A semi-empirical expression has been derived for the fundamental period of large earthfill and rockfill dams. Derivation is based on analytical solutions and has been calibrated using the empirical data available. Analytical solution involves a heterogeneous shear wedge with a realistic distribution of small-strain shear modulus. The effect of the "third dimension" has also been taken into account by making use of two and three dimensional finite element and shear wedge solutions, and a simple expression has been derived by the aid of a single degree of freedom idealization. Empirical data come from forced vibration tests and response observations during small earthquakes. Recently the fundamental period of a large rockfill dam became available which had not been used in the development of the period expression presented. The accurate prediction of the period of this dam has shown that the equation will be useful in practice for estimation of the small strain fundamental periods of large dams.

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The results of investigation of soil liquefaction and related damage to several structures during the Haicheng earthquake of 1975 (M=7.3) and the Tangshan earthquake of 1976 (M=7.8) in China are described. Extensive soil liquefaction occurred during these two earthquakes especially in the sandy deposits of the Holocene period and in the abandoned old river beds. Numerous bridges, buildings, embankments and others were seriously damaged due to soil liquefaction. The maximum ground acceleration at liquefied sites were estmated 100 gals or more. The maximum epicentral distance R_max (km) of liquefied sites for these two earthquakes were well represented by the equation ; log₁₀R_max=0.77M-3.6 in which M is the earthquake magnitude. This equation has been proposed for fourty four Japanese earthquakes in the past. Some discussions were made on the method of evaluation of liquefaction potential using the standard penetration test N-values or the static cone penetration test q_c-values.

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A series of drained triaxial compression tests at extremely low pressures was performed on saturated samples of fine, angular sand to know the dependency of both the angle of internal friction φ=arcsin {(σ₁'-σ₃')/(σ₁'+σ₃')}-<max> and the deformation characteristics on the value of σ₃'. Great cares were paid to the stress measurements and the stress corrections for membrane forces. Also in order to confirm the results with respect to the value of ψ, several analyses based both on the stress-dilatancy relations at failure and on the deformation characteristics of sample were performed. It was found that the change of φ with the change of σ₃' is very small when σ₃' is lower than around 0.5 kgf/cm² (50 kN/m²), especially lower than around 0.1 kgf/cm² (10 kN/m²). It was also found that the apparent cohesion intercept is not needed in using the Mohr-Coulomb failure criterion for the saturated sand tested. Further, it was found that the change of deformation characteristics of sand with the change of σ₃' is rather small when σ₃' is lower than around 0.5 kgf/cm² as well.

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Despite numerous experiences of serious earthquake damages, little knowledge has been obtained about dynamic failure mechanism for sloping embankments constructed in narrow valleys. A fundamental study by means of a series of model tests followed by several analyses was performed to clarify dynamic failure characteristics of V-shaped sloping embankments subjected to impulsive loadings. A simple test equipment system has established to provide the embankment model made of wet sand with well-controlled impact loads. The system is capable of producing an impulsive inertia force with a triangular waveform, and giving rise to a three dimensional failure mass in the embankment. Accelerograms observed on the failure mass are found to give a truncated waveform with an abrupt drop at the end, as well as concavity associated with three dimensional geometry of the failure mass. Yield acceleration read off the truncated accelerograms shows a remarkable increase with a decrease in a width to depth ratio of the embankment, demonstrating restraining effects of the valley walls. Stability and relative displacement are calculated for imaginary tetrahedral failure blocks to compare with the yield acceleration and observed settlement, respectively.

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The estimation of settlements of foundations on granular soils requires both a mechanical model for the footing on the soil and an appropriate method for evaluating soil parameters. Both aspects are considered. In the usual case the loads are mainly monotonous and remain below the failure load with an adequate margin of safety. Observed settlements of foundations show considerable scattering. A general trend, however, can be recognized : The settlement per contact pressure increases somewhat with the breadth of the footing. This observation is compared with the predictions of different soil models. The best model is shown to be a heterogeneous half-space whose modulus increases with the square root of depth. The modulus has elastic and plastic features which need not be considered separately. The settlement of larger footings can be fully explained by the well-known behaviour of sand under one-dimensional compression. Applying dimensional analysis to the footing on this heterogeneous half-space yields results that permit consideration of the form of the contact area and of mutual dependence of adjacent footings. The factor inherent in all calculated results is determined by a comparison of observed settlements with Standard Penetration Test data.

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Normally consolidated clays generally have such a strength profile that the undrained strength increases nearly linearly with depth. The current paper describes a method of preparing normally consolidated clay layers of which undrained strength increases linearly with depth. The gradient of the increase of undrained strength which the authors intended to create in clay was in the range between 110 and 240 kN/m²/m.Kawasaki clay with plasticity index of 26.9 was preconsolidated on the lab floor under a small surcharge pressure of either 9.8 or 19.6 kN/m². The preconsolidated clay was then consolidated with some surfcharge pressure under a centrifugal acceleration of either 40 or 80 g. The surcharge pressure was applied by introducing equal air pressures into three rubber bags installed on the surface of the clay. The magnitude of the pressure was made equal to the preconsolidation pressure on the lab floor to keep the whole layer in the state of normal consolidation.The degree of consolidation after 24 hour-continuous run of the centrifuge was approximately 90%. The change of pore pressurs during centrifuge consolidation was monitored with 5 to 6 pore pressure transducers embedded in the clay. The variation of pore pressures with time predicted by the one-dimensional consolidation theory compared well with the observations. The post-mortem check of the clay revealed that water contents in the clay increased nearly linearly with depth and agreed also well with the theoretical prediction, showing the advantage of the use of centrifuges in preparing normally consolidated clay layers.

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In order to study the deformation-strength behaviour of soft sedimentary rock "Shirasu" derived from pyroclastic flows, drained triaxial compression tests were performed on undisturbed specimens prepared by cutting and trimming from block samples. The specimens were tested with the direction of applied major principal stress inclined at various angles to a bedding plane. An inherent anisotropy in the shearing behaviour of Shirasu was studied from the test results. The anisotropy was dependent on the dip of stratum and the confining pressure related to grain orientations and grain movements during consolidation and shearing. The effect of anisotropy on the shearing behaviour was remarkable under a low confining pressure and disappeared under a high confining pressure. That the shearing strength of sedimentary rocks depends on the direction of the major principal stress at failure and the stress level requires a special attention for the choice of the strength parameters in practical problems.

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This paper presents a numerical procedure in which the soil parameters affecting the two dimensional consolidation are back-calculated from the data monitored in the field. By using a combination of finite element method and mathematical programming technique, the procedure allows to seek the unknown soil parameters which minimize the differences between calculated and measured quantities. Young's modulus, Poisson's ratio, and permeability coefficient in multiple soil layers are the soil parameters determined by the procedure. The validity of the proposed procedure is verified by calibrating the performance of the procedure being applied to hypothetical case studies. The applications to practical projects provide the interesting results such as the changing trend of soil parameter values during consolidation process. By applying the procedure at the early stage of consolidation, one may be able to predict the future settlements with a good accuracy.

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In this paper the authors report on the dynamic active pressure distribution behind a rigid wall rotating about the top and arrive at the following conclusions. (1) The dynamic active pressure distribution behind the wall rotating about the top is non-linear and the magnitude of these pressures approaches zero at the base of the wall. Soil arching effects appear to increase the magnitude of the dynamic active pressures at the top one third portion of the wall. (2) The dynamic pressures at the top of the backfill are non-zero and the magnitude of these surface pressures increase with increasing acceleration levels. (3) The location of the point of application of the total dynamic active force is at 0.55 H from the base of the retaining wall, and is independent of the input acceleration levels. Based on their experimental findings using the University of Washington shaking table, the authors also propose a procedure for the design of such retaining structures in seismically active regions.

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For the support of retaining structures, the use of anchors is often requied. A sizeable number of these are either block anchors or multibell anchors with the enlargement of the section at predetermined locations. The pullout capacity of a block anchor normally depends very much on the peripherial friction on its shaft whereas that of a multibell anchor is predominantly dependent on the earth pressures on the faces of the bells. A laboratory-scale investigation was undertaken to study the effect of anchor length on friction, and therefore pullout capacity, on horizontal block and multibell anchors at different embedment depths in sand. The behaviour of multibel and block anchors in purely granular soils was also investigated by means of a two-dimensional pin model analogy and the patterns of the soil flow at failure were qualitatively examined in line with classical plasticity theories. Results obtained from tests in sand showed that for anchor lengths up to forty diameters, the shaft friction of a block anchor increases linearly at each embedment depth considered. A factor α applied to relate the measured friction with that obtained analytically was constant for lengths exceeding a minimum at each depth. α increased sharply for decreasing lengths less than this minimum. The increase in capacity of the multibell anchor was compared with that of a block anchor. A factor β which was the ratio of the multibell friction to block friction was found to be constant for lengths greater than the minima above. For decreasing lengths less than the minima, β decreased.

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A large continuous sample of a saturated sand to a depth of about 10 m was successfully obtained in Niigata, Janan, by means of an in situ freezing method, and so-called undisturbed samples of the sand were obtained by a conventional triple-tube sampler. Unidirectional freezing tests were conducted in the laboratory to determine the minimum confining pressure for preventing expansion during freezing. Undrained cyclic triaxial tests were conducted on the specimens prepared from the samples of dense sand from a depth of about 9.5 m after they had been thawed under isotropic stress conditions as well as on specimens reconstituted at the same density as the in situ frozen sample. An attempt was made to estimate the undrained cyclic shear strength in the field based on the laboratory tests, and the result was compared with probable field behavior at the site during the Niigata earthquake of 1964. Based on the above studies it was shown that (1) the quality of the in situ frozen sample was judged quite good ; (2) compared with the undrained cyclic strength of the in situ frozen sample, that of the triple-tube sample was only about 30%, and that of the reconstituted samples was about 30 to 60% ; and (3) the ratio between the undrained cyclic strength and consolidation pressure for the in situ frozen sample markedly increased with a decrease in the consolidation pressure.

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