岩体高应力损伤史影响围岩支护的机理研究

Study on the Mechanisms of the Influence of Rock Mass with Previous Highstress Damage on Surrounding Rock Supports

断层带岩体存在裂隙和高应力损伤历史的特点。为了探究隧道穿越断层带时,具有高应力损伤史的岩体在开挖后的力学特性及其对支护的影响,设计了两种卸荷路径不同的离散元数值模型:一种是峰前卸荷,反映普通隧道开挖;另一种是峰后卸荷,反映断层带内具有高应力损伤历史岩体中的隧道开挖。通过白砂岩试样的三轴压缩物理试验,标定了离散元模型的计算参数,然后通过数值计算对比研究两种卸荷路径下的围岩力学行为。结果表明,有高应力损伤历史的围岩在开挖卸荷后,自承载能力崩溃更快,因此要求支护更加及时;要控制到相同的围岩变形量,峰后卸荷工况所需的支护强度显著增大,更难以支护的细观机理在于拉伸微裂纹的显著发育。

The rock mass in the fault zone is characterized by fissures and previous high-stress damage. To explore the mechanical property of rock mass with high-stress previous damage after excavation when a tunnel passes through a fault zone and its impact on supports, different discrete element numerical models of two unloading paths are designed: pre-peak unloading, reflecting the excavation of ordinary tunnels;post-peak unloading, reflecting the excavation of tunnels in the rock mass with high-stress previous damage in a fault zone. The calculation parameters of discrete element models are calibrated through the triaxial compression test of white sandstone samples, and then numerical calculations are conducted to compare and study the mechanical behaviors of surrounding rocks in these two unloading paths. The results show that the self-bearing capacity of the surrounding rock with high-stress previous damage collapses at a faster speed after excavation-induced unloading, so supports shall be provided more timely;the support strength required is significantly increased to achieve the identical amount of deformation of surrounding rock;and it is more difficult to support the micromechanism for the significant development of tensile microcracks.