Study On The Effect Of Oligosaccharide Degradation Process On Engineering Geological Properties Of Clay

As an important part of domestic pollutants,carbohydrate infiltrate into soil and undergo chain biological and chemical reaction,which will cause changes of engineering geological properties of soil.In this thesis,the degradation process of carbohydrate oligosacch-arides in soil was taken as the main line,and the curing time and pollutant concentration were controlled as experimental variables to explore the changing laws of engineering geological properties of clay from the perspectives of degradation rate and degradation amount of oligosaccharides.Through laboratory tests and analysis of the components and stage responses of municipal waste contaminant,the typical carbohydrates oligosaccharide(sucrose)was selected as the single-phase pollution source,the chemical reactions and products during the degradation of sucrose in soil were clarified,and the degradation degree and stage of sucrose were determined and divided.Using the contaminated soil with different sucrose concentrations prepared by remodeling,the variation law of the macroscopic geotechnical properties of the clay with time(degradation rate)and concentration(degradation amount)were tested and studied,and the influence law of carbohydrate degradation on the microstructure of clay and the action mechanism of geotechnical properties were further revealed.The following research conclusions were obtained:(1)The characteristics of the degradation process of sucrose in a slightly acidic and closed soil environment were obtained.The degradation amount of sucrose was selected as the parameter to characterize the pollutant concentration,and the positive proportional relationship between them was obtained.Sucrose degradation rate was selected as the parameter to characterize the curing time.At the end of curing,it reached more than 90%,which was completely degraded.According to the change rate of the degradation rate,the whole degradation process was divided into two stages: fast degradation and slow degradation.(2)The polluted soil formed by sucrose infiltration into the soil presents a response mode of “three stages and two sections”.(1)In the initial stage of formation,the pollutants changed the hydraulic properties of the soil: it reduced the saturated water content,pH and permeability of the soil;increased the bound water content,electrical conductivity liquid limit and plasticity index of the soil but had no effect on the plastic limit.The contaminants strengthen the mechanical properties of the soil: it increased the shear strength and unconfined compressive strength and reduced the compressibility.(2)In the middle stage of degradation,under the influence of the degradation rate(curing time),the organic matter content,bound water content and pH value of the contaminated soil gradually approached the valley value,and the electrical conductivity,permeability coefficient,liquid limit and plasticity index gradually approached the peak value.Under the influence of the degradation amount(sucrose concentration),the mechanical properties were significantly differentiated,as shown an “S” shape.In the low concentration section,the enhancement of mechanical properties is inhibited;in the high concentration section,the cohesion,internal friction angle and unconfined compressive strength decreased,and the compressibility increased.(3)At the end of degradation,sucrose degradation entered a slow stage.The mechanical properties of the contaminated soil were negatively correlated with the amount of degradation(sucrose concentration)and were significantly weakened.(3)Oligosaccharides infiltration changed the microstructure of soil.The infiltrated oligosaccharides and clay particles formed a composite colloid,which could change the soil structure and reduce the porosity.With the degradation of sucrose,the curing time indicates the degradation rate and reflects the completion of the degradation reaction;Oligosaccharides concentration determines the amount of degradation,indicating the intensity of chemical reaction.With the increase of degradation rate and degradation amount,carboxylic acids and alcohols in soil increase,which corrodes the mineral composition and reduces the electric potential of soil particles.The mechanism of oligosaccharide degradation on the hydraulic properties and physical and mechanical properties of clay was explained from the perspective of affecting the chemical environment of the soi,changing the occurrence form of bound water,and destroying the soil structure.The paper has 67 figures,20 tables,and 111 references.