长河坝水电站地下厂房围岩复合型变形破坏特征分析

Study on Composite Deformation Failure Characteristics of Surrounding Rocks in Underground Powerhouse at Changheba Hydropower Station

长河坝水电站地下厂房实测最大地应力超过30 MPa,岩石强度应力比为3.75-7.5,属于高地应力区。监测资料统计结果表明：长河坝水电站地下厂房实测变形量值大于典型的高地应力地下厂房——锦屏一级水电站地下厂房的变形量。但长河坝水电站地下厂区地应力水平低于锦屏一级水电站厂区,岩体质量优于锦屏一级水电站厂区。针对这一异常现象,从声波测试资料、变形监测数据及厂区结构面特征等方面出发,对长河坝水电站地下厂房围岩变形破坏特征进行了综合分析,认识到长河坝水电站地下厂房围岩变形量大的根本原因在于高地应力下结构面对围岩的劣化作用被加剧,从而导致围岩出现浅层松弛程度大、变形量大的现象,属于结构面与应力复合型变形破坏模式。根据研究结果,对长河坝水电站地下厂房支护设计的合理性进行了评价。

Changheba hydropower station is located in high stress area with measured maximum in-situ stress more than 30 MPa and rock strength-stress ratio 3. 75-7. 5 in underground powerhouse area. Statistical results of monitoring data show that the measured deformation value of underground powerhouse at Changheba hydropower station is higher than that of underground powerhouse at Jinping I hydropower station which belongs to typical high in-situ stress underground powerhouse. However,in-situ stress level in underground powerhouse area at Changgeba hydropower station is lower than that at Jinping I hydropower station,rock quality is better than that in powerhouse area at Jinping I hydropower station. In view of this abnormal phenomenon,a comprehensive analysis on composite deformation failure characteristics of surrounding rocks in underground powerhouse at Changheba hydropower station is performed in aspects of acoustic test data,deformation monitoring data and discontinuity in powerhouse area. It is found that large deformation of surrounding rocks in underground powerhouse at Changheba hydropower station is mainly caused by aggravated discontinuity deterioration effect on surrounding rocks,resulting in large shallow relaxation degree and large deformation in surrounding rocks,which is classified as discontinuity and stress composite deformation failure mode. Based on analysis results,proper support design for underground powerhouse at Changheba hydropower station is evaluated in this paper.