Study On Fracture Development And Microscopic Mechanism In Dewatering Process Of Expansive Soil

Expansive soil is a common special engineering geological environment.Its special mineral composition and physical properties make it have obvious fatal swell and shrinkage properties,especially the cracking characteristics of crack development,which will cause extreme impact on engineering activities,such as cracking of the ground,unstable slopes,and overall settlement.Therefore,in order to ensure the safety and stability of the project,the research on the development of cracks and the microscopic mechanism of expansive soil in the dehumidification process is extremely important.Mainly involves the following work content:?1?Determination of basic physico-mechanical properties of expansive soil in Nanyang.Through the basic geotechnical foundation experiment,the liquid-plastic combined instrument method,and the free expansion rate instrument method,the water content,natural density,dry density,specific gravity,liquid limit,plastic limit,and free expansion rate were measured in turn,and the calculated liquidity index was combined,judging the state of the soil where the body is located,combined with the free expansion rate,liquid plastic limit,determine the expansion level of the soil.?2?Study on shrinkage and cracking of Nanyang expansive soil during dehumidification.The contraction test is to control the size of the sample under the condition of other variables unchanged,and to study the relationship between the sample size,shrinkage time,and moisture content under the condition that there is no boundary constraint;the cracking experiment is under the condition of other variables unchanged.By controlling the size of specimens and the number of dehydration,the cracking states in different periods were recorded.The development of cracks in the process of dewetting of expansive soil samples under different sizes and dehydration times was studied.?3?Study on the microscopic mechanism of Nanyang expansive soil during dehumidification.In the NMR experiment,the T₂ relaxation time plots and their derived plots at different stages of the inversion of experimental data were used to study the continuity of pores,the volatilization law of water,and the effect of particle size on the experimental results;Based on the characteristic curve experiment,the relationship curve of moisture content,saturation,void ratio and suction was obtained.The relationship between the three components and suction,the change of pores,and the relationship between matrix suction and fissure were obtained.Using electron microscopy,the micro-morphology,pore structure,pore size and microscopic fractures of the surface and cross-section of the sample during the dewetting process were studied,and the microscopic changes of the reaction sample were intuitive.