深部隧洞卸荷岩体水力特性及破坏机理研究

The rock cracking evolution caused by the combined actions of excavation unloading and external high hydraulic pressure is a complicated mechanical process. Consequently, rock failure mechanism due to the hydro-mechanical coupling effects is not yet clear. It presents a considerable challenge to exactly predict rock failure time, mode and extent, and furthermore guarantee engineering safety. On the basis of the comprehensive analyses of laboratorial and field hydro-mechanical coupling tests and permeability tests under high water pressure, this project focuses on some fundamental theoretic researches associated with the hydro-mechanical coupling mechanism, and the deformation and failure modes of unloading rock mass. Firstly, a rock failure criteria which takes the hydro-mechanical effects into account is expected to be proposed to reveal the hydraulic gradient effects occurring in the process of rock cracking and the failure mechanism of unloading rock mass. Additionally, a constitutive equation considering the hydro-mechanical effects will be presented to develop a numerical model for the unloading rock mass in deep tunnels. By using this numerical tool, high-quality simulation will be conducted for the evolution process of seepage failure. The research results have significant scientific value in enriching and perfecting the coupling theory of unloading rock mass, and also find widespread application in disaster prevention of deep tunnels.

在开挖卸荷和高外水压力共同作用下，深部隧洞节理岩体裂隙演化过程极其复杂，其水力耦合破坏机理目前尚不明确，这给准确预测预报围岩破坏时间、模式、范围和工程安全控制提出了挑战。申请项目以在建水电站深部洞室工程为依托，在室内外水力耦合试验和已有原位高压水渗透试验数据的综合分析的基础上，对深部卸荷岩体水力耦合作用机制、变形破坏模式等开展基础性理论研究。构建反映水力效应的岩体破坏强度准则，揭示裂纹扩展过程中的水力梯度效应及卸荷岩体破坏机理；构建反映水力作用效应的本构方程，建立深部洞室卸荷岩体数值计算模型，并高度仿真渗透破坏演化过程。研究成果对于丰富和完善卸荷岩体多场耦合理论具有重要科学意义，并在深埋隧洞灾害防治方面具有广泛的工程实用价值。

深埋长距离公路和铁路隧道，地下油气储备库，核废料处置库，以及大型和特大型地下水电站等一般处于极为复杂的节理裂隙介质中，深部岩体内高地应力、高渗透压以及高地温多场耦合叠加，在开挖卸荷过程中深部隧洞围岩劣化，高水压渗透破坏作用加剧，严重危及围岩稳定以及洞室工程的安全，并可能对工程施工人员的生命安全造成严重威胁，也影响隧洞的后期运营及长期寿命。研究项目以在建水电站深部洞室工程为依托，在室内外水力耦合试验 和已有原位高压水渗透试验数据的综合分析的基础上，对深部卸荷岩体水力耦合作用机制 、变形破坏模式等开展基础性理论研究。构建反映水力效应的岩体破坏强度准则，揭示裂纹扩展过程中的水力梯度效应及卸荷岩体破坏机理；构建反映水力作用效应的本构方程，建立深部洞室卸荷岩体数值计算模型，并高度仿真渗透破坏演化过程。研究成果丰富和完善了卸荷岩体多场耦合理论，具有重要科学意义，并在深埋隧洞灾害防治方面具有广泛的工程实用价值。研究成果给出了深部高渗透水压下节理裂隙岩体大变形破坏准则，并给出了不同级别围岩变形速率的预警值、最大变形量控制值、最大渗透水压控制值，揭示了深部隧洞裂隙岩体水力致灾机理和灾变演化过程，给出了灾变防控技术方法和具体工程措施。