Effects Of Tunneling On Ground Movements And Underground Pipelines

With the expanding scale of urban construction, urban underground excavation and pipelines have been becoming increasingly important to the use of underground space. As lifeline project, urban underground pipelines are buried in shallow stratum. Meanwhile, underground transportation engineering has been significantly developed to relieve the increasing pressure on urban traffic. In the future, more and more urban underground railways will be built in Chinese cities. The construction of underground tunnels will inevitably affects both the strata and above pipelines. Seriously, strata collapsing and pipeline bending fracture accidents have occasionally occured. The existing researches could not totally solve problems in practical engineering. Therefore, the influence of tunneling on the surrounding stratum and above pipelines is still the subject which is urgently to be solved in current research.Based on the primary research, the effects of tunneling on ground loss and upper pipelines are invetigated. The deformation and stress components of pipeline are calculated by using finite difference method (FDM). The outline and resultant conclusions of the present work are as follows:(1) The stratum deformation mechanism due to tunneling is surveyed. The investigation indicates that the stratum deformation depends greatly on the tunneling method, the depth of tunnel, groundwater,ground loss et al.(2) A novel emprical model to evaluate the ground defornation by tunneling is proposed by modify the wellknown Peck’s model. The present model can consider stratigraphic sedimentation curvature and range of influence.(3) The deflection and stresses of the overlying pipeline due to tunneling are calculated. The theory of beams on Winkler foundation is employed to simulate the pipeline. The governing equation of the deformation of pipeline is deduced based on the soil-pipe interaction and solved by finite difference method. Comparison of the present results with the known results indicates the accuracy of the proposed method. Moreover, overall parametric study is conducted to examine the effects of the curvature coefficients of strata distortion n, the parameters of tube soil stiffness ratioκ, the parameter of soil settlement i and the maximum settlement of the stratum Smax on the behaviour of the overlying pipe.(4) The safety evaluation of the pipeline by tunneling is executed. The discriminant methods and standard are proposed to the flexible and rigid pipes, respectively. to lay the foundation for the pipeline safety evaluation this paper also gives new method of pipeline curvature radius.