Research about the control of geological structure on karst groundwater system in Zhangfang, Beijing

Carbonate formations are intensively distributed throughout Zhangfang, Fangshan, in the West Mountain area of Beijing. Karst groundwater exits among the geological fracture network which is characterized by the different arrangements and levels in different types of fracture networks and structures. The influence of the tectonic environment on the dynamic change rule and the enrichment regulation of karst groundwater system is significant for the exploitation and protection of karst groundwater resources.From the control function of fault and fracture point of view, based on the developmental and distribution pattern of multi-episodic tectonism, this study analyzed fractures in the three-fold structural units characterized by NE-NW and NS trends and discussed the influence of multi-episodic tectonism on groundwater flow, the spring system and rich water zones.The results showed that the geological fracture underwent two episodes of tectonism, thrusting nappe in the Jurassic and extension in the Cretaceous. The overprint of the processes of the two tectonic episodes resulted in a number of faults with high hydraulic conductivity, which serve as conduits. The superior joint groups are in the NE and NW directions, with conjugated characteristics. The high-angle or vertical dips directly benefit infiltration. The fractures in the intersection areas have formed groundwater runoff channels and storage space, controlling water-rich zones such as Baidai, Ganchi-Changgou and Gaozhuang-Shiwo. Magmatic rock and the aquiclude also contribute to the rich water zones and the location of springs, all of which have important significance for water supply.