Kinematics of jointed pipes and design estimates of joint rotation under differential ground movements

Abstract

Centrifuge testing of reduced-scale models has been used to examine the kinematics of jointed pipelines crossing normal ground faults. The model pipeline was fabricated at 1/30th scale using segments of a semicircular cross section cut from an aluminum rod. Threaded rods were used to connect those segments and model a variety of joints having longitudinal bending stiffnesses from 3% to 47% of the bending stiffness of the pipe segments. The semicircular segments were placed against a glass sidewall of the test box and buried in sand. During testing under 30g, differential ground movements of up to 70% of the pipe diameter were imposed, and the pipe movements were monitored using particle image velocimetry. It is shown that maximum rotations occur at the joints when the shear zone generated by the ground fault passes across the joint rather than the pipe segment, and that joint stiffness has little impact on the pipe kinematics. A simplified kinematic model is introduced that permits straightforward, safe estimates of maximum joint rotation.