变径洞室超前支护开挖模拟与分析

变径洞室开挖稳定性是地下工程重要的研究课题之一。尤其在围岩软弱的情况下，从小截面向大截面洞室开挖的过程中，会给施工带来很多安全方面的难题。通过有限差分数值分析方法研究了变径洞室的开挖稳定性，分析了拱部小导管超前注浆支护与非超前支护两种施工方法对工程的影响。计算结果表明，由小截面向大截面洞室开挖，不稳定性因素增加，超前小导管注浆支护能够显著提高围岩的稳定性，明显减少了洞室的变形和塑性区，避免了软弱围岩开挖中塌方现象的产生。研究成果对洞室施工具有指导意义。

Simulation and analysis of excavation of variable cross-section cavern with advanced support

The stability of excavating the variable cross-sections cavern is one of the important research topics about the underground engineering. Particularly for weak surrounding rockmass, it may bring insecurity and instability to excavate the cavern from the small sectional-section to the big. By means of the numerical analysis of finite difference, the stability of excavating variable cross-sections cavern was studied; and effects of two construction methods about the advanced support using the ductule grouting or without the advanced support on the engineering were analyzed. The results showed that it’s more unstable when excavating the cavern from the small cross-section to the big; and the advanced support can considerably improve the stability of the surrounding rocks and reduce the deformation of the cavern, and also avoid the collapse of cavern excavating in weak rock. The results are the some meanings for the construction of similar caverns.