富水隧道掌子面卸荷能量耗散损伤研究

Aimed at the practical needs of the project and many basic and applied research problems of the tunnel face stability to be solved, a study on rich water tunnel face damage due to unloading using energy dissipation principle was carried out, considering that the tunnel face excavation is actually unloading process, instability failure is a result of damage accumulation progressive failure, energy dissipation is the essential attributes of the destruction for it can reflect the internal micro-defects in the development of rock, the intensity of the continuous process of weakening and eventual failure. Combine unloading - seepage test and fracture mechanics analysis, damage evolution mechanism and energy dissipation law was explored, from microcrack nucleation to the growth of macroscopic crack and the failure of the materials. A coupling model of unloading - seepage - calculate damage was built based on the energy dissipation through the application of unloading rock mechanics, damage mechanics, energy dissipation theory. Numerical methods of solving the model is established using the secondary development of large-scale simulation software. Relying on rich water tunnel engineering, the distribution of energy dissipation characteristics and influence of the damage of rich water tunnel face when unloading was discovered using the model. Considering the impact of the formation parameters of spatial variability and randomness, random damage and random energy dissipation of the tunnel face was researched using the theory of probability theory and mathematical statistics. This project can provides a new thinking and new methods for the analysis of the tunnel face instability and the reinforcement.

瞄准掌子面稳定性研究有很多基础和应用问题亟待解决及工程现实需求，抓住掌子面开挖实际是卸荷的过程，失稳破坏是一个损伤累积渐进破坏的结果，能量耗散可以反映掌子面围岩内部微缺陷不断发展、强度不断弱化并最终丧失的过程，是掌子面失稳破坏的本质属性的关键，开展富水隧道掌子面卸荷能量耗散损伤研究；结合卸荷-渗流试验、断裂力学等分析，探索围岩从微裂纹成核、扩展、汇合，到宏观裂纹萌生、扩展，到失稳破坏全过程的渐进破损演化机理与能量耗散规律；应用卸荷岩体力学、损伤力学、能量耗散等理论，构建基于能量耗散的卸荷-渗流-损伤耦合计算模型；研究模型数值计算方法及在大型仿真软件中的二次开发；依托富水隧道工程实际，探明富水隧道掌子面卸荷时能量耗散与损伤的分布性状及影响规律；考虑地层参数空间变异性和随机性的影响，结合概率论和数理统计理论，研究掌子面围岩随机损伤和随机能量耗散，为掌子面失稳与加固分析提供一个新思路和新方法.

随着新一轮西部大开发和城市发展，会有很多山岭隧道和城市隧道修建，其中很多是在富水地层。掌子面附近围岩稳定性是软弱破碎段富水隧道及水下隧道施工面临的关键问题和核心控制因素，很多基础和应用问题亟待解决。本项目分析了富水隧道掌子面开挖卸荷损伤的影响因素及作用规律，统计分析了掌子面坍方形态以及影响因素。通过鲁宾涅特公式，讨论了不良地质条件、地下水、地应力、施工方法以及现场施工管理水平对隧道掌子面稳定性的影响。现场取样，建立了基于软化系数和Hoek-Brown准则获取不同饱和度下围岩力学参数的方法；推导了不同富水程度下围岩随机分布损伤的演化方程。构建了不同富水及饱水时间下掌子面稳定系数计算方法，获得了不同富水下和饱水时间下掌子面的稳定系数，随着饱和度的增加，虚拟支护力增大，掌子面安全系数降低。推导了不同卸荷水平掌子面的稳定性，随着卸荷水平增大，掌子面安全系数整体降低；曲线呈现前陡后缓，卸荷水平对掌子面稳定安全性影响呈现非线性特征，应重视早支护对掌子面围岩稳定的作用。应用开发的模型，并基于流固耦合原理，模拟分析了掌子面在不同地下水位、支护时机对掌子面稳定性的影响，获得了掌子面损伤分布情况，以及掌子面不同路径以及不同参考点的能量耗散情况；进而模拟分析了不同进尺下掌子面的稳定性，并同极限分析做了对比分析，进尺对稳定性的影响呈现非线性特征，整体上随着进尺的增大；进尺过长，不仅会造成掌子面坍方，还会引起开挖段坍方。掌子面附近为应力降低区，即卸荷区；掌子面前方一段距离为应力升高区，即应力承载区，也是拱效应发挥地段；掌子面较远处，为原岩应力区。研发了富水隧道施工安全风险管理软件，该系统可以确定不同围岩地段的围岩压力、涌水量、支护抗力，判断支护结构是否安全。研究成果为富水隧道掌子面的稳定提供了重要的参考。课题组团队发表论文13篇；获得授权实用新型专利7项，授权发明专利2项；取得软件著作权1个。