Centrifuge modeling of axial pipe-soil interaction of deep-water pipelines

This article describes equipment primarily developed for modeling axial pipe-soil interaction of offshore pipelines in a beam centrifuge. The equipment can displace the pipe axially and simulate vertical forces or oscillations acting on the pipe while the pipe is instrumented to measure the contact stresses, pore pressure, and sliding resistance. Axial motion is actuated by a servomotor actuator coupled to a chain-drive system that moves the pipe in the axial direction relative to the soil bed. A closed-loop servo-driven vertical actuator simulates the vertical forces or oscillations acting on the pipe. The centrifuge model tests were conducted under 10-g model gravity. The pipe penetration response, axial pipe-soil resistance, and pore pressure behavior beneath the pipe were investigated. A higher axial pipe-soil resistance was measured for axial shearing of the pipe that was relatively slow compared to rapid axial hearing. For rapid pipe shearing, high excess pore pressure was generated at the pipe invert compared to relatively low pore water pressure for slower movement of the pipe. The results show that the developed equipment is capable of producing highly consistent results over the range of drained and undrained response, which also agree well with recently reported finite element studies and shear box tests conducted to explore long-term axial friction. This makes the equipment potentially useful for generating high-quality data under controlled conditions in the centrifuge for mechanistic and validation studies.