Experimental Study On Physical–mechanical Behaviour Of Reconstituted Clays With And Without Heavy Metals

In environmental dredging projects,how to effectively handle river and lake reservoir sediments is the critical issue.The sediment is characterized by high water content and high heavy metal ion content,and it is important to clarify the physical-mechanical properties of the contaminated sediment.In this study,kaolin,sodium bentonite and natural sedimentary clay with illite as the main mineral constituents were selected as the origin clay,and different amounts of Cu²⁺,Zn²⁺and Pb²⁺were added to prepare artificial heavy metal contaminated sediment,and a series of experiments were conducted to investigate the influence of heavy metal ion concentration,mineral constituents and initial water content on the physical and mechanical properties of the contaminated clay.The main researches and conclusions are as follows:(1)By studying the changes in the basic physical properties of heavy metal contaminated soils,it was observed that the liquid limits and plastic limits increased with the increase in ion concentration after adding heavy metal to the low-activity soils,while the high-activity soils showed the opposite behaviors.The mechanisms of variation are similar to established mechanisms for the influence of salinity on boundaries moisture content of soils.(2)A one-dimensional consolidation-permeability test and a fall cone test for heavy metal-contaminated soils were carried out to investigate the effects of pore fluid ion concentration on the mechanical properties of the soils.The experimental results show that the quantitative relationship between the mechanical properties and physical parameters of heavy metal-contaminated soils is basically consistent with the existing physical-mechanical mathematical description of uncontaminated soils.(3)The mechanism of heavy metal ion induced changes in the mechanical properties of the contaminated soil such as compression,permeability,strength,etc.is revealed,which is essentially attributed to the changes in physical properties caused by the addition of heavy metal ions.