A critical reappraisal of compression index equations

Nagaraj, T. S.; Murthy, B. R. Srinivasa

doi:10.1680/geot.1986.36.1.27

Cited by 155 publications

(40 citation statements)

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“…Correlations between w L and C C (e.g. (Nagaraj and Murthy 1986)) also verifies the observed trend. As illustrated in table 6.1, the initial void ratio of the specimens was dependent on the smectite content.…”

Section: Comparison Of Test Observations With Trends From Literaturesupporting

confidence: 77%

Influence of smectite content on the deformation behaviour of clay

Lodahl¹

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A number of structures are planned to be constructed on or in the Palaeogene clays in Denmark, e.g. the re-development of Aarhus Ø and the construction of the Femern Fixed Link. The Palaeogene clays are generally of very high plasticity, hold low strengths and have high deformation potentials despite being previously compressed by past glaciations. When unloaded the clay adsorbs water and swells profoundly. These geotechnical traits pose a challenge and must be accounted for when designing a structure situated on high plasticity clays. When not considered, the features of the Palaeogene clay may pose a safety concern for the building and settlements may develop over time.Previous studies on Palaeogene clays in Denmark have shown, that the well-known index relations used in Danish geotechnical practice are generally not valid for the in situ behaviour of high plasticity clays. Moreover, several studies illustrates how the vertical yield stress derived from the compression curves of high plasticity clays does not reflect the previously sustained overburden, which normally is the case for clays of low to medium plasticity. The feature have been described as "lack of stress memory".The present thesis investigates the 1D deformation behaviour of high plasticity clays. The effects of the clay mineral smectite on the deformation and swelling potential of the high plasticity clays are of special focus. Based on 1D compression tests the deformation potential of a range of artificial specimens made from mixtures of kaolinite and smectite minerals were investigated. Features typically observed for Danish Palaeogene clays were also observed for the artificial mixtures, e.g. high plasticity and low stiffness, which have both been related to the smectite content in the tested, artificial specimens.Based on a number of tests, conducted following different loading programmes, a deformation model framework is presented which captures the essential features of the high plasticity clays. The model reproduces the compression curves obtained from testing of artificial specimens quite well and have also successfully been applied to reproduce compression curves from oedometer tests on intact natural highly plastic clays presented in literature. Based on the conducted tests it was observed that the lack of stress memory was related to the void ratio increase on a former unloading step, and thus directly affected by the smectite content of the specimen and the extent of unloading. It was also found that the compression potential in normally and overconsolidated conditions is dictated by smectite content but also affected by the length of the stress path followed during testing. III ResuméFlere bygge-og anlaegsprojekter er planlagt opført på de danske palaeogene lere, f.eks. udviklingen af Aarhus Ø og etableringen af den faste forbindelse over Femern Baelt. De palaeogene lere har generelt meget høj plasticitet, lave styrker og høje deformationspotentialer, selvom de tidligere er blevet belastet af isen under forgangne istider. Nå...

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Section: Comparison Of Test Observations With Trends From Literaturesupporting

confidence: 77%

Influence of smectite content on the deformation behaviour of clay

Lodahl¹

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“…They suggested the values of a and b to be 1.099 and 0.223 [15]. Then they revised a and b invariants to 1.122 and 0.2343 respectively [16].…”

Section: Normalising Inherent Compression Curvesmentioning

confidence: 99%

“…7. For comparison, the normalised compression lines proposed by Murthy 1983, 1986 [15], [16] are also plotted in this figure. As can been seen in Fig.…”

Section: Normalising Inherent Compression Curvesmentioning

confidence: 99%

Intrinsic Compression Characteristics of an Expansive Clay From Western Australia

Habibbeygi¹

2017

geomate

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Intrinsic compression behaviour of an expansive clay from Western Australia is investigated using the intrinsic framework in this study. Oedometer results conform with the intrinsic concept at post-yield phase. However, there is a great impact of initial water content on the compression curves at pre-yield stage. It specifies that there is an initial structure similar to a natural clay structure which resists applied forces at this phase and it is related to the amount of initial water content at the preparation stage. Nonetheless, this interparticle bonding is demolished when vertical stress becomes greater than remoulded yield stress. The findings also show that the remoulded yield stress of a reconstituted clay decreases non-linearly with the increase of initial water content, and is remarkably affected by its clay mineralogy. The remoulded yield stress of a soil with the predominant clay of smectite is far greater than those of other clay minerals despite having the same normalised initial void ratio value ( 0 ⁄ ). Moreover, remoulded yield stress of an expansive soil with main clay mineral of smectite decreases more abruptly than for other clay minerals reported in the literature. Reconstituted compression indexes ( * , 100 * ) for clays with a considerable amount of smectite are also greater than respective values for other clay minerals.

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“…In fact, earlier such attempts in the analysis of soil behaviour (Nagaraj & Srinivasa Murthy, 1983, 1985, 1986a, 1986bNagaraj et al, 1990Nagaraj et al, , 1993Nagaraj et al, , 1994a have been with reference to an intrinsic state parameter (eae L ) and its variation with effective stress for reconstituted clays. Examination of the void index and intrinsic parameter reveals that both are identical and intended to take into account the type and amount of clay minerals and non-clay constituents in the soil:…”

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confidence: 99%

“…The factor b has been evolved from double-layer considerations and examined on the basis of normalization of published compression data of reconstituted clays (Nagaraj & Srinivasa Murthy, 1983, 1986a. Both approaches are complementary to each other and reinforce the direction by which analysis can be pursued.…”

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confidence: 99%