Showing papers in "Geotechnique in 1984"
TL;DR: In this article, an exact calculation of the load on such a cylinder is presented, where the load is non-dimensionalized with respect to the soil strength and the diameter of the pile.
Abstract: In the analysis of the undrained loading of laterally loaded piles an important quantity is the ultimate lateral resistance at depth to purely horizontal movement. If the soil is modelled as a perfectly plastic cohesive material then the calculation of this quantity reduces to a plane strain problem in plasticity theory, in which the load is calculated on a long cylinder which moves laterally through an infinite medium. An exact calculation of the load on such a cylinder is presented. If this load is non-dimensionalized with respect to the soil strength and the diameter of the pile, it is found that the load factor varies between for a perfectly smooth pile and for a perfectly rough pile. This result is discussed in the context of previous calculations for the lateral load capacity of piles and is compared with approximate calculations using cavity expansion theory and a wedge failure near the soil surface. La resistance laterale limite en profondeur au seul mouvement horizontal represente un parametre im...
561 citations
TL;DR: In this paper, the results obtained from different tests (triaxial, plane strain, direct simple shear, pressuremeter and vane) are compared by expressing them in terms of the undrained strength ratio su/σv0′ as a function of the friction angle φ.
Abstract: The purposes of in situ testing are set out, and the difficulties of the interpretation of the observations are emphasized. These difficulties are due to the complex behaviour of soils together with the lack of control and of choice of the boundary conditions in any field test. One notable exception is the pressuremeter test, from which soil properties can be derived directly without recourse to empirical correlations. The discussion is concentrated on the measurement of undrained shear strength. The results obtained from different tests (triaxial, plane strain, direct simple shear, pressuremeter and vane) are compared by expressing them in terms of the undrained strength ratio su/σv0′ as a function of the friction angle φ. Special attention is paid to tests in which the principal axes of stress and of strain increment are free to rotate. In such tests, uncertainty exists regarding the definition of failure and the planes of maximum stress obliquity. To derive these functions Matsuoka's failure criterion ...
512 citations
TL;DR: In this article, a simple technique for accurately measuring the mean local axial strains of triaxial samples over a central gauge length is described, which makes use of an axial displacement gauge, which is a development of one devised by Burland & Symes (1982) which made use of electrolytic levels.
Abstract: This Paper describes a simple technique for accurately measuring the mean local axial strains of triaxial samples over a central gauge length. The technique makes use of an axial displacement gauge which is a development of one devised by Burland & Symes (1982) which makes use of electrolytic levels. The device can resolve to less than 1 μ.m over a range of 15 mm, is simple to mount on the specimen and is not damaged when the sample is taken to failure. The results of undrained triaxial tests are presented for a wide spectrum of soil types ranging from sands through intact, reconstituted and remoulded low plasticity till, undisturbed London clay to intact unweathered chalk. The test results show that conventional external measurements of displacement contain errors which are frequently so large that their use in the determination of soil stiffness at working levels of stress is invalid. The errors mainly result from tilting of the sample, bedding at the end platens and the effects of compliance in the app...
384 citations
TL;DR: In this article, the effects of principal stress rotation in a medium-loose sand, tested under undrained conditions, are described and then explained within a framework based on the concept of state boundary surfaces.
Abstract: This Paper describes an investigation carried out in a new hollow cylinder apparatus into anisotropy and the effects of principal stress rotation in a medium-loose sand, tested under undrained conditions. Principal stresses have been rotated at a constant shear stress during both monotonie and cyclic loading. The experimental observations are described and then explained within a framework based on the concept of state boundary surfaces. The over-riding importance of initial anisotropy in determining the response of the sand to rotations in principal stress directions is demonstrated. Pore pressures are shown to be generated by rotation of principal stress directions at constant shear stress and their accumulation during cyclic principal stress rotation can lead to failure. L'article presente une etude de l'anisotropie effectuee dans un nouvel appareil creux cylindrique et decrit les effets de la rotation de la contrainte principale dans un sable moyennement lâche teste dans des conditions non-drainees. L...
203 citations
TL;DR: In this paper, the ability of the 15-noded displacement based finite element to assess accurately collapse loads of soil structures is examined for high friction angles and non-associated flow rules.
Abstract: The ability of the 15-noded displacement based finite element to assess accurately collapse loads of soil structures is examined for high friction angles and non-associated flow rules. Solutions are presented for strip and circular footings, for the trap door problem and for the cone penetration test. The last two problems are introduced in order to demonstrate that the method can be used to generate realistic solutions for problems that cannot be solved analytically. The footing problems are treated in order to assess the accuracy and stability of the numerical scheme. The accuracy is shown to be very high, but stability problems occur when non-associated flow rules are applied. In soil mechanics, this constitutes a fundamental problem since this type of instability is of a physical nature rather than of a numerical nature. L'article examine dans le contexte de grands angles de frottement et de regles d'ecoulement non-associees l'utilite d'un systeme base, sur les elements finis sur le deplacement de 15 ...
188 citations
TL;DR: In this paper, the electrical resistivity characteristics of a clay-water electrolyte system were investigated over a range of consistency indices and at varying degrees of compaction for two different clays, a Cheshire clay and a London clay.
Abstract: This technical note describes work carried out on the electrical resistivity characteristics of a clay-water electrolyte system. The samples were tested over a range of consistency indices and at varying degrees of compaction. Resistivity/fractional volume of water relationships have been established for two different clays, a Cheshire clay and a London clay, over a practical range of moisture contents. A unique relationship exists between these parameters for each clay. The resistivity of a clay is a function of moisture content and degree of saturation. At a particular moisure content, an increase in the degree of saturation (or a decrease in the air-void ratio) will mean a decrease in resistivity. (TRRL)
186 citations
TL;DR: In this article, a series of laboratory flume experiments was conducted to investigate the flow behaviour of dry sand at high velocities, and the conclusion was negative: even the most rapid of the experiments indicated flow behaviour which is in conformity with the constant volume uniform Coulomb friction relationship as applicable to slow shearing.
Abstract: A series of laboratory flume experiments has been conducted to investigate the flow behaviour of dry sand at high velocities. The first incentive for this experimental programme was an attempt to explain the high mobility of apparently dry masses of rapidly moving broken rock during rock avalanches (sturzstroms). Test velocities of over 5 m/s and most other parameters of the tests were found to be dimensionally similar to those for a typical rock avalanche. Yet, the conclusion was negative: even the most rapid of the experiments indicated flow behaviour which is in conformity with the constant volume uniform Coulomb friction relationship as applicable to slow shearing. This conclusion was confirmed independently both by direct measurements of base friction and mean density of the flows and by detailed observations of flow uniformity, acceleration and velocity profiles. The surprising mobility of st¨rzstroms therefore requires a different explanation. Une serie de tests a canaux a ete entreprise dans le...
140 citations
TL;DR: In this article, a ring shear was used on sand materials to show whether there is a change in the behaviour of these materials at high shearing rates and normal stresses, which is relevant to the problem of the mobility of large rock avalanches (sturzstroms).
Abstract: Ring shear tests on sand materials have been carried out to show whether there is a change in the behaviour of these materials at high shearing rates and normal stresses. This question is relevant to the problem of the mobility of large rock avalanches (sturzstroms), but is also of more general academic interest. A ring shear apparatus of unusual, although simple, design has been constructed, capable of achieving circumferential velocities of 2 m/s at normal stresses of up to 200 kPa. Tests were carried out on two types of coarse sand, wet or dry, sand-rock flour mixtures and polystyrene beads. Perfect frictional behaviour was observed in all the tests, uninfluenced by either velocity or normal stress over the entire range of these variables. Change in frictional behaviour due to high rate of shearing therefore cannot be used to explain the high observed mobility of sturzstroms. Des essais de cisaillement circulaire par torsion ont ete effectes afin de decouvrir si un changement ait lieu dans le comportem...
124 citations
TL;DR: In this paper, the Atterberg limits and activity of remoulded clays were investigated and correlations were developed which relate the compressibility, undrained shear strength, and permeability.
Abstract: Correlations have been developed which relate the compressibility, undrained shear strength, and permeability of remoulded clays to their Atterberg limits and activity. The relationships can be used to model a hydraulic fill, such as fine-grained dredged material or mine tailings, prior to deposition. They can also be used to estimate the engineering properties of normally consolidated natural clay, such as marine sediments. The correlations cover a wide range of plasticity index and liquidity index for a wide variety of clays. It was found that the activity plays a major role in the compressibility and undrained shear strength, and is thus also related to the sensitivity of clays. The activity apparently does not affect the permeability, but other factors remain to be investigated. Because compressibility, undrained shear strength, and permeability are interrelated, it can be concluded that if one is known, then the other two can be derived. Hence, these three engineering properties are seen as different...
119 citations
TL;DR: In this paper, the results from an extensive experimental study of the stress-strain behavior of dry sand in triaxial compression tests are presented, with emphasis on sources of error such as end restraint, bifurcation and imperfection sensitivity.
Abstract: In this Paper the results from an extensive experimental study of the stress-strain behaviour of dry sand in triaxial compression tests are presented. The experiments were performed in a new triaxial apparatus for large specimens. Emphasis is given to sources of error such as end restraint, bifurcation and imperfection sensitivity. The behaviour at small and large strains is presented and the rigid granular model of sand, its practical significance and limitations are discussed. Dans cet article on presente les resultats d'une recherche experimentale sur le comportement rheologique du sable sec en compression triaxiale. L'appareil triaxial est d'un genre nouveau qui contient de tres grands echantillons. Une etude detaillee des erreurs de mesures dues au frottement des plaques, a la bifurcation et a l'influence des imperfections est faite. Le comportement rheologique est presente pour de petites et grandes deformations; le modele du sable avec grains rigides, sa signification pratique et ses limites seront...
104 citations
TL;DR: In this paper, the influence of type of construction and initial stress in the soil on the behaviour of single propped retaining walls is investigated and the results of the investigation indicate that for excavated walls in soils with a high initial K 0 value prop forces and wall bending moments greatly exceed those predicted by current design methods.
Abstract: The design of propped retaining walls is currently based on approximate limit equilibrium calculations. A factor of safety is used to ensure adequate stability and to restrict soil and wall movements to acceptable levels. No distinction is made for the type of construction, whether excavated or backfilled, or of the stress state in the soil prior to construction. In this Paper the finite element method is employed to investigate the influence of type of construction and of initial stress in the soil on the behaviour of single propped retaining walls. An elasto-plastic constitutive law is used to model the soil behaviour and a rigid prop is assumed to act at the top of the wall. The results of the investigation indicate that for excavated walls in soils with a high initial K0 value prop forces and wall bending moments greatly exceed those predicted by current design methods. In addition large soil and wall movements are experienced even at shallow depths of excavation. The behaviour is dominated by the ver...
TL;DR: In this article, SEM photographs were obtained of the thixotropic soil microstructure during deformation of samples in a rotary viscometer with and without vibration, and the new data obtained clarify the mechanism of Thixotropic phenomena.
Abstract: Thixotropic phenomena in clay soils are accompanied by microstructural changes. The nature of these changes is unclear because of the short duration of the thixotropic processes and the difficulties involved in preparing a specimen at certain stages. However, these technological problems were overcome and SEM photographs were obtained of the thixotropic soil microstructure during deformation of samples in a rotary viscometer with and without vibration. The new data obtained clarify the mechanism of thixotropic phenomena. Soil microstructure was not ruptured by vibration during the shear process. On the contrary, it became more homogeneous over the entire volume and at the same time this induced a decrease in strengthin the system due to a reduction in cohesion at contacts. Disruption of some structural bonds is followed by their rapid restoration—the overall microstructure remaining intact. As a result, in all the samples studied the shear zone disappears. In kaolinite clay and coarser dispersed soils (si...
TL;DR: In this article, the theoretical bearing capacity of a series of parallel footings has been compared with laboratory tests on three parallel surface footings at various spacings on two different sands.
Abstract: Closely–spaced footings may be encountered on cohesionless soils in the form of grillage foundations and railway ties. Close spacing is known to permit higher loads than can be carried by similar isolated footings. This effect is due to interference between failure zones in the sand, and may increase the capacity by 150% when o = 35° and the centreline separation of the footings is approximately twice the footing width B. The method of stress characteristics has been used to calculate the theoretical bearing capacity of a series of parallel footings, and these have been compared with laboratory tests on three parallel surface footings at various spacings on two different sands. The testing programme also investigated the effects of footing roughness and load distribution. When interference occurs, pre-failure settlements become larger, and post-failure behaviour more ductile. The theoretical solutions show similar trends to the model tests, but suggest that interference stops at rather smaller spacings. D...
TL;DR: In this paper, a stress transfer approach at the interface between a single pile and a consolidating soil is proposed, where the non-linear, plastic character of the shear stress acting on the pile shaft and the adequate modelling of unloading and cyclic behaviour are properly incorporated through a "shooting" solution procedure of the equilibrium equations.
Abstract: In order to describe the interaction between a single pile and a consolidating soil a stress transfer approach at the interface is proposed. The non-linear, plastic character of the shear stress acting on the pile shaft and the adequate modelling of unloading and cyclic behaviour are properly incorporated through a ‘shooting’ solution procedure of the equilibrium equations. The whole problem is formulated in dimensionless terms both for external uniform loading conditions and for changes in piezometric levels. The formulation and the computational procedure developed are fairly general and may accommodate arbitrary layering and complicated loading sequences. In many practical situations the whole length of the shaft-soil interface has reached a limiting shear stress state except for a narrow zone around the neutral point. It is then possible to derive analytical solutions for the main design parameters. Their usefulness has been checked through several well-documented case records. L'article propose de pr...
TL;DR: Extensive instrumentation has been installed at Bell Common Tunnel to monitor the performance of a propped embedded retaining wall and the behaviour of the stiff clay in which it has been constructed.
Abstract: Extensive instrumentation has been installed at Bell Common Tunnel to monitor the performance of a propped embedded retaining wall and the behaviour of the stiff clay in which it has been constructed Earth and porewater pressures, ground and wall movements, and roof loading have been monitored during the construction period The deformations and stresses measured at each stage of construction are presented and the performance of the wall is discussed Un systeme important d'instrumentations a ete installe au tunnel de Bell Common pour controler le comportement d'un mur de soutenement encastre et celui de l'argile raide dans laquelle il a ete construit Pendant la periode de construction on a controle les pressions du sol et de l'eau interstitielle, les mouvements du sol et du mur et le chargement du mur L'article presente les deformations et les contraintes mesurees a chaque etape de la construction et analyse le comportement du mur
TL;DR: In this article, the authors developed a theory which relates in situ stress in level ground to weathering modelled as a weakening process, and the loss of stiffness during weakening is modelled by isotropic elastic theory with reducing elastic parameters, and loss of strength by a Coulomb failure criteria with reducing c′ and o′.
Abstract: No theory exists which relates the formation of a residual soil to the in situ stresses which develop in it. A theory is developed in this Paper which relates in situ stress in level ground to weathering modelled as a weakening process. The loss of stiffness during weakening is modelled by isotropic elastic theory with reducing elastic parameters, and loss of strength by a Coulomb failure criteria with reducing c′ and o′. A small amount of weakening causes in situ horizontal stress to approach a limiting value set by the value of Poisson's ratio assumed. Low horizontal stresses are thus predicted. The solution is extended to the infinite slope, in which even lower stresses are predicted. Internal shear failure, which may lead to densification of high porosity soils, is predicted due to loss of strength in the final stages of weathering. Porosity changes in weathered granite are found to be consistent with the predictions of the theory. Conditions in which the weathering theory would be inapplicable are di...
TL;DR: In this paper, the Mohr failure envelopes for compacted rockfills exhibit significant curvature particularly at low and medium stresses, and a computer program for circular arc slope stability analysis has been modified to accept these non-linear failure envelope, which has been introduced to facilitate the production of charts for the rapid assessment of rockfill slope stability.
Abstract: The Mohr failure envelopes for compacted rockfills exhibit significant curvature particularly at low and medium stresses. A computer program for circular arc slope stability analysis has been modified to accept these non-linear failure envelopes. A dimensionless stability number has been introduced to facilitate the production of charts for the rapid assessment of rock-fill slope stability. The effect of submergence on the stability of compacted rockfill slopes has been examined. Les courbes intrinseques des remblais rocheux compactes montrent une courbure signifiante surtout a basses et moyennes contraintes. Un programme d'ordinateur pour l'analyse de la stabilite des pentes en arc de cercle a ete modifie pour prendre encompte ces courbes intrinseques non-linearies. Un parameter de securite au renversement, sans dimensions a ete introduit pour faciliter la production d'abaques pour l'evaluation rapide de la stabilite des pentes de remblais rocheux. L'effet de la submersion sur la stabilite des pentes de ...
TL;DR: In this paper, the influence of stress relief caused by sampling on the undrained stress-strain behaviour of normally consolidated clays was investigated, and the results showed that samples suffered considerable loss in strength, increase in failure strain and produced appreciably different effective stress paths to failure.
Abstract: The Paper describes investigations into the influence of stress relief caused by sampling on the undrained stress-strain behaviour of normally consolidated clays. The study was conducted on two clays, kaolin and illite, manufactured in the laboratory from consolidated slurries. In situ behaviour was measured from clay specimens consolidated to in situ stresses in the triaxial cell and then tested undrained from these in situ stresses without unloading. Samples were prepared from consolidated blocks of material which were unloaded and stored for various times before being tested in undrained compression. Unloadings equivalent to appreciable sampling depths were simulated. The tests on both clays showed that, compared with the in situ soil, samples suffered considerable loss in strength, increase in failure strain and produced appreciably different effective stress paths to failure. This behaviour became more pronounced with increasing sample age and was accompanied by dissipation of residual negative pore ...
TL;DR: In this article, a technique for accurate and computationally efficient determination of one-dimensional contaminant migration of a single pollutant species in a non-homogeneous soil is presented, where the soil deposit may be split into layers with different hydraulic conductivities, dispersion coefficients, Sorption potential and seepage velocities.
Abstract: A technique for accurate and computationally efficient determination of one-dimensional contaminant migration of a single pollutant species in a non-homogeneous soil is presented. The soil deposit may be split into layers with different hydraulic conductivities, dispersion coefficients, Sorption potential and seepage velocities. The implications of non-homogeneity for design are illustrated by considering a two-layer system consisting of a compacted clay liner overlying a natural silty clay. The effect of liner properties and thickness on both the concentration profile and the peak concentration in an underlying aquifer are examined. It is shown that for a given landfill geometry the maximum concentration within the aquifer may be controlled by the choice of an appropriate clay liner. It is also shown that the volume of leachate has a significant influence on the choice of liner and the performance of the liner-natural soil contaminant system. L'article decrit une technique pour determiner de facon exacte...
TL;DR: In this paper, a series of field tests has been performed to investigate the effects of drilling disturbance on the values of the parameters derived from self-boring pressuremeter tests in sand.
Abstract: A series of field tests has been performed to investigate the effects of drilling disturbance on the values of the parameters derived from self-boring pressuremeter tests in sand. The approach adopted consisted of using different drilling shoe and cutter geometries, thereby deliberately causing varying amounts of drilling disturbance. The results show that the values of friction angle φ′ and dilation angle ν are sensitive to drilling disturbance. A procedure for correcting for the effects of drilling disturbance is proposed; however, it is demonstrated that the best results are obtained when drilling disturbance is kept to a minimum. Une serie d'essais in situ a ete executee pour examiner les effets du remaniement par le forage sur les valeurs des parametres derives des essais d'autoforage pressiometrique dans le sable. La methode adoptee comporte l'emploi de differentes geometries du sabot de forage et de l'outil de coupe, afin de provoquer expres des valeurs variees de remaniement par le forage. Les res...
TL;DR: In this article, two pseudo-steady problems of plane plastic flow of dilatant material are considered, and the distributions of densities within the deforming regions determined, characterized by dilation occurring exclusively across velocity discontinuity lines, that are treated in the analysis as shocks.
Abstract: In the Paper two pseudo-steady problems of plane plastic flow of dilatant material are considered, and the distributions of densities within the deforming regions determined. The kinematic solutions discussed are characterized by dilation occurring exclusively across velocity discontinuity lines, that are treated in the analysis as shocks. The first problem is that of flow of granular material through a hopper, and the kinematic solution suggested by Drescher, Cousens & Bransby (1978) is used. It is shown that in the radial flow zone the density distribution is non-uniform. As a second problem, the indentation of a wedge into a ponderable half-space is considered, and a kinematic solution similar to that proposed by Hodge (1950) is adopted. It is found that regions with different density exist. An upper limit load for the process of wedge indentation is determined, and the solution for weightless material is compared with that given by Shield (1953). A comparison with some of the experimental results obta...
TL;DR: In this paper, a solution for the stability of slopes in purely cohesive soils exhibiting a linear variation in shear strength with depth is presented; the strength at the surface is assumed to be greater than zero.
Abstract: The Paper presents a solution for the stability of slopes in purely cohesive soils exhibiting a linear variation in shear strength with depth; the strength at the surface is assumed to be greater than zero. The effect of seismicity is included in a quasi-static analysis. It is assumed that the potential failure surface is a circular arc. Taylor's charts and that provided by Gibson & Morgenstern can be derived from this Paper with the incorporation of appropriate assumptions. A series of plots are provided that are of use in the assessment of the stability of slopes in soils whose strength is constant with depth, and/or whose strength varies linearly with depth. Cet article fournit une solution pour la stabilite des pentes dans des terrains purement cohesifs ou la resistance a la rupture au cisaillement varie de facon lineaire avec la profondeur; on admet que la resistance a la surface soit positive et superieure a zero. Une analyse quasi-statique comprend aussi l'effet de la seismicite. On admet que la su...
TL;DR: A loading test on soft clay at Mastemyr, Norway, was carried out by the Norwegian Geotechnical Institute in 1968 to examine the build-up of displacements and pore pressures to failure.
Abstract: A loading test on soft clay at Mastemyr, Norway, was carried out by the Norwegian Geotechnical Institute in 1968 to examine the build-up of displacements and pore pressures to failure. Although the test was heavily instrumented deductions from the measurements have not hitherto been published. The field observations of pore pressures and deformations are examined here for indications of the occurrence of yielding which is expected to be manifested in an increased rate of development of pore pressure and of strain with increase in loading. Information concerning the yielding of the clay was also obtained from the results of a programme of laboratory tests and this was used to produce a simple elastic-plastic model for the clay which could be used with various elastic analyses to study the manner in which yielding might be expected to develop in the clay under the loading. Factors which may influence the ability of simple models and the simple analyses to predict the development of yielding are discussed. U...
TL;DR: In this article, the authors presented dimensionless charts for estimating seepage quantity and exit gradients in problems of confined flow, based on the "method of fragments" (Pavlovsky, 1935; Harr, 1962).
Abstract: The Paper presents dimensionless charts for estimating seepage quantity and exit gradients in problems of confined flow. Based on the ‘method of fragments’ (Pavlovsky, 1935; Harr, 1962), the charts represent a simplified approach for obtaining the form factor Φ, which also allows for anisotropic soil permeability. The accuracy of the assumptions inherent in the method is assessed using finite elements. It is concluded that the four charts presented enable reliable estimates of flow rate and exit gradients to be made for a wide range of confined flow problems of practical interest. Cet article presente des graphiques sans dimensions pour 1'evaluation de la quantitt de percolation et des gradients de sortie pour les problemes d'ecoulement confine. Basees sur la methode des fragments (Pav- lovsky, 1935; Harr, 1962), ces graphiques representent une methode simplifiee pour obtenir le facteur de forms Φ, qui Gent compte de la permeabilite isotrope du terrain. L'exactitude des assomptions inherentes dans la meth...
TL;DR: In this article, the authors describe the initial design approach to the retaining walls and highlights the lack of guidance that exists for this type of construction and highlight the results of a study that was commissioned to assess the soil-structure interaction of the retaining wall at Bell Common together with a review of stability criteria.
Abstract: The M25 motorway forms part of the London orbital road and at two locations north of London (Holmesdale, Waltham Cross, and Bell Common, Epping) it is constructed in cut and cover tunnels for environmental reasons. The Bell Common Tunnel is underlain by London clay and the design of the embedded cantilever retaining walls revealed considerable uncertainties in the assessment of the bending moments. Moreover application of the stability requirements of the code of practice (CP2) gave rise to excessive wall penetrations. Part I of the Paper describes the initial design approach to the retaining walls and highlights the lack of guidance that exists for this type of construction. Part II describes the results of a study that was commissioned to assess the soil-structure interaction of the retaining walls at Bell Common together with a review of stability criteria. The decisions leading to the final design are then described. L'autoroute M25 fait partie de la rocade peripherique de Londres. Pour des raisons d'...
TL;DR: In this article, the authors present a survey of the role of geotechnical parameters in the excavation of sand below water level and their estimation by field tests, showing that soil mechanics parameters play a dominant part in many dredging processes.
Abstract: For a long time the art of dredging was based on empiricism. In recent decades more fundamental research has been performed, which has demonstrated that soil mechanics parameters play a dominant part in many dredging processes. Some research results are presented in this Paper, referring especially to processes for the excavation of sand below water level. Attention is paid to each of the geotechnical parameters acting in these processes and also to their estimation by field tests. Pour longtemps l'empirisme a domine le metier de dragage. Mais depuis quelques dizaines d'annees la recherche plus fondamentale contribue a la connaissance du metier de maniere a montrer le role dominant des parametres geotechniques. Quelques resultats de recherche sont presentes ici, notamment les recherches executees sur le deblayage du sable sous eau. Les parametres importants sont decrits et discutes. En outre leur determination in-situ est consideree.
TL;DR: A preliminary assessment of the results obtained from a comprehensive field instrumentation and monitoring scheme of a deep basement in London clay, initiated in 1981 and expected to continue until at least 1987 and probably beyond, is presented in this article.
Abstract: A preliminary assessment of the results obtained from a comprehensive field instrumentation and monitoring scheme of a deep basement in London clay, initiated in 1981 and expected to continue until at least 1987 and probably beyond, is presented. The aspect of particular interest is the performance of the 18 m deep perimeter diaphragm wall and the associated temporary works during construction of the basement. Details of the recorded wall movements, strut forces and strains developed within the wall are given together with observations of water pressures in the ground behind the wall. In addition the results of line and level surveys of the wall and the surrounding area are presented. Soils information extracted from the original site investigation report, together with results obtained from samples and in situ tests conducted during the installation of a deep borehole extensometer, are given. A comparison is made with the original design predictions of wall and ground movements, bending moments and strut...
TL;DR: In this paper, the M26 motorway passes under an existing road in a cutting with a maximum depth of approximately 8 m, and it was necessary to construct retaining walls to limit both the landtake and the ground strains experienced by nearby buildings, including a church.
Abstract: Some sections of the M25 motorway and the M26 motorway were constructed almost entirely on the Gault clay outcrop which is relatively sparsely inhabited. Hence recourse could generally be made to conventional cutting and embankment construction. However, at Dunton Green in Kent, where the M26 motorway passes under an existing road in a cutting with a maximum depth of approximately 8 m, it was necessary to construct retaining walls to limit both the landtake and the ground strains experienced by nearby buildings, including a church. Gault clay is a heavily overconsolidated clay, similar to London clay, but with more extreme properties. In particular it is notorious for high shrinkage/swelling movements with changes in moisture content. Also the properties of the near-surface layers of the Gault clay in Kent have been significantly affected by cryoturbation and solifluxion during periglacial conditions. This Paper describes the design of these retaining walls which were constructed between 1978 and 1980 usi...