SOILS AND FOUNDATIONS
Print ISSN : 0385-1621
Volume 32, Issue 2
Displaying 1-16 of 16 articles from this issue
  • SUSUMU IAI, YASUO MATSUNAGA, TOMOHIRO KAMEOKA
    1992 Volume 32 Issue 2 Pages 1-15
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    The cyclic mobility model proposed in this paper is of a generalized plasticity-multiple mechanism type. The salient feature of the present approach is that the concept of the multiple mechanism, within the framework of plasticity theory defined in strain space, is used as a vehicle for decomposing the complex mechanism into a set of one dimensional mechanisms. The other feature is that the undrained stress path is idealized with the concept of liquefaction front, which is defined in the effective stress space as an envelope of stress points gradually approaching the failure line. Once coded into the finite element program, most of the existing models suffer from serious difficulty in the numerical solution process when effective stress path becomes very close to the failure line. A numerically robust approach is proposed in this paper by introducing a scheme for gradually enlarging scale of shear strain with progress of cyclic mobility.
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  • SUSUMU IAI, YASUO MATSUNAGA, TOMOHIRO KAMEOKA
    1992 Volume 32 Issue 2 Pages 16-20
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    In order to examine the capability of a cyclic mobility model consisting of multiple shear mechanism defined in strain space (Iai et al., 1992), cyclic behavior of anisotropically consolidated sand is analyzed under an undrained and simple shear condition. This behavior of sand, though commonly encountered in earthquake engineering, was not easy to analyze with the conventional plasticity models because it involves effects of rotation of principal stress axis directions. Two analyses are conducted in the present study; one is cyclic simple shearing with constraining lateral normal strain as in the level ground, the other is without the constraint on the lateral strain but keeping the axial stress difference unchanged. The former analysis indicates that cyclic behavior of sand is not affected by initial anisotropic consolidation conditions if initial mean effective stress is kept the same. The latter indicates gradual growth in the axial strain difference causing gradual settlement with lateral bulging. Both of these results are consistent with the previous laboratory findings, suggesting reasonable applicability of the cyclic mobility model.
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  • HARUYOSHI MAEKAWA, KEI MIYAKITA, HIDEKI OHTA
    1992 Volume 32 Issue 2 Pages 21-34
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    Studied is the geometrical character of the yield locus of a diatomaceous mudstone which has an artificially made plane of separation in itself. The diatomaceous mudstone behaves in such a way that overconsolidated clays typically behave, although the diatomaceous mudstone is chemically bonded and has its post geological history totally different from that of overconsolidated clays. The location of the yield points in the stress space was searched by applying the loads to the specimens of diatomaceous mudstone being brought from the elastic state into the elasto-plastic state under the load beyond the yielding stress. The diatomaceous mudstone used in this investigation is a uniform material carefully taken from a mining pit. Thus taken specimens are under undisturbed, saturated and unweathered conditions. The diatomaceous mudstone has a distinct yielding point on the stress-strain curve obtained from the CD (consolidated-drained) tests. The yield locus of the diatomaceous mudstone is well described by the Cam Clay model as is already reported. In this paper, the yielding of the intact diatomaceous mudstone is firstly introduced. The yielding of discontinuous specimens of diatomaceous mudstone having a plane of separation artificially made at three different angles is then investigated. Major conclusions obtained in this study are as follows. (1) The patterns of yielding behaviour are classified into two categories depending both on the angle θ of the plane of separation and on the confining pressure. (2) The yield locus of the specimen which slides along the plane of separation is represented by q = β(θ)·p', while the yield locus of the specimen which fails without sliding along the plane of separation is represented by q/p'+Mln(p'/pc')=0, i.e., the Cam-Clay model. (3) The yield locus of the specimen having the plane of separation at an angle of 37.1°≤θ≤90° to the horizontal plane is represented by the combination of two types of yield functions mentioned above depending the magnitude of confining pressure. (4) The shape of p' vs volumetric strain εvy curve coincides with that of intact specimen regardless of the pattern of yielding.
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  • YASUAKI ICHIKAWA, TOSHIYUKI OHKAMI
    1992 Volume 32 Issue 2 Pages 35-44
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    The material parameter identification problem is classified into the inverse and direct formulations. The former method was firstly proposed by Kavanagh (1973). The procedure is as follows : Observed data are built in boundary conditions of the finite element formulation, then by using its inverse relation the elastic constants are obtained. This is a simple method, however, it sometimes gives inaccurate results. The second formulation is based on the least square method. That is, material parameters are identified by minimizing the error defined between observed data and computed results. This method also gives an insufficient solution especially for the case to identify Young's modulus and Poisson's ratio simultaneously. We here propose a new method under the concept of boundary control.
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  • HIROSHI HAYASHI, A.HS. ANG
    1992 Volume 32 Issue 2 Pages 45-56
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    This paper presents a method capable of evaluating the seismic stability of a cut slope formed by strain-softening soil; to date, no method appears to be available for this purpose. The method consists of the following steps : (1) the horizontal vibration of a sliding mass subjected to an earthquake loading is converted into an equivalent single-degree-of-freedom (SDF) system with a smooth hysteretic restoring force; (2) a failure criterion and a damage index for the converted SDF system is established; and (3) the safety based on the response statistics obtained through random vibration analysis is evaluated. Reliability against sliding failure is assessed for specified intensity and duration of a seismic loading using results from a nonlinear-hysteretic random vibration analysis.
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  • TAKAO ITO, AKIE ASADA, TATSUO KONNO
    1992 Volume 32 Issue 2 Pages 57-66
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    During earthquakes, saturated loose sandy soils often liquefy, causing serious damage to buildings and underground structures. Various construction methods have been employed to stabilize these soils against liquefaction, the most popular being those which increase their density. Vibration and impact methods are commonly employed, but these are often a problem in urban areas. We studied the usage of a composite soil improvement material called Quick-Lime Consolidated Briquette. This material is placed to form cylinders, resulting in static consolidation of the surrounding soil due to absorption of soil water and consequent swelling. In our study, static consolidation increased density, and the swollen material became aggregate-like soon after placement, thus quickly stabilizing the surrounding soil. This report examines the preventive effect of quick-lime consolidated briquette piles against liquefaction as well as a method of determining optimum pile diameter and pitch.
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  • TATSUNORI MATSUMOTO, HIDEO SEKIGUCHI, HIROSHI YOSHIDA, KATSUTOSHI KITA
    1992 Volume 32 Issue 2 Pages 67-82
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    This paper is concerned with dynamics of the standard penetration test (SPT). The usefulness of mounting strain gages at two different stations along a driven rod is described, together with a workable procedure of analysis. The analysis procedure makes use of the traveling time between the two gage points and enables one to identify the particle velocity, the displacement and the stress at any station of the rod, as well as the energy actually transmitted from a hammer to the rod. Particular attention is called for the consequence of inevitable, small errors in strain data upon such identifications. A pertinent procedure of error-correction is proposed and its validity is substantiated against the performance of well instrumented SPTs performed by the authors.
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  • GORO IMAI, YIXIN TANG
    1992 Volume 32 Issue 2 Pages 83-96
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    In order to investigate the general relationship between void ratio e, effective stress σ' and time t at any element in a consolidating clay specimen, an inter-connected consolidometer was developed and a series of experiments on a remolded marine clay was conducted. In the experiments, several thin subspecimens were prepared in individual consolidation cells in the same way, while their drainage channels were connected successively. During consolidation, the settlement of each subspecimen and the pore water pressure between adjacent subspecimens were measured continually, and vertical distributions of e and σ' in the specimen and their changes with time were obtained by calculation. The results obtained showed that on an e-σ' plane there exists a family of e-σ' lines each of which uniquely corresponds to certain value of void ratio rate e. This constitutive model f(e, σ', e) = 0 for the clay skeleton was further experimentally verified for different consolidation conditions. Then the model was used as a tool to explain the effects of layer thickness on compressive strain by consolidation, resulting in good agreement with simulated experiments. The permeability characteristics were also examined for the clay by use of the experimental data. It was found that permeability coefficient varies exponentially with void ratio.
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  • PANOS DAKOULAS, HUMAYUN HASHMI
    1992 Volume 32 Issue 2 Pages 97-110
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    An analytical model is presented for steady-state lateral response of earthfill and rockfill dams in canyons subjected to a steady train of harmonic SH waves incident at an arbitrary angle θ. The dam is idealized as a 2-dimensional shear beam with a triangular cross-section, while the canyon is considered rectangular and consisting of elastic rock. A parametric study is undertaken to investigate the influence on the steady-state response of (a) the angle of incidence θ of the incoming waves, (b) the impedance ratio and (c) the canyon narrowness. It is shown that the acceleration amplification is considerably less for a dam built in flexible canyon than for a dam in a rigid canyon and, hence, the effect of radiation damping may be very important. For obliquely incident waves travelling from the left to the right, the response of the dam depends mainly on the interference of the waves transmitted through the base and the left boundary, leading to a maximum response at a θ about 30°-35°. For very long dams subjected to high frequency obliquely incident waves, it is found that there is no amplification of the motion by the dam. For low-frequency excitation, the response of the dam shows little variation along the crest and approaches the response of the elastic half-space. The results are in agreement with published results for the response of alluvial valleys subjected to incident SH waves.
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  • R.J. JARDINE
    1992 Volume 32 Issue 2 Pages 111-124
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
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    The Paper attempts to describe soil stress-strain behaviour by defining, in normalised stress-space, an outer Bounding Surface and three characteristic Zones which sub-divide the permissable interior region. The types of behaviour exhibited within each Zone are illustrated using experimental data. It is demonstrated that the Zone boundaries, or Sub-Yield Surfaces, are mobile and may be both re-positioned and modified by moving the current stress point. This scheme is found to offer a powerful way of envisaging many poorly understood aspects of soil stress-strain behaviour.
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  • TATSURO MURO
    1992 Volume 32 Issue 2 Pages 125-133
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
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    On earth moving sites, it is considered very important for the application height of effective braking force of a bulldozer towing a scraper down a weak slope terrain to be controlled in accordance with the pushing force of the scraper in order to avoid excessive wear of the track belt. Here, the tracking performance of a flexible tracked vehicle towing a scraper down at a constant speed on a given remolded silty loam sloping terrain is analysed by the use of a simulation program. As a result, it is clarified that the optimum application height under the maximum braking power decreases with the increment of pushing force of the scraper, and that the height should be controlled automatically according to the pushing force of the scraper, which is dependent on the slope angle.
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  • KATSUTOSHI KITA, TORU SHIBATA, ATSUSHI YASHIMA, SHUNICHI KOBAYASHI
    1992 Volume 32 Issue 2 Pages 134-140
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
    A method of measuring the shear wave velocities of sand in a centrifuge is presented. The generation and propagation of seismic waves are modelled within the framework of elastodynamics. An experimental system to measure the shear wave velocities was developed with a disk-shaped piezo-electric oscillator as a seismic wave generator. The propagation of the seismic wave was detected by two accelerometers at two different stations. The shear wave velocities were measured under various centrifugal accelerations up to 100-g. The measured waveforms show good agreement with what have been predicted from the theory. The shear wave velocities show strong dependency on the effective confining pressure.
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  • Kaname Tajiri, Hiroshi Nakayama, Shigeyoshi Imaizumi
    1992 Volume 32 Issue 2 Pages 159-168
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
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  • Hiromu Kusuda, Takashi Nishiyama, Kazuhiko Nishida
    1992 Volume 32 Issue 2 Pages 169-175
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
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  • Tatsuya Koumoto
    1992 Volume 32 Issue 2 Pages 176-179
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
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  • Motonori Enokido, Junji Kameta
    1992 Volume 32 Issue 2 Pages 180-185
    Published: June 15, 1992
    Released on J-STAGE: February 29, 2008
    JOURNAL FREE ACCESS
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