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  • 善 功企, /, 大山 巧, TAKUMI OHYAMA
    地盤工学会論文報告集
    1998年 38 巻 2 号 37-47
    発行日: 1998/06/15
    公開日: 2008/02/29
    ジャーナル フリー
    The mechanism of wave-induced instability in a permeable seabed have been studied for more than two decades. The distinction between shear failure and liquefaction, however, has not been clearly defined. This paper presents a fundamental study on the differences in two failure modes for a fully saturated seabed of both finite and infinite thickness. The wave-induced effective stresses and pore pressure, obtained from an analytical solution of Biot's pore-elastic consolidation theory, were employed to examine the failure modes under a two-dimensional plane strain condition. A case study is presented to examine the failure modes with respect to several parameters, such as excess pore pressure, seepage flow, seepage force, failure areas and stress path in the seabed. The conclusions obtained from this study were as follows ; (1) the thickness of a permeable seabed affects the pore pressure and effective stress response to ocean waves and the failure mode of the seabed, (2) either a liquefaction or shear failure, or both, occur in the seabed, even in the saturated seabed, (3) the Mohr-Coulomb's failure criterion, when combined with elastic stresses, can not be employed to estimate the liquefaction failure in the seabed, (4) the liquefaction can be evaluated by a criterion in terms of the excess pore pressure, (5) The liquefied zone in the seabed is significantly different from the shear failure zone. The shape beneath the seabed surface for the former is almost identical to the contour where the upward seepage flow is concentrated.
  • 井合 進, 森田 年一, 亀岡 知弘, 松永 康男, 安彦 和之
    土質工学会論文報告集
    1995年 35 巻 1 号 115-131
    発行日: 1995/03/15
    公開日: 2008/02/29
    ジャーナル フリー
    In the 1993 Kushiro-oki Earthquake of Richter magnitude
    7
    .
    8
    , simultaneous recording of earthquake motions was successfully made at the ground surface and at a depth of 77 meters in a dense saturated sand deposit. The peak horizontal acceleration was 0.47 g on the ground surface and 0.21 g at a depth of 77 meters. The acceleration record at the ground surface showed a distinctive ground response, which consisted of a cyclic motion having a period of about 1.5 seconds overlain by a spike at each peak of the motion. In order to study the mechanism of this peculiar ground response, effective stress analysis was conducted on the dense saturated sand deposit. The model used for this study was a strain space multiple mechanism model, which takes into account the effect of principal stress axis rotation. The recorded earthquake motion at a depth of 77 meters was used as the input earthquake motion for the analysis. Sampling after in-situ freezing was done in order to evaluate the properties of the sand. The results of the analysis indicated that the observed ground response was due to the effect of dilatancy of sand, which plays a significant role in the response of the dense saturated sand deposits during strong earthquake motions.
  • OSAMU MATSUO
    地盤工学会論文報告集
    1996年 36 巻 Special 号 235-240
    発行日: 1996年
    公開日: 2012/08/13
    ジャーナル フリー
    Among the rivers damaged by the earthquake, two most severely damaged along the Yodo-gawa River are described. In the left levee, the settlement exceeded 2 m for a length of 1.4 km, with a maximum settlement of 3 m. Sand boils were observed extensively on the ground surface near the damaged dikes. Holocene sandy soil with an SPT N-value of 10 or less existed in the upper part of the subsoil profile. These facts indicate that liquefaction of the soil was the major cause of the embankment damage. The cyclic stress ratio required to cause liquefaction was 0.30 as determined from cyclic triaxial tests on undisturbed samples.
  • 黒川 美貴雄, 吉田 耕治, 永井 保嵩, 宇野 準
    Chemical and Pharmaceutical Bulletin
    1983年 31 巻 12 号 4312-4318
    発行日: 1983/12/25
    公開日: 2008/03/31
    ジャーナル フリー
    Two new partially saturated tricyclic ring systems,
    6
    ,
    6
    a,
    7
    ,
    8
    , 9, 10, 10a, 11-octahydro-11-oxodibenz [
    b
    ,
    e
    ] oxepins (3a and 3
    b
    ), and -thiepins (4a and 4
    b
    ) were synthesized. Compounds 4a and 4
    b
    were desulfurized to give a pair of isomeric 2-methylbenzoylcyclohexanes (10a and 10
    b
    ). Deuterated 4a and 4
    b
    (11a and 11
    b
    ) were prepared starting from butadiene-
    d6
    (12). The stereochemical features of 3a (trans), 3
    b
    (cis), 4a (trans) and 4
    b
    (cis) are compared with those of 10a, 10
    b
    , 11a and 11
    b
    on the basis of proton nuclear magnetic resonance data.
  • 金谷 守, 河井 正, 栃木 均
    地盤工学会論文報告集
    2001年 41 巻 6 号 79-96
    発行日: 2001/12/15
    公開日: 2008/02/29
    ジャーナル フリー
    In this paper, centrifuge shaking table tests were conducted in order to understand the performance of seawalls during a seismic event. The model tests showed that the displacement of the caisson was much affected by the seaward shear deformation of the sand seabed beneath it during shaking. It was also confirmed that an armored embankment played an important role in the displacement of the caisson during shaking. Based on these test results, a two-dimensional DEM-FEM coupled analysis method was newly developed to numerically predict the deformation of seawalls covered with armored embankments during earthquakes. The movements of the armor units were calculated by DE analysis and deformations of the caisson, rubble mound, sand seabed and backfill were calculated by FE analysis considering the non-linearity of the soil materials based on the effective stress. Dynamic interaction was taken into account by delivering the nodal displacements of the finite elements or the nodal forces converted from the contact forces through the imaginary distinct elements defined at the boundaries between the DE and FE domain. The applicability of this method to the prediction of the deformation of seawalls was verified through numerical simulations of the centrifuge model test.
  • 本城 勇介, 岩本 悟志, 杉本 三千雄, 鬼丸 貞友, 吉澤 睦博
    地盤工学会論文報告集
    1998年 38 巻 1 号 131-143
    発行日: 1998/03/15
    公開日: 2008/02/29
    ジャーナル フリー
    Seismic records obtained from a seismometer array located in downtown Tokyo Japan for about ten years were inversely analyzed to estimate the dynamic soil parameters. Due to the illposed nature of the problem, the simple and often used "least square method" does not properly estimate the parameters. The Extended Bayesian Method combined with the Akaike Bayesian Information Criterion was introduced to overcome this difficulty. The results obtained were compared with dynamic triaxial test results obtained at the time of the seismometer installation. The shear moduli agree quite well with the estimated results, however the damping ratios estimated are slightly higher than the ones obtained in the laboratory.
  • 関口 秀雄, 大槇 正紀
    土質工学会論文報告集
    1992年 32 巻 3 号 144-155
    発行日: 1992/09/15
    公開日: 2008/02/29
    ジャーナル フリー
    This paper concerns the stability against overturning of the caissons on rubble mound subjected to wave loading. A theoretical discussion is first made of the stability of a leaning caisson during wave loading, as a single degree-of-freedom system. The expression for the lower bound of driving moments sufficient to overturn a given caisson is derived. A review is then made of the damages induced to a composite breakwater, which consisted of two adjoining Stretches
    B
    and C with slightly different sizes of caissons. Attention is called for the observation that most of the caissons in Stretch
    B
    were overturned, whereas no caissons in Stretch C were brought into overturning. This fact is examined in detail in the light of the theory of overturning, making it possible to estimate the destructive wave heights that are compatible with the observed patterns of damage in Stretches
    B
    and C of the composite breakwater.
  • 松本 樹典, 武井 正孝
    土質工学会論文報告集
    1991年 31 巻 2 号 14-34
    発行日: 1991/06/15
    公開日: 2008/02/29
    ジャーナル フリー
    Stress wave theory is applied to open-ended pipe piles to clarify the effects of soil plug on the behaviour of piles during driving and static loading. Measured field data and various numerical models are reviewed ; methods are presented to calculate wave propagation in both the pile and the soil plug ; modelling is presented which takes into account the interaction between the soil plug and the pile ; also presented is simplified method to estimate the loadsettlement relation of the pipe pile in static loading. By correlating observed and calculated values in two analytical cases, the authors demonstrate that incorporation of the soil plug (modelled as a series of masses and springs) is required to correctly predict pile behaviour during driving and static loading.
  • PANOS DAKOULAS, HUMAYUN HASHMI
    土質工学会論文報告集
    1992年 32 巻 2 号 97-110
    発行日: 1992/06/15
    公開日: 2008/02/29
    ジャーナル フリー
    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.
  • 安原 一哉, 村上 哲, 豊田 紀孝 /, ADRIAN F.L. HYDE
    地盤工学会論文報告集
    2001年 41 巻 6 号 25-36
    発行日: 2001/12/15
    公開日: 2008/02/29
    ジャーナル フリー
    Based on the methods previously presented by the authors (Yasuhara et al., 1992, 1994, 1996) for predicting the degradation in strength and stiffness of soft clays in the course of cyclic loading, a methodology has been developed to estimate the cyclic loading-induced settlements. The method also includes not only immediate settlements but also post-cyclic long-term settlements due to dissipation of cyclically induced excess pore pressures in soft soils. The simplified formulae included in the proposed methodology are given as functions of the amplitude of cyclic-induced excess pore pressure normalized by the confining pressure, u/p'c, plasticity index Ip and factor of safety against bearing capacity failure, Fs. The calculations of cyclic-induced settlements were conducted for soft soil deposits with different index and geotechnical properties. The results calculated using the proposed methodology are presented in the form of a design chart to give the settlement versus normalized excess pore pressure ratio relations including the effects of the plasticity index and safety factor for bearing capacity. An example of the calculated results using the proposed procedure for the earthquake-induced settlements of embankments founded on soft clay, is presented to demonstrate the practicality of the method for design at fields.
  • 安田 進, 伯野 元彦, 永瀬 英生, 小林 正二郎, 吉田 剛
    土質工学会論文報告集
    1994年 34 巻 1 号 65-76
    発行日: 1994/03/15
    公開日: 2008/02/29
    ジャーナル フリー
    Shaking table tests were performed to clarify the settlement in liquefied loose sand of a new foundation incorporating top-shaped concrete blocks. In the tests, blocks of half scale were installed as they are in practice, by using a crusher-run, a lattice of iron rods and iron bars. Shaking table tests were also conducted on foundations with two differently shaped concrete blocks to investigate the effectiveness of the three foundations in reducing settlement. One was a T-shaped concrete block, or a disk-shaped concrete plate with a leg. The other was a conical concrete block without a leg. The results of shaking table tests showed that the foundation with the top-shaped concrete blocks was most effective in reducing the settlement among the three types of foundation. FEM elastic analyses were performed to compute the stress distributions in the models and in-situ ground when the top-shaped concrete blocks were applied and to confirm whether liquefaction resistance of the sand layer below the foundation is large. Moreover, the factor of safety against liquefaction, FL was evaluated in in-situ model ground, in order to compare with sensitivities against liquefaction in the ground without countermeasures and with top-shaped concrete blocks. For the liquefaction analyses, shear stress in the ground during an earthquake was estimated by dynamic analyses using the SHAKE computer program.
  • ANESTIS S. AVRAMIDIS, SURENDRA K. SAXENA
    土質工学会論文報告集
    1990年 30 巻 3 号 53-68
    発行日: 1990/09/15
    公開日: 2008/02/29
    ジャーナル フリー
    The original Drnevich Resonant Column apparatus has been designed for testing cylindrical soil specimen with maximum longitudinal and torsional stiffnesses corresponding to approximate resonant frequencies 285 Hz and 318 Hz respectively. This apparatus has been modified successfully and its stiffness has been increased to over threefold in the longitudinal vibratory mode and at least twofold in the torsional vibratory mode. Monterey No. O sand samples prepared at approximate relative densities 43% and 60% were tested with the original and the modified apparatus in the range of effective confining pressures from 49 kPa to 588 kPa. Measurement of dynamic moduli values measured with the original apparatus were up to 23% higher, and damping values up to five times higher than those measured by the modified apparatus.
  • 石原 研而, 長尾 哲
    土質工学会論文報告集
    1983年 23 巻 1 号 19-37
    発行日: 1983/03/15
    公開日: 2008/02/29
    ジャーナル フリー
    Using the so-called pseudo-static method, a stability analysis was made for the mountain slide that took place at Mitake-iriya village at the time of the Izu-Ohshima-Kinkai earthquake of January 14, 1978. Undisturbed samples of volcanic clay were obtained in blocks from the exposed surface of the deposit identified to have been the sliding surface. The partially saturated clay samples were tested under consolidated undrained conditions using the triaxial test equipment. Dynamic axial stresses with irregular time histories were applied to the specimens in combination with statically sustained axial stresses to determine the soil strength under the conditions simulating in-situ states of stress during the earthquake. The results of the tests were expressed in terms of the Mohr-Coulomb type failure criterion which showed that, while the angle of internal friction remained almost unchanged, the cohesion component in irregular loading increased above values obtained in the static loading. Using the strength parameters thus determined, a pseudo-static analysis was made to check the stability of the soil masses that had actually slid during the 1978 earthquake. The maximum horizontal acceleration required to cause the slide was computed. The computed accelerations were shown to cover a range between 400 and 500 gals which is consistent with the range estimated by other investigators on the basis of overturning of tombstones in the vicinity of the slide area.
  • 國生 剛治
    地盤工学会論文報告集
    2000年 40 巻 4 号 95-102
    発行日: 2000/08/15
    公開日: 2008/02/29
    ジャーナル フリー
    Field data indicate that the P-wave velocity in sand or gravel is sometimes much lower than that of water, even if the soil is below the water table. It is well understood that a slight decrease in saturation normally evaluated by the
    B
    -value has a significant effect on undrained shear behavior like liquefaction of saturated soil. In the first part of this research, theoretical formulations of the
    B
    -value, P-wave velocity and Poisson's ratio are made by taking into account the decrease in bulk modulus of water due to a mixture of air bubbles. Then, computations are carried out using formulas based on the soil properties of a typical sand or gravelly soils and Masa soil from the Kobe area to make charts correlating the variables. These charts indicate that a small decrement in the
    B
    -value in the interval of
    B
    =1.0 to 0.
    8
    will considerably decrease the P-wave velocity. Thus, the P-wave velocity which is easily measured in the field can serve as a convenient index to quantitatively evaluate the insitu soil
    B
    -value.
  • 黒川 美貴雄, 糸川 彰, 松本 純一, 福本 吉久, 月原 冨武
    Chemical and Pharmaceutical Bulletin
    1992年 40 巻 9 号 2270-2274
    発行日: 1992/09/25
    公開日: 2008/03/31
    ジャーナル フリー
    11-Amino-
    6
    ,
    6
    a,
    7
    ,
    8
    , 9, 10, 10a, 11-octahydrodibebenzo[
    b
    ,
    e
    ]thiepines (
    6
    a-d) and -oxepines (
    7
    a-d) were synthesized by the Leuckart reaction of
    6
    ,
    6
    a,
    7
    ,
    8
    , 9, 10, 10a, 11-octahydro-11-oxodibenzo[
    b
    ,
    e
    ]thiepines (1a,
    b
    )and -oxepines (2a,
    b
    ) followed by hydrolysis of the reaction products 4a-d and 5a-d, respectively. The four diastereomers, cis(
    6
    a-H, 10a-H)-cis(10a-H, 11-H)
    6
    a and
    7
    a, cis(
    6
    a-H, 10a-H)-trans(10a-H, 11-H)
    6
    b
    and
    7
    b
    , trans(
    6
    a-H, 10a-H)-trans(10a-H, 11a-H)
    6
    c and
    7
    c, and trans(
    6
    a-H, 10a-H)-cis(10a-H, 11-H)
    6
    d and
    7
    d, were isolated and their configurations and conformations were elucidated by chemical methods together with 1H-nuclear magnetic resonance spectroscopic and X-ray crystallographic analyses.
  • ROLANDO ORENSE, WILLIAM VARGAS-MONGE, JOSE CEPEDA
    地盤工学会論文報告集
    2002年 42 巻 4 号 57-68
    発行日: 2002/08/15
    公開日: 2008/02/29
    ジャーナル フリー
    An earthquake of magnitude
    7
    .
    6
    occurred in the south-east coast of El Salvador on January 13, 2001, causing widespread damage to buildings and several kinds of civil engineering structures due to ground shaking and earthquake-induced ground failures, including several large-scale landslides. This paper discusses the results of the damage investigation conducted in the area after the earthquake, with emphasis on the general features of the earthquake and its effects on the ground damage, specifically the landsliding which occurred in natural slopes and the liquefaction of soil deposits. The occurrence of liquefaction in the alluvial plain exhibited several characteristics in common with those observed in other areas of similar condition. On the other hand, the main cause of slope failures in volcanic deposits was not clearly identified, and several possible sources of slope instability were pointed out.
  • 増田 民夫, 安田 進, 吉田 望, 佐藤 正行
    地盤工学会論文報告集
    2001年 41 巻 4 号 1-16
    発行日: 2001/08/15
    公開日: 2008/02/29
    ジャーナル フリー
    This text is concerned with the basic principles underlying current practice in the earthquake response analysis of soft alluvial deposits. Its special interest is focused on the stratification of alluvium that has been modeled in analyses by layers in which soil properties are uniform. Since the age and the effective stress are continuous in the vertical direction, it is possible that the soil-dynamic properties such as shear modulus and damping ratio are not uniform but varying continuously in the vertical direction. From this viewpoint, the conventional idea of uniform layers was examined in detail by conducting detailed investigations in-situ, as well as laboratory tests on continuously collected undisturbed soil samples. The test results show that soil properties continuously vary in the vertical direction within an alluvium. This holds true even when the soil type changes from clayey to sandy. In contrast, a discontinuity of properties was detected at an unconformity of Pleistocene layers where the age and sedimentation process are discontinuous. With this knowledge, an attempt was made to propose a recommendable modelling of soil stratification for practical earthquake response analysis on alluvium.
  • JEANFRANCOIS SEMBLAT, MINH PHONG LUONG, GERARD GARY
    地盤工学会論文報告集
    1999年 39 巻 1 号 1-10
    発行日: 1999/02/15
    公開日: 2008/02/29
    ジャーナル フリー
    The Split Hopkinson Pressure Bar method (S. H. P.
    B
    ) provides a ready means for direct analysis of material dynamic response. Soil Specimens generally present poor mechanical properties, thus the classical experimental device has to be adapted. An original experimental arrangement "Three-Dimensional Split Hopkinson Pressure Bar" (3D-SHPB) is proposed. It allows measurement of the complete three-dimensional dynamic response of soils. Experiments are oedometric type tests (rigid confining cylinder) involving dynamic radial stress measurement. Pseudo Poisson's ratio is then determined and the influence of strain rate is shown. In addition, other types of confining systems are used : soft and semi-rigid confinement and low impedance tests are performed. Results on different loading paths are compared with others on sands and clays. Analysis at grain-size level gives further elements on the comminution process.
  • NEVEN MATASOVIC, MLADEN VUCETIC
    土質工学会論文報告集
    1992年 32 巻 3 号 156-173
    発行日: 1992/09/15
    公開日: 2008/02/29
    ジャーナル フリー
    The paper focuses on the development and modelling of residual cyclic pore water pressure, u, in clay during undrained cyclic strain-controlled loading. Data obtained from a series of NGI type cyclic simple shear tests were employed. In addition to the amplitude of cyclic shear strain, γc, the number of cycles, N, and the overconsolidation ratio, OCR, a new component is incorporated in the conventional characterization of u. This new component is the volumetric threshold shear strain, γtv, of clayey soils, below which for all practical purposes u does not develop. The lack of understanding of complex clay microstructure and the associated interaction between clay particles during cyclic shearing makes the modelling of u in a manner other than curve fitting rather difficult. This is especially true in regard to the development of negative u in overconsolidated clays. A model based on the systematic curve fitting of the pore pressure data expressed in terms of γc, γtv, N and OCR is presented. The possibilities of the incorporation of such a model into existing numerical tools for simulation of the seismic and ocean wave loading response of natural soil deposits are briefly discussed as well.
  • 安田 進, 永瀬 英生, 規矩 大義, 内田 泰
    土質工学会論文報告集
    1992年 32 巻 1 号 149-160
    発行日: 1992/03/15
    公開日: 2008/02/29
    ジャーナル フリー
    To study the mechanism of permanent ground displacement due to liquefaction, shaking table tests on 24 soil models were conducted. In these models, the slope of the ground surface, the thickness of a liquefied layer, the density of the liquefied layer and some other factors were changed. Permanent ground displacements did not occur at the boundary between the liquefied layer and the lower non-liquefied layer, but occurred in the liquefied layer with a constant shear strain. Relationships between the displacement and the thickness of the liquefied layer or the slope of the ground surface were also obtained. Then, vane shear tests and cyclic torsional shear tests were carried out to measure the rate of reduction of shear strength or shear modulus. By the cyclic torsional shear tests, it was clarified that the shear modulus decreases to a very small value due to liquefaction. Based on these test results, a simplified procedure for the analysis of permanent ground displacement was proposed. To confirm the accuracy of this procedure, it was applied to the models used for the shaking table tests and to typical soil cross sections of soil at Niigata City. Finally, some measures to prevent permanent ground displacement were discussed based on the shaking table tests and analyses.
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