长河坝水电站坝址区斜坡应力场特征研究

STUDY ON CHARACTERISTICS OF SLOPE STRESS FIELD AT DAM SITE OF CHANGHEBA HYDROPOWER STATION

采用孔径变形法对大渡河长河坝水电站坝址区斜坡深部地应力场进行测试,并采用简易、快速、经济的硐壁应力恢复法对坝址区两岸不同高程勘探平硐内的硐壁应力场进行系统测试。研究成果表明,斜坡应力场随深度变化呈驼峰式分布,斜坡应力场具有明显的分带性,由表及里可分为应力降低带、应力增高带、应力波动带和应力平稳带。应力降低带水平深度右岸一般小于36～54 m,左岸一般小于65～95 m;应力增高带右岸约在水平深度40～90 m处,左岸约在水平深度65～125 m处;应力平稳带一般水平深度大于360 m,地应力值在20 MPa以上,实测最大值达31.96 MPa,最大主应力方向为NWW～EW向,属潜在走滑型。并简要分析深切河谷区斜坡应力场呈驼峰式分布的原因。研究成果对认识深切河谷区斜坡应力场具有重要意义。

Valley stress field is one of the most important factors affecting the stability of engineering rock mass.In the dam site of Changheba Hydropower Station on Dadu River,the valley is deeply incised;and the slope made up of granite and quartz-diorite is high and steep.The adit wall splitting and discal drilling core show it is in a high stress zone.The aperture deformation method is used to test the stress field in deep slope;and the adit wall stress restoration method which is simple,rapid and economic,is adopted to test adit wall stress field on different levels in this area.Test results indicate that in this area,the slope stress field has obvious zonation;and the curves of slope stress and depth is hump-shaped ones.From outside to inside,the slope stress field can be divided into four parts,i.e.regions with stress reducing,rising,fluctuating and stabilizing.The horizontal depth of the region with stress reducing on the right bank is less than 36-54 m,while on the left bank it is less than 65-95 m.The horizontal depth of the region with stress rising on the right bank is approximate from 40 to 90 m,while on the left bank it is from 65 to 125 m.Meanwhile,the horizontal depth of the region with stress stabilizing is greater than 360 mt;he stress is more than 20 MPa,even to be 31.96 MPa;and the maximum principal stress direction is NWW-EW.In a word,it belongs to the potential strike-sliding type,inheriting the characteristic of tectonic stress field during late Himalayan movement.The reasons about zonation of slope stress field are also analyzed briefly.The results are of great significance to the study of the slope stress field of deeply incised valley.