Study on Limit Support Pressure of Excavation Face of Large Section Pipe-Roof Box Culvert Tunnel
[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.
road tunnelspipe roof box culvert construction methodtheoretical derivationnumerical simula-tionultimate support pressure
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