Changes in super pore water pressure in soft ground under multi-factor influences coupled with positive and negative pressure

Vacuum stacking joint pre-compression method is widely used to reinforce soft ground, with the preloading process generating a coupling mechanism involving both positive and negative pore pressure, the effect of this method to reinforce soft ground is affected by many factors, such as the spacing of drainage board spacing, vacuum intensity, vacuum preloading duration, and interval time. Previous studies focused on single-factor analysis, failing to adequately account for the coupled effects of multiple factors on the super pore water pressure in soft ground. Based on the establishment of finite element model and verification, based on the calculation results of the study of drainage board spacing d, vacuum intensity P_v, vacuum preloading duration T_v, interval time T_i and other construction parameters on the super pore water pressure, to explore the positive and negative pressure coupling multi-factor influence of the super pore water pressure change rule. The results show that: when the spacing of the drainage board increased from 0.9 m to 1 m, the increase in super pore water pressure is more obvious, and the spacing of the drainage board is recommended to take 0.9 m considering the drainage effect and economic benefit; with the increase in P_v, the peak of the super pore water pressure produced in the soft foundation after continuous stacking basically shows a linear and gradual decline; with the increase in T_i, the super pore water pressure produced in the soft foundation is basically decreased gradually. The super pore pressure generated in the soft ground shows a decreasing trend, and the change in the super pore pressure is not obvious if T_i>15 d, so it is suggested that the interval time is 15 d; T_v only affects the super pore water pressure at the initial load stage; drainage board spacing, vacuum intensity, interval time significantly influence the super pore water pressure evolution during preloading process. The research results provide a scientific basis for the design and construction of vacuum-surcharge preloading treatment.