The Effect Of Bent Prefabricated Vertical Drains On The Effective Range Of Vacuum Preloading Reinforcement In New Reclaimed Soil Foundation

Currently, the new dredger fill soft ground has become the main target being reinforced in reclamation projects. To explore the impact of bending vertical drain so as to improve the reinforcement effect of vacuum preloading in this kind of soft ground. But the current research for new Reclamation silty soil ground improved by vacuum preloading is mainly through model tests and field monitoring, there are lack of theoretical analysis and numerical simulation. Based on the basis of Biot’s consolidation theory, numerical analysis is conducted to study it, the main study contents include:(1)The 3D single well calculation models were establish by ABAQUS, order to study the similarities and differences of vacuum consolidation between undisturbed silt and reclaimed silt soft ground which improved by vacuum preloading. The results show that: under the role of vacuum preloading, the settlement of the both soft ground show the settlement is larger in the upper layer than the lower portion, the difference is that shallow sedimentation value of the latter is larger than the former, but deep sedimentation value is smaller than the former. It can be speculated that the Prefabricated Vertical Drains(PVD) bending curvature is larger in the latter than in the former, which makes the transmission loss of vacuum is more serious along the depth, the effect of deep soft soil drainage consolidation is poorer in the latter.(2) New Reclamation sludge’s moisture factor in finite element analysis, the computational analysis found that: amount of compression increases in foundations shallow along with the water content increases; when the water content is up to 90%, the settlement significantly increases in foundation shallow, but the settlement of deep soil decrease. Due to an increase in the amount of compression in shallow ground, speculate PVD bending curvature also increase, resulting in PVD drainage performance reduce and the degree of vacuum decay and pass along the shallower depth, eventually, resulting vacuum preloading for the below 4m deeper silt reinforcement ineffective.(3)Apply the finite element to analysis the vacuum consolidation effects on the new reclamation silt soft ground, when smearing ratio is certain, with the increase ofshkk /, the efficiency of consolidation will gradually be decreased, and the final settlement value is alsoslightly reduced.(4)The reduction of PVD permeability along the depth to simulate the impact of the PVD bending, computational analysis found that, when considering the bending impact, the surface settlement and settlement along the soil depth are significantly reduced. Because of the degree of vacuum attenuated and became smaller along the transfer process, causing negative pressure between the PVD and soil to reduce, it will be more severe with the PVD bending, so it leads the vacuum consolidation behavior in new reclamation foundation to be the truncated cone-shaped or conical,but not the cylindrical-shaped. In addition, While the PVD calculation depth from 20 m to 40 m, through the calculation analysis shows that even increase the driven depth of PVD, actually under 25 m deep silt soft soil reinforcement effect is not much in reclaimed silt soft ground, and the effective reinforcement depth of vacuum preloading is limited.