Study On The Seepage Field Variation And Soil Deformation Caused By Synchronous Grouting Of Large Diameter Shield Machine During The Construction Of A Tunnel

There are many cases for the construction of large diameter slurry shield used in urban rail transit,but the use of large diameter slurry shield under the condition of complex strata in Guangzhou is lack of relevant experience,also there are little research on the effect of synchronous grouting.The mechanical properties and permeability differences of soil in composite strata are significant,which will inevitably lead to the difference of the disturbance law between complex and homogeneous stratigraphy.In this paper,a series of studies have been carried out to study the influence of the seepage field and displacement field on the shield synchronous grouting.Based on the South extension section of Guangzhou metro line four,the site monitoring scheme of soil and water pressure,settlement and horizontal displacement during the construction of a large diameter slurry shield with an outer diameter of 11.66 m is formulated and the field monitoring of the above project is carried out.The variation of the pressure and displacement field is closely related to the synchronous grouting effect of the shield tail.Through the further analysis of the finite element simulation,the perturbed mechanism of the seepage field and displacement field of the stratum is found by the synchronous grouting.Through the above work,the main work and conclusions are as follows:(1)the monitoring datas are analyzed systematically,and the incremental method is used to study the trend of the pore pressure and displacement at each time period.It is found that the shield tail synchronous grouting has a great influence on the displacement and pore pressure of the ground soils.(2)through the analysis of the monitoring data and the displacement field calculated by the 3D FEA,the settlement is caused by the ground loss when shield is crossing the monitoring section,and the synchronous grouting process causes the soil to heave and produce the horizontal displacement far away from the tunnel center,and the displacement of the soils is caused by the seepage force produced by the synchronous grouting.(3)through the extraction of the incremental displacement field produced by a certain grouting in three dimensional finite element method and the corresponding seepage field of the soils,the influence range of the shield tail grouting is analyzed.The results show that the influence range of the synchronous grouting on the seepage field and displacement of the stratum is large,and there is a advance effect caused by the grouting ring after the tail of the shield machine.When there is a certain distance from the monitoring section,it will start to affect,and the effect will be smaller until the shield tail is far away from the monitoring section.(4)through the FEA and theoretical calculation,it is found that the mud membrance formed by the grouting slurry of the shield tail grouting slurry will reduce the pore pressure and displacement of the ground.According to the mud membrance has been formed completely and never formed,the smaller and larger values of the soil displacement can be obtained respectively,and the measured displacement is between the two.