The document discusses using an automated dynamic cone penetrometer (ADCP) to characterize subgrade soil resilient modulus (MR) through correlation with ADCP index (DCPI). Twelve subgrade sections with varying soil types were tested with ADCP and falling weight deflectometer before and after pavement construction. Undisturbed soil samples were also extracted and tested in the laboratory for MR. Regression models were developed to correlate MR with DCPI for fine-grained and coarse-grained soils, accounting for other physical properties. Results suggest ADCP can reliably estimate MR and detect changes in subgrade stiffness from pavement loading.
Structural evaluation of low volume road pavements using pavement dynamic con...eSAT Journals
Abstract
Static and dynamic cone penetration tests are widely used in Foundation engineering for measuring the penetration resistance of the
ground and for relating it to the degree of compaction and safe bearing capacity of soils. In Highway Engineering, Pavement
Dynamic Cone Penetrometer (DCP) is used for rapid in-situ strength evaluation of subgrade and other unbound pavement layers. In
the present studies, an attempt has been made to identify the strength and thickness of different pavement layers of newly constructed
low volume roads in the State of Karnataka, India using dynamic cone penetration studies and was compared with actual
measurements at the site. The evaluation of pavement test stretches was made for a period of two years, and changes in penetration
resistance of different pavement layers were measured. A Software was used to analyze the DCP data and to correlate with field
observation. The results have favoured the possibility of using dynamic cone penetrometer as a quality control and pavement
monitoring tool for low volume roads, eliminating the need for a Benkelman beam or a falling weight deflectometer.
Keywords: Pavement Dynamic Cone Penetrometer, CBR, Subgrade, Rural roads
Structural evaluation of low volume road pavements using pavement dynamic con...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Triaxial test on soil important insights -formatted paperSamirsinh Parmar
This document discusses triaxial testing of soils under stress-controlled and strain-controlled loading modes. It provides a brief history of triaxial testing and describes key aspects of the test including the apparatus, sample preparation, procedures, and analysis of results. It explains that triaxial tests are useful for determining soil shear strength parameters and simulating three-dimensional stress conditions in the field. The document also summarizes important insights from previous studies comparing results of stress-controlled and strain-controlled triaxial tests.
Seismic performance of a layered liquefiable site validation of numerical sim...Mahir Badanagki, Ph.D.
In this paper, the results of a centrifuge experiment modeling of a layered soil profile, including a liquefiable layer of Ottawa sand, are used to evaluate the predictive capabilities of two state ofthe-art constitutive models.
The document presents the results of an experimental study on the variation of shear strength of layered soils. Unconsolidated undrained triaxial tests were performed on soil samples compacted in two and three layers of different combinations of black cotton soil 1 (BC1), black cotton soil 2 (BC2), and red soil (R). It was found that adding a layer of coarser red soil between layers of finer BC1 and BC2 soils led to an increase in the angle of internal friction and a decrease in cohesion. The maximum shear strength of 0.81 kg/cm2 was obtained for a three layer system of BC2-BC1-BC1, while the minimum of 0.43 kg/cm2 was
Analytical study on soil pile interaction effect in the variation of natural ...IAEME Publication
This document summarizes an analytical study on how the natural frequency of a single pile foundation varies with soil-pile interaction effects. It presents the theoretical formulation for calculating the depth of fixity and natural frequency of a pile based on the soil modulus and pile diameter. A finite difference method and MATLAB code were used to model the soil-pile system and conduct a parametric study. The results show that the natural frequency non-linearly decreases with lower soil modulus and smaller pile diameter. An equation was developed through regression analysis to predict the natural frequency based on the soil and pile properties. Understanding how natural frequency varies with soil-pile interaction is important for designing foundations subjected to dynamic loads.
Baghdad subgrade resilient modulus and liquefaction evaluation for pavement d...Alexander Decker
This document discusses a study evaluating the resilient modulus and liquefaction potential of soils in Baghdad, Iraq. The study uses cyclic triaxial tests to directly measure resilient modulus according to AASHTO standards. It also develops a neural network model to predict resilient modulus using basic soil properties. The study finds that Baghdad soils have resilient modulus values ranging from 40-100 MPa but would be classified as fair to poor subgrades. It also indicates the soils showed little potential for liquefaction under cyclic loading conditions. The document provides background on resilient modulus testing standards and factors that influence resilient modulus values.
The Experimental Failure behaviour of a Prestressed Concrete Electricity Tran...Samirsinh Parmar
Pre-stressed Concrete poles, Full-scale field test, Design wind load, Soil–structure-interaction, foundation soil analysis, Mono-pole Behavior with respect to lateral load, effect of foundation soil
Structural evaluation of low volume road pavements using pavement dynamic con...eSAT Journals
Abstract
Static and dynamic cone penetration tests are widely used in Foundation engineering for measuring the penetration resistance of the
ground and for relating it to the degree of compaction and safe bearing capacity of soils. In Highway Engineering, Pavement
Dynamic Cone Penetrometer (DCP) is used for rapid in-situ strength evaluation of subgrade and other unbound pavement layers. In
the present studies, an attempt has been made to identify the strength and thickness of different pavement layers of newly constructed
low volume roads in the State of Karnataka, India using dynamic cone penetration studies and was compared with actual
measurements at the site. The evaluation of pavement test stretches was made for a period of two years, and changes in penetration
resistance of different pavement layers were measured. A Software was used to analyze the DCP data and to correlate with field
observation. The results have favoured the possibility of using dynamic cone penetrometer as a quality control and pavement
monitoring tool for low volume roads, eliminating the need for a Benkelman beam or a falling weight deflectometer.
Keywords: Pavement Dynamic Cone Penetrometer, CBR, Subgrade, Rural roads
Structural evaluation of low volume road pavements using pavement dynamic con...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Triaxial test on soil important insights -formatted paperSamirsinh Parmar
This document discusses triaxial testing of soils under stress-controlled and strain-controlled loading modes. It provides a brief history of triaxial testing and describes key aspects of the test including the apparatus, sample preparation, procedures, and analysis of results. It explains that triaxial tests are useful for determining soil shear strength parameters and simulating three-dimensional stress conditions in the field. The document also summarizes important insights from previous studies comparing results of stress-controlled and strain-controlled triaxial tests.
Seismic performance of a layered liquefiable site validation of numerical sim...Mahir Badanagki, Ph.D.
In this paper, the results of a centrifuge experiment modeling of a layered soil profile, including a liquefiable layer of Ottawa sand, are used to evaluate the predictive capabilities of two state ofthe-art constitutive models.
The document presents the results of an experimental study on the variation of shear strength of layered soils. Unconsolidated undrained triaxial tests were performed on soil samples compacted in two and three layers of different combinations of black cotton soil 1 (BC1), black cotton soil 2 (BC2), and red soil (R). It was found that adding a layer of coarser red soil between layers of finer BC1 and BC2 soils led to an increase in the angle of internal friction and a decrease in cohesion. The maximum shear strength of 0.81 kg/cm2 was obtained for a three layer system of BC2-BC1-BC1, while the minimum of 0.43 kg/cm2 was
Analytical study on soil pile interaction effect in the variation of natural ...IAEME Publication
This document summarizes an analytical study on how the natural frequency of a single pile foundation varies with soil-pile interaction effects. It presents the theoretical formulation for calculating the depth of fixity and natural frequency of a pile based on the soil modulus and pile diameter. A finite difference method and MATLAB code were used to model the soil-pile system and conduct a parametric study. The results show that the natural frequency non-linearly decreases with lower soil modulus and smaller pile diameter. An equation was developed through regression analysis to predict the natural frequency based on the soil and pile properties. Understanding how natural frequency varies with soil-pile interaction is important for designing foundations subjected to dynamic loads.
Baghdad subgrade resilient modulus and liquefaction evaluation for pavement d...Alexander Decker
This document discusses a study evaluating the resilient modulus and liquefaction potential of soils in Baghdad, Iraq. The study uses cyclic triaxial tests to directly measure resilient modulus according to AASHTO standards. It also develops a neural network model to predict resilient modulus using basic soil properties. The study finds that Baghdad soils have resilient modulus values ranging from 40-100 MPa but would be classified as fair to poor subgrades. It also indicates the soils showed little potential for liquefaction under cyclic loading conditions. The document provides background on resilient modulus testing standards and factors that influence resilient modulus values.
The Experimental Failure behaviour of a Prestressed Concrete Electricity Tran...Samirsinh Parmar
Pre-stressed Concrete poles, Full-scale field test, Design wind load, Soil–structure-interaction, foundation soil analysis, Mono-pole Behavior with respect to lateral load, effect of foundation soil
SPT, SCPT, and DCPT Correlation for SC, CL, and SM-SC Soils: A Case Study of ...Samirsinh Parmar
SPT, SCPT, and DCPT Correlation for SC, CL, and SM-SC Soils: A Case Study of Nadiad Soil,Standard Penetration Test, Dynamic Cone Penetration Test, Static Cone Penetration Test, Sand, Silt, Correlation
Improving the performance of asphalt mixtures using nano silicaAhmedMSawan
Adding 7% nano silica by weight of asphalt improves the performance of asphalt mixtures. At the optimum asphalt content, 7% nano silica increases Marshall stability by 25% and decreases Marshall flow by 19%, while maintaining similar unit weight and air void properties. It also increases direct compression strength by 7% and indirect tensile strength by 2.7%, while decreasing wheel tracking rut depth by 40%. Overall, nano silica is effective at enhancing the characteristics of asphalt mixtures.
Study on Consolidation and Correlation with Index Properties Of Different Soi...IJERD Editor
The document discusses a study on correlating the coefficient of consolidation (cv) of different soils in Manipur Valley with their index properties. One-dimensional consolidation tests were conducted on five undisturbed soil samples collected from different locations. The cv was determined and found to correlate best with the liquid limit. Specifically:
1) Consolidation tests were conducted and cv values ranging from 1.02x10^-8 to 6.27x10^-9 m^2/sec were obtained.
2) cv was found to increase with effective vertical pressure up to 40kPa and then remain similar for higher pressures.
3) cv showed better correlation with the liquid limit than other index properties like plasticity index
Fixity depth of offshore piles in elastoplastic soft clay under dynamic loadeSAT Journals
Abstract
This work represents study of dynamic behavior of offshore piles embedded in elastoplastic soft clay, and estimating the fixity depth of pile. ABAQUS finite element program which used to simulate the problem. The soil was modeled in two case elastic state model and elastoplastic state model represented by cam-clay model, three dimension element used to represent the interaction between pile and soil, and laboratory tests used to getting the real properties of clayey soil and to descried interface. The results obtained developed two empirical equations used to calculate depth of pile fixity for pile embedded in elastic and elastoplastic soil respectively. Also, show the depth of pile fixity is increase about (40 %) due to change soil model from elastic to plastic, when pile embedded in elastoplastic soil its dependent on soil strength, interface properties and pile rigidity. The pile head displacement is increase about 90 % while the bending moment is decease 10 % at pile head.
ABAQUS simulation for consolidation of saturated soft soil in two-dimensional...IJRES Journal
1) The document simulates the consolidation of saturated soft soil in a two-dimensional finite region under shear or normal loads using ABAQUS software.
2) The results show that the final soil settlement is unaffected by boundary permeability but depends on the load and soil properties. Different boundary conditions lead to variable consolidation processes.
3) Shear loads have a greater influence on horizontal displacement, while normal loads more strongly impact vertical displacement, with orders of magnitude differences between the two load types.
This study used finite element modeling to analyze swelling behavior in a tunnel excavated through marl rock. Laboratory tests on marl rock samples were used to calibrate two finite element programs, FISS and Nisa-II. FISS modeled the tunnel using the laboratory swelling test results. Nisa-II modeled time-dependent creep behavior by defining a creep function relating stress, strain, and time. Both programs analyzed stresses around the tunnel and indicated higher stresses in the sidewalls compared to the roof and floor. The study demonstrated a method to numerically model swelling behavior in tunnels using laboratory test data.
Design Considerations for AASHTO Flexible pavement designImran Nawaz
The document discusses the key factors considered in AASHTO flexible pavement design: pavement performance, traffic, roadbed soils, materials of construction, environment, drainage, and reliability. Pavement performance is measured by present serviceability index (PSI) on a scale of 0 to 5. Traffic is considered in terms of estimated single axle loads (ESALs). Roadbed soils are characterized by properties like CBR, R-value, and resilient modulus (Mr). Materials are assigned structural numbers (SN) based on properties. Drainage and environment affect Mr. Reliability ensures the design survives the design life with a given level of probability. The design process involves determining layer SNs from properties then thickness to achieve a
Designing and construction of piles under various field conditions Dr. Naveen BP
1) The document discusses the design and construction of piles under various field conditions at two sites in Bangalore.
2) At the first residential site, pile foundations were used due to a high water table and surrounding buildings. The safe load capacity of the piles was analyzed using different analytical methods and compared to load test results.
3) At the second commercial site with excavations, laterally loaded piles were installed to protect excavation sides. Closed form and numerical analyses using PLAXIS were used to design the sheet piles and compared.
This document summarizes a study that analyzed the performance of vertical skirted strip footings on slopes using the finite element software PLAXIS 2D. Various parameters were considered, including the vertical load, depth of footing embedment, distance of footing from crest, ratio of skirt depth to footing width, and configuration of the skirt (one side, both sides, unequal sides). The results showed that skirted foundations significantly improved the bearing capacity compared to unskirted foundations. Bearing capacity increased with deeper skirt depths. Footings at the crest also showed improved bearing capacity. Footing embedment depth did not affect bearing capacity. The study provides insights into using skirted foundations to improve slope stability and bearing capacity
Numerical Simulations on Triaxial Strength of Silty Sand in Drained Conditionsijceronline
The document presents the results of numerical simulations examining the drained response of silty sand under triaxial loading conditions using a hypoplastic constitutive model. The model is validated against experimental data from oedometric compression tests on loose and dense silty sand. Parametric studies are conducted to analyze the influence of void ratio/relative density and consolidation pressure on stress-strain behavior, stress paths, and volume change response. Results show that the drained response (contractive or dilative) depends on the combined effects of density and consolidation pressure, with looser soils at lower pressures exhibiting more dilation. Peak stresses are observed at lower densities and pressures.
Numerical simulation of laterally loaded pileDr. Naveen BP
This document presents a finite element model simulation of a lateral load test on a 1m diameter bored pile embedded in residual soils. The pile and soil were modeled in PLAXIS 2D, with the soil represented by a Mohr-Coulomb model and the pile as a beam element. The model results showed good agreement with load-displacement curves from the field test. However, the field test was unable to apply loads high enough to reach design code displacement limits due to limitations of test equipment for large piles in residual soils. The numerical model can simulate larger displacements to evaluate pile behavior under higher loads.
Experimental Study to Correlate the Test Results of PBT, UCS, and CBR with Li...CSCJournals
This document presents an experimental study that correlates test results from the plate bearing test (PBT), unconfined compressive strength (UCS) test, and California bearing ratio (CBR) test with results from the dynamic cone penetrometer (DCP) test on various soils under soaked conditions. Soil samples from different locations in Gujarat, India were tested for liquid limit, plastic limit, CBR, PBT, UCS, and DCP at their maximum dry densities achieved through modified proctor compaction in a soaked state. Empirical correlations between the test results were established using linear regression to develop formulations that can be used to estimate time-consuming strength parameters from rapid DCP tests.
This document discusses a finite element analysis that was performed to evaluate the responses of asphalt pavement mixtures modified with different additives. A 2D model was created using PLAXIS software to simulate pavement structures consisting of an asphalt layer modified with nano silica, silica fume, lime, rubber or polymer over an aggregate base and subgrade. Laboratory testing was conducted to determine modulus and Poisson's ratio of the modified mixtures. The model analyzed vertical displacement and stresses under traffic loads and found that mixtures modified with silica fume exhibited the least deformation and stresses.
IRJET- Experimental Study of various Shaped Isolated Footings under Monotonic...IRJET Journal
1) The study experimentally compares the load-settlement behavior of six different shaped isolated footings (square, rectangular, circular, hexagonal, triangular, and octagonal) under monotonic and incremental cyclic loading on black cotton soil.
2) Testing found that under both monotonic and cyclic loading, square footings experienced the least settlement at a given load intensity, while triangular footings experienced the maximum settlement.
3) Elastic rebound curves were also plotted and compared, showing that square footings exhibited better rebound performance compared to other shapes like triangular footings.
This document summarizes the analysis of petrophysical data from two wells in the Upper Spraberry Formation to develop a rock-fluid model. Six distinct rock types were identified based on unique pore geometry, mineral composition, and fluid flow characteristics. Laboratory analysis of core plugs using nitrogen, helium, and mercury injection characterized porosity, permeability, pore size distribution, and wettability of each rock type. Clean sandy rocks generally had higher porosity and permeability than shaly or dolostone units. Integration of petrophysical data with log responses and core descriptions allowed differentiation of reservoir-quality from lower-quality rock intervals in the formation.
This document summarizes a study on establishing logging interpretation models for reservoir parameters like porosity, permeability, oil saturation, and gas saturation in the Gaotaizi Reservoir of the L Oilfield. Models were developed using core data from 4 wells and include:
1) A porosity model relating acoustic travel time to porosity with an error of 0.92%
2) A permeability model relating permeability to porosity with an error of 0.31%
3) An oil saturation model using resistivity data with empirically determined parameters
4) A method to determine original gas saturation from mercury injection data.
Application of the models improved interpretation precision and allowed recalculation of oil and gas reserves for the
1. The document discusses applying multi-curve reconstruction technology to seismic inversion to improve accuracy and reliability. It focuses on reconstructing SP and RMN curves from well logs that are affected by various distortions.
2. The process of reconstructing the curves involves removing baseline drift, standardizing values, applying linear filtering, and fitting the curves. This removes interference and retains valid lithological information.
3. Reconstructing high quality curves improves the resolution and credibility of seismic inversion results. The method is shown to effectively predict sand distribution with little error.
"A full experimental and numerical modelling of the practicability of thin fo...Mehran Naghizadeh
Paper entitled "A full experimental and numerical modelling of the practicability of thin foam barrier as vibration reduction measure" published by Soil Dynamics and Earthquake Engineering (2020).
Predicting Resilient Modulus of Clayey Subgrade Soils by Means of Cone Penetr...Pouyan Fakharian
Resilient modulus (Mr) of subgrade soils is considered as one of the most important factors for designing flexible pavements using empirical methods as well as mechanistic-empirical methods. The resilient modulus is commonly measured by a dynamic triaxial loading test, which is complex and expensive. In this research, back-propagation artificial neural network method has been employed to model the resilient modulus of clayey subgrade soils based on the results of the cone penetration test. The prediction of the resilient modulus of clayey subgrade soil can be possible through the developed neural network based on the parameters of the cone tip resistance (qc), sleeve friction (fs), moisture content (w), and dry density (γd). The results of the present study show that the coefficients of determination (R2) for training and testing sets are 0.9837 and 0.9757, respectively. According to the sensitivity analysis results, the moisture content is the least important parameter to predict the resilient modulus of clayey subgrade soils, while the importance of other parameters is almost the same. In this study, the effect of different parameters on the resilient modulus of clayey subgrade soil was evaluated using parametric analysis and it was found that with increasing the cone tip resistance (qc), the sleeve friction (fs) and the dry density (γd) and also with decreasing the moisture content (w) of soils, the resilient modulus of clayey subgrade soils increases.
The document presents the results of a study that used linear regression to correlate index properties and California bearing ratio (CBR) values of lateritic soil samples collected from eight borrow pits in Osogbo, Nigeria. Laboratory tests on the samples found good correlations between CBR and properties like grain size, liquid limit, plastic limit, and maximum dry density. Regression equations were developed to estimate CBR values from index properties for preliminary assessments, though actual CBR tests are still needed given the heterogeneous nature of lateritic soils. The CBR values ranged from 64-85% unsoaked and 26-33% soaked. Most samples met specifications for subgrade, sub-base, and base materials, except two had lower soaked CBR
Prediction of tractve performance on soil surface yogesh5158
This seminar discusses approaches to predicting tractive performance of vehicles on soil surfaces. It presents a new approach using soil deformation modulus as a measure of soil strength. The presentation evaluates the new prediction equation against an existing widely used equation from Wismer and Luth. It describes developing expressions for contact length and area of tractor tires in soil. Results show the new equation predicts traction coefficient more accurately than some other methods and validates using soil deformation modulus in traction studies.
SPT, SCPT, and DCPT Correlation for SC, CL, and SM-SC Soils: A Case Study of ...Samirsinh Parmar
SPT, SCPT, and DCPT Correlation for SC, CL, and SM-SC Soils: A Case Study of Nadiad Soil,Standard Penetration Test, Dynamic Cone Penetration Test, Static Cone Penetration Test, Sand, Silt, Correlation
Improving the performance of asphalt mixtures using nano silicaAhmedMSawan
Adding 7% nano silica by weight of asphalt improves the performance of asphalt mixtures. At the optimum asphalt content, 7% nano silica increases Marshall stability by 25% and decreases Marshall flow by 19%, while maintaining similar unit weight and air void properties. It also increases direct compression strength by 7% and indirect tensile strength by 2.7%, while decreasing wheel tracking rut depth by 40%. Overall, nano silica is effective at enhancing the characteristics of asphalt mixtures.
Study on Consolidation and Correlation with Index Properties Of Different Soi...IJERD Editor
The document discusses a study on correlating the coefficient of consolidation (cv) of different soils in Manipur Valley with their index properties. One-dimensional consolidation tests were conducted on five undisturbed soil samples collected from different locations. The cv was determined and found to correlate best with the liquid limit. Specifically:
1) Consolidation tests were conducted and cv values ranging from 1.02x10^-8 to 6.27x10^-9 m^2/sec were obtained.
2) cv was found to increase with effective vertical pressure up to 40kPa and then remain similar for higher pressures.
3) cv showed better correlation with the liquid limit than other index properties like plasticity index
Fixity depth of offshore piles in elastoplastic soft clay under dynamic loadeSAT Journals
Abstract
This work represents study of dynamic behavior of offshore piles embedded in elastoplastic soft clay, and estimating the fixity depth of pile. ABAQUS finite element program which used to simulate the problem. The soil was modeled in two case elastic state model and elastoplastic state model represented by cam-clay model, three dimension element used to represent the interaction between pile and soil, and laboratory tests used to getting the real properties of clayey soil and to descried interface. The results obtained developed two empirical equations used to calculate depth of pile fixity for pile embedded in elastic and elastoplastic soil respectively. Also, show the depth of pile fixity is increase about (40 %) due to change soil model from elastic to plastic, when pile embedded in elastoplastic soil its dependent on soil strength, interface properties and pile rigidity. The pile head displacement is increase about 90 % while the bending moment is decease 10 % at pile head.
ABAQUS simulation for consolidation of saturated soft soil in two-dimensional...IJRES Journal
1) The document simulates the consolidation of saturated soft soil in a two-dimensional finite region under shear or normal loads using ABAQUS software.
2) The results show that the final soil settlement is unaffected by boundary permeability but depends on the load and soil properties. Different boundary conditions lead to variable consolidation processes.
3) Shear loads have a greater influence on horizontal displacement, while normal loads more strongly impact vertical displacement, with orders of magnitude differences between the two load types.
This study used finite element modeling to analyze swelling behavior in a tunnel excavated through marl rock. Laboratory tests on marl rock samples were used to calibrate two finite element programs, FISS and Nisa-II. FISS modeled the tunnel using the laboratory swelling test results. Nisa-II modeled time-dependent creep behavior by defining a creep function relating stress, strain, and time. Both programs analyzed stresses around the tunnel and indicated higher stresses in the sidewalls compared to the roof and floor. The study demonstrated a method to numerically model swelling behavior in tunnels using laboratory test data.
Design Considerations for AASHTO Flexible pavement designImran Nawaz
The document discusses the key factors considered in AASHTO flexible pavement design: pavement performance, traffic, roadbed soils, materials of construction, environment, drainage, and reliability. Pavement performance is measured by present serviceability index (PSI) on a scale of 0 to 5. Traffic is considered in terms of estimated single axle loads (ESALs). Roadbed soils are characterized by properties like CBR, R-value, and resilient modulus (Mr). Materials are assigned structural numbers (SN) based on properties. Drainage and environment affect Mr. Reliability ensures the design survives the design life with a given level of probability. The design process involves determining layer SNs from properties then thickness to achieve a
Designing and construction of piles under various field conditions Dr. Naveen BP
1) The document discusses the design and construction of piles under various field conditions at two sites in Bangalore.
2) At the first residential site, pile foundations were used due to a high water table and surrounding buildings. The safe load capacity of the piles was analyzed using different analytical methods and compared to load test results.
3) At the second commercial site with excavations, laterally loaded piles were installed to protect excavation sides. Closed form and numerical analyses using PLAXIS were used to design the sheet piles and compared.
This document summarizes a study that analyzed the performance of vertical skirted strip footings on slopes using the finite element software PLAXIS 2D. Various parameters were considered, including the vertical load, depth of footing embedment, distance of footing from crest, ratio of skirt depth to footing width, and configuration of the skirt (one side, both sides, unequal sides). The results showed that skirted foundations significantly improved the bearing capacity compared to unskirted foundations. Bearing capacity increased with deeper skirt depths. Footings at the crest also showed improved bearing capacity. Footing embedment depth did not affect bearing capacity. The study provides insights into using skirted foundations to improve slope stability and bearing capacity
Numerical Simulations on Triaxial Strength of Silty Sand in Drained Conditionsijceronline
The document presents the results of numerical simulations examining the drained response of silty sand under triaxial loading conditions using a hypoplastic constitutive model. The model is validated against experimental data from oedometric compression tests on loose and dense silty sand. Parametric studies are conducted to analyze the influence of void ratio/relative density and consolidation pressure on stress-strain behavior, stress paths, and volume change response. Results show that the drained response (contractive or dilative) depends on the combined effects of density and consolidation pressure, with looser soils at lower pressures exhibiting more dilation. Peak stresses are observed at lower densities and pressures.
Numerical simulation of laterally loaded pileDr. Naveen BP
This document presents a finite element model simulation of a lateral load test on a 1m diameter bored pile embedded in residual soils. The pile and soil were modeled in PLAXIS 2D, with the soil represented by a Mohr-Coulomb model and the pile as a beam element. The model results showed good agreement with load-displacement curves from the field test. However, the field test was unable to apply loads high enough to reach design code displacement limits due to limitations of test equipment for large piles in residual soils. The numerical model can simulate larger displacements to evaluate pile behavior under higher loads.
Experimental Study to Correlate the Test Results of PBT, UCS, and CBR with Li...CSCJournals
This document presents an experimental study that correlates test results from the plate bearing test (PBT), unconfined compressive strength (UCS) test, and California bearing ratio (CBR) test with results from the dynamic cone penetrometer (DCP) test on various soils under soaked conditions. Soil samples from different locations in Gujarat, India were tested for liquid limit, plastic limit, CBR, PBT, UCS, and DCP at their maximum dry densities achieved through modified proctor compaction in a soaked state. Empirical correlations between the test results were established using linear regression to develop formulations that can be used to estimate time-consuming strength parameters from rapid DCP tests.
This document discusses a finite element analysis that was performed to evaluate the responses of asphalt pavement mixtures modified with different additives. A 2D model was created using PLAXIS software to simulate pavement structures consisting of an asphalt layer modified with nano silica, silica fume, lime, rubber or polymer over an aggregate base and subgrade. Laboratory testing was conducted to determine modulus and Poisson's ratio of the modified mixtures. The model analyzed vertical displacement and stresses under traffic loads and found that mixtures modified with silica fume exhibited the least deformation and stresses.
IRJET- Experimental Study of various Shaped Isolated Footings under Monotonic...IRJET Journal
1) The study experimentally compares the load-settlement behavior of six different shaped isolated footings (square, rectangular, circular, hexagonal, triangular, and octagonal) under monotonic and incremental cyclic loading on black cotton soil.
2) Testing found that under both monotonic and cyclic loading, square footings experienced the least settlement at a given load intensity, while triangular footings experienced the maximum settlement.
3) Elastic rebound curves were also plotted and compared, showing that square footings exhibited better rebound performance compared to other shapes like triangular footings.
This document summarizes the analysis of petrophysical data from two wells in the Upper Spraberry Formation to develop a rock-fluid model. Six distinct rock types were identified based on unique pore geometry, mineral composition, and fluid flow characteristics. Laboratory analysis of core plugs using nitrogen, helium, and mercury injection characterized porosity, permeability, pore size distribution, and wettability of each rock type. Clean sandy rocks generally had higher porosity and permeability than shaly or dolostone units. Integration of petrophysical data with log responses and core descriptions allowed differentiation of reservoir-quality from lower-quality rock intervals in the formation.
This document summarizes a study on establishing logging interpretation models for reservoir parameters like porosity, permeability, oil saturation, and gas saturation in the Gaotaizi Reservoir of the L Oilfield. Models were developed using core data from 4 wells and include:
1) A porosity model relating acoustic travel time to porosity with an error of 0.92%
2) A permeability model relating permeability to porosity with an error of 0.31%
3) An oil saturation model using resistivity data with empirically determined parameters
4) A method to determine original gas saturation from mercury injection data.
Application of the models improved interpretation precision and allowed recalculation of oil and gas reserves for the
1. The document discusses applying multi-curve reconstruction technology to seismic inversion to improve accuracy and reliability. It focuses on reconstructing SP and RMN curves from well logs that are affected by various distortions.
2. The process of reconstructing the curves involves removing baseline drift, standardizing values, applying linear filtering, and fitting the curves. This removes interference and retains valid lithological information.
3. Reconstructing high quality curves improves the resolution and credibility of seismic inversion results. The method is shown to effectively predict sand distribution with little error.
"A full experimental and numerical modelling of the practicability of thin fo...Mehran Naghizadeh
Paper entitled "A full experimental and numerical modelling of the practicability of thin foam barrier as vibration reduction measure" published by Soil Dynamics and Earthquake Engineering (2020).
Predicting Resilient Modulus of Clayey Subgrade Soils by Means of Cone Penetr...Pouyan Fakharian
Resilient modulus (Mr) of subgrade soils is considered as one of the most important factors for designing flexible pavements using empirical methods as well as mechanistic-empirical methods. The resilient modulus is commonly measured by a dynamic triaxial loading test, which is complex and expensive. In this research, back-propagation artificial neural network method has been employed to model the resilient modulus of clayey subgrade soils based on the results of the cone penetration test. The prediction of the resilient modulus of clayey subgrade soil can be possible through the developed neural network based on the parameters of the cone tip resistance (qc), sleeve friction (fs), moisture content (w), and dry density (γd). The results of the present study show that the coefficients of determination (R2) for training and testing sets are 0.9837 and 0.9757, respectively. According to the sensitivity analysis results, the moisture content is the least important parameter to predict the resilient modulus of clayey subgrade soils, while the importance of other parameters is almost the same. In this study, the effect of different parameters on the resilient modulus of clayey subgrade soil was evaluated using parametric analysis and it was found that with increasing the cone tip resistance (qc), the sleeve friction (fs) and the dry density (γd) and also with decreasing the moisture content (w) of soils, the resilient modulus of clayey subgrade soils increases.
The document presents the results of a study that used linear regression to correlate index properties and California bearing ratio (CBR) values of lateritic soil samples collected from eight borrow pits in Osogbo, Nigeria. Laboratory tests on the samples found good correlations between CBR and properties like grain size, liquid limit, plastic limit, and maximum dry density. Regression equations were developed to estimate CBR values from index properties for preliminary assessments, though actual CBR tests are still needed given the heterogeneous nature of lateritic soils. The CBR values ranged from 64-85% unsoaked and 26-33% soaked. Most samples met specifications for subgrade, sub-base, and base materials, except two had lower soaked CBR
Prediction of tractve performance on soil surface yogesh5158
This seminar discusses approaches to predicting tractive performance of vehicles on soil surfaces. It presents a new approach using soil deformation modulus as a measure of soil strength. The presentation evaluates the new prediction equation against an existing widely used equation from Wismer and Luth. It describes developing expressions for contact length and area of tractor tires in soil. Results show the new equation predicts traction coefficient more accurately than some other methods and validates using soil deformation modulus in traction studies.
Modeling Soil Pressure-Sinkage Characteristic as Affected by Sinkage rate usi...J. Agricultural Machinery
Due to the numerous variables that may influence the soil-machine interaction systems, predicting the mechanical response of soil interacting with off-road traction equipment is challenging. In this study, deep neural networks (DNNs) are chosen as a potential solution for explaining the varying soil sinkage rates because of their ability to model complex, multivariate, and dynamic systems. Plate sinkage tests were carried out using a Bevameter in a fixed-type soil bin with a 24 m length, 2 m width, and 1 m depth. Experimental tests were conducted at three sinkage rates for two plate sizes, with a soil water content of 10%. The provided empirical data on the soil pressure-sinkage relationship served as the basis for an algorithm capable of discerning the soil-machine interaction. From the iterative process, it was determined that a DNN, specifically a feed-forward back-propagation DNN with three hidden layers, is the optimal choice. The optimized DNN architecture is structured as 3-8-15-10-1, as determined by the Grey Wolf Optimization algorithm. While the Bekker equation had traditionally been employed as a widely accepted method for predicting soil pressure-sinkage behavior, it typically disregarded the influence of sinkage velocity of the soil. However, the findings revealed the significant impact of sinkage velocity on the parameters governing the soil deformation response. The trained DNN successfully incorporated the sinkage velocity into its structure and provided accurate results with an MSE value of 0.0871.
Evaluating 2D numerical simulations of granular columns in level and gently s...Mahir Badanagki, Ph.D.
The response of a layered liquefiable soil profile, with granular columns as a mitigation strategy, was evaluated via numerical and centrifuge modeling. Comparisons were made for a level site containing a single granular column and for a pair of gentle slopes, one of which was mitigated with a network of dense granular columns. The results reveal the abilities and limitations of two state-of-the-art soil constitutive models. All simulations were performed in 2-dimensions using: 1) the pressure-dependent, multi-yield-surface, plasticity-based soil constitutive model (PDMY02); and 2) the bounding surface, plasticity-based, Manzari-Dafalias (M-D) soil constitutive model, both implemented in OpenSees. Numerical model parameters were previously calibrated via element testing. Both constitutive models under-predicted PGA near the surface at different distances from the granular column, but they better predicted spectral accelerations at periods exceeding 0.5 s (particularly M-D). The M-D model generally predicted seismic settlements well, while PDMY02 notably underestimated soil's volumetric compressibility and strains. Both models accurately predicted the peak value and generation of excess pore pressures during shaking for the unmitigated slope, leading to a successful prediction of lateral deformations. However, lateral movement of the treated slope was poorly predicted by both models due to inaccuracies in predicting the dissipation rate in the presence of drains. Both models came close to predicting the performance of gently sloping, liquefiable sites when untreated. But further advances are required to better predict the rate of excess pore pressure dissipation and seismic performance when the slope is treated with granular columns.
To Experimental Study of Comparison and Development of Design for Rigid Pavem...Agriculture Journal IJOEAR
Abstract— The development of design have been discussed adopted various types methods use. The Hadi and Arfiadi Method presents a formulation for the optimum rigid road pavement design by genetic algorithm, a new method. The Westergaard’s Method determines the stresses in the rigid concrete slab and also the pressure-deformation curve which depend upon the relative stiffness of the slab and the subgrade. Razouki and Al-Muhana also developed stress charts similar to Westergaard’s method. The paper reveals that the effects on the maximum bending tensile stress are quite significant due to the modulus of subgrade reaction, modulus of elasticity of concrete and slab The Maharaj and Gill method have performed axisymmetric finite element analysis by varying parameters, the thickness of pavement, pressure and elastic modulus of subgrade. The advantage of this method is that four types of design charts have been presented which other methods have note done. First type of design chart has been plotted between thickness of pavement and nodal deflections for various pressures for a particular elastic modulus of soil. Second type of design chart has been plotted between thickness of pavement and element stress for various pressures for a particular elastic modulus of soil. The third type of design chart has been plotted between thickness of pavement and nodal deflections for various elastic moduli of subgrade for a particular pressure. Each of the design charts has three parameters. For two known parameters, the third parameter can be obtained.
Prediction of uplift capacity using genetic programmingAhmed Ebid
DOI: 10.13140/2.1.3107.6163
In most geotechnical problems, it is too difficult to predict soil and structural behavior accurately, because of the large variation in soil parameters and the assumptions of numerical solutions. But recently many geotechnical problems are solved using Artificial Intelligence (AI) techniques, by presenting new solutions or developing existing ones. Genetic Programming, (GP), is one of the most recently developed (AI) techniques based on Genetic Algorithm (GA) technique. In this research, GP technique is utilized to develop prediction criteria for uplift capacity of shallow foundations using collected historical records. The uplift capacity formula is developed using special software written by the authors in "Visual C++" language. The accuracy of the developed formula was also compared with earlier prediction methods.
Fixity depth of offshore piles in elastoplastic soft clay under dynamic loadeSAT Journals
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This work represents study of dynamic behavior of offshore piles embedded in elastoplastic soft clay, and estimating the fixity depth of pile. ABAQUS finite element program which used to simulate the problem. The soil was modeled in two case elastic state model and elastoplastic state model represented by cam-clay model, three dimension element used to represent the interaction between pile and soil, and laboratory tests used to getting the real properties of clayey soil and to descried interface. The results obtained developed two empirical equations used to calculate depth of pile fixity for pile embedded in elastic and elastoplastic soil respectively. Also, show the depth of pile fixity is increase about (40 %) due to change soil model from elastic to plastic, when pile embedded in elastoplastic soil its dependent on soil strength, interface properties and pile rigidity. The pile head displacement is increase about 90 % while the bending moment is decease 10 % at pile head.
This document discusses the fatigue behavior of high volume fly ash concrete (HVFAC) under constant amplitude and compound loading. It presents test results of 95 HVFAC and 100 conventional concrete prism specimens tested under constant amplitude flexural fatigue loading. It also discusses test results of 24 HVFAC specimens under compound fatigue loading to verify the validity of Miner's hypothesis for HVFAC. Probability distributions were developed from the fatigue life test results and S-N curves were established relating stress level to fatigue life for both concretes. The findings provide useful data on fatigue performance of HVFAC.
Contribution to long term performance of piled raft foundation in clayey soilIAEME Publication
This document summarizes previous research on piled raft foundations in clayey soils. It discusses how numerical modeling using finite element methods has been used to analyze load distribution, settlement behavior over time, and the effects of different pile configurations. The document reviews several studies that have developed finite element and boundary element models to simulate the behavior of piled raft foundations, soil-structure interaction, and time-dependent consolidation settlement. It also discusses how pile raft foundations can reduce settlement and differential settlement more cost effectively than pile groups or rafts alone.
Experimental estimate of ultimate bearing capacity and settlement for rectangIAEME Publication
The document summarizes experimental tests conducted to estimate the ultimate bearing capacity and settlement of rectangular footings on sand. Laboratory model tests were performed on footings with varying sizes (100mm x 125mm, 100mm x 150mm, etc.) and a constant depth of sand cushion below the footing of 900mm. The tests measured how loading intensity affected settlement. Log-load vs log-settlement curves were plotted from the results, and the point of intersection was used to determine ultimate bearing capacity and corresponding settlement. Bearing capacity factors were computed and compared to theoretical values. The tests found that as footing size increased, ultimate bearing capacity and settlement values also increased, while the bearing capacity factor decreased.
This document discusses applying the NCHRP-1-28 resilient modulus model to characterize blended unbound granular materials in Sudan. An experimental testing program measured the resilient modulus of blended samples using dynamic triaxial tests. The NCHRP-1-28 model was used to predict resilient modulus values, which showed good agreement with measured values, being 8-10% lower, providing conservative estimates. The materials tested included natural gravels blended with sand and crushed stone to meet gradation specifications for base materials. Measured properties like density, CBR and gradation are reported for the blended samples.
Theoretical study for r.c. columns strengthened with gfrp with different main...Ahmed Ebid
DOI: 10.13140/2.1.3631.9041
It becomes a common practice to strength and repair reinforced concrete columns by wrapping them with GFRP sheets. The aim of this research is to develop a formula to describe the relation between the gain of strength of reinforced concrete square columns, their longitudinal reinforcement and number of warped layers of GFRP sheets. The research is based on simulating loading tests of a set of 12 reinforced concrete columns with different reinforcement ratios and different number of warped layers of GFRP sheets using ANSYS software. The outputs of the ANSYS models are verified using experimental tests results carried out by the author in earlier research. The results of the study are used to develop a proposed formula to correlate the axial capacity of the warped square RC column with its reinforcement ratio and the confining stress caused by the sheets. Values from both proposed formula design and formula of Egyptian Code of Practice (ECP) are compared with ANSYS outputs and experimental results. The final conclusion is that gained strength due to confining equals to (confining stress / Fcu)
This document discusses a study on the influence of adding waste polypropylene fibers on the resilient modulus of clay soil. Several tests were conducted including specific gravity, liquid limit, grain size distribution, standard proctor, and cyclic CBR tests on soil samples with different percentages of polypropylene fibers added by weight. The results showed that the resilient modulus increased with the addition of fibers up to an optimum of 0.4% fibers by weight, above which the resilient modulus started to decrease. It was concluded that reinforcing clay soil with polypropylene fibers has a positive influence on improving the resilient modulus of the soil.
This document summarizes a study on using recycled concrete aggregate in concrete. It discusses that recycled aggregate can reduce environmental impacts from construction waste and lower costs. The study tested the compressive strength, split tensile strength, and flexural strength of concrete with 20%, 40%, and 60% replacement of natural coarse aggregate with recycled aggregate. The 40% replacement mix achieved the highest strengths. The study concluded that recycled aggregate concrete can meet design requirements and is a sustainable construction material option.
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This document presents a study that developed empirical equations to predict the soaked CBR value of lean clay soils based on index properties, dry density, and unsoaked CBR values. Laboratory tests were conducted on soil samples collected from an existing flexible pavement, which identified the soil as lean clay. Soaked and unsoaked CBR tests were performed at different densities. Three equations were formulated: 1) Using index properties and compaction characteristics to predict soaked CBR, 2) Relating dry density to soaked CBR, and 3) Relating unsoaked CBR to soaked CBR over a range of dry densities. These equations can be used to predict soaked CBR for lean clay subgrade soils.
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solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
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train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
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1. 70 s Transportation Research Record 1806
Paper No. 02- 2039
Subgrade soil characterization, expressed as resilient modulus (MR),
is crucial for pavement design. For a new design, MR is generally ob-
tained by conducting repeated triaxial tests on reconstituted and un-
disturbed cylindrical specimens. Because of the test’s complexities, in
situ tests are desirable, if reliable correlation is established. This study
investigated the viability of using the automated dynamic cone pen-
etrometer (ADCP, abbreviated as DCP) for subgrade characterization
through correlation between DCP index (penetration per blow) and
MR. The sensitivity of DCP results to changes in subgrade stiffness,
expressed in modulus values, was also investigated. Twelve as-built
subgrade sections, reflecting a range of typical Mississippi subgrade
materials, were selected and tested with DCP. Undisturbed samples
were extracted with a Shelby tube and tested in a repeated triaxial
machine for MR. After other soil physical properties were determined,
the soil was classified according to AASHTO procedure. DCP tests
were repeated atop the subgrade through drilled holes after construc-
tion of pavement layers. Falling weight deflectometer (FWD) testing
was conducted near the DCP test locations. Results suggest two rela-
tionships, for fine-grain and for coarse-grain soils, in correlating the
DCP index to laboratory MR. Other physical properties helped improve
the robustness of the regression models. For model verification, the DCP
and MR tests were repeated and produced good agreement between pre-
dicted and actual MR values. The DCP index before and after pavement
layer’s emplacement suggests subgrade stiffness enhancement, owing
to pavement overburden, which agrees with FWD–backcalculated
moduli.
In the original AASHTO Guide for Design of Pavement Structures,
published in 1961 and revised in 1972, the subgrade stiffness was
accounted for by assigning a soil support value (SSV) on a scale
ranging from 1 to 10. In 1986, the AASHTO guide was substantially
revised to include replacement of SSV with subgrade resilient mod-
ulus (MR ) (1). MR values may be estimated directly from labora-
tory testing, indirectly through correlation with other laboratory and
field tests, or backcalculated from deflection measurements.
For a new design, MR values are generally obtained by con-
ducting repeated triaxial tests on reconstituted and undisturbed
cylindrical specimens. The laboratory test is a tedious, costly, and
time-consuming procedure. Large numbers of samples need to be
collected and tested for reasonably accurate results. Even then, it is
difficult to reproduce the in situ sample conditions (2). Considering
the complexity of the repeated load triaxial test, field testing proce-
dures have been proposed to estimate subgrade moduli. Of particu-
lar interest in this paper is an automated version of the dynamic cone
penetrometer (DCP) as a potential device for estimating MR through
correlation.
The DCP consists of a steel rod with a cone at one end that is
driven into the subgrade by means of a sliding hammer. The material’s
resistance to penetration is measured in terms of the DCP index
(DCPI) in millimeters/blow (3). Figure 1 shows the fully portable
trailer-mounted automated DCP during operation in the field. The
DCP was originally designed and used to determine the strength
profile of the subgrade because of its ability to provide a continuous
record of relative soil strength with depth. Numerous studies have been
conducted investigating the use of the DCP and factors affecting its
results (4–8).
The direct use of the DCP in pavement design is yet to be estab-
lished. However, it has been correlated to commonly used soil
parameters, for example, California bearing ratio (CBR) (5). Burn-
ham and Johnson (9) stated that the DCP could be used to provide
a reasonable estimate of unconfined compressive strength of soil-
lime mixtures. The shear strength of soils was correlated with the
DCPI, for different confining pressures, in a laboratory study con-
ducted by Ayers et al. (7 ). Employing a DCPI–CBR relation fol-
lowed by another one between the CBR and MR, the DCP results were
converted to the MR, which showed good agreement with both
laboratory-measured and falling weight deflectometer (FWD)–
backcalculated values (8).
Only a few studies attempted to directly correlate the MR to DCPI.
Hassan (4) developed a simple regression model correlating the
MR with DCPI for fine-grain soils at optimum moisture content.
Chai and Roslie (10 ) used the results of DCP tests and CBR–DCP
relationships developed in Malaysia during the 1987 National Axle
Load Study to determine in situ subgrade elastic modulus. Jianzhou
et al. (11) analyzed the FWD deflection data and DCP results of
six pavement projects in Kansas to develop a relationship be-
tween the DCPI and backcalculated subgrade moduli. Adopting the
one-dimensional projectile penetration, originally developed by
Yankelevsky and Adin (12), Chua (13) related the DCP test results to
elastic moduli of subgrade soil.
The objective of this paper is to explore the feasibility of using
the DCP to characterize subgrade soil MR, via correlating the DCPI
to laboratory resilient modulus. For two different soil groups,
namely, fine-grain and coarse-grain soils, two different regression
models are attempted correlating the MR (as dependent variable)
with the DCPI and other soil physical state variables as independent
variables. Influence of pavement overburden on subgrade stiffness
(moduli), and in turn on the DCPI, is also investigated.
Automated Dynamic Cone
Penetrometer for Subgrade
Resilient Modulus Characterization
Ashraf M. Rahim and K. P. George
A. M. Rahim, California Department of Transportation, Central Region, Fresno, CA
93726. K. P. George, Department of Civil Engineering, University of Mississippi,
Carrier Hall, Room 203, University, MS 38677.
2. Rahim and George Paper No. 02-2039 71
TESTING PLAN
Test Sections
Selected were 12 test sections of 244 m (800 ft) in completed grad-
ing projects, reflecting a range of soil types in Mississippi. Table 1
lists the locations, soil classifications, and other properties of the soils
in each section. A schematic of the test activities and evaluation
strategies can be seen in Figure 2.
Field Testing and Sampling
Dynamic Cone Penetrometer Tests
Before the experimental program in the field, side-by-side tests were
conducted with a manual DCP and an automated DCP, establishing
that they provide statistically similar results. For the purposes of this
discussion, however, the penetration test results will be referred to
as DCP results, though most of the results were gathered employing
an automated DCP. The grading operation was completed in early
1999, and the subgrade of each section was tested in the summer of
1999. The scheme for the DCP investigation consisted of testing at
30 m (100 ft) intervals to a depth of 1 m (3 ft) in the subgrade. At the
same locations, the DCP tests were repeated in the spring and sum-
mer of 2000, after completion of pavement construction. After graph-
ing the results of penetration versus number of blows, as shown in
Figure 3, possible subgrade layering was sought by investigating
slope changes in the trend line. Through a visual inspection of the
plots, the points of slope change were identified, thus determining
different layers, each with a finite slope. The slope of a segment is
designated by the DCPI in units of millimeter/blow. As shown in
Figure 3, most of the 60 sample locations exhibited three layers. The
calculated DCPI for each layer was used for correlation with the cor-
responding laboratory-measured MR, as will be discussed in detail
in a later section.
Falling Weight Deflectometer Tests
Side-by-side FWD tests were also conducted in all 12 test sections,
before and after emplacement of pavement layers. The stiffness change
observed in the FWD test series will be compared with the corre-
sponding change in the results of DCP test series. How sensitive the
two tests are to the overburden will be discussed in a later section.
Detailed results of FWD–backcalculated moduli before and after
pavement construction can be found in Rahim and George (14).
Proctor Test Shelby Tube Samples
Section
No.
Roadway/
County Station
AASHTO
Classification
Max. Dry Densitya
, kN/m3
(pcf)
/ Optimum Moisture, %
Dry Densityb
, kN/m3
(pcf) / Moistureb
, %
1 SR25/Rankin 1303-1311 A-6 17.4 (110.8) / 14.0 18.0 (114.6) / 16.8
2 SR25/Rankin 1347-1355 A-6 18.2 (115.9) / 12.0 19.0 121.0) / 12.5
3 SR25/Rankin 1590-1598 A-6 17.1 (108.9) / 14.3 17.0 (108.3) / 16.9
4 SR25/Rankin 1696-1704 A-6 18.00 (114.6) / 13.0 18.4 (117.2) / 12.8
5 SR25/Leake 522-530 A-6 18.4 (117.2) / 14.0 19.2 (122.3) / 11.7
6 US45/Monroe 88-96 A-2-4 16.7 (106.4) / 15.0 17.5 (111.5) / 14.2
7 US45/Monroe 108-116 A-2-4 16.3 (103.8) / 16.0 17.4 (110.8) / 16.5
8 US45/Monroe 170-178 A-2-4 17.1 (108.9) / 14.5 18.4 (117.2) / 12.4
9 US45/Monroe 260-266 A-2-4 15.7 (100.0) / 17.5 16.8 (107.0) / 16.3
10 US45/Monroe 461-469 A-6 17.4 (110.8) / 14.5 18.1 (115.3) / 16.6
11 US45/Monroe 490-498 A-6 17.1 (108.9) / 15.5 18.2 (115.9) / 13.7
12 US45/Monroe 668-676 A-3 15.7 (100.0) / 15.5 16.5 (105.1) / 17.2
a
Standard Proctor.
b
Average dry density/moisture determined from Shelby tube samples.
TABLE 1 Soil: Physical Properties of Test Sections
FIGURE 1 Automated DCP in operation.
3. 72 Paper No. 02-2039 Transportation Research Record 1806
Soil Sampling and Testing
Composite bulk samples were collected from every section for rou-
tine laboratory testing, including the Standard Proctor compaction
(T99-90), with those results presented in Table 1. For MR testing,
Shelby tube samples were obtained from five locations at 61-m
(200-ft) intervals to a depth of 1.5 m (5 ft). Retrieved from each foot
was one test cylinder of 71 mm (2.8 in.) in diameter by 142 mm
(5.6 in.) in height, with the top three samples tested for the MR in the
laboratory, accumulating 15 MR values from each test section. At
completion of the MR test, the density and moisture contents of each
sample were determined. The average values per section are listed
in Table 1. As can be verified, the actual densities of the Shelby tube
samples are somewhat higher than the maximum Standard Proctor
densities (by 1.5% to 8.8%). It could be the case that those samples
have undergone recompaction and densification while the Shelby tube
was being pushed in extracting a sample. This problem is aggravated
in the top layer because of desiccation and shrinkage.
Laboratory Tests
Resilient Modulus Test
Laboratory MR tests, following the AASHTO TP46 Protocol, were
conducted employing the Mississippi Department of Transportation
repeated triaxial machine furnished by Industrial Process Control.
The deformation in the samples was monitored employing two lin-
ear variable differential transformers mounted outside of the testing
chamber. The average MR values for the last five loading cycles of a
100-cycle sequence yielded the MR. Figure 4 presents a typical plot
of MR versus deviatoric stress for a fine-grain soil sample. In total,
180 plots were prepared, from which the MR of each sample was
interpolated for the stress state representative of field conditions.
As a general rule, the modulus values of the first-foot samples of
fine-grain soil sections were always higher than the corresponding
coarse-grain soil values. This result could be attributed to desicca-
tion and shrinkage and consequent stiffening of the soil. Increase in
Study Plan
Field Testing
Shelby Tube DCP
Before and after pavement
layers construction
Laboratory Tests
Laboratory
resilient modulus
Atterberg limits, sieve analysis,
moisture content, dry density
Undisturbed
cylindrical samples
FWD
Before and after pavement
layers construction
Comparison of DCP and FWD
results before and after pavement
layers construction
LL, PI, wc, cu, γd, % passing #200 MR DCP index
1- Fine-grain soil correlation; MR = f (DCPI, LL, wc,)
2- Coarse-grain soil correlation; MR = f (DCPI, cu, ….)
FIGURE 2 Schematic chart showing field and laboratory tests and data analysis.
4. Rahim and George Paper No. 02-2039 73
soil suction in fine-grain soil, as a result of desiccation, in turn, gives
rise to larger modulus values.
Laboratory Routine Tests
Routine tests for soil classification (M145-87) (15) were conducted
on composite samples collected from each section (see Table 1).
The same routine tests determining soil state variables were per-
formed on soil from each test cylinder at completion of the MR test.
Those properties comprised some of the explanatory variables in the
regression analysis.
RESILIENT MODULUS RELATED TO DCPI
Resilient Modulus Determination
The plan called for correlating the MR to DCPI (possibly in con-
junction with other soil physical state properties). At each Shelby
tube location, samples from the first, second, and third foot yielded
MR–stress state curves, such as are shown in Figure 4. From the pen-
etration versus blows plot (typical plot in Figure 3), three DCPI val-
ues were extracted corresponding to the same sample location. Since
the MR is a function of stress state, the question arises as to selecting
an MR from an MR–stress state relation. Relying on the results of
Thompson and Robnett (16), Elliot (17) suggested using a zero con-
fining pressure and a 41.6-kPa (6-psi) deviatoric stress when selecting
an MR value from laboratory test data. With the recognition that
in-place subgrade must sustain the overburden of pavement layers,
in addition to the standard 18-kip axle load, in situ stress due to a
typical pavement is combined with stress due to a 20-kN (4,500-lb)
wheel load at a tire pressure of 690 kPa (100 psi). Stresses calcu-
lated by KENLAYER (18) yielded a stress state of 37 kPa (5.4 psi)
deviatoric stress and 14 kPa (2 psi) lateral stress. Making use of
the foregoing stress combination, one MR value for each sample was
interpolated from plots such as those in Figure 4.
MR –DCPI Correlation
By necessity, the 180 test cylinders from 12 test sections were clas-
sified into two groups: fine-grain and coarse-grain soil, in accordance
0
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1200
1400
0 10 20 30 40 50 60
No. of Blows
CumulativePenetration(mm)
20
40
60
80
100
120
0 10 20 30 40 50 60 70
Deviatoric Stress (kPa)
ResilientModulus(MPa)
Conf. pressure = 41 kPa
Conf. pressure = 28 kPa
Conf. pressure = 14 kPa
FIGURE 3 Typical ADCP test results (Monroe County, Station 89؉00).
FIGURE 4 Typical plot of laboratory MR test results (Monroe County, Station
670+00, Sample 1).
5. 74 Paper No. 02-2039 Transportation Research Record 1806
with AASHTO M145-87 (15). For each group, one regression model
relating the MR to the corresponding DCPI was attempted.
Because the DCP test is destructive in nature, it is not realistic to
expect a one-to-one relation between the MR and DCPI. Therefore,
it appeared prudent to include basic soil state properties as indepen-
dent variables in the regression models. After an exhaustive search
for variables that may have some bearing on the MR, the following
were selected in the regression analysis: dry density (γd), moisture
content (wc ), liquid limit (LL), plasticity index (PI ), percentage pass-
ing the #200 sieve, and uniformity coefficient (cu ). Table 2 lists the
range of dependent and independent variables for the two soil groups.
The Statistical Package for the Social Sciences (SPSS) (19) was
employed to perform the regression analysis in this study. For identi-
fying individual variables that exhibit high correlation with the MR, a
simple correlation analysis was conducted. Explanatory variables with
poor correlation with the MR were identified and in turn excluded from
further consideration. The PI for fine-grain soils and the percentage
passing the #200 sieve for coarse-grain soils are examples. For a reli-
able regression model, there should not be a strong correlation among
the explanatory variables. Explanatory variables, if they are highly cor-
related, would weaken the predictive power of the model, a problem
referred to as multicollinearity. Multicollinearity is always associated
with unstable estimated regression coefficients and can seriously
limit the use of regression analysis for inference and forecasting (20,
21). If such multicollinearity does exist, its effect can be eliminated
by coining or transforming variables. Simple correlations were con-
ducted exploring multicollinearity, among the transformed variables.
For illustrative purposes, the correlation matrix for coarse-grain soil is
presented in Table 3. It is clear from the table that the correlation coef-
ficients between each pair of transformed variables are relatively low,
less than 0.40 for all combinations. In addition, the coefficient of cor-
relation of the MR with each transformed variable has improved com-
pared with that before transformation. More detailed results and
analysis can be found in Rahim (22). The listed transformed variables
were, therefore, employed for developing the regression model.
In developing regression models, the curve estimation option in
SPSS was employed. The best forms of relation between the MR and
each of the explanatory variables were investigated, employing the
coefficient of determination (R2) as the best-fit criterion. The explana-
tory variables were then combined, and different model forms were
examined. The nonlinear regression option in SPSS was employed
to determine the regression coefficients. After an exhaustive search,
examining many different forms and interaction terms, the following
model forms were selected: for fine-grain soil,
and for coarse-grain soil,
where R2
is the coefficient of determination, and RMSE is the root-
mean-square error.
Listed in Table 4 are the values of regression coefficients and
summary statistics of the derived models. The F-test for multiple
regression relation was conducted to validate the significance of
the relationship between the MR and all of the explanatory variables
included in the models (20). With F* values for fine-grain and coarse-
grain soil much higher compared with F(0.95, p − 1, n − p), the evi-
dence is sufficient to show that a relationship does exist between the
MR and other explanatory variables. Note that p is the number of
explanatory variables, and n is the number of observations. The sig-
nificance of individual coefficients was tested employing the t-test.
At a confidence level of 95%, all of the coefficients are significant,
as t* > 1.96 (see Table 4).
To check the robustness of the developed models, residuals versus
the predicted MR values for the two soil groups were plotted. Such plots
are used to examine multicollinearity among the explanatory variables
after developing the model. The residual-MR plots for fine-grain and
coarse-grain soil are presented in Figure 5a and 5b, respectively.
No distinct pattern is observed, ruling out multicollinearity among
explanatory variables. Therefore, the models are well specified.
The laboratory MR values were plotted against the predicted MR
for fine-grain and coarse-grain soil, as shown in Figure 6a and 6b,
respectively. The plotted points clustering along the line of equality
are an indication of the robustness of the presented models.
M b
DCPI
c
w
R RMSE
R o=
+( )
= =
log
. . ( )
u
b1
dr
b2
cr
b3
γ
2
0 72 12 1 2
M a DCPI
LL
w
R RMSE
R o= ( ) +
= =
a1
dr
a2
c
a3
γ
2
0 71 31 6 1. . ( )
Soil Type Variable
Variable
notation Description Range
Dependent MR Laboratory resilient
modulusa
, MPa (psi)
31(4,436) – 269 (38,986)
DCPI Penetration Index, mm (in.) 3.7 (0.14) – 66.7 (2.63)
γd Dry density, kN/m3
(pcf) 15.1 (96.0) – 20.6 (131)
wc Moisture content, % 10.6 – 31.1
LL Liquid limit 20 - 57
Fine-grain
Independent
PI Plasticity index 2 - 31
Dependent MR Laboratory resilient
modulusa
, MPa (psi)
28 (4,058) – 158 (22,899)
DCPI Penetration index, mm (in.) 5.6 (0.22) – 40.0 (1.6)
γd Dry density, kN/m3
(pcf) 15.7 (99.7) – 19.1 (121.6)
wc Moisture content, % 12.4 – 22.0
cu Uniformity coefficient 2.8 - 925
Coarse-
grain
Independent
% #200 Percent passing # 200 sieve 7 - 33
a
MR values calculated at 37 kPa deviatoric stress and 14 kPa confining pressure.
TABLE 2 Ranges of Dependent and Independent Variables for Fine-Grain and
Coarse-Grain Soils
6. Rahim and George Paper No. 02-2039 75
Model Verification
To verify the predictability of the developed models, the DCP test was
conducted at four different locations in a construction site in Oxford,
Mississippi. Field density and moisture content were measured for the
four locations. Bulk soil samples were collected from each of the test
locations, and cylindrical specimens were reconstituted for labora-
tory MR testing, duplicating the moisture and density in the field.
Atterberg limits and grain size distribution were also determined, with
the soils classified as A-4, putting them in the fine-grain soil group.
The laboratory MR values were determined, for the three samples
from each location, at stress combination of 37 kPa deviatoric stress
and 14 kPa confining pressure. The average of the three MR values
is listed in Column 7 in Table 5. With employment of the fine-grain
soil model (Equation 1), the MR values were predicted and compared
with average laboratory values (Columns 8 and 7 of Table 5).
To compare the predicted and actual MR values, the test of dif-
ference of paired samples was conducted (23). Twelve modulus val-
ues (three per location) form the sample size. On the basis of the
test results (t* = −0.52 compared with Η t0.025, 11Η = 2.201), the null
hypothesis, H0—no significant difference exists between predicted
and actual values—is accepted. Viewed differently, no evidence
of significant difference exists between actual and predicted mod-
uli, which validates the predictability of one of the models devel-
oped in this study.
SENSITIVITY OF DCP TO CHANGES IN
SUBGRADE STIFFNESS
The MR –DCP correlation study was part of a larger study to char-
acterize Mississippi subgrade soils, in terms of MR. Because of the
need for MR values in both pavement design and rehabilitation, other
tests were conducted, including FWD tests, before and after pave-
ment layer construction, and DCP atop subgrade following coring
through pavement layers. Results from these tests made it possible
to investigate the sensitivity of the DCP test to changes in subgrade
stiffness brought about by overburden pressure.
A comparison between backcalculated moduli from FWD deflec-
tion data conducted directly on the subgrade and after pavement layer
construction revealed that modulus values were enhanced primar-
ily due to overburden imposed by pavement layers. On average, the
modulus was enhanced by 40% and 100% for fine-grain and coarse-
grain soils, respectively. More details of the comparison, results, and
analysis can be found in Rahim and George (14). The DCP results
before and after pavement layer construction (DCPI1 and DCPI2 )
were compared to investigate whether the stiffness change, captured
by backcalculated moduli, could be in line with the DCPI change.
Figure 7a and 7b compare DCPI1 and DCPI2 for fine-grain and
coarse-grain soil, respectively.
As expected, the ratios of DCPI2 / DCPI1 are different for the two
soil types. With stiffening of the soil, the DCPI2 decreased in rela-
tion to the DCPI1, providing percentage decreases of 20% and 34%
for fine-grain and coarse-grain soil, respectively. A scrutiny of the
test conditions reveals that the subgrade is only partially confined
when tested through the core hole. A recent study by Chen et al. (8)
showed that the DCPI2, determined through a core hole, was 11%
smaller than the DCPI1 with no overburden. The authors gave no
clue as to the type of soil tested, however. In the second part of their
experiment, the DCP was driven through the asphalt layer deter-
mining DCPIasp for fully confined conditions, observing 30%
reduction from DCPI2 to DCPasp. If this 30% reduction were to be
applied to our results, it could be shown that from a no-overburden
to full-overburden state, the DCPI could decrease by 44% and 60%
for fine-grain and coarse-grain soil, respectively. These changes
(decreases) in the DCPI are somewhat in line with the changes
in backcalculated moduli of 40% for fine-grain and 100% for
coarse-grain soils.
A basic difference in the test procedure may be cited for the poor
or inferior correlation between the DCPI change and backcalculated
MR DCPI/ Log cu γdr wcr
MR 1 0.35 -0.42
DCPI / Log cu -0.45 -0.20 0.03
γdr 0.35 1 -0.40
wcr -0.42
-0.45
1
-0.20
0.03 -0.40 1
γdr = Actual density / standard Proctor maximum density.
wcr = Actual moisture content / optimum moisture content.
Soil Type Coefficient Value t* F* RMSE R2
ao 27.86
a1 -0.114
a2 7.82Fine-grain
a3 1.925
46.5a
31.45 0.71
bo 90.68
b1 -0.305
b2 -0.935Coarse-grain
b3 0.674
4.33
2.05
4.60
10.81
9.99
10.48
1.98
2.17
31.82b
12.12 0.72
a
Critical F = 2.50
b
Critical F = 2.55
TABLE 3 Correlation Matrix of Transformed Explanatory Variables for
Coarse-Grain Soil
TABLE 4 Summary Statistics for Two Soil Group Models
7. 76 Paper No. 02-2039 Transportation Research Record 1806
moduli change. The difference is that the DCP test is destructive in
nature, whereas the FWD test is not. Because the soil is plasticized
while the cone is driven into the soil, the effect of confinement
hardly arises in the DCP test; accordingly, the DCPI change from no
overburden to full overburden is not as significant as is the modulus
change in the FWD test. Nonetheless, that the DCP change closely
follows the modulus change is an indication of the viability of the
DCP for monitoring modulus changes of in-place subgrade.
SUMMARY AND CONCLUSIONS
The focus of this study was to investigate the use of the automated
DCP for subgrade soil characterization. In 12 sections of prepared
subgrade, side-by-side DCP and FWD tests were conducted, and
undisturbed samples for MR tests were collected. MR values were
regressed against the DCPI other soil state properties, obtaining
models for fine-grain and coarse-grain soil. A feature of the models
is that in addition to the DCPI, other soil state variables are found to
be significant in MR prediction. The models were verified by repeat-
ing the tests in another site and comparing measured and predicted
moduli. Following is a summary of the significant conclusions:
1. The automated DCP is a simple and expedient device for field
testing of soils and particulate material.
2. Shelby tube samples extracted for MR testing had suffered sig-
nificant sample disturbance, especially those from the desiccated
top layer.
3. As mandated by data, two models were developed—one for
fine-grain and another for coarse-grain soil. The model predictabil-
ity is substantially increased by including soil state properties as
additional explanatory variables.
4. The predictability of the fine-grain soil model was substantiated
by testing an independent site with excellent comparison between
Location
#
Actual
moisture
contenta
, %
Dry densitya
,
kN/m3
Moisture
ratioa
Density
ratioa
Liquid
limita
Actual
MR
a
,
MPa
Predicted
MR
a
,
MPa
1 17.1 0.76 1.05 39.0 189 216
2 17.8 0.76 1.08 37.0 197 193
3 16.8 0.93 1.03 39.0 141 146
4
12.6
12.6
15.3
13.0 16.7 0.79 1.02 28.0 113 103
a
Average of three samples.
(a)
(b)
-40
-30
-20
-10
0
10
20
30
40
0 50 100 150
Predicted MR, MPa
Residuals,MPa
-100
-80
-60
-40
-20
0
20
40
60
80
100
0 50 100 150 200 250 300
Predicted MR, MPa
Residuals,MPa
FIGURE 5 Residuals versus predicted MR values for
(a) fine-grain soil and (b) coarse-grain soil.
(a)
(b)
0
20
40
60
80
100
120
140
160
180
0 20 40 60 80 100 120 140 160 180
Laboratory MR, MPa
PredictedMR,MPa
0
50
100
150
200
250
300
0 50 100 150 200 250 300
Actual MR, MPa
PredictedMR,MPa
FIGURE 6 Laboratory versus predicted MR values for
(a) fine-grain soil and (b) coarse-grain soil.
TABLE 5 Physical and Mechanical Properties of Samples Tested for Model Verification
8. Rahim and George Paper No. 02-2039 77
the measured and predicted MR values. The coarse-grain soil model,
however, awaits verification.
5. The sensitivity of the DCP test procedure is substantiated by
comparing the change in DCPI (before and after emplacement of pave-
ment) with the corresponding change in FWD backcalculated moduli.
By way of general conclusions and recommendation, it is advanced
that for the range of soils tested, the developed MR –DCPI models
provide useful predictions of MR.
ACKNOWLEDGMENTS
This paper is a part of the study entitled Subgrade Characterization
for Highway Pavement Design, conducted by the Department of
Civil Engineering, University of Mississippi, in cooperation with
the Mississippi Department of Transportation (MDOT) and
FHWA. Technical help received from Alfred Crawley, Joy
Portera, Bill Barstis, Johnny Hart, and Alan Hatch of MDOT, and
Jianrong Yu, of the university, is acknowledged.
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The opinion, findings, and conclusions expressed in this paper are those of the
authors and not necessarily those of the Mississippi Department of Transportation
or FHWA. This paper does not constitute a standard, specification, or regulation.
Publication of this paper sponsored by Committee on Strength and Deformation
Characteristics of Pavement Sections.
FIGURE 7 Comparison of DCPI1 and DCPI2 (before and after
pavement construction) for (a) fine-grain soil and
(b) coarse-grain soil.
0
10
20
30
40
50
60
70
80
0 20 40 60 80
(DCPI)1, mm/blow
(DCPI)2,mm/blow
(a)
(b)
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70
(DCPI)1, mm/blow
(DCPI)2,mm/blow