Experimental Study On Physical-Mechanical Behavior Of Backfill Groutng Material In Shield Tunneling

In recent years,shield tunnelling has become a well-established tunnel construction method in the underground engineerings in China,For controlling the settlement caused by the instruction of shield trunnel and protecting the tunnel segments,it is uaually needed to inject the grounting material into the clearance between the tunnel segment and the soil layer.So the physical and mechanical properties of grouting materials are very important in the design and construction of the shield tunnel.Based on the state of the literature review and the engineering problems,a series of physical and mechanical tests were performed on different grounting materials and cemented soils in this study.Comparisons in the mechanicla properties of grounting materials and cemented soils are made,for invesigating the influence of cementing material content and curing period on the mechanical properties of grounting materials.In addition,the differences in the mechanical propeties of different grounting matrials are also discussed.The main work in this study are as follows:(1)Since the rigid grout and cement stabilized soil usually have the small initial void ratio,low compressibility and high yield strength,the existing high pressure consolidation apparatus were modified and connected with the variable head apparatus,for conducting consolidation and hydraulic conductivity tests on these engineering materials.The maximum of the applied pressure can achieve 12.8 MPa;(2)The fall cone test,the vane shear test and the unconfined compression test were conducted to measure the shear strength of grouting materials and cemented soils.Comparisons in the strength of grouting materials and the cemented soils are made,for studying the influence of cementing material content and curing period on their strength behaviour.Then,the differences in the strength of different materials,and the mechanism cotrolling the increase in the strength are investigated;(3)A series of one-dimensional compression tests were carried out on the grouting materials and cemented soils.By comparing the compression behaviour of cemented soils,the cementing material content and the puring period effect on the compression behaviour of grouting materials are analysed.Meanwhile,the applicability of grouting materials in the engineerings is also discussed;(4)Based on the experimental results,the hydrulic conductivity of grouting materials and cemented soils with different cementing material content and puring period,are analysed.In addition,comparisons in their pemeability are also made.