直剪剪切速率对粗粒土强度与变形特性的影响

土体的强度和变形对路基及边坡的稳定性具有控制作用，为分析剪切速率对粗粒土抗剪强度和变形特性的影响，基于THE-1000型室内大型直剪仪，对不同剪切速率下粗粒土的强度和变形特性进行试验研究。试验数据表明：不同剪切速率时的剪应力-剪切位移曲线均呈应变软化型；剪切速率为小于5 mm/min时，粗粒土强度理论公式拟合相关系数比较理想；随剪切速率的增加，内摩擦角有减小的趋势，约在27.8°～22.8°内变化，咬合力在90.3～112.2 kPa范围内振动变化；颗粒破碎率和最大垂直变形随着剪切速率减小或垂直压力增加而增大，即剪切速率越小越容易发生剪缩；剪切速率小而抗剪强度高的本质原因是：破碎后的细颗粒填充了由粗颗粒构成的土骨架孔隙，造成试样的密实度增加。

Effects of shear rate on shear strength and deformation characteristics of coarse-grained soils in large-scale direct shear tests

The strength and deformation of soils play an important role in the stability of slopes and subgrades. In order to analyze the influence of shear rate on shear strength and deformation characteristics of coarse-grained soils, the strength and deformation of coarse-grained soils under different shear rates are investigated by use of the THE-1000 lab large-scale direct shear apparatus. The experimental results indicate that the curves of shear stress versus shear displacement present themselves to be strain-softening ones under different shear rates. While the samples are sheared at the rate lower than 5 mm/min, the correlation coefficient is ideal. With the increase of the shear rate, the internal friction angle tends to decrease and ranges from 27.8° to 22.8°, and the interlocking force changes in the range between 90.30 to110.2 kPa. The breakage ratio and the maximum amount of shrinkage increase with the decrease of the shear rate or the increases of vertical stress. In other words, shrinkage occurs easily under a low shear rate. The essential reason why the shear strength shows a high value under a low shear rate is that the broken pieces of coarse particles fill the pores, which consist of the coarse particles, resulting in the increase of density of the soil samples.