隧道开孔段围岩变形的薄壳理论预测方法研究

Study on thin shell theory-based method for prediction of surrounding rock deformation of tunnel-intersection opening section

隧道围岩变形预测分析理论主要是针对无开孔隧道,而对于隧道开孔产生的围岩变形,相关预测分析研究理论较少。为此,利用薄壳理论对隧道开孔处受力进行分析,同时结合Mindlin公式对隧道开孔段围岩变形公式进行修正,从而得到了隧道开孔围岩变形预测公式。将所得隧道开孔段围岩变形预测公式应用于肯尼亚内马铁路恩贡山隧道开孔段围岩变形预测,结果显示:隧道开孔段围岩变形预测公式得到隧道开孔段位移为10.766 mm,与恩贡山隧道实际监测位移值相比,其预测分析误差为9.86%;而采用隧道非开孔段位移计算公式得到的隧道围岩预测位移为6.376 mm,其预测误差为35.04%。可见,该隧道开孔段围岩位移预测公式精度较高,满足实际施工精度要求,对实际隧道开孔段设计与施工具有较大的指导意义,并为隧道开孔段拱顶稳定性分析预测提供了新的预测方法。

At present,the prediction theories of tunnel surrounding rock deformation are mainly aiming at the tunnels without intersection openings,while the study theories for the prediction and analysis of the surrounding rock deformation caused by tunnel-intersection opening are less.Therefore,the stress status at tunnel-intersection opening section is analyzed herein by means of thin shell theory,meanwhile,the formula for the surrounding rock deformation of the tunnel-intersection opening section is revised in combination with Mindlin formula as well,and then a formula for predicting the surrounding rock deformation at the tunnel-intersection opening section is obtained.The prediction formula is applied to the surrounding rock deformation of the intersection opening section of Ngong Hills Tunnel for Nariobi-Malaba Railway in Kenya and the result shows that the displacement at the intersection opening section of the tunnel is obtained to be 10.766 mm with a predictive analysis error of 9.86%if compared with that from the actual monitoring of the tunnel,while the predicted displacement of the tunnel surrounding rock obtained from the formula for calculating the tunnel section without intersection opening is 6.376 mm with a prediction error of 35.04%.The accuracy of the formula of predicting the surrounding rock displacement at tunnel-intersection opening section is higher and then can meet the requirement of the actual construction with a larger guiding significance for the design and construction of the actual tunnel-intersection opening section,thus a new prediction method for the analytical prediction of the stability of the vault of the tunnel-intersection opening section is provided as well.