白鹤滩水电站巨型地下洞室群关键岩石力学问题与工程对策研究

 白鹤滩水电站地下洞室群规模宏大、围岩地质条件复杂且地应力水平较高，在现阶段的开挖过程中，普遍揭露了脆性岩体的高应力破坏、软弱层间带导致的深层变形、柱状节理玄武岩的破裂松弛三类典型岩石力学问题。基于室内岩石力学试验，定义脆性玄武岩的启裂强度标准，并结合FLAC3D的Hoek-Brown模型对开挖过程中的洞室顶拱和墙角应力集中区进行分析，提出针对岩体高应力破裂风险区域的支护措施；针对层间带出露于洞室顶拱或高边墙引起的剪出口坍塌、顶拱深层变形、边墙错动变形问题，采用3DEC的Coulomb-slip模型与位移监测相结合开展反馈分析，确定加强支护措施及范围；针对柱状节理岩体的各向异性变形松弛特性，应用专门研发的Comba本构模型与声波检测相结合的研究方法，对柱状节理围岩各向异性松弛深度进行分析，为支护参数拟定提供依据。研究表明，巨型地下洞室围岩的稳定问题通常较为复杂，在施工期依据施工地质、数值模拟和监测成果相结合的反馈分析，不仅能够解释围岩变形破坏机制，而且能够为动态优化设计提供依据。

Key rock mechanical problems and measures for huge caverns of Baihetan hydropower plant

The surrounding rock of the huge caverns of Baihetan hydropower plant is under the complex geological conditions and high in-situ stresses. The high stresses，shear zones and unloading induced spalling of brittle basalt，deformation and relaxation of columnar basalt in the process of the excavation respectively，which are the focus of this paper. The uniaxial compression and acoustic emission experiments were conducted in lab for the study of the stress induced spalling problem and the initiation criteria of crack strength of brittle rock was defined. The Hoek-Brown model using FLAC3D was applied to analyze the potential high stress concentration，and the supporting measure for the zones with damage risk under high stresses was suggested. For the local collapse，deep-seated deformation and shear displacement induced by the weak shear zones located at the roof or the high wall，the Coulomb-slip model using 3DEC for shear zones was employed in analysis with the feedback results from displacement monitoring. The reinforcement measures and ranges were determined. The columnar jointed basalt is discontinuous and exhibits the anisotropy in deformation and strength. The Comba model developed and the monitoring results with the field sonic wave were adopted to capture the anisotropic relaxation depth of the rock under excavation，which provided the helpful insights to the support parameters for design.