Study On Non-darcy Flow And Antifouling Performance Of Clay Modified By Sand Under Temperature

The compacted clay liner in the antifouling barrier of the landfill will produce cracks due to some reasons such as drying,the existence of cracks may provide a priority channel for the leachate to break down the antifouling barrier,so as to pollute groundwater and surrounding soil environment.Mixing sand in clay can reduce its shrinkage and avoid its cracks,but there is no study on permeability and antifouling performance of sand-clay.Therefore,this paper analyzes the influence of sand content and temperature on the non-Darcy flow parameters of sand-clay under different sand content and temperature conditions;calculating the intrinsic permeability of the sample based on the seepage theory,and establishing the quantitative relationship between the threshold gradient on and the intrinsic permeability.The influence of non-Darcy flow parameters on the service life of single liner and double liner under different working conditions is analyzed by numerical calculation.The specific research contents are as follows(1)Study on the influence of sand content on permeability of sand-clay.In this part,the sand content of 5 groups were 10%,30%,40%,50%and 60%respectively.Through the permeability test of sand-clay with different sand content,the change rules of permeability coefficient k and threshold gradient i0 at different amount of sand are studied,and then the intrinsic permeability K can be calculated based on the seepage theory,it is found that there is a good exponential relationship i0=A×KB between the threshold gradient and the intrinsic permeability of sand-clay materials.(2)Study on the influence of temperature on the permeability of sand-clay.Four temperature gradients 30?,40?,50? and 60? were set by the developed temperature controlled flexible wall permeameter,and sand-clay samples with 30%sand content were selected,through the permeability test of sand-clay at different temperatures,the change rule of permeability coefficient k and threshold gradient i0 at different temperatures is studied,considering the influence of temperature on the viscosity and density of the permeate,the intrinsic permeability of the sample is calculated by combining the seepage theory,it is also found that there is a good linear relationship between the threshold gradient i0 and the intrinsic permeability K in the double logarithmic coordinate.(3)Influence of permeability coefficient on service life of liner.Considering the difference between the real permeability coefficient and the measured permeability coefficient,combined with the change of leachate head and pollutant concentration,the service life of single liner and double liner are calculated respectively.The calculation results show that the difference between the real permeability coefficient and the measured permeability coefficient has less influence on the service life of the liner under the condition of low water head than that under the condition of high water head,while the effect of the difference between the real permeability coefficient k0 and the measured permeability coefficient k1-3 on the service life of the liner under the condition of variable water head is opposite to that under the condition of variable concentration.(4)Influence of threshold gradient on service life of liner.Considering different threshold gradient,combined with the change of leachate head and pollutant concentration,the service life of single liner and double liner are calculated respectively.The calculation results show that the difference of the threshold gradient has less effect on the service life of the liner under the condition of low head than that under the condition of high head,while the difference of the threshold gradient under the condition of variable concentration has little effect on the service life of the liner compared with that under the condition of variable head.