Strength Characteristics And Durability Of Typical Clay Polluted By Life Source Contaminant

In the formation process of polluted clay from life source contaminant,on the one hand,it is subject to seepage and erosion of polluted materials from life source contaminant,on the other hand,the alternation of drying-wetting cycles.of polluted materials also affects the polluted clay,which leads to the change of mechanical properties and durability of clay,and then affects the stability of the project.Therefore,the study on the strength and long-term stability of polluted clay from life source contaminant has important practical value and theoretical significance for engineering practice and soil mechanics research.In this paper,acetic acid polluted clay is regarded as a typical type of life source polluted clay,and a typical life source polluted clay,acetic acid polluted clay,is defined.According to the engineering geological properties of the original clay polluted by life source contaminant,the durability of the clay is studied based on the evolution of pores and fissures,the resistivity and the long-term strength under the drying-wetting cycle conditions.The ideal stress-strain curve of undisturbed clay polluted by life source contaminant was obtained and verified,and the strength prediction formula of acetic acid polluted clay based on soil-water characteristic curve was established.The law and mechanism of pore development of acetic acid polluted clay are revealed.The diffusion process of acetic acid and clay minerals is explained from the perspective of molecular modeling,and then the microstructure of typical living source polluted clay is clarified.The formula of long-term strength of compacted typical clay polluted by life source contaminant based on resistivity is obtained.The main research results are as follows:1)It is found that the main properties of the clay polluted by life source contaminant change with the seepage depth of the polluted material.With the increase of depth,the liquid limit,specific gravity,conductivity,salinity and clay content first increased and then decreased with the increase of depth,while the pH value showed a law of first decreased and then increased.The undisturbed samples with different water content tend to "strain hardening type" after pollution.In the shear indexes of soil before and after pollution,the change of internal friction angle is not obvious,while the cohesion is obviously reduced.2)The ideal elastic-plastic stress-strain relationship of unsaturated clay polluted by life source contaminant is established.The soil-water characteristic curves of the original life source polluted clay,remolded polluted clay and original unpolluted clay,as well as their shear characteristics at different mass moisture content(17%,20%,23%,26%,30%)were obtained through the field sampling of the original clay polluted life source contaminant.Based on the soil-water characteristic curve and unsaturated soil strength theory,the ideal elastic-plastic stress-strain relationship of unsaturated clay polluted by life source contaminant is obtained,which accords with the measured stress-strain relationship of undisturbed polluted clay.3)The mechanical characteristics of clay polluted by acetic acid in different concentrations were clarified.The soil-water characteristic curve of clay polluted by different acetic acid concentration was analyzed.The triaxial shear properties of acetic acid polluted clay under four kinds of confining pressures were tested,and the stress-strain curve was compared with that of remolded polluted clay.The results showed that the peak value of stress-strain curve of acetic acid polluted clay was significantly lower than that of polluted clay,and the softening of acetic acid polluted clay was significant.It fully shows that there is a component(presumably carbonate)that increases the strength of caly in the polluted soil.4)A montmorillonite model with different concentration of acetic acid was established.The engineering geological properties and microstructure characteristics of typical clay polluted by life source contaminant were obtained,and the micro diffusion process and change rule of acetic acid in montmorillonite were revealed.With the increase of the concentration of acetic acid,the macropores in the pores of acetic acid increase,the porosity increases,the coefficient of pore heterogeneity increases,and the gradation tends to be good;however,the molecular simulation shows that with the increase of the concentration of acetic acid,the diffusion ability first increases and then decreases.When it is in the range of 0.2-0.4mol/L,the mobility of acetic acid is the strongest.5)Reveal the dynamic development process of water loss fracture of typical clay polluted by life source contaminant,and the change rule and mechanism of resistivity and strength parameters under the condition of drying-wetting cycles.Acetic acid with the concentration of 0.4 mol/L had the greatest effect on fracture development,but when the concentration of sodium carbonate was higher than 0.4 mol/L,fracture development was inhibited.The resistivity of compacted typical clay polluted by life source contaminant increases with the increase of drying-wetting cycles.With the increase of resistivity,the cohesion of clay decreases and the internal friction angle keeps stable.When the number of drying-wetting cycles reaches 4,the clay properties tend to be stable.6)The influencing factors of the durability of clay polluted by typical life source contaminant are defined,and the calculation method of long-term strength of clay polluted by acetic acid based on resistivity parameters is deduced.The long-term strength of acetic acid polluted clay is affected by matrix suction,mineral composition,pollutant concentration,pore fracture structure and development.Among them,fracture development is the main factor to reduce the long-term strength of soil,while mineral composition and pollutant concentration directly affect the development of pore fracture structure,and ultimately affect the resistivity of clay.Therefore,the long-term strength calculation method of acetic acid polluted clay based on resistivity parameters is deduced by establishing the resistivity formula of acetic acid polluted clay.There are 94 figures,32 tables and 254 references in the paper.