Study On The Influence Caused By Foundation Precipitation Around The Open-cut Zones In Jinci Tunnel

Reducing the underground water level can cause harmful result: the foundationsettlement surrounding buildings and nearby underground pipelines. According to theinfluence caused by foundation precipitation around the open-cut in the Jinci tunnel(DK18+088-DK18+730), this paper analyzes this problem as follows:Firstly, based on variable and invariant total stress, the paper calculates theincrement of effective stress in the influence range of precipitation, drawing aconclusion that decrement of pore-water stress and increment of effective stress are notsimply equal. The characteristics and differences between the consolidation theory ofTerzaghi and Biot are analyzed, and methods of calculating surface subsidence causedby the foundation precipitation are summarized.Secondly, the coupling of soil and water should be considered, because thefoundation precipitation is an issue coupled with stress field and groundwater seepage.The characteristics of groundwater in the process of foundation precipitation areanalyzed, and combining with the consolidation theory, the coupling equation betweenstress field and seepage field is derived.Thirdly, utilizing the FLAC3D, the paper analyzes the impact caused byfoundation precipitation on the coupling of the surrounding environment, and points outthe advantage of FLAC3D on analyzing the fluid-solid coupling. The advantage ofFLAC3D on analyzing the fluid-solid coupling is obvious. Then the process ofmodeling on foundation precipitation and supporting structure are respectivelydescribed. Meanwhile, it is concluded that widening the width of waterproof structureand deepening the depth of waterproof structure can effectively reduce these physicalquantities, analyzing the influence on the characteristics of flow field caused bywaterproof curtain.Finally, according to foundation construction and the simplified geologicalconditions around the Jinci tunnel, the finite difference calculation model is established.Compared with measured dates and calculation results, the variation characteristics ofpore water stress and water level distribution can be obtained, and the relationshipbetween water level drawdown and surface subsidence is summarized. The results show that the tunnel construction will not affect the security of surrounding buildings.Utilizing the FLAC3D, the dewatering-effect are discussed, caused by the parameters:the spacing between dewatering wells, and the depth of dewatering wells, flow rate, soilpermeability.