Numerical Simulation Of Groundwater Flow By The Land Creation In Yan’an New District

To solve the problem of the growing scarcity of land in Yan’an, the government is going to expand a new district by the urban land creation, which will have an impact on the groundwater flow field and the local engineering geological environment such as soil salinization and loess collapsibility, etc. The research on spatial distribution and evolution mechanism of the disrupted groundwater field is of vital significance to both the engineering and the management of groundwater resource by three-dimensional numerical simulation. And it will also provide theoretical basis for preventing the geological disaster during urban land creation in other cities, which locates in the loess hilly-gully region.Based on analyzing the geology and hydrogeological conditions of the loess hilly-gully area of research area, the model of groundwater flow after land creation has been established by the three-dimensional finite element software Feflow coupled with ArcGIS. In the model, there are three engineering design schemes:scheme A means the model do not set hardening measures and drainage, scheme B means the model sets hardening measures and no drainage and scheme C means the model sets hardening measures and drainage. After calibrating the model, these three schemes in short-term and long-term were simulated to predict the dynamic regime of groundwater level, the depth and the drained effect of blind drainage. The study shows that the new landform after land creation plays a key role on the variation of groundwater level, which is supplement by the blind drainage in the landfill. The hardening measures, which makes the surface water hard to infiltrate to the aquifer, and the blind drainage in the landfill, which significantly improves the hydraulic conductivity of the artificial aquifer, make the groundwater level decreased about 20m. According to the hydraulic gradient changing difference value and the increasing ratios of water level between upstream and downstream in main valley and secondary valleys over the years, the secondary blind drainages are more efficient than the main blind drainage in water drainaging. While, the main blind drainage will be predicted to act the main function for water drainage in future on the result that the hydraulic gradient of the main blind drainage is larger than three secondary blind drainages’ in the end of 50-year simulation period.