Numerical Iterative Method for Determination of the Asymmetry Pressure of Surrounding Rock for Shallow Buried Biased Tunnel
According to the equivalent principle of surrounding rock pressure and lining node supporting reaction,a numerical iteration method of asymmetric surrounding rock pressure in shallow-buried un-symmetrical tunnel was proposed.This method took the vertical surrounding rock pressure on one side of the tunnel as the solution target.By improving the traditional dichotomy and using the built-in strength reduction method of FLAC3D,the back calculation process of surrounding rock pressure was fully automated,including the automatic judgment of the stable state of surrounding rock,the auto-matic search of the upper and lower limits of the solution target,the automatic iteration of the solu-tion target and the automatic conversion of the surrounding rock pressure distribution,which greatly simplified the analysis process and improves the analysis efficiency.In addition,this method did not need to assume the slip surface and fracture angle,which reduced the conditions needed to determine the surrounding rock pressure and reduces the related errors.The iterative process of surrounding rock pressure was explained by an example,and the iterative results were compared with the measured results and the standard calculation results.The results show that the pressure distribution of sur-rounding rock obtained by numerical iteration method is in good agreement with the measured results,and can be used for internal force calculation,structural design and service state evaluation of seconda-ry lining.The sensitivity analysis of the influencing factors of surrounding rock pressure shows that in order to reduce the adverse effect of eccentric pressure on lining,the slope angle should be reduced and the soil strength around the tunnel should be appropriately improved.
shallow-buried bias tunnelpressure of surrounding rocknumerical iteration
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