不同加载率作用下双材料巴西圆盘动态抗拉强度试验研究

水泥砂浆广泛应用于岩石工程中,如巷道锚喷支护及山体滑坡注浆加固等,由于温度变化,岩石与砂浆之间的过渡区容易形成微裂隙薄弱区,同时地下岩体结构又常常承受着动载荷的作用,如爆破、冲击及地震等,因此研究岩石与水泥砂浆界面过渡区(interface transition zone,ITZ)的强度及其破坏特征具有重要的意义。为此提出了岩石–砂浆双材料巴西圆盘构型,采用分离式霍普金森压杆系统对两种界面粗糙度(光滑和粗糙)的双材料巴西圆盘进行了冲击实验;同时,为了比较单一材料与双材料破坏性能的差异,还制备了单一花岗岩、砂岩和砂浆的巴西圆盘试样。为了克服双材料巴西圆盘的应力分布不均匀的问题,使用实验–数值法确定了其中心抗拉强度。并且,采用Python语言建立了两种试件批量嵌入cohesive单元的数值模型模拟双材料试件ITZ的失效过程。结果表明:(1)当动态加载率相同的条件下,双材料界面粗糙度对试件的应变率影响不大,但对试件抗拉强度影响较大;(2)相比于花岗岩–砂浆试件,界面粗糙度对砂岩–砂浆试件动态初始抗拉强度影响更大;(3)基于数值模型得出圆盘模型中心处存在切应力τ_xy,但拉...

Experimental study on dynamic tensile strength of bimaterial Brazilian disc under different loading rates

Mortar is widely used in rock engineering,such as mortar jet supporting tunnel and landslide grouting reinforcement.Due to the change of temperature,the interface transition zone between rock and mortar is easy to form the weak area of micro cracks.At the same time,the underground rock structure often bears the dynamic load such as blasting,impact and earthquake.Therefore,it is of great significance to study the strength and failure characteristics of the interface transition zone between rock and mortar.In this paper,a rock-mortar bimaterial Brazilian disk configuration is proposed,and the impact experiments of bimaterial Brazilian disk with two kinds of interface roughness(smoothness and roughness)are carried out by using the split Hopkinson compression bar system.At the same time,in order to compare the difference of failure performance between single material and bimaterial,Brazilian disc specimens of single granite,sandstone and mortar were also prepared.In order to overcome the problem of uneven stress distribution of the bimaterial Brazilian disc,the central tensile strength of the disc was determined by the experimental numerical method.In addition,two kinds of numerical models are built with Python language to simulate the failure process of bimaterial ITZ.The results show that,when the dynamic loading rate is the same,the interface roughness has little effect on the strain rate of the specimen but has a greater impact on the tensile strength of the specimen,and that,compared with the granite-mortar bimaterial specimen,the interface roughness has a greater impact on the dynamic initial tensile strength of the sandstone-mortar bimaterial specimen.It is also shown that,based on the numerical model,the shear stress τxy exists in the center of the disk model and is far less than the tensile stress σx,and that the failure phenomenon of the numerical model embedded with cohesive element are close to that of the test specimen,which verifies the effectiveness of the method.