高地应力下TBM组装洞特大洞室开挖方法研究

Study on Construction Behavior of a Deeply-Buried TBM Assembling Cavern

锦屏二级水电站TBM组装洞断面尺寸大,并且处于高地应力地区,从围岩应力卸载路径来看,不同的卸载路径影响着洞室的稳定性以及岩爆发生的可能性,因此有必要对洞室的开挖方法进行研究。分析常规台阶法开挖,多工作面开挖以及不同的拱顶开挖方式等3种开挖方法对围岩稳定性影响。结果表明,多工作面开挖能有效降低对围岩的扰动,提高施工速度。最后利用岩爆评判新指标局部能量释放率分析了各开挖方案下岩爆发生的可能性以及规模大小,结果显示,第二种开挖方案最有利。综合分析,建议施工采取第二种开挖方案。

The cross-section of TBM assembling cavern for Jinping caseade 2 hydropower station is large and the cavern locates in high stress area.From the perspective of surrounding rock stress unloading paths,different unloading paths affects the stability of the cavity and the possibility of rockburst,therefore,it is necessary to study the method of excavation.This paper analyzes the conventional bench excavation,excavation by parts and different options of upper heading excavation and their influence on stability of surrounding rocks.Results showed that excavation by parts can effectively reduce the disturbance of surrounding rocks and enhance the construction speed.Finally,using the new rockburst index evaluation of local energy release rate analyzed the possibility of rockbursts and their scale under various excavation schemes,the results showed that,the second scheme is the most favorable one.Through omprehensive analysis,the author suggests to the use the second excavation scheme for construction.