浅埋公路隧道Ⅳ_(1)级围岩初期支护设计施工优化研究

Study on Design and Construction Optimization of Primary Support Relatively Class Ⅳ_(1) Surrounding Rock in Shallow Buried Highway Tunnel

浅埋公路隧道Ⅳ_(1)级围岩存在自稳能力差、围岩掉块风险高及格栅拱架支护承载时效性差、施工困难、施工功效底等弊端,严重影响隧道施工安全。通过数值模拟、现场试验等方法对浅埋公路隧道Ⅳ_(1)级围岩初期支护设计进行优化研究。首先,基于有限元分析软件Midas GTS构建二维仿真数值模型并开展计算研究,揭示钢拱架在围岩开挖后其水平及竖向变形、拉应力及压应力响应规律;然后,通过现场试验监测结果与数值模拟计算结果对比分析,得出初期支护采用钢拱架取代格栅钢架的支护设计型式适用于浅埋公路隧道Ⅳ_(1)级围岩段;最后通过钢拱架与格栅拱架在承载时效性、加工及安装难易性、成本费用及施工功效等方面对比分析,可知浅埋公路隧道Ⅳ_(1)级围岩段初期支护采用钢拱架取代格栅钢架,在提高施工工效、节省投资方面具有明显的优势。

The self stability of class IV surrounding rock of shallow buried highway tunnel is poor.The falling of surrounding rock is a high risk.The bearing timeliness of grid arch support is poor,construction difficulty,construction efficiency,and so on.First,the finite element analysis software MIDAS GTS is used to build the simulation numerical model.Through it,carry out calculation research.After the excavation of surrounding rock,the lining response is studied deeply.The response laws of horizontal and vertical deformation,tensile stress and compressive stress of steel arch frame are revealed.On this basis,the numerical simulation results are verified by the field test results.At the same time,the applicability of steel arch support in classⅣ_(1)surrounding rock support of shallow buried highway tunnel has been proved.Finally,steel arch frame and grid arch frame are compared and analyzed in terms of bearing timeliness,processing and installation difficulty,cost and construction efficiency.It can be seen that the initial support of ClassⅣ_(1)surrounding rock of shallow buried highway tunnel adopts steel arch frame instead of grid arch frame,which has obvious advantages in improving construction efficiency and saving investment.