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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
*MODULUS SOIL CHARACTERISTIC c_--_--_------_~
Density Standard Penetration
Test Value ( N) (1) r--------For Dgap, *-_--_-_
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
RENTION ( k,) IN kg/cm” Stifi
1 to 2
2 to 4
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 to 5.4
5.4 to 108
are based on the
ultimate bearing IS:2950( PartI)- B-2. FIELD DETERMINATION
B-2.1 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 : 9214-1979*. The test shall be carried out with a plate
of size not less than 30 cm. B-2.2 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.
B-3. LABORATORY DETERMINATION B-3.1 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$].
B-3.2 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 ).
B-3.3 The value of k shall be determined from the following relationship:
k = 0-65 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 B-3.4 Im the absence of laboratory test data, appropriate values of E, and p
may be determined in accordance with Appendix A and used in B-3.2 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
B-4.1 When the structure is rigid ( see Appendix C ), the average moduhrs
of subgrade reaction may also be det...
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