Unformatted text preview: ases 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 SUBCRADE REACTION ( k ) FOR
COHRSIONL.ESS SOILS
*MODULUS SOIL CHARACTERISTIC c____~
Relative
Density Standard Penetration
Test Value ( N) (1) rFor Dgap, *___
For $ttzerged
(4) 1.5
1.5 to 4’7
4.7 to 18.0 < 10
10 to 30
30 and Over Dense Moist (3) (2) Loose
Medium OF SULIGRADE REACTION
( k ) IN kg/cm3 0.9
0.9 to 29
29 to lo.8 *The above values apply to a square plate 30 x 30 cm or beams 30 cm wide. TABLE 2 MODULUS OF SUBCRADE REACTION ( k ) FOR
COHESIVE SOILS SOIL CHARACTERISTIC #_,Consistency
(1) 7
Unconfined Compressive
Strength, kg/cm*
(2) *MODULUS
OF SU~GRADB
RENTION ( k,) IN kg/cm” Stifi
1 to 2
Very stiff
2 to 4
Hard
4 and over
*The values apply to a square plate 30 x 30 cm. The above values
assumption that the average loading intensity does not exceed half the
capacity. 12 (3)
2.7
27 to 5.4
5.4 to 108
are based on the
ultimate bearing IS:2950( PartI) B2. FIELD DETERMINATION
B2.1 In cases where the depth of the soil affected by the width of the
footing may be considered as isotropic, the’value of k may be determined in
accordance with IS : 92141979*. The test shall be carried out with a plate
of size not less than 30 cm. B2.2 The average value of k shall be based on a number of plate load tests
carried out over the area, the number and location of the tests depending
upon the extent and importance of the structure.
B3. LABORATORY DETERMINATION B3.1 For stratified deposits or deposits with lenses of different materials,
evaluation of k from plate load test will be unrealistic and its determination
shall be based on laboratory tests [ see IS : 2720 ( Part XI )1971t and
IS : 2720 ( Part Xl1 )1981$].
B3.2 In carrying out the test, the continuing cell pressure may be so selected
as to be representative of the depth of average stress influence zone (about
0.5 B to B ).
B3.3 The value of k shall be determined from the following relationship:
k = 065 I2 . 1 .+
cc B where
E, = Modulus of elasticity of soil ( see Appendix A ),
fi= Young’s modulus of foundatipn material, p = Poisson’s ratio of soil ( see Appendix A ), and I = Moment of inertia of structure
foundation. if determined or of the B3.4 Im the absence of laboratory test data, appropriate values of E, and p
may be determined in accordance with Appendix A and used in B3.2 for
evaluation of k.
*Method of determination of subgrade reaction ( k value ) of soils in the field.
tMethods of test for soils : Part XI Determination of shear strength parameters of
specimen tested in unconsolidated undrained triaxial compression without the measurement of pore water pressure.
tMethods of test for soils : Part XII Determinatio’n of shear strength parameters of
soil from consolidated undrained triaxial cdrnpression test with measurement of pore
water pressure (first revision ). 13 . IS:29SO(PartI)1981
B4. CALCULATIONS
B4.1 When the structure is rigid ( see Appendix C ), the average moduhrs
of subgrade reaction may also be det...
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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.
 Spring '13
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