Study On Ground Settlement Characteristics Of Shield Construction Of Small Radius Curved Tunnel

The ideal urban subway line consists of a straight line and a few curves,but due to the intricate above and below ground structures in the urban area,the subway line often needs to avoid obstacles and small radius curve tunnels are inevitable.Compared with linear tunnels,small radius curve tunnel shield construction is more prone to over(under)excavation,resulting in problems such as shield body jamming,tube sheet breakage,tunnel encroachment and excessive ground settlement.Excessive ground settlement will cause building tilt,foundation stability damage,and affect the normal use of ground buildings(structures).Therefore,it is of great engineering significance to study the influence law of small radius curve tunnel shield construction on ground settlement.The paper takes the tunnel between Cuibai Road Station?Tianshui Road Station of Hefei Rail Transit Line 4 as the engineering background,and uses a comprehensive research method of theoretical analysis,finite element numerical simulation and field monitoring to analyze the influence of tunnel curve radius,stratum loss rate,overburden conditions and construction parameters on surface settlement during the construction of small radius curve tunnel,and the main research contents and results are as follows.(1)The curve correction Peck formula was derived,the numerical analysis model was established,and the numerical simulation analysis results,theoretical calculation results and field measurement data were compared and analyzed,and the results showed that the surface settlement trends of the three basically consistent,and the maximum settlement error value is small;it shows that the numerical model is reliable and the curve correction Peck formula can be used to predict the ground settlement in the curve tunnel construction.(2)Unlike straight-line tunnels,the maximum value of surface settlement in small radius curve section tunnels will be shifted to the inner side of the curve radius,and the smaller the tunnel curve radius,the larger the offset of the maximum value of surface settlement will be,and the two are approximately inverse function curve relationship.(3)The effects of stratum loss rate,tunnel overburden thickness,soil bin pressure and grouting pressure on surface settlement were investigated by using single factor analysis method combined with numerical model.The results show that with the increase of stratum loss rate,the surface settlement value will increase accordingly and the change rate will also increase;the greater the tunnel depth,the smaller the surface settlement value caused by shield tunneling,but the larger the influence range of surface settlement;within a certain range,increasing the soil bin pressure and grouting pressure can reduce the surface settlement,and there is a linear relationship between surface settlement and soil bin pressure and grouting pressure.(4)Based on the research results of the thesis,combined with the shield interval project of Cui Bai Road Station? Tian Shui Road Station of Hefei Rail Transit Line 4,the surface settlement control measures for shield construction of small radius curve tunnel are proposed,with a view to play a reference role for the construction of similar projects in Hefei.Figure [49] table [4] reference[64]...