水压致裂法地应力测量在成昆铁路垭口隧道的应用

The Application of Hydraulic Fracturing Stress Measurements in the Yakou Tunnel of Chengdu-Kunming Railway

垭口隧道是成昆铁路米易至攀枝花段的重点控制性工程,以地质条件复杂、工程地质问题突出、围岩变化频繁、施工安全风险高而著称。地应力是影响隧道围岩稳定、划分隧道围岩分级的主要影响因素之一,为查明工程区的地应力状态,在全隧道开展了两个深孔的水压致裂地应力测量工作。结果表明:最大主应力方向总体为N29°E,优势方向为北东向,这反映了研究区受印度板块构造作用明显;三个方向主应力相对大小表现为SH> SV> Sh,表明该地区在地壳浅部水平应力占主导地位;最大水平主应力方向与隧道轴线方向夹角为30°,对隧道围岩的稳定略为有利;σc/σmax介于3. 49~5. 15,应力值水平属于高应力至极高应力状态;通过判据分析,垭口隧道在开挖过程中硬质岩有发生轻微岩爆的可能,软质岩洞壁岩体有位移甚至发生大变形的可能。

The Yakou tunnel was the Key control engineering of the Miyi to Panzhihua section of Chengdu Kunming Railway,with the characteristics of complex geological conditions,outstanding engineering geological problems,frequent change of surrounding rock and high risk of construction safety.The geo-stress is one of the main factors affecting the stability of tunnel surrounding rock and its classification.In the whole tunnel,2 deep-holehydro-fracture geo-stress measurements have been carried out in order to find out the geo-stress state in the engineering area.The results are as follows.The direction of the maximum principal stress in the tunnel area was N29°E,dominantly in northeast direction,that is,the study area is obviously influenced by the tectonic action of India plate.The relative size of three principal stresses was shown as SH>SV>Sh,that is,the horizontal stress in the shallow crust of the region was dominant.The angle between the direction of the maximum horizontal principal stress and the axis of the tunnel was 30°,to the stability of the tunnel surrounding rock is slightly favorable;the ratio ofσc/σmaxwas 3.49~5.15,the geo-stress level belongs to the high-extremely high stress state;Through the analysis of the criterion,slight rock burst in hard rock and large deformation in soft rock may occur during the excavation of Yakou tunnel.