An analysis of the effect of vacuum combined with surcharge preloading on offshore soft foundation reinforcement

Based on the monitoring data of the Zhoushan coastal soft soil foundation treatment, the surface settlement, layered settlement, pore water pressure and horizontal displacement of soil are analyzed in detail. The results show that the compressive capacity of soil mass in the soil below the depth of 6 m is larger after preloading, which is related to the soil quality and uncompress of the soil layer before preloading. Pore pressure increases with the increasing stack load series. Since the vacuum preloading dominates the main position and pore pressure is transformed, the pore pressure has a downward trend, and the resulting joint super static pore pressure is always less than 0, indicating that the vacuum combined surcharge preloading method can reinforce the soft foundation, the vacuum forms a certain negative pressure after the pore pressure, and the fast reactor load will not appear the phenomenon of foundation instability. The horizontal displacement of soil is converted from shrinkage to squeeze out under a certain depth. Reason for the above phenomenon is that the vacuum degree has higher attenuation by well resistance and the vacuum suction is less than the outward additional stress of the stack load produced. The effective depth of the vacuum combined with preloading can reach 4 m below the plastic drainage board.