砂质卵砾石力学行为与颗粒破碎的试验研究

荷载作用下粒状岩土材料的颗粒破碎改变了颗粒组构,从而影响其力学特性。为了揭示颗粒破碎对抗剪强度的影响,利用大型真三轴进行一系列不同应力路径的剪切试验,阐述产生不同颗粒破碎形态的破碎机制;论证颗粒破碎是粗粒土抗剪强度非线性变化的重要影响因素,并建立幂函数拟合强度公式。引入由粗粒土非线性强度曲线与线性临界状态线围成面积和线性临界状态线随平均球应力变化面积之比定义的强度因子,描述颗粒破碎对子午平面内临界状态线的影响。强度因子越大,子午平面内临界状态线的非线性变化越突出;平均球应力越大,颗粒破碎对强度变化规律的影响越大。筛分试验结果表明,Marsal颗粒破碎指标与强度因子呈指数关系;粒径大于1 mm颗粒的破碎率随平均主应力的增大而增大,小于1 mm颗粒的破碎率随平均主应力的增大反而衰减的变化规律,内摩擦角与咬合强度随破碎率变化表现出一定的相关性。

Experimental study on mechanical behaviors and particle breakage of sandy gravel

The particle breakage of granular geomaterials under loading alters the particle composition and further affects their mechanical properties.In order to reveal the effect of particle breakage on shear strength characteristics,a series of true triaxial shearing tests with different stress paths on sandy gravel were carried out by using a large true triaxial apparatus,and the breakage mechanisms of different particle breakage patterns were described.It is revealed that particle breakage is an important factor for the nonlinearity of the shear strength.A power function fitting strength formula was established and the non-linear shear strength indexes were calculated.The influence of particle breakage on the critical state line in meridian plane was described by introducing the strength factor,which is defined by the ratio of the area enclosed by the non-linear strength curve and the linear critical state line to the area under the linear critical state line.The larger the strength factor,the more significant the nonlinear characteristic of the critical state line in meridian plane,and the larger the mean spherical stress,the greater the impact of particle breakage on the shear strength.The sieving results show that the particle breakage rate by Marsal is exponentially related to the strength factor.The variation rules of the internal friction angle and interlocking strength with the index of fine-grained breakage were sorted out.It is shown that the particle breakage rates of particles larger than and less than 1 mm respectively increase and decrease with increasing the mean principal stress.The internal friction angle and occlusion strength show a certain correlation with the change of the breakage rate.