Researchs On Mechanical Properties And Curing Measures Of Rock-soil Invaded By Heavy Metals

Heavy metal pollution rock-soil widely distributed in our country, especially in Guangxi, Yunnan and other places which have non-ferrous mineral resources.The colloid between particles was corroded and cementing strength was destroyed after invaded by heavy metals,which changed the internal structure and properties of soil mass,such as the void ratio and compressibility increasing, the shear strength reducing, the bearing capacity declining.At present, the research achievement of engineering properties,curing mechanism,prevention and controling measures for contaminated rock-soil was less. Mostly disposed as general soil or not disposed in project construction,which led to engineering accidents,such as subgrade, slope crack, building foundation cracking and collapsing and so on.So researching the engineering properties, the constitutive relation, the curing mechanism and control measures of contaminated rock-soil. That was of great significance to evaluate and control land (road), slope of heavy metal pollution, and used soil resources of heavy metal pollution rationally.The paper investigated the surrounding soil influence of miner-al exploring with the object of typical lead and zinc mine. we ana-lyzed the mechanism and the causes about soil pollution of the mi-nefield.Through establishing migration experimental model of heavy metal pollution, the main pollution elements Cd (cadmium), Pb (le-ad), Zn (zn) migration characteristics and linear relations were obta-ined by adopting the method of partial least squares (PLS) establish the linear regression curve equation migration. According to the st-udying plant’s self-purification capacity of heavy metals, The consi-stent relationship between plants accumulation and heavy metals mi gration was obtained. The results showed that:migration characteri-stics of Cd (cadmium) was stronger. Not control by self-purification capacity of plants,the migration characteristics of Pb (lead) was we-aker because of impacted by self-purification capacity of plants mo- regreatly, the migration characteristics of Zn (zn) was weakest as to control by self-purification capacity of plants.A heavy metal contaminated soil with organic matter was stud-ied by CD test, CD comparison tests were done with undisturbed and added agent contaminated soil under low and relatively high c-onfining pressure, and two kinds of mechanical volumetric change-ng characteristic curves were drawn.Based on the results of laborat-ory tests,a two yield surfaces model of contaminated soil with vo-lumetric change was established that got rid of the deficiency of s-ingle yield surface model, which can express the process of volum-etric change preferably. The results showed that the curing agent c-ould dramatically improve the peak strength of heavy metal conta-minated soils, and ameliorate volumetric expansion and contraction under low and relatively high confining pressure effectively.The nu-merical simulation agreed well with the data of large-scale triaxial compression test, which proved the model to be of the priority in-describing the volumetric behavior of heavy metal contaminated soil.A heavy metal contaminated soil was studied by CU test, dir-ect shear test and compression test. Under confined pressures of100、200、300kPa,CU tests were done with general soih、contamin-ated soil(The heavy metals ratios were1%,2%,3%and4%respec-tively).The results showed that the strength of contaminated soil co-uld dramatically reduce with heavy metal content increasing.Accreti-on of confined pressure could not affect the strength of contaminat-ed soil insignificantly. The peak strength would reduce by10%-15%when mass ratio was lower than0.01, and reduce by40%-50%when mass ratio was more than0.03. Direct shear tests showed t-hat the shear strength was being reduced by10%-15%and45%-55%respectively when mass ratio was lower than0.01or more tha n0.03.The shear strength was proportional to thevertical stress when mass ratio was lower than0.01, with the curves being almost par-allel to each other, and the curves expression was irregular when mass ratio was more than0.03.Compression tests showed the differ- rence in decrement between general soil and contaminated soil was greater and more obvious when mass ratio was more than0.05. B-ased on the Mastsuoka-Nakai criterion and the results of laboratory tests,a constituteive relation of contaminated soil was established, which showed more realistically in describing the strain-stress relati-on of heavy metal contaminated soil.The performance changes of the heavy metal contaminated roc-k were analyzed under different test conditions.According to the te-st results, the rock weathering velocity and the mechanical properti-es which influenced by heavy metal content, the impact of heavy metals on rock hydration and hydrolysis mechanism was discussed. According to the size relationship of intrusion performance,extension performance of heavy metal elements,the3D constitutive model was set up for contaminated rock with fracture surface damaged,and the model fitting results and test results were compared.The results sho-wed that thickness of electric double layer increased by heavy met-al elements, repulsive of diffusion layer was changed,hydration exp-ansion stress increased,which led to the expansion and extension of rock fracture surface, the intensity of rock was decreased. Hydrolys was constant of heavy metal elements formed a new M-OH, which promote the hydrolysis of rocks. The relationship of heavy metal p-ollutants mass ratio and rock weathering was polynomial type,and the curve was parabolic.The fitting results of the3D constitutive model and test results had a good consistency.