Uplift resistance of buried submarine pipelines: comparison between centrifuge modelling and full-scale tests

Abstract

A buried pipeline can buckle upwards if there is not enough resistance to movement. Both the uplift resistance (the maximum force per unit length) and the mobilisaion distance (the distance the pipeline has move before the maximum force is reached) are important in design. Tests on pipes in several soils were carried out at 1 g at full scale and in a centrifuge at 10 g and 1/10 scale. A comparison shows that the measured uplift resistances are consistent with the conventional understanding of centrifuge tests, but that the measured mobilisation distances are not consistent with that understanding. Unscaled mobilisation distance in the centrifuge is roughly the same as at full scale. Mobilisation distance does not scale with particle size. This discrepancy is related to the formation of shear zones, and to theory and observations in other areas of the mechanics of brittle materials, among them ice, concrete and heavily overconsolidated clays. An idealised analytical model displays the same behaviour.

Mobilization Distance for Upheaval Buckling of Shallowly Buried Pipelines

“…Experimental data from previous research (Trautmann et al 1985;Schaminée et al 1990;Baumgard 2000;Palmer et al 2003;Wang et al 2010a) supports the hypothesis that the value of f p remains reasonably constant for a particular pipe geometry and backfill condition. This assumption breaks down, however, when a deep flow-around type mechanism begins to occur, typically beyond H=D ¼ 6.…”

“…One underlying reason for this is the scaling law discrepancy for mobilization distance between small-scale centrifuge and full-scale test data. Previous research (Palmer et al 2003) confirmed that, while centrifuge modeling offers reasonably accurate estimates for R peak , the standard distance scaling law could not be used to derive δ f because of localized shear zone formation. As the thickness of the shear zone is a multiple of the particle diameter, the pipeline movement required to mobilize full uplift resistance is a function of the ratio of the diameters of the pipe and the soil particles.…”

“…It is worth pointing out that such insensitivity is not inconsistent with the known problem that δ f does not scale conventionally in centrifuge tests. Palmer et al (2003) suggested that this could be tentatively explained as a result of localized shear stress being a function of relative absolute displacement:…”

Investigation of the effect of different gravity conditions on penetration mechanisms by the Distinct Element Method

“…Klein and White (1990) conducted experiments of granular flow in a rotating drum to investigate the effect of gravity on angles of repose, followed by the work of Brucks et al (2007). Tests on pipes in several soils were also carried out at 1g at full scale and in a centrifuge at 10g and 1/10 scale (Palmer et al, 2003). Little study has been carried out on the effect of gravity on the penetration into lunar soil simulants by centrifuge model tests.…”

Experimental and numerical simulation of buried pipelines subjected to large permanent ground displacements

“…Since a very important issue in the design of pipelines is the potential upheaval buckling, much effort was also placed on exploring the upward soil restraint (i.e upward p-y springs). Drained conditions have been assumed in the works , , , , while saturated soils under drained and undrained conditions were studied by White et al (2001), Palmer et al (2003), Schupp et al (2006), , Williams et al (2013). Experimental data on the (downward) bearing capacity of buried pipelines may be found on the work of Nagaoka (2007).…”