轴向循环加载卸载条件下饱和软土变形特性试验研究

研究循环加卸载条件下软黏土的强度和变形特性具有一定的工程实践价值。利用自行改进和研制的连续加载一维K_0固结仪对饱和软土进行轴向循环加卸载试验。结果表明:各级卸载应力-应变曲线是双曲线,再加载曲线应力-应变关系在上级卸载载荷之前为双曲线,超过卸载载荷为直线,呈现不断硬化的现象,试样产生塑性变形和弹性变形,且塑性变形和弹性变形分别与卸载等级呈线性关系;以原有双曲线本构关系为基础,利用各级加载轴向最大应力和初始切线模量,卸载曲线的轴向最大应变和初始割线模量,引入新的模型参数,从而建立轴向循环加卸载的本构方程,并验证了其可靠性。对各级塑性滞回能进行了计算,随着卸载应力水平的增大,塑性滞回能不断增大,且通过拟合加卸载过程中消耗的塑性滞回能与卸载应力水平呈良好的二次曲线关系。

Study of deformation of saturated soft soil under axial cyclic loading and unloading

It is of practical value to study the strength and deformation characteristics of soft clay under cyclic loading and unloading. This study conducted an axial cyclic loading and unloading test of saturated soft clay, using the continuous load one-dimensional K₀ consolidation apparatus developed and improved by Chang''an University. The results showed that the stress strain curve of saturated soft clay is hyperbolic during the unloading period. During the reloading period, the curve is hyperbolic when the loading quantity is less than unloading quantity and the curve is straight line and keep hardening when the loading quantity is greater than unloading quantity. The plastic deformation and elastic deformation of test samples produced in the test have linear relation with the unloading level. On the basis of the original constitutive relation, axial circulation loading and unloading constitutive equation have been established using the loading axial stresses, the initial tangent modulus, maximum unloading axial strain and its initial secant modulus as parameters. The reliability of the equations has been verified as well. The hysteresis energy increased with the increase of unloading stress, and there is a good quadratic curve between the consumption of hysteresis energy and unloading stress.