Reinforcement Mechanism And Settlement Prediction Of Vacuum In Preloading In Soft Soil

As the Chinese economy has developed rapidly in recent years, more and more engineering projects are constructed in soft soil area. Vacuum preloading has been widely used in soft soil area of China because of its good treatment effect, advanced technology and low cost. However, there are still many problems worthy discussing about vacuum preloading, such as reinforcement mechanism, settlement prediction, etc. Therefore most engineering projects are designed and constructed relying on experience. And further research is very necessary to be carried out to solve these problems.At first the development history of vacuum preloading was introduced. Besides the research situation of reinforcement mechanism and settlement prediction were summarized. Combining the vacuum preloading project in Lianyun town, the construction technology and field examination project of vacuum preloading were discussed.Researching the characteristics of soft soil in Lianyun town, the results indicated that: â‘ The soft soil in study area was marine deposits silt of Quaternary with high water content, high liquid limit, high compressibility and low strength.â‘¡As the soft soil layer had isotropic consolidation properties in reinforced region, the sedimentary environment of silt layer was relatively similar.â‘¢Approximate results of in-situ test and laboratory test showed that the soft soil in reinforced region was high sensitive soil.Secondly, the concepts of vacuum degree, negative pressure, pore water pressure and excess pore water pressure were introduced. And two common theories about reinforcement mechanism of vacuum preloading as negative-pressure consolidation method and vacuum seepage field theory were discussed in detail. Combining with measurement data, the changing rules in the vacuum preloading process of layered settlement, pore water pressure and surface settlement were deeply researched.Finally according to the measured data, three-point method, hyperbola method and exponential curve method which were common methods of settlement prediction were introduced to calculate the final settlements. By comparing and analyzing the calculation results, hyperbola method was proved to have better applicability, and successful experience were provided for the application of vacuum preloading in Lianyun town.