Research On Correlations Of Water Content And Mechanical Characteristics Of Expansive Soil

The purpose of the present thesis is following:The relationship between the water content and the expansion rate and the binding force in the expansive soil is revealed, and the serviceable range and the selection criteria of the different mechanical characteristics tests of expansive soils are studied. The work related in the study is mainly divided into two parts:the laboratory test of the mechanical characteristics of expansive soils and the PFC numerical simulation about the above tests.The tests about the relationship between water content and expansion rate are introduced in the beginning. The relationship between the water content changes and the expansion strain is studied, and the results indicate that it is a linear relationship. Followed by an overall stress-strain relationship of the expansive soil sample with four methods is analyzed. The results indicate a linear relationship between the strain and logarithm of stress. But different way of loading leads to different relationship. The result is caused by the adjustment of internal structure and water. By the comparative analysis of different mechanical characteristics tests, the principle of the selection of the expansion tests under different application conditions is brought forward.The PFC numerical simulation studied in this thesis aims at studying the boundary conditions which can not be achieved in the tests. However this thesis does not have a more in-depth breakthrough in the mechanism study, and the PFC program needs a very clear understanding on the microscopic mechanism. Some attempts are done. A numerical direct shear test model is designed by PFC. The unit parameters are adjusted to make the overall parameters similar to the same laboratory test results. This thesis argues that the model which meets the needs of these conditions can be used to do the expansion tests. By adjusting the expansion of the particles, the relationship between the unit expansion rate and the overall expansion rate is established. A numerical expansion test model as described in Chapter3is established to simulate the mechanical process of these tests, and analogical results with the laboratory test results are obtained.