上软下硬地层暗挖地铁隧道合理岩跨比探讨及实例分析

Discussion and Case Study of the Rational Ratio of Rock Mass Thickness and Tunnel Span of Mined Subway Tunnels in Upper-Soft and Lower-Hard Ground

岩跨比选择是上软下硬地层地铁隧道规划设计中的关键技术问题之一,文章在对上覆软弱地层厚度、隧道跨度和下卧围岩质量进行深入分析的基础上,采用经验公式与数值计算相结合的方法,对地铁隧道合理岩跨比进行了综合探讨,并结合工程实例进行了验证分析。结果表明：地铁隧道合理岩跨比受上覆软弱地层厚度影响较小,受隧道跨度和下卧岩层质量影响较大;隧道跨度越大、岩层质量越好,合理岩跨比值越小;将0.27-0.3和0.5-0.6作为青岛微风化岩层大跨地铁车站隧道和中风化岩层塔柱式地铁车站隧道合理岩跨比范围有可靠理论依据。

The selection of the rock mass thickness and tunnel span ratio is one of the key technical factors in the planning and designing of subway tunnels in upper-soft and lower-hard ground. Therefore, based on the analysis of the thickness of overlying soft ground, tunnel span and underlying rock quality, the rational ratio of rock mass thickness and tunnel span of subway tunnels is analyzed by combining empirical formula with numerical calculation. Verification of the results by engineering practice shows that the thickness of the overlying soft ground has fewer effects on the rational ratio than the tunnel span and underlying rock quality do; also, the larger the tunnel span and the better the rock quality, the smaller the rational ratio of rock mass thickness and tunnel span is. Consequently, a reliable theoretical basis is determined for the rational ratios of rock mass thickness and tunnel span of 0.27-0.3 and 0.5-0.6, respectively, for the metro station with large span in slightly weathered rock mass and the pylon-type metro station in moderately weathered rock in Qingdao.