The 24th IAHR-APD Congress (24th IAHR-APD Congress)

176 / 2024-02-26 17:41:03

The Characteristics and Storage Law of Weak-Middle Mineralized Groundwater in Red Beds in Central Area of Sichuan Basin

central area of Sichuan Basin；red bed；shallow weak-middle mineralized groundwater；storage law；genetic mechanism

The shallow weathered rock mass of the red bed in central area of Sichuan Basin hosts weak-middle mineralized groundwater.Studying its spatial distribution, hydrochemical characteristics and storage law is of great significance for solving seasonal water shortage and evaluate its impact on engineering construction.Based on the results of 35 borehole fluid resistivity tests and 95 groundwater samples hydrochemical analysis carried out by a water diversion project in this area, the relationship between mineralized degree and apparent resistivity of underground water, and the relationship between storage law and water-bearing rock groups, rock weathering, rock chemical composition, recharge, runoff and discharge were studied, and the genetic mechanism was analyzed. The study shows that the shallow weak-middle mineralized groundwater mainly stored in the pores and fissures of the shallow weathered rock mass of mudstone and sand-mudstone interbeds. The apparent resistivity is less than 8Ω·m for middle-mineralized water（mineralization degree is 3～10g/L）, and less than 16Ω·m for weak mineralized water（mineralization degree is 1～3g/L）. The hydrochemical types are mainly HCO₃+SO₄-Ca and SO₄-Na for weak-mineralized water, and SO₄-Na and Cl+SO₄-Na for middle mineralized water, which are medium-strong corrosive to concrete. The ionic components are mainly derived from the plaster salt leaching and dissolution of rock containing soluble and easily soluble components such as gypsum and calcareous nodules. Under the control of micro-geomorphological conditions, the vertical zoning characteristics of groundwater are significant, which can be divided into active alternating zone fresh water ( buried depth less than 15 m ) and slow alternating zones of weak-mineralized water (buried depth 15-25m), and stagnant alternating zones of middle mineralized water (buried depth 25-40m).The research results can guide the development and utilization of groundwater resources in this red beds area and the engineering layout and treatment related to weak-middle mineralized groundwater.