Soil restraints on buried pipelines subjected to reverse-fault displacement

Abstract

The interaction between a buried pipeline and surrounding soil during large ground displacements is typically simulated using numerical nonlinear soil-restraint springs aligned with the longitudinal axis of the pipeline and in the two directions orthogonal to it. There are only very limited experimental data available to characterize the soil springs for simulating pipelines crossing reverse faults where large oblique soil displacements relative to the pipe could occur. Full-scale model testing was undertaken to evaluate this complex soil–pipe interaction problem. The tests simulated the performance of ∼400 mm diameter (nominal pipe size, NPS 16) pipe specimens buried in moist sand and crushed limestone trench backfill. The peak normalized oblique soil restraint (N θ ) values for oblique pipe movement angles (θ), when θ = 0° (horizontal movement) and θ = 90° (vertical movement), estimated based on state-of-practice approaches, were in agreement with those from full-scale testing. The value of N θ was found to depend significantly on the peak friction angle of soil ([Formula: see text]) when θ was closer to 0°, whereas N θ was less sensitive to [Formula: see text] when θ was beyond about 35°. The theoretical values of N θ based on limit-equilibrium approaches compared well with the experimental findings.