A series of undrained triaxial shear tests on undisturbed Nanyang expansive clay under saturated K

0

condition have been performed. Two different stress paths

reduced triaxial compression（RTC） and reduced triaxial extension（RTE）

four axial consolidation stress（80 k Pa

160 kPa

240 k Pa and 320 kPa）

and three stress rate（0.02 kPa/min

0.2 kPa/min and 2 kPa/min） were configured by GDS triaxial system. Based on the experimental data

the relationship among initial tangent modulus E

i

ultimate deviatoric stress q

ult

of expansive soil

consolidation

stress

and unloading rate was established. The results showed that the stress-strain relationship of expansive soil was hyperbolic along the unloading paths in both RTC test and RTE test. The shear strength increased as the stress rate and confined pressure increased monotonously. The changes of initial tangent modulus Ei and the ultimate principal stress difference q

ult

were similar to the shear strength. The initial tangent modulus E

i

increased exponentially and the ultimate principal stress difference q

ult

increased linearly as the confined pressure increases. Based on the modified Duncan-Chang model

the prediction formula considering the stress rate was built for expansive soil under K

0

consolidation condition.