Research On Ground Deformation Caused By Pipe Jacking Construction

As China's urbanization accelerates,pipe jacking construction technology has been widely used in urban construction.However,it inevitably causes disturbance to the surrounding soil,resulting in a certain scope of soil deformation(settlement or heave).When the soil deformation is large enough,it will possibly influence the surrounding buildings,underground pipelines and so on.If not paid enough attention,it may bring immeasurable property losses and security crises to cities and people.The purpose of this paper is to study the ground deformation mechanism,the deformation factors and the calculation of ground deformation caused by the construction of pipe jacking so as to predict the influence and the risk to the surrounding environment.It may provide useful references for the designer,constructor and urban manager of the engineer,so as to take effective prevention and control measures to avoid the occurrence of construction accidents.The main research contents and achievements are as follows:(1)The study takes a pipe jacking project in Shijiazhuang as the background to study the applicability of Peck formula.By using linear regression and least square method principle,the principle and characteristics of the pipe jacking construction process,the deformation mechanism of soil and the main influence factors are analyzed.The Peck equation correction coefficient is obtained after fitting the function.The reference value range of soil volume loss rate ? and settlement coefficient index n is 0.72% ~ 1.13% and 0.65 ~ 0.8 respectively in this project.(2)The vertical displacement of ground caused by the positive propulsion of the pipe jacking tool,the friction between the tool pipe and the surrounding soil are analyzed by applying Mindlin elasticity solution,and the vertical displacement of ground caused by soil loss is calculated by Sagaseta correction formula.The analysis shows that the soil loss plays a leading role in the deformation of the ground,and the construction stress has a limited impact on the deformation of the ground,its influence range is within about 20 meters away from the tool pipe.Based on the previous studies,the Sagaseta analytical formula is modified by using soil loss rate ? obtained from empirical formula and soil-related settlement tank width coefficient index n under the consideration of non-equivalent elliptic soil loss model and Poisson's ratio,the corrective and analytical formula of the deformation of the ground caused by the loss of soil mass is obtained in the hard soil area.(3)The three-dimensional finite element analysis model is established by MIDAS / GTS software to simulate the soil deformation caused by pipe jacking.The displacement and distribution law of soil around the pipe jacking construction are analyzed,and compare the vertical simulation displacement of the ground with the measured values.The analysis shows that when keeping other parameters and working conditions unchanged,the increasing of the depth and the diameter of pipe jacking can both reduce the settlement of the ground.The larger the elastic modulus of the soil is,the better the soil and its bearing capacity is,which is more beneficial to control the ground deformation caused by construction.(4)The calculated results obtained by using measured data fitting,theoretical analysis and finite element method are basically consistent with the measured values,which verifies the correctness of the calculation method in this paper.