软弱破碎围岩深埋隧道拱顶渐进性塌方机理及控制

隧道拱顶塌方事故是近年来隧道施工中造成重大人员伤亡的主要事故类型，危害极大，因此必须掌握隧道拱顶塌方发生机理和演化规律、制定科学有效的控制对策，为塌方事故的防治提供依据。基于上限变分法，建立深埋地层中隧道拱顶塌方模型，研究隧道拱顶塌方范围及其影响因素，进一步建立软弱破碎围岩隧道拱顶渐进性塌方模型，推导渐进性塌方范围全过程曲线，并与模型试验结果进行对比。据此提出了拱顶塌方事故的安全性控制措施，揭示预控制、过程控制两类措施下拱顶塌方安全性控制机理和承载特性，提出支护措施的围岩荷载确定方法。结果表明：隧道塌方宽度L随着初始粘聚力c0和单轴抗拉强度σt的增大而增大，随着重度γ和非线性系数m的增大而减小；隧道塌方高度h1随着抗拉强度σt和非线性系数m的增大而增大，随着初始粘聚力c0和围岩重度γ的增大而减小；基于渐进性塌方过程中围岩物理力学参数逐渐减弱的特性，建立了考虑围岩粘聚力和抗拉强度衰减的隧道拱顶渐进性塌方模型；根据控制机理和目标，将拱顶塌方控制措施分为预控制措施和过程控制措施；围岩的形变荷载和总荷载随着塌方荷载的增大而增大。相关研究成果将为隧道拱顶塌方的预测及安全性控制提供借鉴。

Progressive Collapse Mechanism and Safety Control of Deep Buried Tunnel Vault in Soft and Broken Surrounding Rock

Tunnel vault collapse is the main type of tunnel accident that has brought huge injuries and deaths. The causes and prevention of tunnel collapse have aroused great concern. Therefore, it is necessary to carry out profound research on the safety problems of tunnel vault collapse to master occurrence mechanism and evolution law of tunnel vault collapse, and formulate scientific and effective control measures which is hoped to provide basis for prevention and treatment of tunnel collapse. Using the upper limit variational method, the collapse prediction model of tunnel vault in deep overburden ground is put forward, and the influencing factors of tunnel vault collapse range is studied. The progressive collapse model of tunnel vault is further established, the whole process curve of collapse range is deduced which is compared with the model test results. Based on the progressive collapse characteristics of tunnel vault, the safety control principle and bearing mechanism of tunnel collapse with pre-control and process control measures are clarified. The method to determine the surrounding rock load of support measures is proposed. The following results are found. The width of tunnel collapse increases with initial cohesion and uniaxial tensile strength, however decreases with weight and the nonlinear coefficient. The height of Tunnel collapse increases with tensile strength and nonlinear coefficient, and decrease with initial cohesion and weight. Based on the characteristics that the mechanical parameters of surrounding rock gradually weaken during the progressive process of vault collapse, the progressive model of tunnel vault collapse considering the attenuation of cohesion and tensile strength is established. The control measures of vault collapse can be divided into pre-control and process control measures considering control mechanism and objectives. Both deformation load and total load of surrounding rock increase with the increase of collapse load. The relevant research results can provide reference for the prediction and safety control of tunnel vault collapse.