寒区富水裂隙岩体隧道脱空衬砌裂损机理研究

For tunnels located in the cold regions, the voids behind lining and its induced lining crack problems were widespread, especially for the tunnels located in water-rich fractured rock mass, which threats the tunnel service life and the safety of vehicle operating seriously. The methods of laboratory experiment, theory analysis and numerical simulation based on the extended discrete element method would be used to study the frost heaving mechanism of single fracture filled with water, multi-physics couplings of fractured rock mass and catastrophe characteristics of lining with voids in sequence. Based on the results of freezing-loading test conducted using the rock samples with different single fracture filled with water, the deformation characteristics and frost heaving force corresponding evolution laws of the single fracture will be studied. The mechanical model of frost heaving force and crack criterion of fracture will be given. The governing equations of thermal field, hydrological field and mechanical field will be derived, respectively. Combining with the governing equations mentioned above, the thermo-hydro-mechanical coupled model will be proposed. Optimizing the numerical simulation based on the extended discrete element method, and combining with the model, the distribution characteristics and evolution laws for the thermal field, hydrological field and mechanical field of water-rich fractured rock mass will be well researched, under the effect of water migration, latent heat of phase change and hydro-mechanical coupling. Based on the mini physical model testing results, the deformation and mechanical response characteristics of lining with voids under the action of the frost heave load will be analyzed. The crack mechanism of cold regions tunnel lining with voids and its gradual catastrophe instability evolution laws will be revealed. The research achievements will provide a significant and scientific method to forecast, identify and prevent crack disaster for tunnel lining with voids located in cold regions.

寒区富水裂隙岩体冻胀诱发隧道脱空衬砌裂损问题普遍存在，严重威胁隧道结构长期服役性能和车辆运行安全。本项目拟采用室内试验、理论分析和扩展离散元模拟等手段，以单裂隙冻胀扩展-裂隙岩体多场耦合-脱空衬砌裂损失稳为主线，研究寒区富水裂隙岩体隧道脱空衬砌裂损机理。基于饱水单裂隙原岩试样冻结加载试验，分析裂隙冻胀变形特征与冻胀力演化规律，建立裂隙冻胀力学模型及其起裂扩展判据；推导富水裂隙岩体温度场、渗流场和应力场控制方程，构建低温相变裂隙岩体温度–渗流–应力多场耦合本构模型，优化裂隙岩体多场耦合扩展离散元数值分析方法，研究水热迁移、相变潜热和渗流耦合作用下岩体温度场、渗流场和应力场分布特征及变化规律；开展微型物理相似模型试验，分析冻胀荷载作用下脱空衬砌形变与力学响应特征，揭示裂损衬砌失稳灾变渐进性演化规律。为我国寒区隧道衬砌结构灾害预测、临灾判识与防控治理提供理论依据，具有重要的理论意义和科学价值。

我国交通基础建设逐步向高寒、高海拔地区转移，以川藏铁路为代表的大量寒区隧道工程正在规划和修建，数万公里寒区隧道工程正在或即将投入运营，然而寒区隧道运营过程中因衬砌开裂诱发的渗漏、挂冰甚至掉块等问题，给寒区隧道长期服役性能和车辆运行安全带来极大威胁。.本项目以灾害源（冻胀力）—孕灾体（裂隙富水围岩）—灾变体（脱空衬砌失稳灾变演化）为研究主线，重点围绕寒区富水裂隙岩体隧道脱空衬砌裂损机理的基础理论难题开展研究。取得的成果如下：基于国内外典型寒区隧道灾害的病害调查和特征与成因分析，系统梳理总结了隧道衬砌病害类型与特征，明确了寒区富水隧道衬砌背后积水和含水裂隙围岩圈冻胀附加荷载为主要的两种致灾因素；建立了裂隙冻胀力、外荷载与裂隙强度之间数学表征关系，建立了富水裂隙岩体冻胀扩展的起裂判据，推导了饱水裂隙岩体温度场、渗流场和应力场控制方程；基于自主研发的低温环境隧道模型试验装置，分别针对富水裂隙围岩和衬砌脱空工况，研究了多场耦合作用冻胀力分布规律及演化特征；通过考虑围岩含水率和比重指标，实现了冻胀力时-空演化规律理论表征，采用多元回归分析，建立围岩冻胀率与冻结圈厚度、含水率的拟合计算方程，建立平面应变状态下冻结圈围岩冻胀力理论解；通过数值仿真和相似模型试验方法，分析冻胀荷载作用下脱空衬砌形变与力学响应特征，利用声发射技术定量分析了衬砌裂纹由微损伤到宏观破坏全过程，揭示裂损衬砌失稳特征及灾变渐进性演化规律。项目研究成果有利于推动实现寒区富水隧道冻害诱发衬砌裂损灾变有效主动防控，降低寒区隧道运营风险，尤其对寒区富水隧道衬砌背后脱空积水冻害，具有理论价值与研究意义。