煤系地层大跨度隧道围岩结构稳定性研究

针对目前大跨穿煤隧道的研究热点，以重庆市绕城高速公路环山坪隧道为研究对象，在界定大跨度隧道及分析其围岩稳定性关键影响因素的基础上，结合现场监测和数值模拟对大跨度穿煤隧道围岩结构稳定性进行了分析。结果表明，大跨度隧道各处等效应力集中对扁平率变化敏感程度不同，拱脚最为敏感，拱顶基本不随扁平率的改变而变化。隧道穿越软弱煤层段时，围岩应力重分布受影响明显，拱顶位移随开挖面不断推进急剧增加，且隧道围岩塑形圈不断向拱顶围岩内部发展。尤其当煤层软弱带与隧道顺层相交时，隧道荷载结构偏压效应凸显，偏压荷载随煤层倾角变陡而增大，易造成支护结构失稳破坏，在设计及施工中应特别加以重视。

Stability analysis of surrounding rock structure of large-span tunnel passing through coal seams

Focusing on the research hotspot of large-span tunnel passing through coal seams, and taking Chongqing Huanshanping tunnel for example, some works on defining the large-span tunnel and the mechanism of interaction between surrounding rock and support structure was primary conducted, and then on-site monitoring and numerical simulation of the stability of large-span tunnel passing through coal seams were carried out. The results show that the effect of equivalent stress concentration in different part of the tunnel structure has different sensitivities to the change of flat rate, the most sensitive is arch spring, and the crown is the least. Due to sharp stress redistribution when the tunnel is excavated through coal soft rock mass, tunnel crown settlement increases greatly; and the plastic zone can also quickly expand along the coal seam. Specially when the weak coal layer is intersected by the tunnel, the effect of bias pressure becomes much larger and the bias pressure increases with the coal seam steepens, so as to easily lead to the failure of surrounding rock and support structure. Therefore, it should be dealt with carefully during the design and construction.