(1. PowerChina Huadong Engineering Corporation，Hangzhou，Zhejiang 310014，China；2. HydroChina Itasca Research and Development Center，Hangzhou，Zhejiang 310014，China；3. China Three Gorges Corporation，Beijing 100038，China)
Abstract：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.
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2016, Vol. 35 
