三峡工程永久船闸二期开挖岩体松弛范围的绝对应力测量

In-situ Stress Measurements in Relaxed Rock Massof Second-Phase Excavation at the Perwanent Lock of Three Gorges Project

永久船闸是三峡工程的重要组成部分,其高边坡是在花岗岩山体中开挖而成的,最大开挖深度达170m。由于开挖卸载,在岩体中形成卸荷应力场,这种新的应力场往往成为岩体持续变形的主要因素,而岩体的持续变形可对工程建筑物(特别是高边坡)的稳定性产生致命的影响。另外,岩体内的地应力释放,使岩体产生回弹变形,岩体结构松弛破裂,岩体力学性质恶化。因此,在永久船闸的开挖过程中,对其进行地应力测量和监测,不仅对边坡整体稳定性分析和安全预报具有重要意义,而且还为制定合理的施工方案,并对边坡的加固处理提供依据。按设计技术要求,地应力测量及其变化监测在永久船闸北坡第四层排水洞内进行,地应力测量和监测的布置如图1所示。按照要求。

The piezo-magnetic overcoring method has been applied to the stress measurements in a relaxed rock mass of the second-phase excavation at the permanent lock of the Three Gorges Project. The quantities and direction of the principal stresses were obtained more accurately. The measurement results reflect the real stress state of the rock mass in the excavation at a certain extent, and give actual data for the rock mass stability analysis. The results also provide a good basis for working out a reasonable construct step. Meanwhile, the stress measurement data were analyzed in conjunction with the distribution of the tectonic stresses in the Three Gorges area. The analysis indicates that the stress measurement results are characterized by a new stress state acting on the rock mass.