Experimental Study On The Physical And Mechanical Properties Of Volatile Non-aqueous Phase Organic Compound Contaminated Soil

Coastal regions of china are mostly multifunctional ports and chemical industry parks.A large number of spit and leakage generated from exploitation?refinement?transportation and application of oil and oil-products have contaminated coastal sedimentary clays in varying degrees.Contaminated soils affect the reliability and stability of housing construction built on them.This research chose different reconstituted clay samples as research objects,contrasted the changing characteristics of saturated clays contaminated in different degrees by adding Petroleum hydrocarbon and discussed the effect rule and action mechanism of mechanics property of saturated clays by volatile non-aqueous phase organic contamination.The main research contents and conclusions are as follows:(1)Tests of physical performance including density of soil particles,liquid and plastic limits,rate of swelling on four types of virgin and diesel contaminated reconstituted clays(Fuzhou soil,Taizhou soil,sodium-based bentonite and calcium-based bentonite)were conducted.The results showed that influence of liquid and plastic limits by diesel contamination was related to vary factors such as type of soil and corresponding initial liquid limit.liquid limits of the three soils except Taizhou soil increased along with diesel-content increasing.As for plastic limit of bentonite,the change trend of which was positive corrected with contaminated degree while Taizhou soil and Fuzhou oil were the opposite.(2)One-dimensional consolidation and permeability tests of different contaminated degrees on reconstituted and preconsolidation reconstituted clays of Fuzhou soil,Taizhou soil,respectively,were conducted.The changing compressibility behaviors mechanism of different soils after contaminated:connectors were formed between diesel and soil particles which led to stronger resistance to compression and larger reconstituted yield stress of diesel-contaminated saturated soil.Compared to high liquid limit clay,the connector phenomenon of low liquid limit clay was more obvious and the changing difference of compression characteristic along with contaminated degrees was larger.During the same soil sample,compared to sealed reconstituted clays,unsealed reconstituted clays were easier to compress and the destruction degree of connector was more serious due to the volatilization of diesel,which led to greater compressibility and smaller reconstituted yield stress.Due to the enrichment of diesel in clay,the e100*value of oil contaminated soil was larger than that of uncontaminated soil,and the CC*was lower.Thus,the virgin compression lines VCL below the curve of compression.(3)Through triaxial consolidated-undrained shear tests of Fuzhou reconstituted clays which had different initial oil content,the normalization properties of stress-strain and pore pressure strain after diesel contamination were described.The results showed that under different stress levels,water content?liquid limit and diesel content had a great effect on the stress-strain,pore-water pressure behavior,undrained strength envelope and critical strength line of reconstituted clays.Undrained shear strength had a linear relationship with diesel content.Soil strength decreased along with the increase of diesel content.when Su/?' 3 tended to 0.33,relation curve and strength line(ISuL)of reconstituted clays were completely coincided.(4)The conclusion that the compression behavior and strength properties of contaminated soil were determined by the liquid limit of soil after diesel-contaminated was drew by analysis of the data of one-dimensional consolidation test of diesel-contaminated reconstituted clay by w/wL and data of triaxial consolidated-undrained shear tests.The empirical formula was deduced by utilization of existing data and the liquid limit predictor formula of diesel contaminated clay.The compression index,reconstituted yield stress and undrained shear strength of Fuzhou diesel-contaminated reconstituted clays can be calculated by the empirical formula under the known of three basic physical parameters:liquid limit of pollution-free clay wL(%),oil content of contaminated clay woil(%)and initial water content w(%).