Deformation Analysis Of Small Turning Radius Shield Tunnel Construction

With the modernization of cities, demands for power and transportation has been on therise. Traditional power transmission through high altitude has been greatly limited for itsinfluence on urban space, urban landscape, fire protection and security and so on,consequently it becomes difficult to continue using the traditional method of powertransmission. On the contrary, underground tunnel has the advantages of high capacity, highsecurity, no influence on the urban landscape and no occupying of the land, which make it theoptimal manner of modern high-capacity electricity transmission. Similarly, underground railtransportation has the advantage of safety, efficiency, comfort and celerity and thus making itthe bast solution to transportation congestion of modern city. Underground tunnel and railtransportation usually adopt shield construction and take small-radius curve tunnel to bypassurban obstacles such as the dense buildings and a variety of tunnels because the curve radiusof electricity tunnel could be as small as100m to adapt to the extension under curved street.The construction stress and deformation of curve shield tunnel with small radius and theresulted environmental problems are the critical issues that should be taken into considerationfrom the point of construction design and safety. In the dissertation, the author analyzed theconstruction stress and deformation of small-radius shield tunnel through the method ofmeta-data, which would provide references for construction design and safety analysis.The main researching works and achievements of the dissertation involved the followingaspects:(1) The author summarized the characteristics of the construction stress and deformationof linear and curve shield tunnel the differences of their demands for constructionenvironment and also discussed the construction and safety issue of small-turning-radiusshield tunnel.(2) Through using Mohr-Coulomb soil model and the linear deformation segment model,the author established the mesh model for calculation of construction stress and deformationof small-radius shield tunnel, which is suitable for that of small-turning-radius shield tunnel aswell.(3) Using the finite meta-computing mesh model, the author listed three kinds of calculating concerning the construction stress and deformation of small-turning-radius curveshield tunnel. The results revealed that as the turning radius decreased, the stress anddeformation of curve tunnel increased and the hazards it brings to the environment increased.(4) For different turning radius, the author provided analysis of construction stress anddeformation of curve shield tunnel surrounding rock, including soft soil, silty clay, poor soiland mucky soil. Through calculating, the author found that when the strength of soil is small,it is too difficult for the soil on the reverse side of the small-turning-radius shield tunnel toprovide enough counter-force to push the advancement of tunnel, thus making theconstruction of the curve part of the small-radius tunnel difficult to implement.(5) For the difficulty mentioned above, the author proposed grouting measure tostrengthen the soil on the back of the soil and further solving the problem of shield tunneling.(6) The author proceeded corresponding numerical analysis according to the supportmeasure taken for the soft soil layer in the small-turning-radius curve shield tunnel. Theanalysis shows that the support measure could improve the soil strength and further solve thetunneling problem of small-turning-radius shield in soft soil.