Study On Consolidation Settlement And Stability Controlling Of Super-soft Foundation Treated By The Method Of Prefabricated Vertical Drains With Preloading

The method of prefabricated vertical drains with preloading offer significant benefits in improving foundations in super-soft soil area with high water content,high compressibility and low bearing capacity by accelerating the drainage consolidation and it has been used extensively in the large-scale infrastructure construction for highways,airports and so on.After reviewing the principal and development of consolidation theory for prefabricated vertical drain in brief,this thesis gives a systematic research on consolidation settlement and stability controlling of super-soft foundation treated by the method of prefabricated vertical drains with preloading based on the example of a super-soft soil foundation engineering in Xiapu tidal flat.?1?The inherent mechanism of soft soil foundation treated by the method of prefabricated vertical drains with preloading is analyzed by using the effective stress principle.Based on the comprehensive analysis of consolidation settlement and lateral deformation characteristics,we should do a good job about stability control under staged filling load,avoiding the occurrence of the ground unstable failure due to large horizontal displacement.?2?Secondly,four typical embankment sections of the secondary highway are selected to carry out the experimental study.During the process of on-site monitoring,the staged filling construction stability prediction model based on the hyperbolic method is proposed,which mainly focuses on controlling the surface settlement and deep horizontal displacement of the subgrade.The measured standard settlement S?_mi of each stage load in the standard settlement time t_{m i} is larger than the calculation standard settlement S_mi,and the lateral displacement rate _iB of the embankment meets the requirements of the standards,which means the embankment is achieved in a consolidation stable state in the preloading period of each load.Because the method solves the"settlement step"problem which is difficult to deal with in the whole settlement prediction,it has certain engineering use value.?3?Finally,aiming at the soft foundation treatment engineering,the plastic drainage plate is simplified by the drainage line and Chai's two-dimensional equivalent method respectively,and the corresponding numerical simulation analysis is carried out in PLAXIS 2D finite element software.By analyzing the calculation results of the two simplified models of plastic drainage plate compared with the measured data,it is found that the surface settlement,deep settlement,deep horizontal displacement and excess pore water pressure of the subgrade are in agreement with the measured data,and the deviation is within the allowable range.Meanwhile,the calculation result of the equivalent permeability coefficient method is reliable by comparing the two simplified models,so Chai's two-dimensional equivalent method can be extended to other finite element analysis of prefabricated vertical drains with preloading method,making up for the limitation of simplified analysis of plastic drainage plate by using the similar finite element software.