循环荷载作用下结构性软土微结构演化特性试验研究

为探讨动荷载作用下结构性软土微结构演化特征,对天津滨海新区典型结构性软土进行动力三轴试验,并对特定循环振次下土样进行微结构制样及电镜扫描,重点研究不同动应力比、不同振次以及不同围压下,循环荷载作用对软土微结构演化的影响。试验与测试结果表明:随动应力比、振次以及围压的增加,颗粒数量和孔隙数量增加,而颗粒等效直径、颗粒形态比、孔隙等效直径、孔隙形态比减小。当动应力幅值小于临界幅值时,微观结构随振次增加很快趋于稳定,当动应力幅值大于或等于临界幅值时,微观结构随振次增加持续处于变化中。循环荷载作用过程中,当围压分别在土体固结结构屈服应力前后取值时,微观结构参数值存在明显变化,不同微结构参数值与振次均呈对数关系,相关性较好。

Experimental research on microstructure characteristics of structural soft clays under cyclic loading

Dynamic triaxial tests are performed for typical soft clays from Binhai New District in Tianjin to study the microstructure characteristics of structural clays under dynamic loads. Soil samples after the specific numbers of loading cycles are sliced and scanned with SEM. The research focuses on the effects of different cyclic stress ratios，the number of cycles and the cell pressures on the microstructure variation of soft clays. The test results show that the numbers of particles and pores increase with the increase of cyclic stress ratio，the number of cycles and the cell pressure，and on the contrary，the equivalent diameter and the shape ratio of particles and pores decrease. The microstructure tends to be stable with the increase of the number of cycles when the cyclic stress amplitude is less than a critical value. However，the microstructure changes constantly with the increase of the number of cycles when the cyclic stress amplitude is greater than or equal to the critical amplitude. Microstructure parameter values have obvious changes during the cyclic loading when the cell pressure is around the consolidation yield stress. Different microstructure parameter values change with the number of cycles logarithmically with good correlation.