循环荷载作用下粗粒料与掺砾粘土接触面单剪试验研究

Cyclic Simple-shear Tests on the Interface between Granular Material and Gravel-clay

土石坝内部存在较多的接触面,在静、动力荷载作用下,接触面的力学特性对坝体的稳定性具有显著的影响。基于动态单剪仪,开展了粗粒料与掺砾粘土接触面循环单剪试验。试验结果表明,初始剪应力加载方向对相对位移有较大影响:相对位移总是在沿初始剪应力加载方向一侧较大;在一个剪切循环内,正、反向加载时,若剪应力较小,发生剪缩变形,若剪应力较大,则发生剪胀变形;卸载时试样发生剪缩变形;整个剪切循环过程中,试样总体上处于剪缩状态;循环单剪过程中,接触面抗剪强度提高;接触面抗剪强度随着法向应力的增大而增大,呈线性关系。

Interfaces,which are commonly introduced into the rock filling dams constructed with different materials bearing distinct mechanical properties,according to the results of previous study,can exert evident influences on the performance of the whole dam.Using the NGI-type simple shear apparatus,cyclic simple shear tests on the interface between granular material and grave-clays were conducted to study the mechanical behaviors.Observations and conclusions are summarized based on the test results as follows： （1） The direction of initial shear stress significantly influences the mode of relative displacement of interface, i.e.relative displacement in the direction of initial shear stress is always greater than that in the opposite direction.（2） The volumetric deformation is regular during any semi-cycle in such a manner that at the loading stage of first 1/4 cycle,the specimen shrinks dominantly at low shear stress but dilates at high shear stress level,whereas only shrinkage deformation takes place at the next 1/4 unloading stage;after each cycle,the negative volumetric deformation dominates.（3） Shear strength of the interface increases as the shear cycle increases and is approximately linear proportional to the normal stress level on the interface.