木寨岭深埋隧道北段地应力测量与围岩稳定性分析

基于兰渝铁路木寨岭深埋隧道工程区活动断裂调查和3个钻孔水压致裂地应力测量,获得了木寨岭隧道工程区北段的现今地应力分布特征,结果表明,北段工程区最大水平主应力为38.38 MPa,属于高地应力区;三个主应力的关系为SHShSv,表明该区地壳浅表层现今构造活动以水平运动为主,主应力关系有利于逆断层的发育和活动;最大水平主应力优势方向为NE,反映穿越隧道北段的NWW向主要断裂带具有逆冲兼反时针扭动活动特征。根据地应力测量结果、相关理论及判据认为:隧道北段横截面形状以水平长轴、垂直短轴,且长短轴之比近似于隧道截面上侧压力系数的椭圆形为宜;隧道北段在埋深范围开挖时,硬岩具有岩爆发生的可能性,软岩具有发生严重挤压变形的背景。该成果为深入研究隧道区应力场特征,分析隧道围岩稳定性,科学设计隧道断面形状、结构和强度等工程地质问题提供了依据。

IN-SITU STRESS MEASUREMENT AND STABILITY ANALYSIS OF SURROUNDING ROCKS IN THE NORTH SECTION OF DEEP BURIED TUNNEL IN MUZHAILING

In order to conclude present ground in-situ stress distribution characteristics, data are gathered from active fault investigation and three drilling boreholes for in-situ stress measurement located in the north section of the Muzhailing tunnel engineering area along the Lanzhou-Chongqing railway. Combined with the high in-situ data of S_H > S_h > S_v, the core sampling of the structure features of shallow earth crust rock formation reveals that current horizontal principal stress plays a leading role in reverse fault activity. Moreover, measured maximum principal in-situ stress strikes in NE direction and reflects present compressive properties, with sinistral slip activity, of the north segment. Based on the data of crustal stress and the interrelated theories as well as criterions, it is concluded that the favorite shape of the cross-section of the tunnel are ellipses with horizontal long axis, vertical short axis and long to short axis ration as lateral pressure coefficient; when the north section of the tunnel are excavated, the hard rock has the possibility of rock burst, and the soft rock has the background of its occurrence and serious extrusion deformation. The results provide a basis for studying the characteristics of stress field in tunnel area, analyzing the stability of tunnel surrounding rock and designing engineering geological problems such as shape, structure and strength of tunnel section.