| Soft soils show low strength, high compressibility and low permeability, so soft soils must be reinforced before people build expressway, port and dock etc on them. Vacuum preloading method is effective to improve the soft soil foundation. The settlement and stability problems are well solved by this method and the time limit for a project is shortened. However, there are still many problems on the research of improvement mechanism. These problems have restricted its wider application and development.By means of theoretical analysis and field monitoring, the improvement mechanism of vacuum preloading method is analyzed. The variation of surface settlement and horizontal displacement, groundwater level, pore water pressure and vane-shear strength of foundation is studied. The main contents presented in this thesis can be summarized as follow:Based on the field monitoring data of project, the variation of surface settlement,and settlement profile, pore water pressure, groundwater level, and vane-shear strength of soils in different depth of the foundation during vacuum preloading is studied in this paper. The improvement effect is discussed, and suggest on how to get the real groundwater level data in monitor measure is proposed.Based on the mechanism of vacuum preloading method to improve the softfoundation, influence of this method on surrounding environment is studied. From theperspective of side-discharging, stress and deformation of the soils out of vacuumpreloading field are discussed. Combined with the results of observed field data, thecharacteristic of the horizontal displacement and vertical settlement of surroundingenvironment is analyzed. The results show that, because the border of improved areais unable to seal totally, with the decreasing of groundwater level in the vacuumpreloading field, the groundwater level of surrounding area will decrease in variousdegree too. Then the soils will keep on consolidation and surface settlement afterunloading. The measures to reduce its influence have been described and theconclusions can be used for reference in the similar engineering project. |
