Possible Approaches of Numerical Modelling of Seepage Anomalies and Cut-Off Wall Solutions for Earthfill Dams

Abstract Seepage is a frequent cause of dam safety problems and often leads to internal erosion or suffusion. A case study of a small earthfill dam in Slovakia, i.e., the Lozorno Dam, has exhibited anomalies in the development of seepage since its commissioning. This has been manifested by increased water levels in its observation boreholes and the occurrence of fine sand deposits in its relief wells. The objective of this study was to analyze the causes of these anomalies and propose effective remedial measures. The field monitoring data, including the groundwater levels and seepage flows, were evaluated and complemented by numerical modeling. The models were calibrated against long-term measurements in key observation profiles and subsequently applied to assess different remediation scenarios. The results demonstrated that local permeable sandy soils on the left valley slope are the primary source of the anomalous seepage. Parametric studies showed that the construction of a cut-off wall (COW) significantly reduces groundwater levels, seepage, and hydraulic gradients below critical limits. The findings provide practical recommendations for the remediation of earthfill dams in similar geological settings and highlight the importance of integrating monitoring and modeling in dam safety management.