【作者】 杨峰；

【导师】 阳军生；

【作者基本信息】 中南大学 ， 桥梁与隧道工程， 2010， 博士

【摘要】 浅埋隧道围岩压力和稳定性问题对于隧道设计、施工和理论研究均具有重要意义。传统的极限平衡法和滑移线法在解决该问题时存在诸多困难。而有限元法在模拟隧道围岩失稳破坏时需进行大量的迭代计算,耗费机时且可能存在收敛问题。相比而言,极限分析上限法是解决该问题的有效途径。其中刚性滑块上限法针对特定问题具有计算量小、能快速得到上限解等特点。而上限有限元法无需假定破坏模式,又结合了有限元法的优势,对复杂边界条件的适应性较强。论文以这两种方法为主要研究手段,对不同参数条件下浅埋隧道围岩稳定性进行分析,主要研究内容如下：(1)探讨了传统的刚性滑块极限分析上限法的主要特点及适用性问题,对破坏模式和速度场的构建方法等问题进行讨论,分别构建了矩形隧道和掌子面纵向破坏模式,编制了计算程序,对隧道稳定性进行了分析。(2)基于线性规划模型的上限有限元基本理论,提出其计算流程,编制了隧道稳定性分析的二维上限有限元通用计算程序,调节网格划分和约束条件,即可实现复杂边界条件下的隧道围岩稳定性分析。通过计算经典的条形基础地基承载力算例,与已有精确解进行对比,验证程序的准确性。并探讨了上限有限元法的网格密度、网格形式、塑性乘子数目p等因素对计算结果精度的影响。(3)对于土体不排水条件,利用上限有限元得到了不同参数取值时单洞圆形隧道围岩稳定性系数的计算图表；而针对土体排水条件下单洞圆形隧道围岩稳定性,得到不同参数取值时的隧道支护反力系数Nγ、Ns、Nc的计算图表,计算结果与已有文献进行对比验证。(4)将强度折减法引入上限有限元,提出相应的计算流程,并通过算例得到浅埋隧道围岩稳定性安全系数。(5)根据上限法计算结果,总结了单洞浅埋隧道围岩破坏模式和影响因素。分析不同参数条件下隧道围岩破坏模式的形态特征和演变规律。(6)利用上限有限元法得到不同参数条件下的矩形隧道围岩压力和浅埋隧道掌子面支护反力系数Nγ和Ns,并与刚性滑块上限法计算结果进行对比验证。(7)针对并行隧道和偏压隧道,采用上限有限元法进行围岩稳定性分析,并对相应的破坏模式形态、范围、演化规律进行探讨,与地表水平条件下单洞隧道的破坏模式进行对比分析。(8)针对云阳山隧道亚粘土地层开挖施工过程中隧道围岩与支护结构的大变形和冒顶坍塌的实例,利用极限分析上限有限元法分析隧道围岩发生失稳破坏时的形态特征和破坏范围,验证本文方法的有效性和实用性。更多还原

【Abstract】 Shallow tunnel surrounding rock pressure calculation and stability analysis has great effect on tunnel design, construction and theory investigation. The traditional solutions of limit equilibrium and slip line methods have difficulties in solving such problems. When tunnel surrounding rock failure is simulated, finite element method has to perform large numbers of iterative calculation, which are time-consuming and would arise convergent problem. Compared to the above solutions, upper bound solution of limit analysis is an effective way. The rigid blocks upper bound solution can obtain results with little iterative calculation for specific problems. Finite element upper bound solution of limit analysis takes advantage of finite element method and has no need to assuming failure mechanism beforehand. Therefore, it is suitable for complicated boundary conditions. Based on the two upper bound solutions, the shallow tunnel surrounding rock stability under different parameters were calculated and analyzed. The main contents are detailed as following:(1) The main characteristics and applicability of traditional rigid blocks upper bound solution were discussed. And the method of constructing failure mechanism and its corresponding velocity field were also proposed. The failure mechanism of surrounding rock pressure of rectangular tunnel and shallow tunnel face stability were constructed, and the tunnel stability was analyzed using the compiled program.(2) Based on the fundamental theory of finite element upper bound solution with linear program, the calculation process was proposed and the two dimensional computer program of finite element upper bound was compiled, which can be used for tunnel stability analysis. And the complicated stability problem can also be performed with adjusting mesh and constrain condition. The bearing capacity of strip footing was calculated and compared with the existing exact solution to verify the compiled program. In addition, the impact of calculation accuracy of the dense and form of the mesh and the number of plastic multiplier were discussed.(3) Using finite element upper bound solution, the calculation chart of circular tunnel surround rock stability factor for undrained ground was obtained. And calculation chart of tunnel support pressure factor Nγ, Ns, Nc were also obtained for circular tunnel with various calculating parameters. The results were all compared with the existing data in literature.(4) The strength reduction method was introduced to finite element upper bound solution. And corresponding calculation process was proposed. The safety factor of shallow tunnel stability was obtained by numerical examples.(5) By using finite element upper bound solution, the failure mechanism and influence factors of shallow tunnel was discussed. And its characteristics and changing regulations for different parameters were summarized.(6) The surrounding rock pressure of rectangular tunnel and tunnel face support pressure factor Nγand Ns with different parameters were obtained using finite element upper bound solution. And the results were compared with rigid blocks upper bound solution.(7) For parallel and incline tunnel, the stability of surrounding rock and the characteristics, range and changing regulations of the failure mechanisms were analyzed and discussed. And the results were compared with shallow tunnel of level surface.(8) Based on the case study of failure of surrounding rock and support structure of Yun Yangshan tunnel in mild clay ground, the characteristics and range of failure mechanism was analyzed, so as to verify the validity and practicability of finite element upper bound solution.更多还原