Validation of boundary PIV measurements of soil–pipe interaction

Abstract

It is a well-established argument that side-wall interface friction can influence the behaviour of soil located at the boundary of physical model test chambers. This effect has a potentially significant influence on measurement techniques such as particle image velocimetry that often rely on images captured at vertical transparent boundaries. However, it is hypothesised that under kinematically controlled boundary conditions, particle image velocimetry can yield not only qualitative but highly accurate quantitative measurements of deformation. In this paper, this hypothesis is tested for the specific soil–structure interaction problem of pipelines being subject to vertical faulting. In the middle of the model, a circular model pipeline was heavily instrumented with 32 pairs of strain gauges. At the same elevation but at the window of the test chamber, an identical model pipeline was split in half axially along its centreline to give a semi-circular cross-section, and placed against the visible window. Three digital cameras were used to record deformations of the pipe and the surrounding soil during the test. After image processing and filtering, measurements of peak curvature obtained from digital image analysis on the half pipeline section are shown to be within 5% of the results obtained from strain gauges.