Anchor Sharing in Sands: Centrifuge Modelling and Soil Element Testing to Characterise Multi-Directional Loadings

2018 ◽  
Author(s):  
Manuel Herduin ◽  
Christophe Gaudin ◽  
Lars Johanning
Keyword(s):  
Shear Stress ◽  
Renewable Energy ◽  
Simple Shear ◽  
Physical Modelling ◽  
Centrifuge Modelling ◽  
Shear Tests ◽  
Mooring Lines ◽  
Geotechnical Centrifuge ◽  
Capacity Reduction ◽  
Load Conditions

Offshore foundations are typically designed to resist mooring loads coming from a single direction. This paper provides some insights into the geotechnical challenges associated with anchor sharing (i.e. where mooring loads are coming from multiple directions to one anchor) for Offshore Renewable Energy (ORE) applications. Firstly, the multidirectional mooring load conditions on shared anchors are characterised for cases with one, two and three mooring lines connections. Secondly, multi-directional loadings applied on a caisson foundation in a geotechnical centrifuge facility showed large capacity reduction and large displacement of the foundation at large loading angle. Thirdly, multi-directional simple shear tests have showed that volumetric contraction increases as the degree of shear stress reversal increases. Lastly, the results from the soil element tests are brought into discussion with the physical modelling results to identify the foundation’s response to multi-directional loading.

scholarly journals Geotechnical centrifuge modelling of gelifluction processes: validation of a new approach to periglacial slope studies

2000 ◽  
Vol 31 ◽  
pp. 263-268 ◽  
Author(s):  
Charles Harris ◽  
Brice R. Rea ◽  
Michael C. R. Davies
Keyword(s):  
Gravitational Field ◽  
Physical Modelling ◽  
Full Scale ◽  
Laboratory Simulation ◽  
Small Scale ◽  
Centrifuge Modelling ◽  
Soil Movement ◽  
Geotechnical Centrifuge ◽  
Centrifuge Tests ◽  
Soil Temperatures

AbstractHere we compare scaled centrifuge modelling of gelifluction processes with earlier full-scale physical modelling experiments. The objective is to assess the validity of the centrifuge technique for cryogenic slope-process investigations. Centrifuge modelling allows correct self-weight stresses to be generated within a small-scale physical model by placing it in an elevated gravitational field. This paper describes an experiment in which a scaled frozen-slope model was thawed in a gravitational field equivalent to ten gravities. After four cycles of thawing, during which soil temperatures, pore pressures, thaw settlement and downslope soil displacements were continuously monitored, a series of marker columns were excavated to reveal profiles of soil movement. Comparison of these data with those from an earlier full-scale laboratory simulation experiment indicates that thaw-related gelifluction was successfully reproduced during centrifuge modelling. It is concluded that rates of soil shear strain during gelifluction were not time-dependent? since soil displacements in the centrifuge tests were of a similar magnitude to or greater than those observed in the much longer-duration full-scale simulation. This suggests that no transition occurred in soil behaviour from a frictional plastic to a true viscous fluid during the period of high moisture contents immediately following thaw.

Strain Accumulation Procedure During Staged Cyclic Loading of Carbonate Sediments

2014 ◽  
Author(s):  
Nathalie Boukpeti ◽  
Barry Lehane ◽  
J. Antonio H. Carraro
Keyword(s):  
Shear Stress ◽  
Cyclic Loading ◽  
Shear Strain ◽  
Simple Shear ◽  
Soil Strength ◽  
Carbonate Sediments ◽  
Strain Accumulation ◽  
Shear Tests ◽  
Cyclic Shear ◽  
North West

Design of offshore foundation systems requires assessment of the effects of cyclic loading on the soil strength. This paper investigates the applicability of the strain accumulation procedure, which is used to assess the effects of wave loading on the soil strength. Staged undrained cyclic simple shear tests were conducted on a carbonate sediment from the North West shelf of Australia, with varying shear stress amplitude in each stage. The shear strain mobilised at the end of the staged tests is compared with the value predicted by the strain accumulation procedure, using shear strain contours constructed from the results of single amplitude undrained cyclic simple shear tests. It was found that the strain accumulation procedure gives adequate prediction for normalised cyclic shear stress less or equal to 0.3, but largely underestimates the cyclic shear strain for normalised cyclic shear stress greater than 0.3 (the cyclic shear stress being normalised by the effective vertical stress at the end of consolidation).

Physical modelling of a dissolved contaminant in an unsaturated sand

1991 ◽  
Vol 28 (6) ◽  
pp. 829-833 ◽  
Author(s):  
B. Cooke ◽  
R. J. Mitchell
Keyword(s):  
Contaminant Transport ◽  
Scaling Laws ◽  
Physical Modelling ◽  
Saturated Soils ◽  
Test Results ◽  
Centrifuge Modelling ◽  
Geotechnical Centrifuge ◽  
Partially Saturated ◽  
Partially Saturated Soils ◽  
Viable Approach

Computer solutions to the problem of dissolved contaminant movements in saturated soils are readily available. However, for partially saturated soils, extreme nonlinearity of some variables and difficulties in determining values for other variables make computer solutions predicting the movement of dissolved contaminants highly unreliable. Physical modelling in a geotechnical centrifuge is presented as a viable alternative to numerical modelling. Scaling laws for physical modelling are presented in this paper, and dimensional analysis is used to identify potential difficulties in application of model test results to prototype situations. Preliminary results of experimental work are presented. These results indicate that centrifuge modelling may be a viable approach to the evaluation of dissolved contaminant transport in partially saturated soils. Key words: contaminant transport, centrifuge, unsaturated.

Centrifuge modelling of heat-generating waste disposal

1989 ◽  
Vol 26 (4) ◽  
pp. 640-652 ◽  
Author(s):  
F. Poorooshasb ◽  
R. G. James
Keyword(s):  
Waste Disposal ◽  
Field Tests ◽  
Free Fall ◽  
Heat Emission ◽  
Centrifuge Modelling ◽  
Depth Of Penetration ◽  
Geotechnical Centrifuge ◽  
Pressure Changes ◽  
Deformation Patterns ◽  
Theoretical Analyses

A set of experiments, conducted on the Cambridge geotechnical centrifuge and which model the free-fall option for the subseabed disposal of heat-generating waste, is reported. The results reported relate to the morphological effects of model penetration (depth of penetration, deformation patterns, and closure) as well as to the pore pressure changes associated with this penetration. Results regarding the effect of heat emission (from the model penetrators) upon the surrounding soil are also presented. These results are discussed and compared with theoretical analyses and field tests, and conclusions are presented regarding both the processes attendant upon penetration and heating and the relevance of the modelling to the prototype event. Key words: centrifuge modelling, heat-generating waste disposal, projectile penetration.

scholarly journals The Influence of Apparatus Stiffness on the Results of Cyclic Direct Simple Shear Tests on Dense Sand

2020 ◽  
Vol 44 (5) ◽  
pp. 20190471
Author(s):  
M. Konstadinou ◽  
A. Bezuijen ◽  
G. Greeuw ◽  
C. Zwanenburg ◽  
H. M. Van Essen ◽  
...  
Keyword(s):  
Simple Shear ◽  
Shear Tests ◽  
Dense Sand ◽  
Direct Simple Shear

Effect of Material Frame Rotation on the Hardening of an Anisotropic Material in Simple Shear Tests

2018 ◽  
Vol 85 (12) ◽  
Author(s):  
Kelin Chen ◽  
Stelios Kyriakides ◽  
Martin Scales
Keyword(s):  
Simple Shear ◽  
Plastic Anisotropy ◽  
Yield Function ◽  
Strain Response ◽  
Shear Tests ◽  
Stress Strain ◽  
Anisotropic Yield Function ◽  
Torsion Experiment ◽  
Thin Walled Tube ◽  
Material Frame

The shear stress–strain response of an aluminum alloy is measured to a shear strain of the order of one using a pure torsion experiment on a thin-walled tube. The material exhibits plastic anisotropy that is established through a separate set of biaxial experiments on the same tube stock. The results are used to calibrate Hill's quadratic anisotropic yield function. It is shown that because in simple shear the material axes rotate during deformation, this anisotropy progressively reduces the material tangent modulus. A parametric study demonstrates that the stress–strain response extracted from a simple shear test can be influenced significantly by the anisotropy parameters. It is thus concluded that the material axes rotation inherent to simple shear tests must be included in the analysis of such experiments when the material exhibits anisotropy.

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