Pipeline-soil interaction behaviour: acoustic emission and energy dissipation

Acoustic emission (AE) offers the potential to monitor and interpret soil-pipe interaction behaviour by sensing particle-scale interactions. However, application of AE is limited by gaps in understanding related to how particle-scale interactions influence AE activity. Discrete Element Method (DEM) simulations of buried pipe uplift with energy tracking were performed and compared with experimental mechanical, displacement and AE measurements, to ensure realistic behaviour was captured by the modelling approach. A parametric investigation was then performed to evaluate the influence of pipe displacement direction and pipe diameter on plastic energy dissipation, and hence AE. Trends of dissipated plastic energy and measured AE with stress level (via burial depth) and pipe velocity were analogous. Relationships were quantified (R2 ranging from 0.74 to 0.98) between AE, dissipated plastic energy, and pipe velocity. Measured AE and dissipated plastic energy were linked with a general expression, comprising increments of friction (sliding and rolling), damping, and damage energies.
Sliding friction energy accounted for >80% of the total dissipated energy on average during buried pipe deformation. Exemplar relationships were established between dissipated energy, pipe movement direction, embedment ratio, and mobilised soil volume (R2 values ranging from 0.92 to 0.97). A conceptual framework for interpreting buried pipe behaviour using AE monitoring was presented.