In order to solve the problem of reckoning without shear contraction in K-G model suggested by Specification of Soil Test and keep its simplicity

a shear contraction modulus is proposed and a three-modulus modified K-G-D model is suggested which has seven parameters; the integrated incremental stress-strain relations are expressed by mean normal stress

generalized shear stress

volumetric strain and generalized shear strain are given. Model calibration for normal consolidated clay soil is carried out by isotropic consolidation tests and drained triaxial compression tests that the mean normal stress remains constant

model verification is carried out by the drained conventional triaxial compression tests

the computation results by the model parameters coincide well with curves of the tests

which demonstrates that the modified method is rational and applicable. The modified model is capable of reflecting the characteristics of pressure sensitivity

shear contraction and strain hardening

and suitable to underconsolidated and normally consolidated clay soils

loose and medium sands under the stress paths of mean normal stress increasing or remaining constant. In addition

the model calibration does not need additional tests

the modified model is clear in concept

simple in form and convenient to use.