高地应力地下厂房预应力锚索预紧系数

为了有效控制围岩大变形，避免围岩破坏，常常对围岩变形突出的高边墙、洞室交叉口区域采用预应力锚索加固。目前，对于具有时效变形特征的高地应力、低强度应力比的地下厂房锚索预紧力相关研究尚较少报道。以锦屏一级水电站地下厂房为代表的高地应力地下厂房，在围岩开挖过程中表现出显著的时效变形特征，从而导致锚索、锚杆内力持续增加，甚至内力超出强度极限而破坏。为合理设置锚索预紧力，基于围岩时效变形特征，提出了围岩时效释放荷载计算方法，并推导了预应力锚索预紧系数计算公式。该公式可以解释不同地应力环境以及不同支护强度、不同施锚时间对锚索预紧力的影响。与锦屏一级地下厂房锚索预紧系数实际采用值对比分析可见，所提出的预紧系数公式较为合理，具有工程实践指导作用。

Pre-load factor of the pre-stressed anchor cable in underground powerhouse with high geo-stress

To avoid the damage of surrounding rock, pre-stressed anchor cables are installed in high side-wall and cavern intersection area to control the large deformation of surrounding rock. However, research is seldom performed on estimating the pre-load of cables in underground powerhouse with high geo-stress and low strength-stress ratio in the previous literature. Jinping-I hydro-power station is recognised as a typical high geo-stress underground powerhouse. Its cavern exhibits remarkable time-dependent deformation during excavation, which may result in the continuous increase of the inner force of the anchor cable and bars, even the strength failure. To determine an appropriate pre-load, a procedure is proposed for calculating the time-dependent released load of surrounding rock, based on their deformation characteristics. At the same time, a formula is deduced to calculate the pre-load factor of pre-stressed anchor cable. This established formula considers the influences of geo-stress, anchorage force and installation time on the pre-load factor. Comparing the actual values with the theoretical values of pre-load factor of Jinping-I underground powerhouse, the result indicates that the established calculation formula for the pre-load factor is reasonable and can be referenced in practical underground engineering.