高地应力深埋软弱围岩隧道大变形机理及施工力学特性研究

During the construction of deep-buried weak surrounding rock tunnel with high geostress, the disasters such as large deformation, boundary encroachment, collapses, are prone to occur, which will cause casualties, cost out of control, schedule delay. Focusing on the problems above, and in order to clarify large deformation mechanism of weak surrounding rock tunnel with high geostress, and to reveal its mechanical properties during the construction, this project is planning to take the methods of theoretical analysis, laboratory tests, field tests and numerical simulation, considering the engineering mechanical properties of weak surrounding rock with high geostress, and applying the theories of nonlinear and viscoelastic plastic. First, collect the engineering examples of weak surrounding rock tunnels domestic and abroad, analyze and summarize the engineering mechanical properties and deformation features of the weak surrounding rock. Second, select typical relying project, gather rock samples of weak surrounding rocks, and carry out the laboratory tests, to build nonlinear and viscoelastic mechanical constitutive models of weak surrounding rock. Then, based on the field tests results and geological conditions of relying project, carry out three-dimensional numerical simulation of the weak surrounding rock tunnel construction process, explore the evolution law of advance displacement at the working face, extrusion deformation at the working face and backward displacement during the tunnel construction. At last, combining with the results of theoretical analysis, field tests, and numerical simulation, reveal the large deformation mechanism of weak surrounding rock tunnel with high geostress, and determine the construction mechanical properties. These research achievements are of great significance to large deformation disasters prevention for deep-buried weak surrounding rock tunnel.

高地应力深埋软弱围岩隧道在施工中极易发生大变形、侵限、塌方等灾害，导致人员伤亡，造价失控，工期延误。针对上述问题，本项目拟采用理论分析、室内试验、现场试验和数值模拟等方法，考虑高地应力软弱围岩的工程力学特性，运用非线性、黏弹塑性理论等，阐明高地应力软弱围岩隧道大变形机理，揭示其施工力学特性。首先，搜集国内外软弱围岩隧道的工程实例，分析和总结软弱围岩的工程力学特性和变形特征。其次，选取典型依托工程，采集软弱围岩岩样，开展室内试验，建立软弱围岩的非线性黏塑性力学本构模型。然后，基于室内试验结果和依托工程既有地质情况，开展软弱围岩隧道施工过程三维数值模拟，探寻隧道施工过程中掌子面先行位移、掌子面挤出变形及后方位移的演化规律。最后，结合理论分析、现场试验和数值模拟结果，揭示高地应力软弱围岩隧道大变形机理，明确施工力学特性。研究成果对深埋软弱围岩隧道大变形灾害防治具有重要意义。

高地应力软岩隧道施工常常发生大变形，造成支护变形侵限、喷射混凝土开裂剥落、钢架扭曲断裂、二次衬砌开裂掉块甚至垮塌，导致工期延误、费用剧增、安全失控。本项目以隧道工程为背景，首先选取典型的依托工程宝汉高速连城山隧道，开展了现场原位测试，获取了依托工程岩体的物理力学参数，得到了依托工程岩体的工程力学特性；其次开展了软弱围岩隧道施工过程的三维数值模拟，提示了隧道施工过程中掌子面先行位移、掌子面挤出变形及后方位移的演化规律。结果表明，掌子面前方至后方一定范围内的产生了拱顶下沉现象，掌子面正上方亦产生一定量的瞬时初始位移，约为最终位移值的40%，在隧道掌子面前方约1倍洞径范围内，产生了先行位移；隧道和周边位移径向影响范围在3倍洞径以内，水平位移主要产生于下台阶和落底的开挖，纵深影响范围约为掌子面后方2倍洞径，隧道掘进的纵深影响范围为：掌子面前方1倍洞径左右，后方约2倍洞径左右；软弱围岩隧道施工过程中，围岩的流变特性不容忽视。研究成果对深埋软弱围岩隧道大变形灾害防治具有重要意义。