某地下洞室群分步开挖支护的非连续变形分析

Discontinuous Deformation Analysis for an Underground Cavern Group with Stepwise Support

文章分别从岩体的分步支护以及相应的收敛准则两方面对已有的非连续变形分析程序进行了改进,并应用改进的程序分析了含有随机节理的某大型水电站地下洞室群的围岩稳定问题,着重研究了施工因素的影响,突出了对分步开挖支护过程的模拟计算分析,并且通过与实际工程监测值的比较,验证了该方法的有效性。通过围岩破坏区深度和关键点的位移比较了三大洞室(主厂房,主变室,尾调室)不同的开挖顺序对围岩稳定性的影响和重点支护的关键部位,并对支护方案进行了优化。研究结果表明,此工程中先开挖主厂房与尾调室,再开挖主变室为最优开挖顺序,并且尾水调压室为洞室群支护的关键部位,可以通过在关键位置增加锚索支护的方式改善其围岩的应力状态。

In this paper, an existing discontinuous deformation analysis program was improved using the aspects of stepwise support and relevant convergence criterion. The stability of an underground cavern group with random joints in a large hydropower station was analyzed by the improved program, especially in terms of the effects of construction factors and the stepwise support, and it was verified by comparing the analyzed results with the measured ones. Through a comparison of the influence of various excavation sequences of the three caverns（main powerhouse, transformer chamber and tailrace surge chamber） on rock stability, an optimization was carried out for the support scheme based on the deduced depths of the failure zone and the displacements of key points,showing that the optimal excavation sequence is to excavate the main powerhouse and the tailrace surge chamber first and then the transformer chamber; the cable bolting may be additionally installed at key parts of the tailrace surge chamber to improve the stress state of the surrounding rock.