Showing papers in "Geotechnique in 1983"
TL;DR: In this paper, a simple empirical failure criterion is presented and its application in engineering design is illustrated by means of a number of practical examples, and the authors summarize some of the basic information upon which such simplifying assumptions can be made.
Abstract: Jointed rock masses comprise interlocking angular par- ticles or blocks of hard brittle material separated by discontinuity surfaces which may or may not be coated with weaker materials. The strength of such rock masses depends on the strength of the intact pieces and on their freedom of movement which, in turn, depends on the number, orientation, spacing and shear strength of the discontinuities. A complete understanding of this problem presents formidable theoretical and experi- mental problems and, hence, simplifying assumptions are required in order to provide a reasonable basis for estimating the strength of jointed rock masses for engineering design purposes. This Paper summarizes some of the basic information upon which such simplifying assumptions can be made. A simple empirical failure criterion is presented and its application in engineering design is illustrated by means of a number of practical examples. Des masses jointives de rochers comprennent des particules angulaires enchevetrees ou des ...
641 citations
TL;DR: In this paper, the authors describe both the design and principles of operation of a new hollow cylinder apparatus and its application to the investigation of principal stress rotation effects in sands and clays.
Abstract: In the wall of a hollow cylindrical specimen under combined axial load, torque and internal and external radial pressures, the magnitude and direction of the major and minor principal stresses can be controlled together with the magnitude of the intermediate principal stress This Paper describes both the design and principles of operation of a new hollow cylinder apparatus and its application to the investigation of principal stress rotation effects in sands and clays A discussion is presented of the stress and strain nonuniformities which occur in a hollow cylinder specimen as a result of its curvature and of restraint at its ends The manner in which these non-uniformities have been minimized, by selection of a sample geometry of 203 mm id × 254 mm od × 254 mm height and by the use of internal instrumentation, is described The results of tests on dense Ham River sand are presented to demonstrate the capabilities of the apparatus Dans la paroi d'un echantillon creux cylindrique sous une combinatio
389 citations
TL;DR: In this article, the authors examined the five elastic parameters needed to describe transverse isotropy, sometimes called crossanisotropy, and proposed reasonable assumptions with easily identifiable physical significance, which permit extrapolation from triaxial to more general stress conditions.
Abstract: Lightly overconsolidated natural clays are commonly anisotropic because of their mode of deposition. They exhibit substantial ranges of approximately linear, reversible (elastic) behaviour at stress levels which do not produce yielding of the particle structure of the clay. The Paper examines the five elastic parameters needed to describe transverse isotropy, sometimes called crossanisotropy. Only three parameters can be measured in triaxial tests, and reasonable assumptions, with easily identifiable physical significance, are proposed which permit extrapolation from triaxial to more general stress conditions. Convenient parameters are identified such as the bulk modulus K, shear modulus G, and a cross modulus J which expresses the relationships in a transversely isotropic soil between mean stress and shear strain and between shear stress and volumetric strain. A least squares solution is used to evaluate these parameters from 76mm diameter triaxial tests on Lake Agassiz clay from Winnipeg, Canada. The so...
380 citations
TL;DR: Following about two months of intense outward movement and strength deterioration associated with magmatic intrusion, seismicity and gravitational creep, an earthquake on 18 May 1980 marked the col... as mentioned in this paper.
Abstract: Following about two months of intense outward movement and strength deterioration associated with magmatic intrusion, seismicity and gravitational creep, an earthquake on 18 May 1980 marked the col...
343 citations
TL;DR: In this article, the results from a series of conventional tests and stress-probe tests on two different clays were shown that yield envelopes in lightly overconsoli-dated natural clays are time-dependent, and contract in p&rime, q-space.
Abstract: Laboratory tests on a wide variety of lightly overconsoli-dated natural clays show that important engineering properties such as undrained strength and preconsolidation pressure are time-dependent. Relaxation and step-changing procedures suggest that these properties decrease by 10–20% with a tenfold decrease in the speed of testing. The influence of strain rate on undrained shear strength appears to be independent of soil plasticity, test type or stress history during laboratory reconsolidation. Its influence on stress-compressibility curves from oedo-meter tests is independent of soil plasticity and test conditions. Ageing and delayed compression in clays produce a stiffer arrangement of the soil particles, and a quasi-preconsolidation pressure that is in part available for foundation design. The results from a series of conventional tests and stress-probe tests on two different clays show that yield envelopes in lightly overconsoli-dated natural clays are time-dependent, and contract in p&rime, q-space...
299 citations
TL;DR: In this article, a general method of three-dimensional slope stability analysis using the limit equilibrium concept is proposed, where the failure mass is assumed to be symmetrical and divided into many vertical columns.
Abstract: A general method of three-dimensional slope stability analysis using the limit equilibrium concept is proposed. The failure mass is assumed to be symmetrical and divided into many vertical columns....
176 citations
TL;DR: In this article, volume change properties of the more important British clay soils are discussed and the impact of seasonal variations in soil moisture and the significant reductions that trees can induce are discussed.
Abstract: The Paper describes volume change properties of the more important British clay soils. Seasonal variations in soil moisture and the significant reductions that trees can induce are discussed. The impact of the 1975–76 drought in Britain which generated many cases of building damage is considered by the application of a damage classification, the results of which suggest that levels of damage have not generally been large. However, the large heave movements which can occur close to trees following their removal are emphasized. Recently published information on the range of influence of various tree species in clays in urban conditions is reviewed and a hierarchy of damaging trees is presented. Some consideration is given to the difficulty of detecting desiccation in clays, with some practical though limited guidance being suggested. Three short case histories are presented to illustrate the influence of trees on both existing buildings and new construction. Cet article decrit les proprietes de changement d...
90 citations
TL;DR: In this article, a generalized e-log 10 p equation has been derived for the compressibility of saturated, normally, consolidated uncemented soil systems based on the Gouy-Chapman diffuse double layer theory.
Abstract: Soils primarily being paniculate media, any attempt to understand, interpret, generalize and predict their volume change behaviour would greatly enhance the rational approach to geotechnical engineering problems. This Paper deals with the development of a scientific basis for assessing the volume change response of fine grained, uncemented, normally consolidated, saturated soil systems. A generalized e-log10 p equation has been derived for the compressibility of saturated, normally, consolidated uncemented soil systems based on the Gouy–Chapman diffuse double layer theory. It has been shown that Skempton's compressibility equation is a logical consequence of development from the diffuse double layer theory. At present this equation is extensively employed to obtain the ranges of Cc values of soil systems with only liquid limit water contents known. An engineering approach has been developed in the present investigation to identify the natural systems under equilibrium for any one of the three material sta...
88 citations
TL;DR: In this paper, the authors describe research into the patterns of deficit near 36 different trees, covering a range of tree species and clay types, and demonstrate that poplars have much greater effects than the other species which are investigated.
Abstract: Existing guidelines on the proximity of trees and buildings are based on the concept of permitting minimum foundation depths and then trying to ensure sufficient separation between the tree and building to prevent damage. Such guidelines are impractical and are not universally accepted or implemented. The alternative approach is to increase foundation depth to permit most tree planting designs and natural regeneration, but in the past very little information has been available on the necessary depths. The Paper describes research into the patterns of deficit near 36 different trees, covering a range of tree species and clay types. It demonstrates that poplars have much greater effects than the other species which are investigated. Clay type makes little difference to the patterns of deficit, although it is important because of differences in permeability and the amount of shrinkage which occurs. Differences between individuals of the same tree species are comparatively small, unless there are anomalies in...
84 citations
TL;DR: Soil movement is of great importance in Australia because about 20% of the total area consists of expansive soils, most of which occur in the semi-arid climatic zone.
Abstract: Soil movement is of great importance in Australia because about 20% of the total area consists of expansive soils, most of which occur in the semi-arid climatic zone. The first measurements of soil movement were made in Adelaide under natural grassland. From this limited information, it was deduced that there was little soil movement below 1·6m. Recently, movements have been measured in clay layers at much greater depths. These movements have been attributed to shrinkage due to desiccation by deep rooted vegetation, and swelling due to ponding of water. Several case histories are discussed where the effects of vegetation have caused movements of buildings of up to 150mm settlement and 100mm heave. To calculate potential soil movement caused by vegetation, the extremes of total soil suction and a quantitative value of the volume change properties of the soil are required. The instability index, Ip has been suggested as a measure of this soil property and was measured on two of the most expansive and widesp...
80 citations
TL;DR: In this article, the authors present evidence that very small hydraulic gradients should be used in laboratory permeability tests to minimize errors arising from seepage-induced consolidation, which can be performed in substantially less time than either a constant or falling head test.
Abstract: The author presents evidence that very small hydraulic gradients should be used in laboratory permeability tests to minimize errors arising from seepage-induced consolidation. These errors will be carried forward to practice in significant ways. The gradients must be such that the seepage-induced effective stresses are substantially less than the maximum past effective stress. In cases of normally consolidated soils, there will always be induced errors: the softer the clay, the greater the errors. These errors seem to be compounded by conventional constant and falling head permeability tests, because of the high gradients involved, and can be readily minimized by the flow pump method. In addition, this test can be performed in substantially less time than either a constant or a falling head test. In using conventional tests one is faced with a paradox. The use of high gradients reduces the time of testing but introduces substantial errors in the test results. However, the use of low gradients extends the testing time to unacceptable limits. The flow pump test solves both these problems. If the clay is very soft and normally consolidated, even the lowest gradients can cause significant consolidation. It may well be that indirect measurements, using inversion techniques, will be required for these cases. The laboratory data presented are based on gross changes in sample thickness and thus on average void ratios. For a complete analysis consideration of the time-dependent void ratio distribution within the sample during the test is required. (Author/TRRL)
TL;DR: In this paper, the static and dynamic response of single free-head piles embedded in a soil stratum, the modulus of which increases linearly with depth, is investigated by means of a dynamic finite-element formulation which accounts for the three-dimensionalality of soil deformation while properly reproducing the radiation damping characteristics of the system.
Abstract: The Paper presents the results of a systematic parametric investigation of the static and dynamic response of single free-head piles embedded in a soil stratum, the modulus of which increases linearly with depth. The study is conducted by means of a dynamic finite-element formulation which accounts for the three-dimensionality of soil deformation while properly reproducing the radiation damping characteristics of the system. The soil is modelled as a linear hysteretic continuum and the excitation consists of a sinusoidally time-varying horizontal force or moment, applied at the pile head. Comprehensive plots of the results are presented in non-dimensional form, for a wide range of the most significant dimensionless groups of problem parameters. For the response of flexible piles, in particular, simple algebraic expressions are developed in terms of the ratio E,/E,, of the pile and soil moduli. These expressions, being valid for several values of Poisson’s ratios of the soil, compare favourably with results from previous studies and are expected to be useful in practical design calculations.
TL;DR: In this article, the deformations in the soil behind a flexible cantilever retaining wall can be predicted using a simple velocity field, which can be used for a wall with an anchor or support.
Abstract: Bransby & Milligan (1975) showed how the deformations in the soil behind a flexible cantilever retaining wall could be predicted using a simple velocity field. For a wall with an anchor or support ...
Journal Article•
TL;DR: In the more humid areas of the USA, the greater portion of shrinkage is caused by transpiration from vegetation as mentioned in this paper, which can be very significant, often adversely tipping the damage scale.
Abstract: Soils subject to swelling and shrinking can be found in most of the states in the continental United States of America, extending from the east coast to the west coast and from the north to the south. The cost of damage to structures placed on these soils is said to exceed the combined cost of all damage caused by earthquakes, tornadoes, hurricanes and floods. A significant portion of volume changes caused by shrinking and swelling can be attributed to the desiccation effects of vegetation. In the more humid areas of the USA, the greater portion of shrinkage is caused by transpiration from vegetation. In the arid and semi-arid parts of the country, evaporation is a major factor but transpiration losses can be very significant, often adversely tipping the damage scale. The effects of vegetation on soil moisture changes are very complex. These involve trees, shrubs and grasses, which may not only draw moisture from the soils, but may also cause changes in soil temperatures, soil chemistry, infiltration of w...
TL;DR: In this article, the depth of root systems in the highveld is given as well as the ranges of soil suction are often in excess of pF 1 for clays found in this region.
Abstract: Examples are given of the depth of root systems in the highveld. The heaving clays found in this region can cause extensive damage to buildings. The ranges of soil suction are often in excess of pF...
TL;DR: In this paper, the authors evaluated soil moisture and volume changes in bare field soils and in the presence of vegetation in a controlled manner, and found that the majority of shrinkage cracks extend to depths less than 50 cm, although depths of up to 135 cm are reported.
Abstract: Soil moisture and volume changes in bare field soils and in the presence of vegetation are evaluated. In bare fields below the uppermost soil layer, which may dry up relatively fast, moisture may remain practically unchanged for a very long time if shrinkage cracks do not form. Deep-rooting plants can extract water from gradually increasing depths of up to 2–3 m, drying the soil to no lower than wilting moisture content, in general above the shrinkage limit. Accelerated drying rates under hot and dry weather conditions cause shrinkage crack formation in highly expansive soils. Crack formation is enhanced in cropped soils. The majority of shrinkage cracks extend to depths less than 50 cm, although depths of up to 135 cm are reported. Moisture and volume changes are observed to depths of 1·5–2·0m in cracked soils. In the presence of deep-rooting crops the time required to reach maximum cracking volume is significantly shorter and the cracks are deeper and wider. L'article evalue l'humidite du sol et les mod...
TL;DR: The variability of unweathered chalk is judged on the basis of approximately 600 tests to determine dry density, and 200 Atterberg limit tests as discussed by the authors, and the influence and extent of a number of diagenetic processes are examined.
Abstract: The chalk in England is a highly variable material, and much of its variability stems from the wide variety of diagenetic processes which have been identified from lithological studies. This Paper reviews those processes, and presents results of laboratory index tests to determine their significance. The variability of the unweathered chalk is judged on the basis of approximately 600 tests to determine dry density, and 200 Atterberg Limit tests. The influence and extent of a number of diagenetic processes are examined. The degree to which the index properties are predictable (both stratigraphically and geographically) is discussed. En Angleterre la craie est un materiau qui varie beaucoup. Cette variabilite est le resultat d'une grande variete de phenomenes diagenetiques qui ont ete identifies a partir des etudes lithologiques. Cet article passe en revue ces phenomenes et puis presente les resultats des essais des proprietes caracteristiques faits dans le laboratoire avec le but de determiner leur signifi...
TL;DR: In this article, a mecanique des materiaux granulaires en deformation deviatoire is described, and a nouvelle approche is proposed, based on the coaxialite des tenseurs de contrainte et de vitesse de formation.
Abstract: Cet article se rapporte a la mecanique des materiaux granulaires en deformation deviatoire, et en propose une nouvelle approche. Supposant la coaxialite des tenseurs de contrainte et de vitesse de formation et que le materiau absorbe de l'energie mecanique au cours de la deformation, on en deduit l'existence d'un angle d'ecoulement, grandeur objective, qui permet d'ecrire une equation d'ecoulement. Lorsque l'angle d'ecoulement est differend de π/2, on deduit analytiquement de l'equation d'ecoulement que dans le cas general, les modes de deformation permis verifient un certain principe d'exclusion. En deformation plane ou symetrie axiale, a volume massique variable la relation contraintedilatance de Rowe est satisfaite, l'angle d'ecoulement s'identifie au frottement intergranulaire de Rowe, et a volume massique constant, la loi de Coulomb est satisfaite, l'angle d'ecoulement s'identifie au frottement interne. Sous contrainte quasi-isotrope, dans le cas general toute deformation entraine une contraction en ...
TL;DR: In this article, the authors reviewed the performance of a variety of support systems in the Four Fathom mudstone over a period of five years and the important lessons learned from these long-term experiments are reviewed.
Abstract: The entrance to the Kielder experimental tunnel was sealed late in 1979 about the same time as the driving of the 32 km long 3·3 m dia. tunnel for the Kielder Water Scheme was completed. The experimental tunnel was the scene of quite detailed studies of the performance of a variety of support systems in the Four Fathom mudstone over a period of five years. The important lessons learned from these long-term experiments are reviewed. In particular the most recent experiment where the same support, consisting of an annulus of sprayed concrete, was placed at different times after excavation (equivalent to different amounts of rock yielding) is reported. This has enabled characteristic lines, or ground-reaction curves, to be established in the field. The strains and deformations in the cast in situ concrete lining, in a part of the Kielder main tunnel where it passes through the same mudstone, are also presented. These demonstrate that it is lightly loaded-a result to be expected from the experimental tunnel s...
TL;DR: In this article, the authors demonstrate that simple application of the principles of effective stress and seepage laws leads to the perhaps surprising result that the longterm loads acting on linings below the water table are unaffected by whether the lining is watertight or not.
Abstract: In this note the authors demonstrate that simple application of the principles of effective stress and seepage laws leads to the perhaps surprising result that the long-term loads acting on linings below the water table are unaffected by whether the lining is watertight or not. This is only valid for cases where the original groundwater level is only little affected by the lining acting as a drain, and where the flownet is approximately radial, and is therefore of most relevance to relatively deep tunnels. The practical significance of this result is that it is erroneous to suppose that the total load on a watertight deep tunnel (or sewer lining or buried pipe) in soil would be reduced by allowing the lining to be permeable. By relieving the water pressure in the soil immediately outside the lining. a steady-state seepage would develop and the seepage stresses imposed on the soil grains (and therefore on the lining) would balance the relief of the water pressure.
TL;DR: In this article, a mathematical model of the generalized viscoelastic solid is proposed to find the time and strain dependence of the moduli, where the damping factor (1/Q) is also a known function of strain.
Abstract: Measurements of moduli by shear wave methods are made in short times and for low strains. Calculations of settlements of foundations require data corresponding to longer times and often to greater strains. The time dependence may be described by a mathematical model of the generalized viscoelastic solid where the characteristics are shown by the damping factor (1/Q) as a function of time. (1/Q) is also a known function of strain and so the time and strain dependence of the moduli may be found. Settlement curves are compared with experimental data for loaded pads on boulder clay. Les mesures des modules par les methodes employant les ondes de cisaillement sont effectuees pendant de courtes periodes et pour de basses contraintes. Les calculs de tassement des fondations necessitent des donnees correspondant a des temps plus longtemps et des contraintes souvent plus elevees. La dependance du temps peut se decrire par un modele mathematique d'un solide viscoelastique generalise ou les caracteristiques sont mon...
TL;DR: In this article, the authors compare some well known liquefaction results obtained by Seed and his co-workers at the University of California with extant field liquefactory data derived mainly from Japanese earthquakes and reveal Seed's results to be generally over-conservative for small earthquakes and possibly unconservative for very large earthquakes.
Abstract: In this note, the authors compare some well known liquefaction results obtained by Seed and his co-workers at the University of California with extant field liquefaction data derived mainly from Japanese earthquakes. The comparison reveals Seed's results to be generally over-conservative for small earthquakes and possibly unconservative for very large earthquakes. (TRRL)
TL;DR: In this article, it is shown that earthquake-induced liquefaction consists of a cyclic instability dominated by heterogeneities in the soil, and as such is a phenomenon that is fundamentally intractable analytically.
Abstract: This technical note demonstrates that earthquake-induced liquefaction consists of a cyclic instability dominated by heterogeneities in the soil, and as such is a phenomenon that is fundamentally intractable analytically. Consequently it is shown that the liquefaction analyses proposed by the Berkeley school are fundamentally incorrect, not just after zero effective stress has been reached in the soil, but well before that - that is as soon as any pore pressure is generated and any softening of the soil takes place. The method is fundamentally in error in assuming that dynamic stressing of the soil takes place independently of soil softening. A distinction is also made between liquefaction failure and flowslides, which is a phenomenon originally addressed by the Harvard school in its studies of soil behaviour at densities looser than critical. It is argued that the only way in which reliable design procedures against liquefaction can be developed is by the creation of empirical design criteria based on direct experimental data. Where possible this should involve experimentation at full scale, which is by definition the most accurate method. However, such data is necessarily very limited and very expensive, and so it is suggested that these design rules should be developed from the second most accurate experimental method, namely centrifuge modelling, and then calibrated wherever possible against measured full-scale results. It is also suggested that the most accurate form of in situ index testing of soil liquefaction potential will incorporate the self-boring pressuremeter, and some preliminatry recommendations are given in this note. (Author/TRRL)
TL;DR: In this article, the authors describe some problems encountered with the foundations of a building in Salisbury, England, where excavation for a basement within a coffer-dam led to a piping failure of the chalk in the base which was found to be much softer than expected.
Abstract: The Paper describes some problems encountered with the foundations of a building in Salisbury, England. Excavation for a basement within a coffer-dam led to a piping failure of the chalk in the base which was found to be much softer than expected. This gave rise to fears for the adequacy of the foundations. Large-scale loading tests were carried out to assess the load-settlement characteristics of the foundations. The settlement of the building was observed during and subsequent to construction.
TL;DR: In this article, the pore fluid and the solid matrix move together as a single phase, except in a thin boundary layer near the ground surface, and the analytical method of Muskhelishvili in elastostatics is applied to obtain the effective stresses near the structure.
Abstract: A fluid-filled poro-elastic foundation supporting a long and rigid structure is subjected to a normally incident Rayleigh wave. For sufficiently low permeability and high frequency, the pore fluid and the solid matrix move together as a single phase, except in a thin boundary layer near the ground surface. Hence the dynamics of most of the porous medium is governed by the usual laws of elastodynamics with effective moduli which depend on both constituent phases. In this Paper, the dynamic stresses and pore pressure beneath the structure are studied. When the structure is small compared to the wave length, the neighbourhood of the structure is approximately quasi-static with time being a parameter only. The analytical method of Muskhelishvili in elastostatics is then applied to obtain the effective stresses near the structure. By mass conservation, the corresponding pore pressure is found immediately. Boundary layer corrections are added to complete the solution. The so-called outer solution presented here...