Showing papers in "Geotechnique in 1979"
Journal Article•
TL;DR: The distinct element method as mentioned in this paper is a numerical model capable of describing the mechanical behavior of assemblies of discs and spheres and is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the objects modelled particle by particle.
Abstract: The distinct element method is a numerical model capable of describing the mechanical behaviour of assemblies of discs and spheres. The method is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the particles modelled particle by particle. The main features of the distinct element method are described. The method is validated by comparing force vector plots obtained from the computer program BALL with the corresponding plots obtained from a photoelastic analysis. The photoelastic analysis used for the comparison is the one applied to an assembly of discs by De Josselin de Jong and Verruijt (1969). The force vector diagrams obtained numerically closely resemble those obtained photoelastically. It is concluded from this comparison that the distinct element method and the program BALL are valid tools for research into the behaviour of granular assemblies. La methode des elements distincts est un modele numerique capab...
12,554 citations
TL;DR: The distinct element method as mentioned in this paper is a numerical model capable of describing the mechanical behavior of assemblies of discs and spheres and is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the objects modelled particle by particle.
Abstract: The distinct element method is a numerical model capable of describing the mechanical behaviour of assemblies of discs and spheres. The method is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the particles modelled particle by particle. The main features of the distinct element method are described. The method is validated by comparing force vector plots obtained from the computer program BALL with the corresponding plots obtained from a photoelastic analysis. The photoelastic analysis used for the comparison is the one applied to an assembly of discs by De Josselin de Jong and Verruijt (1969). The force vector diagrams obtained numerically closely resemble those obtained photoelastically. It is concluded from this comparison that the distinct element method and the program BALL are valid tools for research into the behaviour of granular assemblies. La methode des elements distincts est un modele numerique capab...
12,472 citations
Abstract: The shortcomings of the curves normally used to describe the change of volume of a soil skeleton with variations in mean effective stress are discussed. The author proposes an alternative approach, without the use of void ratio, adopting specific volume. Expressions are derived to show that natural volumetric stresses and strains are linearly related. Some consequences of this new relationship are examined. The coefficient of volume compressibility is defined, and the theory of soil consolidation in an oedometer investigated. Predictions of pore water pressure and effective stress changes are better than those of the conventional linear theory. The cam clay soil model is modified to give a revised critical state line which is well supported by experimental evidence. Equations are derived which could provide a basis for a simplified presentation of state boundary surfaces. (TRRL)
521 citations
TL;DR: In this article, the authors reviewed available information concerning the field performance of dams during earthquakes and conclusions were drawn concerning the potential for earthquake-induced sliding for different types of construction materials and earthquake shaking intensities.
Abstract: The factors to be considered in the earthquake-resistant design of dams are discussed and defensive measures which may be taken to mitigate the effects of these factors are summarized. Available information concerning the field performance of dams during earthquakes is reviewed and conclusions are drawn concerning the potential for earthquake-induced sliding for different types of construction materials and earthquake shaking intensities. Finally, available methods for evaluating the stability and deformations of the slopes of a dam due to earthquake shaking are reviewed and their applicability illustrated. Conclusions are drawn concerning the significance of the type of soil used for construction and the possibility of delayed failure, after the earthquake ground motions have stopped, due to pore water pressure re-distribution within an embankment. Suggestions are made concerning the appropriate role of analytical procedures in the overall assessment of the seismic stability of dams in relation to the un...
425 citations
TL;DR: In this article, the effects of installing a driven pile on the strength of the soil were investigated using a work-hardening elasto-plastic soil model, which has the unique feature of allowing the strength to change as the water content changes, thus it is possible to calculate the new intrinsic soil strength at any stage during consolidation.
Abstract: 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...
409 citations
TL;DR: In this article, a method of analysis is presented which permits the settlement of a pile group under vertical load to be calculated with reasonable accuracy, without the expense of a full rigorous analysis.
Abstract: A method of analysis is presented which permits the settlement of a pile group under vertical load to be calculated with reasonable accuracy, without the expense of a full rigorous analysis The me
280 citations
TL;DR: In this paper, an anisotropic hardening model for soils was proposed, taking into account both isotropic hardening due to porosity changes and anisotropy effects induced by the initial consolidation process.
Abstract: This Paper extends the previous work (Mroz, Norris and Zienkiewicz, 1978a) where an anisotropic hardening model for soils was proposed, taking into account both isotropic hardening due to porosity changes and anisotropy effects induced by the initial consolidation process. The analysis is restricted to the case of triaxial state for which two principal stresses are equal. The incremental relations are derived and applied to study the drained and undrained material behaviour after isotropic and anisotropic K0 consolidation of clays. The material response under cyclic loading is also discussed. The predicted inelastic behaviour is compared with available experimental results for kaolin and Weald clays for which the material parameters are also identified. Further improvements of the model are indicated, Cette etude prolonge le travail anterieur (Mroz, 1978a) realise par Norris et Zienkiewicz dans lequel un modele anisotrope de durcissement pour sols etait propose, tenant compte du durcissement isotrope par ...
270 citations
TL;DR: In this paper, the authors discuss the mechanisms controlling the shear strength behavior of saturated kaolinite and montmorillonite clays from a detailed experimental program based on certain theoretical consid'rations.
Abstract: This Paper discusses the mechanisms controlling the shear strength behaviour of saturated kaolinite and montmorrillonite clays from a detailed experimental programme based on certain theoretical consid'rations. In the light of the modified effective stress concept, which takes into consideration the interparticle electrical attractive and repulsive forces, an attempt has been made to explain the behaviour of the clays. Eight organic fluids of different dielectric properties, air and water have been used as pore media to vary the inter-particle forces in the conventional box shear apparatus. The experimental results are in qualitative conformity with the modified effective stress concept and the soil strength is significantly influenced by the dielectric properties of the pore discussed in detail. Cet article traite des mecanismes regissant la resistance au cisaillement des argiles a kaolinite et montmorillonite saturees, a partir d'un programme experimental detaille base sur certaines considerations theor...
118 citations
TL;DR: In this article, the authors show that the strain energy can be used with advantage to define the limit state surface of clays from eastern Canada using three different tests on four undisturbed, overconsolidated clays.
Abstract: Triaxial, stress controlled, drained tests on four undisturbed, overconsolidated clays from eastern Canada show that the strain energy can be used with advantage to define the limit state surface o...
100 citations
TL;DR: In this article, a model for the stress-strain behavior of London Clay has been developed for use in a nonlinear finite element program, which can be used to compute the results of both laboratory and in situ tests.
Abstract: A computer model for the stress–strain behaviour of London Clay has been developed for use in a nonlinear finite element program. The behaviour of London Clay is divided into three ranges of strain: elastic, intermediate and plastic. In the elastic range strains are very small and the material is very stiff. The intermediate range represents the larger strain behaviour normally observed in laboratory tests; it is not truly elastic, but in many respects exhibits aniso-tropic elastic behaviour. As yield is approached, plastic behaviour can accompany the intermediate phase and is governed by a flow rule and a state boundary curve. In all phases the stiffnesses of the model increase with mean normal effective stress. It is shown that the model can be used to compute the results of both laboratory and in situ tests. The movements around two excavations in London Clay, including the New Palace Yard Underground Car Park, have also been computed retrospectively with considerable success. Un modele informatique de...
97 citations
TL;DR: In this article, a series of tests made on instrumented tubular steel piles in the field to examine the mechanism of load transfer from piles in stiff clay were described, and during installation detailed measurements were made of the vertical movements of the soil near the ground surface and at mid-pile level and of the distribution of load in the pile shafts.
Abstract: This Paper describes a series of tests made on instrumented tubular steel piles in the field to examine the mechanism of load transfer from piles in stiff clay. The piles were jacked into the ground and during installation detailed measurements were made of the vertical movements of the soil near the ground surface and at mid-pile level and of the distribution of load in the pile shafts. During installation of the first pile, loading tests were made at a range of penetrations so that the variation of the soil properties with depth and the effect of pile length on the settlements at corresponding working loads could be examined. The movements of piles already installed and changes in their residual shaft loading were observed as subsequent piles were driven. The main part of the study was a detailed examination of the soil displacements around and beneath a pile under working load conditions using new instrumentation developed for this purpose. By relating the soil displacements to the pile settlement and ...
TL;DR: In this paper, the strength of a face-centred cubic array of uniform rigid spheres is analyzed for three degrees of rotational freedom and the complete stress range σ3 ≤ σ2 ≤ ρ1 is considered, and the strength is found to be dependent on the relative orientation of the applied stresses.
Abstract: The general solution for the strength of a face-centred cubic array of uniform rigid spheres is presented. The applied stress system is allowed three degrees of rotational freedom and the complete stress range σ3 ≤ σ2 ≤ σ1 is considered. The strength is found to be dependent on the relative orientation of the applied stresses and the optimum solutions for various degrees of rotational freedom are identified. The solution for the case in which the stress and strain–increment tensors are coaxial extends the previous work of Dantu (1961), Rowe (1962) and Leussink and Wittke (1963) to generahzed stress conditions. The optimum solution for freedom to rotate about the intermediate principal strain–increment direction is identical to Parkin's (1965) solution except that the angles of deviation between the stress and strain–increment directions are correctly prescribed. None of the remaining solutions contained in the analysis have been presented before. The analysis shows that a variety of failure envelopes are ...
TL;DR: In this paper, the effect of angularity on interparticle friction has been investigated and a physical interpretation of Horne's theoretical prediction on maximum dilatancy rate is proposed.
Abstract: The definition of interparticle friction—in Rowe's and Horne's terms—allows us to research effects of petrographic characteristics of sand grains on their mechanical properties in mass, independently of the effect of packing parameters. It is known that this interparticle friction depends on the mineral composition of particles and on the state of their surface chemistry. Quantitative characterization of grain shape allows us to point out the effect of angularity on interparticle friction, for which a physical interpretation is proposed. Some tests results show that Horne's theoretical prediction on maximum dilatancy rate is not verified for highly rounded calcareous particles, thus demonstrating that the sphericity of particles has an effect on the types of assembly strain. La notion de frottement intergranulaire—au sense de Rowe et Horne—permet de rechercher l'effet des caracteres petrographiques des grains de sable sur leurs proprietes mecaniques d'ensemble independamment des caracteristiques de l'asse...
TL;DR: In this article, a simple analytical method which relates induced lateral earth pressures to the effective line loading imposed by a compaction plant is presented, and a comparison is made between the factors of safety assumed to exist in conventional retaining wall design and those resulting when compaction effects are taken into account.
Abstract: It is widely recognized that compaction of fill behind earth retaining structures can induce lateral earth pressures that vary considerably in magnitude and distribution from those predicted using classical earth pressure theory. This Paper presents a simple analytical method which relates induced lateral earth pressures to the effective line loading imposed by compaction plant. Although by no means definitive, the method proposed permits a meaningful assessment of compactioninduced lateral pressures without recourse to complicated mathematical models. Predicted pressures are compared with observed pressures from two case histories, in a third case history the performance of a retaining wall is compared with predictions made using classical theory and the proposed method. A comparison is made between the factors of safety assumed to exist in conventional retaining wall design and those resulting when compaction effects are taken into account. II est couramment admis que le compactage du remblai derriere l...
TL;DR: A local hydraulic uplif failure has been observed in the base of a 29m brick pit excavation in Oxford Clay as mentioned in this paper, preceded by at least a 150mm rise of the pit base as water accumulated under pressure beneath impermeable clay surface layers.
Abstract: A local hydraulic uplif failure has been observed in the base of a 29m deeep, large brick pit excavation in Oxford Clay. The failure was preceded by at least a 150mm rise of the pit base as water accumulated under pressure beneath impermeable clay surface layers. Hydrogeological studies have indicated that the source of water was a thin underlying bed of limestone. Rupture of the capping clay finally resulted in the rapid release of about 7000m3 of water which flooded part of the pit and caused an immediate settlement of up to 100mm of the pit base. Precise survey observations begun in the year before the failure have provided a unique record of the rate and extent of the uplift and settlement movements. Une rupture locale par soulevement du a une sous pression hydraulique a ete observee a la base d'un grand puits d'excavation de brique de 29m de profondeur dans l'argile d'oxford. La rupture fut precedee par un soulevement d'au moins 150mm de la base du puits a mesure que la sous pression augmentait en de...
TL;DR: In this paper, Young's moduli are compared with the results of finite element back analysis of the settlements observed under a large scale tank test and shown to be directly proportional to depth.
Abstract: Seismic velocities are calculated as a function of depth for chalk at Mundford and dynamic Young's Moduli, which increase with depth, are found from these velocities. The moduli are compared with the results of finite element back analysis of the settlements observed under a large scale tank test and shown to be directly proportional. This factor is thought to be accounted for by a viscoelastic model. Le calcul des vitesses sismiques de la craie de Mundford est effecte en fonction de la profondeur et les modules dynamiques de Young, qui augmentent avec la profondeur, sont determines a partir de ces vitesses. Les modules sont compares aux resultats d'une analyse inverse a elements finis des tassements observes lors d'un essai en bassin a grande echelle et les resultats montrent qu'ils sont directement proportionnels. Le fait que les modules sont fonction du temps expliquerait ce facteur.
TL;DR: In this paper, the authors discuss the effects of cyclic loading and suggest the such effects cause some of the most pressing uncertainties in geotechnical engineering today, reflecting the general concern about the consequences of earthquakes and the safety of offshore structures.
Abstract: The authors discuss the effects of cyclic loading and suggest the such effects cause some of the most pressing uncertainties in geotechnical engineering today, reflecting the general concern about the consequences of earthquakes and the safety of offshore structures. Reference is made to the problems associated with the hollow cylinder apparatus used to resolve such uncertainties, and a new apparatus which completely controls the principal stress directions applied to a uniformly stressed soil sample sheared in plane strain. This technical note reports on the use of this new apparatus, known as a "directional shear cell" in which drained tests were made on dry dense leighton buzzard sand with the effective stress ratio held as nearly constant as possible throughout. The apparatus is described by reference to a cross-sectional drawing of the cell, and information provided on preparation and testing. A summary of the data obtained is presented and discussed, and stress variations obtained during a test cycle illustrated and described. The authors suggest that the data from this test series are unusual in yielding a single result of great potential significance: the large reduction in strength induced in a drained dense sand by cyclic continuous rotation of the major principal stress direction. It is suggested that there is a need for independent confirmation of such a result bearing in mind that it was obtained from tests made in a new apparatus. /TRRL/
TL;DR: In this paper, an experimental study of the inward radial drainage of remoulded kaolinete clay to a central model sand drain has been undertaken primarily to assess the effects of various methods of installation and spacing on the consolidation characteristics of the soil.
Abstract: This Paper is concerned with an experimental study of the inward radial drainage of remoulded kaolinete clay to a central model sand drain and has been undertaken primarily to assess the effects of the various methods of installation and spacing on the consolidation characteristics of the soil. An experimental programme has been designed and implemented using three sizes of Rowe consolidation cells (76, 152 and 254 mm dia.). Geometrical models of various methods of forming the drains were used for the three sample sizes consolidated under three levels of loading. A development incorporating the concept of non-circular cross-section for the drain former has been similarly assessed. Vertical flow consolidation tests were also conducted to compare the results with those from the radial drainage. These were done to assess the reliability of the commonly used method of deployment of vertical flow consolidation coefficient in the sand drain design procedure. The results indicate that there are marked difference...
TL;DR: In this paper, a plough of the long-beam forestry plough was used to excavate an underwater trench 1·5 m deep for a pipeline shore crossing in the Canadian Arctic.
Abstract: An underwater trench 1·5 m deep was required for a pipeline shore crossing in the Canadian Arctic. At the site the sea bottom is soft mud, and the trench would be close to its limit of stability. It was decided to excavate the trench with a large plough, built to a new design which would avoid the difficulties that had been encountered with earlier trenching ploughs. The design uses the principle of the long-beam forestry plough, which gives accurate control of trench depth, and the mechanics of a plough of this type are described. Dimensional analysis was used to develop the similarity conditions that have to be obeyed in model tests of a plough in clay, and the results were used in an extensive programme of model testing, which checked the operation of the plough and was used to refine the design. The full-scale plough was then fabricated, tested in a river delta, and transported to the Arctic, where it successfully excavated the required trench. Une tranchee sousmarine, d'une profondeur de 1,50 m, etai...
TL;DR: In this article, the authors examined the axis-yrnmetric problem of a rigid circular foundation, resting on an isotropic elastic half-space which is subjected, simultaneously, to an external load and an internal anchor load.
Abstract: This Paper examines the axisyrnmetric problem of a rigid circular foundation, resting on an isotropic elastic half-space which is subjected, simultaneously, to an external load and an internal anchor load. The anchor load consists of constant, linear or parabolic distributions of Mindlin forces of finite length, located along the axis of symmetry. A Mindlin force is defined as a concentrated force which acts at an interior point of the half-space along the axis of symmetry. The solution for the rigid displacement experienced by the circular plate is obtained in an exact closed form. This particular problem is of interest in connection with the study of rock anchors and in the examination of in situ tests such as the cable method of in situ testing. Cet article examine en axisymetric le cas d'une fondation circulaire rigide reposant sur un semi-espace elastique isotrope, soumise simultanement a un effort externe et a un effort d'ancrage interne. L'effort d'ancrage se compose des forces de Mindlin de longue...
TL;DR: A 2.74m diameter shield driven tunnel at an axis depth of 5m in a soft organic silty clay with a high moisture content known locally as Belfast sleech was measured in this paper.
Abstract: Surface and subsurface ground movements and changes in piezometric level were measured around a 2·74m diameter shield driven tunnel at an axis depth of 5m in a soft organic silty clay with a high moisture content known locally as Belfast sleech. Observations were obtained in a plane normal to the tunnel centre line during tunnel construction, and following removal of the stabilizing air pressure 25 days after construction. Results show a two-stage settlement process. During construction deformation was rapid and typical of empirical patterns associated with constant volume undrained ‘ground loss’ at the face and shield. Following removal of the air pressure, deformation patterns and reduced piezometric levels suggested compression of the silty clay, caused by drainage of groundwater into the tunnel, and similar to primary consolidation. Des mouvements de sol de surface et de subsurface et des variations de niveau piezometrique furent mesures autour d'une tole protectrice d'un tunnel perce, de 2·74 m de di...
TL;DR: In this article, a multi-blade cable plough with index specific cutting resistance was developed for use in the Japan-China submarine signal cable project, which has a distance of 850km.
Abstract: A submarine cable plough with multiple blades was developed for use in the Japan–China submarine signal cable project which has a distance of 850km. In developing and designing the equipment, an extensive series of experiments were carried out starting from fundamental investigations on the performance of a single blade to prototype tests. In the analysis of the performance of the multi–blade cable plough, a primary role is played by a newly proposed index specific cutting resistance which represents particular conditions of the material on the sea floor and is obtained from a simple in situ test. The performance of the cable installation was observed through the whole distance of cable laying and there was reasonable agreement between the measured and predicted drag forces. Une machine a lames multiples destinee a enterrer un câble sous-marin a ete utilisee pour le projet du câble de transmission sous-marin reliant le Japon a la Chine sur une distance de 850km. En meme temps que la mise en oeuvre et l'et...
TL;DR: In this paper, a new model is presented for soft clays under undrained loading, which takes into account the dependence of both strength and deformability on stress history during consolidation of the clay.
Abstract: A new model is presented for soft clays under undrained loading. The model takes into account the dependence of both strength and deformability on stress history during consolidation of the clay. This stress history causes non-homogeneity with depth and anisotropic behaviour. The model includes a new failure condition in terms of total stresses. Parameters defining the proposed rmodel are of two kinds: intrinsic shear strength (based on Hvorslev's parameters), and stress history, namely, consolidation and overconsolidation pressures and at-rest earth pressure coefficient. The validity of the model is checked against different test results previously reported, covering different stress conditions (simple shear and unconfined compression tests with variable orientation). Finally, a finite element model has been developed, based cn a hybrid method in displacements and stresses, which incorporates the proposed stress-strain-strength model for the clay. The case of a footing on a clay stratum over a rigid base...
Journal Article•
TL;DR: In this paper, an elastic model of the problem was analyzed and an approach was suggested for estimating the risk of pipe fracture by comparing the variation of maximum bending moment obtained for the continuous pipeline with that obtained for a regularly jointed pipeline allowed to articulate at the joints.
Abstract: The authors refer to a method which was proposed by them in 1977 for estimating the horizontal movement of a long shallow buried continuous pipeline due to the nearby excavation and backfilling of a long deep trench parallel to the pipeline. An elastic model of the problem was analysed and an approach was suggested for estimating the risk of pipe fracture. For cases of both short trenches and long trenches the present note compares the variation of maximum bending moment obtained for the continuous pipeline with that obtained for a regularly jointed pipeline allowed to articulate at the joints. It was found that for a pipeline buried in laterally deforming soil, the presence of articulating joints may increase the bending strains above those induced in an equivalent continuous pipeline. Under some conditions the bending moments could be increased by "absolute possible" maximum values of up to 36.5 percent for a long trench and up to 21 percent for a short trench. The actual maximum depends on the distance between the joint and the end of the excavation. /TRRL/