Earth pressure distribution and structural response of rectangular pipe jacking in soft clay

The rectangular and quasi-rectangular pipe jackings are increasingly used in the construction of urban underground space structures. Their structural water and soil load distribution characteristics and structural response are particularly important for engineering stability and safety. However, there are few relevant studies. Based on a review of the existing methods for earth pressure of pipe jacking, the vertical earth pressure distribution at the top of rectangular pipe jacking in saturated soft clay and the deformation mode of lateral linings are studied through the finite element simulation, and an improved load model for rectangular pipe jacking that includes non-uniform vertical earth pressure and horizontal soil resistance is proposed. The method is validated by comparing with an overall stratigraphic-structural finite element simulation. The main conclusions are as follows: (1) The earth pressure at the top of pipe is non-uniform, approximately displaying a trapezoidal distribution pattern with smaller pressure at mid-span and higher pressure at both sides. The averaged vertical earth pressure is similar to the full overburden value. (2) The degree of non-uniformity of vertical earth pressure increases with the increase of section size, increase of structural burial depth and decrease of height-to-width ratio, among which the height-to-width ratio has the most significant impact. (3) The height-to-width ratio affects the lateral deformation mode of the pipe jacking structures. The flat pipe jacking deforms laterally outward and squeeze the soil, inducing horizontal soil resistance. (4) The non-uniform distribution of vertical earth pressure and horizontal resistance play an important role in the reasonable calculation of the bending moments at the top and waist of the rectangular pipe jackings in soft clay.