Research On Swelling-shrinkage And Shear Strength Of Disturbed Expansive Soil Under Acidic Environment

Expansive soil is a kind of regional special clay, it is called tough, problems, hidden disasters soil by geotechnical engineering because the serious dangers. Soil acidification problem is becoming more and more serious in the expansive soil areas in China caused by acid rain, which is the main form of atmospheric acid deposition. Engineering construction have appeared disease problems with expansive soil acidification. So, it is very important to study swelling-shrinkage, microstructure and shear strength of expansive soil under the acidic environment.In this paper, we selected expansive soil of Ningming area in Guangxi. We study and analyze swelling-shrinkage deformation, shear strength parameters, the stress- strain curve, microstructure and mineral element composition change of disturbed expansive soil under the acidic environment.(1)Based on the non-load swelling test and shrinkage test to explore swelling- shrinkage deformation laws of disturbed expansive soil under different acidic environment and different initial dry density. Experiment results show that under the condition of the same initial dry density, swelling ratio and linear shrinkage ratio of disturbed expansive soil increase with the acid increases; in the same acid condition, swelling ratio of disturbed expansive soil is an exponentially growing with initial dry density increase, and linear shrinkage ratio decrease in a polynomial fashion with initial dry density increase.(2) Based on the triaxial compression experiment to analyze the stress-strain curve characteristics and the shear strength attenuation variation of disturbed expansive soil under the acidic environment. Experiment results show that the stress-strain curves of disturbed expansive soil under the acidic environment show hardening type or the ideal elastic-plastic type under low confining pressure, low initial dry density and high-acid; while the curves show softening type under high confining pressure, high initial dry density and low-acid; the peak shearing strength of disturbed expansive soil will increase with the confining pressure increases; cohesion and internal frictional angle of disturbed expansive soil all decrease in a linear fashion with the acid increases; cohesion of disturbed expansive soil is an exponentially growing with the initial dry density increase, and internal frictional angle is increasing in a linear fashion with the initial dry density increase.(3) By X-ray fluorescence analysis and scanning electron microscopy test to study the changes of mineral element composition, content and microstructure of disturbed expansive soil under the acidic environment. Experiment results show that the acidic environment can dissolution soluble salts and organic matter, dissolve-loss mineral element and change the microstructure of disturbed expansive soil under the acidic environment;the higher acid is, the more severe dissolve-loss mineral element and the more change the microstructure of disturbed expansive soil; improving the initial dry density can effectively reduce the ions dissolved loss and the change of microstructure of disturbed expansive soil under the acidic environment.