The Feasibility Study Of Straw Fiber Modified Clay As Impervious Landfill Liner Material

Crop straw fiber was used in the compacted clay liner to improve the resistancecharacteristics of the carrying capacity of the liner system, in order to aiming at thekey scientific issue of compacted clay liner cracking failure in landfill running. Forevaluating the feasibility of straw fiber modified clay as landfill liner materials,compacted clay cracking test was carried out. The laws of modified clay cracking inwetting-drying cycles were researched, and the best mix proportion of crop strawfibers. The strength and deformation of different straw fiber content and acid-basechemical solution corrosion of compacted clay was researched by indoor soil test.The microscopic morphology and pore structure of acid-base chemical solutioncorrosion straw fiber compacted clay was analyzed by microstructure experiment.The law of liner deformation and failure and transport tendency of contaminantspread was numerical simulated under seepage-stress-solute coupling. Based onthe results:(1) Wetting-drying cycles had significant effect on the cracking of compactedclay, with the increase of the number of the cycles, the cracks became increasinglyapparent. The straw fiber improved clay has better resistance characteristics tocracking, and CIF first increased and then decreased. When the fiber content was0.3%, CIF was0.00813.(2) The carrying capacity was the best when the fiber content was0.3%. Theunconfined compressive strength was459.15kPa, and c was80.97kPa and φ was21.06°. The permeability coefficient was5.0×10-8cm/s, and α was0.18MPa-1, andthe minimum Cc was0.065MPa-1. Es was9.356MPa. Acid-base chemical solutionthe straw fiber improvement clay had significant affect to strength characteristics.(3) Acid-base chemical solution had a large impact on the microstructure ofcompacted clay. Clay surface roughening, flatness decreased significantly andravines, and the specific surface area increased. Pore size, the second hole and thehole increased, the particle arrangement by the evolution of a sheet pile structure to the point-point arrangement structure. Composition of organic matter decompositioncorrosion under the action of acid-base chemical solution, and the acidic corrosion amuch greater extent than alkaline conditions.(4) Based on the results of numerical simulation as deformation andcontaminant transport of landfill liner with straw fiber modified clay, After50daysof landfill running modified clay liner deformation reached steady state, the strainwas2.84%. The point of landfill liner on deformation is a axisymmetric variation, itsdeformation is maximum around the left and right border of landfill liner layer.Eachpoint of landfill liner layer on the modified clay concentration increased with theincrease of the time,and the pollutant concentration decreased with the increase ofdepth of the cushion layer.In600days, leachate pollutants crossed through linerlaye. Pollutant concentration change is axisymmetric, concentration of pollution waspeak value on the axis of liner layer.