大断面管幕箱涵隧道开挖面极限支护压力研究

Study on Limit Support Pressure of Excavation Face of Large Section Pipe-Roof Box Culvert Tunnel

【目的】箱涵隧道具有断面大、推进缓慢等特点,开挖面易失稳。【方法】依托合肥市庐州大道浅埋隧道下穿机场跑道实例工程,利用极限平衡理论、摩尔-库伦强度准则、全覆土重理论进行理论推导,并结合大型三维精细化数值模型,对开挖面极限支护压力进行研究。【结果】结果表明:提出了一种简便的管幕作用下大断面箱涵隧道开挖面极限支护压力计算方法。基于此,通过毕肖普条分法计算值与文章提出的极限支护压力计算值相比较,误差极小,证明了该方法的准确性。通过建立管幕箱涵施工三维数值模型,发现地表沉降量和开挖面纵轴线方向位移量随着支护压力的增大而减小,并趋于稳定状态。当支护压力超过静止土压力时,上部土体受强挤压作用,开挖面状态易呈倒S形。【结论】以上结果可为相类似工程提供参考。

【Objective】There are many characteristics of the box culvert tunnel,such as large section,slow con-struction progress and instability excavation face.【Method】Based on the project of shallow buried tunnel sec-tion of Luzhou Avenue in Binhu Science City of Hefei City,this study used limit equilibrium theory,Mohr-Cou-lomb strength criterion and full overburden weight theory to carry out theoretical derivation,and combined with large-scale three-dimensional fine numerical model to study the limit support pressure of excavation face.【Result】The results show that:it proposed a simple calculation method for the limit support pressure of the ex-cavation face of large-section box culvert tunnel under the action of pipe curtain.Based on this,according to the calculated value of Bishop slice method,the error was very small.Compared with the calculated value of the lim-it support pressure proposed in this paper,which proves the accuracy of the method.Through the establishment of three-dimensional numerical model of pipe curtain box culvert construction,it is found that the surface settle-ment and the displacement of the longitudinal axis of the excavation face gradually decrease with the increase of the support pressure and tend to be stable.When the support pressure exceeds the static earth pressure,the upper soil is subjected to strong extrusion,and the excavation face state is easy to be inverted S shape.【Conclusion】The above results can be used as a reference for related projects.