不同地应力条件下楔形掏槽爆破的岩石损伤演化过程研究

Evolution of Rock Damage Caused by Wedge Cut Blasting under Different Ground Stress Conditions

为解决掏槽爆破开挖困难的问题,以高速铁路隧道爆破工程入口段为例,设置多组静水地应力和非静水地应力加载工况,对楔形掏槽爆破过程进行数值模拟计算,分析不同地应力条件对岩石爆破裂纹扩展规律的影响。通过与实测数据进行对比,验证模型参数的合理性。结果表明:1)由于掏槽孔与自由面斜交,应力波叠加区压应力分量增大,使炮孔间内部岩石产生更大的压缩损伤;同时,远离炮孔处出现一定的裂纹,炮孔间靠近自由面部分岩体也出现拉伸损伤,有利于后续辅助孔的爆破。2)在静水地应力条件下,随着地应力增大,岩石爆破损伤演化受到抑制作用;在非静水地应力条件下,损伤范围沿最大主应力方向扩展,且槽腔水平裂纹与垂直裂纹的长度差异随侧压力系数减小而愈加显著。3)静水地应力场20 MPa范围内,楔形掏槽角度为60°左右时,岩石爆破效果受地应力的影响较小。

A case study is conducted on the entrance section of a high-speed railway tunnel blasting project to address the challenges expected during excavation by rock blasting, and multiple groups of hydrostatic and non-hydrostatic stress loading conditions are set up to numerically simulate the wedge cutting blasting process and analyze the influence of different ground stress conditions on the expansion of rockburst cracks. The rationality of the model parameters is validated by comparison with the measured data. The results reveal that:(1) The compressive stress component of the stress wave superposition area is higher because the section being cut is inclined to the free surface, resulting in greater compressive damage to the rock inside the holes. At the same time, cracks are generated at a distance from the hole, and part of the rock between the blast holes that is near the free surface suffers tensile damage, which is conducive to the blasting of the subsequent auxiliary holes.(2) Under hydrostatic stress conditions, the evolution of rock blasting damage is inhibited with an increase in ground stress, while under non-hydrostatic ground stress conditions, the extent of the damaged region expands along the direction of the maximum principal stress, and the difference between the lengths of the horizontal and vertical crack of the groove cavity becomes more pronounced with a decrease in the lateral pressure coefficient.(3) When the hydrostatic stress is around 20 MPa and the wedge cut angle is about 60°, the effect of rock blasting is less affected by the ground stress.