Centrifuge Model Test on Performance of Thermosyphon Cooled Sandbags Supporting Warm Oil Pipeline Buried in Thawing Permafrost

Abstract

The performance of thermosyphon cooled sandbags supporting the warm pipeline in permafrost was simulated in a centrifuge model test. Two pipes of an unsupported and a supported section were evaluated over a period simulating 20 years of operation with seasonal oil and air temperature cycles along the China-Russia Crude Oil Pipeline (CRCOP). The results showed that pipe settlement of the supported pipe was 45% of the settlement of the unsupported pipe. The final thaw bulbs extended about 3.6 and 1.6 times the pipe diameter below the unsupported and supported initial pipe elevations, respectively. The sandbag supports remained frozen throughout the test period due to cooling effect of thermosyphons. The maximum bending stress induced over the span length from bearing of the full cover is equivalent to 40% specified minimum yield strength. Potential buckling of the pipe should be considered as the ground thaws. Suggestions for design considerations for the field conditions along the CRCOP are made based on the model test observations.