Disturbance Mechanism And Control Of Large Diameter Pipe Jacking In Soft Soil

Pipe jacking technology, for its advantages of low cost, short constructionperiod as well as the less impact on environmental, has been more and moreapplied to the underground pipeline laying works, and gradually develop to thetrend of large-diameter and long-distance. Taking account the size effect ingeotechnical engineering, large-diameter pipe jacking construction will have itsown characteristics in surrounding soil disturbance relative to the small diameterpipe jacking. With the increasing complexity of modern constructionenvironment, environmental impact control also put forward higherrequirements. Based on Shanghai soft soil area, soil disturbance factors causedby the inner diameter of4m concrete pipe jacking construction were studied.The soil disturbance caused by the pipe jacking excavation surface, as well asthe slurry sets are studied by numerical simulation, the control method isproposed and successfully applied in the actual project.The content and the research results of this paper are as follows:(1) The excavation surface disturbance mechanism of large-diameter pipejacking is studied by Three-dimensional finite element simulation. Soildisturbance law of large diameter pipe jacking construction with differentsupport ratio is analyzed. Soil disturbance type of the excavation face is studied.Recommended formula of excavation face support pressure setting in pipejacking engineering in Shanghai is proposed.(2) Using the finite element method to study the law of soil disturbance inslurry sets control. Through the analysis of the displacement of the soil, changeof pore pressure ratio, and plastic zone is analyzed under different slurry pressure, The slurry pressure control in soil disturbance is studied. Researchshows that too large and too small slurry pressure will cause larger soildisturbance, and the increases of ground surface. It is recommended the slurrypressure should be1.1times the overlying soil weight., In this case, slurrypressure will lead to the minimum soil disturbance.Meanwhile, by comparing effect on the soil disturbance of different frictionsituation, measures to reduce pipe jacking construction shear disturbance controlis proposed.(3) Application of the above-mentioned research results in the actualproject has successfully predicted the environmental impact of the pipe jacking,which has proved the accuracy of the research results. Through a combination ofon-site monitoring data, the environmental impact caused by pipe jackingcrossing beneath is analyzed, and the impact factors is discussed. On this basis,soil disturbance mechanism caused by pipe jacking crossing beneath isdiscussed, guidance for the environmental impact control.