Mining operations generate massive quantities of waste during the extraction of valuable ore. In Sweden, annually 126 million tons of waste is generated from mining and quarrying, 70% of mine waste contains sulfide minerals, which has the potential to generate acid rock drainage (ARD) when it contacts with atmospheric oxygen and humidity. To avoid the formation of ARD, Soil cover, i.e., multi-layer soil cover system in Sweden is typically used to limit the ingress of water and oxygen into the underlying mine waste.

In boreal regions, seasonal variations such as prolonged freezing periods, snow accumulation, and rapid snowmelt events create highly transient hydrological conditions within soil cover systems. These processes significantly influence water balance components, including infiltration, storage, and net percolation, which are critical for evaluating sealing layer performance. In addition, prolonged dry periods can reduce soil saturation, potentially increase oxygen diffusion and compromise the effectiveness of the cover system. Understanding these coupled processes is therefore essential for the design of reliable and climate-resilient mine soil covers.

The main objective of this study is to investigate the hydraulic performance of mine cover sealing layers through an integrated approach combining field trials, laboratory column testing, and numerical modelling using SEEP/W. The hypothesis is that combining testing methods would allow for an assessment at the early stage of design process, which makes it possible to test alternative and innovative cover design in a time and cost-efficient way.

The research field trails are centered at the Garpenberg mine in Sweden, where different designs of sealing layer of cover systems have been constructed and instrumented to monitor key parameters such as volumetric water content, matric suction, and temperature. These field data provide a basis for developing detailed water balance assessments and for evaluating the performance of different sealing layer configurations.

Laboratory column experiments were conducted to replicate the multilayer cover system under controlled conditions, allowing for detailed analysis of water flow and retention behavior. These experiments enable the assessment of the influence of material properties, including compaction and bentonite content, on sealing layer performance. Numerical modelling was used to simulate the hydraulic behavior of the cover systems, including extreme weather conditions such as snowmelt and prolonged dry periods. The models were calibrated and validated using both laboratory and field data to ensure reliability.

The results show that the integration of laboratory testing and numerical modelling provides an effective framework for evaluating mine cover performance and predicting water balance dynamics. The findings highlight the critical role of sealing layer design in controlling net percolation and maintaining sufficient saturation to limit oxygen diffusion. Furthermore, the study shows that climatic variability has a significant impact on cover system behavior, emphasizing the need for climate-specific design approaches.

This research contributes to the development of improved methodologies for the design and assessment of mine soil cover systems. The integrated approach presented reduces reliance on costly field trials and supports the development of more sustainable and resilient mine closure strategies.