土工合成材料大型直剪界面作用宏细观研究

利用大型直剪模型试验设备,在不同竖向压力下进行一系列的土工合成材料直剪试验,应用数码可视化跟踪技术,结合土体变形无标点量测技术来研究双向土工格栅与砂土直剪界面作用的宏细观特性,同时分析界面附近土压力分布规律,并研究界面颗粒运动变化规律和细观组构演化特征与宏观特性的关联。分析结果表明,直剪筋土界面附近竖向压力分布从前端依次向后端减少;直剪界面位移达25 mm时,形成了稳定的剪应变集中带;在筋土界面（6～8）D₅₀粒径厚度范围内,界面颗粒以旋转和平动方式同时位移,该范围外颗粒以平动方式沿剪切方向位移,且位移较小;在剪切过程中,界面颗粒发生旋转,土体发生剪胀,孔隙率增大,平均接触数减小,颗粒重新被压密,孔隙率减小,平均接触数增多,颗粒长轴排列趋于水平方向,各细观组构处于相对稳定状态。

Macroscopic and mesoscopic studies of interface interaction on geosynthetics by use of large direct shear tests

Through a series of direct shear tests under different vertical stresses, digital visual tracking technology and non- punctuation soil deformation measurement techniques are adopted to study the macroscopic and mesoscopic behaviors of the interface between biaxial geogrid and sand. The distribution laws of soil pressure near the reinforcement soil interface are analyzed, and the changes of interface movement and mesoscopic fabric evolution characteristics are studied. The results show that the distribution of the vertical pressures decreases from the front to the back end on the near direct shear reinforcement interface. The direct shear displacement is up to 25 mm, and a stable shear strain concentration zone is formed. In the range of reinforcement interface 6 to 8 times D₅₀ particle size thickness, the sand particle particles on the interface exhibit rotational and translational displacements, and outside this range, the particles show translational displacement along the shearing direction, and the displacement is smaller. During the shearing process, the interface particles rotate, soil dilatancy occurs, the porosity increases, the coordiation number decreases, the particles are re-compacted, the porosity decreases, the coordiation number increases, the particles along the long axis orientation tends to be horizontal direction, and various meso fabrics are in relatively stable state.