Research On Soil Structural Parameters And Structural Constitutive Model Of Unsaturated Laterite In Haikou

Laterite covers most of the land area in South of China,which is a regional special soil. HaiNan Province, which has abundant resources of lateritic soils, is an ideal area for lateritic soils studies. It is not only for the need of geotechnical engineering research, but also for the development and infrastructure construction of an international tourist island——Hainan Island.Natural laterite are strongly characterized by the structural and unsaturated property. Introducing an appropriate parameter in the model is an usual way in the study of soil’s structure and unsaturation, to study their effects on the mechanic and engineering properties of the soil and the relationship between them. Following results have been achieved:1. Use moisture content instead of matric suction, which is a tranditional parameter for unsaturation study, to describe the unsaturation of soil. The stress-strain relation and effect of moisture content on it can be obtained through recearch of reconstituted soils with different moisture content and unsaturated natural soils based on conventional triaxial test. The constant parameters a and b are modified to obtained their relationship with moisture content base on a hyperbolic model. Then a hyperbolic model considering the influence of moisture content of the soil sample is obtained and usd to compare and predict the reconstituted soils with different moisture content and unsaturated natural soils. It turned out that the model can effectively simulate and predict the stress-strain relation of reconstituted soils with different moisture content.2. Research on constitutive relation of the soil has been done through the stress path triaxial test. Isotropic consolidation test and shear tests with controlled net mean stress equaling constant are used respectively to study how the spheric stress and the deviator stress affect the stress-strain relation of the soil sample. A K-G model of the soil sample has been built and then deduced to get the corresponding parameters. The model obtained has been used to compare and predict the remolded soil. The results show that the model can significantly fit the stress-strain relation in isotropic consolidation stage and shear tests with controlled net mean stress equaling constant.3. Research on the constitutive property of unsaturated natural soils. The paper used comprehensive structural potential, which is advanced by Professor Xie dingyi, as the structural parameter. Two different structural parameters-stress structural parameter and strain structural parameter are used in isotropic consolidation test and shear tests with controlled net mean stress equaling constant and both of them are quantified and modified in the K-G model to reflect and redict the stress-strain relation of original structural laterites. Compared with the regular K-G model, a better transform curve of the soil samle in the the isotropic consolidation stage and shear tests with controlled net mean stress equaling constant can be gained through the modified K-G model introducing structural parameters.