不同溶腔-隧道间距对地铁隧道施工影响的模型试验研究

为探明不同溶腔-隧道净距下隧道施工对岩溶地层的扰动影响规律,以贵阳市轨道交通3号线一期工程为依托,开展了城市浅埋环境下不同溶腔-隧道间距对地铁隧道施工影响的模型试验研究。主要得到以下结论：(1)拱顶侧溶腔对拱腰水平位移位移影响较小,主要影响隧道拱顶的竖向沉降量；溶腔对原始地应力场的影响范围是有限的,溶腔直径为4m、溶腔底部与隧道开挖轮廓线顶部净距为5m时,隐伏溶腔的存在对隧顶围岩的沉降量影响不太显著。(2)溶腔与开挖隧道净距为1m、2m、5m时,拱顶围岩最终土压力变化分别为47.4kPa、84.7kPa、135.1kPa。溶腔底部距离隧道开挖轮廓线越近,拱顶围岩在隧道开挖后的土压力变化越小。岩溶地质现象对原始地应力场的影响表现为岩溶腔体对周边围岩的应力释放作用。(3)溶腔与隧道顶部净距为1m、2m、5m时地中沉降峰值分别为25.7mm、32.8mm、38.8mm,分别为无溶腔时的135.3%、172.6%、204.2%。隧道拱部隐伏溶腔与隧道净距并非越小对地表的沉降影响更大,溶腔-隧道净距与溶腔上覆土层厚度都会影响隧道开挖后的地表沉降。(4)各工况下拱架最终轴力表现为全环受压,弯矩值差异较轴力值更显著。拱部隐伏溶腔的存在一定程度上会减小开挖后初期支护结构拱部的受力,且距离隧道开挖轮廓线越近其拱部弯矩值越小。

Model Test Study on the Influence of Different Spacing Between Karst Cavity and Tunnel on Subway Tunnel Construction

In order to find out the law of disturbance effect of tunnel construction on karst strata under different karst cavity tunnel clearance, based on Phase I Project of Guiyang Rail Transit Line 3, a model test study on the impact of different karst cavity tunnel spacing on subway tunnel construction under urban shallow burial environment was carried out by simulating hidden karst caves with embedded air bags. The main conclusions are as follows: (1) The lateral cavity of the arch crown has little influence on the horizontal displacement of the arch waist, and mainly affects the vertical settlement of the tunnel arch crown; The influence scope of the cavity on the original geostress field is limited. When the diameter of the cavity is 4m, and the clear distance between the bottom of the cavity and the top of the tunnel excavation contour is 5m, the influence of the existence of the hidden cavity on the settlement of the surrounding rock at the tunnel top is not significant. (2) When the clear distance between the cavity and the excavated tunnel is 1m, 2m and 5m, the final earth pressure changes of the surrounding rock of the arch crown are 47.4kPa, 84.7kPa and 135.1kPa respectively. The closer the cavity bottom is to the tunnel excavation contour, the smaller the earth pressure change of the surrounding rock of the vault after the tunnel excavation. The influence of karst geological phenomena on the original geostress field is shown by the stress release of the karst cavity on the surrounding rock. (3) When the clear distance between the cavity and the top of the tunnel is 1 m, 2 m and 5 m, the peak values of ground settlement are 25.7 mm, 32.8 mm and 38.8 mm respectively, which are 135.3%, 172.6% and 204.0% respectively when there is no cavity. The smaller the clear distance between the hidden cavity and the tunnel at the arch of the tunnel, the greater the impact on the ground settlement. The clear distance between the cavity and the tunnel and the thickness of the overburden layer on the cavity will affect the ground settlement after the tunnel excavation. (4) The final axial force of the arch under each working condition is full ring compression, and the difference of bending moment value is more significant than the axial force value. The existence of hidden cavity in the arch will reduce the stress on the arch of the initial support structure after excavation to a certain extent, and the closer to the tunnel excavation contour, the smaller the bending moment value of the arch.