1) Cement-treated soil samples were cured under different consolidation conditions, including single-dimensional and isotropic consolidation, to examine how consolidation pressure and curing time affect peak and residual strength.
2) Tests found that strength increases with higher consolidation pressure and longer curing time due to increased density from consolidation and cement hydration. However, applying consolidation pressure after a delay reduced strength.
3) Isotropic consolidation led to higher volumetric strains and strengths than single-dimensional consolidation due to the higher mean effective stress. Residual strength also increased with higher consolidation pressure during curing.
This document summarizes a research study on the effect of consolidation stress on the strength of lime-stabilized soil. Laboratory tests including vane shear tests, unconfined compression tests, and triaxial tests were conducted on natural soil stabilized with 3-9% lime and cured for 7-28 days. The following key findings were reported:
1) Undrained cohesion and UCC strength increased with higher lime content and longer curing periods. However, under a given lime content and curing, undrained cohesion increased but angle of internal friction decreased with higher consolidation stress.
2) Triaxial tests showed the undrained strength of stabilized soil, like natural soil, is dependent on the consolidation stress. Und
Predicting the Workability of Fresh Concrete Using Simple Pull-out TestIJRESJOURNAL
This study explores using a simple pull-out test to predict the workability of fresh concrete as an alternative to other common tests. Concrete samples with varying water-cement ratios were tested for slump, compacting factor, and pull-out strength. Regression analysis showed pull-out strength highly correlates with compacting factor. Calculated and measured compacting factors matched closely. The pull-out test provides a fast, easy means to determine workability on-site and is recommended as an alternative to other tests.
Brittle Ductile Behaviour For ( STEEL - RIENFORCED CONCRETE - CONCRETE )Ahmed Abdullah
- Steel exhibits ductile behavior by allowing large strains before rupturing or failing. It can stretch substantially under tension.
- Concrete and cast iron exhibit brittle behavior, failing abruptly with little warning once their strength limits are exceeded. Their stress-strain curves are steep with little plastic deformation.
- Reinforced concrete can show ductile behavior if designed properly with sufficient confinement and ductile reinforcement to allow inelastic deformations without collapse.
The Crack Pattern Of R.C Beams Under LoadingAhmed Abdullah
1. A reinforced concrete beam was tested under static two-point concentrated loading to study the effect of different web reinforcement arrangements on ultimate shear strength.
2. It was observed that diagonal cracks developed first in deeper beams while flexural cracks developed first in shallower beams with sufficient reinforcement.
3. The crack pattern and failure mode were similar across all test beams despite variations in web reinforcement, with diagonal cracks forming first in deeper beams.
Evaluation of concrete spall repairs by pullout testfrank collins
This document summarizes a study that evaluated concrete spall repairs using pullout tests. Concrete specimens were damaged via an initial pullout test, repaired with epoxy mortar, and subjected to a second pullout test. The tests showed that:
1) Pullout force of repaired specimens was linearly correlated with concrete cylinder compressive strength up to around 45 kN/2.26 MPa, but diminished at higher strengths.
2) Pullout force/stress of repaired specimens increased similarly to concrete specimens as age increased up to 90 days, but was lower than unrepaired concrete.
3) Higher initial pullout damage forces resulted in higher pullout forces for repaired specimens, up to around 43
Construction Materials Engineering and Testingmecocca5
This document provides an overview of materials testing services for soil, aggregate, concrete, and masonry. It describes common laboratory and field tests for evaluating the properties and quality of construction materials, including tests for soil particle size and compaction, concrete slump and strength, and masonry compressive strength. The document emphasizes that materials testing should be performed by properly trained personnel according to standardized test methods and that test results should be reported in a timely manner.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
Experimental study on critical closing pressure of mudstone fractured reservoirsIJRES Journal
This study examines the critical closing pressure of fractures in mudstone reservoir cores from the Daqing oilfield in China. Laboratory experiments subjected fractured and unfractured mudstone cores to increasing external pressures while measuring permeability. The critical closing pressure is defined as the pressure when fractured core permeability matches unfractured permeability, indicating fracture closure. Results show fractured cores have higher permeability than unfractured cores due to fractures. Permeability generally decreases exponentially with increasing pressure. By calculating sensitivity equations relating permeability and production pressure difference, the study estimates critical closing pressures under reservoir conditions are lower than values from external pressure experiments. The study provides guidance but notes limitations in fully simulating complex in-situ stress conditions.
This document summarizes a research study on the effect of consolidation stress on the strength of lime-stabilized soil. Laboratory tests including vane shear tests, unconfined compression tests, and triaxial tests were conducted on natural soil stabilized with 3-9% lime and cured for 7-28 days. The following key findings were reported:
1) Undrained cohesion and UCC strength increased with higher lime content and longer curing periods. However, under a given lime content and curing, undrained cohesion increased but angle of internal friction decreased with higher consolidation stress.
2) Triaxial tests showed the undrained strength of stabilized soil, like natural soil, is dependent on the consolidation stress. Und
Predicting the Workability of Fresh Concrete Using Simple Pull-out TestIJRESJOURNAL
This study explores using a simple pull-out test to predict the workability of fresh concrete as an alternative to other common tests. Concrete samples with varying water-cement ratios were tested for slump, compacting factor, and pull-out strength. Regression analysis showed pull-out strength highly correlates with compacting factor. Calculated and measured compacting factors matched closely. The pull-out test provides a fast, easy means to determine workability on-site and is recommended as an alternative to other tests.
Brittle Ductile Behaviour For ( STEEL - RIENFORCED CONCRETE - CONCRETE )Ahmed Abdullah
- Steel exhibits ductile behavior by allowing large strains before rupturing or failing. It can stretch substantially under tension.
- Concrete and cast iron exhibit brittle behavior, failing abruptly with little warning once their strength limits are exceeded. Their stress-strain curves are steep with little plastic deformation.
- Reinforced concrete can show ductile behavior if designed properly with sufficient confinement and ductile reinforcement to allow inelastic deformations without collapse.
The Crack Pattern Of R.C Beams Under LoadingAhmed Abdullah
1. A reinforced concrete beam was tested under static two-point concentrated loading to study the effect of different web reinforcement arrangements on ultimate shear strength.
2. It was observed that diagonal cracks developed first in deeper beams while flexural cracks developed first in shallower beams with sufficient reinforcement.
3. The crack pattern and failure mode were similar across all test beams despite variations in web reinforcement, with diagonal cracks forming first in deeper beams.
Evaluation of concrete spall repairs by pullout testfrank collins
This document summarizes a study that evaluated concrete spall repairs using pullout tests. Concrete specimens were damaged via an initial pullout test, repaired with epoxy mortar, and subjected to a second pullout test. The tests showed that:
1) Pullout force of repaired specimens was linearly correlated with concrete cylinder compressive strength up to around 45 kN/2.26 MPa, but diminished at higher strengths.
2) Pullout force/stress of repaired specimens increased similarly to concrete specimens as age increased up to 90 days, but was lower than unrepaired concrete.
3) Higher initial pullout damage forces resulted in higher pullout forces for repaired specimens, up to around 43
Construction Materials Engineering and Testingmecocca5
This document provides an overview of materials testing services for soil, aggregate, concrete, and masonry. It describes common laboratory and field tests for evaluating the properties and quality of construction materials, including tests for soil particle size and compaction, concrete slump and strength, and masonry compressive strength. The document emphasizes that materials testing should be performed by properly trained personnel according to standardized test methods and that test results should be reported in a timely manner.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
Experimental study on critical closing pressure of mudstone fractured reservoirsIJRES Journal
This study examines the critical closing pressure of fractures in mudstone reservoir cores from the Daqing oilfield in China. Laboratory experiments subjected fractured and unfractured mudstone cores to increasing external pressures while measuring permeability. The critical closing pressure is defined as the pressure when fractured core permeability matches unfractured permeability, indicating fracture closure. Results show fractured cores have higher permeability than unfractured cores due to fractures. Permeability generally decreases exponentially with increasing pressure. By calculating sensitivity equations relating permeability and production pressure difference, the study estimates critical closing pressures under reservoir conditions are lower than values from external pressure experiments. The study provides guidance but notes limitations in fully simulating complex in-situ stress conditions.
The document summarizes a study that investigated the effect of gap size on soil strength properties in direct shear tests. It examined three soils with five different gap sizes between 0.25mm and 2mm under three confining stresses. The tests found that as gap size increased, shear stress decreased and vertical deformation increased. When normalized by grain size, the relationship between gap size and friction angle differed by soil, with the smallest-grained soil leveling off at higher gap sizes. Further testing could explore higher and lower gap sizes to better understand the effect of gap size on friction angle.
This document summarizes tests performed on fresh and hardened concrete. For fresh concrete, tests included the compaction factor test, slump test, and Vee-Bee test to measure workability. For hardened concrete, non-destructive tests like rebound hammer, ultrasonic pulse velocity and destructive compression tests were performed. The compression test resulted in a compressive strength of 19.39MPa, lower than desired, indicating the quality of the hardened concrete. Various properties of hardened concrete can also be analyzed over time using smart sensor chips embedded in samples.
The document summarizes an experimental study that investigated the friction coefficient between concrete block and steel plate bolted joints. Specifically, it tested 30 specimen groups to determine the effects of various parameters on the friction coefficient, including: the type and amount of glue between the concrete and steel surfaces; the type, size, and amount of sand on the concrete surface; the shape and dimensions of grooves in the steel plate; and the bolt pre-tightening force. The experiments found that the friction coefficient increased with greater amounts of glue on the steel plate surface and higher bolt pre-tightening pressures. It also examined using different sizes of sand and shapes of steel plate grooves to optimize the friction coefficient.
This document summarizes a research project investigating how the addition time of superplasticizer affects the rheological properties of self-consolidating cement paste. The project aims to understand how mixing procedures and addition sequence influence the robustness of SCC mixtures. Test results show that for a VMA-type mix design, rheological parameters are more sensitive to the addition time of superplasticizer compared to variations in water content, while a powder-type mix design shows the opposite. Tests also indicate that limestone filler has a more significant influence on rheological properties than the presence of VMA, type of superplasticizer, or use of silica fume and fly ash.
This document discusses various methods for classifying rock masses, including the Geomechanics Classification (RMR) method developed by Bieniawski, the Norwegian Q-System, and the RMi method. It provides details on how each system determines classification based on parameters such as rock quality, discontinuity spacing and condition, groundwater conditions, and orientation. The classifications are then used to determine appropriate excavation dimensions and support requirements for tunnels based on the rock mass quality.
Schmidt's Hammer Rebound Value Analysis for finding Uniaxial Compressive Stre...Jasmeet Singh Saluja
An innovative & easy way of establishing a relationship ship between Schmidt's Hammer Rebound value & Uniaxial Compressive Strength, Point Load Index & Density of rocks to obtain the value of UCS on site.
This method helps in eliminating the need of laboratory analysis of rock for UCS, Point Load Index & density determination.
Segregation in Concrete
The main explanation of this report of Segregation in concrete in terms of
concrete and self-compacting. The aim was to find an analytical relation to
estimating the risk of sedimentation, using the characteristics of the particles
and those of the mortars. The prediction of surface effect segregation (i.e.
transportation of different particle size fractions during heap formation) has
been the subject of a significant level of study.
Explanation of the type of segregation in term size, dry, wet, and water separate
and effect segregation in concrete in term strength and cracks, and
Prevention of Segregation in Concrete.
I brought up an example that supports segregation in concrete which is used
in Kurdistan Region, and explaining the example in term caused segregation
the effect in concrete.
A review on different destructive methods to determine the compressive streng...IJERD Editor
Determination of the compressive strength of an existing masonry attracted the attention of many scientists and researchers around the world. Most of these researchers, scientists and engineers want to find the best way to obtain the compressive strength of masonry in situ with high accuracy, and less cost. There are many methods to determine the compressive strength of masonry. Some of these methods are destructive methods and others are non-destructive methods and others are partially destructive. Each one of these testing methods has advantages and disadvantages .this paper presents different destructive testing Methodsfor obtaining the compressive strength of an existing masonry. Testing procedure, the main advantages and the problems of each method are explored.
Literature Review of Experimental Study on Load Bearing Masonry WallIOSRJMCE
Masonry load bearing wall subjected to vertical concentric and eccentric loading may collapse through instability. In this Paper the buckling behavior of masonry load bearing wall of different slenderness ratio were investigated by many researcher has been reviewed via testing a series of scale masonry wall subjected to concentric and eccentric vertical loading. The influence of nonlinear behavior of interface element, slenderness ratio and various end conditions have been investigated together with the effect of different end eccentricity of vertical load.
This document presents a new approach for determining the tensile and shear strengths of normal weight concrete. It discusses existing methods for evaluating these properties and their limitations. The author proposes using the failure patterns of two concrete cylinders under compression - with the same cross-sectional area but different heights - to define a characteristic fracture angle. This angle would be a function of the concrete's compressive strength. Equations are then developed relating the fracture angle to the tensile and shear strengths. The significance of using two cylinders is that it introduces the concept of the direction of the failure plane as a way to predict mechanical properties from a standard compression test.
This document discusses strength parameters for clays, including:
- The peak friction angle for clays decreases with increasing plasticity index and activity. Critical state friction angles range from 20-25° for kaolin clays and 20° for montmorillonite clays.
- The Hvorslev failure envelope models the strength of overconsolidated clays using equivalent friction angle and cohesion parameters.
- Undrained shear strength of clays decreases with increasing liquidity index and increases with overconsolidation ratio. Empirical equations relate strength to plasticity index and preconsolidation stress.
- Shear bands form after peak strength due to strain localization. Their thickness is 7-10 particle diameters
The document discusses different types of triaxial tests used to determine the shear strength parameters of soils, including consolidated drained (CD), consolidated undrained (CU), and unconsolidated undrained (UU) tests. It focuses on the UU test, explaining the test procedure, data analysis, and determination of shear strength parameters. Key points include the use of Skempton's pore water pressure parameters B and A, the effect of saturation and drainage conditions, and practical applications of UU analysis such as modeling embankment and footing construction on soft clays.
This document summarizes a study that investigated the influence of shear bond strength on the compressive strength and stress-strain characteristics of masonry. The study varied the shear bond strength between soil-cement blocks and cement-lime mortar using different bonding enhancement techniques, without altering the strength or modulus of the individual materials. Masonry prisms were tested under different bond strength conditions and ratios of block modulus to mortar modulus. The results showed that compressive strength increased linearly with bond strength when the block modulus was less than the mortar modulus. Bond strength was also found to influence the modulus of masonry depending on the relative stiffness of the block and mortar.
This document summarizes a study that evaluated the ratio of splitting tensile strength to compressive strength (ftsp/fc) of concrete with compressive strengths ranging from 4 to 120 MPa. A large dataset from various sources was used to develop regression equations relating ftsp/fc to fc. The most accurate equation, with the lowest integral absolute error rate, was ftsp/fc = 0.3870 - 0.3700/fc. This equation can be used to predict strengths of high-strength concrete under confinement using Johnston's strength criterion, without separate triaxial compression tests.
International Journal of Engineering Research and DevelopmentIJERD Editor
The document investigates the effects of silica fume and fly ash on the flexural strength of roller compacted concrete. Tests found that using fly ash alone decreased 28-day flexural strength while silica fume alone slightly increased it. However, using silica fume and fly ash together resulted in higher flexural strength than either additive alone or the control mixture. The maximum 28-day flexural strength of 4.53 MPa was achieved with a mixture of 85% OPC, 10% fly ash, and 5% silica fume.
This document discusses direct shear tests which are used to determine the shear strength of soils. It provides definitions of key terms like shear strength and failure. It explains that shear strength depends on interactions between soil particles and failures occurs when particles slide past each other. It describes the direct shear test procedure which involves applying normal and shear stresses to a soil sample in a shear box to cause failure. The document provides equations to calculate normal stress, shear stress, dry unit weight and void ratio from direct shear test data.
The document discusses experimental investigations into the material properties and compressive/shear behavior of brick masonry with different mortar ratios. Tests were conducted on brick units, mortar cubes/cylinders, and brick prism triplets with varying mortar ratios to evaluate properties like compressive strength, bond strength, and interface behavior. The results were then evaluated and compared to better understand the behavior of unreinforced brick masonry under shear and compression loading for use in numerical simulations.
This document discusses the key characteristics of soil strength and deformation behavior. It introduces the Mohr-Coulomb failure criterion and explains that soil strength depends on factors like effective stress, void ratio, composition, and stress history. It describes the different failure envelopes for peak, critical, and residual strength. It also discusses concepts like dilatancy, anisotropy, and how strength is influenced by factors like density, drainage conditions, overconsolidation ratio, and temperature. The document emphasizes the fundamental factors controlling soil strength and stress-deformation behavior.
Non-destructive testing methods like the rebound hammer test and ultrasonic pulse velocity test can evaluate concrete structures without damaging them. The rebound hammer test measures surface hardness to estimate compressive strength, while ultrasonic pulse velocity testing determines the speed of ultrasonic pulses traveling through concrete to evaluate quality and uniformity. Both tests are influenced by factors like moisture, aggregates, and reinforcing steel, so they provide an initial assessment of concrete rather than absolute measurements. Non-destructive testing allows inspection of both new and existing concrete structures for defects and compliance with design specifications.
Laboratory experimental study and elastic wave velocity on physical propertie...HoangTienTrung1
Pressure grouting has gained popularity as a soil reinforcement method. However, the behavior of the interface between rock and grout is not well known. This study investigates the interaction of pressure grouting and rock, through a series of laboratory tests performed on specially designed and fabricated equipment and using standard testing methods. The test measures the density, compressional strength, and frictional resistance of grout relative to the applied pressure and curing time. Simultaneously, the velocities of the elastic wave traveling through the grout are obtained to develop correlations between the physical properties of the grout and the test conditions. The results of the tests show that the density, compressional strength, and frictional resistance of the grout increase with applied pressure and curing time. The strengths of the influencing factors are seen to be correlated within the range of the test conditions. Using the results of these tests, the potential development of a new method that requires less cement was discussed.
1) The document reports on a laboratory experiment to test the compressive and tensile strengths of concrete. Cubes and cylinders were cured for 14 days and then tested.
2) The compressive strength of the cubes was found to be 19.11 N/mm2 on average, while the cylinders was 14.71 N/mm2. The ratio of 0.8 between cylinder and cube strengths was as expected.
3) The tensile strength was found to be 2.05 N/mm2, which is approximately 10% of the compressive strength of the cubes, showing that concrete is weaker in tension.
The document summarizes a study that investigated the effect of gap size on soil strength properties in direct shear tests. It examined three soils with five different gap sizes between 0.25mm and 2mm under three confining stresses. The tests found that as gap size increased, shear stress decreased and vertical deformation increased. When normalized by grain size, the relationship between gap size and friction angle differed by soil, with the smallest-grained soil leveling off at higher gap sizes. Further testing could explore higher and lower gap sizes to better understand the effect of gap size on friction angle.
This document summarizes tests performed on fresh and hardened concrete. For fresh concrete, tests included the compaction factor test, slump test, and Vee-Bee test to measure workability. For hardened concrete, non-destructive tests like rebound hammer, ultrasonic pulse velocity and destructive compression tests were performed. The compression test resulted in a compressive strength of 19.39MPa, lower than desired, indicating the quality of the hardened concrete. Various properties of hardened concrete can also be analyzed over time using smart sensor chips embedded in samples.
The document summarizes an experimental study that investigated the friction coefficient between concrete block and steel plate bolted joints. Specifically, it tested 30 specimen groups to determine the effects of various parameters on the friction coefficient, including: the type and amount of glue between the concrete and steel surfaces; the type, size, and amount of sand on the concrete surface; the shape and dimensions of grooves in the steel plate; and the bolt pre-tightening force. The experiments found that the friction coefficient increased with greater amounts of glue on the steel plate surface and higher bolt pre-tightening pressures. It also examined using different sizes of sand and shapes of steel plate grooves to optimize the friction coefficient.
This document summarizes a research project investigating how the addition time of superplasticizer affects the rheological properties of self-consolidating cement paste. The project aims to understand how mixing procedures and addition sequence influence the robustness of SCC mixtures. Test results show that for a VMA-type mix design, rheological parameters are more sensitive to the addition time of superplasticizer compared to variations in water content, while a powder-type mix design shows the opposite. Tests also indicate that limestone filler has a more significant influence on rheological properties than the presence of VMA, type of superplasticizer, or use of silica fume and fly ash.
This document discusses various methods for classifying rock masses, including the Geomechanics Classification (RMR) method developed by Bieniawski, the Norwegian Q-System, and the RMi method. It provides details on how each system determines classification based on parameters such as rock quality, discontinuity spacing and condition, groundwater conditions, and orientation. The classifications are then used to determine appropriate excavation dimensions and support requirements for tunnels based on the rock mass quality.
Schmidt's Hammer Rebound Value Analysis for finding Uniaxial Compressive Stre...Jasmeet Singh Saluja
An innovative & easy way of establishing a relationship ship between Schmidt's Hammer Rebound value & Uniaxial Compressive Strength, Point Load Index & Density of rocks to obtain the value of UCS on site.
This method helps in eliminating the need of laboratory analysis of rock for UCS, Point Load Index & density determination.
Segregation in Concrete
The main explanation of this report of Segregation in concrete in terms of
concrete and self-compacting. The aim was to find an analytical relation to
estimating the risk of sedimentation, using the characteristics of the particles
and those of the mortars. The prediction of surface effect segregation (i.e.
transportation of different particle size fractions during heap formation) has
been the subject of a significant level of study.
Explanation of the type of segregation in term size, dry, wet, and water separate
and effect segregation in concrete in term strength and cracks, and
Prevention of Segregation in Concrete.
I brought up an example that supports segregation in concrete which is used
in Kurdistan Region, and explaining the example in term caused segregation
the effect in concrete.
A review on different destructive methods to determine the compressive streng...IJERD Editor
Determination of the compressive strength of an existing masonry attracted the attention of many scientists and researchers around the world. Most of these researchers, scientists and engineers want to find the best way to obtain the compressive strength of masonry in situ with high accuracy, and less cost. There are many methods to determine the compressive strength of masonry. Some of these methods are destructive methods and others are non-destructive methods and others are partially destructive. Each one of these testing methods has advantages and disadvantages .this paper presents different destructive testing Methodsfor obtaining the compressive strength of an existing masonry. Testing procedure, the main advantages and the problems of each method are explored.
Literature Review of Experimental Study on Load Bearing Masonry WallIOSRJMCE
Masonry load bearing wall subjected to vertical concentric and eccentric loading may collapse through instability. In this Paper the buckling behavior of masonry load bearing wall of different slenderness ratio were investigated by many researcher has been reviewed via testing a series of scale masonry wall subjected to concentric and eccentric vertical loading. The influence of nonlinear behavior of interface element, slenderness ratio and various end conditions have been investigated together with the effect of different end eccentricity of vertical load.
This document presents a new approach for determining the tensile and shear strengths of normal weight concrete. It discusses existing methods for evaluating these properties and their limitations. The author proposes using the failure patterns of two concrete cylinders under compression - with the same cross-sectional area but different heights - to define a characteristic fracture angle. This angle would be a function of the concrete's compressive strength. Equations are then developed relating the fracture angle to the tensile and shear strengths. The significance of using two cylinders is that it introduces the concept of the direction of the failure plane as a way to predict mechanical properties from a standard compression test.
This document discusses strength parameters for clays, including:
- The peak friction angle for clays decreases with increasing plasticity index and activity. Critical state friction angles range from 20-25° for kaolin clays and 20° for montmorillonite clays.
- The Hvorslev failure envelope models the strength of overconsolidated clays using equivalent friction angle and cohesion parameters.
- Undrained shear strength of clays decreases with increasing liquidity index and increases with overconsolidation ratio. Empirical equations relate strength to plasticity index and preconsolidation stress.
- Shear bands form after peak strength due to strain localization. Their thickness is 7-10 particle diameters
The document discusses different types of triaxial tests used to determine the shear strength parameters of soils, including consolidated drained (CD), consolidated undrained (CU), and unconsolidated undrained (UU) tests. It focuses on the UU test, explaining the test procedure, data analysis, and determination of shear strength parameters. Key points include the use of Skempton's pore water pressure parameters B and A, the effect of saturation and drainage conditions, and practical applications of UU analysis such as modeling embankment and footing construction on soft clays.
This document summarizes a study that investigated the influence of shear bond strength on the compressive strength and stress-strain characteristics of masonry. The study varied the shear bond strength between soil-cement blocks and cement-lime mortar using different bonding enhancement techniques, without altering the strength or modulus of the individual materials. Masonry prisms were tested under different bond strength conditions and ratios of block modulus to mortar modulus. The results showed that compressive strength increased linearly with bond strength when the block modulus was less than the mortar modulus. Bond strength was also found to influence the modulus of masonry depending on the relative stiffness of the block and mortar.
This document summarizes a study that evaluated the ratio of splitting tensile strength to compressive strength (ftsp/fc) of concrete with compressive strengths ranging from 4 to 120 MPa. A large dataset from various sources was used to develop regression equations relating ftsp/fc to fc. The most accurate equation, with the lowest integral absolute error rate, was ftsp/fc = 0.3870 - 0.3700/fc. This equation can be used to predict strengths of high-strength concrete under confinement using Johnston's strength criterion, without separate triaxial compression tests.
International Journal of Engineering Research and DevelopmentIJERD Editor
The document investigates the effects of silica fume and fly ash on the flexural strength of roller compacted concrete. Tests found that using fly ash alone decreased 28-day flexural strength while silica fume alone slightly increased it. However, using silica fume and fly ash together resulted in higher flexural strength than either additive alone or the control mixture. The maximum 28-day flexural strength of 4.53 MPa was achieved with a mixture of 85% OPC, 10% fly ash, and 5% silica fume.
This document discusses direct shear tests which are used to determine the shear strength of soils. It provides definitions of key terms like shear strength and failure. It explains that shear strength depends on interactions between soil particles and failures occurs when particles slide past each other. It describes the direct shear test procedure which involves applying normal and shear stresses to a soil sample in a shear box to cause failure. The document provides equations to calculate normal stress, shear stress, dry unit weight and void ratio from direct shear test data.
The document discusses experimental investigations into the material properties and compressive/shear behavior of brick masonry with different mortar ratios. Tests were conducted on brick units, mortar cubes/cylinders, and brick prism triplets with varying mortar ratios to evaluate properties like compressive strength, bond strength, and interface behavior. The results were then evaluated and compared to better understand the behavior of unreinforced brick masonry under shear and compression loading for use in numerical simulations.
This document discusses the key characteristics of soil strength and deformation behavior. It introduces the Mohr-Coulomb failure criterion and explains that soil strength depends on factors like effective stress, void ratio, composition, and stress history. It describes the different failure envelopes for peak, critical, and residual strength. It also discusses concepts like dilatancy, anisotropy, and how strength is influenced by factors like density, drainage conditions, overconsolidation ratio, and temperature. The document emphasizes the fundamental factors controlling soil strength and stress-deformation behavior.
Non-destructive testing methods like the rebound hammer test and ultrasonic pulse velocity test can evaluate concrete structures without damaging them. The rebound hammer test measures surface hardness to estimate compressive strength, while ultrasonic pulse velocity testing determines the speed of ultrasonic pulses traveling through concrete to evaluate quality and uniformity. Both tests are influenced by factors like moisture, aggregates, and reinforcing steel, so they provide an initial assessment of concrete rather than absolute measurements. Non-destructive testing allows inspection of both new and existing concrete structures for defects and compliance with design specifications.
Laboratory experimental study and elastic wave velocity on physical propertie...HoangTienTrung1
Pressure grouting has gained popularity as a soil reinforcement method. However, the behavior of the interface between rock and grout is not well known. This study investigates the interaction of pressure grouting and rock, through a series of laboratory tests performed on specially designed and fabricated equipment and using standard testing methods. The test measures the density, compressional strength, and frictional resistance of grout relative to the applied pressure and curing time. Simultaneously, the velocities of the elastic wave traveling through the grout are obtained to develop correlations between the physical properties of the grout and the test conditions. The results of the tests show that the density, compressional strength, and frictional resistance of the grout increase with applied pressure and curing time. The strengths of the influencing factors are seen to be correlated within the range of the test conditions. Using the results of these tests, the potential development of a new method that requires less cement was discussed.
1) The document reports on a laboratory experiment to test the compressive and tensile strengths of concrete. Cubes and cylinders were cured for 14 days and then tested.
2) The compressive strength of the cubes was found to be 19.11 N/mm2 on average, while the cylinders was 14.71 N/mm2. The ratio of 0.8 between cylinder and cube strengths was as expected.
3) The tensile strength was found to be 2.05 N/mm2, which is approximately 10% of the compressive strength of the cubes, showing that concrete is weaker in tension.
Pullout test as nondestructive test method in structural engineeringMohammed Layth
1. The pullout test measures the force required to pull an embedded metal insert from hardened concrete. It was first described in 1938 and research in the 1960s aimed to optimize the geometry and develop simple field equipment with high correlation to compressive strength.
2. An embedment depth of 50mm was chosen as it tests beyond the surface while not requiring too much force. Tests established the optimal insert head and bearing ring diameters. Failure involves cracking around the insert and aggregate interlock up to the ultimate load.
3. For field use, a 25mm diameter steel disc on a conical stem is embedded and pulled against a reaction ring using a hydraulic jack, measuring the force. The test estimates concrete strength to determine
This document discusses a study on the influence of particle size gradation on shear parameters for cohesionless soil. Laboratory direct shear tests were performed on sand samples with different particle size gradations (coarse, medium, fine mixes) and relative densities (30-90%). The results showed that the angle of internal friction increased with increasing particle size and relative density. Specifically, samples with coarser grains had internal friction angles ranging from 36-42 degrees, while finer grained samples ranged from 28-34 degrees. The shear strength parameters were thus found to depend on both the particle size gradation and relative density of the cohesionless soil samples.
This document summarizes a laboratory testing program that investigated the time-dependent differential consolidation of slurry wall backfill material. Large-scale consolidation tests were performed on samples from an 11,000 m long, over 45 m deep slurry wall installed through glacial till. The results showed significant retardation of vertical stress in the backfill due to arching effects. Narrower trench widths led to greater loss of vertical effective stress. Differential consolidation around multiple aquifers crossed by the wall could increase due to the loss of vertical stress, potentially creating more permeable zones.
This document summarizes research on the tensile characteristics of no aggregate concrete. Testing found that no aggregate concrete has lower tensile strength than normal concrete, around 5-6% of its compressive strength compared to 10% for normal concrete. Replacing some fly ash with cement can increase tensile strength of no aggregate concrete. Density is also lower than normal concrete and decreases over time. The elastic modulus of no aggregate concrete is around 11 GPa compared to 26 GPa for normal concrete, and it exhibits more brittleness. Increasing cement content or decreasing fly ash content can respectively increase or decrease tensile strength. While no aggregate concrete has benefits, full replacement of aggregates is not recommended.
This document presents research on the compressive strength of bamboo leaf ash (BLA) blended cement concrete cured in different sulphate environments. Concrete cubes with 0%, 5%, 10%, and 15% replacement of cement with BLA were cured in water and sulphate solutions of varying concentrations for 21 and 28 days. Testing found that BLA concrete strengths generally increased with higher sulphate concentrations and longer curing times compared to plain cement concrete. Replacement of 10% cement with BLA produced the highest strengths. The results indicate BLA concrete has improved sulphate resistance and could be suitable for use in sulphate environments where early strength is not critical.
1. The document discusses Karl Terzaghi's principle of effective stress, which states that the stress on a soil is equal to the total stress minus the pore water pressure.
2. It then provides objectives and scope for a case study on evaluating Terzaghi's theory through consolidation tests. Materials used include remolded soil samples from various locations.
3. The document outlines Terzaghi's assumptions for his consolidation theory and provides his equations for calculating bearing capacity of strip, square, and circular footings. It also briefly reviews several literature sources analyzing consolidation and settlement prediction.
Pullout test as a nondestructive test method in structural engineering Ahmed Abdullah
- The pullout test measures the force required to pull an embedded metal insert from hardened concrete. It has been shown to have good correlation with compressive strength.
- The failure mechanism involves initial cracking around the insert followed by the development of microcracks between the insert and bearing ring. Beyond ultimate load, a circumferential crack forms extracting the failure cone.
- Within-test variability, or repeatability, of pullout tests on the same concrete is typically a coefficient of variation of 4-15%, with an average of 8%. The size of coarse aggregate affects variability.
Three series of push-off tests were conducted to study subbase friction characteristics for typical Korean jointed concrete pavement systems under different subbase conditions. The subbase conditions tested were: I) concrete slab directly cast on lean concrete subbase, II) polythene sheet placed between slab and subbase, and III) asphalt bond breaker layer between slab and subbase. Tests were performed at various loading rates and slab thicknesses to evaluate how these factors influence subbase friction properties. Results showed that subbase type and stiffness affected the failure plane location and shape of the friction-displacement curve. Softer subbases led to failure at the slab-subbase interface and a decreasing friction curve, while stiffer subbases
This document summarizes a study on the influence of curing regime on the strength development of grade C60 concrete. Concrete cubes were cured in water or ambient air and tested at various ages to determine compressive strength. Additional cubes were water cured for limited durations and then stored in air, and tested at 28 and 90 days. The results showed that cubes water cured for only 3 days reached the highest 28-day strength of 74.15N/mm2, while cubes water cured for 28 days reached the highest 90-day strength of 77.58N/mm2. Sorptivity and water absorption tests also indicated improved pore structure and reduced permeability with increased water curing duration.
1. The document compares static and dynamic (seismic) earth pressures behind retaining walls using different soil types as backfill material.
2. Laboratory tests were conducted on three soil types - soft murrum, hard murrum, and black cotton soil - to determine their engineering properties. Earth pressures were then calculated using various static and dynamic methods.
3. The results found that the Mononobe-Okabe method yielded the highest dynamic earth pressures of the methods studied. Static earth pressures from the Coulomb method were the lowest. The percentage increase in pressure from static to dynamic conditions ranged from 9.35-10.66% for the different soil types.
The document summarizes research on stress distribution in soils under the pile cap of tapered piles in compressible clay. Laboratory tests were conducted using modeled tapered piles in compressible clay from Belarus. Field tests measured stresses in soils at different depths under loaded pile caps connected to instrumented tapered piles installed in compressible clay. Results found stresses slightly higher than calculated using Boussinesq's theory. Stresses increased towards pile centers and with depth, and were directed along radius vectors from pile centers. Stresses decreased radially outward from pile centers and with increased pile spacing. Stress distribution was also affected by pile spacing and tapering angle. Clearly delineated stressed zones of soil deformation were observed under loaded pile caps.
This document discusses the shear strength of soils. It begins with an abstract describing shear strength and factors that influence it, such as particle interactions and stresses. It then outlines different methods to measure shear strength in the laboratory and field, including direct shear tests, triaxial shear tests, and vane shear tests. The Mohr-Coulomb failure criteria is also explained as a way to analyze shear strength based on normal and shear stresses. Key parameters that govern shear strength are identified as cohesion and the friction angle.
This document describes a study that investigated the relationship between porosity and compressive strength of concrete with varying water-to-cement (w/c) ratios over time. Concrete cylinders were made with w/c ratios of 0.40, 0.55, and 0.70 and tested for compressive strength and porosity at various ages up to 56 days. The results showed that as curing time increased, compressive strength increased while porosity decreased. A direct correlation was observed between porosity and compressive strength. Understanding how the pore structure of hardening concrete changes over time provides insights into concrete quality and performance.
1. The document examines the use of Tunnel Stability Factor (TSF) to estimate convergence and face stability in weak rock tunnels. TSF considers rock mass strength, overburden height, and tunnel size.
2. Parametric numerical analyses were conducted on 74 tunnels varying in size, depth, and rock mass quality. Dimensionless plots of plastic zone radius and convergence vs TSF showed good correlation despite varying conditions.
3. Guidelines for criticality of stability were developed based on convergence-to-radius ratio ranges associated with TSF levels, indicating severe squeezing for TSF < 0.2 and increased risk of collapse below 0.3 without support.
The document discusses soil mechanics topics related to consolidation and settlement. It covers three types of settlement (immediate, primary consolidation, and secondary consolidation). It also explains the fundamental concept of consolidation using a piston-spring model and describes how a one-dimensional consolidation test (oedometer test) is conducted in the laboratory to determine soil compressibility.
Introduction.
Some definitions.
Mohr circle of stress.
Mohr-coulomb’s strength theory.
Tests for shear strength.
Shear tests based on drainage conditions.
This test measures the compressive strength of concrete cubes made and cured according to specific standards. It provides a measure of quality control by testing one property, compressive strength, but results can vary depending on test conditions like specimen size and loading rate. The document outlines how to conduct compression tests on concrete cubes to determine if the concrete meets design specifications. Cubes are made, cured, weighed, and tested for compressive strength at various ages to see how strength develops over time. Detailed procedures are provided for casting, curing, operating the compression machine, and analyzing results.
REINFORCED CONCRETE STRUCTURE CHAPTER ONE GENERAL INTRODUCTION
final 1211 Suzuki 1109 final 4484 CR658-1
1. Peak and Residual Strength Characteristics of Cement-Ttreated Soil Samples That Were Cured
under Different Consolidation Conditions
1. Introduction
Because high strength appears within a short period in Gsuch ground that was has been soliildified with cement-base
solidification material acquires strength quickly, so consolidation and strength, which increase along with solidificationit,
are not commonly known commonly and are not reflected to in the design of ground improvements. However, soil
elements are receiveing confining pressure even in cement-treated ground, so it can be considered that consolidation occurs
in the initial stage of construction before consolidation starts and that the undrained shear strength will increase. In the current
method for edvaluating the strength of cement-treasted soil, the influence of the type and state of the soil, the type and
dosage of the stabilizer, and the material age are understood considerably quite welll.deeply; Hhowever, the influence of
overrburden pressure improsed in stute situ after construction is unknown??ignored??.
The authoers examined the unconfined compressive strength of cement-treated soil that was cured in the a state of single-
dimentisonal dimensional consolidation using consolidation and curing equipment that employsuses a split mold as the
consolidation vessel 1)~3). As a result, theyit was clarified that the unconfined compressive strength increases due tounder
the influence of the consolidation pressure applied to the cement-treated soil sample. An Iincrease in density due to
consolidation during the initial material -aginge period before solidification started was detected and, due to the synergetic
effect of it this with the progress of cementation, the strength and deformation characteristics to be exhibited later differ
remarkably from those obtained from curing under the atmospheric pressure.; Iin other words, it was thus found that
solidifying soil exhibitsin the middle of solidification shows the an increased in shear strength due to both actions, an
increased in density thrrhough consolidation, and development of cementation through cement hydration. However, there
were such problems in the experiment that because the shear test is an unconfined compression test, the state of stress and
deformation of the specimen differs from that in the original position, and that the confining pressure was once removed
inat the time of transition from the consolidation process to the shear process1)~3).
In conventional studies as well, tThe shear strength, and the deformation, characteristics and the single-dimensional
compression characteristics of cement-treated soil samples subjected tounder the condition that confining pressure was
applied during curing are have been investigated in conventional studies as well (e.g., Kobayashi & Tatsuoka, Cosoli et
al., and others). In these studies, the a soil sample was left atalone under the atmospheric pressure or submerged under
water for several hours or several days after it was cement-treatmented until before it was exposed to confining pressure, so
it is necessary to considerpay attention to the fact that cement hydration was in progress within the state where no confining
pressure is was applied. TConcerning this fact, the authors investigated the changes in the unconfined compression strength
whenin the case where loading of overburden pressure on cement-treated soil is delayed using the above- mentioned mold-
type consolidated curing equipment, . Theyand aAs a result, it was found that the values of consoliikdiation settlement
and unconfined compression strength decrease with an increase in the delayed loading of overbuyrden pressure, and
ultimately, they gradually approaching to the vluaes values at the time ofseen with curing under the atmospheric pressure
(Suzuki et al., 2002). This result suggests that the time course after solidification may causeinduce underesttimation of the
shear strength of cement-treated soil to be underestimated. However, whether this effect of delayed loading time applies
similarly toalso appears operates in the same manner on the shear strength exhibited under the action of confining pressure
in the a triaxial compression test has not yet been verified.
On the other handIn contrast, while in-situ cement-treated soil is cured under thein a single-dimensional consolidated state, it
is not alnways clarified by conventional studies have not clarifiedas to how the influence of the differences between the
single-dimensional consolidated state and the isotropic consolidated state influencesappears in the consolidation
characteristics and subsequent strength characteristics of cement-trreated soil when it is cured in a single-dimensional state
(Ghee et al., 2004). Moremover, past exammainations with the unconfined compression tests mainly focusted on
evaluatingon of the peak strength, and did not examineations are have been conducted at all about the influence of
consolidation stress during curing on the residual strength, of which examination is necessary for to study the fealurefailure
of burnerable materials.
In this study, based on the present status as mentioned discussed above, we implemented the an unconfined compresstion
test and a consolidated undrained triaxial test on single-dimenstionally consolidated and isotropically consolidated cement-
treated soil sample based on the above statuss, respectively, and examined mainly three itmes as followsthe following,
based on the test results: 1) influence of the difference in consolidation state during curing on the consolidation and shear
characteristics in the case of cement-treated soil withwhere cementation is in progress, 2) the consolidation and undrained
shear characteristics of cement-treated soil in the case whenre application of isotropic consolidation stress is delayed in the
triaxial test, and 3) the effect of consolidation stress during curing on the residual strength of the cement-treated soil. These
1
2. test results are and a discussedtion are described presented in the following sections.
2. Changes in stress state of cement-treated soil in the a laboratory test
Figure. 1 depicts the changes with time in the vertical stress σv that acts on the specimen immediately after solidification in
the a laboratory test 4). Because in-situ soil elements are steered stirred and mixed during construction, it can be considered
that the effective stress is initially zero and then increases up to the full vertical stress σv as consolidation progresses. In the
case of the current laboratory mixing test (an unconfined compression test), while the curing time Tc elapses as indicated by
path OABD in Fig. 1, but σv scarcely acts and the in-situ stress state is not reproduced. Therefore, Yamamoto et al. (2000)
conducimplemented the an unconfined compression test on the a cement-treated soil sample that was curred while being
consolidateding onsingle- dimensionally using a mold-type consolidated curing equipment. Based on the result, they
demonstrtatshowed that the settlement distortsion, (εv), the unconfined compression strength, (qu), and the deformation
modulus, (E50), all increase with an increase in σv. In this test, however, because the overburden pressure is was
removed when removing the specimen was removed from the mold after curing for a specified period, as indicated by path
OCBD in Fig. 1, so there was nooa transition to undrained shear while keeping maintaining the pressure was
maintainedstate during consolidation does not occur. TIn this study, to solve this problem, we cured the a specimen that
was immediately after solidification while subjecting it to isotropic consolidation using triaxial omplesion compression test
equipment and then implemented the undrained shear test. I Here, in the case of conventional triaxial compression tests
(e.g., Cobayashi & Tatsuoka), attention must be paid to ensurethe fact that the cement-treated soil sample is consolidated after
being left alone for a certain period (the delayed loading time ΔT, represented by segment OA) under the atmospheric
pressure or under water after being cement-treated as in path OACD in Fig. 1. The purpose of the triaxial compression test
implemented in this study soughtis was to obtain the undrained shear strength of cement-treated soil that was cured while
being consolidated immediately after being cement-treated as in path OACD in Fig. 1.
Figures. 2(a) and (b) schematically depict the difference in the stress states in during the consolidation process of the
specimens used in the unconfined compression test and triaxial compression test, respectively, and along with Mohr’s stress
circles of for the specimens in the consolidation and shear processes. IFirst, in the consolidation process, while the stress
state of the unconfined compression testis is represented by a stress circle with a diameter of (σc,0), (K0σc,0), and the stress
state of the triaxial compression test is represented by a point of (σc,0). ISecond, in the shear process, because the confining
pressure on the specimen of from the unconfined compression test has once beenis removed before the shear process, so
its Mohr’s stress circle passes through the ??datpum?? point.T; on the other handmeanwhile, because the specimen of
from the triaxial compression test transits to the shear process while keeing maintaining the same stress state as in the
consolidation process, so its Mohr’s stress circle passes through (σc,0). On the other handWe note that, the shear strength
ratio due to consolidation, ΔSu/ΔP, is the gradient of the approximation straight- line approximation of the radius of the
Mohr’s stress circle at the time of failure. TIn this study, we will also discuss the difference in ΔSu/ΔP between the
isotropic consolidation and onainflesingle-dimensional consolidation.
3. Test Method
(1) Soil sample and solidification agent
The soil sample used is was fine-grained quality divided sand mixed with stone that was collected in Yamaguchi City,
Yamaguchi Prefecture (soil particle density of soil particle: :ρs=2.693 g/cm3, maximum grain size: Dmax=4.75 mm,
natural water content: wn=16.3 %, fine fraction content: Fc=18.9 %, maximum void ratioo: emax=1.308,
minimum void ratio: emin=0.697, apparent cohesion: c'=0 kPa, and internal friction angloe: φ'=35.5 °). The
solidification agent used was ordinary Portland cement (OPC) mixedand the dosage was set to a constant 50 kg/m3
constatlty. The procedure used to mix the soil sample and solidification agent complied with the “pPreparation method
for unconsolidated samples of stabilized soil” in JGS0821-2009, and the solidification agent was added in the form of
slurry (water/agent ratio=160%).The initial water content of the cement-treated soil, w0, was 20.7 % and no separation of
materials was detected at the time when the specimen was preapared.
(2) Consolidated undrained triaxial compression test
This test uses medium-sized triaxial compressiton test equipment of with a hydraulic control system and complies with the
“cConsoldidated undrained triaxial compression test method for soil” in JGS0522-2009. In this test, saturation of the
sample was limited to the load of back pressure (uBP=49 kPa) to minimizemake the time until before the start of
consolidation of the specimen as shorther as possible. and tThe time from solidificaction to the start of consolidation was
set to a constant 50 min, constantly. The test procedures are as described briefly in the following. i) Stieer and mix the soil
sample and a solidificaction agent made in the form of slurry with de-aired water for 10 min using a Hovert mixer. ii) Put
1
3. cement-treated soil into the split mold (dia.: 50 mm, height: 100 mm). RIn this case, remove bubbles by tapping the mold.
iii) Smooth the top face of the specimen with a knife. T In this test, because the time until before specimen consolidation of
the specimen is limited, socapping, etc., on the end faces of the specimen are not capped with gypsum is not implemented.
iv) Take outRemove the specimen from the mold, place it on the a pedestal, and assemble the triaxial cell chamber. IBy the
way, it was possible to prepare a self-standing specimen for this sample. v) Start consolidation by applyloading the side and
back pressures so that the specified consolidation pressure is achieved. TIn this case, the drainage conditrion was set to single
drainage only from the top. vi) After consolidationng curing for the timea certain period as specified in Table 1, perform the
shear at an axial strain rate of 0.05 %/min onunder the undrained specimencondition.A In this test, an external
displacement meter was used in this test tofor measurement of the axial strain. Shear was ended at the time when the axial
strain showed that shows the maximum deviator stress was exceeded by 3%. AFurthermore, it was confirmed that a clear
slip line appeared on the specimen at the time when the test was stopped.
(3) Unconfined compression test
A specimen of cement-treated soil was cured while being consolidateding onsinggnle-dimensionally using the mold-
type consolidationng curing equipmewnt that the authoers developed. After the specified consolidation, we conducted the
an uncondefined comprlession test on this the specimen. The specimen had a diameter of 50 mm and a height of 100
mm, and shearing was performed at an axial strain rate of 1.0 %/min. For other details of the test method, refer to
Yamamoto et al. (2000). TIn this case, the unconfined compression test was conducted atunder the constant
-temperature and constant -humidity conditions (temperature: 20 ℃ and relative humidity: 95 %).
(4) Test cases
Table 1 and Table 2 show summarizes the test cases and test results for the triaxial compression test, and Table 2
summarizes those for the uncopnfined compression test, respectively. To examine the influence of consolidation pressure
(isotropic consolidation pressure σr0 in the triaxial compressiton test,: or vertical consolidation pressure σv in the unconfined
compression test), the value of σr0=σv was changed intoset to three cases of 49, 98, and 147 kPa by setting the
delayed loading time ΔT to 0 min and the curing time Tc to 1, 3, and 7 days.; Tto examine the effect of ΔT, the value
of ΔT was changed into four cases ofset to 0, 60, 120, and 240 min by setting σr0=σv=147 kPa and Tc=3 days. IBy the
way, Aamong the symbols shown in the tables, ws denotes the water content of the specimen after being subjected to shear
in the triaxial compression test and wc and ρtc denote the water content and wet density of the specimen after being subjected
to consolidatedion in the unconfined compression test.
4. Test Results and Discussions
(1) OneSingle-dimensional and isotropic consolidation behavior of cement-treated soil
This section describes the influence of differences in the consolidated state during curing on consolidation behavior. Figure.
3 depicts the changes with time in the volumetric strains, εvU and εvT, in during the consolidation process under with
different values of overburden pressures, (σv), and isotropic pressures, (σr0). SHere, subscriptts U and T mean
represents the onsingle-dimensionally consolidated and isotropically consolidated strain states that the specimens that are
used receive in the unconfined test; subscript Tand represents those for the triaxial test receive, respectively.εvU and εvT
are percentages expressions of the quotients obtained by dividing the volumetric variation during consolidation, ΔV, by the
volume of the specimen in the initial stage, V0. However, εvU, εvT, and ΔV arhave positive values when representing
conmtraction and drainage, respectively. The test conditions at this time are delayed loading delay ΔT=0 min and curing
time Tc=3 days. Figure. 3 indicates that the volumetric strain increases with the progress of the time regardless of the stress
state in during the consolidation process and becomes roughly constant around t=100 min for onin the case of single-
dimensional consolidation or within the a range of t=200 to 2000min forin the case of isotropic consolidation. TIt can be
considered that this difference is due tocomes from the difference in drainage distance between specimens. On the other
handStill, such aa separate trend can be observed that in which the volumetric strain tended to increases with increasinge
in consolidation pressure regardless of the consolidating conditions. Furruthermore, the volumetric strain in isotropic
consolidation exceedsis larger than that in onsingle-dimensional consolidation. TIt can be considered that this is
influenced by the fact that the mean effective principlea stress in the isotropic consolidation exceedsis larger than that in
onsingle-dimensional consolidation. Figure. 4 depicts the relationships between the ultimate volumetric strain, εvU*, εvT,
and the curing time, Tc. Because the volumetric variation due to consolidation becomes roughly constant within the range
of 100 to 2000 min and the value of εvU*, and εvT* becomes roughly constant under the same consolidation pressure
1
4. even with increasing Tc as described above, the influence of the change in density at an early material age is heldremains
after the curing time has elapsed regardless of the stress state of the specimen in the consolidation process.
/////
(2) Shear behavior of cement-treated soil samples cured under different consolidation condittiions
This section describes the influence of differences in the consolidation state on shear behavior. Figures. 5(a) to (c) depict the
results of both the unconfined compression and triaxial compression tests in the case where the curing time, Tc, differs. The
vertical axis of the grapth represents the deviator stress, q(=σa-σr); the horizontal axis represents the, axial strain, εa.; σr ,is
the confining pressure; and σc, is the consolidation pressure. In the case of Tc=1 day in Fig. 5(a), q in the triaxial
compression tends to increase monotonously with increasinge in εa and to decrease slightly after passing the peask strength,
qmax.On the other handIn contrast, q in the unconfined compression shows qmax around εa=1% and then decreases. The
value of qmax becoocmes larger with in creasinge in consolidation pressure regardless of whetherin both the uncinfied
unconfined and or triaxial compression test. Furthermore, generally speaking, qmax is larger in the triaxial compressuion
test than in the unconfined compression test.This result is caused by the difference in the stress states of the specimens in
the consolidation process. While the value of the failure strain, εf, is larger in the triaxial comperession test than in the
unconfined compression test, the trend of strain softening is more remarkable in the unconfined compression test. As a
reason, it is possible thatThis may be due to the influences of the axial strain rate as or the presence or absence of confining
pressure in the shear process. In this case, generally speaking, the initial rigidity (i.e., the initial tangent gradient of the q-εa
curve) is larger in the triaxial compression test than in the unconfined compression test. In the case of Tc=3 and 7 days as
shownseen in Figs. 5(b) and (c), respectively, the q-εa curve shows more a remarkable trend of vulnerability with increase
in Tc while the initial rigidity is high and εf is small in both in the unconfined and triaxial compression tests. On the other
handIn contrast, differences in the size of consolidation pressure with increases in Tc appear clearly on the q-εa curve and in
the case of Tc=7 days, qmax of the triaxial compression test increases from 1.3MPa to 2.1MPa and that of the unconfined
compression test increases from 1.0MPa to 1.3MPa while the consolidation pressure increases from 49kPa to 147kPa.
Moreover, it can be seen from the same figure that qres corresponding to approx. imately 80% of qma is remainsing at the
end of the shear in the triaxial compression test.
(3) Strength- increasinge characteristics by with consolidation under different consolidation conditions
Figures. 6(a) to (c) depict Mohr’s total stress circles at the time of faitlure in the triaxial cxompression test and unconfined
compression test. These figures are were prepared according to each curing time, and the result of the triaxial compression
test accompanies the strength parameters in terms of total stress, ccu, φcu, as determined from Mohr-Coulomb’s failure
criterion. Here, while the strength parameters in terms of the effective stress of the soil sample (untreated soil) used in this
study are cd=0 kN/m2 and φd=35.5 °as mentioned above, it is necessary to pay attention to the factnote that strength
parameters are handled in terms of total stress are handled in this section. In the case of Tc=1 day as shown in Fig. 6(a),
when faeilure lines are determined from three Mohr’s stress circles with different consolidation pressures, the values of
ccu=145.6 kP and φcu=39.0 ° can be obtained. The shear strength ratio was estimated from the relationship between the
consolidating pressure and the undrained shear strength, SuT,SuU. Here, the undrained shear strengths in the unconfined
compression and triaxial comprlession tests are denoted by SuT and SuU (=qmax/2), respectively. As a result, the shear strength
ratio in the triaxial compression test is ΔSuT/ΔP=1.36 while that in the unconfined compression test is ΔSuU/ΔP=0.8, so the
shear strength ratio is larger in the triaxial compression test than in the unconfined compression test. This was is the same
also in the case of Tc=3 and 7 days as depicted in Figs. 6(b) and (c). Figure. 7 shows plots the relationship between
ΔSuT/ΔP, ΔSuU/ΔP, and Tc. Such aA trend can be observed that in which the shear strength ratio obtained from both the
unconfined compression and treiaxial compression tests increases with increasinge in the curing time. This indicatesd that
the volumetric variation in the consolidation process in Fig. 4 is roughly constant regardless of the curing time. Thus, the
void ratio of the specimen before shear is constant regardless of the curing time, so it can be considered that this the change in
shear strength ratio is not caused by the increase in density due to consolidation but rather is caused in the development of
cementation with the elapse passage of curing time. Figure. 8 depicts the relationship between the strength parameters in
terms of total stress, ccu, φcu, and Tc. Such aA trend can be observed that in which the internal friction angle, φcu, increases
with an increase in Tc while the value of apparent cohesion, ccu, is keptremains roughly constant. This result suggests that
the strength parameters of the soil themselves (including those in terms of effective stress) may have changed essentially
with the increase in curing time. As a reason for this, it can be conjectured that because the soil sample mainly consists of
coarse-grained aggregate, the hydration product is relatively smaller in size than the soil grain, so cementation is formed on
the surface of soil particles rather than bonding the soil particles, and as a result, the roughness and friction characteristiitcs on
of the surface of the soil particles change, which in turn changes the shear strength characteristicitcs changed.
1
5. (4) Influence of the difference in stress state of the specimens in the consolidation process on the peak strength
This section describes the influence of the stress states of the specimens in the consolidation process on the undrained shear
strength. Figure. 9 depicts the relationship between the undrained shear strengths in the triaxctial compression test and the
unconfined compression test, SuT, SuU. A proportionality between SuT and SuU also with a gradient of 1.5 can be
recognized. The same figure shows data quoted from past study results (Ghee et al., 2005). Although the methods for
improving soil and cement differ, it was confirmed that the undrained shear strength of cement-treated soil differs depending
on the consolidation condition during curing. To explore the cause of itthis, we examined the difference between theh
volumetric variations in the unconfined consolidation and that in the triaxial consoliddiation. Figure. 10 depicts the
relationship between the ultimate volumetric strains in the isotropic consolidation and the single-dimensional consolidation,
εvT* and εvU*. A linear relationship was recognized between both valiesthese, except for some dispersion, and it can be
seen that the ultimate volumentric strain under the isotropic consolidation condition is approximately. 1.5 times as large as
that under the single-dimensional consolidation condition. The gradients of the linear relationships were roughly the same
in both aspectwith respect to thes of strength and the density of the specimen. From these results, it can be considered that
the difference in stress state during the consolidation process give has the same level of influence on the ratios of the
consolidation amount and the undrained shear strength.
(5) Influeneuce of delayed loading time on undrained shear strength
This section describes the influence of delayed loading time, ΔT, on the undrained shear strength. As described previously,
delayed loading time can be said defined as the exposure time before application of confining pressure to cement-treated soil,
while during which cementation develops in the cement-treated soil. Such aA trend was clarified by Yamamoto et al.
(2000) that in which the volumentric variation due to overburden pressure dsecreaseds with increases in the delayed
loading time, ΔT, in the single-dimensional consolidation state and then unconfined compression strength, qu, also
decreaseds in the an unconfined pressure test implemented thereafter. However, as described previously, whether or not
this result is also correct under the insotropic consolidation in the triaxial compression test or not has not yet been
verifieddetermined. This means that confining pressure applied after cementation has developed does not cause any
significant change in density in the a specimen of cement-treated soil and, therefore, does not contribute to the any increase
in strength. Figure. 11(a) depicts the relationship between the ultimpate volumetric strain, εvT*,εvU*, and ΔT in the
consolidation process. On the other hand, Figures. 12(a) and (b) depict the relationships between the stress and strain
curves and ΔT as well as the peak strength, qmax, and ΔT, respectively, for different values of ΔT. The ultimate
volumetric strain decreases with increases in the delayed loading time. Furthermore, qmax also decreases with increases in
ΔT and ultimately guraduaalygradually approaches the value of the a specimen of cement-treated soil that was curred in
the a state of unconfined pressure, where no volumetric variation occurs. From the result at this time, it was found that the
undrained shear strength does not increase, even in the state of isotropic consolidation, if the time until before application of
confining prerssure is prolonged. In other words, if the time after solidification until but before application of consolidation
pressure is prolonged, no increase in density occurs in the specimen if consolidation pressure is applied to it, and no
subsequent increase in undrained shear strength will occur. In that case, therefore, it can be considered that it is highly
probable that the undrained shear strength of cement-treated soil is underestimated.
(6) Influence of consolidation stress during curinjg on residual strength
As described previously, in the case of the stabilization of stiff ground, evaluation of residual strength rather than the peak
strength is more important to when considering brittle fracture. Figure. 13 depicts the relationship between the residual
strength, qres, and the initial effective confining pressure, σr0’. Here, for the purpose of evaluating the sterength after the a
brittle fracture in stiff ground materiasl, such as stabilizsed soil, we defined qres in this study as the value of the deviator
stress at the time of stopping the shear test, as described above. At each value of Tc, qres becomes larger with increases in
σr0’. On the othe handIn contrast, qres becomes larger with increases in Tc regardless of the magnitude of σr0’. From this
result, it can be said that the influence of consolidation during curing also appears in the shear strength in the residual state.
Although no clear differences in consolidation pressure during curing were detected in the value of q in the residual state in the
single-dimensional compression test as shown in Fig. 5, it can be considered that this is because the confining pressure did
not act. It was confirmed that a certain level of shear strength is remainsing even in the residual state under the action of
confining pressure.
5.Conclusions
In this study, we examined the undrained shear strength of cement-treated soil samples that were cured in the isontropic
1
6. consolidation and single-dimensional consolidation states. The Ffindings obtained are as follows:
(1) The undrained shear strength of the a cement-treated soil sample that was cured in the isotropic consolidation state
increases with increases in consolidation pressure, as in the single-dimensional consolidation state.
(2) The rate of increase in the undrained shear strength due to consolidation differs between the isotropic consolidation state
and the single-dimensional consolidation state. Within the range of curing time of one1 to seven7 days, the rate of
increase in strength in the isotropic consolidation state is larger than that in the single-dimensional consolidation state.
(3) The volumetric variation of cement-treated soil during the consolidation process depends on the stress state of the
specimen, and the volumetric variation in the isotropic consolidation state was aprrox.approximately 1.5 times as large
as that in the single-dimensional consolidation state. Furthermore, the same trend was recognized in the undrained
shear strength. As a reason for itthis, it can be said that the difference in the stress state during consolidation give had the
same level of influence to on the ratios of the consolidation amount and the undrained shear strength.
(4) When the time of loading of confining pressure is delayeds, the volumetric variation during consolidation decreases.
This is true regardless of the stress strate in during the consolidation process. When the loading of confining
pressure is delayeds, the undrained shear strengtrh decreases in the triaxial compression test decreases as it does in the
unconfined compression test and ultimately gradually approaches to the value of cement-treated soil that was cured
without applying confining pressure.
(5) For the above reason, if the test is conducted in a nearly in-situ stress state, the undrained shear strength may be
underestimated, depending on the time from cement treatment to consolidation of the specimen.
(6) It has been clarified that the shear strength in the residual state will be influenced by the state of consolidation during
curing. The larger the consolidation pressure during curing, the larger the residual strength.
End
1