| At present,landfill liner impermeable layer is commonly used composite liner,natural compacted clay liner,geomembrane single layer impermeable structure.Natural compacted clay systems are generally prone to cracking and difficult soil extraction,while HDPE geomembranes suffer from tearing,bulging and other damage.These conditions seriously affect the service performance of the barrier system.The comprehensive utilisation rate of construction waste and other industrial solid waste in China is low.Based on the above background,this study uses construction waste powder in conjunction with industrial solids to solidify silty soft soil as a new material for landfill liner impermeable layer.Response surface design tests were carried out to determine the optimum proportion of raw materials.Volumetric shrinkage tests,unconfined compressive strength tests,direct shear tests and permeability tests were carried out on specimens under normal temperature maintenance and leachate corrosion to investigate the mechanical and impermeability properties of the material.ICP-OES,XRD,SEM-EDS and FTIR tests were carried out to examine the physical composition and microstructural characteristics of the material,thereby revealing the corrosion mechanism of the modified sludge by waste leachate.The above research can provide data reference for the use of modified sludge as landfill liner barrier material,and also provide new ideas for the comprehensive utilization of solid waste.The main research results are as follows:（1）17 sets of RSM tests were designed to determine the optimum raw material ratio of construction waste powder in conjunction with industrial solid waste modif ying sludge,using the minimum volume shrinkage as the response target,combined with the 3D response surface results,as sludge:construction waste powder:fly ash:sla g powder:desulphurization gypsum=60:17:5:14:4,where the shrinkage rate was 2.183%.（2）The compressive strength,shear strength,and permeability coefficient of modified sludge samples at different curing ages were obtained.The results show that the compressive strength reached 6.93-14.29 MPa,the shear strength was 807.85-1494.50 k Pa,the cohesion and internal friction angle were 334.48-657.83 k Pa and 57.26-70.33°.The permeability coefficient is stable at 3.98-23.1×10-8cm/s.（3）The unconfined compressive strength changes of modified sludge samples were tested and analyzed when they were placed in the air at different concentrations of landfill leachate for 30 to 240 days.It was found that the decrease in the unconfined compressive strength of the samples placed in the air was significantly higher than that of the samples soaked in landfill leachate.After being placed in air and immersed in 100%landfill leachate for 240 days,the unconfined compressive strength of the sample was 6.7-9.4 MPa and 4.0-6.0 MPa,respectively.（4）When distilled water is used as the infiltration medium,the permeability coefficient of the modified sludge is directly proportional to the erosion concentration of landfill leachate,and increases first and then decreases with the prolongation of leachate erosion time.The permeability coefficient of the optimally proportioned modified sludge was 6.41-9.6×10-8 cm/s after 240 days of erosion by different concentrations of leachate;when 100%concentration of landfill leachate is used as the infiltration medium,the permeability curve first increases and then decreases,which is related to the p H of the leachate,inorganic salts,organic matter,Heavy metals and other factors are related,and the permeability coefficient after 240 days of leachate erosion is 9.41×10-8 cm/s.（5）Detection and analysis of the phase composition,surface microscopic morphology and element composition,chemical bond energy,and toxic leaching characteristics of the modified sludge under different landfill leachate concentrations and immersion time conditions,revealing the corrosion mechanism of landfill leachate on the modified sludge. |
PDF Full Text Request