Discussion On Strengthening Of Expressway Soft Foundation By Vacuum-Heaped Load Combining Precompression

In our coastal provinces, with the exception of some sections of Shandong province, most of the soil layer is saturated normal compaction soft clay, including mud, muddy clay, muddy loam, and muddy sand. Such soils with high compression, low-permeability and low-intensity characteristics can not meet the demand of the deformation of the highway ground base, it is necessary to be reinforced. Therefore, the domestic issue of soft clay subgrade, consolidation settlement, deformation and strength has been the large number of geotechnical engineering scholars and builders issue of common concern.Vacuum-surcharge preloading method is combined by vacuum preloading and surcharge. At first, apply vacuum preloading to the soil, then, when vacuum membrane stability, surcharge on the membrane in accordance with the requirements of vacuum-surcharge preloading method.Treating with the soft subgrade settlement and stability issues with vacuum-surcharge preloading method, this paper focuses on the following elements:(1) This paper analyses the micro-structural of the natural soft clay, the effect of the applied loads on soft soil structure and the external manifestations of pore water pressure and deformation. Through the study on the different characteristics of undisturbed soil and remolding soil, the basic guidance idea on engineering application and analysis on the issue of the treatment of the soft clay subgrade subsidence and stability with plastic drainage plate vacuum-surcharge preloading method is provided.(2) Analyzing the measured value of the settlement, pore pressure and the lateral displacement in the soft soil subgrade in the sixth contract of Shenzhesuwan Freeway, which is in Baique village Huzhou town Zhejiang province, the general regularity of their development is unveiled. Meanwhile, the method of calculating the final settlement by the measured settlement curves is discussed for in-depth analysis. Analyzing the two standards used to calculating the subgrade consolidation and the unloading conditions in project, making sure that it can apply the actual conditions, so it can be easily use and practice.(3) According to the calculation result of subgrade stress by finite element method, the stability of subgrade is studied. In response to the actual project, the standard of the subgrade stability is gained, which can be used and practiced simply.(4) For the engineering application, the soft soil subgrade design method and the job practice and monitor with vacuum-surcharge preloading method is expounded. Particularly, in light of the author's work, on the soft soil subgrade construction, the design and implementation of the observations is discussed in detail, meanwhile, some specific proceedings are discussed in the project construction.