The Influence Of Pipeline Leakage On The Ground Deformation And Failure In Shallow Tunnelling

ABSTRACT:In recent years, ground collapse accidents induced by pipeline leakage water happen frequently in urban shallow tunneling. According to this situation, based on common soft surrounding rocks in urban areas, this article will use some research methods which combine model test, granular discrete element (PFC2D) numerical simulation with theoretical analysis to carry out a systematic study on the influence of pipeline leakage on the ground deformation and failure in shallow tunnelling. The main research results of this paper are as follows:(1) when the pipeline is no leakage, the strata has been in a steady state before the excavation of the tunnel, but overlying strata would collapse to the ground surface after the tunnel has been excavated. As the pipeline leakage happens, the pipeline leakage water leads to the presence of the significant surface subsidence before tunnelling, however, the dynamic slump arching would be weakened by the pipeline leakage water, and not only the overall collapse damage of overlying strata is occurred, but also the extent of damage is larger compared with no leakage after tunnel has been completed.(2) Under the case of pipeline leakage, the surface subsidence induced by pipeline leakage water before excavating,the destruction rate and the extent of damage would improve with the range of pipeline leakage water increasing. Therefore, with the improvement of pipeline leakage water, overburden deformation would be magnified and strata collapse would be expedited.(3) The position offset of the pipeline leads to the same shift of the pipeline leakage scope, the range of the surface subsidence before excavating and the extent of strata collapse. Moving down the pipeline makes the distance between pipeline and tunnel vault and the scope of leakage water decreasing. Thus, the overlying strata deformation is weakened,and the extent of strata collapse is reduced.(4) With the increase of water pressure in the pipeline, the pipeline leakage range and the surface subsidence caused by leakage water before tunneling expand, thus resulting the expansion of overburden deformation and strata collapse scope.