水泥胶结颗粒的微观力学模型试验

Experimental investigation on micromechanical model of cement-bonded particles

土体粒间胶结是建立天然结构性土本构模型的决定性因素之一,将胶结颗粒理想化为两铝棒,在指定位置处形成胶结。采用水泥作为胶结材料,对胶结颗粒进行了一系列简单加载试验(包括拉伸、压缩、压剪、压扭)和复杂应力路径试验,并与蒋明镜等所做的环氧树脂胶结试验进行对比。结果表明:胶结材料对胶结颗粒的力学性能存在一定影响,但基本规律符合蒋明镜等所提出的理想颗粒间胶结模型。水泥胶结抗拉强度低于环氧树脂胶结抗拉强度,但延性相对较好,抗压特性均呈塑性软化现象;二者的抗剪强度初始均随法向压力的增加而增大,当法向压力超过一定值时,又随法向压力的增加而减小(该压力称为界限法向压力),但水泥胶结的界限法向压力明显高于环氧树脂胶结,扭转试验规律与剪切试验规律类似。在三维应力空间中(法向压力-扭矩-剪力)水泥胶结的强度包线呈橄榄球状,环氧树脂胶结强度包线呈水滴状。

Bond between particles has become one of the key factors in establishing the constitutive model of natural sands.In this paper,the bonded granulates are idealized by two aluminum rods glued together by cement with cement water ratio 0.34,and the micromechanical responses of the bonded rods are investigated by performing a series of loading tests,such as tension tests,compression tests,shear tests,rotation tests and complex stress path tests.Then the comparison between the present results and the experimental data acquired on the epoxy resin adhesive by Jiang et al.,is carried out to analyze the effect of bonding materials.The results show that the mechanical behaviors of cement and epoxy resin bonded rods both satisfy the same micro-contact laws proposed by Jiang et al.in spite of some distinct differences between the two kinds of bond materials.The tension and compression strengths of cement are lower while the ductility is better than those of epoxy resin.Both cement and epoxy resin bonded rods present plastic-softening property in compression tests.In the shear and torsion tests,shearing force and torque initially increase with the normal force until a critical normal force is reached,and then gradually decrease.The strength envelope in the normal-torsion-shear space is a rugby and water-drop shell for the cement and epoxy resin adhesive,respectively.