Stephen P. Bentley

Cardiff University

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Ian Smalley

University of Leicester

H. J. Siddle

Cardiff University

Michael Carter

Rothman Institute

M. Carter

University of Wales

Nigel J. Clark

A. Al Masmoum

C. F. Moon

C. Jake Harris

Corteva (United States)

Ken O’Hara-Dhand

University of Leicester

Sue McLaren

University of Leicester

Cooperative Institutions

Cardiff University

University of Leicester

University of Novi Sad

National University of Malaysia

University of Wales

Nottingham Trent University

University of Bedfordshire

University of Sheffield

McGill University

Coventry University

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Mineralogy of a Norwegian postglacial clay and some geotechnical implications

The Canadian Mineralogist (1980)

Stephen P. Bentley Nigel J. Clark Ian Smalley

Crystalline and amorphous phases present in a sensitive clay from Oslo are examined using several independent analytical techniques. Major crystalline phases are feldspars (50 wt.%), hornblende (approx. 18 wt.%), quartz (8 wt.%), clay mica (12 wt.%) and chlorite (approx. 7 wt.%). Selective-dissolution studies in association with energy-dispersive X-ray investigations reveal polymictic assemblages that are cemented by amorphous iron oxide. Amorphous iron compounds (approx. 2 wt.%) also form discrete particles and coatings on hornblende. The dissolution technique disaggregates these cemented mineral assemblages and affords an improved definition of the constituent particles. It is inferred that the minute particles ( 0.2 microns) and the amorphous iron oxide which make up the polymictic assemblages probably are common constituents of Norwegian and Canadian clays. Although these materials can appear as one bonded mass, their roles in the formation of sensitive-clay microstructures are considered to be independent. By enhancing interparticle bonding at low stresses, the glacially derived colloidal particles may promote the development of high-porosity structures. The amorphous coatings, produced by in situ chemical weathering, act as cementing agents and augment the established soil structure. Variations in the degree of cementation exhibited by the engineering characteristics of clays reflect differences in timing of the cementation.

Cementation (geology)

Hornblende

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Citations (10)

Book review: Urban geology in Wales: 3.

Géotechnique (2011)

Stephen P. Bentley

10.1680/geot.2011.61.3.279

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Citations (0)

Partitioning of heavy metals on soil samples from column tests

Engineering Geology (2001)

Raymond N. Yong Wan Zuhairi Wan Yaacob Stephen P. Bentley C. Jake Harris B. K. Tan

Soil test

10.1016/s0013-7952(00)00111-3

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Citations (47)

Loess and fragipans: Development of polygonal-crack-network structures in fragipan horizons in loess ground

Quaternary International (2015)

Ian Smalley Stephen P. Bentley Slobodan B. Marković

Soil structure

10.1016/j.quaint.2015.01.034

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Citations (16)

Significance of amorphous material relative to sensitivity in some Champlain clays: Discussion

Canadian Geotechnical Journal (1980)

Stephen P. Bentley

In considering the significance of amorphous materials to the sensitivity of Canadian clays the authors have made an informative contribution to the sensitive-clay literature. The authors have established a comprehensive framework for analysis that other researchers would do well to follow in subsequent studies. In the writer's opinion these analyses should be considered in the light of all research into amorphous materials and a brief review of Norwegian work would be appropriate. The Norwegians led sensitive-clay research into the 1960's and some aspects of this work, augmented by work recently performed by the writer, are relevant to the paper under discussion. The presence of amorphous compounds in sensitive clays has been recognized by several Norwegian workers (Moum 1967; Bjerrum et al. 1969; Lerken 1970). The amorphous matter appears to be insoluble-iron and aluminium compounds, which are liberated from mineral phases by in situ weathering. Other soluble cations, notably K+, Ca2+, and Mg2+ also are liberated by mineral disintegration; these do not form amorphous precipitates but they can have an important electrochemical influence on the clay. It is evident from laboratory observations that mineral disintegration becomes active when the leaching process introduces fresh waters, which result in a change of pH and oxidation capacity (Bjerrum 1967; Moum 1967). The interaction of these released cations with the clay system has been summarized by Lerken (1970); the cations may be leached out with the remaining salts in the pore water, enter adsorbed positions by displacing more weakly adsorbed cations, or precipitate as insoluble amorphous compounds. From work concerning chemical additions to quick clays Lerken (1970) concluded that there is a fundamental differ-

10.1139/t80-071

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Citations (10)

Mineralogy of sensitive clays from Quebec

The Canadian Mineralogist (1978)

Stephen P. Bentley Ian Smalley

Source

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Citations (19)

The evolution of landslide research in the South Wales Coalfield

Proceedings of the Geologists Association (1990)

Stephen P. Bentley H. J. Siddle

Welsh

10.1016/s0016-7878(08)80205-2

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Citations (5)

Practical guidelines for microwave drying of soils

Canadian Geotechnical Journal (1986)

Michael Carter Stephen P. Bentley

This note provides practical guidelines for the use of microwave drying in the determination of soil water contents. The results are based on over 250 individual tests performed on sand, sandy clay, estuarine clay, marl, lateritic clay, kaolin, and bentonite (sodium). All soils tested fell into one of three distinct categories and drying times for each are presented as a function of initial sample mass. The recommended drying times give results within 0.5 wt% of those obtained by standard oven drying. No limitations were observed in the performance of a 600-W domestic microwave oven. Key words: water contents, microwave, drying, sand, silt, clay, procedures.

Silt

Microwave oven

Bentonite

Marl

Soil test

10.1139/t86-088

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Citations (8)

Frost Susceptibility

Michael Carter Stephen P. Bentley

There are many factors that affect frost susceptibility, including clay mineralogy and the number of freeze-thaw cycles, but four factors are of particular significance in affecting the amount of ice segregation during soil freezing: the pore size of the soil; the moisture supply; the rate of heat extraction; and the confining pressure. The test that is usually considered to be the defining measurement of frost susceptibility is the frost heave test which essentially consists of freezing a soil specimen in a mould by cooling it at the top face, therefore applying a temperature gradient, and measuring the amount of frost heave. Reliance on frost heave alone may not be sufficient since soils may exhibit little heave but still show appreciable weakening on thawing. To overcome these problems, methods have been developed that rely on more standard testing to identify frost-susceptible soils, principally grading, moisture content and plasticity testing.

Frost heaving

Frost (temperature)

Frost weathering

10.1002/9781119130888.ch9

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Citations (2)

Inter‐particle cementation in Canadian post‐glacial clays and the problem of high sensitivity (S_t > 50)

Sedimentology (1978)

Stephen P. Bentley Ian Smalley

ABSTRACT A new explanation of the sensitivity exhibited by Canadian clay sediments is outlined. The mechanism involves cementation of the microstructure and is based on the interaction of primary mineral particles with amorphous matter. The particles appear to be coated with amorphous matter and during sedimentation links develop as the particles come into contact. The speed of the sedimentation, the formation of cementitious links at low stresses and the post‐depositional rise in pH enhance the development of the high porosity structures.

Cementation (geology)

Sedimentation

Particle (ecology)

10.1111/j.1365-3091.1978.tb00314.x

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Citations (17)