冻结盐渍土三轴剪切试验过程中的损伤及压融分析

Damage and pressure melting analysis of frozen saline soils in process of triaxial compression tests

三轴剪切过程中损伤及压融等力学性质对冻结盐渍土的强度及变形影响显著。通过对-15℃德令哈含盐砂土进行一系列的三轴剪切循环试验及CT扫描试验,分析冻结盐渍土在三轴试验过程中的损伤演化以及压融量变化规律。研究发现,在三轴剪切中损伤变量随静水压力的变化而改变,在本文条件下当静水压力在1~12 MPa之间时,损伤变量随围压的增加而增加,当静水压力超过12 MPa时,损伤变量反而呈现减小趋势。同时,定义压融阈值ps以及压融量达到最大值时对应的静水压力值pm,研究表明：当静水压力小于ps时,试样内部几乎不存在压融现象;当静水压力大于ps且小于pm时试验内部的压融量可用二次函数描述;当静水压力超过pm时,试样中的压融量达到最大值λm,且压融极值点与损伤变量极值点对应的静水压力值基本一致。

The mechanical properties, such as damage and pressure melting, have significant influences on the strength and deformation behaviors of the frozen saline soils in the process of triaxial compression tests. In order to analyze the change laws of damage evolution and pressure melting variation, a series of triaxial shear loading–unloading-reloading tests and CT scanning tests are carried out for Delhi frozen saline soils at -15℃. The results show that the damage variable is influenced by hydrostatic pressure. When the hydrostatic pressure is between 1 MPa and 12 MPa, the damage variable increases with pressure, and when hydrostatic pressure is more than 12 MPa, with the increase of the hydrostatic pressure, the damage variable shows a decreasing trend. Meanwhile, the definitions of pressure melting thresholdsp and the corresponding hydrostatic pressure value pm when the pressure melting variable reaches the maximum value are given. The pressure melting is hardly existent in the sample when pressure is less than the threshold. When the pressure is between ps and pm, the pressure melting variables can be expressed by the parabola equation. And if the hydrostatic pressure exceeds pm, the pressure melting variable reaches the maximum value λm. Besides, the hydrostatic pressure corresponding to the maximum value of the pressure melting variables almost equals the hydrostatic pressure when the damage variable gets its maximum.