The Research Of Non-uniform Penetration Phenomenon In The Homogeneous Porous Medium

Groundwater resources, as the significant components of water resources, areconsidered as the principal elements impacting economic and social developmentsamongst arid and semi-arid areas. Facing the grim situation of groundwater pollution,especially in porous media, research on pollutants migration in groundwater is at theprimary stage. The laboratory experiment on hydrogeology in porous media is regarded asan essential mode to study the migration rule of solute in this pattern. Homogeneousmedium is frequently adopted in experiments accounting homogeneous flow should behomogeneous. However, quantities of experiments demonstrate that heterogeneousseepage phenomena exist even in a homogeneous medium and once this happens, it wouldexert an influence on groundwater seepage as well as the spatial and temporal distributionof solute. Moreover, it would leave an effect on handling laboratory results correctly.Based on this, non-uniform seepage phenomenon should cause relevant scientific workers’attention.Based on six groups of medium and coarse sand seepage experiments in distincthydraulic gradients, this dissertation focuses on the rule and factors of non-uniformpenetration phenomenon. Through the analysis of SPSS, it is calculated that critical effectfunctions illustrating differently on various observation position in the process of flow.Main achievements and conclusions are as follows:1. Towards medium and coarse sand in homogeneous medium, there could benon-uniform penetration phenomenon when the solute transport status is not an idealpiston movement state during the seepage state.2. In the upstream of percolation channel, due to the solute went access to it evenly,the concentration in the channel were distributed uniformly, characterized as piston movement. The time difference of peak tracker concentrations illustrated amongst0to10minutes in the area of observation hole on both sides of the border and mainstream areasin each experiment group. Nonetheless, with the increase of solute transport distance,there was non-uniform seepage phenomenon, which manifested that the migration speedof solute near the border was faster than it in the mainstream and became increasinglyobvious from the upstream to the downstream. The time differences enlarged to50to100minutes. According to seepage velocity calculated by data from observation holes anddispersion coefficient, it was illustrated that the changes of dispersion in medium were notsignificant while the seepage velocity became faster in the area of borders and slowernearby mainstream.3. Based on the qualitative analysis of heterogeneity characteristics of seepage andsolute transport, we conducted theoretical analysis and built heterogeneity seepagecorrection function paradigm. On account of statistical approaches and monitoring datafrom the tracer concentration, the research ascertained correction function in differentnon-uniform seepage cases.4. Coupling the function to the analysis of hydrodynamic dispersion model, it wasapplied into distinct practical experiments and predicted the changes of concentration. Bycomparing concentration graph and contour map, it is verified that coupling function isconsistent with the predications and consequences; hence, it stated that hydrodynamicdispersion model can be more practical when taking the characteristic of non-uniform inseepage and can be applied to predict the spatial-temporal migrations of solute in differentmoments.5. It is predicted that non-uniform diosmose exists in homogeneous medium whilethis phenomenon can be founded on its rhythms through quantities of experiments andnumerical calculations. By constructing correction function, ideal conditions forconvection-dispersive equation can be corrected, therefore predicted the non-uniformdiosmose during the penetration process in a right direction. It is considered as a positiveeffect for porous medium laboratory experiments.