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由于爆破开挖,巷道内常含有径向裂隙,并影响巷道的稳定性,为了详细地研究含径向裂纹巷道在冲击载荷作用下的动态断裂行为,采用砂岩材料制作巷道模型试样进行中低速冲击动态断裂试验,并采用AUTODYN有限差分软件进行数值模拟分析。分析巷道对称轴线上的径向裂纹在冲击荷载作用下的扩展特性及止裂现象,并采用试验–数值–解析法计算出裂纹的起裂韧度及扩展速度等参数。研究结果表明:(1)巷道围岩在静力载荷作用和动力载荷作用下的破坏行为有较大差异,动力载荷下破坏仅是裂纹尖端处的起裂、扩展;而静力载荷下破坏除了发生在裂纹尖端处,也会在巷道拱肩、拱脚及两侧帮处发生破坏。(2)巷道对称轴线上的裂纹在冲击载荷下的扩展路径大致沿着裂纹的原方向扩展,扩展路径中存在明显的止裂现象。(3)采用试验–数值–解析法能够较好地计算出裂纹的起裂速度及扩展速度,进一步采用位移外推法能够求解出巷道内裂纹的动态应力强度因子时程曲线,利用测试的裂纹起裂时间确定起裂韧度。
In order to study the dynamic fracture behavior of roadway with radial cracks under impact load in detail, the roadway model samples are made of medium and low speed Impact dynamic fracture test, and the use of AUTODYN finite difference software for numerical simulation. The expansion characteristics and crack arrest of radial cracks on symmetry axis of tunnel under impact load were analyzed. Parameters of initiation fracture toughness and propagation velocity of crack were calculated by the test-numerical-analytical method. The results show that: (1) The failure behavior of surrounding rock in roadway under static load and dynamic load is quite different. The failure under dynamic load is only the crack initiation and propagation at the crack tip; except for the failure under static load Occurred at the tip of the crack, but also in the roadway arch, arch foot and both sides of the gang Department of damage occurred. (2) The crack propagation along the symmetry axis of the roadway expands along the original direction of the crack under the impact load, and there is a clear crack arrest in the expansion path. (3) The crack initiation and propagation velocities can be well calculated by the test-numerical-analytical method. The displacement extrapolation method can be used to solve the dynamic stress intensity factor time-history curve of the crack in the roadway. Starting time to determine the starting fracture toughness.