Stagnation Flow Principle’s Comparative Study On Its Hydraulic Simulation, Analytical Method And Numerical Method In Un-confined Unsteady Flow Seepage Process

As an important component of water resource, groundwater plays an important role inpromoting national economic development and maintaining hydro-ecologic system balance. Itis necessary to guide groundwater rational development and utilization by researching thegroundwater seepage law for quantitative evaluation of groundwater. However, in the processof seepage calculation, it is difficult for hydrogeologists to make quantitative evaluationbecause of the complex hydrogelogical conditions and uncertain boundary conditions. Inorder to identify the hydrogeological conditions and boundary conditions of the study area,we have to spend a lot of human, materials and financial resources. At the same time, thecomplexity of the boundary conditions has caused great difficulties for seepage calculation.Studies have been shown that boundary conditions have no direct impact on flow processeswhen Initial seepage field source was mutated and has not reached the borders. Therefore，when the seepage calculation is only for the areas that the new formation of the seepage fieldhas not spread to，to determine the complex boundary conditions will only increase thedifficulties of the hydrogeological work and not get better results.Based on Professor Li Pei-cheng’s “stagnation flow principle”，this paper preliminarilyanalysed the impact of boundary conditions on the seepage process，and set three differentspacings between complete rivers(that was to say，three different schemes were designed):Un-confined unsteady flow seepage process in the area between rivers was simulated byhydraulic integrator, meanwhile, definition on error range and similarity was put forward toanalyse the scope and the seepage process of the various schemes caused by the new seepagefield. The results showed that, when the seepage field had not reached the boundary, thescopes caused by the new seepage field were almost the same, and the basically same changeof groundwater table happened in each time of different schemes to the same location. Whilethe seepage field had reached the boundary, the seepage process changes with the effect ofboundary, groundwater table was largely different to the same area in different schemes.Based on results by hydraulic integrator above, un-confined unsteady seepage model incomplete rivers was established, different boundaries were set, and the groundwater flow movement process in different boundary conditions was analyzed by using analytical methodand numerical simulation method. The results show that：when the seepage field had notreached the boundary, the scopes caused by the new seepage field were completely same, andthe completely same change of groundwater table happened in each time of different schemesto the same location. While the seepage field had reached the boundary, the seepage processchanges with the effect of boundary, and groundwater table was largely different to the samearea in different schemes，which further verified the results of hydraulic integrator above. Inaddition, with engineering example, whether groundwater affected the foundations of buildingor not, based on “stagnation flow principle”, different boundaries for seepage calculation wereassumed. The results show that there is no influence to the B factory foundation in threemonths when river level risen.Through the engineering calculation, it is shown that, theassumption to boundary conditions is feasible for seepage calculation in the practical workwhen the source of seepage field mutated.