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考虑隧洞瞬态开挖卸载并分析围岩的动态响应对研究其变形破坏机制非常重要。在静水压力圆形隧洞动态卸荷模型理论分析的基础上,采用FLAC3D的Fish语言开发了隧洞开挖动态卸载围岩响应模拟计算程序。验证算例模拟结果与理论结果对比,证明了程序的正确性,围岩的应力变化和体积应变增量均呈现由表及里的波浪型变化,能较好地模拟围岩的动态卸荷响应。根据Griffith强度准则计算得到的不同时刻围岩的损伤范围表明,考虑动态卸载时围岩的损伤区比采用静态分析要大。采用该程序分别模拟了不同卸载时间、卸载路径、隧洞形状、隧洞直径、地应力等条件下,隧洞动态卸载围岩的动态响应。结果表明,在卸载时间变短、先慢后快卸载路径、洞形为方形、洞径变大和地应力差值增大的条件下,隧道围岩内最大、最小主应力应力差也增大。深部隧洞采用瞬态卸载分析对于深入研究围岩变形破坏机制具有重要意义。
Considering the tunnel transient excavation unloading and analyzing the dynamic response of the surrounding rock is very important for studying its deformation and failure mechanism. Based on the theoretical analysis of dynamic unloading model of hydrostatic circular tunnel, the simulation program of dynamic response to surrounding rock excavation was developed by using FLAC3D’s Fish language. The simulation results verify that the correctness of the program is verified. The stress and volumetric increment of surrounding rock show the variation of wave form from surface to interior, which can well simulate the dynamic unloading response of surrounding rock . The damage range of surrounding rock calculated at different times according to Griffith’s strength criterion shows that the damage zone of surrounding rock is larger than that of static analysis considering dynamic unloading. The program simulates the dynamic response of surrounding rock unloaded dynamically under different conditions such as unloading time, unloading path, tunnel shape, tunnel diameter and ground stress. The results show that under the conditions of shorter unloading time, slower initial unloading path, square hole shape, bigger hole diameter and greater difference of ground stress, the maximum and minimum principal stress stress difference in tunnel surrounding rock also increases. The analysis of deep tunnel using transient unloading is of great significance for further study on the deformation and failure mechanism of surrounding rock.