| The thesis takes the expansive soil from Guangxi Nanning as the researchobject, and aims at the effects of rainfall, evaporation, transpiration and otherenvironmental factors on expansive soil. By studying basic properties of expansivesoils, micro-pore structure, soil property and pile-soil interface strength properties,the thesis systematically explores the relationship between soil characteristics and theproperties of interface mechanical behavior of expansive soil and soil under thehydrological-mechanical coupling. The main contents and results are as follows:(1)By using shrink instrument to study remolded expansive soil and undisturbedexpansive soil on their unconfined freedom of expansion and contractioncharacteristics test, we can get the results that: macro swell-shrink characteristics ofexpansive soil are greatly influenced by soil disturbed state, and the reshapedexpansive soil linear shrinkage ratio is larger than undisturbed expansive soil, and ittakes longer time to enter the contraction period.Under the effect of simulatedatmospheric environment, we can do some research about the expansive soilmicroscopic pore structure by using the scanning electron microscope and mercuryinjection apparatus, results show that under the take off, moisture absorption path,pore size distribution curve is of unimodal structure characteristics, mainly smallaperture porosity, there is a small amount of particles between overhead pores andmicrocracks; under the dry-wet circulation condition, the pore size distribution curveshows bimodal structure characteristics, mainly in the medium and small pore, largepore and micro crack is not significantly affected by the dry-wet circulation.(2)By simulating atmospheric rainfall and evapotranspiration environmentaleffect on expansive soil engineering properties, and using conventional triaxial shearapparatus and geotechnical ring shear apparatus, the thesis has studied the mechanicalproperties of the moisture absorption path and expansive soil under the condition ofdry-wet circulation pile soil contact surface. Results show that within the shrinkagelimit moisture content and saturation moisture content, the scope of pile soil contactsurface and the shear strength of soil, cohesive force and angle of internal friction andoriginal modulus decreases with the increase of moisture content; when the soil is dryand the moisture to the saturated moisture content, soil contact strength and thestrength of approximately equal; within a certain scope of dry-wet cycles, pile soilcontact surface and the shear strength of soil with the increase of the number of dry-wet circulation, they present a trend of decrease at first and then increases, but therule of shear strength parameters has obvious difference.(3)Using regression analysis, the thesis has respectively established the soilmoisture content and dry-wet cycles and pile soil contact surface and the shearstrength and shear modulus relation; and the thesis has comprehensively analyzedunder the moisture absorption path and dry-wet circulation conditions, the influenceof the characteristics of expansive soil soil on interface shear strength of expansivesoil-pile, and get the equation of pile-soil intensity parameter characterization ofinterface shear strength equation... |
