Investigation Of Engineering Properties Of Vertical Cutoff Wall Material Based On Soil-modified Bentonite

The rapid development of China’s economy is inseparable from the boost of industry.In response to the requirements of sustainable urban development,a large number of industrial enterprises were shut down or relocated,resulting in a large number of abandoned industrial pollution sites.Soil-bentonite vertical cutoff wall is an effective solution,which can effectively prevent the pollution of soil and water nearby due to the leakage of leachate.Limited by the lack of sodium-bentonite,the bentonite used in the soil-bentonite vertical cutoff wall in our country is mainly sodium activated calcium-bentonite,and its engineering properties are still far behind the sodium-bentonite.However,the use of polymer modified of sodium activated calcium-bentonite can significantly improve its various properties.At present,there is little research on this aspect in our country.Therefore,it is urgent to carry out the research on the polymer modified of sodium activated calcium-bentonite,and to clarify the workability,compressibility,consolidation properties and hydraulic conductivity of the polymer modified bentonite when preparing the vertical cutoff wall backfill,and to determine the content of bentonite required for achieving hydraulic conductivity limit regulatory.Based on the above,this thesis carried out the research on the related engineering properties of soil-bentonite vertical cutoff wall materials,and the workability,compression and consolidation properties and hydraulic conductivity of sodium activated calcium-bentonite,polymer modified bentonite and the backfill made from the two kinds of bentonite were studied.Qualitatively evaluated the modification effect of the polymer monomer on sodium activated calcium-bentonite.The main research contents and conclusions are as follows:（1）Two kinds of bentonite content which can meet the construction workability during the preparation of bentonite slurry were defined;the corresponding relationship between the slump of mini slump tube and water content of two kinds of vertical cutoff wall backfill under different initial bentonite content is defined;it is found that the construction workability of polymer modified bentonite is obviously better than that of sodium activated calcium-bentonite.（2）The compression and consolidation properties of two types of vertical cutoff wall backfills under controlled water content were revealed.It was found that the compressibility of polymer modified bentonite were lower than that of sodium activated calcium-bentonite,and the consolidation properties is more stable than that of sodium activated calcium-bentonite.（3）The variation law hydraulic conductivity of two kinds of vertical cutoff wall backfills are described when the permeating liquid is tap water,steel slag leachate and Ca Cl₂concentration of 50 mmol/L were elaborated.The content of bentonite required for achieving hydraulic conductivity limit regulatory(hydraulic conductivity<10^-9 m/s)is determined.The hydraulic conductivity of polymer modified bentonite is lower than sodium activated calcium-bentonite.