中文摘要：

选取云南虎跳峡龙蟠右岸地区分布的土石混合体，基于室内大型直剪仪对土石混合体进行不同剪切速率下的直剪试验。为消除大型直剪试验过程中实际剪切面积变化对试验结果的影响，建立基于圆形剪切盒剪应力的修正公式，在此基础上得到考虑与不考虑实际剪切面积变化影响的剪应力.剪切位移曲线。经过对比分析，发现相同剪切位移时，修正后剪应力比修正前有不同程度提高，随着剪切位移的增加，其提高程度也随之增大；用修正后的剪应力.剪切位移曲线获取的内摩擦角比用修正前的实验曲线获取的指标值偏大，而用修正后的实验曲线获取的黏聚力比用修正前的实验曲线获取的黏聚力偏小；剪切速率对峰值剪应力的影响随着法向应力的增大而愈加明显；不同剪切速率下内摩擦角有一定的差别，但总体趋势是随剪切速率增加而增大；而不同剪切速率下黏聚力差别较大，总体趋势是随着剪切速率的增加而减小。在此基础上，提出不同剪切速率条件下内摩擦角和黏聚力的计算公式，经过实例验证分析发现理论计算值和试验值误差较小，初步验证了该公式的有效性。

英文摘要：

Rock-soil aggregate on the right bank of Longpan in Tiger-leaping Gorge reservoir area were selected,and the direct shear test of rock-soil aggregate was carried out in four different shear rates by use of the large-scale direct shear apparatus.In order to quantitatively estimate the influence of sample area decreasing on the shear stress and strength parameters,the improved formula of shear stress and the normal stress in circular shear box was deduced.The conclusive results were obtained through comparative analysis.After modified by the improved formula,the results of shear stress are improved to different extents in the same shear displacement.The degree of improvement for shear stress increased as the shear displacement increased.After modification,cohesion and the angle of internal friction become smaller.The effect of shear rate on the peak shear stress becomes more obvious with the increase of normal stress.Internal friction angle changes with different shear rates.On the whole,internal friction angle increases with the increase of shear rates.However,cohesion has great differences in different shear rates.On the whole,Cohesion decreases with the increase of shear rates.The formulas of internal friction angle and cohesion in different shear rates were proposed.The validation experiment indicated that the experimental result agrees well with the predicted data calculated by the above formulas.Therefore,the effectiveness of the above formulas is proved.