Stability of Entrance Slope of Shallow Multi-arch Tunnel Under Unsymmetrical Pressure in Soft Soil of Floodplain Based on Strength Reduction Method
Taking the long-span shallow multi-arch tunnel under unsymmetrical pressure in Wulongshan Mountain of Nanjing as the background,the safety factor and plastic zone distribution characteristics of the slope entrance during tunnel construction were analyzed by finite element strength reduction method,the stability and the development law of the failure mode of the slope were verified,and the corresponding construction suggestions were put forward.The results show that:When the slope angle is larger and the tunnel depth is shallower,the safety factor of the overlying slope during tunnel excavation is lower.Timely,application of tunnel lining structure can greatly improve the stability of slope,but the reinforcement effect will be greatly weakened when the tunnel buried depth exceeds 1.5 times of the tunnel height.When the slope angle is 60°,the potential sliding surface of the slope body will generate near the arch of the shallow buried side of the tunnel.When the buried depth of the tunnel roof reaches 1.5 times of the tunnel height,the failure surface of the slope will no longer pass through the tunnel,but will distribute above the arch.In view of the poor safety of tunnel entrance section,it is suggested to adopt different range of slope surface grouting reinforcement schemes according to different tunnel buried depth and slope angle.When the buried depth of the tunnel is more than 1.5 times of the tunnel height,no slope grouting is needed.When the tunnel buried depth is less than 1.5 times of the tunnel height and the slope angle is less than 60°,grouting should be carried out from the slope foot to the middle partition wall before the construction of the shallow buried side of the tunnel,and the reinforcement depth should not be less than the buried depth of the tunnel arch waist.When the slope angle reaches 60°,the slope surface grouting should be carried out before the construction of both deep and shallow buried tunnels.
tunnelsmulti-arch tunnelssoft soil stratumstrength reduction methodslope stabilityfinite element analysis
NETL
NSTL
万方数据
维普
