冲击载荷下砂岩强度特性及破坏规律研究

为了研究砂岩的强度特性以及破坏规律,利用分离式Hopkinson装置对砂岩巴西圆盘进行不同冲击速度的动态劈裂试验,并利用三维非线性动力学分析软件LS-DYNA模拟这一劈裂过程。通过对试验所得应力应变曲线与模拟所得应力应变曲线的对比,确定数值模型的有效性。结合试验结果以及模拟结果可以得出,总体上砂岩的动态抗拉强度随着平均应变率的增大而增大,但并不是线性关系,而是当平均应变率低于某一值时,动态抗拉强度随着平均应变率的增加急剧增大,当平均应变率高于这一值时,动态抗拉强度随着平均应变率的增加而缓慢的增加;在动态劈裂过程中,砂岩巴西圆盘的破坏并不都是从中心位置起裂的,初始起裂位置与平均应变率的大小有关,当平均应变率小于某一值时,初始起裂位置在靠近入射杆一端,当平均应变率大于某一值时,初始起裂位置在靠近透射杆一端;砂岩试件的总体破坏顺序是由靠近入射杆端或者靠近透射杆端向中间位置扩展,同时由试件表面向内部扩展,最终上下表面导通,试件被劈裂成两半。

Research on Strength Properties and Failure Law of Sandstone under Impact Loading

In order to study the dynamic tensile strength and failure regularity of sandstone, a dynamic splitting test under different velocity was performed on Brazilian disk of sandstone by using separate Hopkinson device, and the 3D nonlinear dynamic analysis software LS-DYNA was used to simulate the splitting process. The validity of the numerical model can be verified through the consistency of experimental stress-strain curve and simulated stress-strain curve. Combined the experimental results with the simulation results, it indicates that the dynamic tensile strength of sandstone is increased with the increasing of average strain rate, but they are not in linear relationship. When the average strain rate is less than a certain value, the dynamic tensile strength increases sharply with the increasing of average strain rate, and if the average strain rate is higher than the value, the dynamic tensile strength increases slowly with the increasing of average strain rate. In the process of dynamic splitting, the initial crack location of sandstone Brazil disk is not totally occurred from the center, it is related to the average strain rate. When the average strain rate is less than a certain value, the initial crack location is near the end of the incident bar, when the average strain rate is higher than another certain value, the initial crack location is near the end of the transmission bar. The failure sequence of sandstone Brazilian disk is expanded from the location near the end of the incident bar or near the end of the transmission bar to the center of specimen, and at the same time, the crack expands from the surface to the internal, leading to the upper and lower surface conduction, finally, the specimen is split into two parts.