Glide block or out-runner block impact on suspended submarine pipeline

Chi, Ken Fai (2012) Glide block or out-runner block impact on suspended submarine pipeline. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (5MB)

Abstract

Due to the high demand of oil and gas, offshore exploration and development are forced to explore and/or develop near areas of potential slope failure. A glide block or out-runner block is the product of a slope failure and can cause great damage on offshore structures, such as a submarine pipeline, since it can travel a long distance from its origin and carries the soil properties of the parent slide. -- To better understand the drag force generated from a glide block or out-runner block on to a suspended submarine pipeline, 11 physical tests were conducted to quantify it and are presented in this thesis. The tests were conducted in a geotechnical centrifuge located at C-CORE under submerged conditions with a centrifugal force of 30 times the Earth's gravity (i.e., N = 30) and simulated impact situations under steady state conditions and uniform velocities. The soil blocks (approximately 4.5 m high in prototype terms) were made of kaolin clay with undrained shear strengths ranged from 4 to 8 kPa. The model pipes were 6.35 and 9.52 mm in diameter, which corresponds to 0.19 and 0.29 m in prototype. The impact velocities ranged from 0.04 to 1.3 rn/s. The pipe centerline was at mid-height of the block. The shear strain rates, defined as the ratio of impact velocity to pipe diameter, in the centrifuge model are N times higher than that in the prototype, and it ranged from 4 to 137 reciprocal seconds. Hence, the test results are applicable to a wide range of field situations. A geotechnical approach was adapted, based on the results of the centrifuge tests, and a method is presented for estimating drag force for soil block impacting on submarine pipeline.

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