CHENNAI METRO RAIL PROJECT ECV-02 /03<br />WORK METHOD STATEMENT<br />PROCEDURE FOR SOIL INVESTIGATION-WMS-2<br />DISCIPLINECivilMechanicalElectricalGeneral<br />ContactDocument controlNAME: S.BalajiSoil InvestigationQMS/D/CMP/WMS- 2ATel:09600091870Action RequiredEmail:firstname.lastname@example.orgFor informationFor Approval<br />Preparation & IssueNamePositionSignatureDatePrepared byS.KavinkumarPlanning ManagerReviewed byK.NarasimhanConstruction ManagerApproved byS.BalajiProject ManagerThis submission is considered ready for review and complies with contract other than stated herewith.Approved by(GCC)<br />This document consists of 11 pages including this page<br />CONTENTS<br />Sl No.ContentPage no.01Preamble302Scope of work303Laboratory Tests704Reports11<br />1. Preamble<br /> The object of this Method Statement is to lay down a procedure for soil investigation works of the Project. <br />Introduction<br /> Geotechnical investigations are required to evolve various soil/rock parameters at the proposed project location in order to carry out engineering analysis. Broad objectives of the investigations are as follows.<br />To evaluate geo-technical parameters of soil/rock at the proposed borehole locations.<br />To assess the engineering parameters and to estimate bearing capacity of soil.<br />To recommend suitable foundation systems.<br />To evaluate the aggressiveness of soil due to chemical content in the deposits.<br />To measure the effect of groundwater on steel and other materials and draw up recommendations for preventive measures.<br />2. Scope of Work<br />The scope of work includes the following.<br />
Boring / Drilling shall be done at an average spacing of 100 m along the project alignment.
Conducting standard penetration tests at 1.5m interval or at every identifiable change of strata, whichever is met earlier.
Conducting the Vane Shear Test (VST) in soft clay.
Collection of both disturbed and undisturbed soil samples and rock cores and carrying out the entire relevant laboratory tests on soils and rock cores as mentioned in the subsequent section.
Submitting a detailed report on soil investigations including the design soil parameters for the various locations and to the complete satisfaction of GC.
Location of Boreholes<br /> The exact location of boreholes shall be obtained from the topographical survey data and the chainage /coordinates will be intimated to Engineer’s representative once the location is mutually agreed after joint inspection. The sequence of work shall be decided jointly based on the land handing over schedule and the approval from the concerned Government departments. Three nos. of rigs for ECV-02 and 3nos for ECV-03 will be deployed to complete the desired no. of boreholes (Approximately 100nos). Sketches showing the location of boreholes shall be submitted separately. Tentatively 8 weeks is planned to complete the works at site. <br />Safety Measures<br /> All safety measures will be followed strictly during working. Following shall be taken care. <br />Barricading the location (at median), the safety of men and equipment for an area of 8m x 8m.<br />Before to start the drilling, the location of hole shall be probed with a “Cable and Pipe Detector” to ensure that no electrical cables and pipelines run below.<br />Only experienced operators and workers shall be working at site.<br />All men working at site shall be provided with the following<br />
The drilling machineries proposed to mobilize shall be in good condition and shall be to the standard laid down in contract conditions. All rotating parts of the machineries shall be guarded properly. Locations and parts where the dust particles fly shall be covered to protect the work men. The machinery not complying to the safety standards will be removed from site if it is not to the satisfaction of GC.<br />Drinking water in sufficient quantity shall be available at working place. <br />A first Aid Box shall always be available at site.<br />It is intended to drill during day light only and incase if the drilling is continued at Night, necessary lighting arrangements shall be made at work place. Two halogen lights (battery operated) will be provided at respective locations. <br />2. Boring and Rock coring<br />Boring in Soil<br /> Boring shall be carried out in accordance with the provisions of IS 1892:1979. Minimum diameter of boring shall be 150 mm. Auger boring shall be resorted to above the water table, whereas below the water table the boreholes shall be advanced by rotary drilling with mud circulation through all kinds of soils other than rock. While boring above water table, no water shall be introduced in the boreholes. Casing if required shall be used to support the sides of boreholes in soft to loose soils. Water table in the borehole shall be carefully recorded as per the IS 6935 – 1973 and reported as per the guidelines given in IS 1892- 1979.<br /> Use of chisel and percussion boring shall be permitted exclusively in strata having N (SPT) value greater than 100 per 30 cm of penetration.<br /> The contractor shall take care while using shell and auger casing and attachments to avoid fracturing or otherwise disturbing the rock at the interface between soil and rock / weathered rock, such that the true level of the surface of rock / weathered rock and its true in-situ quality are identifiable.<br />Boring in Rock<br />Drilling in rock shall be done as per IS 6926. If the rate of advancement of boring by chiselling is slow (i.e. less than 20 cm in 4 hrs), the contractor may be permitted to adopt core drilling with NX size Tungsten Carbide (TC) bit. When Core Recovery (CR) with TC bit is less than 10% the material will be treated as soil.<br />If rate of penetration with TC bit is in the order of 15 cm/ Hour or less, then TC bit can be changed to diamond bit. <br />The rotational speed of the bit (spindle speed) the amount of downward pressure applied on the bit (bit pressure) and water pressure shall be suitably adjusted and properly monitored so that the core is collected with least disturbance and avoid shearing of the Core from its base. Bit speed, bit pressure, water pressure for the type of bit for various rocks types shall be as given in IS: 6926.<br />In sound rock maximum length of drilling run shall be restricted to 1.0 m. This may be increased to 1.5 m provided the core recovery is observed more than 80% in two successive drill runs and on approval from project engineer. Double tube core barrel shall be used for coring. Suitable core catchers shall be used to ensure continuous and good core recovery.<br />The contractor shall ensure that the equipment used for drilling, sampling etc. shall have an adequate capacity to drill boreholes up to specified depth.<br /> <br />Once the core has been cut and the core barrel is full, the drill rods or overshot assembly are pulled and the core retrieved. <br />Termination criteria for Boreholes:-<br />The boreholes shall be terminated as per following criteria, whichever occurs earlier.<br />a) When the depth of drilling reaches 40.0m.<br />b) When tungsten bit drilling in weak rock (stratum where RQD <50% or CR <75%) reaches 15.0m depth <br />c) When diamond bit drilling in sound rock (stratum where RQD>50% or CR >75%) reaches 3.0m depth.<br />If a very hard stratum is met within the borehole at depths shallower than specified, the borehole shall be advanced by chiseling. If in the opinion of the Project Engineer, the rate of advancement of borehole is still low, coring may be resorted. The contractor has to obtain the consent from the Project Engineer while terminating each borehole.<br />Within SEVEN days of the completion of a borehole, borelog shall be prepared in the approved proforma and submitted to Project Engineer for further use.<br />3. In-situ Tests<br />Standard Penetration Tests<br />The SPT shall be conducted in 150 mm diameter boreholes using a Split spoon sampler. The sampler should conform to the specifications given in IS 9640:1980. The weight of the drop hammer should be 63.5 kg and the height of fall of this hammer should be 75 cm. The sampler should be driven through a length of 450 mm and the number of blows for every 150mm penetration should be recorded. The first 150mm of drive may be considered as seating drive. The total blows required for the second and third 150mm penetration shall be termed as the penetration resistance N.<br />These tests shall be conducted in boreholes at intervals of 1.5m upto 15m depth and at intervals of 2.0 m beyond 15m depth and at every change of strata. The first penetration test in each borehole shall be conducted either at 1.5m depth or less from existing ground level and last SPT shall be conducted at the termination depth of borehole.<br />Vane Shear Tests<br />Vane shear tests shall be conducted in boreholes in saturated clays of soft to medium consistency, sensitive clays which are highly susceptible to sampling disturbances, and in clayey strata where N value is less than 8. Vanes of diameter 50 mm and length 100 mm should be used. These tests shall be conducted in accordance with IS 4434:1978. For vane testing instruments that do not read the torque directly, a calibration curve to convert the readings of torque shall be provided. These calibration curves shall be checked periodically.<br />Records of vane shear tests shall be maintained in a suitable form including all testing details and submitted to Project Engineer for further use.<br />4. Sampling<br />Disturbed Soil Samples<br />Disturbed samples shall be collected at every 1.5 m up to 15m depth and at intervals of 2.0 m beyond 15m depth and at every change of strata from borehole. They shall be fully representative of the zone from which they are taken. Weight of disturbed samples shall not be less than 1kg and shall be taken as per IS 1892:1979. They shall be placed immediately in airtight containers with a minimum of air space so as to maintain the natural moisture content for at least one week.<br />Identification levels, indicating depth, borehole number and visual soil classification shall be affixed on the containers.<br />Undisturbed Soil Samples<br />Undisturbed soil samples shall be collected as per IS 2132- 1986. UD samples shall be collected from all boreholes from representative soils at intervals of 3.0 m in depth and at every change of stratum, whichever occurs earlier. For adjacent boreholes, depth of sample collections shall be staggered to cater for full layer. The area ratio of the sampling tubes shall not exceed 20%. 80mm/100mm nominal diameter of the tubes shall be used. In soft deposits, piston sampler shall be used to collect UDS. <br /> <br />Before taking an undisturbed sample the bottom of the boring shall be carefully cleaned to remove loose materials and where casing is being used the sample shall be collected from the bottom of the casing.<br />Care shall be taken to minimise sample disturbance while collection of samples. Samples shall be collected preferably by pushing the sampler. Driving by hammer above ground level (like SPT) is not acceptable. However, for stiff / hard soil a sliding hammer can be used for driving the sampler at sampler head.<br />Where an attempt is made to collect an undisturbed sample, which is aborted because of slippage, the boring shall be cleaned out for the full depth to which the sampling tube has been driven and the recovered soil shall be kept as a disturbed sample. A fresh attempt shall be then made from the level of the base of the aborted attempt, and the contractor may use a core catcher between the cutting shoe and sampling tube; alternatively, an additional sample tube may be coupled. Where full recovery is not achieved the actual length of sample in the sampling tube shall be recorded and the reason for only partial recovery shall be noted. Samples with recovery of less than 60% shall be regarded as disturbed samples.<br />The depths from which all samples are taken shall be recorded. The level at the top of the sample and the length of the sample obtained shall be given, together with the depth of casing. As soon as the sample is obtained from the borehole, the ends of the sample should be cut and removed to a depth of 2.5 cm and several layers of molten wax should be applied to each end. UD samples shall be transported and stored vertically upright.<br />Rock Samples<br />Disturbed Samples: <br />The sludge from percussion borings, or from rotary borings, which have failed to yield a core, may be taken as a disturbed sample. It may be recovered from circulating water by settlement in a trough. The rock type may be deduced by examining the material of which the sludge is composed.<br />Undisturbed Samples: <br />Core samples shall be extracted by the application of continuous pressure at one end of the core with barrel held horizontally without vibration. Care shall be taken to maintain direction of extrusion of sample same as while coring to avoid reversal of stresses. Immediately after withdrawing from core barrel, the core shall be transferred in to core boxes specially prepared for the purpose. The core boxes of size 1500mm x 320mm shall be made as per IS 4078 - 1980 to hold 5 rows of cores. The photographs of the rock samples in barrel shall be enclosed.<br />Percent core recovery and RQD value shall be determined in field or laboratory for each core run and recorded on boring log as per IS: 11315 (PART II) –1985. While boring in rock, the spacing and thickness of discontinuities, lithology, condition and orientation of discontinuities are to be recorded and reported. <br />Depths below the surface of the ground shall be indicated at 1.5m intervals by writing the depth in indelible pencil on a small block of wood, which is inserted in it’s correct position in the box. The exact depth of any change of strata should be shown in the same way. Where there is a failure to recover core, this should be recorded in the same way. For shear strength determination, a core with diameter to height ratio of 1:1 is required. <br />Rock pieces may be used for determination of specific gravity and classification. The core samples shall be transported to the laboratory for testing. <br />Water Samples<br />Samples of groundwater shall be taken from each boring in which water is found. Where water has been previously added for boring purposes, the boring shall be bailed out before sampling until only uncontaminated groundwater is present in the boring. <br />The samples shall be stored in watertight containers, which shall be washed out with groundwater before filling. The sample shall be not less than 0.5 litres in volume. In the event that sample contains any suspended sediment, a larger quantity of sample shall be obtained and allowed for sediment settling. <br />The clean water shall then be decanted into the storage container. The depth of borehole, depth of casing and water level at the time of sampling and the depth from which the sample is obtained shall be recorded on two labels to be fixed to the samples, using appropriate non-fade waterproof marker pen.<br />Labeling, Packing and Transporting<br />Sample Labeling<br />All samples, irrespective of their type, shall be clearly and permanently labeled with the following information immediately upon recovery:<br />a.Project name and location<br />b.Borehole number<br />c.Depths at which sample collected<br />d.Date of recovery<br />e.In the case of core samples or undisturbed "tube" samples, the top and bottom of the samples shall be clearly marked as such.<br />All samples shall be fixed with two labels one on the lid or screw top, the other on the jar or on the steel tube.<br />Packing and Transporting<br />The contractor shall be responsible for the packing and transport of sample to the laboratory as approved by the Project Engineer. All collected samples shall be transported at the end of every borehole to the laboratory. The contractor shall ensure that all packing and transport arrangements are suited to the type of sample(s) in question and that the least possible disturbance of the samples will occur during transport. In any event, the contractor shall be held responsible for any damage to samples.<br /> Laboratory Testing<br />After collecting disturbed and undisturbed soil samples from different boreholes at different depths and trial pits, a laboratory test schedule shall be prepared. The laboratory tests shall essentially comprise of but not limited to the following<br />Moisture Content Determination<br />The natural moisture content of all the soil samples brought from the site should be determined as prescribed in IS 2720 (Part 2) -1973.<br />Grain Size Distribution<br />Sieve analysis for grain size distribution should be conducted on all disturbed and undisturbed samples collected from boreholes and trial pits. A hydrometer analysis should be carried out on fractions less than 75 micron wherever applicable as per IS 2720 (Part 4)-1985. For the hydrometer analysis, the hydrometer should be calibrated appropriately and all corrections viz. meniscus, temperature and dispersing agent corrections applied to the readings. <br /> The grain size distribution curve i.e. Percent finer vs particle diameter should be plotted. A table showing the percentage of various grain sizes (gravel to clay), D10, D60, Uniformity Coefficient Cu and Coefficient of Curvature Cc for each test should be given.<br />Atterberg Limits<br />These tests shall be carried out on clay fractions (size < 75 microns) for all disturbed and undisturbed samples. The test results should include liquid limit, plastic limit, and plasticity index and shrinkage limit of the soil samples. These tests shall be conducted as per IS 2720 (Part 5)-1985 and IS 2720(Part-6)-1972. In swelling type of soils, the free swell index should be determined.<br />Consolidation Tests<br />These tests shall be conducted on undisturbed samples of clayey soils for vertical drainage only. <br />The following loading stages shall be employed:<br />0.1, 0.25, 0.50, 1.0, 2.0, 4.0, 8.0 kg/cm2.<br />From e vs log p curves, pre-consolidation pressure shall be determined to establish whether the soil is normally consolidated or over-consolidated. <br />The point (e, p) showing initial condition of the soil under test must be specifically marked on the consolidation curves. Cycle(s) of loading, unloading and reloading shall be applied. <br />The field virgin compression curve shall be established. Settlement predictions based on the field virgin compression curve shall only be acceptable. The procedure adopted in respect of obtaining compression indices from the field curve and that for computing settlements for the type of soil under consideration shall be clearly illustrated in the report.<br />The following curves shall be included in the report:<br />a)e Vs log p<br />b)e Vs p<br />c)Compression Vs log (t) or compression Vs square root (t)<br />The choice of relationship in part (c) depends upon the shape of the plot that enables clear determination of Cv, the coefficient of consolidation. The time period required for 50% and 90% primary consolidation should be given in the report.<br />Location of pc (pre-consolidation pressure) shall be clearly indicated in the e-log p curve.<br />Values of mv and cv shall be furnished for different pressure ranges including the values of e0, Cc, & pc, in the e-log p plot as well as in tabular form. Computation of secondary settlements if significant shall also be made and included in the report.<br />Unconfined Compressive Strength (UCS)<br />These tests shall be done as per IS 2720 (Part 10) -1973 on undisturbed soil samples of saturated (or nearly saturated) non-fissured cohesive soils. The cylindrical soil sample should be tested quickly without allowing for drainage, in vertical compression. The UCS and cohesion (half the UCS) of the samples should be reported.<br />Triaxial Tests<br />These tests shall be conducted on UDS collected in the boreholes. The test shall be performed as per IS 2720 (Part 11) -1971 & IS 2720 (Part 12) -1987 unless otherwise specified. The specimens of required dimension (with height twice the specimen diameter) shall be prepared from the UD sampling tubes.<br />The specimen shall be placed centrally on the pedestal of the triaxial cell. The cell containing the specimen shall be placed in the loading machine. The operating fluid shall be admitted to the cell and the pressure raised to the desired value. The initial reading of the gauge measuring the axial compression of the specimen shall be recorded. <br />A rate of axial compression shall be selected such that failure is produced within a period of approximately 5 to 15 minutes. The test shall be commenced and a sufficient number of simultaneous readings of the load and compression measuring gauge being taken to define the stress-strain curve. The test shall be continued until the maximum value of the stress has been passed or until an axial strain of 20 percent has been reached. The specimen shall then be unloaded and the final reading of the load measuring gauge shall be recorded.<br />A minimum of three specimens shall be tested as above for different cell pressure. The dimensions of each specimen, the bulk density, the moisture content, the cell pressure, the value of the maximum principal stress difference, and the corresponding strain and time to failure and the rate of strain at which the test was conducted shall be reported. <br />All the stress-strain diagrams as well as Mohr's envelopes shall be included in the report. The Secant Modulus and Tangent Modulus at 50% of the peak strength shall be indicated. The shear strength parameters shall be obtained from the plot of Mohr circles and be reported.<br />Depending on the type of soil the following type of tests shall be conducted.<br />Type of SoilType of TestFine Sand/Silt (ML, MI)CUClayey soils ( CH, CI)UU<br />Direct Shear Tests<br />These tests shall be conducted on disturbed samples collected in boreholes/trial pits remoulded to their natural density. The test shall be performed as per IS 2720 (Part 13) – 1971. In case cohesive soils, the specimen of required dimension shall be prepared by compacting the sample to the natural density and natural moisture content and extracted and trimmed to required size or directly compacted in to the shear box.<br />In case cohesion less soils, the sample shall be prepared directly in to the shear box itself with base plate or grid plate/ porous plate.<br />The shear box with the specimen, plain grid plate over the base plate at the bottom of the specimen and plain grid plate at top of the specimen shall be fitted in to the loading frame. The serrations of the grid plates should be at right angles of the direction of shear. <br />A water jacket should be provided so that the specimen does not get dried during the test. The test shall be commenced and shear load reading and displacements should be noted at regular intervals. The test shall be continued until the specimen fails or to 20 percent of longitudinal displacement, which occurs first. The specimen then be unloaded and final moisture content shall be noted.<br /> A minimum of three specimens shall be tested as above for different shear loads. The dimensions of each specimen, the bulk density, the moisture content, the normal load, the value of the maximum principal stress difference, and the corresponding strain and time to failure and the rate of strain at which the test was conducted shall be reported. <br />All the stress-strain diagrams as well as Mohr's envelopes shall be included in the report. The Secant Modulus and Tangent Modulus at 50% of the peak strength shall be indicated. The shear strength parameters shall be obtained from the plot of Mohr circles and be reported.<br />Point Load Test on Rock Cores<br />The tests shall be performed as per IS 8764-1978.Intact samples of minimum 50 mm diameter and length equal to 1.5 times the diameter should be tested on a Point Load Tester and its point load index shall be determined. <br />The Uniaxial Compressive Strength (UCS) of the sample should be calculated from the point load index. The index as well as the UCS should be reported<br />Uniaxial Compressive Strength of Intact Rock Samples<br />The tests shall be performed as per IS 9143 – 1979.Intact rock cores of minimum NX size and length 2.5 to 3 times the diameter should be tested for its Uniaxial compressive strength. This test should be conducted on perfectly cylindrical samples, which shall be polished and conform to the relevant Indian Standards. The UCS of the sample should be reported along with the diameter and length of the sample.<br />Chemical Tests<br />Chemical test shall be conducted on soils and water samples as per the relevant IS latest revisions to report the following:<br />a)pH<br />Chlorides in ppm & percentage<br />Sulphates in ppm and percentage and expressed as S03 & S04<br />Other Tests <br />Brazilian split tests on core as per IS:10082:1981<br />Moisture content , porosity and bulk density of rock samples as per IS 1124 -1974<br />Mineral analysis on rock samples<br />Carbonate content of soil and rocks<br /> Organic content of soil.<br />Report Preparation<br />The report shall also contain the summary of various soil parameters evaluated in a proforma. The final report shall include but not limited to the following:<br />A plot plan shall be attached with the report showing all test locations with their co-ordinates and reduced levels.<br />General geological information of the region.<br />Character and genesis of soil.<br />Procedure of investigations and methods of various tests adopted.<br />Detailed bore logs indicating co-ordinates, reduced ground/bed levels, ground water table, subsoil section along various profiles indicating borehole nos., depth wise in situ tests like SPT, etc.<br />All field and laboratory test results shall be plotted against depth and also in tabular form.<br />Summary of results obtained from various tests and their interpretation to evaluate various soil parameters.<br />Sets of longitudinal and transverse soil profile connecting various boreholes showing the variation of soil stratum.<br />Comments on chemical nature of ground water and soil with due regard to potential deleterious effect on steel and other materials and firm recommendations on protective measures. Also remedial measure for sulphate attack or acidity shall be dealt with in detail giving clear practical recommendations.<br /> All recommendations shall be supported by back up calculations. Final report shall be submitted in Four (4) copies. All the data collected including the original records.<br /> <br />