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.

抄録全体を表示

In view of the significant role of the water film effect in flow failure for a liquefied sandy deposit, the mechanism of water film generation is numerically studied based on a 1-dimensional model test. The process of water film growth and decay can be simulated to a certain extent by a simple consolidation analysis, which indicates that only a small difference in permeability in layered sand is enough for a water film to develop. A 1 G shaking table test for a two-dimensional slope model with an arc of silt within a saturated sand is then addressed to discuss the dilatancy effect exerted in sheared sand during flow failure. It is possible that, once the water film is formed, the transmission of shear stress through it is interrupted, leaving the sand below free from the dilatancy ; this eventually allows the water film to stay without being absorbed during flow failure. The result of another shaking table test for a trapezoidal slope with horizontal silt seams indicate that water films beneath the seams enable the soil mass above them to laterally flow along water films very gently inclined even after shaking. If a silt seam breaks due to excessive pressure in the water film, it triggers re-liquefaction in the upper sand and leads to further instability.

抄録全体を表示

The paper illustrates theoretical and experimental procedures adopted to characterize the seismic response of earth dams by performance-based criteria. The study refers to a real case, the Camastra Dam, a zoned earth dam with vertical clay core, placed in a highly seismic zone of Southern Italy. At first, the analysis objectives have been identified along with the physical quantities needed to achieve them for characterizing dam seismic performance. A theoretical approach, consistent with the identified analysis objectives, has been later selected. The adopted approach is based on continuum mechanics and accounts for coupling between soil skeleton and pore water phase. It is also able to describe the main features of soil response under cyclic loading conditions since it implements an advanced constitutive law for the soil skeleton. Big effort has been paid to the mechanical characterization of the dam materials. In addition to data coming from the interpretation of the laboratory tests performed at the time of dam construction, in situ tests (SASW, Down Hole, DMT) have been recently carried out on the embankment and foundation soils and interpreted consistently with the requirements of the selected theoretical model. Preliminarily, the static stages of the dam lifetime have been numerically simulated to reproduce the behaviour observed in terms of cross-arm settlements and pore water pressures, in order to obtain or verify some soil parameters and initialize the state variables for the simulation of the seismic stages. A seismological study of the dam site provided the expected seismic scenarios in terms of time histories of acceleration, needed as input for the dynamic analyses. The seismic response of the Camastra Dam was finally investigated and discussed in the light of performance-based criteria.

抄録全体を表示

A crucial matter related to roads in seismic areas is to ensure viability during the post-seismic stages, especially if the road represents an important or unique way to reach towns that may be potentially hit by strong earthquakes. Verification of road viability under seismic actions requires not only safety assessment of the failure mechanisms which may jeopardize single road components (embankment, viaduct, bridge, etc.) but also evaluation of performance. Viability of a road may be compromised by an unsatisfactory response of road embankments. The vehicle flux may be, in fact, inhibited or reduced if a road embankment suffers global instability mechanisms or significant permanent displacements mainly at the contact with structural elements (.g., viaducts, bridges) that do not move significantly. In this case the embankment permanent displacements turn out into steps or separations. The paper accounts for the different stages followed to study the seismic performance of the road embankments located along a sample road branch of about 5 km. Preliminary activities consisted in characterizing the geological area of the sample road, in selecting the potentially vulnerable embankments and in carrying out in-situ investigations to properly characterize the physical and mechanical properties of the embankments and foundation soils. A seismological study of the sample area was performed in order to characterize the reference seismic actions needed for the numerical analyses. The seismic response of the embankments was evaluated by a pseudo-dynamic approach and an advanced dynamic model. In the latter, the equations describing dynamic equilibrium and compatibility were merged with an elastoplastic combined-hardening constitutive law that properly models soil response under cyclic loads. The embankment's seismic performance was predicted in terms of permanent settlements at the embankment top surface versus the peak acceleration of the reference input motions.

抄録全体を表示

The filtration compatibility of soil-geotextile systems has been assessed experimentally in the laboratory with the gradient-ratio test. A nonwoven geotextile was used against a variety of model soils that were prepared from glass beads. They exhibited a range of fines content, in both gap-graded and broadly-graded size distributions. Filter blinding and clogging, if it happens, occurs within hours of initiating unidirectional flow. The zone of soil above the geotextile that is influenced is relatively thin. In gap-graded soils, the movement of fine particles appears to occur at a conditioh of />. A new dimensionless index is proposed to quantify the internal stability of gap-graded soils.

抄録全体を表示

In the 1993 Kushiro-oki Earthquake of Richter magnitude ., 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.

抄録全体を表示

The resistivity tomography, the horizontal electrical profiling, and the elastic wave tomography methods were used for evaluating an improved area in gravelly soils by chemical grouting. The first and second methods are basically the same; however, the second method is much easier to perform. The availability of the second method is also investigated. The improved area was confirmed by excavation after grouting. The actual improved area was compared with the area estimated by using the above three methods. Among them, the resistivity tomography method could nearly estimate the grouted area in cooperation with the analytical method used by Komine et al. It was, however, difficult to evaluate the grouted area by either the horizontal electrical profiling nor the elastic wave tomography method in the present case.

抄録全体を表示

A series of permeability tests on both high-quality undisturbed samples and reconstituted samples was performed using a large-scale triaxial cell. Based on the test results and discussion, the following conclusions were noted. (1) The coefficient of permeability in the horizontal direction is larger than that in the vertical direction. However, its difference is between 10% and 70% and not so large. (2) The coefficient of permeability decreases with increasing confining stress. The effect of the confining stress can be understood as the effect of the void ratio. And the small change of the void ratio due to consolidation only leads to a small change of the coefficient of permeability. (3) There is no clear correlation between the physical properties and the coefficient of permeability. () The coefficient of permeability of gravelly soils is almost the same as that of sandy soils, even though the 50% diameter of gravelly soils is about ten to a hundred times that of sandy soils. This result implies that the large size particles of gravelly soils have no significant effect on permeability characteristics of gravelly soils. (5) A new definition for determination of , and fines content only from those soil particles with a diameter smaller than 2mm was introduced. A correlation similar to sandy soils can be seen between the coefficient of permeability and , , and fines content based on the new definitions. (6) The effect of the small size particles of the gravelly soils on the coefficient of permeability was found significant based on the test results using samples with a special blend of particle size and density reconstituted from undisturbed samples. () The coefficient of permeability of multi-layer gravelly soils, in the direction perpendicular to the sedimentation, was significantly affected by the lowest permeability. And the coefficient of permeability of the multi-layer in total agrees well with the theoretical estimation. () Although the data is limited, there was no significant different of coefficient of permeability between undisturbed and reconstituted samples. This result accords with that reported for sandy soils by Hatanaka et al. (1997). This result also means that the coefficient of permeability of gravelly soil is not affected by the soil fabric. As a result, the in-situ coefficient of permeability of gravelly soils can be well estimated for practical purposes from the reconstituted samples with the same gradation properties.

抄録全体を表示

In order to establish a physical model leading to stable (uniform) and unstable (non-uniform fingering) flows in unsaturated soils, two-dimensional tests on continuous rainfall infiltration were carried out by changing not only the initial water content (air dry, 0.5%, 1.0%) but also the rainfall intensity (15, 30, 180 mm/h). The physical mechanism of fingering flow was discussed on the basis of precise suction measurements inside and outside the fingers. The results show that wetting fronts developed in unsaturated sandy soils can be classified into three types ; 1) fingering flow, 2) wavy front, and 3) plane front. Two types of fingering flow can be further distinguished by the difference of the swelling velocity ; i. ., low-swell finger and high-swell finger flows. In each of the low-swell and high-swell fingers, a core and a swelling zone are developed while a finger is growing. Based on suction measurements inside them, it is found that the water condition in the finger core changes from wetting to drying processes while the water condition in the swelling zone remains in the wetting process. This hysteretic behavior in the core can be explained by the moisture distribution changing along a finger from tip to tail. Fingers swell when water moves from a finger core to surrounding dry sand. Such a swelling process is mainly controlled by the hydraulic conductivity for the wetting process at a finger tail.

抄録全体を表示

One method currently being considered for the disposal of high level radio-active waste is burial in the seabed. When a hot object is buried in soil, the temperature of the soil adjacent to the object is raised and there is transient heat flow away from the object. The rise in the temperature of the soil causes excess pore pressures to be generated and transient pore water diffusion also takes place. A finite element formulation of the coupled heat flow and consolidation problem is presented. The computer implementation of this formulation is found to compare favourably with analytical solutions based on the same physical principles.

抄録全体を表示

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.

抄録全体を表示

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.

抄録全体を表示

[1] The purpose of this reserch is to make clear what type of design can give good effects to win the high readership score. At the begining I had to know what factors decide the readership score, and how to change the quality of the desing into numerical value. I have used the method of multi-dimentional analysis with the help of a computer, and got the estimation formula, with kinds of factors, as follows ; A^^〜=+C++K+aE++cG. A^^〜=estimated values of the readership score. 1) , C, , K : these four factors are given as category values (so we call them); each factor is classified into several categories. =week day, classified into categories. C=pages of a newspaper, which are characterized by the kinds of articles, news, and the other reading matters, classified into categories. =kinds of goods and trades of the advertizement, classified into 14 catedories. K=constants, given to each 13 surveys. 2) , F, G : these factors are given as numerical values. G=area of advertizement, measured by the unit of column in the whole page length, being classified into 6 kinds of area (2.5, 3.5, 5, , 10, 15) and 15 column means a whole page, about 2,000cm^2. , F are the marks obtained in the design of advertizements. =sum of the marks obtained in each design element on the advertizement. F=the marks obtained on the whole effect of the design. 3) a, , c : coefficients Using the above formula with the category values and the coefficients, we can obtain the naked design effect from the actual value A of readership score: aE+=A-(+C++K+cG). In this research, I used 1,829 data of readership score from 1960 to 1968, being obtained by 13 survevs, spring and autumn twice a year. The sample of size each survey was 3,541, 2,251, or 200 in the other 11 surveys. Multiple correlation coefficient between the estimated value A^^〜 and the actual value A is 0.951. The table 2^* shows the contribution indexes of each factor by 3 kinds of expression-(1) Range : the absolute difference between the maximum and the minimum category values, (2) Standard deviations of the category values, (3) Partial correlation coefficient : the relationship between the actual values A and each factors. *see the table 2 in the thesis in Japanese. [2] The important point was in the determination of the values of , F. is the sum of the marks obtained in each design element, classified into four kinds : =_1+_2+_3+_. design elements [table] _1, _2, _3, _, these values have the 5 grades, as 0, 1, 2, 3, and 0 is given to the design that has no attractive effect or no applicable element. And obtain the marks of 0 to grades as the sum of them. The values of F have also 5 grades, 0 to . The principles to determine the values of , F are as follows : a) The marks obtained of , F must be the relative values among the each survey, and at the same time, they must have constancy within the same survey-the same elements of design must win the same marks obtained. ) They must be determined as to win the highest multiple correlation coefficient, when they are put into the estimation formula. c) They must be reasonable. In order to justify them, we must carry many researches on the actual condition. The frequency of accurence of each grade of , F values, as the table 5-, and 5-5 in the thesis in Japanese.

抄録全体を表示

An investigation into the base capacity of piles in passing through loose, liquefiable sand and founded in underlying dense sand is presented based on the results of a series of dynamic centrifuge tests on instrumented model pile groups. Excess pore pressures equal in magnitude to the initial effective vertical stress were observed to be generated in the bearing layer of dense sand at both shallow (15 m) and deep (26 m) depths. This induced a dramatic reduction in base capacity and consequently, large settlements of the piles by as much as ~. A spherical cavity expansion solution for base capacity was validated against measured values showing good agreement, provided that excess pore pressure and dynamic shear stiffness in the bearing layer are known. A simple closed-form relationship, applicable to end-bearing piles, between the degree of liquefaction and the initial pile static safety factor was then developed against plunging failure at the pile base which can be used in design.

抄録全体を表示

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 I_p and factor of safety against bearing capacity failure, F_s. 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.

抄録全体を表示

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, F_L 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.

抄録全体を表示

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.

抄録全体を表示

From the fronds of Polystichum tripteron (KUNZE) P_R. a new norcarotenoid glycoside was isolated and shown to be (6R, , R)--hydroxy-megastigma-, -dien-3-one--O-β--glucoside. The fronds of Dennstaedtia wilfordii (MOORE) CHRIST. contain the same glucoside.

抄録全体を表示

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, () 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.

抄録全体を表示