An analytical method is developed for the distribution of the earth pressure against a retaining wall caused by an earthquake loading for any mode of wall movement, based on Dubrova's model of redistribution of pressure.Dubrova's method for static loading is extended for earthquake loading. Rotation of the failing retaining wall about any point is considered. For such case of failure mode, the slope of the failure line is determined, together with the point of application of the total force, which is useful for design purposes. Moreover, the pressure distribution and the critical direction of the earthquake loading is computed. Several conclusions are reached for the failure mechanism which may assist in proper design of retaining walls.The results of this study are in fair agreement with experimental observations.

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In order to explore the nature of cyclic loading in seabed soil deposits due to travelling waves, an analysis was made to determine the stresses in an elastic half-space subjected to continuously distributed sinusoidal loads on the surface. The result of the analysis showed that the cyclic loading generates an alternate changeover of two components of shear stresses, i. e., the horizontal shear stress and the stress difference between the vertical normal stress and horizontal normal stresses. It was further shown that the alternate changeover in stresses as above takes place in such a way that the principal stress axes continuously rotates while holding the deviator stress (difference between two principal stresses) at a constant level. In an attempt to simulate the actual stress conditions as above, a triaxial torsion shear test apparatus was manufactured, and controlled combinations of torsional and vertical stresses were applied so that the same nature of cyclic loads as described above could be applied to hollow cylindrical sand specimens prepared in the test apparatus. The test results showed that, even when the amplitude of the combined shear stress (deviator stress) is maintained constant, the plastic deformation as represented by the pore water pressure build-up could take place in the sand, if the rotation of the principal stress axes is executed during the cyclic loading test, and consequently the cyclic strength of sand is reduced, as compared to the cyclic strength obtained from the conventional type of cyclic triaxial test apparatus.

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Recently, several large-scale tunnels, such as the Seikan undersea tunnel and the Haruna-Nakayama tunnel, have been excavated for the Japanese railway system. One of the most important problems related to the tunneling projects concerns groundwater behavior and seepage around the tunnel. The intent of this paper is to clarify the fundamental character of tunnel discharge hydrograph by analyzing groundwater movement and water balance in terms of hydrology.

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The paper discusses the effects of non-linearity in the failure criterion of soil on the upper bound solution procedure. By considering the inherent non-linearity of the failure criterion, it is demonstrated that the upper bound procedure yields not only the minimum value of and the external load and the failure mechanism, but also the stress distribution along the slip surface. The stress distribution so obtained satisfies a Kotter type differential equation and guaranties the global equilibrium of the sliding mass. This result is valid for both linear and non-linear failure criteria. When the failure criterion is linear, it is demonstrated that for a simple failure mechanism the classical solution procedure provides only a partial solution which does not include the normal stress distribution. This is due to the different consequence of the normality requirement in the linear and non-linear cases.

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A simplified method of evaluating pore pressure behaviors of earth dams during construction was proposed in the present paper. The basic scheme of the method is similar to that presented by Eisenstein et al. (1976), but some simplifications were introduced in the part of consolidation analysis. The main advantages of the method are to estimate generated pore pressures from the results of conventional oedometer tests and to evaluate pore pressure dissipation by using the relationship between the degree of consolidation U and the time factor T in one-dimensional consolidation. Concerning the latter, it is recommended here that U-T relationships be composed from pore pressure measurements in the field, because it is not necessarily sufficient to represent such field consolidation conditions as anisotropic permeability and the difference in drainage systems through laboratory tests. In the comparisons between computed and observed results for three representative earth dams, it was noticed that the present analytical approach on the whole showed good correspondence with pore pressure behaviors in actual dams, offering sufficient accuracy for practical purposes.

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A critical review of field performance of sandy soil deposits during past earthquakes is conducted with special emphasis being placed on Standard Penetration Test N-values and fines content. The field relationship between adjusted dynamic shear stress ratio and normalized SPT N-values together with laboratory tests on undisturbed sands indicate that (1) sands containing more than 10 percent fines has much greater resistance to liquefaction than clean sands having the same SPT N-values, (2) extensive damage would not occur for clean sands with SPT N₁-values (N-values normalized for effective overburden stress of 1 kgf/cm²) greater than 25, silty sands containing more than 10 percent fines with SPT N₁-values greater than 20, or sandy silts with more than 20 percent clay, and (3) sands containing gravel particles seem to have less resistance to liquefaction than clean sands without gravel having the same SPT N-values.On the basis of the above findings, an improved empirical chart separating liquefiable and non-liquefiable conditions is presented in terms of dynamic shear stress ratio, SPT N-values, fines content, and shear strain amplitude.

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An approximate and economical method is presented that can analyze dynamic interaction of piles. The method is based on a beam-on-Winkler foundation model of a pile group. Discrete soil-pile interaction elements (springs and dashpots) for the method are determined by superimposing responses of two dynamically interacting piles in a homogeneous and linearly elastic soil.The proposed method is evaluated through a case study of seismic response of an actual pile-supported building. Computed results are compared favorably with field observational data. This indicates that the stiffness and damping characteristics of a pile group can be represented reasonably by the method. Thus the method provides an economical means to evaluate dynamic response characteristics of complex pile groups in layered soils.

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A constitutive equation for soils is presented that describes the deformation and strength characteristics of soils in three-dimensional stresses. A stress-strain relationship under shear was developed introducing an extended concept of "Spatial Mobilized Plane" (named the concept of SMP^*). In the present paper, paying attention to the fact that the dilatancy of soils under anisotropic consolidation is similar to that under shear, a stress-strain relationship under consolidation is obtained on the basis of the concept of SMP^* in the same way as the stress-strain relationship under shear. By combining these two stress-strain relationships and the stress-strain relationship in the elastic state, a generalized constitutive equation is formulated. The validity of this proposed constitutive equation is checked by the analysis of various kinds of element tests and its comparison with the experimental results. All the soil parameters of the proposed constitutive equation can be determined from shear and consolidation tests by using a conventional triaxial compression test apparatus.Finite element analyses for bearing capacity problems are then performed by using the proposed constitutive equation. The analytical results explain well various deformation and failure behaviors of soil foundation which have been well-known empirically.

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Alluvial clay, widely distributed throughout the world, is generally in an overconsolidated state. The phenomenon occurs in spite of the fact that the clay has not undergone stress release. This is attributed to development of an additional structure induced by aging. In this paper, the overconsolidated state of three alluvial clays found in Tokyo Bay, Singapore, and the Arabian Gulf are presented as well as a discussion of the causes of overconsolidation and the formation process of each clay.Characteristics of overconsolidation caused by aging such as secondary compression, chemical bonding, and desiccation stress are first discussed. Effective overburden stress, σ^^-_υo, consolidation critical stress, σ^^-_c, and overconsolidation ratio, OCR, of the three clays are presented. Causes of overconsolidation and the formation process of each clay are evaluated from 1) the σ^^-_υo-σ^^-_c-OCR relationship, and 2) the changes in sea level from deposition to the present. It is concluded that 1) chemical bonding, 2) secondary compression, 3) cementation, 4) oxidation, and 5) desiccation stress are the causes of overconsolidation in the three clays.

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In seismic engineering practice it is extremely important to seek confrontation of theoretical analysis with field observations. Japan being one of the countries of high seismic activity and one of the leading countries in seismic investigations, has installed recently reliable seismic observational stations, to obtain a better understanding of this complicated phenomenon, to the benefit of the engineering profession.The basic ideas and assumptions to solve foundation seismic problems play a very important part to achieve more accurate practical solutions when thay are clearly supported by field observations. Since, this is the only way the engineer may develope confidence in the methods of analysis and theories.The aim of the paper is therefore, to compare a theoretical method of analysis developed by the author based on two simple working hypothesis, with the seismic field pore water pressure measurements performed in "Owi Island", Japan. The theoretical analysis was performed with data of the site furnished kindly to the author by Professor Ishihara.The method of analysis is briefly described in the paper and the results compared with field observations. The author found a fair agreement between the results of his analysis with the field observations of the seismic pore water pressures. The author suggest, however, to verify the method proposed over again whenever reliable seismic field observations are available in the future.

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Earthquake-induced deformation of an existing earth dam was evaluated by a simplified method and finite element method, and the predicted settlement of the crest of earth dam by both methods well agreed. Material of the earth dam was non-liquefiable and dilative soil, and the earthquake-induced accumulation of deformation was calculated. Both methods employed the stress-permanent strain relationships determined by cyclic triaxial tests which were performed under the condition of existence of initial shear stress. The static initial shear stress exists in the earth dam, and earthquake loadings cause the large accumulation of deformation in soils only if the initial shear stress exists.

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