Dredged clay in land reclamation undergoes finite strain and considerable change in permeability and compressibility. Realistic predictions of consolidation behaviour of soft to extremely soft clay can be achieved using a finite strain formulation with varying permeability and compressibility instead of conventional Terzaghi's small strain theory. Such a formulation is developed using a theory which couples the interaction of solid and fluid. The material non-linearity is incorporated by piece-wise linear e-log σ' and e-log k relationships. The effect of initial void ratio profile on the settlement and pore pressure behavior is investigated. The significance of finite strain analysis is highlighted through two case studies associated with reclamation projects. Predictions by the proposed method of analysis compare well with field results in terms of settlement and void ratio distribution.

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Statistical properties of undrained shear strength c_u are investigated through laboratory and in-situ tests. In laboratory, a series of unconfined compression tests and triaxial UU tests are performed using mixed soil samples. Concerning in-situ soil samples, comparative study is made between disturbed and undisturbed soil specimens. Following findings and method are obtained : (1) When plasticity index I_p is greater than 15%, the difference of c_u between unconfined compression test and triaxial UU test is less than 2% and is almost negligible. However, when I_p is smaller than 15%, unconfined compression test always provides smaller strength than triaxial UU test. c_u of unconfined compression test is about 15% smaller than that of triaxial UU test when I_p≒10. (2) Concerning the coefficient of variation of strength V(c_u), however, there is no significant difference between these two testing methods. Moreover, V(c_u) is found almost independent of both plasticity index and consolidation pressure. (3) When soil specimens are disturbed, the mean value of q_u becomes small while the coefficient of variation becomes large. In the case of E₅₀, however, the coefficient of variation holds constant during disturbance procedure. (4) The method of predicting statistical values of strength of undisturbed specimens from those of disturbed samples is newly presented.

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The movement of single rigid solid vertical model piles and pile groups under eccentric, inclined as well as axial and horizontal loads are experimentally investigated. From displacements of single piles in sand and clay the vertical and horizontal secant moduli of soil are evaluated by relationships based on elastic theory. It is found that changes in the loading eccentricity cause induced anisotropy in sand. The values of secant moduli of sand and clay from pile tests are compared with the values obtained from laboratory plate bearing tests. The ratio of vertical to horizontal secant moduli of sand agrees well with the value of the same from triaxial tests reported elsewhere. The ratios of secant moduli to the undrained shear strength of clay also lie within the range of values given by other sources. Effects of grouping of piles on movements are analyzed by displacement and rotational ratios determined from tests. These ratios are compared with their experimental values given by Oda (1972). The method of pile installation and soil density are found to have significant influence on the displacement and rotation ratios from pile tests conducted in sand.

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A method of measuring the shear wave velocity in a triaxial test specimen (300 mm in diameter, 600 mm in height) has been proposed. The validity of the measurement method and the characteristics of the detected waves were confirmed by conducting preliminary tests on a steel cylinder and Toyoura sand specimens. By applying this method, the velocities of the shear waves propagating in the 'undisturbed' samples which were obtained from diluvial gravel deposits by means of an in-situ freezing method were measured under various confining pressures. The results of these measurements indicated that the effect of confining pressure on shear wave velocity was more significant for diluvial gravel samples than for clean sand, and that the shear wave velocities in reconstituted gravel specimens at in-situ overburden pressure were 20 to 30 percent below those in diluvial gravel samples. The shear moduli at a strain amplitude of l0^-5 in cyclic triaxial tests were about 5 percent less than those determined from measurement of shear wave velocities. Moreover, it was verified that laboratory shear wave velocities in diluvial gravel samples were nearly equal to in-situ shear wave velocities measured at the sampling site, in the range of K₀ equal to 1.0 to 2.O. From this fact, it was concluded that the disturbance of the diluvial gravel samples was very slight during the entire sampling procedure.

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A review of field liquefaction behavior during several recent earthquakes was made with emphasis on the Cone Penetration Test (CPT) q_c-values and the grain size of the soils. The field correlation between the earthquake-induced cyclic stress ratio and normalized cone resistance indicates that fine-grained soils with a mean grain size of D₅₀<0.25mm have greater resistance to liquefaction than do clean sands (D₅₀≥O.25mm) having the same q_c-values. On the basis of this finding, we have developed a liquefaction assessment method for soils using the CPT. The normalized critical value of the CPT, (q_c1)_cr' which separates liquefiable from nonliquefiable conditions, is defined as a function both of the cyclic stress ratio, and the mean grain size of a soil. A simple chart showing variation in the critical CPT value, (q_c)_cr' with depth was developed for various earthquake magnitudes, maximum surface accelerations and ground water levels. Our proposed CPT-based liquefaction assessment method was evaluated by data on the known performance of soils in the field.

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The Nihonkai-chubu Earthquake, with a magnitude of 7.7, occurred on May 26, 1983 in northwest Japan and produced liquefaction sites in the coastal plain of Akita and Aomori Prefectures. About one month later, the maximum aftershock, with a magnitude of 7.1, again induced liquefaction at several sites in Aomori Prefecture. The authors surveyed the affected area and discovered almost ten reliquefaction sites. Initial liquefaction at these sites had not occurred solely because of the main shock of the Nihonkai-chubu Earthquake. Initial liquefaction at some sites was attributable to the Niigata Earthquake in 1964, the Tokachi-oki Earthquake in 1968, and other earlier earthquakes. Although it had earlier been thought that the occurrence of reliquefaction would be improbable, the authors' investigation shows that reliquefaction occurs frequently, even when the acceleration caused by a later earthquake was less than that caused by a former earthquake. It can therefore be said that a site liquefied by an earthquake can be reliquefied by a subsequent earthquake.

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The critical intensity of earthquake ground motion which separates liquefiable to non-liquefiable conditions is investigated. The peak ground acceleration and velocity are calculated at about 130 liquefied and non-liquefied sites during 19 Japanese earthquakes. These sites are on natural levee, river channel, reclaimed land or drained land, and have high liquefaction susceptibility. In the calculation, the effects of fault rupture and local site condition are considered, to obtain more accurate results than those in previous studies. The results of the calculation indicate that (1) the occurrence of soil liquefaction is better correlated with the peak ground velocity than with the peak ground acceleration, (2) soil liquefaction is likely to occur for the ground with high liquefaction susceptibility, when the peak ground velocity exceeds 15 kines (cm/s), and (3) the degree of soil liquefaction shows no clear correlation with peak ground velocity or acceleration.

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Investigated from a fundamental point of view is the strength of granular material in simple shear. The theoretical relation between the angle φ_s defined by tan φ_s=τ/σ and the angle φ_p defined by sin φ_p=(σ₁-σ₃)/(σ₁+σ₃) presents a useful information for engineering purpose. The theoretically derived relationship between the direction of major principal axis to the vertical ψ and tan φ_s made clear that the expression of tan φ_s=κ·tan ψ(κ is a constant) is an approximate relation. The direction angle of the slip plane to the horizontal was also theoretically obtained. This angle is related to the difference between φ_s and φ_p and the slip plane never coincides with the horizontal at any instance. The relationship between φ_p and φ_s based on the author's S model yields more realistic result than that based on the sliding block model. In this investigation, assumed is that the orientation of principal strain increment axis coincides with that of principal stress axis for the deformational regime after the most compactive point at which the positive dilatancy begins to take place.

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A method for simple shear simulation using a hollow cylindrical specimen is described. Drained tests at controlled axial stresses were performed automatically by means of a servosystem consisting of a micro-computer and a pneumatic-controlling system. For undrained tests on saturated specimens the simple shear simulation was achieved only by a mechanical means. The torsional simple shear behavior of Toyoura sand is described. This is well comparable with that from the Cambridge simple shear apparatus reported in the literature ; i.e., the major part of the rotation of principal stresses takes place only at the early stage of shearing keeping a stress ratio σ₁'/σ₃' close to the initial value 1/K₀. Strains associated with the principal stress rotation were found very small. It was found that the strength and deformation properties of Toyoura sand at relatively large strains in torsional simple shear are very similar to those by the plane strain compression test in which the directions of principal stresses with respect to the deposition direction and the value of σ₃' are similar to those at failure in the torsional simple shear test. It is likely that the effect of principal stress rotation on simple shear behavior during monotonic loading has often been considerably over-exaggerated.

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This paper is concerned with the yield condition of cohesionless granular materials with fabric anisotropy. The proposed yield condition is based on a physically motivated assumption that plastic slips will occur when the stress ratio on the contact plane, which has information about fabric anisotropy, with respect to a suitably specified slip plane becomes a critical value. The quantities involved in the proposed yield condition are given in terms of the contact and modified stress tensors. It is shown that two familiar yield conditions for an isotropic granular material are obtained as special cases of the present study and they can be naturally converted into the anisotropic yield condition by using the contact and modified stress tensors. The behavior of the proposed yield condition is determined by two fundamental factors : (1) the selection of referential slip plane ; (2) the degree of fabric anisotropy. These two factors are examined based on numerical calculation results. The shape change of the yield condition during triaxial loadings is also evaluated.

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A simplified procedure without using boring data is proposed for the seismic microzoning on soil liquefaction potential. The geomorphological land classification is adopted as the index for liquefaction susceptibility, because the classification data are easily available for an area of interest. For each geomorphological unit, the critical peak ground velocity which separates liquefiable from non-liquefiable conditions is investigated based on case histories at about 250 sites during 19 Japanese earthquakes. The critical peak ground velocities at the sites with the same geomorphological unit are almost the same. These critical velocities vary depending on the geomorphological unit. For reclaimed land, drained land, natural levee, river channel, sand dune and lowland between sand dunes, the velocity is 15 kines (cm/s). For back marsh, valley plain and delta, the velocity is 25 kines. And, for sand bar and alluvial fan, the velocity is 35 kines. Combining the land classification map and the isoseismal map of an earthquake which represents the distribution of peak ground velocity, the seismic microzoning on liquefaction potential during an earthquake can be readily made.

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The published analyses of axially loaded piles are based on the notion that the buckling load is P_cr ; the so-called critical load that is obtained from a linear eigenvalue problem. The purpose of this paper is to show that generally this assumption is not justified for slender piles. Since the main aim of the presentation is to clarify the basic features of the pile buckling phenomenon, and to show how they are related to the various buckling analyses, this study is conducted on a simple model that exhibits the essential buckling mechanism of the pile but is amenable to an exact non-linear analysis. One presented analysis is based on the common assumption that the lateral soil resistance increases linearly with the lateral displacement. It shows that P_cr may, or may not, be the true buckling load depending on the lateral stiffness of the soil and the bending stiffness of the pile. Thus, in some cases the buckling load has to be established from a non-linear analysis. Another analysis assumes that the lateral resistance stiffens non-linearly with increasing pile displacements. It shows that if the stiffening effect is strong enough, P_cr may be considered as the buckling load. Thus, for the stability analysis of slender piles, the actual soil response to lateral pile displacements is needed.

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