Demystifying basal pore pressure measurement in landslide flume experiments

Laboratory landslide flume studies have revealed that saturated granular flows experience greater mobility than their dry counterparts, being notably faster, farther reaching, and experiencing enhanced spreading. The ability to reliably measure basal pore water pressures 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 paper we explore the hypothesis that the elevation of pore water 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 sensor 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.