Groundwater Simulation Of The Hydrogeological Impact Exert By The Excavation And Embankment In The Loess Hilly-gully Region

Excavation and embankment in the loess hilly-gully region is essential for land formation, which is in urgently need caused by the rapid expansion of Yanan city. After the implement of EAE, surface runoff and exposed springs will be buried in the valley where these runoff and springs flowing. And the spatial structure and hydraulic conductivity of the natural aquifer will be also changed, as well as the the recharge and discharge condition. In addition, this hydrogeological impact will be intensified by the hardening measures to the site and the drainage in the landfill. The changes in the hydro geological conditions would not only cause the fluctuations of groundwater level inevitably, but also affect the groundwater system, significantly. Besides this problem, engineering damage, such as failure of site by lost strength of loess will be resulted. In a word, the geological engineering measures, such as EAE, hardening measures to the site and drainage in the landfill, can have profound effect to the natural ground water system. As a result, exploring how to responds to the implement of EAE, when the ground water system is remake by EAE, is not only the requirement of engineering, but also the need for management of water resource. And it will make contributions to the understanding how to evolves of underground water system when it disturbed by engineering carried out in the loess hilly gully region.In order to identify the effect to the natural aquifer, the present paper have carried out a numerical study with the Feflow software coupled by GIS, based on the field data collection, theoretical analysis and etc. According to the hydrological impact induced by the geological engineering, such as the remake effect to the hydrological condition by the implement of EAE, as well as hardening measures and drainage, a series of modeling scheme is designed in the simulation. After running the numerical model according to different modeling design scheme, the Dynamic Regime of groundwater level, the depth, as well as the decline is predicted. Through analysising of the spetial temporal variations in groundwater level, the mechism of groundwater level evolvation is investigated. The present study show that, on one hand, the remake effect induced by EAE plays a key role on the groundwater flow, where the drainage measure in the landfill make a assistance. In addition, harding measure to the site can increasing the hydraulic gradient about30%-50%. And the auxiliary influence to the response of the groundwater level characterized by acceleration of decline in the water table in the upstream, when by acceleration the rising of water level in the down stream. As aresult, the upstream of new terrain became relatively high and flat Loess Plateau take shapes, and the groundwater level will rise slowly, and finally come to stable with groundwater level at1085-1095m.