剪切路径对土与结构接触面三维循环特性影响研究

运用80t大型三维接触面试验机，通过改变往返圆弧剪切路径的半径和旋转角度幅值研究不同剪切路径下接触面三维循环力学特性，重点分析了剪切路径的影响规律。剪切路径由于影响两正交切向位移大小、方向转变及结构面附近土颗粒运动形态，从而导致接触面剪切体变及可逆性剪切体变-x或y向位移关系、切向应力位移关系及切向应力间关系形式差异显著。随旋转角度幅值的增大，接触面x向应力位移关系形式由双曲线向椭圆形转变；残余摩擦角由35°逐渐减小到33°，而后趋于稳定；峰值摩擦角则保持35°不变。不同剪切路径下接触面力学特性亦有诸多相同之处：抗剪强度具有各向同性；往返型路径下均产生明显的不可逆性和可逆性剪切体变，随循环剪切的进行，前者单调增长，后者峰值逐渐减小而后趋于稳定；不同剪切路径下接触面可逆性剪切体变-主切向位移关系及主剪应力-主切向位移关系具有良好的一致性；且后者曲线形式随循环剪切的进行由双曲线形式逐渐向理想弹塑性模式转变。

Influence of shear paths on 3D cyclic behaviors of the gravel-structure interface

Using a large-scale apparatus (3DMAS), the influence of shear paths on 3D cyclic behaviors of the gravel-structure interface was investigated based on a series of direct shear tests in various two-way arc cyclic shear paths. The test results indicate that the shear paths play a notable role in 3D cyclic behaviors of the interface. Remarkably differences can be observed in the relationship between volumetric change and tangential displacement, shear stress-displacement hysteretic relationship, and shear stress relationship in x or y direction in different shear paths. The residual cyclic friction angle of the interface gradually decreases from 35° to the stabilized value around 33° with increasing rotation angle amplitude, while the peak cyclic friction angle remains at 35°. Meanwhile, in all two-way shear paths, the interface contracts when being unloaded and then dilates after sheared to some extent, and thus presents irreversible and reversible volumetric change with decreased peak value due to cyclic shearing. The interface presents good consistency in the relationship between reversible volumetric change and resultant tangential displacement, and the relationship between resultant shear stress and resultant tangential displacement, independent of shear paths. The resultant shear stress-displacement relationship gradually transits from the hyperbolic trend to the elastic-perfectly plastic model with cyclic shearing continuing, and the cyclic shear strength of the interface appears to be isotropic.