侧向卸荷条件下软土典型力学特性试验研究

 针对侧向卸荷条件下软土变形、强度、蠕变等典型力学特性，选取珠三角洲相沉积的典型灰黑色淤泥质软土进行室内三轴试验研究。试验结果表明：侧向卸荷条件下的应力–应变规律呈应变硬化现象，可采用平均应力进行归一；土样在侧向卸荷条件下进行不排水剪切时会产生负的孔隙水压力，使得有效应力强度反而低于总应力强度，与轴向加荷条件下的强度规律不同；侧向卸荷条件下的初始卸荷模量小于轴向加荷条件下的初始卸荷模量，与平均固结压力呈线性关系；任一时间的卸荷变形模量仍可表示为切线模量，并可通过试验成果推导得出；侧向卸荷条件下软土蠕变变形比轴向加载显著，即使在偏应力不大时仍占总变形的较大比例；应变率随时间的下降呈较好的双对数线性关系，可以建立考虑剪应力水平对初始应变率影响的线性经验公式来估算某级荷载下应变率随时间的发展。

TEST RESEARCH ON TYPICAL MECHANICAL CHARACTERISTICS OF SOFT CLAY UNDER LATERAL UNLOADING CONDITION

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.