TEST RESEARCH ON TYPICAL MECHANICAL CHARACTERISTICS OF SOFT CLAY UNDER LATERAL UNLOADING CONDITION
ZHOU Qiujuan1，2，CHEN Xiaoping1
(1. Department of Mechanics and Civil Engineering，Jinan University，Guangzhou，Guangdong 510632，China；2. Department of Hydraulic Engineering，Guangdong Technical College of Water Resources and Electric Engineering，Guangzhou，Guangdong 510635，China)
Abstract：The typical mechanical characteristics in deformation，strength and creep under lateral unloading condition of soft clay are investigated by laboratory triaxial tests. The specimens are black gray silty soft clay，which are taken from Pearl River Delta sediments. The results pointed that the stress-strain relationship shows the phenomenon of strain hardening，and can be normalized by average stress. The effective stress strength is lower than the total stress strength because minus pore water pressure is produced under the condition of lateral unloading，which is opposite to the stress law under the axial-loading condition. The initial unloading modulus under lateral unloading condition is smaller than that under the axial-loading condition，and there is a linear relationship with the average consolidation pressures. The unloading deformation modulus can be expressed as the tangent modulus at any time；and it can be obtained through the test results. Creep test shows that the creep deformation under lateral unloading condition is more significant than that under axial-loading condition. Even if the deviator stress is small，the creep deformation also occupied a large proportion of the total deformation. The logarithm of the strain rate decreases linearly with the increase of the logarithm of time. The development of the strain rate can be estimated at any loading condition from the linear experience formula considering the effect of shear stress on initial strain rate.
