Activities to enhance students’ understanding of pore water pressure, seepage and total head

When students start an undergraduate engineering course, many have a limited comprehension of water pressure, and find that understanding first hydrostatics and later the concepts of total head and seepage is extremely challenging. Yet this topic is very important in engineering practice, and misconceptions about the water regime often contribute to major failures in excavations and tunnels. This paper describes attempts at the University of Bristol to develop undergraduate civil engineering students’ understanding of pore water pressure through classroom exercises and in the laboratory. In class students are encouraged to explore problems of one-dimensional seepage. Later, working in small groups, students observe flow through a dam built from sand in a seepage tank and compare their empirical flow-net with predictions using a finite element seepage analysis run for them in the laboratory. They measure the permeability of the same sand using a per-meameter, which also demonstrates the link between seepage and non-hydrostatic pressure. Using this perme-ability they compare the predicted and measured discharge from the dam, before they observe failure of the downstream slope of the dam induced when the exit from the underlying drainage blanket is blocked. These activities develop their understanding of pore water pressure, seepage and total head so that many have confi-dence in their ability to predict and interpret groundwater observations by the time they graduate.