Ground movements induced by pipe jacking in shallow underground soils

Pipe jacking in soft soils may induce ground movements, including ground settlement and axial movement of soils below the ground surface. These movements can lead to damages of nearby structures and utilities. Both theoretical analyses and field observations have shown that pipe jacking in such a kind of soft soil ground as in Shanghai area, movements of soils around the pipes is of three-dimension. Based on the basic principle of semi-analytical method, a procedure for the computation of soil movements is developed which discretize axial direction while adopting displacement functions in radial and circular directions. Regular functions are set up and semi-analytical element method is constituted. Displacement functions, stiffness matrices and load matrices are presented in details. By making use of the semi-analytical element method, the three-dimensional soil movements problem of pipe jacking is transferred to a one-dimensional numerical calculation. The value of a calculated case of pipe jacking in soft soils is compared to that of observations. The results show that semi-analytical element method is a satisfied way to predict soil displacements induced by pipe jacking in shallow soft soils. Due to the sharp reduction of the number of the element, the time needed for processing this problem is much less. Some useful conclusions have been obtained according to the analyses and calculations.