Prediction of Jack-up Rig Footing Penetration

Endley, Shailendra N.; Thompson, Peter; Baglioni, Vincent P.

doi:10.4043/4144-ms

Cited by 20 publications

(4 citation statements)

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“…One example, where understanding of the change in bearing capacity at different embedment is required, is the offshore application of spudcan foundations. These large footings of mobile drilling platforms regularly penetrate and bury into the seabed to depths of three diameters (Endley et al 1981;Menzies and Roper 2008;Menzies and Lopez 2011).…”

Section: Introductionmentioning

confidence: 99%

Failure Mechanism and Bearing Capacity of Footings Buried at Various Depths in Spatially Random Soil

Tian

Cassidy

2015

J. Geotech. Geoenviron. Eng.

128

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The objective of this paper is to demonstrate how the spatial variability of random soil affects the failure mechanism and the ultimate bearing capacity of foundations buried at various depths. A non-linear finite element analysis combined with random field theory is employed to explore the vertical capacity of foundations embedded at different depths in random soil. Different possibilities of shear failures resulting from spatial patterns of soil are demonstrated and used to explain the significant discrepancy between the bearing capacity of the random soil and that of uniform soil. The effect of the spatial pattern of the soil on the development of shear planes is also investigated, with the coefficients of variation for the bearing capacity demonstrated to be closely related to the shear plane length. Results of the statistical variation in the bearing capacity are provided for different embedment depth and these are also reported as the failure probability of the footing against using the established uniform soil bearing capacity. Safety factors are proposed for foundations at different levels of failure probability. This study provides a thorough understanding of the failure mechanisms of footings in random soil, especially where structures can penetrate deeply into soil.

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Section: Introductionmentioning

confidence: 99%

Failure Mechanism and Bearing Capacity of Footings Buried at Various Depths in Spatially Random Soil

Tian

Cassidy

2015

J. Geotech. Geoenviron. Eng.

128

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“…In most cases all soil within the plan area of the spudcan down to the base level is conveniently removed or replaced by a surcharge of zero strength backfilled soil above the spudcan (Endley et al, 1981;SNAME, 2002). This contrasts with onshore practice where a footing is placed at the base of a preexcavated hole or trench.…”

Section: Sname Suggested Design Approach and Recent Workmentioning

confidence: 99%

New Mechanism-Based Design Approach for Spudcan Foundations on Stiff-Over-Soft Clay

Hossain¹,

Randolph²

2009

Proceedings of Offshore Technology Conference

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The paper reports an improved mechanism-based design approach for assessing spudcan penetration response on stiff-oversoft clay, where potential for punch-through exists. The method has evolved through a combination of centrifuge modeling and large deformation finite element (LDFE) analysis. The model tests included half-spudcan tests against a transparent window, allowing visualization of the soil flow, and full-spudcan tests to measure the penetration resistance. The LDFE analyses simulated continuous penetration from the surface, providing complete profiles of penetration resistance and revealing the evolving soil flow patterns. The analyses were undertaken with and without taking strain softening and rate dependency into account. The LDFE results were first validated against centrifuge observations and then extended for a range of layer geometries and soil strength profiles encompassing almost all cases of practical interest. The design method currently recommended in the SNAME guidelines was found to underestimate the maximum penetration resistance significantly in most cases and to exaggerate the post-peak reduction in resistance. A new design approach based on the study is presented in both graphical and equation form to facilitate use for practical design problems, and is applied to a case study from the field. Comparison between recorded field data, predictions from the new design method and corresponding results from LDFE analyses show that the design method provides accurate estimate of the depth at which punch-through occurred and its severity, and also a close approximation to the full load-penetration response.

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“…the Gulf of Mexico and West Africa), the fine-grained sediments are either normally consolidated or lightly overconsolidated (Gemenhardt and Focht 1970;Endley et al 1981;Puech et al 2005) and the undrained strength profile, s u can be represented as: where s u-m is the mudline strength, k su is the strength gradient and z m is the depth below the mudline.…”

Section: Introductionmentioning

confidence: 99%

Laboratory development of a vertically oriented penetrometer for shallow seabed characterization

et al. 2016

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Current site investigation practice for offshore pipeline design relies on soil parameters gathered from boreholes or in situ test soundings to depths of 1–2 m below the mudline. At these depths, the fine-grained seabed is very soft and possesses low undrained strength, which can be difficult to measure. This paper describes a centrifuge test programme undertaken to evaluate the feasibility and performance of a novel penetrometer designed to assess the shallow strength of soft seabed over continuous horizontal profiles. This device is termed the vertically oriented penetrometer (VOP). Tests were performed on a normally consolidated kaolin sample, with the VOP translated horizontally at velocities ranging from 1 to 30 mm/s, after embedding the VOP at 30 and 45 mm depths. All tests involved many cycles of VOP forward and backward movement to assess its potential to derive the ratio of intact to fully remoulded strength. Strength determination is achieved by dragging the VOP at a specified embedment depth along the soil surface, and deriving the soil strength from the measured resistance as if the VOP were a laterally loaded pile. The VOP is shown to yield comparable strength measurements to that of a T-bar penetrometer. The VOP is a potentially valuable addition to the range of tools used to characterize soil strength, both in small-scale centrifuge models and, following practical development, potentially also in the field.

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Prediction of Jack-up Rig Footing Penetration

Cited by 20 publications

References 0 publications

Failure Mechanism and Bearing Capacity of Footings Buried at Various Depths in Spatially Random Soil

Failure Mechanism and Bearing Capacity of Footings Buried at Various Depths in Spatially Random Soil

New Mechanism-Based Design Approach for Spudcan Foundations on Stiff-Over-Soft Clay

Laboratory development of a vertically oriented penetrometer for shallow seabed characterization

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