高放废物地质处置库围岩各向异性热-水-力耦合机理及长期安全性分析

The anisotropic thermo-hydro-mechanical coupling behavior caused by original joints and indeuced cracks in sorrounding rock is the controlling factor of the long term safety of high-level radioactive waste underground repositories, while its mechanism is still lack of qualitative knowledge. From the viewpoint of its physical reason: original joints and induced cracks, the systemic methods including laboratory tests, theoretical model and extended finite element are used in this project. A series of laboratory tests are proposed to perform on the samples with original joints and induced cracks in order to obtain the evolutions of elastic modulus, effective stress coefficient, thermal conductivity, thermal expansion coefficient and permeability in both axial and lateral directions. The anisotropic thermo-hydro-mechanical coupling model is formulated based on the interaction mechanism of temperature, flow and stress. The creep tests on the samples with original joints and induced cracks under the effect of thermo-hydro-mechanical coupling are used to model the in situ surrounding rock structure and verify the proposed model. Extended finite element method is used to construct numerical algorithm of thermo-hydro-mechanical coupling, the long term safety and nuclide migration of high-level radioactive waste underground repositories under thermo-hydro-mechanical coupling effect is analyzed. The studied results can offer important theoretic and technical support for site choice, safety design and stabilization analysis of radioactive waste underground repositories in China.

围岩中原生节理和开挖扰动区内次生裂纹引起的各向异性热-水-力耦合是控制高放废物地质处置库长期安全性的关键因素，对热、水和力三场耦合的各向异性的系统研究还不多见。本项目从其内在机理：原生裂隙和次生裂纹出发，设计了一系列含裂隙试样和破坏后产生裂纹的试样的室内试验，获得轴向和侧向方向上的弹性模量、有效应力系数、热传导系数和热膨胀系数以及渗透系数等的演化规律，分析原生裂隙和次生裂纹中热、水和力三场之间的相互作用，建立花岗岩各向异性热-水-力耦合模型。采用热-水-力耦合作用下裂隙和破坏后试样的流变试验模拟实际围岩结构，对所建立的模型进行验证和改进。采用扩展有限元的方法，提出处置库各向异性热-水-力耦合数值分析方法，对我国高放废物地质处置库的长期稳定性和核素迁移性在热-水-力耦合作用下的长期演化特征进行研究。研究成果可为处置库的选址、设计和稳定性分析提供关键的理论和技术支持。

围岩中原生节理和开挖扰动区内次生裂纹引起的各向异性热-水-力耦合是控制高放废物地质处置库长期安全性的关键因素。针对围岩中原生节理和开挖扰动区内次生裂纹引起的各向异性热-水-力耦合现象，设计了一系列含裂隙试样和破坏后产生裂纹的试样的室内试验:（1）完成了含不同角度的天然层理砂岩热学与力学性质试验，分析得出了单轴压缩强度、弹性模量等力学参数和热膨胀系数、纵波波速等热学参数与天然层理角度的关系；（2）完成花岗岩单轴及三轴压缩加卸载试验，并分析了其力学及热学参数随应力损伤造成的次生裂纹扩展之间的关系；（3）对含裂纹岩石提出了有效热学性质的评价方法，包括岩石的有效热学性质、裂纹分布、裂隙流体及应力状态对岩石有效热学性质的影响；（4）完成了花岗岩单轴及三轴压缩过程中的渗透实验和含不同角度裂隙砂岩的有效应力系数试验，分析了原生裂纹、裂纹扩展与渗流的相互影响；（5）针对花岗岩等脆性岩石，考虑裂纹扩展，提出了热-力耦合模型，通过Abaqus实现了力学模型的计算，并通过试验数据验证了该模型的有效性：（6）利用上述提出的热-水-力耦合模型，以瑞典KBS-3处置方案为原型，对高放废物处置库近场进行了热-力耦合数值模拟，分析了温度场整体演化规律、不同材料交界面温度变化规律、材料热学参数对处置库温度场的影响以及巷道开挖、处置回填后的地应力和位移分布。研究成果可为处置库的选址、设计和稳定性分析提供关键的理论和技术支持。