Testing Research On Permeability Of Ningming Expansive Soils

Expansive soil is a kind of unsaturated soils which contain lots of swelling clay minerals, and usually make structures deformate and destroyed with its strength decease sharply as swelling and shrinkage due to the change of its water content in the fluency of weather. The slide of slope is the biggest technique problem during the construction of road in the regions of expensive soils. In addition to the character of expansive soil and the effect of wet-dry cycling, the expanding of soils with the seepage of the rainfalls and the attenuation of shear strength are the main reasons of slide of expansive soils slope. So it is all-important to research the permeability of soil and analyze the stability of rainfalls with slide of expansive soils slope. Nowadays the feasible tests method of permeability is inexistence, the studying of permeability of unsaturated expansive soil is still have lots of difficulties need to be solved. Therefore this thesis primary carried out the tests on characteristic of penetrability of Ningming unsaturated expansive soils.First the thesis studied the characteristic of Ningming expansive soils from its type of origins, distributing as well as its microstructure, analyzed the results of permeability tests and the phenomena in the tests with the guidance of theory of unsaturated soils. Using advanced GDS unsaturated Triaxial testing system, the thesis studied the relationship of water-content and permeability, the coefficient of permeability result that is worked out indirectly by Soil-water characteristic curve tests indicates non-linear relationship of water-content and coefficient of permeability of Ningming unsaturated expansive soils, and the facticity of tests result has been validated by combining with the outcome of the VG imitate model. Therefore the theoretic formula of Ningming unsaturated expansive soils that is the relationship with water-content and coefficient of permeability is put forward. In this tests, the coefficient of permeability of the high air entry disk base of GDS unsaturated Triaxial testing system is also demarcated.Considering the influence of structure on permeability of Ningming expansive soils, the thesis designed and done general permeability test elaborately, studied and summarized the influence of void,disturbance and structure with the permeability of Ningming expansive soils. Variability of the coefficient of permeability has been acquired with the changing of void ratio,earth depth and seepage direction, its influence function formula is also put forward.The whole thesis focused on three main factors of void ratio, water-content and structure of earth which influence on the permeability of unsaturated expansive soils to study the permeability by test, the aim is acquire permeability and its variability of...