Study On The Influence Of Shield Tunneling In Soft Soil Layer In Changzhou Area On Ground Settlement And Structures

The shield method has become the main means of tunnel construction in urban subways in recent years,and the control of ground settlement during shield construction is one of the main objectives of its construction control.Under different geological conditions,different working conditions,and different construction control parameters,the settlement of the surface and adjacent structures caused by it has different characteristics.Therefore,when designing and constructing subway in Changzhou,it is necessary to study the law of settlement caused by shield construction,and can provide an important reference for future design and construction.Based on the engineering background of Changzhou subway,this paper uses theoretical analysis and finite element simulation to study the related problems of ground subsidence caused by shield tunneling under the formation conditions of Changzhou.The main research contents and research results are:(1)The characteristics of ground subsidence caused by shield construction in sand and clay layers in Changzhou area were analyzed,and the influence of relevant construction parameters on surface subsidence was summarized.The regression analysis was used to obtain the prediction curve of the relationship between the depth of the tunnel under the two strata and the surface settlement.Sand layer is i=0.84+0.49 h,Clay layer is i=2.3+0.05 exp((h-7.88)/ 3.41)+0.08 exp((h-7.88)/ 3.41),and introduce the correction coefficient n = 0.6 ? 0.9,so that the two-line Peck formula can be used in Changzhou sand layer.(2)The whole process of earth pressure balance shield machine tunneling is analyzed,and a numerical simulation method that can quantitatively analyze synchronous grouting,secondary grouting,earth cabin pressure,and shield tunneling speed is proposed.Analysis of the on-site monitoring data of the shield tunneling speed shows that the surface settlement caused by the tunneling speed is faster,and the tunneling speed under the clay layer is obtained by numerical simulation when the tunneling speed is 20 mm / min ? 50 mm / min Prediction curve of settlement relationship: h = 6.5 /(1 + 86.2((v-19.5)/27842.7)0.464),the prediction effect is great.(3)Combining the engineering characteristics of the deep-buried bidding section of the Changzhou Metro,a theoretical calculation method of earth pressure balance shield cutter head torque and shield thrust is proposed,and the error rates with the average monitoring data on site are 6.4% and 3.57%,respectively.(4)Combined with on-site monitoring data through numerical simulation,the effects of secondary grouting,driving speed,and various control measures on the settlement of the tunnel under the existing structure under the shield are analyzed.1.The faster shield tunneling speed can effectively reduce the settlement of the superstructure,and the reinforcement of the soil below the open cut structure and the second grouting as soon as possible will reduce the settlement of the structure to a certain extent,and the second supplementary grouting will be carried out early The effect on reducing structural settlement is more significant.