Analysis Of Environmental Effects Due To The Ramming Pipe Roof

Utilizing and empoldering underground space is more and more important in city development. As an effective supporting measure of tunnel excavation, pipe roof method has been widely used, especially in the conditions crossing existing project. In these cases, pipe ramming method is a common choice. It is ineluctable that soil layer is destroyed because of pipe ramming and earth deformation is produced to affect the surrounding environment. In this dissertation, environmental effects of pipe ramming are investigated. The major works and results were as follows:(1) On the basis of plastic mechanics and dilatancy of soil, formulas for stress field and displacement field in infinite body with cylindrical cavity expansion has been obtained.(2) During the driving process of pipe pile, the squeezing effect and plugging effect will be generated. Based on the reasonable assumptions, the elastoplastic analytical solutions for stress field and displacement field of the soil around the pile are presented.(3) Expressions of stress field and displacement field are deduced via image method. Meanwhile, the sensibilities of soil layers parameters, outer diameter, buried depth, initial stress and relative buried depth to vertical displacement and horizontal displacement are analyzed. The conclusion is arrived that outer diameter, buried depth, initial stress and relative buried depth are pivotal factors.(4) Numerical simulation of environmental effects is researched according to displacement load method and Drucker-Prager yield criterion. The modulus and thickness of pipe to vertical displacement and horizontal displacement are analyzed and all have obviously influence. And the coherence is obvious from the contrast graph between analytical expression and numerical solution.(5) A practical project where Subway Line No.4 crosses the existed No.2 line under Xuanwumen station in Beijing, is analyzed the displacement with numerical simulation method.