Study On Capacity Of Fly Ash Modified Landfill Clay Liner

Sanitary landfill is the trash main processing method of our country city life. In alandfill, clay (natural clay, compacted clay, etc) with the little permeability coefficient,strong capability of cutting corrupt, low price advantage, so it is widely use in alandfill pad system. However there is high quality of concentration of hydrophilicmineral in cohesive soil, under water is easy to expand, and it will contract after lossthe water. So in the dry-wet circulation, cold regions under the condition offreeze-thaw cycle may induce clay liner crack; In addition to some of the claycomposition may have a reaction with landfill leachate, which causes the dissolved. Itwill also make clay lining of the permeability coefficient increase; Once the clayseepage control layer destruction, it is difficult to natural healing, seal, need to punchthrough the landfill to repair, which is not only construction difficulties, but alsoincrease the operation and maintenance of the landfill costs, increased the risk of theleachate contamination leak out.In view of the above problems, we select the economic and effective clayseepage control layer added material-fly ash, fly ash as industrial solid waste not onlyhave large output, and polluted surroundings, choose the fly ash as modified packingcan not only improve the characteristics of clay, also can achieve the purpose of usingwaste treat waste, consider through the static adsorption test, prevent craze experimentand dynamic soil column simulation experiment, study the soil mechanics propertiesof natural clay and fly ash modification of clay, seepage control function, preventcracking resistance, the difference in intercepting performance. the results are asfollows.(1) through the soil mechanics experimental study the influence on natural claysoil mechanics properties with different amount of fly ash, the results of the studyshow that added10%,15%,20%,25%,30%fly ash to natural clays, each differentadditives modification of the fly ash’s IP is in between10%and30%, fitting therequirements of the materials for seepage control. Fly ash as modified packing thatcan be mixed with the natural clay.When adding amount of fly ash were10%,15%,20%,25%and30%,themaximum dry density of modified clay were1.85g/cm3,1.83g/cm3,1.82g/cm3,1.80g/cm3,1.79g/cm3. The optimum moisture content were19.50%,19.81%, 20.20%,22.54%,23.67%. The modification of fly ash clay maximum dry density ρwill decrease with fly ash proportion increasing, deand all of the them are belownatural clay’s maximum dry density1.97g/cm3. It can be inferred that fly ash asmodified packing can decrease the plasticity of the packing soil, therefore the amountof fly ash should not be exorbitant.(2) through the dynamic simulation study that the influence on the performanceof the natural clay seepage control with different adding amount of fly ash, theresearch result indicates that:1) different proportion0f fly ash modification of clay’s adsorption balance timeto NH4+-N and COD points for12h and24h. Determine the time of adsorptionequilibrium, the follow-up experiment use it as the time of adsorption equilibrium.2) according to the different soil sample’sCOD and NH4+-N DengWenXian wecan get adsorption relationship is30%fly ash>25%fly ash>20%fly ash>15%flyash>10%fly ash> clay. Clay itself adsorption effect is the worst, this is mainlybecause the chemical and physical properties of fly ash.3) the permeability coefficient from low to high is20%fly ash is in themodification of clay,10%fly ash modification of clay,15%fly ash modification ofclay,25%fly ash modification of clay,30%fly ash modification of clay. with the flyash addition amount increase the permeability coefficient of the lining is decreasing,starting stage in10-5magnitude, when adding amount is20%,the permeabilitycoefficient decrease to a minimum, achieve10-7magnitude, accord with therequirement of the lining of seepage control layer, then with the increase of addingamount of fly ash, the permeability coefficient gradually increase to10-6magnitude.That indicate taht fly ash’s best add ratio is20%.(3) through the static saturated experiment and the cracking experimental studythe influence to natural clay on the performance of the cracking by different addingamount of fly ash, research shows that comprehensive consideration of the threefactors, the crack’s number, the maximum crack’s length and the maximum crack’scrack width,only20%fly ash modification of clay performance is better than thenatural clay itself. In all experiments, sample body shrinkage rate increase with theincrease of sample optimal moisture content.30%fly ash modification of clay’s bodyshrinkage is maximum,it is0.32% (4) through the dynamic simulation study the cases of adding amount of the flyash20%, fly ash ‘s influence on cutting performance of natural clay, the researchresult indicates that the goal of pollution Cu, Zn and Cr’s adsorption mainly in thefirst three layer, the biggest adsorption were0.097mg/g,0.1mg/g and0.0068mg/g.Because of the concentration of leachate contamination is low, and the modificationof clay’s cutting capacity cannot be judged, if we want to get it,we need to furtherincrease the concentration of the goal pollutant in landfill leachate.In a word, from the consideration on the physical properties,chemical propertiesand engineering properties, fly ash is favorable add materials; The addition of fly ashcan strengthen the cracking resistance, greatly enhance the lining’s interceptionamount of pollutant, optimal add ratio is20%.This paper determined the the optimal add ratio of fly ash as modification of thepacking, the different proportion of the modification of clay’s influence on differentperformance, providingfor theoretic basis for this new modified packing used in clayseepage control layer and the engineering application.