Kuazizhuang fortune telling

Hydrogeological characteristics of water-bearing strata in karst fractures

I. Development and distribution characteristics of karst fractures

There are many exposed strata in this area, and the development degree of karst fractures directly controls its water abundance. The development degree of karst fractures is directly restricted by factors such as stratum lithology, geological structure and burial conditions. Middle Ordovician limestone is easy to form large karst caves, fractures and collapse columns because of its thick strata, high calcium carbonate content and rich groundwater. In addition, in areas with complex geological structures, such as the turning point of Kaiping syncline, the north-south turning point of Chengzizhuang anticline, the edge of Jinggezhuang syncline, the northern end of Chezhoushan syncline, Douhe fault and the influence zone of Xiaoshuipo fault, karst is very developed. The thickness of Quaternary in the northeast of Tangshan City is small, pore water is closely related to karst water, and water alternates strongly, which is easy to form dissolution cracks and caves, and groundwater is also rich. However, the deep limestone buried by the overlying water-resisting layer can not be replenished by Quaternary pore water, with poor hydrodynamic conditions, poor karst development and little water supply value.

(1) Distribution characteristics, development and water abundance of Ordovician karst fractures.

The exposed Ordovician limestone is mainly distributed in the north of Feng Run County, the northwest of Luanxian County and the northeast of Tangshan City (the north wing of Kaiping syncline), with a small exposed area. The Ordovician limestone of caprock is mainly distributed in the northwest wing of Kaiping syncline from Houtun to Kuzizhuang. Weifengshan, Tatuo, Qingtuoying and Lihaozizhuang in the southeast wing of Kaiping syncline; Axle mountain syncline, Hancheng, Sishenzhuang area; Jinggezhuang syncline area. Its cover thickness is different, its distribution area is different and its development degree is quite different. Buried Ordovician limestone is buried in Carboniferous-Permian strata, distributed in the core of syncline, and karst is not developed, but ancient karst is developed in the end and wing of syncline and the shallow buried area of Ordovician limestone near the fault.

Ordovician limestone karst fractures are developed, with good connectivity and good water conductivity. The water level in the same structural unit tends to be consistent, and the hydraulic gradient is about110000, which has the characteristics of large pumping influence range, fast water level transmission speed, equal amplitude, synchronization and area change. However, due to the division of formation lithology or water-blocking structures, the hydraulic connection between structures is quite weak.

(2) The development and distribution characteristics of karst fractures in Cambrian, Qingbaikou, Jixian and Great Wall systems.

Cambrian system, Qingbaikou system, Jixian system and Great Wall system are exposed in the northern mountainous area. The lithology is mainly oolitic limestone, leopard limestone and flint nodule dolomite, with developed karst fractures. The axis of Beiziyuan anticline, Kaiping syncline and Chezhoushan syncline are covered with limestone, and the thickness of the covering layer is tens of meters in the north and 600 meters in the south. The thickness of the west side of the Lizhuang fault in Daba Mountain is more than 700 meters. Generally, karst fractures are not developed, but only in the area with the Quaternary thickness less than 100 meters.

Secondly, the water-bearing property of water-bearing strata in karst fractures.

The water abundance of water-bearing rock groups in karst fractures is basically consistent with the development degree of karst fractures.

Dolomite and dolomitic limestone are mainly exposed in Qingbaikou period, Jixian period and Great Wall period, and groundwater is directly replenished by atmospheric precipitation. Shangshui Road area in Feng Run County has a spring flow of about 5800 m3/d, which is a strong water-rich area. Luanxian bedrock exposed area, with spring flow of 1706.4 m3/d, is a medium water-rich area; Other exposed bedrock areas in mountainous areas are rich and poor water areas.

Covered karst fissure water-bearing rock formations and buried karst fissure water-bearing rock formations are widely developed in the sloping plain in front of the mountain. The buried depth of the roof of the covered karst fissure water-bearing rock formations is mostly less than 300m, which is rich in water due to direct recharge by Quaternary infiltration and has water supply significance. For example, in Zhaogezhuang and Majiazhuang areas of Kaiping Basin, the buried depth of Ordovician limestone aquifer is 160 ~ 230 m, and karst fractures are developed, and the single-hole water yield can reach more than10000 m3/d. Strong water-rich areas are distributed in the eastern mining area of Tangshan City, and the single-well water yield is 21.65 ~/kloc-. In other areas, the water yield of a single well varies greatly due to different buried depths and different strata in direct contact. Only J 10 and C 1 1 have a single well water yield of 2257m3/d in the north of LaoZhuangzi Town in Feng Run County and Wangzhuangzi in Fengnan City, and the single well water yield of other carbonate rocks is 3 140m3/d, both of which are relatively large.