A case study: delayed failure of a deep cutting in lodgement till

Hughes, David; Sivakumar, V.; Glynn, D F

doi:10.1680/geng.2007.160.4.193

Cited by 17 publications

(12 citation statements)

References 4 publications

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“…thread rolling) is perhaps not the most accurate way to assess the merits of the present approach. Nevertheless, the authors are well acquainted with the properties of Belfast clay and glacial till, and the PL values recorded using the revised procedure are in close agreement with previously published data on these deposits (Navaneethan & Sivakumar, 2002;Hughes et al, 2007). PL values reported for sleech (SL) and Winnipeg clay (WP) vary between 78 and 110%, and 65 and 85% respectively (Graham et al, 1988), and again agreement is good.…”

Section: Measurement Of Pl Of Various Materialssupporting

confidence: 86%

A new method of measuring plastic limit of fine materials

Sivakumar¹,

Glynn²,

Cairns³

et al. 2009

Géotechnique

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Index properties such as the liquid limit and plastic limit are widely used to evaluate certain geotechnical parameters of fine-grained soils. Measurement of the liquid limit is a mechanical process, and the possibility of errors occurring during measurement is not significant. However, this is not the case for plastic limit testing, despite the fact that the current method of measurement is embraced by many standards around the world. The method in question relies on a fairly crude procedure known widely as the ‘thread rolling' test, though it has been the subject of much criticism in recent years. It is essential that a new, more reliable method of measuring the plastic limit is developed using a mechanical process that is both consistent and easily reproducible. The work reported in this paper concerns the development of a new device to measure the plastic limit, based on the existing falling cone apparatus. The force required for the test is equivalent to the application of a 54 N fast-static load acting on the existing cone used in liquid limit measurements. The test is complete when the relevant water content of the soil specimen allows the cone to achieve a penetration of 20 mm. The new technique was used to measure the plastic limit of 16 different clays from around the world. The plastic limit measured using the new method identified reasonably well the water content at which the soil phase changes from the plastic to the semi-solid state. Further evaluation was undertaken by conducting plastic limit tests using the new method on selected samples and comparing the results with values reported by local site investigation laboratories. Again, reasonable agreement was found.

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Section: Measurement Of Pl Of Various Materialssupporting

confidence: 86%

A new method of measuring plastic limit of fine materials

Sivakumar¹,

Glynn²,

Cairns³

et al. 2009

Géotechnique

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“…Morris et al 1992;Konrad and Ayad 1997), decrease in lateral stress (e.g. Hughes et al 2007), and differential deformations (e.g. Sherard 1986;Handy and Lustig 2017).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of failure in saturated and unsaturated clayey geomaterials subjected to (total) tensile stress

Murray

Tarantino

2019

Géotechnique

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The paper presents an experimental investigation into the mechanisms of tensile failure in clayey geomaterials under saturated and unsaturated conditions. An experimental apparatus was developed to test specimens in uniaxial tension with the facility to monitor suction (porewater tension) using high-capacity tensiometers. This allowed interpretation of failure data in terms of effective stress and average skeleton stress for saturated and unsaturated specimens respectively. Experimental data from normally consolidated samples showed that failure under uniaxial tension occurs in shear and tensile cracks form as a combination of Mode I and Mode II fracture. In the saturated range when samples were prepared with de-aired water, tensile failure occurred at deviatoric stresses corresponding to the critical state line derived from triaxial and uniaxial compression tests. When using non-de-aired water and at suction levels approaching the air-entry value, failure occurred at deviatoric stresses lower than the ones corresponding to the critical state line derived from compression tests. It has been suggested that water cavitation may be one of the mechanisms that control premature rupture of saturated clay when subjected to a (total) tensile stress state. Finally, tensile failure data from unsaturated samples showed that there is continuity between saturated and unsaturated states. I. Murray and A. Tarantino 'Mechanisms of failure in saturated and unsaturated clayey geomaterials subjected to (total) tensile stress'

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“…McGown has published a number of papers McGown & Radwan, 1975) which show that fissuring present in Scottish deformation tills led to preferential flow of water through the fissures. Hanranhan (1977) has also observed fissures in Irish till, and an investigation into the failure of a till cutting in Northern Ireland revealed a layer of heavily fissured, stone-free, brown clay coincident with the basal slip plane (Hughes et al, 2007). Fissures were observed in the till at the Loughbrickland site at the toe of the excavation and could be attributed to some combination of shear deformation during formation of the till, stress relief during the excavation and high hydraulic gradients through the till at the base of excavation.…”

Section: Hydrogeology Of Drumlinsmentioning

confidence: 99%

The impact of hydrogeology on the instability of a road cutting through a drumlin in Northern Ireland

Hughes

Clarke

Harley

et al. 2016

QJEGH

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This paper describes the hydrogeological processes which caused unexpected instability and quick conditions during the excavation of a 25m deep cutting through a drumlin in County Down, Northern Ireland. A conceptual hydrogeological model of the cutting, based on pore pressures monitored during and after the excavation demonstrates how quick conditions at the toe of the cutting caused liquefaction of the till. Stability of the cutting was re-established by draining the highly permeable, weathered Greywacke which underlies the drumlin, through the use of a deep toe drain. In spite of this drainage, the cutting was only marginally stable due to the presence of a low permeability zone in the till above the bedrock which limits the reduction of elevated pore pressures within the upper to mid-depths of the drumlin. The factor of safety has been further improved by the addition of vertical relief drains at the crest and berm of the cutting to relieve the pore-pressures within the upper till by intercepting the weathered bedrock. The paper also highlights the importance of carrying out an adequate site investigation compliant with Eurocode 7 and additional monitoring in excavations in stiff, low permeability till.

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A case study: delayed failure of a deep cutting in lodgement till

Cited by 17 publications

References 4 publications

A new method of measuring plastic limit of fine materials

A new method of measuring plastic limit of fine materials

Mechanisms of failure in saturated and unsaturated clayey geomaterials subjected to (total) tensile stress

The impact of hydrogeology on the instability of a road cutting through a drumlin in Northern Ireland

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