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According to the monitoring results of soft clay treated by preloading with plastic drainage pipe, the consolidation settlement effect of soft clay with 50kPa preloading load, 21m plastic pipe, 1.2m and 1.5m distance was compared with that of 30kPa preloading load, 6m plastic pipe, 1.5m and 2.0m distance. The analysis showed that, the preloading method with deep plastic drainage pipe can accelerate the dissipation of excess pore water pressure in deep soft soil. The over-flow penetration may occur in the confined water. The elastic deformation appears and recoveries after unloading. This is not conducive to the consolidation of soft clay layer 4. The plastic drainage pipe whose depth and distance should be 18~20m and 1.5m respectively to the consolidation soft soil in Pudong.

The seismic responses of solid pile and hollow pile were analyzed and compared in this paper. According to the deflection equation of pile during earthquake, rotation, bending moment, shear force and soil resistance of pile were obtained. The differences of deflection, rotation, bending moment, shear force and soil resistance between hollow pile and solid pile, whose effective areas of cross-sections were same, were found. From calculation results, hollow pile had certain advantages in seismic performance. This study provided a theoretical basis for the applications of hollow piles in practical engineering.

Ground subsidence is one of the main geological hazards in Shanghai. The ground subsidence is caused by pumping groundwater greatly. In the past, studies of ground subsidence in Shanghai were mostly taken for the ground subsidence caused by pumping confined water in Puxi. And ground subsidence caused by pumping phreatic water was rarely studied. Dewatering preloading is a new technology for soft soil treatment. The monitoring of ground water level, ground subsidence, pore water pressure in the process of dewatering preloading test for a soft soil treatment project in Pudong showed that pumping phreatic water can also cause ground subsidence. The ground subsidence caused by pumping phreatic water was analyzed in this paper. The relationship between phreatic water level and ground subsidence was obtained.

The method of composite stiffness principle and biparameter for laterally loaded pile was used in this paper to calculate the amplitude of deflection and rotation of pile on the ground when the vibration frequency of dynamic load is equal to or close to the natural frequency of pile, i.e. when the pile is in the state of resonance. And the amplitude of the maximum bending moment and its location was also calculated. Then the finite difference method which is simple in principle and easy to program was used to calculate the displacement, soil side resistance and internal forces of pile under horizontal dynamic load. By choosing reasonable parameters, rotation, displacement, and the maximum bending moment of hollow concrete pile and solid pile under the same dynamic loads at pile top in the same geological conditions were calculated respectively. On this basis, the performance differences between hollow pile and solid pile were analyzed. Some advantages of hollow pile were obtained. This research provides a theoretical guidance for the using of hollow pile in engineering.

The consolidation coefficient, permeability coefficient and other parameters were calculated out based on field measurement data of pore water pressure in this paper. The post-construction settlement behaviour of dynamically consolidated foundation was also simulated. The simulation results were consistent with the actual observation results. The method of this paper provides an effective way for the prediction of post-construction settlement of dynamically consolidated foundation.