Soils can rarely be described as ideally elastic or perfectly plastic and yet simple elastic and plastic models form the basis for the most traditional geotechnical engineering calculations. With the advent of cheap powerful computers the possibility of performing analyses based on more realistic models has become widely available. One of the aims of this book is to describe the basic ingredients of a family of simple elastic-plastic models of soil behaviour and to demonstrate how such models can be used in numerical analyses. Such numerical analyses are often regarded as mysterious black boxes but a proper appreciation of their worth requires an understanding of the numerical models on which they are based. Though the models on which this book concentrates are simple, understanding of these will indicate the ways in which more sophisticated models will perform.

Soil Behaviour and Critical State Soil Mechanics

Publisher Summary
This chapter focuses on fundamentals of poroelasticity. The presence of a freely moving fluid in a porous rock modifies its mechanical response. Two mechanisms play a key role in the interaction between the interstitial fluid and the porous rock: (i) an increase of pore pressure induces a dilation of the rock; and (ii) compression of the rock causes a rise of pore pressure, if the fluid is prevented from escaping the pore network. These coupled mechanisms bestow an apparent time-dependent character to the mechanical properties of the rock. If excess pore pressure, induced by compression of the rock, is allowed to dissipate through diffusive fluid mass transport, further deformation of the rock progressively takes place. The rock is more compliant under drained conditions than undrained ones. The chapter discusses the formulation and analysis of coupled deformation–diffusion processes, within the framework of the Biot theory of poroelasticity. The Biot model of a fluid-filled porous material is constructed on the conceptual model of a coherent solid skeleton and a freely moving pore fluid.

Fundamentals of Poroelasticity

Incompressible porous media models by use of the theory of mixtures

Keywords: Mecanique des sols ; Drainage ; Ecoulement souterrain Reference Record created on 2004-09-07, modified on 2016-08-08

Applications of soil physics.

Introduction to Soil Mechanics and Foundations. Physical Characteristics of Soils and Soil Investigations. Stresses, Strains and Elastic Deformations of Soils. One--Dimensional Consolidation Settlement of Fine--Grained Soils. Shear Strength of Soils. A Critical State Model to Interpret Soil Behavior. Bearing of Capacity of Soils and Settlement of Shallow Foundations. Pile Foundations. Two--Dimensional Flow of Water Through Soils. Stability of Earth Retaining Structures. Slope Stability. Appendices. Answers to Selected Problems. References. Index.

Soil Mechanics and Foundations

This paper describes the results of numerical analysis of the effects of installing a driven pile. The geometry of the problem has been simplified by the assumption of plane strain conditions in addition to axial symmetry. Pile installation has been modelled as the undrained expansion of a cylindrical cavity. The excess pore pressures generated in this process have subsequently been assumed to dissipate by means of outward radial flow of pore water. The consolidation of the soil has been studied using a work-hardening elasto–plastic soil model which has the unique feature of allowing the strength of the soil to change as the water content changes. Thus it is possible to calculate the new intrinsic soil strength at any stage during consolidation. In particular the long-term shaft capacity of a driven pile may be estimated from the final effective stress state and intrinsic strength of the soil adjacent to the pile. A parametric study has been made of the effect of the past consolidation history of the soil...

Driven piles in clay - the effects of installation and subsequent consolidation

Closed form solutions are presented for the expansion of cylindrical and spherical cavities in an ideal, cohesive frictional soil. An explicit solution for the pressure-expansion relationship can be obtained for infinitesimal (small strain) deformations. For finite deformations it is necessary to adopt a numerical approach to obtain the complete pressure-expansion relationship and it is found that the cavity pressure approaches a limiting value for infinite deformation. It is, perhaps surprisingly, possible to determine the precise value of this limiting pressure analytically. It is suggested that the small strain solution for a cylindrical cavity is applicable to the interpretation of pressuremeter tests in sand, and that the solutions for limit pressures have application to the problem of pile installation and the end bearing pressure of deep foundations. L'article presente des solutions de forme fermee pour l'expansion de cavites cylindriques et spheriques dans un sol ideal coherent a frottement. On pe...

Cavity expansion in cohesive frictional soils

A theoretical study of the behaviour of structured soil is presented. A new model, referred to as the Structured Cam Clay model, is formulated by introducing the influence of soil structure into th...

A structured Cam Clay model

This paper presents the results of three-dimensional finite-element analyses of circular foundations on the surface of homogeneous, purely cohesive soil. The foundations were assumed to adhere fully to the soil, and compressive, tensile and shear stresses may develop at the interface between the footing and the soil. The predicted ultimate response of the foundations to combined vertical, moment and horizontal loading was compared with other available theoretical predictions. A three-dimensional failure locus is presented for these foundations, based on the numerical predictions. An equation that approximates the shape of the failure locus is also suggested, and this provides a convenient means of calculating the bearing capacity of circular foundations on a uniform clay and subjected to combined loading.

Numerical studies of the bearing capacity of shallow foundations on cohesive soil subjected to combined loading

The stress–strain behaviour of sands is highly nonlinear, even at stresses well below the peak strength of the sand. The hyperbolic model is a reasonable conceptual model for representing the stres...

John P. Carter

Papers

Driven piles in clay - the effects of installation and subsequent consolidation

Cavity expansion in cohesive frictional soils

A structured Cam Clay model

Numerical studies of the bearing capacity of shallow foundations on cohesive soil subjected to combined loading

A finite element study of the pressuremeter test in sand using a nonlinear elastic plastic model