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以内蒙古金盆湾大跨软岩隧道为工程背景,通过现场监测及数值分析,探讨围岩拱顶沉降、钢支撑内力、围岩与初期支护之间的内力、初期支护与二衬之间的内力随时间及开挖距离的变化规律,并用现有的理论及方法对其进行围岩稳定性分析。研究结果表明:对拱顶沉降数据的拟合函数进行求导分析并判定出围岩的稳定状况良好;围岩和初期支护压力在距离上台阶开挖面65 m后逐渐稳定;钢支撑外侧应力平均值大于内侧应力,最大应力值小于钢拱架的屈服强度,开挖过程安全级别始终处于安全或者基本安全状态;初衬和二衬间的接触应力在二衬浇筑后2天左右达到最大值,随后减小趋于稳定,且稳定值都小于0.1 MPa;数值模拟的围岩变形规律和实测围岩的变形规律相同且沉降实测值与模拟值差别不大,证明了模型的合理性。研究结论可为类似条件下工程的设计、施工和监测提供指导。
Taking the Jinpen Bay large-span soft-rock tunnel in Inner Mongolia as an example, through on-site monitoring and numerical analysis, discussion is made on the settlement of surrounding rock vault, the internal force of steel support, the internal force between surrounding rock and initial support, Between the internal forces with time and excavation distance variation law, and use the existing theory and method of rock stability analysis. The results show that the fitting function of the vault settlement data is analyzed and the stability of the surrounding rock is determined. The surrounding rock and the initial support pressure gradually stabilize at a distance of 65 m from the excavation face of the upper step. The outer side of the steel support The average stress is greater than the internal stress, the maximum stress value is less than the yield strength of steel arch, the safety level of the excavation process is always in a safe or basically safe condition; the contact stress between the first liner and the second liner reaches the maximum about 2 days after the second liner is poured Value, then decrease to stabilize, and the stability values are all less than 0.1 MPa. The numerical simulation of the surrounding rock deformation law and the measured deformation of the surrounding rock are the same, and the difference between the measured and simulated values is not large, which proves the rationality of the model. The conclusions of the study can provide guidance for the design, construction and monitoring of a project under similar conditions.