锦屏一级水电站左岸边坡高地应力区卸荷松弛特征及其控制措施

岩体开挖卸荷松弛效应对边坡的稳定性影响巨大,如何控制岩体卸荷松弛程度非常重要。以锦屏一级水电站左岸高边坡为研究对象,区域3维地应力场反分析结果表明:工程区域内地应力水平较高,水平构造应力较大,河床处的最大主应力达到40～50 MPa。施工期声波波速及钻孔变模的测试数据表明:边坡高地应力区的岩体卸荷松弛现象非常明显,岩体卸荷松弛深度随着地应力的增大而增大。边坡高地应力区开展的先挖后锚和先锚后挖的两种岩体卸荷松弛控制试验表明:先锚后挖能够有效地改善岩体的应力释放,同时能够较好地控制岩体的变形。

Unloading relaxation and control measures for the high in-situ stress region of left bank slope at the Jinping I Hydropower Station

Slope stability is influenced by the excavation unloading relaxation effects of rock masses obviously, how to control the degree of excavation unloading relaxation is very important. In this paper, the left bank slope at Jinping I Hydropower Station is selected for the case study, the unloading relaxation effects of rock mass and excavation measures for high in-situ stress slope are researched. Back-analysis results of three-dimensional in-situ stress of study region show that, the in-situ stress at the study region is very high, the horizontal tectonic stress is higher than vertical direction, the maximum first principle stress is about 40-50MPa at the riverbed. The acoustic wave velocity and borehole deformation modulus test results show that, the unloading relaxation effect of rock masses in the high in-situ stress region is obviously and the unloading relaxation degree is increased with the in-situ stress. Two field experiments of anchoring after excavation and anchoring before excavation methods for control the excavation unloading relaxation show that, the anchoring before excavation method can improve the stress relaxation and controlling the deformation of rock masses.