岩溶隧道土质围岩段地表沉降估算方法研究

Estimation Method for Ground Settlements of the Karst Tunnel in Soil Surrounding Rock

岩溶隧道土质围岩段在渗水条件下易产生地表下沉。为此,文章考虑掌子面渗水导致水位下降而引起的地表沉降,提出了一种潜水稳定渗流下的地表沉降估算方法。文章基于渗流和固结理论分析了渗水条件下围岩中土体单元的自重有效应力和渗流有效应力的变化,并以降水漏斗曲线为界线对围岩沉降区域进行划分;基于开挖横断面建立了二维平面并通过二重积分分析推导了在渗水条件下由渗流作用引起的隧道地表沉降估算公式。文章以广西壮族自治区六寨—河池高速公路瑶寨隧道为依托,分别采用现场实测与估算的方法对土质围岩段地表沉降进行预测,结果表明:两种方法所得结果整体上较为接近,但在距离开挖面3 m的水平开挖径向范围内,实测值大于估算值。研究内容可为渗水条件下岩溶隧道土质围岩段的地表沉降估算提供参考。

Water seepage of a karst tunnel section in soil surrounding rock is prone to surface subsidence.Considering the settlement caused by descending of water level due to water leakage,a method of surface settlement estimation under steady seepage of phreatic water was proposed.Based on the seepage and consolidation theory,the changes of dead-weight and seepage effective stress of soil unit in surrounding rock was analyzed in condition of water seepage, and the settlement zone of surrounding rock was divided by taking the funnel curve of precipitation as the boundary line.A two-dimension plane was established based on the excavation cross section and the estimation formula for surface settlement due to seepage effect was deduced by means of double integral.On the basis of Yaozhai tunnel of Liuzhai-Hechi Expressway in Guangxi Zhuang Autonomous Region,the surface settlement of soil surrounding section was predicted by field measurement and formula estimation respectively.Facts and figures show that the measured values are mainly consistent with the estimation ones,while the measured values are larger than the estimation ones within the scope 3 m away from the excavation face along the horizontal radial direction.