Why is it so difficult to reliably measure the pore pressure at the base of a fast landslide in a laboratory flume test?

Laboratory landslide flume tests provide valuable insights into the mechanics of multi-phase granular flows within highly controlled settings. Past studies have revealed the complex fluid-particle interactions associated with saturated granular flows result in greater mobility than their dry counterparts, being notably faster, further reaching, and experiencing enhanced spreading. The ability to reliably measure the pore pressures at the base of these flows in the laboratory is critical for developing, evaluating, and validating constitutive relationships linking the effects of pore pressure to the mechanisms causing increased mobility. Unfortunately, experience has shown that two identical sensors installed in the base of a landslide flume can yield wildly different responses to the same multi-phase landslide. In this session, we explore an answer to the question “Why is it so difficult to reliably measure the pore pressure at the base of a fast landslide in a laboratory flume test?” using evidence accumulated from ten years of flume testing using the Queen’s University Landslide Flume. In particular, we explore the hypothesis that surface roughness around pore pressure sensor filter elements can influence sensor readings. A unique experimental strategy of simplifying the flow into a single fluid phase is used to validate sensor readings, prior to application in multi-phase flows. Dam-break releases of 600 kg of water at the top of the inclined flume slope are used as a parametric study to provide evidence to support the hypothesis that surface roughness significantly impacts the pore pressure recorded in high velocity flows. These results are then contrasted to observations of releases of multi-phase flows to derive best practices for the reliable measurement of pore pressure in landslide flume tests.