| With the rapid development of railways and highways,the total amount of tunnel construction has increased rapidly.In the process of tunne l construction,surface settlement and tunnel surrounding rock deformation are key problems,which have become prominent engineering problems in the process of traffic tunnel construction.Supporting structure is the key to control surrounding rock deformation and surface settlement,so the optimization of subway support parameters is very important.The Qingdao Metro Line 1 is located in the bustling area of Qingdao.The surface settlement caused by the construction process not only causes the unsafety of the project,but also causes adverse effects on the social environment,the humanistic environment and the economic benefit.Therefore,it is of great significance to analyze the formation displacement and the law of surface settlement during the construct ion of the subway,to optimize the design of the excavation method and support parameters,and to study the construction risk of the tunnel.This thesis takes the Qingdao Metro Line 1 line as an example,and uses the method of theoretical analysis and numerical simulation to study the surface displacement,formation settlement,construction technology,support parameters and construction risk in the process of subway excavation,and the following main conclusions are obtained.(1)After the shield method is excavated,the surface of the surface of the surface occurs behind the front uplift,and with the advance of the shield machine,the settlement trough behind the excavation face is wider and wider,the maximum settlement is increasing,and the uplift area is also progressively advancing.The stress of segment lining structure gradually increases with excavation,and the stress of lining structure gradually becomes stable.(2)The pressure of the earth cabin and the grouting behind the segment are optimized,and the formula for calculating the earth chamber pressure and the grouting formula for the primary grouting and the corresponding grouting pressure are obtained.The coefficient K of the earth pressure correction value is 4.4~5.8 KPa/m,and the coefficient of increase of the earth pressure under the dynamic load of the train is 1.005.(3)Optimization of supporting parameters for tunneling during tunnel construction.From the three aspects of the settlement of the vault,the axial force of the bolt and the axial force of the lining,the two parameters of the length of the bolt and the spacing of the bolt are optimized.Considering the economic factors,the length of the bolt length 2.0m and the distance 0.95 m are the best support parameters.Risk assess ment of the project,the risk level index value is 0.78,the risk level is level II,which must be taken certain measures to control risks.(4)The actual monitoring data are analyzed and compared with the numerical simulation results.It is found that the settlement value of numerical simulation is slightly smaller than that of monitoring data,and the error is within the allowable range.The possible reason is that there is a certain error in the theoretical volume values of the formation loss rate,the internal friction angle and the unit length of the tunnel.The YSK43+444 section of monitoring data is a dangerous section,and the rate of change is too fast,so we need to optimize the design. |
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