深长隧道充填型岩溶管道渗透失稳突水机制三维流–固耦合模型试验研究

 为研究岩溶地区隧道开挖过程中充填型岩溶管道受施工扰动和地下水渗流作用发生失稳突水的机制，以湖北省保康至宜昌高速公路尚家湾隧道突涌水段为工程背景，通过大型三维可视化固液耦合试验平台、水压加载控制系统以及水压环境下有较好相似度的流-固耦合岩石和充填物相似材料的研制，开展深长隧道充填型岩溶管道渗透失稳突水的大比尺三维流-固耦合模型试验，真实再现隧道开挖和水压加载过程中，岩溶管道充填物中裂隙形成–扩展–导水通道贯通–突水的全过程，通过位移、应力和渗压变化规律的分析，揭示了充填物渗透失稳突水过程的灾变演化机制。试验结果表明：(1) 施工过程中充填型岩溶管道突水是开挖扰动和高地下水位高渗透力作用诱发充填物渗透失稳的结果；(2) 充填物受开挖扰动影响比围岩更明显，变形量比围岩大20%～25%，应力释放率比围岩高30%；水压加载阶段，水头高度升高到6.0 m时，充填物位移突增50%，渗压下降速率达0.6 kPa/min，达到失稳临界状态；(3) 岩溶管道突水受其发育形态影响比较明显，其弯曲角度较大的部位是阻碍上部水和充填物突出的主要屏障；(4) 充填型岩溶管道渗透失稳突水的灾变演化过程经历四个阶段：形成离散的微小裂隙、裂隙连通形成导水通道、在渗流作用下导水通道扩展延伸、导水通道贯通形成突水路径，其中前两个阶段主要受开挖扰动影响，后两个阶段与高水位高水压的渗流作用密切相关。试验成果对突涌水机制的研究和工程中突涌水灾害的防治具有一定的指导意义。

3D FLUID-SOLID COUPLING MODEL TEST ON SEEPAGE FAILURE WATER-INRUSH MECHANISM OF FILLED-TYPE KARST CONDUIT IN DEEP LARGE TUNNEL

In order to explore the water-inrush mechanism of filled-type karst conduit under the influence of construction disturbance and groundwater seepage，the 3D large-scale fluid-solid coupling model text is carried out based on the water-inrush section of Shangjiawan tunnel in Baokang-Yichang expressway. The 3D visual fluid-solid coupling test platform，the water-loading control system，and the similar materials of high similarity simulating rocks and fillings in water environment are developed. The process of cracks formation-extension- connection-water inrush is truly reproduced during excavation and water loading. The catastrophe evolution mechanism of fillings seepage failure and water inrush under the permeation effects is revealed by analyzing the variation characteristics of displacement，stress and seepage pressure. The research results are as follows. (1) The water inrush of filled-type karst conduit is the result of fillings seepage failure caused by construction disturbance，high groundwater level and high seepage pressure. (2) The influence is more obvious on fillings than surrounding rock. The displacement of fillings is 20%-20% larger than that of surrounding rock，and the stress release rate is 30% higher. In water-loading stage，as the water head height rises to 6.0m，the displacement of fillings rises 50% and the seepage pressure falling rate is 0.6 kPa/min. The fillings develops into a critical state. (3) The water inrush is significantly influenced by the development morphology of karst conduit. The large-angle bend position is the barrier to prevent the inrush of water and fillings. (4) The catastrophe evolution process can be divided into four stages： Discrete tiny cracks are formed. Water channel is formed by cracks connection. Water channel is extended under the function of seepage. Water inrush pathway is formed by water channel transfixion. The first two stages are mainly influenced by excavation disturbance，while the latter two stages are closely related to the seepage effect caused by high water level and high water pressure. The results will make certain guiding significance to research on mechanism of water inrush and control of the disaster.