天然和饱水状态B类角砾岩的力学性质及其对地下厂房稳定性的影响

 从现场勘查、室内试验和数值计算的角度对某厂房出露的B类角砾岩的岩体特性、力学性质与开挖卸荷后围岩稳定性做系统的分析。室内试验结果表明，0～15 MPa围压下B类角砾岩表现典型的弹脆塑性；饱水试样在相对较高围压下加载时，试样的变形趋于均匀化，此时弹性模量不再随围压增大而增大。峰值强度的离散性较大，这是由于试样中方解石含量不同，随方解石含量增大，试样峰值强度增大；饱水状态试样较天然状态内摩擦角小而黏聚力大，体现水对角砾岩黏结强度的提高和内摩擦因数的弱化作用；利用角砾岩区域的三维数值模型计算得到开挖卸荷条件下B类角砾岩区域围岩的基本力学响应。计算结果与现场监测数据吻合较好。经过对B类角砾岩出露区域系统地加强支护，确保了施工期角砾岩区域的稳定性。

Mechanical property of B-type breccia under both natural and saturated state and its influence on the stability of underground powerhouse

The field investigation，laboratory experiment and numerical computation were carried out to systematically analyze the B-type breccia from a hydropower station. The laboratory test results indicated that the B-type breccia exhibits typical elasto-brittle-plastic feature under the confining pressures of 0–15 MPa. The specimen deformation tended to be uniform under relatively high confining pressure. Therefore，the elastic modulus had little relationship with the confining pressure. Due to the different calcite contents in the specimens，the peak strengths of the specimens differed markedly. Peak strength increased with the increasement of calcite contents. Compared with natural specimens，the internal friction angle of saturated specimens increased while cohesion decreases，which illustrated that water strengthened the bonding effect and weakened the internal friction coefficient；Three-dimensional numerical model including breccia mass was established. Mechanical response of B-type breccia under excavation was obtained through numerical computation. The numerical computation results fit well with monitoring data. It indicated that the surrounding rock was steady after systematic reinforced support have been set.