Effects of Offshore Sampling and Testing on Undrained Soil Shear Strength

Young, Alan G.; Quirós, G.W.; Ehlers, Clarence J.

doi:10.4043/4465-ms

Cited by 15 publications

(7 citation statements)

References 2 publications

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“…Thus, the study supported earlier results by Olson and Dennis (1982) and Young et al (1983), that recommended the empirical procedures used for axially loaded pile design be based on strengths determined from UUP on 3 inch (.076 m) diameter or larger high quality pushed samples. The study confirmed that a conservative bias could be avoided by interpreting the design Su from UUP or miniature vane tests on pushed samples (MVP) as opposed to unconfined compression tests on driven samples (UCD).…”

Section: Reliability Of Various Design Methodssupporting

confidence: 86%

“…OtTshore soil samples, especially if obtained by wireline percussion techniques, are known to be adversely affected by sample disturbance, as shown by Erruich (1971), Quiros et al (1983) and Young et al (1983). This problem is exacerbated at deep water sites where the samples are subjected to large hydrostatic stress relief prior to laboratory testing.…”

Section: $Anmle Disturbance and Shear Strength Determinationmentioning

confidence: 99%

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Historical Development And Assessment Of The Current Api Design Methods For Axially Loaded Pipes

1993

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The design methods for axially loaded piles contained in the API RP 2A, Recommended Practice for Planning. Designing and Constructing Fixed Offshore Platiorms are continually evaluated and updated. To support this activity, API has fimded research over the past 10-12 years which has resulted in the establishment of an internationally recognized data base of axial pile load tests. Subsequent interpretation of these data led to sigrdllcant changes in the design methods for axially loaded piles for both sand and clay. The sand revisions, first incorporated into the 15th Edition of RP 2A provide improved statistical predictions (bias and coeftlcient of variation) of the sand data base than did the design methods for sand contained in earlier editions. The clay revisitms, first incorporated into the 17th Edition of RP 2A provide a statistical description of the clay data base that is similar to descriptions provided by earlier clay methods. Both the revised clay and sand methods provide a more technically sound framework than the methods contained in earlier editions. The revised methods are contained in the current, i.e., the 20th Edition of RP 2A (1993). These revisions have initiated considerable debate, and have prompted the authors to present their thoughts herein. A discussion of the data base, review of the philosophy and evolution of the design method, and a summary and analysis of the key criticisms are provided. The data have been exceedingly useful in formulating design practice, but in our opinion they are too limited to conclusively resolve many of the important issues. While some moditlcations to the present practice seem to be indicated, the References and figures at end of paper 253 authors believe that when combined with a careful site investigation, attention to installation detail and good engineering judgment, RP 2A continues to provide a sound basis for design of axially loaded piles.

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Section: Reliability Of Various Design Methodssupporting

confidence: 86%

Section: $Anmle Disturbance and Shear Strength Determinationmentioning

confidence: 99%

Historical Development And Assessment Of The Current Api Design Methods For Axially Loaded Pipes

1993

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“…Additional coring effects result from the rotational coring tool [ Arman and McManis , 1977; Young et al , 1983]. Figure 9 shows evidence of striation from the cutting shoe in 2‐D X‐rays and 3‐D tomograms of 10B‐5R and 10B‐14R core samples recovered using the rotary cutting method (i.e., Hyace Rotary Core).…”

Section: Discussionmentioning

confidence: 99%

A pressure core based characterization of hydrate-bearing sediments in the Ulleung Basin, Sea of Japan (East Sea)

Yun

Lee

et al. 2011

J. Geophys. Res.

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[1] The physical characteristics of hydrate-bearing sediments sampled by pressure coring from the Ulleung Basin in the Sea of Japan (East Sea) were investigated using an instrumented chamber capable of testing recovered natural sediments that have never left the methane hydrate stability field. The heterogeneous distribution of segregated hydrate veins and lens structures in sediments results in highly variable geophysical and geomechanical properties. The scaled production test was conducted by controlled depressurization of pressure cores while dissociation and gas production were concurrently monitored using various sensors in the instrumented chamber. The hydrate saturation was estimated to be ∼19.5% in the pore space. Data show a sharp reduction in sediment shear and bulk stiffnesses during hydrate dissociation. Relatively fast gas migration was observed, probably along high-conduction planes left behind as hydrate veins dissociated. The spatial distribution of hydrates in sediment was analyzed based on 3-D image processing. The phenomena relevant to the production test and sampling effects during pressure coring are discussed.

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“…Reduction of the effective stresses by this mechanism (Okumura 1971;Procter 1976;Young et al 1983), or by drainage of the sample during storage and testing (Adams and Radhakrishna 197 1 ;Kirkpatrick and Khan 1984), causes significant loss of strength: Proportionally larger changes are observed in stress-strain properties such as modulus or pore-water pressure parameters.…”

Section: Reviewmentioning

confidence: 97%

Stress release, undrained storage, and reconsolidation in simulated underwater clay

Graham¹,

Kwok²,

Ambrosie³

1987

Can. Geotech. J.

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Triaxial testing has examined the influence of storage time and reconsolidation procedures on normally consolidated and overconsolidated samples of reconstituted clay prepared with high pore-water pressures to simulate underwater deposits. "Samples" of illite were consolidated one dimensionally, off-loaded without drainage, stored undrained, reconsolidated, and sheared undrained. The storage times were 15 min, I day, and 7 days. Reconsolidation pressures were (1) isotropic to uO,, (2) isotropic to 0.6 u:,,, and (3) anisotropic to u,',,, 0.53u,',,. The results were compared with "specimens" that had not been off-loaded. Different undrained storage times had no effect on the strengths after reconsolidation, but the strengths were affected by the reconsolidation pressures. Anisotropic reconsolidation produced the best agreement between the control specimens and samples in terms of their strengths andA,-values. The duration of storage time did affect stress-strain parameters such as the undrained compression modulus ESO and the pore-water pressure parameter A,.

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Effects of Offshore Sampling and Testing on Undrained Soil Shear Strength

Cited by 15 publications

References 2 publications

Historical Development And Assessment Of The Current Api Design Methods For Axially Loaded Pipes

Historical Development And Assessment Of The Current Api Design Methods For Axially Loaded Pipes

A pressure core based characterization of hydrate-bearing sediments in the Ulleung Basin, Sea of Japan (East Sea)

Stress release, undrained storage, and reconsolidation in simulated underwater clay

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