2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference


Title
Full-Scale Laboratory Pullout Testing Of A 60mm Diameter Buried MDPE Pipe


Author(s)
Mr. Auchib Reza, Memorial University of Newfoundland, St. John's, NL, Canada. (Presenter)
Dr. Ashutosh Dhar, Memorial University of Newfoundland
Mr. Abu Hena Muntakim, Memorial University of Newfoundland
Abstract

Buried pipelines are extensively used for transporting oil, gas and water in Canada and worldwide, as pipelines are considered the most convenient and economical means of transporting liquid and gas. The pipelines are often required to cross active landslide areas, which are subjected to additional loads due to ground movements. Assessment of the effects of ground movements on the performance of the pipeline is, therefore, an important consideration for pipeline integrity management. The existing pipe design methods for the assessment of the performance of pipelines crossing active landslide area recommend using the simplified method to calculate maximum pullout force due to axial landslide without proper consideration of soil-pipe interaction. Researchers employed analytical and numerical modelling approaches to explain the soil-pipe interaction during relative ground movements. However, the assumptions used in the analytical and numerical models require validation with experimental evidence. Over the past few decades, many experimental studies were carried out to improve the understanding the behaviour of pipelines subjected to ground movements. However, studies on medium density polyethylene (MDPE) pipes, which are extensively used for the gas distribution system, are very limited. A new full-scale pipe test facility has been developed at Memorial University of Newfoundland to investigate the behaviour of flexible medium-density polyethylene (MDPE) pipes subjected to movements relative to the soil. The facility comprises a 1.5m × 2m × 4m testing chamber with the capacity to axially pulling out pipes buried in sand backfill. A pullout test of a 60 mm diameter MDPE pipe has been performed using the test facility. During the test, the axial movement of the pipe is measured using LVDT and pipe wall strains are measured using uniaxial and biaxial strain gauges. Pressures within the soil are measured using vibrating wire strain gauges and I-Scan tactile pressure mapping systems. The study reveals that the pullout behaviour of the pipe significantly depends on the viscoelastic response of the pipe material. Pipe strains increased almost linearly from the trailing end to the leading end during the pullout test. Surrounding soil offered resistance to a pullout that reduced the axial pipe wall strains. The paper presents the key features of soil-pipe interaction observed during the test.