Variation of shear modulus of a clay with pressure and overconsolidation ratio

A method is described for expressing the elastic shear modulus of a clay as a power function of the applied pressure and the preconsolidation pressure. The method has the advantage that it incorporates the concept of normalisation of clay properties with respect to pressure, whilst allowing a realistic variation of the shear modulus with overconsolidation ratio to be described. A further advantage is that, since the shear strength is often expressed in a similar manner, the rigidity index G/su, which plays an important role in many geotechnical engineering analyses, can be expressed as a power function of the overconsolidation ratio. The new method is compared with some existing data showing the variation of the stiffness of clays

Determination of undrained strengths by cone penetration tests.

Calculations have been presented for the loads on a cone penetrometer in a cohesive material, with the validity of the calculations being limited at present to a penetrometer near the surface of a soil. The undrained strength of a cohesive soil could therefore be back-analysed from measurements of loads on cone penetrometers. -from Author

Influence of soil stiffness and lateral stress on the results of in-situ soil tests

The results of in-situ tests depend on the strength, stiffness and permeability properties of the ground, as well as the in-situ stresses. Laboratory and theoretical studies have shown that two quantities are particularly important in the understanding of in-situ tests: the horizontal stress and the soil stiffness. The effect of these quantities on test results can sometimes be advantageous, in that it can allow the stiffness or horizontal stress to be estimated, but is more often inconvenient, since it adds a degree of uncertainty to the interpretation of the tests. Results are presented for the cone penetrometer, piezocone, Marchetti dilatometer and cone-pressuremeter, and tests in both clays and sands are considered. Recommendations are made for use of appropriate in-situ tests in different circumstances

APPLICATIONS OF SOIL MECHANICS THEORY TO THE PROCESSING OF CERAMICS.

The purpose of this paper is to introduce the basic concepts of soil mechanics to workers in the materials processing industries, especially those concerned with the forming of ceramics. After a brief description of soil as a three-phase material, and the importance of the concept of effective stress, some basic tests used in conventional soil mechanics are outlined, with an emphasis on the rate effects resulting from drainage of fluid from the soil skeleton

Direct solution of plasticity problems in soils by the method of characteristics.

The application of similar methods to problems of axial symmetry, and to soils with non-homogeneous properties is described and some illustrative examples given. The method of characteristics may also be used for the solution of the plastic displacement equations, although the exact form which these equations should take is still a matter of controversy. -from Author

Calculation of stresses on shallow penetrometers and footings.

A short review is made of the types of analyses available for cone penetration tests. The assumptions involved in analyses using the method of characteristics (slip line methods) are discussed, and some analyses of problems of shallow cone penetration and bearing capacity are presented. Graphical results are presented for the variation of the cone factor, Nc, with the angle and roughness of a shallowly penetrating cone. The second example of the application of the method is to problems of bearing capacity on soils with strength increasing with depth, and is relevant to the design of very large concrete gravity oil-production platforms. Numerical values of bearing capacity factors for smooth and rough circular footings on non-homogeneous soils are presented and compared with the equivalent values for strip footings.-from Author

Soil mechanics - property characterization and analysis procedures.

Recent and current developments in the understanding and description of soil behaviour and in the numerical analysis of geotechnical problems are discussed. The discussion of soil properties is concentrated on the pattern of behaviour of clays in monotonic tests, and the important correlations of the strength and stiffness of clays with the level of effective stresses and overconsolidation ratio. -from Author

Calculation of stresses on shallow penetrometers and footings.

A short review is made of the types of analyses available for cone penetration tests. The assumptions involved in analyses using the method of characteristics (slip line methods) are discussed, and some analyses of problems of shallow cone penetration and bearing capacity are presented. Graphical results are presented for the variation of the cone factor, Nc, with the angle and roughness of a shallowly penetrating cone. The second example of the application of the method is to problems of bearing capacity on soils with strength increasing with depth, and is relevant to the design of very large concrete gravity oil-production platforms. Numerical values of bearing capacity factors for smooth and rough circular footings on non-homogeneous soils are presented and compared with the equivalent values for strip footings.-from Author

Direct solution of plasticity problems in soils by the method of characteristics.

The application of similar methods to problems of axial symmetry, and to soils with non-homogeneous properties is described and some illustrative examples given. The method of characteristics may also be used for the solution of the plastic displacement equations, although the exact form which these equations should take is still a matter of controversy. -from Author

Predictions of the results of laboratory tests on a clay using a critical state model.

An elastic-plastic model for describing the stress-strain behaviour of a clay is presented. The model is based on the Modified Cam-Clay model, but includes an additional yield surface to model failure of overconsolidated samples on a Hvorslev surface. The model is used to predict the behaviour of a kaolinite in a number of repeated loading tests, based on the results of monotonic triaxial compresson and extension tests. -from Author