Investigation Onthe Regularityof Contaminant Migrationthrough Compressible Media

In construction of the simple waste landfill site,it usually chooses the thick,high water content and void ratio clay layer as the natural impervious barrier.As the increasing height of waste loading on the surface,the clay layer will undergo a large deformation,of which the engineering practice showed that,the consolidation theories based on small strain can not accurately predict the consolidation process,and also can not accurately predict the regularity of contaminant migration and transformation through compressible media.So it is very necessary to take the deformation of the clay layer into account in the investigation of the regularity of the contaminant migration and transformation through the clay barrier.Due to the case of the contaminant migration and transformation through the clay barrier that has a large deformation.The main achievements are shown as follows:1.Based on the Gibson one-dimensional consolidation theory,one-dimensional large deformation consolidation governing equation of homogeneous soil,which considering the self-weight of soil,is established.Based on the large deformation consolidation theory of multi-layered foundation,one-dimensional large deformation consolidation governing equation of layered soil,which considering the self-weight of soil,is established,and solved by the Crank-Nicholson finitedifference scheme.2.Based on the Gibson one-dimensional consolidation theory and the dispersion and advection equation of contaminant in saturated porous media,a theoretical model for coupled one-dimensional and one-dimensional large strain consolidation and solute transport is here in presented,in which soil weight,adsorption and biodegradation effect are taken into account comprehensively;Combining the large deformation consolidation theory of multi-layered foundation with the contaminant transport theory,a one-dimensional mathematical model for contaminant migration and transformationin large deformation soil,which is layered.The main characteristic of these models is considering the effect of soil deformation under loads and different adsorption modes on the migration of contaminant.The governing equation is solved by the finite difference scheme.3.Numerical analysis of one-dimensional migration and transformation of contaminant in large deformation soil under the condition of non-linear adsorption.The analysis results show that,the thickness of the clay barrier,the coefficient of hydrodynamic dispersion and the biodegradation effect play an important influence on the migration of contaminant.When the concentration of contaminant is high,The results will be commanded by assuming the isothermalnon-linear adsorption.4.Research on one-dimensional mathematical model for contaminant migration and transformation in large deformation soil,which is layered.The effect of different adsorptions of soil particles on the migration and transformation of contaminant in soil are studied,the sensitivity of the related parameters and the action of the dominant terms are analyzed.The results show that,under the same conditions,the distribution of profile concentration at different working conditions is different.The concentration distribution at the interface of the soil forms a mutation.But the sequence inversion has little effect on the breakthrough time of contaminant across the liner.Secondly,the biodegradation effect has little effect on the concentration of contaminant at the beginning of the transformation rule,but as time goes on,the biodegradation effect will incredibly reduce the growth rate of the contaminant concentration.And the concentration of contaminant in soil is negatively correlated with the biodegradation coefficient.The more the biodegradation effect,the less the time needed to reach the steady state.It means a lot for evaluating the long term obstructing capacity of the barrier.5.Numerical analysis of two-dimensional migration and transformation of contaminant in large deformation soil under the condition of linear adsorption.Using the alternating direction implicit difference scheme(ADI)to solve the governing equation.The thickness of the clay barrier,the coefficient of the horizontally hydrodynamic dispersion,the coefficient of the vertically hydrodynamic dispersionand the biodegradation effect on the migration and transformation of contaminant in soil are analyzed.The results show that,the hydrodynamic dispersion can significantly affect the migration of contaminant in soil.The hydrodynamic dispersion effect plays an important role in the migration and transformation of contaminant.The results of the investigation show that,the geometric non-linearity of large deformation soil has an important influence on the migration and transformation of contaminant in the clay.The large deformation effect can't be neglected in the study of the obstructing capacity of the natural thick clay barrier.The presented solutions can be used for preliminary design of landfill liners.