Study On The Improvement Of The Completely Decomposed Granite Silty Soil And Its Road Deformation

As the poor engineering properties soil, the engineering classification, mechanical properties, improved conditions and the road deformation characteristics of the completely decomposed granite silty soil are not well researched, which greatly affect the utilization of the sandy soil. Therefore, it is important to carry out the experiment of completely decomposed granite silty soil to assure the physics mechanics index and improved characteristics, and to promote the engineering application in construction of completely decomposed granite silty soil.This paper used mainly the completely decomposed granite silty soil along Pu tian—Yong ding highway as the background. After the systematic analysis, sorting and summarizing domestic and foreign research situation of completely decomposed granite, through laboratory test and finite element simulation method, the completely decomposed granite and its improved the engineering properties of soil were studied. The main research contents and conclusions of this paper mainly includes the following aspects:1, Do some laboratory tests to analyze the physical properties of completely decomposed granite silty soil, including particle size distribution test, liquid and plastic limit test, compaction characteristics, etc. Besides, do soil mechanical properties test (direct shear test, compression test, CBR) under the different conditions of distinct moisture content and different impact of hit power in order to study about the relationship between different conditions and the soil mechanical properties, to get the result that the soaked soil cannot meet the requirements of the highway subgrade with its CBR values are less than 2, and to provides theoretical basis about improvement of soil.2, The relationship between the unconfined compressive strength of the improved soil and curing period, the ratio of the lime-cement was studied by a lot of lime and cement experiments. Through the linear regression of the experimental data, the trend of unconfined compression strength was analyzed, and the optimum ratio of lime and cement to the soil was put forward.3, For CBR test and rebound test of improved soil, through data regression analysis and theoretical research, clear the relationship between CBR, modulus of resilience and lime ratio. By comparing the intensity of improved soil under soaking or un-soaking concluding that the soaking conditions of CBR value influence is not obvious, has a great influence on the modulus of resilience.4, Using ABAQUS software to build the model, discussing the rule of stress and strain under the different improved thickness of embankment road. By inverse calculation of pavement deflection value and bottom layer tensile stress, the best improved thickness of the lower embankment was presented.5, The influence of load magnitude and frequency on the deformation, vertical acceleration and velocity of the road are analyzed by the elastic-plastic finite element model. It is concluded that the strict control of overload and the proper increase of traffic speed are beneficial to reduce the settlement and deformation of the road structure.