10 is 2950 part i 1981 where bf bp represent sizes

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Unformatted text preview: Bp *Method of load test on soils ( second revision ). 10 IS : 2950 (Part I) - 1981 where Bf, Bp represent sizes of foundation and plate and Ep is the modulus determined by the plate load test. A-2.2 For stratified deposits or deposits with lenses of different materials, results of plate load test will be unreliable and static cone penetration tests may be carried out to determine Es. A-2.2.1 Static cone penetration tests shall be carried out in accordance with IS : 4968 (Part III)-1976*. Several tests shall be carried out at regular depth intervals up to a depth equal to the width of the raft and the results plotted to obtain an average value of Es. A-2.2.2 The value of Es may be determined from the following relationship: Es = 2 Ckd where Ckd = cone resistance in kgf/cm2. A-3. LABORATORY DETERMINATION OF Es A-3.1 The value of Es shall be determined by conducting triaxial test in the laboratory [ see IS : 2720 (Part XI)-1971† and IS : 2720 (Part XII)1981‡ ] on samples collected with least disturbances. A-3.2 In the first phase of the triaxial test, the specimen shall be allowed to consolidate fully under an all-round confining pressure equal to the vertical effective overburden stress for the specimen in the field. In the second phase, after equilibrium has been reached, further drainage shall be prevented and the deviator stress shall be increased from zero value to the magnitude estimated for the field loading condition. The deviator stress shall then be reduced to zero and the cycle of loading shall be repeated. A-3.3 The value of Es shall be taken as the tangent modulus at the stress level equal to one-half the maximum deviator stress applied during the second cycle of loading. *Method for subsurface sounding for soils: Part III Static cone penetration test ( first revision ). †Methods of test for soils: Part XI Determination of shear strength parameters of a specimen tested in unconsolidated undrained triaxial compression without the measurement of pore water pressure. ‡Methods of test for soils: Part XII Determination of shear strength parameters of soils from consolidated undrained triaxial compression test with measurement of pore water pressure ( first revision ). 11 IS : 2950 (Part I) - 1981 APPENDIX B [ Clause 3.1 (f) ] DETERMINATION OF MODULUS OF SUBGRADE REACTION B-1. GENERAL B-1.1 The modulus of subgrade reaction ( k ) as applicable to the case of load through a plate of size 30 × 30 cm or beams 30 cm wide on the soil is given in Table 1 for cohesionless soils and in Table 2 for cohesive soils. Unless more specific determination of k is done ( see B-2 and B-3 ), these values may be used for design of raft foundation in cases where the depth of the soil affected by the width of the footing may be considered isotropic and the extrapolation of plate load test results is valid. TABLE 1 MODULUS OF SUBGRADE REACTION ( k ) FOR COHESIONLESS SOILS *MODULUS OF SUBGRADE REACTION ( k ) IN kg/cm3 SOIL CHARACTERISTIC Relative Density Standard Penetration Test Value ( N ) For Dry or Moist State For Submerged State (1) (2) (3) (4) Loose < 10 1.5 0.9 Medium 10 to 30 1.5 to 4.7 0.9 to 2.9 Dense 30 and Over 4.7 to 18.0 2.9 to 10.8 *The above values apply to a square plate 30 × 30 cm or beams 30 cm wide. TABLE 2 MODULUS OF SUBGRADE REACTION ( k ) FOR COHESIVE SOILS SOIL CHARACTERISTIC Consistency (1) Stiff Unconfined Compressive Strength, kg/cm2 *MODULUS OF SUBGRADE REACTION ( Ks ) IN kg/cm3 (2) (3) 1 to 2 2.7 Very stiff 2 to 4 2.7 to 5.4 Hard 4 and over 5.4 to 10.8 *The values apply to a square plate 30 × 30 cm. The above values are based on the assumption that the average loading intensity does not exceed half the ultimate bearing capacity. 12 IS : 2950 (Part I) - 19...
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This note was uploaded on 03/14/2014 for the course CE 684 taught by Professor Prof.deepankarchoudhury during the Spring '13 term at IIT Bombay.

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