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交通、波浪、地震等循环荷载引发不同主应力方向变化模式,对软土地基长期沉降与稳定产生显著影响。为研究饱和软黏土在交通荷载下的长期动力特性,借助空心圆柱扭剪仪开展偏应力空间中主应力轴心形线旋转、圆形旋转与定向剪切等3类主应力方向变化路径的室内模拟,对比研究了不同试验条件下试样不排水塑性累积变形、孔压、临界动应力比与动强度特性的发展规律,研究表明:(1)不同主应力轴旋转路径下土体临界应力比由低到高依次为主应力轴圆形旋转、主应力轴心形旋转、拉压非等幅三轴路径。与前面临界应力比分布相对应,在轴向累积应变稳定型中,产生的塑性累积变形与极限孔压依次减小;(2)振次大于一定数值时,不同主应力方向变化路径下稳定型试样的轴向累积应变与时间的对数具有良好的线性关系,并依此建立了轴向塑性累积变形方程;(3)与轴向塑性累积变形相对应,动力荷载下土体孔压增长也存在3种发展规律,主应力轴连续旋转路径下临界型破坏的土体孔压-应变时程曲线呈三阶段两相态点模式;(4)在其他条件均相同时,土体在主应力轴圆形旋转路径下强度最小,在主应力轴心形旋转路径下的次之,在拉压非等幅动三轴路径下最高。
Cyclic loads such as traffic, wave and earthquake lead to different modes of principal stress direction change, which have a significant impact on long-term settlement and stability of soft ground. In order to study the long-term dynamic characteristics of saturated soft clay under traffic load, three types of principal stress direction changing paths, such as circular principal axis of rotation, directional circular shear and directional shear, Simulation and comparative study of the law of undrained plastic cumulative deformation, pore pressure, critical dynamic stress ratio and dynamic strength characteristics under different test conditions, the study shows that: (1) under different principal stress axis rotation path of soil bulk density critical stress ratio From low to high followed by the main axis of rotation of the principal axis of rotation, the main stress axis rotation, tension non-constant amplitude three-axis path. Corresponding to the distribution of the front critical stress ratio, the plastic cumulative deformation and the ultimate pore pressure generated in the axial cumulative strain stability decrease in turn. (2) When the vibration frequency is larger than a certain value, The axial cumulative strain of the specimen has a good linear relationship with the logarithm of the time, and the axial plastic cumulative deformation equation is established accordingly. (3) Corresponding to the axial plastic cumulative deformation, the pore water pressure increases under dynamic load There are also three kinds of developmental rules. The pore pressure-strain curve of the soil under critical stress failure along the main stress axis shows a three-phase two-phase model. (4) When the other conditions are the same, Under the circular axis of rotation, the stress axis has the lowest strength, the second under the main axis of rotation and the highest under the tension and compression non-amplitude and amplitude three-axis path.