Study On The Effect Of TCs And SAs Antibiotics On The Engineering Properties Of Conhesive Soil And Their Migration Law

A series of physical,chemical and biological reactions occur between the antibiotics entering the soil environment and the soil,resulting in structural changes of the soil,resulting in uneven settlement and cracking of the superstructure.Therefore,it is of great significance to study the engineering properties of antibiotic contaminated soil and the process of antibiotic migration in soil to reveal the evolution law and mechanism of the engineering properties of antibiotic contaminated soil,as well as the migration characteristics and mechanism of antibiotic contaminated soil in soil.In this paper,six typical tetracycline antibiotics(TC_S)and sulfamilamide antibiotics(SA_S)including oxytetracycline(OTC),aureomycin(CTC),Sulfadiazine(SD),sulfamilamide dimethyrimidine(SMD),sulfamethoxazole(SMZ)and Sulfapyridine(SPY)are selected.The variation of engineering properties of contaminated soil with the types and concentrations of TCs and SAs before and after contamination is experimentally studied,and the evolution mechanism of engineering properties of contaminated soil is revealed.With the help of self-developed pressure percolation apparatus,the changes of soil moisture content and the concentrations of OTC and SD antibiotics at different profile depths with the change of migration time are studied.The spatial distribution characteristics of water content of two kinds of antibiotics contaminated soil and the migration of antibiotics in soil are revealed.Determine the OTC shear strength model,compare and analyze the ultimate bearing capacity of the OTC contaminated foundation soil before and after the pollution evaluation,and explore the change mechanism of the ultimate bearing capacity of the OTC contaminated foundation soil.The results show that:(1)(1)The liquid limit and plasticity index of six kinds of antibiotics contaminated soil are negatively correlated with the concentration of antibiotics.In terms of plasticity,the plasticity limits of OTC,CTC,SD,SMZ and SPY contaminated soils are positively correlated with the concentration of antibiotics,but the plastic limit of SMD contaminated soil is negatively correlated with the concentration of antibiotics.OTC has the most significant effect on plasticity,while SMZ has the weakest effect.(2)The shear strength of the six antibiotics fluctuat greatly at low concentration,but show no obvious rule.When the concentration of antibiotics is high,the shear strength of the six antibiotics contaminated soil is positively correlated with the concentration.Compared with the uncontaminated soil,the shear strength of OTC,CTC and SD increase at high concentration,while the shear strength of SMZ,SMD and SPY decrease at high concentration.(3)Under the seepage of OTC and SD contaminated solution,the permeability coefficient of soil is negatively correlated with its concentration.Compared with the uncontaminated soil,the permeability of the clay added with antibiotics decrease,and the effect of OTC on the permeability of the clay was greater than that of SD.(2)Water transport in soil can be divided into three stages:initial flat stage,rapid growth stage and stable change stage.At each sampling point,the water migration rate of OTC is higher than that of SD,and the migration rate decrease as the sampling points moved up.The OTC concentration is smaller than the SD concentration.(3)Mechanism analysis:(1)The easily ionized and easily polarized functional groups of SA_S and TC_Santibiotics themselves combine with the adsorption sites on the surface of soil organic matter(SOM).With the increase of SA_S and TC_S concentration,the organic matter in soil forms multi-layer adsorption,which makes the adsorption capacity of antibiotics on the surface of inorganic minerals increase rapidly.(2)The full mixing of SA_S and TC_S antibiotic suspension with soil particles results in the exchange of cation and cation between the two,which changes the concentration of cation and cation in soil and results in the change of the properties of clay mineral particles in soil,resulting in the change of plasticity,shear strength,permeability coefficient and water migration rate.(4)Under each foundation form,the ultimate bearing capacity of OTC contaminated soil increases by about 30%.When the OTC concentration is between 0.50-0.93g/kg,the ultimate bearing capacity of contaminated soil is lower than that of unpolluted soil.When the OTC concentration is between 0.93-4.00g/kg,the ultimate bearing capacity of contaminated soil is higher than that of unpolluted soil.(5)When the OTC concentration is low,the ultimate bearing capacity of the contaminated soil decreases and the internal stress changes.On the one hand,When OTC concentration is high,the ultimate bearing capacity of contaminated soil increases.The paper contains 60 figures,37 tables and 100 pieces of refer.