三河口水利枢纽工程坝址区河谷应力场分析研究

In-situ Stress in the River Valley of Dam Site of Sanhekou Hydro-Junction

三河口水利枢纽工程地处东秦岭地区的河谷地段,复杂地质结构和复杂地形地貌决定了工程区地应力分布的复杂性。为了研究其地应力分布情况,采用水压致裂法在左右坝肩边坡和河床部位3个钻孔进行现场地应力测量。测试结果表明:河床部位测孔埋深0～50 m及两岸边坡测孔500～530 m高程岩体应力量值较大,可划为应力增高区;而河床测孔埋深50 m以下和边坡测孔500 m高程以下,可归为原岩应力区;河床浅部岩体最大水平主应力方位与河流走向基本垂直,随着埋深的增加而向区域构造方位靠近;边坡浅层岩体最大水平主应力方向与河流在该段走向呈小角度相交,随着竖直埋深的增加,最大水平主应力方位逐渐向NE向过渡,而接近区域构造方位。

Sanhekou Hydro-junction project is located in the river valley of east Qinling area.Complex geological structure and topography determines the complexity of in-situ stress distribution.To investigate the distribution of in-situ stress,hydraulic fracturing test was carried out on 3 boreholes in the slopes of both abutments and the river bed.Measured results show that the stress values are relatively large in buried depth of 0-50m in borehole at the river bed,and elevation of 500-530m in the boreholes at both banks,which can be designated as increased stress zone.Meanwhile,the area of buried depth under 50m in the borehole of river bed and elevation under 500m in the boreholes of both banks can be designated as original stress zone.In the shallow rockmass under the riverbed,the orientation of maximum horizontal principal stress is nearly perpendicular to the river trend,and with the increase of burial depth,it is close to the direction of regional structure.In the surface rockmass of slope,the direction of maximum horizontal principal stress intersects with the river trend at an small angle,and with the increase of burial depth,it transits to the northeast gradually.In deep buried rock mass,the direction of maximum horizontal principal stress is close to the regional tectonic.