Three-Dimensional Finite Element Analyses for Buried Concrete Pipes in the Imperfect Trench Installations

The objective of this study was to validate the superiority of the induced (or imperfect) trench installations (ITI) with proposed soft material zone for buried concrete pipes using 3D FE analyses and nonlinear soil models. The ITI method is used to reduce earth pressure on deeply buried conduits. There, however, have been limited research results published regarding primarily qualitative aspects of earth load reduction for imperfect trench conditions. Kang et al. proposed the optimum geometry of the soft material zone using 2D finite element (FE) models. Their studies, however, had several limitations: 1) plane strain approach only; and 2) no available field test data for the modeling validation at that point. The developed 3D FE models have been validated and calibrated using experimental field studies from Valsangkar et al., and showed good agreements with the experimental studies. The limitations of the previous 2D FE models by Kang et al. have successfully been overcome by this study. The findings and recommendations presented in this report, therefore, would provide the detailed guidelines for envisioned field studies and ITI design. It is hoped that an innovative understanding of the soil-structure interaction for deeply buried conduits and other findings presented in this study will find their way into improved specifications in the near future. As the economic impact appears to be huge, immediate implementation of these findings by designers and contractors is particularly urgent for conduits buried under several hundred feet of fill