Research On The Influence On Surrounding Buildings Induced By Tunneling And The Face Stability Of Large Shield-Driven Tunnel

Shield tunnel method is a popular excavation method during the development ofurban underground space, especially in the construction of subway tunnel, because ofits advantages in the adaptation of various geological conditions, construction qualityand excavation speed. However, the tunnel excavation will inevitably has an impacton the buildings in the downtown area, thus the research on the influence of tunnelexcavation to the surrounding buildings is very necessary. Moreover, the constructionof large diameter shield tunnel engineering become more and more common in recentyears, the study on the issues of large-diameter shield tunnel construction is verymuch needed.With the influence of the tunnel excavation to the surface structures, the fieldmeasurement is done based on the intervial tunnel engineering of Wuhan Metro Line2section12. Some conclusions are obtained After the analysis of the measuredresults: the ground subsidense caused by tunneling can be well described by Gaussiancurve in Wuhan, the stiffness of the building has a great influence on the settlementinduced by tunneling, the damage evaluate criteria for the age-old building should bemore stringent.A soil small strain constitutive model is implemented in FLAC3Dby the FISHprogram language, and the correctness of the model program is verified by simulatingthe triaxial tests. Then the effectiveness of the model program in the boundary valueproblem is tested by simulating a geotechnical centrifuge test, the results show thatthe surface settlement of the smail strain model is in a good agreement withexperimental data.Firstly, Based on the small strain model above, The numerical analysis is donefor simulating a group of geotechnical centrifuge tests from Farrell and Mair, thecomparison of the numerical results with the experimental data reveals that the smallstrain constitutive model can well reflect the influence on the buildings induced bytunneling; Secondly, the results obtained by numerical simulation show that thebuilding not only affects the deformation of the surface soil, but also almost has aneffect on the deformation of the soil between the building and the tunnel; Finally, the current assessment methods (Burland’s method and Boone’s method) are reviewed,Boone’s method is imploved and then compared with Burland’s method, thecomparison shows that the predicted result of Burland’s method isn’t safe enough insome cases, and may seriously underestimate the deformation of the frame buildings.The partition method (partition pile and diaphragm wall) is analyzed. Theanalysis focuses on the factors which affect the partition effect and points out that thelength of the pile (the depth of the wall) has a great influence on the partition effect.Three-dimensinal numerical analysis has been carried out to study the tunnelface stability of large shield-driven tunnel in sand. The tunnel depth, the soil strengthand the support pressure distribution which affect the ultimate support pressure andthe tunnel face instability mode are investigated, then the analysis results arecompared with the conventional wedge method, and reveal that the wedge model isnot suiltable for the face stability of large slurry shield-driven tunnels.