缓倾错动带对白鹤滩水电站右岸出线场边坡稳定的影响分析

右岸出线场边坡位于白鹤滩水电站右岸坝肩顶部,出线场北侧边坡两侧临空,坡体内发育有多条缓倾角错动带,边坡表层岩体受风化卸荷影响随机长大裂隙较发育,与缓倾错动带组合可能形成不稳定块体;在开挖过程中错动带出露部位附近坡面出现多条竖向裂缝,可见坡面残留炮孔沿错动带错位明显,局部稳定问题突出,需对受缓倾错动带影响区域的局部稳定性进行重点分析。建立了右岸出线场区域的精细三维有限元模型,采用强度折减法分析了无支护条件下人工边坡的稳定性,着重分析了出线场北侧边坡的局部稳定特征;针对缓倾错动带影响区域提出了"长锚索+框格梁"的局部支护方案并对支护效果进行了评价。分析结果表明:右岸出线场人工边坡整体稳定性较好,但受缓倾错动带和随机长大裂隙影响区域在开挖扰动和临空条件改变的状况下可能会出现局部失稳破坏;"长锚索+框格梁"的局部支护方案对缓倾错动带影响区域岩体变形抑制效果明显,有效地改善了出线场北侧边坡的局部稳定性。

Analysis on Influence of Low-angle Fault Zones on Stability of Right Bank Outgoing Line Yard Slope at Baihetan Hydropower Station

The right bank outgoing line yard slope of Baihetan hydropower station is located at the top of right abutment.The both sides of at north of outgoing line yard slope are free faced and many low-angle fault zones are developed in the slope mass.Affected by weathering and relaxation in slope surface,a lot of random large cracks are developed in the rock mass of the slope.Some unstable rocks may be formed because of combination of fault zones and large cracks.Many vertical cracks occurred near exposed areas of fault zones on the slope surface during excavation and the residual boreholes on the slope dislocated obviously along the fault zones.So the partial stability problem is prominent.Therefore,in this paper,analysis is mainly performed for partial stability in areas affected by lowangle fault zones.A fine three-dimensional finite element model is established for right bank outgoing line yard area,and the stability of the excavated slope without support is analyzed by strength reduction method,especially for the partial stability of the north slope.A partial support scheme is presented and its support effects are analyzed.The analysis results show that the overall stability of the slope is good,but partial stability problems may occur in the area affected by fault zones and random large cracks.The partial support scheme of"long anchor cable+frame girder"will well control deformation of rock mass in the area affected by fault zones.The effect is obvious and the partial stability of the north slope is effectively improved.