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针对深部高地应力条件下巷道开挖卸荷造成的围岩强烈扰动问题,基于弹性卸荷理论,运用留数定理和拉氏逆变换的延滞性给出动态开挖卸荷应力解析解。在此基础上,研究深部开挖卸荷下围岩力学特征和破坏机理,根据围岩力学特征建立动态卸荷的强度准则和拉压损伤模型。通过算例探讨初始地应力、开挖半径、卸荷时间和岩体动态强度对围岩卸荷破坏与稳定的影响。结果表明:深部开挖卸荷下围岩力学特征主要表现为最小主应力卸荷、最大主应力集中,而主应力差的瞬间增大,诱发开挖面内裂隙扩展、贯通,形成由强及弱连续分布的破坏区,构成二次支护前维系围岩稳定的支撑结构。深部动态开挖卸荷下,初始地应力和开挖半径越大、卸荷时间越短,围岩损伤越严重,破坏范围越广,对围岩的扰动越强烈;而岩体动黏聚力和动摩擦角越大,围岩的破坏范围越小,围岩越稳定。分析结果对深入研究高地应下巷道开挖的破坏机制具有重要意义。
Aiming at the strong disturbance of surrounding rock caused by tunnel excavation unloading under the condition of deep high ground stress, the analytical solution of dynamic excavation unloading stress is given based on the theory of elastic unloading and the lag of logarithm transformation and Laplace inverse transform. Based on this, the mechanical characteristics and failure mechanism of surrounding rock under deep excavation and unloading are studied. According to the mechanical characteristics of surrounding rock, dynamic strength criterion and tension and compression damage model are established. The effects of initial stress, excavation radius, unloading time and dynamic strength of rock mass on the unloading failure and stability of surrounding rock are discussed by means of an example. The results show that the mechanical characteristics of the surrounding rock under deep excavation unloading mainly include the unloading of the minimum principal stress and the concentration of the maximum principal stress, but the instantaneous increase of the principal stress difference, which induces the fracture in the excavation to expand and penetrate, Weak continuous distribution of damaged areas, forming secondary support before the stability of the surrounding rock support structure. Under the condition of deep dynamic excavation and unloading, the initial stress and excavation radius is larger, the unloading time is shorter, the more serious the surrounding rock damage, the more extensive the damage, the stronger the disturbance to the surrounding rock. The dynamic cohesion And the larger the dynamic friction angle, the smaller the damage range of the surrounding rock, the more stable the surrounding rock. The results of the analysis are of great significance for further study of the failure mechanism of roadway excavation under high ground conditions.