Strength of Weakly Cemented Sands from Drained Multistage Triaxial Tests

Sharma, Mahesh; Baxter, Christopher; Moran, Kathryn; Narayanasamy, Raja

doi:10.1061/(asce)gt.1943-5606.0000537

Cited by 30 publications

(16 citation statements)

References 25 publications

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“…On the other hand, cemented soils and rocks can experience irreversible damages in cementing fabric when sheared up to the peak strength in earlier stages. Thus, their peak strengths in later stages become smaller than those in single‐stage tests under similar confining conditions (Kim & Ko, ; Ravi Sharma et al, ). Figure a shows that the peak strengths ( q peak ) obtained from multistage tests are comparable to those from single‐stage tests under similar hydrate saturation and confining stresses, suggesting that the hydrate pore habit formed in the tested specimens is not contact‐cementing.…”

Section: Analyses and Discussionmentioning

confidence: 98%

“…On the other hand, the shearing termination at peak point causes irreversible failures in brittle rocks and cemented soils, thereby leading to the reduced material strengths at the intermediate and final stages as compared to those from the single‐stage tests (Kim & Ko, ; Taheri et al, ). To minimize premature failures in such materials at earlier shearing stages, the volumetric strain is utilized to specify the termination point, for example, the shearing point, at which the volumetric strain returns to zero from the initial contraction ( ε v = 0; Crawford & Wylie, ) or at which the initial contractive volumetric strain turns to be expansive with respect to the axial strain ( dε v / dε a = 0; Pagoulatos, ; Ravi Sharma et al, ). With the termination points at the first and intermediate stages, a pseudo failure envelop can first be constructed, and then parallelly be shifted up to the peak point obtained at the final stage where the specimen is to be sheared to fail.…”

Section: Introductionmentioning

confidence: 99%

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Multistage Triaxial Tests on Laboratory‐Formed Methane Hydrate‐Bearing Sediments

et al. 2018

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A sound understanding of the geomechanical behavior of hydrate-bearing sediments (HBSs) is essential not only for assessing reservoir and wellbore stability during methane gas production but also for projecting the impact of global warming on the stability of geological settings that contain hydrates. This study experimentally investigated the geomechanical responses of laboratory-formed methane-HBS to triaxial shearing under drained conditions. The hydrate pore habit formed in the sediments is noncontact-cementing, which is different from contact-cementing or grain-coating hydrate pore habits formed when the excessive gas method is used. The multistage triaxial test method, which shears a single specimen under different confinements, was employed to examine its applicability in measuring geomechanical properties of the HBS. Conventional single-stage triaxial tests were also performed to serve as baselines. The results show that both the strength and stiffness of HBS increase with increased hydrate saturation and confining stress. Shear dilatancy increases with increased hydrate saturation and decreased confining stress. The peak strength and peak/postpeak shear dilation measured using the multistage tests are comparable to those using the single-stage tests. However, the stiffness measured in later stress stages in the multistage tests was enhanced by the stress-strain history of earlier stages. Therefore, the multistage test offers an efficient way of measuring the strength and volumetric response of the HBS with a much smaller number of specimens than the single-stage test. This benefits the geomechanical characterization of the HBS, as obtaining the pressure cores is extremely costly and preparing lab samples is usually sophisticated and time consuming. Key Points: • Multistage triaxial tests are conducted on noncontact-cementing, hydrate-bearing sediments under drained conditions • The strength, dilatancy, and stiffness of the hydrate-bearing sediments are measured • The multistage test can be a viable and efficient method to measure the strength and dilatancy of the hydrate-bearing sediments

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Section: Analyses and Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Multistage Triaxial Tests on Laboratory‐Formed Methane Hydrate‐Bearing Sediments

et al. 2018

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“…It is quite possible that cohesion (developed after curing for a few weeks) provides a strength that is available at lower strain in cemented backfill, but it can be expected also that the activation of shear planes should nonetheless mobilize some frictional stresses at failure along the interfaces in backfilled stopes (after the initial pore-water pressures have dissipated, which may also take a few days to a few weeks, as shown by Grabinsky (2010) andEl Mkadmi et al (2011)). This combined contribution of cohesion and friction has been observed during experimental tests conducted under drained conditions on cemented soils (e.g., Camusso and Barla 2009;Sariosseiri and Muhunthan 2009;Baxter et al 2011;Sharma et al 2011), as well as on cemented backfill (Lun 1986;Benzaazoua et al 2000;Fall and Nasir 2010). For this reason, the contribution of friction to the shear strength will be considered below.…”

Section: Original Solutionmentioning

confidence: 92%

A modified solution to assess the required strength of exposed backfill in mine stopes

Aubertin

2012

Can. Geotech. J.

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Backfilling contributes to the improvement of ground stability and reduction of ore dilution in underground mines. A critical issue for backfilled stope design is the required strength for the fill material. A practical solution to address this question was proposed by Mitchell and co-workers for stopes with an exposed face and a high aspect ratio (height H over width B). However, this solution is not directly applicable to stopes with a relatively low aspect ratio (H/B). Its application is also restricted by additional limitations on the strength along the fill-rock interfaces and the load applied on top of the backfill. In this note, the model proposed by Mitchell and co-workers is modified to provide an estimate of the required strength of backfill for various geometries, material properties, and surface loads. The modified Mitchell (MM) solution is validated against experimental results. Sample calculations with the MM solution are also presented and discussed.Résumé : Le remblayage contribue à l'amélioration de la stabilité du massif rocheux et au contrôle de la dilution du minerai dans les mines souterraines. Lors de la conception des chantiers remblayés, un aspect critique est la détermination de la ré-sistance requise pour le remblai. Une solution pratique pour répondre à cette question a été proposée par Mitchell et collaborateurs pour des chantiers avec une face exposée et un rapport hauteur sur largeur élevé. Cette solution n'est toutefois pas directement applicable aux chantiers relativement bas et larges (faible rapport hauteur sur largeur). D'autres restrictions limitent l'application de la solution, selon la valeur de la résistance le long des interfaces remblai-roches et la charge appliquée à la surface du remblai. Dans cette note, le modèle de Mitchell et collaborateurs est modifié pour fournir une estimation de la résistance du remblai pour diverses géométries, propriétés de matériaux et charges de surface. La solution de Mitchell modifiée (MM) est validée à partir de résultats expérimentaux. Quelques exemples de calculs avec la solution MM sont aussi présentés et discutés.

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“…A method for conducting multi-stage drained triaxial compression tests on weakly cemented sands and estimating the resulting shear strength parameters was proposed recently (Sharma et al, 2011). However, this type of test is more satisfactory for plastic soils than for brittle soils (Head, 1982).…”

Section: Methodsmentioning

confidence: 99%

Shear strength of microfine cement grouted sands

Markou

Droudakis

2013

Proceedings of the Institution of Civil Engineers - Ground Impr

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Unconsolidated–undrained (single and multi-stage) triaxial compression tests were conducted to evaluate the shear strength of microfine cement grouted sands. Microfine cements of three different types were obtained by pulverising ordinary cements produced in Greece. Multi-stage triaxial compression tests can be used dependably for determination of the shear strength parameters of cement grouted sands. It has been observed that the Mohr–Coulomb failure criterion represents adequately the behaviour of the grouted sands. Grouting with microfine cement suspensions improves the strength of sands significantly, and the improvement is primarily controlled by the water-to-cement (W/C) ratio of the suspensions. The positive effect of microfine cement grouting on the shear strength of sands is mainly the addition of cohesion, which is substantial even at a distance of 1·2 m from the injection point. Grouting with suspension, using W/C = 1 provides the sand with cohesion of about 2·6 MPa. The shear strength parameters vary with axial strain, and cohesion attains a maximum value well before failure.

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Strength of Weakly Cemented Sands from Drained Multistage Triaxial Tests

Cited by 30 publications

References 25 publications

Multistage Triaxial Tests on Laboratory‐Formed Methane Hydrate‐Bearing Sediments

Multistage Triaxial Tests on Laboratory‐Formed Methane Hydrate‐Bearing Sediments

A modified solution to assess the required strength of exposed backfill in mine stopes

Shear strength of microfine cement grouted sands

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