Evalution Of Impacts On Environment Due To Parallel Pipe-Jacking In Soft Sandy Deposit

This study was undertaken to evaluate environment effects induced by parallel pipe-jacking construction with large diameter in complicated deposit. Site monitoring, laboratory test, theoretical analysis, and 3D numerical simulation were conducted to investigate the impacts. Some key construction parameters related to soil deformation, such as grouting pressure of bentonite slurry and pressure in slurry chamber were also analyzed. The gist and primary new findings of this thesis includes:1) Variation law of soil stress and deformation induced by the construction of parallel pipe-jacking with large diameter in complicated deposit composed of clustered sandy soil was concluded. Environment effects induced by pipes jacked earlier and those jacked later were different. Grouting had a potent effect on soil deformation induced by consequent pipe.2) Prediction approach of ground deformation induced by pipe-jacking construction by considering grouting pressure was proposed. Rule of soil deformation affected by grouting was studied. Cavity expansion theory in half infinite plane could be used to analyze soil deformation. Calculation method of soil movement due to soil loss by tunneling was developed to predict 3D soil displacement. A formula to predict ground deformation due to additional stress caused by pipe-jacking was improved Comparison between the monitored value and calculated value indicates that the calculation simulated the monitored value fairly well.3) Numerical analyses were conducted to study variation law of soil stress and deformation induced by the construction of parallel pipe-jacking with large diameter in complicated deposit. Suitable construction parameters which can alleviate the environment effects caused by pipe-jacking construction were obtained, such as jacking force, pressure in slurry chamber and so on. Ground deformation was predicated and compared with site monitored value.