Study On The Effect Of Defects Of Pea Gravel Backfill Grouting Body On The Engineering Effect Of Segment Lining Structure

In shield TBM tunnels,pea gravel backfilling grouting may result in grouting defects of different types and distribution under various conditions.However,there are few studies on the influence of backfill grouting defects on segment lining structure,and there is no systematic and sound treatment plan for all kinds of grouting defects in engineering.Therefore,relying on the Lanzhou Water Source Construction Project,combined with some other problems encountered in backfilling grouting of TBM tunnel,this paper studies the engineering effect of the defect of pea gravel backfilling grouting body on segment lining structure.(1)This paper investigates the regional geological conditions of the Lanzhou Water Source Construction Project,and summarizes the lining and supporting technology used in the project,in order to prepare for the numerical analysis of segments.(2)Distribution characteristics of various grouting defects are obtained by field coring inspection results and core description.:It is easy to form holes or pure cement slurry at the Top 180 degrees(grouting hole D1 area),and non-dense grouting entities at the top 100 degrees and 260 degrees(grouting hole C1 and E2 area)at the side.Pure cement grouting stone bodies are easy to form at 42 and 318 degrees(grouting holes B1 and F2 area),and high rock powder backfill grouting bodies are easy to form at 0 degrees(grouting holes A1 and A2 area).(3)Through uniaxial compressive test,the uniaxial compressive strength,elastic modulus,deformation modulus and other related mechanical parameters of various types of defect grouting bodies were obtained,and the relationship between elastic modulus and compressive strength was analyzed.The relationship between triaxial compressive strength of grout with different types of defects and surrounding rock is obtained through conventional triaxial tests.The cohesion and internal friction angle of grout with different types of defects are obtained according to ?1-?3 optimal relationship curve and relevant calculation formula,which provides corresponding parameters for numerical analysis.(4)Selecting the parameters of surrounding rock,in-situ stress conditions,segment parameters in Lanzhou water source construction project and relevant physical and mechanical properties parameters of grouting body defects obtained from experiments,the influence of various grouting defects in different ranges on segment stress and displacement in type II and IV surrounding rocks of pressure-free tunnel is numerically analyzed.The grouting body defect type,void defect and non-compactness defect,which have relatively large influence on segment and backfill.(5)As it is a hydraulic tunnel,the influence of various grouting defects on segment and backfill in type II and IV surrounding rocks under normal internal water pressure during operation period is also analyzed numerically.It is concluded that the grouting body defects which have relatively great influence on segment and backfill under the condition of type II surrounding rock are void defects.non-compact defects and pure cement slurry defects.The grouting body defect type with relatively large influence on segment and backfill under type IV surrounding rock condition is void defect.