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  • Author: Eugeniusz Koda x
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Efficiency assessment of vertical barriers on the basis of flow and transport numerical modeling

Abstract

The construction of cut-off walls is a common solution applied in such disciplines as land reclamation and landfill containment. Most commonly the construction of vertical barriers is based on cut-off wall mono or diphase technology with the use of bentonite-cement mixture as a filling material. The content of the paper is focused on groundwater flow and transport numerical modeling conducted on landfill areas where vertical bentonite barriers were constructed. The modeling process was conducted with the use of FEMWATER software which employs analysis based on finite element method. There are two examples of the software application presented in the paper which concern such case studies, i.e., reclamation of Radiowo and Łubna landfill sites. These examples are provided to prove that the appropriate investigation of ground conditions as well as definition of initial and boundary conditions and correct selection of material parameters to be fed into the software, are crucial for the overall modeling process. Moreover, the comparison of results obtained from the numerical modeling and the groundwater monitoring on site is presented for one of the case studies.

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Modelling groundwater flow and nitrate transport: a case study of an area used for precision agriculture in the middle part of the Vistula River valley, Poland

Abstract

The present paper discusses studies related to the preparation of a hydrogeological model of groundwater flow and nitrate transport in an area where a precision farming system is applied. Components of water balance were determined using the UnSat Suite Plus software (HELP model), while the average infiltration rate calculated for the study area equalled 20 per cent. The Visual MODFLOW software was used for the purpose of modelling in the saturated zone. Hydrogeological parameters of the model layers, inclusive of hydraulic conductivity, were defined on the basis of results of column tests that were carried out under laboratory conditions (column experiment). Related to the dose of mineral nitrogen used in precision fertilisation (80 kg N/ha), scenarios of the spread of nitrates in the soil-water environment were worked out. The absolute residual mean error calculated for nitrate concentrations obtained from laboratory and modelling studies equalled 0.188 mg/L, the standard error of the estimate equalling 0.116 mg/L. Results obtained were shown graphically in the form of hydroisohypse maps and nitrate isolines. Conclusions were drawn regarding the possibility of using numerical modelling techniques in predicting transport and fate of nitrates from fertilisers applied in precision agriculture systems.

Open access
Analysis of Embedded Retaining Wall Using the Subgrade Reaction Method

Abstract

This paper analyzes the distribution of internal forces and displacements of embedded retaining wall in Quaternary deposits and Tertiary clays. Calculations have been based on the Subgrade Reaction Method (SRM) for two different types of earth pressure behind the wall (active, at-rest) in order to show the differences resulting from adopting the limit values. An algorithm for calculation of “cantilever wall” using the Mathematica program was proposed.

Open access