爆破与开挖瞬态卸荷双重动力扰动下岩溶隧道掌子面突水灾变机理研究

Water inrush has become a major security challenge in the construction of karst tunnel in China. This research is intended to take the frequent occurrence of water inrush for working face in karst tunnel excavated by the drilling and blasting method as the engineering background. it is found that dual dynamic disturbance induced by blasting and transient unloading of excavation is an important inducement to water inrush of tunnel face. Firstly, based on investigation analysis and classification statistics of massive cases of water inrush for karst tunnel face, the typical structures of rock mass to prevent water inrush ahead of tunnel face are concluded from the view of hydraulic properties of rock mass. Then, the model tests are carried out to present the instability styles of water inrush corresponding to the typical structures of rock mass ahead of tunnel face coupled by structures of water-resisting strata ahead of tunnel face, initial in-situ stress, karst water pressure and damage degree by blasting excavation. The macroscopic fracture mechanism of water inrush for rock mass in front of tunnel face base on results of physical model tests. 3D DEM-CFD of dynamic simulation is established considering the coupling dynamic effect of blasting and transient unloading. The evolution law of rock mass in front of tunnel face fracture, the formation process of bursting water channel and flow state conversion are illustrated under the engineering disturbance from meso level by this numerical simulation method. Subsequently, the critical feature information of instability due to water inrush of tunnel face is achieved, meantime, the dynamic instability criterion and the method to determine water-resisting thickness of rock mass are built on the basis the results of model tests and numerical simulation. Eventually, the outcomes of theoretical research is verified by the field tests. Research results will devote to the early warning and preventive treatment for water inrush hazards of karst tunnel. for simulating water inrush of tunnel face

突水灾害已成为我国岩溶隧道建设的重大安全挑战。本项目以钻爆法施工的岩溶隧道掌子面突水为研究背景，认识到爆破和开挖瞬态卸荷双重动力扰动是掌子面突水的重要诱因。项目首先基于大量岩溶隧道掌子面突水案例的系统调查分析和归类统计，从岩体水力学角度归纳出掌子面防突岩体典型结构；其次，开展以防突岩体结构、岩溶水压、初始地应力、爆破开挖损伤程度为主控因素的掌子面突水物理模型试验，提出与防突岩体结构相对应的掌子面突水失稳模式，揭示防突岩体突水破坏的宏观机理。建立考虑爆破和瞬态卸荷耦合影响的三维离散元—计算流体力学动力模拟方法，从细观层面揭示工程动力扰动下掌子面破裂演化及突水通道形成过程与流态转换。然后依据模型试验和数值模拟结果，获取掌子面突水失稳临界特征信息，建立掌子面整体动力失稳判据及防突安全厚度分析方法。最后基于现场试验，对研究结论进行验证。研究成果对岩溶隧道突水灾害预警和防治具有重要意义。

掌子面突水是一种致灾性极强的岩溶隧道地质灾害，因对其灾变机理认识不清导致难以有效遏制该类型灾害发生，造成严重的人员伤亡和经济损失。项目围绕钻爆法施工的岩溶隧掌子面突水灾变机理为这一核心科学问题，综合采用文献调研、理论分析、模型试验和数值模拟相结合的方法，从岩溶隧道掌子面防突岩体结构及失稳模式、掌子面防突岩体破裂演化及突水通道形成过程、掌子面防突岩体整体失稳判据与临突特征信息等方面开展了深入系统的研究。主要研究成果如下：（1）划分了岩溶隧道突水致灾构造类型，建立了岩溶隧道掌子面防突岩体大类-亚类-次亚类的分类方法，厘清了掌子面各典型防突岩体结构突水失稳模式及灾变过程；基于弹性厚板理论、断裂力学理论、关键块体理论及莫尔-库伦理论揭示了各典型结构掌子面防突岩体失稳机制。（2）分析了掌子面突水的爆破与开挖瞬态卸荷双重动态效应，建立爆破与地应力瞬态卸荷耦合作用下支裂纹尖端应力强度因子的计算方法，揭示了爆破和开挖瞬态卸荷触发防突岩体破裂失稳的力学机制。（3）开发了岩溶地层流固耦合相似材料，研制了融合开挖卸荷扰动效应和多元信息监测技术的岩溶隧道突水灾变演化模拟试验系统。（4）建立了综合考虑开挖卸荷扰动及高压岩溶水耦合影响的且能反映掌子面防突岩体突水破裂形成过程的三维离散元模拟分析方法。（5）基于物理模型试验和数值模拟结果，揭示了不同结构类型掌子面防突岩体突水通道动态形成过程及应力场、位移场、渗流场等多场变化规律，明晰了岩溶隧道掌子面突水不同阶段的水流转换特征。（6）获取了掌子面防突岩体整体失稳时应力、位移及渗压等物理量临突特征信息，揭示了岩溶隧道掌子面突水不同阶段的前兆信息特征，建立了典型结构防突岩体的整体失稳判据及最小防突安全厚度与临界水压力的分析方法；依据宜万铁路马鹿箐隧道和重庆市快速路一横线歇马隧道验证和完善了理论研究成果。研究成果对岩溶隧道掌子面突水灾害预警和防治具有重要意义。