Experimental Study On Water-absorbing Expansion Coefficient Of Expansive Soil And Its Engineering Application

This paper mainly takes expansive soil as the research object,using three methods of theoretical research,experimental verification,and numerical simulation to study the water-absorbing expansion coefficient of different types of expansive soils,and summarizes the changing laws of water-absorbing expansion coefficients of different types of soils.The engineering significance and engineering application of water-absorbing expansion coefficient are discussed.The main research results are as follows:（1）Based on the relevant theories of the existing expansion mechanism and starting from clay minerals,an expansion model from microscopic clay mineral particles expansion to macroscopic soil expansion is established,and the calculation formula of soil expansive deformation is derived.（2）Aiming at the influence of the particle size gradation and the number of stirring passes on the free expansion rate test,an improved scheme of free expansion rate test is proposed,and through the particle flow software PFC^2D,the simulation of expansive soil free swelling rate test is realized.（3）Based on the electric double layer theory,the thickness of the hydration film of clay particles was tested by atomic force microscopy technology,and the hydration film thickness of montmorillonite weakly bound water was about 25.13nm,and the measured hydration film thickness combined with the particle size as well as the content of clay minerals,the rationality of the expansion and deformation formula is verified.（4）Through the developed uniaxial expansion test device,the remodeled soil samples under different types and initial conditions are tested and studied,and the real-time relationship curve between the expansion stress and expansion deformation of the sample and the increase in water content is obtained,based on the expansion stress and expansion deformation is closely related to the change of soil moisture content.The concept of water-absorbing expansion coefficient is proposed,and it is obtained that the water-absorbing expansion stress coefficient decreases with the increase of water content,and the water-absorbing expansion strain coefficient increases with the increase of water content.Finally,the rationality and reliability of using the water-absorbing expansion coefficient to classify the strength and weakness of soil expansion are verified.（5）The practicability of the water-absorbing expansion coefficient in engineering application is verified,namely,the three aspects of geological survey,design and numerical simulation.In the geological survey aspect,the water-absorbing expansion coefficient can be used to classify the expansibility of rock and soil.In the design aspect,the water-absorbing expansion stress coefficient can be applied to the calculation of earth pressure and the design of retaining wall and pile foundation.In the numerical simulation aspect,based on the similarity theory and the relationship between temperature field and humidity field,the equivalent relationship between temperature stress and humidity stress is established,the temperature field is used to indirectly represent the change of humidity field in FLAC3D,and the humidity field is simulated.