间歇性变围压循环荷载作用下饱和软黏土变形特性

Effects of intermittent cyclic loading with cyclic confining pressure on deformation behaviors of saturated clay

交通荷载由循环加载和间歇停振两部分组成,间歇停振对土体动力特性的影响不容忽视。交通荷载引起的应力场包含循环变化的轴向偏应力和围压。因此,通过对软黏土开展一系列间歇性变围压循环加载试验,对饱和软黏土在间歇性加载和循环围压作用下的变形特性进行了研究,分析了循环围压和间歇停振阶段排水条件对软黏土累积轴向应变的影响。研究结果表明,不同试验条件下软黏土累积轴向应变增量随加载阶段的变化趋势保持一致,即累积轴向应变增量随加载阶段的增加逐渐减小。累积轴向应变增量随循环围压的增大而减小。间歇停振阶段不同排水条件下,试样累积轴向变形变化规律也有所区别:部分排水条件下,循环加载阶段产生的超孔隙水压力在间歇停振阶段消散,试样累积轴向应变在间歇停振阶段有一定程度的增长;不排水条件下,循环加载阶段产生的一部分变形在间歇停振阶段得以慢慢恢复,试样累积轴向应变有所减小。上述研究成果可加深对间歇性循环荷载作用下软黏土变形规律的认识。

Traffic loading is composed of cyclic loading and intermittent periods,in which the influences of intermittent period on the dynamic characteristics of soil cannot be ignored.The stress field in subgrade soil caused by the traffic loading includes cyclic deviator stress and cyclic confining pressure.Therefore,a series of cyclic triaxial tests in intermittent cyclic loading mode with cyclic confining pressure are carried out to study the deformation behaviors of saturated clay,and the effects of the cyclic confining pressure and drained conditions during the intermittent period are investigated.The results show that the relationship between the accumulated axial strain increment and the loading stages are similar under different test conditions:the accumulated axial strain increment gradually decreases as the loading stage increases.Additionally,the variation of the accumulated axial strain increment is also affected by the cyclic confining pressure,in which the accumulated axial strain increment decreases with the increasing cyclic confining pressure.Besides that,the variations of accumulated axial strain are also different under different drained conditions during the intermittent period:the excess pore water pressure induced in cyclic loading period dissipates under partially drained conditions during the intermittent period,leading to that the accumulated axial strain of soft clay increases in a certain extent during the intermittent period;part of the deformation produced during the cyclic loading period can recover under undrained conditions during the intermittent period,and the accumulated axial strain of soft clay decreases.The above test results may deepen the understanding of the deformation behaviors of soft clay under intermittent cyclic loading.