Showing papers in "Geotechnique in 1982"
TL;DR: In this paper, the authors describe a theoretical investigation into the behavior of anchor plates in sand, considering the effects of anchor embedment, friction angle, dilatancy, initial stress and initial stress on the anchor.
Abstract: This Paper describes a theoretical investigation into the behaviour of anchor plates in sand. Consideration is given to the effects of anchor embedment, friction angle, dilatancy, initial stress st...
355 citations
TL;DR: In this paper, the undrained behavior of anchor plates with a vertical or horizontal axis, resting in a saturated clay, is examined and theoretical consideration is given to the effects of anchor embedment, layer by layer.
Abstract: The undrained behaviour of anchor plates with a vertical or horizontal axis, resting in a saturated clay, is examined. Theoretical consideration is given to the effects of anchor embedment, layer d...
219 citations
TL;DR: In this paper, finite elements in conjunction with elasto-plastic theory can give excellent collapse load predictions for footings resting on c-φ soils, and the problem is approached by consider...
Abstract: The Paper shows how finite elements, in conjunction with elasto-plastic theory, can give excellent collapse load predictions for footings resting on c-φ soils. The problem is approached by consider...
213 citations
TL;DR: The compressibility of pure clays under external load depends not only on the negative charges and crystallite morphology of clay minerals but also on the ion concentration, cation valency, dielectric properties of clays.
Abstract: The compressibility of pure clays under external load depends not only on the negative charges and crystallite morphology of clay minerals but also on the ion concentration, cation valency, dielect...
208 citations
TL;DR: Frictional heat generated within fluid-saturated landslide slip zones can create an increase in pore fluid pressure as discussed by the authors, which is enhanced by large values of friction coefficient, initial porosity and slide displacement, and by small values of slip zone thickness and compressibility.
Abstract: Frictional heat generated within fluid-saturated landslide slip zones can create an increase in pore fluid pressure. This rise in fluid pressure is enhanced by large values of friction coefficient, initial porosity and slide displacement, and by small values of slip zone thickness and compressibility. If maintained under conditions of fast slip, and small wall rock permeability and shear dilatancy, fluid pressure rise can induce rapid frictional strength loss during sliding. Moderate sliding can thereby be converted under certain conditions into catastrophic descent. The rate of temperature rise within a slip zone diminishes as pore fluid pressures rise. Vaporization seems possible only under restricted conditions, and results suggest that large gas pockets are not generally produced. However, rock melting or dissociation may be relatively common under portions of large slides. Frictional heat-induced fluid pressure enhancement is proposed as a possible explanation for the problem of low kinetic friction ...
169 citations
TL;DR: In this article, a theoretical analysis of the fall cone test and a direct calculation of the undrained strength at the liquid limit of a clay is presented, showing that the single most important factor affecting liquid limit is cone roughness.
Abstract: The fall cone test is widely used as a method for determining the liquid limit of a clay. In the past it has been suggested that the liquid limit test is essentially a strength test, and empirical correlations have been made for the strength at the liquid limit. This Paper presents a theoretical analysis of the fall cone test and a direct calculation of the undrained strength at the liquid limit. The analysis also allows a critical examination of the tolerances specified for the liquid limit device; it is found that the single most important factor affecting liquid limit is cone roughness. Le test au cone a chute libre est largement employe pour determiner la limite de liquidite d'une argile. Dans le passe on a suppose que l'essai de la limite de liquidite est essentiellement un essai de resistance et des correlations ont ete etablies pour la resistance et la limite de liquidite. Cet article presente une analyse de l'essai au cone a chute fibre et un calcul direct de la resistance non-drainee a la limite ...
132 citations
TL;DR: In this paper, the use of electrolytic liquid levels as horizontal inclinometers is described for the measurement of local displacements and strains on laboratory soil samples, and a triaxial test apparatus for application in routine soil testing is presented.
Abstract: The use of electrolytic liquid levels as horizontal inclinometers is described for the measurement of local displacements and strains on laboratory soil samples. The simplicity, accuracy and low-cost of electrolytic levels are said to make such units useful in transducer applications. The liquid level consists of an electrolyte sealed in a glass capsule with three co-planar electrodes partially immersed in the electrolyte. Resistance between the electrodes vary as the capsule is tilted. Inclinometer apparatus described uses an electrolevel for measurement of local torsional strains in soil and it is shown how such a vertical deflection gauge can be used in a triaxial test apparatus for application in routine soil testing. (Author/TRRL)
126 citations
TL;DR: In this paper, the influence of the deformation mechanism on the softening characteristics of triaxial tests on granular material was studied and the solutions for the apparent angle of internal friction were obtained by the approximate method of slices and are expressed in terms of collocational coefficients, defined for an appropriate choice of collocal points of the slices.
Abstract: The Paper presents a study of the influence of the deformation mechanism on the softening characteristics of triaxial tests on granular material. The material is treated locally as rigid-plastic with a linear Mohr-Coulomb yield condition. The solutions for the mobilized apparent angle of internal friction are obtained by the approximate method of slices and are expressed in terms of collocational coefficients, defined for an appropriate choice of collocational points of the slices. The determination of the collocational coefficients from the underlying flow rules and mechanism of deformation is presented. The solutions are used for the analysis of experimental records by Deman (1975). The main conclusions are that softening in the triaxial test is due mainly to geometric effects and that moderately slender specimens with non-lubricated end platens yield unsafe values of the friction angle and give an erroneous indication of the extent of material softening. Dans cet article est etudiee l'influence des mec...
102 citations
TL;DR: In this paper, the mobilization of shear stress along a rough pile shaft in normally consolidated clay is considered in terms of the effective stresses acting in the clay, and theoretical predictions of the stress changes which occur in the soil adjacent to the pile shaft on loading are presented and shown to be in good agreement with some experimental results.
Abstract: Most design procedures for estimating pile capacities are empirical in nature, and the mechanism of load transfer from a pile to the soil is not well understood. In this Paper the mobilization of shear stress along a rough pile shaft in normally consolidated clay is considered in terms of the effective stresses acting in the clay. Theoretical predictions of the stress changes which occur in the soil adjacent to the pile shaft on loading are presented and shown to be in good agreement with some experimental results. For drained loading conditions reductions in radial effective stress generally occur, and the peak mobilized angle of shaft friction is shown to be independent of initial soil stresses before pile loading. The validity of the theoretical model is shown and the loading behaviour, drained and undrained, of driven piles is examined. Comparison between these predictions and field data suggests that fabric disturbance caused by pile installation may seriously affect pile capacities. La plupart des m...
71 citations
TL;DR: In this paper, the suitability of a simple expression, containing the specific gravity of soil particles, relating the plasticity index and compression index for soils at their plastic and liquid limits is tested by comparing predicted values with measured values of the compression index.
Abstract: The suitability of a simple expression, containing the specific gravity of soil particles, relating the plasticity index and compression index for soils at their plastic and liquid limits is tested by comparing predicted values with measured values of the compression index. A survey of the available research indicated that generally good correlation was found. It is considered possible that the relation should also depend on clay minerology although good agreement with the expression has been obtained on a wide range of soils. It is concluded that the cone penetrometer test described in BS 1377(1975) is simple, and although results do not correspond exactly with those determined using other devices, the water content at which a 30 deg, 80gf cone penetrates 20mm provides a useful index property for soils. (Author/TRRL)
53 citations
TL;DR: A technique for installing a piezometer probe on samples down to a diameter of 38 mm is described in this paper, where the probe is based on a miniature silicon diaphragm pressure transducer mounted at mid-height to cause minimum interference between the sample and probe.
Abstract: A technique has been evolved for installing a piezometer probe on samples down to a diameter of 38 mm. The probe is based on a miniature silicon diaphragm pressure transducer mounted at mid-height to cause minimum interference between the sample and probe and to provide a rapid response for the piezometer-soil system. Considerable savings can be made in testing times by using the probe at mid-height and by using effective lubricated end platens. Measurements can also be made in cyclic loading tests on clays and are viable in quick undrained tests even at shearing rates used in commercial laboratories. Examples are given of measurements made in undrained compression-extension triaxial tests in cromer fill and medium-dense ham river sand. The probe provides a more accurate method of measuring pore pressures in unconsolidated undrained triaxial tests and can be effectively used to maintain an acceptably low gradient of pore pressure in the sample when following a drained stress path. (TRRL)
TL;DR: The stability of axisymmetric excavation has been given little attention in the past, even though axismmetric excavations are common in the construction industry as mentioned in this paper, and analytical upper bound solutions for the failure of an unsupported axisymmetric excavation are presented for conditions where the soil is treated as a rigid plastic material, satisfying the Tresca yield criterion and possessing an uniform undrained shear strength.
Abstract: The stability of an axisymmetric excavation has been given little attention in the past, even though axisymmetric excavations are common in the construction industry. Analytical upper bound solutions for the failure of an unsupported axisymmetric excavation are presented for conditions where the soil is treated as a rigid plastic material, satisfying the Tresca yield criterion and possessing an uniform undrained shear strength. Wall failure mechanisms are found to be more critical than base failure and combined wall-base failure modes. The width of the failure zone at the surface for the critical wall mechanism is found to be 0·4 times the depth of the excavation. The stability number given by the present analyses is lower than that obtained previously. On ne s'est guere penche dans le passe sur l'etude de la stabilite d'excavations axisymetriques, bien que ce genre d'excavations soit courant la pratique. L'article presente des solutions analytiques de limite superieure se rapportant a la rupture d'une ex...
TL;DR: In this article, the authors considered a rigid caisson incident on a sea bed, where the sea bed is an isotropic poro-elastic half-space saturated with water, and the dynamics of the two phases are governed by Biot's equations.
Abstract: Sea waves incident on a rigid caisson induce stresses in the sea bed by the direct action of wave pressure and by the vibration of the caisson. Under the assumption that the sea bed is an isotropic poro-elastic half-space saturated with water, the dynamics of the two phases are governed by Biot's equations. To circumvent the difficulties of solving the coupled equations an approximate scheme is applied to achieve an analytic solution. The problem can first be reduced to a series of classical elastostatic problems which can be solved by complex variables, and then corrected for seepage near the mudline. Numerical results are presented. Des vagues marines qui frappent un caisson rigide engendrent des contraintes dans le fond marin en raison de l'action directe de la pression des ondes et de la vibration du caisson. Si l'on considere le fond marin comme un semi-espace poro-elastique isotrope sature d'eau, la dynamique des deux phases est regie par les equations de Biot. Afin de contourner les difficultes que...
TL;DR: In this paper, the authors examined the case of fully drained tests on clay specimens and, in particular, what constitutes a sufficiently slow rate of straining to approximate to the fully drained condition.
Abstract: In the triaxial soil test cylindrical soil samples are subjected to controlled axial strain through rigid end platens and also controlled radial stress through a rubber membrane. The author examines the case of fully drained tests on clay specimens and, in particular, what constitutes a sufficiently slow rate of straining to approximate to the fully drained condition. Non-homogeneous behaviour of the triaxial specimen may result from the migration of pore water through the specimen and perhaps across its boundaries during testing. Some of the non-homogeneities occurring in triaxial specimens due to migration of pore water are discussed. (Author/TRRL)
TL;DR: In this paper, an analysis of the California bearing ratio (CBR) test on saturated clays has been carried out using finite element techniques to examine whether the test adequately reflected the stiffness of the clays as this is an important parameter in determining the performance of road pavements on clay subgrades.
Abstract: An analysis of the California bearing ratio (CBR) test on saturated clays has been carried out using finite element techniques. The aim was to examine whether the test adequately reflected the stiffness of the clays as this is an important parameter in determiningthe performance of road pavements on clay subgrades. It is shown that the CBR does not correlate consistently with either strength or stiffness. In stiff intact clays, the CBR reflects only undrained strength; in clays compacted wet of optimum, the CBR depends on both stiffness and strength. Recommendations are made to use the full load-penetration curveas well as the CBR in the selection of subgrade or capping layer materials. Une analyse du CBR a ete realise sur des argiles saturees en employant des techniques a elements finis. L'objectif etait de decouvrir si le test retltte de facon satisfaisante le rigidite des argiles, qui represente un parametre important pour determiner le comportement des revetements de route sur des terrains de fondatio...
TL;DR: In this article, the modified effective stress concept was used to control the secondary compression behavior of saturated clay soils. But the authors did not consider the effect of the interparticle attractive and repulsive forces.
Abstract: This Paper deals with the mechanism controlling the one-dimensional secondary compression behaviour of saturated clay soils. The behaviour of the clays has been explained in the light of the modified effective stress concept which takes into consideration the interparticle attractive and repulsive forces. A non-dimensional secondary compression coefficient is defined as the ratio of the secondary compression per unit of log (time) to the final thickness of the sample for any pressure increment. It is shown that the secondary compression coefficient is directly related to the strength of soil skeleton at particle level which is governed by the modified effective stress concept. Seven organic fluids, water and air of different dielectric properties were used to vary the interparticle forces in the one-dimensional consolidation tests. To confirm the nature of the mechanism, tests were also conducted in which load increments, load increment ratio and void ratio were varied. The rectangular hyperbola method is...
TL;DR: Load tests on a model pile installed in Speswhite kaolin are described in this article, and the results show that the angle of shaft friction is independent of the stress ratio in the soil before loading, and is only just less than φ′triaxial for normally and overconsolidated kaolin.
Abstract: Load tests on a model pile installed in Speswhite kaolin are described. The soil surrounding the pile was consolidated under a range of stress ratios K, and the pile was loaded under drained conditions in such a way that only shaft friction was generated. Pile installation techniques minimized soil disturbance so that the failure criterion for pile shaft friction could be investigated. The results, based on tests on nine normally consolidated and one overconsolidated sample, show that the angle of shaft friction is independent of the stress ratio in the soil before loading (0·7
TL;DR: The sliding micrometer (TRRL) as mentioned in this paper is a portable strain measuring device with an accuracy of better than 3 microns, which can be used to determine the strain distribution, curvature and deflection of axially and laterally loaded piles.
Abstract: A novel portable strain measuring device called the sliding micrometer iseth has been developed. The continuous direct measurement of strain along one or more straight lines is possible using the device. A hard pvc tube is connected into the structure containing steel ring-shaped measuring marks at 1 M intervals. The rings contain stops to hold the two heads of the portable device in position during readings. A linear displacement transducer is used to determine the relative displacement of the measuring marks as a measure of the strain in the surrounding concrete. The instrument with a base length of 1 M has an accuracy of strain measurement in the field of better than 3 microns. The linearity of the inductance transducer can be checked by using a calibration frame before and after any set of measurements. Examples are given showing how the apparatus can be used to determine the strain distribution, curvature and deflection of axially and laterally loaded piles and the strain distribution and curvature of a diaphragm wall at the excavation stage. A load-settlement diagram is given for top and bottom of an axially loaded pile. (TRRL)
TL;DR: In this paper, a series of well-instrumented models showed that whereas the first occurrence of ultimate tensile strength in a strand of reinforcement was always reliable and was subject to a conservative limit state calculation after the fashion of Rankine, the ultimate collapse condition was less reliable owing
Abstract: The use of systems of earth reinforcement or anchorage is gaining in popularity It therefore becomes important to assess whether or not the methods of design which have been adopted for such constructions represent valid predictions of realistic limit states Confidence can only be gained with regard to the effectiveness of limit state criteria if a wide variety of representative limit states has been observed To clarify the nature of appropriate collapse criteria, over 80 centrifugal model tests of simple reinforced earth retaining walls have been carried out Collapses due to insufficient friction have been shown to be repeatable and are therefore subject to fairly simple limit state calculations However, a series of well-instrumented models showed that whereas the first occurrence of ultimate tensile strength in a strand of reinforcement was always reliable and was subject to a conservative limit state calculation after the fashion of Rankine, the ultimate collapse condition was less reliable owing
TL;DR: In this article, finite difference solutions for the fundamental process of pore pressure equalization in a soil piezometer system are presented for cyhndrical piezometers, and the cylindrical equalization chart is constructed, which provides a direct means for the analysis of equalization tests in cylinear piezometry.
Abstract: The finite difference solutions presented for the fundamental process of pore pressure equalization in a soil piezometer system are the first of their kind to be published for cyhndrical piezometers. The response-time relationships established for cylindrical piezometers (of radius a and length b) are of the same general form as those for spherical piezomelers, the exact shape of a particular relationship being a function of the ratio a/b, the soil compressibility m and the flexibility of the piezometer measuring system V. The soil-pierometer system characteristics can be best represented by a control parameter λ = 47πbm/V. The value of this parameter characterizes the shape of the response-time curve, for which there is a unique time ratio t90/t50 and time factor ratio T90/T50. On this basis, the cylindrical equalization chart is constructed, which provides a direct means for the analysis of equalization tests in cylindrical piezometers. Interpretation of laboratory tests on piezometers embedded in clay ...
TL;DR: In this paper, the measurement of undrained shear strength during flight using the design of vane apparatus described is examined, and it is suggested that this indicates a need to develop site investigation techniques for use with the centrifuge in flight.
Abstract: As a result of using a relatively permeable clay in a centrifuge two problems are likely to arise when the centrifuge is stopped during a test, or after a test has been carried out: a) voids are too large to sustain high porewater tension causing air entry or cavitation, b) high permeability allows excess water to be drawn into the clay by negative pore pressure. These phenomena have the effect of softening the clay and reducing shear strength so causing innacuracy in strength or deformation parameters measured. It is suggested that this indicates a need to develop site investigation techniques for use with the centrifuge in flight. The article examines the measurement of undrained shear strength during flight using the design of vane apparatus described. (Author/TRRL)
TL;DR: The importance of collaboration between geologists and geotechnical engineers is emphasized and the common interest in geomorphology is suggested as a useful link to enable both the geological engineering skills to be mobilized as discussed by the authors.
Abstract: The importance of collaboration between geologists and geotechnical engineers is emphasized and the common interest in geomorphology is suggested as a useful link to enable both the geological engineering skills to be mobilized. The role of geomorphology in the understanding of soil movements in the Gulf of Mexico during hurricanes is discussed. Attention is drawn to problems of tropical weathering and changes in soil chemistry which need further study. Some of the problems associated with groundwater lowering in an area underlain by dolomite are described together with the effects on stability of minor changes in surface drainage of an inclined rock layer. L'article souligne l'importance d'une collaboration plus etroite entre les geologues et les ingenieurs geotechniciens, afin que leurs etudes combinees puissent ameliorer simultanement leurs deux disciplines geologie et geotechnique. Puis est discute le role joue par la morphologie dans la comprehension des mouvements du sol pendant les ouragans dans le...
TL;DR: In this article, the velocity u of seepage through a model subjected to an increase in self-weight of N times will be greater than that experienced in a full-scale, geometrically similar prototype when the model and prototype have identical soils, hydraulic gradients and pore fluids in the ratio
Abstract: Laut (1975) considered how the velocity of laminar seepage through soil is affected by the increase of self-weight that occurs in centrifugal modelling. He concluded that the velocity u of seepage through a model subjected to an increase in self-weight of N times will be greater than that experienced in a fullscale, geometrically similar prototype when the model and prototype have identical soils, hydraulic gradients and pore fluids in the ratio
TL;DR: In this article, the authors examined the theory of a possible reason for the reduction in skin friction factor with increasing pile lengths and found that the major cause of the length effect on the pile load capacity is the reflective compressibility of the pile.
Abstract: This note examines the theory of a possible reason for the reduction in skin friction factor with increasing pile lengths. Results indicate that the major cause of the length effect on the pile load capacity is the reflective compressibility of the pile. Tthis is expressed as a dimensionless axial stiffness factor, proportional to the cube of the embedded pile length, the axial stiffness and the rate of increase of the soil modulus with depth. Other contributing factors, which could be incorporated into the equation, include possible strain-softening skin friction response and the degradation of the pile-soil contact along the top part of the pile caused by lateral vibrations induced in the pile during driving. (Author/TRRL)
TL;DR: Horizontal plate gauges have been used to monitor the behavior of major embankment dams during construction as discussed by the authors, where a sensing probe containing an induction coil was used to measure the horizontal distance to each plate, and a second water overflow orifice probe was subsequently pulled to the position of each plate to measure vertical movement.
Abstract: Horizontal plate gauges have been used to monitor the behaviour of major embankment dams during construction. Detailed measurements have been made of the movements of numerous discrete points within the fill. Each gauge consists of a line of horizontally laid plastic pipe with steel masker plates put over the measurement points. A sensing probe containing an induction coil was pulled through the pipes to measure the horizontal distance to each plate, and a second water overflow orifice probe was subsequently pulled to the position of each plate to measure vertical movement. Methods of installation and operation of the gauge, which has been recently modified for single-handed operation, are outlined. Examples of results obtained during construction of the Megget Dam show that the new plate gauge is more accurate and faster to read than the earlier type provided that the instrument chamber is in place before the gauge is installed so that zero readings can be obtained. (TRRL)
TL;DR: In this article, the interaction between a rigid circular foundation resting on an elastic halfspace and a distributed external load of finite extent which acts at an exterior region of the halfspace is studied.
Abstract: The paper is concerned with the interaction between a rigid circular foundation resting on an elastic halfspace and a distributed external load of finite extent which acts at an exterior region of the halfspace. This problem serves as a model for the examination of the interaction between an existing structural foundation and a newly constructed adjacent foundation. The mathematical procedures which lead to the theoretical analysis of the title problem are summarized. It is shown that the additional elastic settlements experienced by the rigid circular foundation due to the action of a concentrated external force can be evaluated in exact closed form. This solution is used to generate results which are applicable to distributed loadings. From the results presented it is possible to determine the additional elastic settlement of a rigid circular foundation on an elastic halfspace due to multiple loads, of arbitrary shape and location, which act in its vicinity. La communication traite de l'interaction entr...