Comparison Between Hydraulic and Hydro-Mechanical Analyses for Estimating Flow Rate in Rock Masses: Case Study: Upper Gotvand Dam Foundation - Iran

Abstract

Water flow through fractured rock masses is one of the important topics in civil, mining and environmental engineering fields. In order to estimate accurately water flow rate in fractured rock media, it is crucial to take into account the Hydro-Mechanical (HM) coupling processes occurring between the solid body of rock fractures and fluid flow. In this study, differences between HM analysis, considering HM coupling interactions, and hydraulic analysis have been investigated through numerical models as well as in a large scale model of Upper Gotvand dam foundation as a case study. The results show that flow rates obtained from HM analysis are significantly higher than those obtained from hydraulic analysis since in HM analysis the change of water pressure can lead to aperture change. In this regard, two different behaviours can be seen for a fracture: (a) if the water pressure exceeds in a fracture compared to the overburden load, the fracture aperture increases, and such condition can be seen at depth less than 40 meters for the studied case; (b) if the overburden load on the fracture is higher than the water pressure, the fracture aperture decreases as seen at depth greater than 40 m in the studied case. The changes in fracture apertures lead to a flow regime in the fractured rock mass different from the one predicted using hydraulic analysis. The results of the study were applied to design of the Dam foundation and abutments. Comparison Between Hydraulic and Hydro-Mechanical Analyses for Estimating Flow Rate in Rock Masses: Case Study: Upper Gotvand Dam Foundation - Iran.