边坡、挡土墙等结构中的土体一般存在初始剪应力的作用,同时在地震、波浪等动荷载作用下,土体的初始剪应力与动荷载之间往往会存在一定的夹角。为了研究初始剪应力与循环荷载之间的夹角(剪切方向角)对土体软化指数的影响,采用多向循环单剪仪对温州软黏土进行一系列的循环单剪试验研究。研究结果表明,在特定剪切方向角下,随着循环应力比rc的增加,软化指数?逐渐降低,且在相同软化指数条件下,相邻循环应力比对应的循环圈数相差的幅度逐渐减小;循环应力比一定时,当剪切方向角在0°-90°范围内增加时,软化指数依次递增,当90°〈θ≤180°时,软化指数的变化趋势与0°-90°时相反;循环应力比rc=0.15时,在加载初期,θ=120°,150°,180°时,软化指数均分别较θ=60°,30°,0°时大。对试验数据进行回归分析,建立土体的软化指数模型和孔压–软化模型。
The soil elements within a slope or behind a retaining wall are subjected to the initial static shear stress prior to cyclic loading,and there exists an angle between the directions of initial static shear stress and cyclic loading under earthquake or wave loading. In order to investigate the effects of the angle between the directions of the initial static stress and cyclic loading on the softening index of soil,a series of tests were carried out using dynamic simple shear apparatus. The test results indicate that the softening index δ decreases with the increasing of cyclic shear stress ratio rc with a certain angle θ between the directions of cyclic loading and initial static shear stress. The difference of the loading cycles obtained from a certain value of δ corresponding to the two neighboring rc decreases. The softening index increases as the angle grows from 0° to 90°with a certain rc. An opposite evolution of softening index was observed for 90°θ≤180°. At the initial stage of cyclic loading,the softening index for θ = 120°,150°,180° is larger than that for θ = 60°,30°,0° when rc = 0.15,respectively. The softening index model and the model of pore pressure ratio versus softening were established through analysis of data regression.