Study On Containment Performance Of Geosynthetic Clay Liner Exposed To Red Mud Leachate

The leachate of red mud exhibits high p H and is rich in aluminum.Infiltration of red mud leachate into the ground will not only pollute the groundwater,but also affect the engineering properties of the ground soil.This study is financially supported by the National Key Research and Development Plan No.2018YFC1803100 and No.2018YFC1802300.This dissertation presents a systematic study of the engineering characteristics,chemical compatibility,and the hydraulic conductivity(k)and physical and chemical properties of geosynthetics clay liner(GCL)in red mud leachate.The main conclusions are shown as follows:(1)The engineering properties and basic physical properties of CMC-amended,SHMP-amended and XG-amended bentonite slurry are investigated.The results show that CMC greatly improves the swelling performance of bentonite in distilled water,with a swelling index of 40 m L/2g which is consistent with the swelling performance of bentonite in GCL.(2)With the results of the swelling test,modified fluid loss test and flexible wall permeability test,the effects of pre-hydration process and hydraulic gradient on the k of GCL and the influence of red mud leachate on the chemical compatibility of GCL are studied.The results shows that the pre-hydration process has a great impact on the k of GCL,but the type of pre-hydration solution has insignificant effect;The GCL possesses good chemical compatibility of GCL in red mud leachate.The ratio of hydraulic conductivity in the red mud leachate(k_c)to that in the tap water(k_w)k_c/k_w of it is less than 15.During the flexible wall permeability test,no fine particles are flushed out of the testing specimen.(3)The chemical compatibility of four types of bentonite slurries including GCL-bentonite slurry,CMC-amended bentonite slurry,SHMP-amended bentonite slurry,and XG-amended bentonite slurry are investigated by conducting swelling test and modified fluid loss test.The swelling index values of each amended bentonite in distilled water differ from those in red mud leachate.Higher ionic strength of the red mud leachate alters swell index and fluid loss volume.Sodium bentonite(Na B)exhibits poor swelling and containment performance is poor in red mud leachate,whereas the amended bentonites show superior swelling and containment performance.The hydraulic performance of CMC-amended bentonite filter cake in red mud leachate action is similar to that of the GCL-bentonite.The SHMP-amended and XG-amended bentonite filter cakes in red mud leachate have lower hydraulic conductivity than the GCL-bentonite filter cake.action.(4)X-ray diffraction analysis(XRD),Fourier transform infrared spectroscopy(FTIR)and Scanning electron microscope analysis(SEM)are used to investigate the microstructure and surface groups of bentonite in GCL.The XRD test results show that after 150 days,the bentonite sheet structure in the GCL is destroyed.The FTIR test results show that there is insignificant change in the inter-layer bond water.The SEM test results show that after exposed to the red mud leachate,the pore size of increases and formation of flocculation structure is formed.Higher ionic strength exposes greater impact on the microstructures of the GCL specimen.