深埋围岩破裂损伤深度分析与锚杆长度设计

DEPTH OF FRACTURE AND DAMAGE IN DEEP-BURIED SURROUNDING ROCK AND BOLT LENGTH DESIGN

为了确定锦屏二级水电站深埋隧洞合理的锚杆长度,首先对现场围岩破坏模式进行统计,了解围岩的主要破坏方式及其特征,从而确定锚杆设计所需要针对的主要问题。由于损伤区裂纹的发育会导致波速的降低,通过对隧洞典型洞段的声波测试成果的汇总,得到损伤区深度的分布特征,并利用现场声波的测试成果对颗粒流(PFC)程序中的相关参数进行反演拟合,对不同埋深处的损伤深度进行预测。结果表明,随着埋深的增加,围岩的破裂损伤深度和裂纹数量也随之缓慢增加,并非破损深度急剧增加这种破坏模式,此特征有利于锚杆的长度设计。PFC的计算成果也显示出围岩损伤呈现局部化的特点,损伤区内的围岩仍然具有承载能力,锚杆安装在损伤区域范围内,仍然会起到限制损伤破裂发展的作用,达到支护损伤区的要求。

In order to determine the reasonable bolt length for Jinping II deep buried tunnels,the statistical analysis to the failure mode of surrounding rock was carried out and the main problem in bolt design was identified. Because the crack development in the damaged zone led to the decrease of wave velocity,the distribution characteristics of the damaged zone were obtained through the summarization of the typical acoustic test results in the tunnels. The related parameters of particle flow code(PFC) were fitted with the field acoustic test results,and the buried depths of damaged zone at different depths were forecasted. The results showed that the depth of rock damage and the number of cracks were also increased slowly with the increase of buried depth. This feature was beneficial to the design of the bolt length. The calculated results with PFC showed the phenomena of localized damage and that the surrounding rock in the damage zone still had the bearing capacity. The bolt installation in the damage zone still had the effect of limiting the damage development,and met the requirements of the damage zone supporting.