J. P. Carter

A THEORY OF FINITE ELASTIC CONSOLIDATION

Presented in this paper is a general theory describing the consolidation of a porous elastic soil. The formulation allows for the occurrence of finite geometry changes and finite elastic strains during the consolidation process. The governing equations have been cast in a rate form and the laws which determine deformation and pore fluid flow, i.e. Hookes law and Darcys law, are presented in a frame indifferent manner. A numerical technique is described that provides an approximate solution to the governing equations. The theory and the solution technique are illustrated by several examples of practical interest.

Elastic consolidation around a deep circular tunnel

A method of analysis is presented for the consilidation of a linear elastic soil due to the cutting of a long and deep circular tunnel. Solutions have been obtained for the time dependent displacements and stress changes occurring in the soil surrounding the tunnel opening.

A neural network model for the uplift capacity of suction caissons

Abstract Suction caissons are frequently used for the anchorage of large compliant offshore structures. The uplift capacity of the suction caissons is a critical issue in these applications, and reliable methods of predicting the capacity are required in order to produce effective designs. In this paper a back-propagation neural network model is developed to predict the uplift capacity of suction foundations. A database containing the results from a number of model and centrifuge tests is used. The results of this study indicate that the neural network model serves as a reliable and simple predictive tool for the uplift capacity of suction caissons. As more data becomes available, the model itself can be improved to make more accurate capacity prediction for a wider range of load and site conditions. The neural network predictions are also compared with finite element based predictions.

Finite element analysis of coupled thermoelasticity

Most thermal stress analyses assume that the determination of the temperature field is uncoupled from that of the stress and displacement fields, while assuming that the stress and displacement fields depend on the temperature field. This semi-coupled approach to thermoelasticity is not entirely consistent. In this paper a variational principle for the fully coupled theory of thermoelasticity is developed. This is used to obtain a finite element approximation which is then compared with analytical solutions. An assessment is also made of the importance of the full coupling.

Withdrawal of a compressible pore fluid from a point sink in an isotropic elastic half space with anisotropic permeability

Abstract The complete solution is presented for the transient effects of pumping fluid at a constant rate from a point sink embedded in a saturated, porous elastic half space. It is assumed that the medium is homogeneous and isotropic with respect to its elastic properties and homogeneous but anisotropic with respect to the flow of pore fluid. The soil skeleton is modelled as an isotropic linear elastic material obeying Hookes law while the pore fluid may be compressible with its flow governed by Darcys law. The solution has been evaluated for a particular value of Poissons ratio of the solid skeleton, i.e. 0.25, and the results have been presented graphically in the form of isochrones of excess pore pressure and surface profile for the half space. The solutions presented may have application in practical problems such as dewatering operations in compressible soil and rock masses and in the extraction of petroleum products from the crust of the earth.

Deformation Analysis in Soft Ground Improvement

Preface Notation 1 Introduction 1.1 What is ground improvement and when and why is it necessary? 1.2 Techniques of ground improvement 1.3 Why do we need to estimate ground deformations? 1.4 What is this book all about? 1.5 References 2 Modelling Soft Clay Behaviour 2.1 Introduction 2.2 Initial stiffness and undrained shear strength 2.3 Modelling the embankment construction process 2.4 Effect of large deformations on embankment stability 2.5 Buoyancy effects due to large deformation 2.6 Summary 2.7 References 3 Vertical Drains 3.1 Consolidation theory for prefabricated vertical drains 3.2 Parameter determination 3.3 Optimum PVD installation depth 3.4 Two-dimensional modelling of PVD-improved soil 3.5 Modelling a large scale laboratory test 3.6 Application to a case history 3.7 Summary 3.8 References 4 Vacuum Consolidation 4.1 Introduction 4.2 Field methods for vacuum consolidation 4.3 Theory of consolidation due to vacuum pressure 4.4 Characteristics of vacuum consolidation 4.5 Optimum PVD penetration depth 4.6 Estimating deformations induced by vacuum pressure 4.7 Deformations associated with the vacuum-drain method 4.8 Summary 4.9 References 5 Soil-cement Columns 5.1 Introduction 5.2 Settlement predictions 5.3 Degree of consolidation 5.4 Settlement - time curve 5.5 Deformations induced by column installation 5.6 Summary 5.7 References 6 Concluding Remarks 6.1 What else needs to be done? 6.2 Hybrid soft ground improvement techniques 6.3 References Index

A semi-analytical finite element method for three-dimensional consolidation analysis

Abstract An efficient formulation, based on a semi-analytical finite element method, is described for elasto-plastic analyses of consolidation of an axi-symmetric soil body subjected to three-dimensional loading. Expressing the field quantities in the form of discrete Fourier series results in a set of modal equations that can be solved separately. This has the effect of considerably reducing the necessary storage and the cost of solving three-dimensional problems. The numerical method is applied to the problem of a laterally loaded pile in consolidating elasto-plastic soil.

On the volumetric deformation of reconstituted soils

This paper reviews the phenomenon of volumetric hardening, which is a common feature of the mechanical behaviour of many geo-materials. Three different material idealizations have been proposed to describe this hardening, and the paper contains the corresponding mathematical formulation. These idealizations vary in their complexity and hence their ability to capture different aspects of real material behaviour. Any of the three postulates can be implemented into most constitutive models. As a demonstration of their capabilities, the postulates have been implemented into the well-known modified Cam Clay model, and computations are made with the resulting new constitutive models. It is seen that the new models can successfully represent important features of soil behaviour such as plastic yielding associated with loading inside the current virgin yield surface, the loosening or densifying of granular soils caused by shearing, and the accumulation of both volumetric and distortional deformation caused by repeated drained loading over a large number of cycles.

A Constant Normal Stiffness Direct Shear Device for Static and Cyclic Loading

A device has been designed and built to carry out both static and cyclic direct shear tests on specimens of soil and rock and on interfaces of soil or rock and construction materials. The device has the special capability of allowing the shear deformation to proceed under conditions of constant normal stiffness. This is in contrast to the more conventional direct shear devices, which permit shearing under conditions of constant normal stress. It is expected that the constant normal stiffness conditions will be more representative of many in-situ conditions of shear deformation; an important example occurs at the interface of a pile and the formation in which it is placed (particularly those piles that are grouted into the formation). When used with a servo-controlled testing machine the device is capable of applying either static or cyclic shear loading to the test specimens utilizing either load or displacement control. The device is described in this paper, and typical results are presented for static and cyclic loading of a variety of interfaces including some that dilate on shearing and others that collapse as they are sheared.

Analysis of the compression of structured soils using the disturbed state concept

The aim of this note is to quantify the influence of soil structure on the compression behaviour of natural soils using the disturbed state concept (DSC). The behaviour of the fully adjusted state is chosen to be that of the corresponding soil in a reconstituted condition so that the disturbance function is a direct measure of the effects of soil structure. A new DSC compression model is proposed. This model is able to describe the compression behaviour of structured soils under loading, swelling and reloading. Special versions of the proposed model are also described for situations (a) where the compression behaviour of the corresponding reconstituted soils is linear in the e–ln p′ space and (b) where the compression is one-dimensional. The ability of the proposed model and its various versions to describe the compression behaviour of structured soils has been verified. Copyright