基于岩体波速的地下洞室围岩损伤区岩体力学参数取值方法及工程应用

A method for determining mechanical parameter values of rock mass in the damage zone of surrounding rocks of underground caverns based on wave velocities of rock mass and its engineering application

地下洞室在爆破开挖以及在后期利用(如用于压气储能)过程中往往会在洞室围岩中形成一定深度和沿洞室边界环状分布的损伤区,研究地下洞室围岩损伤区内岩体力学参数的取值方法对地下洞室围岩稳定性分析和支护设计具有重要的意义。考虑岩体的地震波速度和声波速度,建立地下洞室围岩损伤区内地质强度指标GSI值和岩体扰动因子D值的计算公式,以及定量地确定扰动因子D值随地下洞室围岩损伤区深度的变化规律。引入Hoek-Brown强度准则,研究地下洞室围岩损伤区不同深度岩体力学参数取值方法。结果表明:提出的估算GSI和D值的方法能够很好地反映洞室在开挖爆破以及在后期利用过程中(如压气储能)损伤区内岩体力学参数随深度变化规律,损伤区岩体单轴抗压强度σ_(cm)所受弱化影响最为严重,而内摩擦角φ受到弱化影响最小;洞室围岩岩体波速类型可以分为3种:(1)凹型缓慢增长区+稳定波动区;(2)凸型缓慢增长区+稳定波动区;(3)直线型缓慢增长区+稳定波动区;在进行地下洞室损伤区围岩稳定性评估时,当所选择的数值模拟方法和本构关系允许时,应根据工程重要性选择损伤区间隔深度来建模,并且取分区内岩体波速测试平均值来确定岩体扰动因子D。研究成果可为类似地下洞室工程损伤区围岩稳定性评价与支护设计的岩体力学参数取值提供参考。

A damage zone that has a certain depth and is circularly distributed along the cavern boundary usually forms within the surrounding rocks of caverns in the excavation blasting and later utilization(for instance,compressed air energy storage) processes.Therefore,exploring a method for determining mechanical parametric values of rock masses inside the damage zone of the cavern surrounding rock is of significance to stability analysis and support design of surrounding rock in underground caverns.Considering the seismic wave velocity and acoustic velocity of rock masses,a formula for calculating the geological strength index GSI and rock mass disturbance factor D of rock mass in the damage zone of surrounding rocks of underground caverns was established.Changes in the disturbance factor D with the depth of damage zone in the surrounding rocks of underground caverns were quantitatively determined.Additionally,the Hoek-Brown strength criterion was introduced to study the determination method of mechanical parameter values of rock mass in the damage zone.The results show that the proposed calculation methods of GSI and D well reflect the change with the depth in the mechanical parameters of rock mass in the damage zone of caverns in the excavation blasting and later utilization(compressed air energy storage for instance) processes.The uniaxial compressive strengthσ_(cm) of rock mass in the damage zone is most seriously weakened while the internal friction angleφis least weakened.The wave velocities of surrounding rock mass of the cavern can be classified into three types:(1) concave-shaped slow increase area and stably fluctuating area;(2) convex-shaped slow increase area and stably fluctuating area;(3) linearly slow increase area and stably fluctuating area.When numerical simulation methods and constitutive relationship are allowed,the depth interval of the damage zone should be selected for modeling according to the degree of importance for engineering projects in the evaluation of the stability of surrounding rock in the damage zone of underground caverns.The rock mass disturbance factor D should be determined based on the tested average wave velocities of rock mass in sub-zones.The results provide reference for evaluating the stability of the surrounding rock mass in the damage zone in similar underground caverns and for determining mechanical parameter values of rock mass in support design.