ANALYSIS OF AUTOMATED PIEZOMETRIC MONITORING DATA FOR THE CONTAINMENT DAMS OF A PHOSPHOGYPSUM TAILINGS STORAGE FACILITY DURING THEIR RAISING

Abstract

The purpose of the research is to establish, from automated multipoint monitoring of hydrostatic pressure and groundwater temperature, the quantitative structure and dynamics of the vertical seepage regime of the containment dams of a phosphogypsum tailings storage facility and to assess the actual reserve of their seepage strength during staged raising. Materials and methods. Forty-two and fifty-three readings from wells GG-1 and GG-2 covering November 2023 – September 2025 were processed; the data came from multipoint systems of four piezoresistive sensors with built-in thermistors and SAP-1M/GSM loggers. The work included statistical processing of the series, calculation of vertical hydraulic gradients for six measuring intervals, estimation of the relative permeability of the layers from the continuity condition of the vertical flow, and comparison with the design safety criteria K1 and Kpr. Results. A steady downward flow was established with a total head difference of 20.62 m (GG-1) and 22.47 m (GG-2); the regime was shown not to be steady. A transient process was recorded in well GG-2: over 39 days the heads in the middle of the mass rose by 7.85 and 7.48 m and dissipated over 65 days, while the response of the foundation did not exceed 0.61 m. In well GG-1 the share of head loss across the silica gel – cemented phosphogypsum interval increased from 26.4 to 52.5%, while the share of the interval containing the peat layer decreased from 51.0 to 21.6%. Thermometry independently confirms the difference between the sites: the foundation groundwater temperature is 7.48°C in GG-1 against 12.56°C in GG-2. The minimum reserve up to criterion K1 is 3.12 m. Conclusions. The estimates make it possible to substantiate the drainage layout in the GG-2 area, the sensor polling schedule during raising and the parameterisation of a layered seepage model.