非绕轴对称岩质巷道的收敛约束法及支护优化研究

The classical tunnel convergence-confinement method is based on the rotationally symmetric condition, which represents that a circular tunnel is subjected to uniform in-situ stress. However, many instances in practical engineering are non-rotationally symmetry, such as the coefficient of lateral pressure being smaller than 1 as well as non-circular tunnel geometry, and thus the supporting structure is poorly designed. The primary objective of this project is to extend the classical tunnel convergence-confinement method to the non-rotationally symmetric condition. A theoretical solution of ground reaction curve is firstly presented by considering the integrated effects of five parameters. Laboratory model tests of non-rotationally symmetric tunnel excavation are simultaneously carried out, including two cases: the circular tunnels with unequal in-situ stress and the straight wall-arch tunnels with uniform in-situ stress, to measure the changes of wall displacement, interior displacement and rock pressure with the excavation distance. Then, 3D numerical models of non-rotationally symmetric tunnel are established using FLAC3D to simulate the excavation process of model tests and are verified by the model test results, and more numerical complementary tests are performed with different situations. The different spatial effects of tunnel face attributed to different non-rotationally symmetric factors are investigated with both the model tests and numerical simulations. Finally, a new formulation for the displacement relief coefficient under non-rotationally symmetric condition is derived and its applications to the support optimization design for different parts and different support times. The safety evaluation of tunnel support is discussed on both strength and deformation. This study can obtain a series of originally new results, which has innovative and scientific significance in theory as well as a good application prospect and economic benefits in engineering practice.

经典收敛约束法以圆形巷道受均匀地应力作用即绕轴对称条件为基础，与实际侧压力系数不等于1、非圆断面等工程实践明显不符，易造成支护结构设计不当。本项目拟对经典收敛约束法进行非绕轴对称拓展研究，首先构建综合5种因素影响的非绕轴对称围岩特征曲线的理论解答，同时开展室内非绕轴对巷道开挖模型试验，包括两种情况：圆形巷道受不等地应力、直墙圆拱巷道受等值地应力，测得洞壁及深部位移和围岩压力随开挖面距离的变化规律，进而利用FLAC3D软件建立非绕轴对巷道开挖三维模型，对模型试验过程进行模拟并比较验证，继而改变条件开展数值模拟补充试验，继而结合模型试验与数值模拟结果探讨不同非绕轴对称因素对开挖面空间效应的影响差异，建立非绕轴对称位移释放系数的新公式，并对不同部位与时机下的支护进行优化设计与安全性评价。本研究可取得一系列独创性成果，在理论上具有较好的创新性和科学意义，在工程实践中具有良好的应用前景和经济效益。

经典收敛约束法以圆形巷道受均匀地应力作用即绕轴对称条件为基础，与实际侧压力系数不等于1、非圆断面等工程实践明显不符，易造成支护结构设计不当。本项目采用理论分析、室内试验、现场实测与数值模拟相结合的方法，对经典绕轴对称条件下巷道的收敛约束法进行了拓展，主要研究内容及结论如下：.(1) 根据软岩流变控制原则和统一强度理论，推导两种稳定蠕变准则下巷道最优支护力和围岩允许最大位移的理论解答，给出公式适用条件、应用步骤。所得公式表达简洁、参数易确定，并得到两个工程实例的验证，具有良好的工程应用前景。.(2) 针对非绕轴对称地应力条件，构建圆形巷道的各种塑性统一解，包括塑性区应力、塑性区位移、塑性区半径和围岩特征曲线，能合理反映地应力分布、中间主应力效应和围岩剪胀特性的综合影响，具有一定理论意义和广泛工程应用潜力。.(3) 通过室内不同饱水情况下IV级围岩单轴和三轴强度试验，研究软岩在天然地下水与地应力耦合作用下的强度变化，获得了该类软岩峰值强度、残余强度、内摩擦角、粘聚力以及弹性模量等的变化规律。.(4) 以陈斜岭隧道、凝灰软岩隧道、黄枫隧道为工程背景，开展现场监测与Midas-GTS/FLAC3D开挖数值模拟，摸清了围岩变形的动态演化规律和不同工况下隧道位移与应力的变化特征，对不同部位与时机下的支护进行优化设计与安全性评价，获得了非绕轴对称巷道的变形实证。.本项目所取得的系列化创新成果不仅完善了收敛约束法的理论基础，推进其在巷道工程设计和施工中的进一步应用，而且能准确确定支护压力和支护合理选型，大幅度降低工程造价，具有很好的经济效益和社会效益。