Impact of soil erosion voids on reinforced concrete pipe responses to surface loads

This paper discusses the results of controlled, full-scale laboratory experiments on 0.9 m (36 in.) internal diameter reinforced concrete pipes (RC pipes) in the presence of simulated erosion voids. This study introduces a novel, yet practical, experimental method to simulate erosion voids near buried pipes. Using this method, the paper focuses on capturing the circumferential moment changes experienced by a 0.9 m (36 in.) internal diameter RC pipe buried at 0.9 m depth as voids of different sizes (approximate cross-sectional areas of 0.16 m(2) and 0.31 m(2)) develop beside it, which have not been investigated before in such tests. The tests were also repeated after the erosion voids were repaired using a low strength grout (similar to 2 MPa) to characterize it as a potential rehabilitation solution, and the moment changes were recorded. The presence of erosion voids resulted in an overall increase in bending moment with the invert moments being affected the most (e.g., 70% increase in the invert moment between the intact soil result and the small void result and a 26% increase in the invert moment between the intact soil result and the extrapolated large void results). While, grouting the erosion voids resulted in an overall improvement in the pipe responses, there was still a 50% increase in the invert moment between the intact soil result and the grouted small void result and a 22% change between the grouted large void and the intact soil tests. The large void tests showed that soil collapse is the dominant failure mechanism at high loads. Comparing the modified bedding factor values for pipes with different void sizes and void condition (pre- and post-grouting), the intact soil always featured the highest bedding factor, followed by grouted large void (approximately 22% reduction in bedding factor), grouted small void (approximately 36% reduction), and small void before grouting (approximately 39% reduction).