崩积体剪切性能试验研究

崩积体是一种由土体和块石堆积形成的天然地质体，其内部结构特征在很大程度上控制着崩积体的物理力学特性。通过对崩积体进行现场实地踏勘，收集典型工点的崩积体试样，考虑原样级配，开展了对崩积体重塑样的室内大尺度直剪试验，获得了不同含石量、块石形状、土体性质以及应力状态下崩积体的剪应力-应变曲线与抗剪强度曲线，分析并探讨了其变形与强度特性变化规律及内在机制，首次提出了崩积体抗剪强度随含石量增长模式曲线。研究结果表明：崩积体剪应力-应变曲线较常规的单一介质有显著区别。在低法向应力下，崩积体表现为剪胀，而在高法向应力下，则表现为先剪缩后剪胀。崩积混合体的抗剪强度随含石量的增加经历了缓慢增长－快速增长－缓慢增长的过程，其内摩擦角增量与含石量（含黏性土崩积体为0～80%，含砂土崩积体为40%～80%）近似成线性增长的关系。相同含石量情况下，含不规则形状块石的崩积体内摩擦角显著高于含规则形状块石的混合体。

Experimental research on shear behavior of colluvium

Colluvium is a natural deposit of soil and rock.The physico-mechanical properties of colluvium are controlled to a large extent by its structure.On the basis of ground investigation and laboratory grading analysis,large scale direct shear tests on remoulded colluvium samples are carried out in laboratory.The shear stress-strain curves and shear strengths of colluvium with different rock particle contents,rock particle shapes,soil types and stress states are obtained.In addition,studies of the deformation and strength characteristics of colluvium are performed and a nonlinear increasing trend in shear strength of colluvium with respect to an increase in rock particle contents is first proposed.The results indicate that the shear stress-strain curve of colluvium is different from that of homogeneous soil or rock.Colluvium samples exhibit shear dilatation characteristics at low normal stress levels and tend to have a transformation from shear contraction to dilatation at higher stress levels.Overall,the shear strength of colluvium increases with increasing content of rock particles,for which the trend of increase is slow at first,and then becomes rapid,and slow down finally.The increment of internal friction angle increases linearly with the increase of the rock particle contents(0-80% for cohesive colluvium and 40%-80% for cohesionless colluvium).With the same content of rock particles,the internal friction angle of colluvium containing rock particles with irregular shape is higher than that composed of rock particles with regular shape.