Showing papers in "Geotechnique in 1975"
TL;DR: The visco-plastic model is established as a realistic general description of soil behaviour as well as a computationally convenient fiction for solving any properly formulated plasticity problem as discussed by the authors.
Abstract: The visco-plastic model is established as a realistic general description of soil behaviour as well as a computationally convenient fiction for solving any properly formulated plasticity problem. T...
948 citations
TL;DR: In this paper, the authors established the loading on a circular tunnel in the "elliptical" mode of deformation, making certain simplifying assumptions, and the effects of shear forces between ground and lining were first ignored and subsequently introduced in an explicit manner.
Abstract: Neither the ground around a tunnel nor, usually, the tunnel lining, behaves in an elastic manner. Nevertheless, the linear characteristic of an elastic or visco-elastic analysis has great merit, particularly when, as frequently occurs, limitations of knowledge of the behaviour of the ground do not justify greater elaboration. This Paper sets out to establish the loading on a circular tunnel in the ‘elliptical’ mode of deformation, making certain simplifying assumptions. The effects of shear forces between ground and lining are first ignored and subsequently introduced in an explicit manner. Bending moments in a lining are related to a stiffness factor, Rs. While a higher mode of deformation of a tunnel lining is only applicable to problems of stability for thin linings, nevertheless, consideration of this condition allows the coefficient of ground reaction a to be evaluated for conditions of asymmetrical deformation. Direct radial loading of a tunnel lining is related to its compressibility factor Rc...
334 citations
TL;DR: In this paper, a model of a rigid block on a plane surface is used to analyse the effect of inertia forces and pore-pressures on the stability of an earth dam or embankment during strong earth quakes.
Abstract: In the design of earth dams and embankments under earthquake loading conditions, displacements offer a better criterion than a factor of safety on shear strength. The displacement depends on shear strength, inertia forces and pore-pressures generated during the earthquake. The model of a rigid block on a plane surface is used to analyse the effect of inertia forces and pore-pressures on the stability of an earth dam or embankment during strong earth-quakes. The study is based on limit equilibrium principles and the material obeys the Mohr-Coulomb failure criterion with effective stresses. It is shown that by using the pore-pressure parameters A and B, the excess pore-pressures generated during an earthquake can be accounted for in the effective stress analysis. It is also shown that displacements during an earthquake can be easily calculated by using simple pulses. Several interesting conclusions are drawn and an example of application of the method to earth dams and embankments is given. Dans le calcul d...
272 citations
TL;DR: In this paper, a simple and versatile hydraulically operated triaxial apparatus has been developed for stress path testing, which can be used with any convenient pressure control and recording system.
Abstract: A simple and versatile hydraulically operated triaxial apparatus has been developed for stress path testing. The apparatus is described and the range of tests which can be performed is discussed. These include both stress controlled and strain controlled tests. Some typical test results are presented and are used to illustrate the fact that under undrained conditions the deformation of the sample is a function only of the magnitude and sign of the stress difference, and is not otherwise influenced by the absolute magnitude of the total stress changes. The apparatus can be used with any convenient pressure control and recording system. A simple adaptation of the self-compensating mercury control system is illustrated. Un appareil triaxial simple et universel hydraulique, a ete cree pour des essais de traction. L'appareil est decrit et la portee des essais qui peuvent etre realises, est discutee. Ceux-ci comprennent des essais de traction controlee ainsi que des essais de deformation controlee. Quelques res...
267 citations
TL;DR: In this article, the authors discuss the possibility of improving the mechanical characteristics of fine saturated soils to a great depth by a technique known as dynamic consolidation, which is supplied by repeated high intensity impacts.
Abstract: This Paper discusses the possibility of improving the mechanical characteristics of fine saturated soils to a great depth by a technique known as dynamic consolidation. The energy required is supplied by repeated high intensity impacts. A review is made of the fundamental research which was carried out to gain an understanding of the mechanisms involved; it treats four main points: (a)|the compressibility of saturated soils due to the presence of micro-bubbles; (b) the gradual liquefaction under repeated impacts; (c) the changes of permeability of a soil mass due to the creation ofjissures; (d) the thixotropic recovery. The role played by adsorbed water in the last two points is reviewed. The various stages of dynamic consolidation are then summarized in graphical form; the resulting vibrations are also discussed. The control and engineering design parameters are then discussed and the ‘dynamic oedometer’, a tool specially developed for that purpose, is described. The technique is then illustrated by fiel...
244 citations
TL;DR: In this article, the load-settlement relationship for plate loading of an isolated stone column in soft clay was predicted prior to field testing, based on the theory used by Hughes and Withers (1974).
Abstract: The load-settlement relationship for plate loading of an isolated stone column in soft clay was predicted prior to field testing. The column was constructed by vibro-replacement and, after the test, was excavated to check its dimensions. The theory used was proposed on the basis of laboratory model tests by Hughes and Withers (1974). The purpose was to verifv the theory on a field scale. A standard site investigation supplemented by Cambridge and Menard pressuremeter tests provided basic soil parameters. The ultimate column load depends on the friction angle of the gravel used to form the column, the size of the column formed and the restraint of the clay on the uncemented gravel. To predict the load-settlement curve the essential radial stress-strain data for the clay were obtained from a Cambridge pressuremeter. The prediction is excellent if allowance is made for transfer of load from column to clay through side shear and correct column size. Accurate estimation of column diameter is the major factor i...
218 citations
TL;DR: In this paper, the finite element method has been applied to study the behavior of vertically loaded single piles and pile groups in a homogeneous linearly elastic medium, and three-dimensional and axisymmetric ele-...
Abstract: The finite element method has been applied to study the behaviour of vertically loaded single piles and pile groups in a homogeneous linearly elastic medium. Three-dimensional and axisymmetric ele-...
165 citations
TL;DR: In this article, the secondary compressibility of Mexico City clay with special reference to the effects of previous secondary compression and thixotropic hardening was investigated by means of one-dimensional consolidation tests run on specimens in the following states: natural undisturbed, artificially sedimented, remoulded at natural water content and hydrogen peroxide treated.
Abstract: Composition and compressibility characteristics of Mexico City clay were investigated using samples with natural water contents in the range of 421–574%. The composition study included scanning electron microscopy, X-ray diffraction and chemical analyses, as well as measurements of physical properties. Compressibility characteristics were investigated by means of one-dimensional consolidation tests run on specimens in the following states: natural undisturbed, artificially sedimented, remoulded at natural water content, remoulded-aged, and hydrogen peroxide treated. The primary objective was to study the secondary compressibility of Mexico City clay with special reference to the effects of previous secondary compression and thixotropic hardening. Compositional analysis indicated 5–10% sand-sized particles, most of which are calcareous ooliths (the remainder of this size fraction is a suite of heavy minerals); 55–65% of the whole sample is composed of silt-sized siliceous microfossils, mostly diatoms; 20–3...
150 citations
TL;DR: In this article, repeated load triaxial tests have been carried out on samples of Keuper marl reconstituted from a slurry and measurements were made of permanent and resilient strain and the mean value of pore-pressure.
Abstract: Repeated load triaxial tests have been carried out on samples of Keuper marl reconstituted from a slurry. The stress history of each sample was controlled and overconsolidation ratios between 2 and 20 were used. The repeated load tests were carried out undrained and involved the application of cyclic deviator stresses at a frequency of 10 Hz and the work was done in the context of the pavement design problem though the results may well be relevant to other situations such as those occurring beneath off-shore gravity structures. Measurements were made of both permanent and resilient strain and the mean value of pore-pressure. It was shown that even after 106 cycles of stress, failure had not occurred in most of the samples although strains as high as 8% had developed in the more highly overconsolidated cases. Pore-pressures built up to constant positive values for lightly over-consolidated samples within about 104 cycles. For heavily overconsolidated samples, however, negative values were still building up...
135 citations
TL;DR: In this article, the authors used direct tension tests and simple bending tests on soil structures such as multilayer pavements and earth dams to find zones of total stress tension and steep stress gradient.
Abstract: Zones of total stress tension and steep stress gradient occur in soil structures such as multilayer pavements and earth dams, and direct tension tests and simple bending tests on soils could be use
84 citations
TL;DR: In this paper, the authors investigated the effectiveness of stone columns in reducing the settlement of high embankments built on soft alluvium, and found that the columns hadno apparent effect on the performance of the embankment.
Abstract: To investigate the effectiveness of stone columns in reducing the settlement of high embankments built on soft alluvium, stone columns were constructed under one end of the East Brent trial embankment using the vibro-flotation replacement technique. Here the alluvium was 27·5 m thick, the columns were O·9 m in diameter and 11·3 m long, and they were constructed on a triangular grid at 2·4 m centres. The embankment was built to a height of 7·9 m. The foundations were instrumented, and a comparison of the piled and unpiled ground shows that the columns hadno apparent effect on the performance of the embankment. Some of the construction problems are commented on, and the performance records andpossible reasons for the inefiectiveness of the columns are presented in the Paper. Ajin d'enqut?ter sur l'eficacite de colonnes en Pierre dont l'objet est de reduire le tassement de hauts remblais poses sur un depot alluvionnaire mou, de telles colonnes ont et econstruites audessous d'une extremitedu remblai d'essai d...
TL;DR: In this paper, Ham River sand was prepared at high and low porosities by pouring through air or a liquid, the techniques being alternated for layered samples and some samples were reinforced with horizontal sheets of various materials.
Abstract: Samples of Ham River sand were prepared at high and low porosities by pouring through air or a liquid, the techniques being alternated for layered samples. Some samples were reinforced with horizontal sheets of various materials. To avoid edge effects near lubricated platens in triaxial compression, strains in the middle third of each sample were recorded in accurate detail. Changing the relation of the plane of deposition to the major principal stress direction revealed inherent anisotropy effects. Stress-strain and strength data show the influence of porosity, layer geometry and horizontal reinforcing sheets. In homogeneous samples the orientation of lines of zero extension in the maximum-shear plane depended on porosity but not on current strain or inherent anisotropy. Inherent anisotropy did not affect the stress-dilatancy relationship, nor did changing its axes affect the virtual coincidence of stress and strain rate axes. But pre-failure strains were largely influenced by inherent anisotropy at both...
TL;DR: In this paper, the stress-strain relations of a cemented sensitive clay were studied experimentally by loading soil samples along different effective stress paths under axisymmetric and plane strain conditions.
Abstract: The stress-strain relations of a cemented sensitive clay are studied experimentally by loading soil samples along different effective stress paths under axisymmetric and plane strain conditions. Th...
TL;DR: Anisotropic elasticity may be considered as a suitable mathematical model for the small strain deformation behavior of an overconsolidated clay as discussed by the authors, and the predictions of the model will be compared with the results of some laboratory compression tests on samples of undisturbed London Clay from the site of the Barbican Arts Centre.
Abstract: Anisotropic elasticity may be considered as a suitable mathematical model for the small strain deformation behaviour of an overconsolidated clay. The predictions of the model will be compared with the results of some laboratory compression tests on samples of undisturbed London Clay from the site of the Barbican Arts Centre and it will be seen that the agreement between the model predictions and the test results is satisfactory. The effects of stress and stress history on the elastic parameters for undisturbed London Clay will be investigated by comparing the results of laboratory tests on samples taken from several locations within the London Clay basin. L'elasticite anisotrope peut etre consideree comme un modele mathematique valable pour le comportement de la deformation d'une argile surconsolidee sous faible contrainte. Les previsions du modele seront comparees avec les resultats de quelques essais (de laboratoire) de compression faits sur les echantillons d'argile intacte pris a Londres a l'emplaceme...
TL;DR: In this paper, the results of an experimental study of the soil deformations near laboratory-scale cantilever flexible sheet pile walls in dry sand are reported, and a simple analytical method is given which links the deformations in the sand with deflexions of the wall and it is found to give good predictions of the settlements and other observed behaviour.
Abstract: The Paper reports the results of an experimental study of the soil deformations near laboratory-scale cantilever flexible sheet pile walls in dry sand. The experimental conditions simulate those of plane strain. The deformations of the sand and of the walls are measured by an X-ray technique which also allows observation of the rupture surfaces in the sand. Data of the strains and displacements in the soil are reported for tests on loose and dense sand with rough and smooth walls of different flexibilities. A simple analytical method is given which links the deformations in the sand with deflexions of the wall and it is found to give good predictions of the settlements and other observed behaviour. La communication analyse les resultats d'une etude experimentale, en laboratoire, sur les deformations pres des rideaux de palpanches simples encastres, dans du sable sec. Les conditions experimentales simulent celles des deformations planes. Les deformations du sable et des parois sont mesurees par une techniq...
TL;DR: In this paper, the authors consider the treatment of soil as an isotropic strain-hardening or strain-softening material, and different assumptions are discussed for the derviation of incrementa stress-strain relations.
Abstract: Plasticity concepts are set forth in a rather general manner for the treatment of soil as an isotropic strain-hardening or strain-softening material, and different assumptions are discussed for the derviation of incrementa stress-strain relations. Strain-softening flow laws violate Drucker's postulate, but it is shown how uniquencess can still be ensured by contraining the relative magnitude of the rate of strin softening with respect to the recoverable elastic energy of the material. The stability of the solutin is discuseed, and in order to illustrate the stability concepts, closed form solutions for the undrained expansion of a cylindrical cavity in a finite and infinite saturated medium are presented. Les concepts plastiques sont exposes de facon generale en vue du traitement du sol comme un materiau isotrope presentant des comportements de raffermissement aussi bien que de ramolissement. Differentes hypotheses por la derivation des lois incrementales contraintes-deformations elementaires sont discute...
TL;DR: In this paper, the problems of prediction of the reaction of real soils to intense impact are discussed and the difficulties enumerated, and idealized models are presented to illustrate the parts played by stress wave reaction and by inertia forces associated with elastoplastic void closure in determining the deceleration of a falling weight and the utilization of the impact energy.
Abstract: The problems of prediction of the reaction of real soils to intense impact are discussed and the difficulties enumerated. Idealized models are presented to illustrate the parts played by stress wave reaction and by inertia forces associated with elasto-plastic void closure in determining the deceleration of a falling weight and the utilization of the impact energy. The general behaviour of real soils to a specified impact is then reviewed by selecting more specific types of soil and discussing their expected behaviour in the light of the general principles embodied in the idealized models. Les problemes de prevision de la reaction des sols reels au contact d'un choc intense, sont discutes et les difficultes enumerees. Des modeles idealises sont presentes afin d'expliquer les roles joues par la reaction d'ondes de contrainte et des forces d'inertie associees a la fermeture de la cavite e’lasto-plastique dans la determination de la deceleration d'un poids tombant et l'utilisation de l'energie de choc. Le co...
TL;DR: In this paper, it is shown that these zones of undeformed soil, called boundary wedges, are formed either because of kinematic constraints imposed by the motion of the interface or as a result of limitations imposed by interface configuration.
Abstract: Earth pressure analyses which use a rigid-plastic Mohr-Coulomb soil model generally assume that all the soil within the rupture boundary is deforming and that the loading boundary stresses are fully mobilized The analysis presented here shows that neither of these conditions is always realized and that zones of dead soil develop within the rupture boundary which alter the rupture surface geometry and interface stress conditions It is shown that these zones of undeformed soil, called boundary wedges, are formed either because of kinematic constraints imposed by the motion of the interface or as a result of limitations imposed by interface configuration A systematic method for predicting both the formation of these boundary wedges and their influence on interface stress conditions is presented A calculation procedure, using dimensionless passive coefficients to supplement the charts of those coefficients already published, is set out The theory proposed incorporates into the basic Sokolovski solution t
TL;DR: In this paper, the effect of transverse isotropy on the surface settlement of a homogeneous elastic half-space resulting from both frictionless and adhesive axisymmetric surface loading applied over a circular area is considered.
Abstract: Consideration is given to the effect of transverse isotropy on the surface settlement of a homogeneous elastic half-space resulting from both frictionless and adhesive axisymmetric surface loading applied over a circular area. Particular emphasis is accorded to the sensitivity of the calculated settlements to the assumed values of the elastic constants. The finite element method is then used to analyse the problem of an elastic circular raft of finite flexibility in adhesive contact with a thick transversely isotropic elastic layer underlain by a rigid frictionless base. The layer is assumed to be either homogeneous (moduli constant with depth) or strongly heterogeneous (moduli increasing linearly with depth). Results are given for uniform and parabolic distributions of applied load, and for undrained and fully drained soil layers. On examine l'effet de l'isotropie transversale sur le tassement de la surface d’un demi-espace homogene elastique lors du chargement de surface axisymetrique sans ou avec frott...
TL;DR: In this article, the effects of anisotropy on the stress-strain characteristics of a sand and the influence of a comparatively simple form of three-dimensional testing apparatus on the measured stressstrain behaviour of samples were reported.
Abstract: Tests are reported concerning the effects of anisotropy on the stress-strain characteristics of a sand and the influence of a comparatively simple form of three-dimensional testing apparatus on the measured stress-strain behaviour of samples. The stress-strain characteristics in vertical triaxial compression tests on cylindrical samples of 3·9 in. diameter and 4·1 in. in height and on cuboidal samples 3·3 in. high, 3·0 in. long and 2·3 in. wide, with two 0·010 in. thick lubricated membranes at each end, were found to be identical for samples at a given initial porosity, independent of the sample shape. Vertical and horizontal plane strain and horizontal triaxial compression tests were conducted in the ISC apparatus developed by Green (1969, 1971). It was found that the use of undersized rigid platens affected the stress-strain characteristics in the direction of the undersized platens. Groups of horizontal triaxial compression and plane strain tests demon-strated that both loose and tamped dense samples w...
TL;DR: An extension of the analysis of undrained pressuremeter tests, which allows the complete undrained shear stress-shear strain curve to be derived directly from the observed relation between the applied pressure and the radial expansion of the membrane of the pressuremeter, is presented in this paper.
Abstract: An extension of the analysis of undrained pressuremeter tests, which allows the complete undrained shear stress-shear strain curve to be derived directly from the observed relation between the applied pressure and the radial expansion of the membrane of the pressuremeter, is presented. It takes account of volume change, thus facilitating pressuremeter tests in permeable soils such as sands, silts and silty clays. The likely consequences of applying the new analysis are assessed. /TRRL/
TL;DR: A telemetering differential piezometer was designed and constructed at the Norwegian Geotechnical Institute to measure a minimum differential pressure (pore-pressure referenced to hydrostatic pressure) of 34 kPa and a maximum pressure of 294 kPa in water depths of up to 500 m as discussed by the authors.
Abstract: A telemetering differential piezometer was designed and constructed at the Norwegian Geotechnical Institute to measure a minimum differential pressure (pore-pressure referenced to hydrostatic pressure) of 34 kPa and a maximum pressure of 294 kPa in water depths of up to 500 m. An emplacement system was built at the University of Illinois, One successful in situ test in the Wilkinson Basin, in a water depth of 274 m, yielded a maximum excess pore-pressure of 59 kPa after the probe was driven about 3·2 m into the silty-clay bottom. An excess pore-pressure of 9·8 kPa was measured 5–10 h after emplacement of the probe. Implications of excess pore-pressures cyclically generated by storm and internal wave loading of sea-floor soils is discussed. It is concluded that a better understanding of submarine slope stability through the use of the effective stress principle should now be possible by measuring pore-pressure in situ. Un telemetre/piezomtre differentiel fut projete et construit a l'institut Geotechnique N...
TL;DR: In this article, three groups of stress paths are described, all applied with constant mean normal stress to samples of isotropically consolidated kaolin, and the success with which two numerical models of soil behaviour (the so called Cam clay and microstructural models) are able to predict the experimentally observed behaviour for these more complicated conditions of stress.
Abstract: The Cambridge True Triaxial Apparatus permits samples of soil to be tested with independent variation of the three principal stresses. A feedback system, based on a small computer, has been attached to the apparatus and this enables any three-dimensional stress path that is desired to be followed accurately. Three groups of stress paths are described here, all applied with constant mean normal stress to samples of isotropically consolidated kaolin. These paths are used to examine the success with which two numerical models of soil behaviour (the so called Cam clay and microstructural models) are able to predict the experimentally observed behaviour for these more complicated conditions of stress. (Both models have previously been used with some success for axisymmetric conditions of stress and strain). The assessment of the success of the predictions will depend on the use for which the models are required. Neither model is very successful for stress paths in which the octahedral stress ratio decreases. F...
TL;DR: In this article, a site investigation carried out in connexion with the construction of the Ely-Ouse Essex water tunnel was carried out and a number of rotary core and open-nve samples of the Gault were obtained from depths varying from about 20 to 90 metres below ground level.
Abstract: During a site investigation carried out in connexion with the construction of the Ely-Ouse Essex water tunnel a number of rotary coreandopen-dnve samples of the Gault were obtained from depths varying from about 20 to 90 metres below ground level results of laboratory tests made on these samples are presented and are compared with similar tests made on block samples of the Gault taken subsequently during tunnelling operations The possibility that the borehole samples are not reasonably representative of the in situ clay, particularly in view of the great depth involved, is discussed in relation to various soil characteristics Because of the general scarcity of geotechnical data on the Gault some comparisons are made in this Paper between its properties and those of the better known London Clay Au cours d'une reconnaissance in situ, mise a execution a propos de la construction du tunnel d'eau Ely-Ouse en Essex, un nombre d‘echantillons du Gault en forme de carottes par sondage en rotation a ciel ouvert
TL;DR: In this article, a theory of the creep of a clay during shear is suggested which is supported by experime, and the following features are characteristic of soil behaviour: creep limit, static viscosity and moduli of mobilization and stabilization.
Abstract: A succession of soil structures is formed and destroyed during the creep of a clay during shear; they are characterized by a mutual rearrangement of contacts and by the forces acting at the contacts. Transition from one structure to the other proceeds in a jump-like way. The creep process consists of two phases: mobilization and rupture. In the mobilization phase the strain rate decreases directly with time; in the rupture phase it increases. Therefore the creep curves in the mobilization phase consist of logarithmic curves whilst, in the rupture phase, of parabolas. The following features are characteristic of soil behaviour: creep limit, static viscosity and moduli of mobilization and stabilization. These quantities are linearly related to the normal pressure. The strain rate at low and moderate shear stress levels decreases following the stabilization limit, whilst at high stress levels the process ends in rupture. A theory of the creep of a clay during shear is suggested which is supported by experime...