Pile foundations in a soft ground will usually be subjected to lateral cyclic loading during earthquakes. In a major earthquake, it is reasonable to think that the mechanical behavior of the pile foundation and the surrounding ground is nonlinear. In recent years, the limit state design method has become predominant in the design of foundations for railway bridges and other structures. Investigations of the mechanical behavior of pile foundations subjected to lateral cyclic loading up to the ultimate state, therefore, are very important in providing evidence for the design method. In this paper, field tests on a pile foundation, composed of cast-in-place reinforced concrete piles and subjected to oneside cyclic lateral loading up to the ultimate state, are simulated with the three-dimensional elasto-plastic finite element analysis (DGPILE-3D). In the numerical analysis, particular attention is paid to the stress-strain relation of the soil which, to the author's point of view, plays a dominant role in the mechanical behavior of the pile foundation. Such constitutive models as the Drucker-Prager model, Cam-clay model, and t_ij model are adopted for the analysis in order to find the differences in the results due to the application of different constitutive models. Based on the analysis, the authors try to provide an applicable numerical way of evaluating the mechanical behavior of a pile foundation subjected to cyclic lateral loading at the ultimate state.

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In designing structures, especially harbor structures on soft clayey ground, deformation of the foundation ground may sometimes appear as a vital factor for rational design. Both the short and long term behavior of soft clay improved by sand compaction piles with low replacement ratios, which is subjected to backfilled caisson loading, were investigated through a series of centrifuge model tests. In model tests, the construction sequence from the installation of the caisson to backfilling was simulated in-flight. Effects of replacement ratio, improvement width, SCP location and loading rate on the behavior of the caisson were studied. It was found that settlement of the model ground can be effectively reduced by a higher replacement ratio, and long term settlement of caisson after backfilling is highly influenced by the settlement of the ground behind the SCP portion. A wider improvement area towards the fill is more effective in reducing the lateral displacement of the caisson both during and after backfilling, and the degree of consolidation of the clay part in SCP ground has a significant effect on short term lateral deformation.

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In order to evaluate the effects of increasing cementation on the mechanical properties of lightly cemented soils, artificially cemented clay was prepared and a series of standard consolidation tests, undrained triaxial compression tests and constant mean effective stress tests was performed. Based on the experimental considerations, the effects of light cementation on the stress-strain behaviour and strength property are discussed. In addition, based on the theoretical considerations within the framework of the critical state concept, several basic concepts for the development of a constitutive model for lightly cemented clays are presented. The special characteristic of the presented model is the introduction of an internal variable which controls the effects of cementation. The following conclusions are obtained : 1) The failure state of lightly cemented clay may be determined in the balance of cementation, void ratio and stress condition. 2) The failure state line in the p-q space is parallel to that of an uncemented clay and has a certain intercept p_r, which characterizes the cementation effect. The slope of the failure state line in the e-ln (p+p_r) space becomes steeper with any increase in cementation effect. 3) A constitutive model incorporating cementation is proposed. Introduction of a soil constant p_r is effective in estimating the mechanical properties of lightly cemented clay.

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The effects of tube sampling disturbances on undrained shear properties of reconstituted samples of coastal soils were investigated. The values of undrained shear strength (s_u), initial tangent modulus (E_i) and secant modulus (E₅₀) were reduced while axial strain at peak deviator stress (ε_p) increased because of disturbance caused by the penetration of samplers. Disturbances also considerably reduced initial effective stress (δ'_i) and pore pressure changes. The changes in soil parameters between the "in-situ" and "tube" samples depended markedly on the characteristics of the tube samplers. Values of s_u, E_i, E₅₀ and δ'_i decreased while the values of ε_p increased with increasing area ratio (or decreasing external diameter to thickness ratio) of the samplers. It was also found that the reductions in the values of s_u, ε_p, E_i, E₅₀ and δ'_i increased with decreasing plasticity of the soils. A number of reconsolidation procedures, both isotropic and anisotropic including SHANSEP methods, were adopted in order to assess the suitability of reconsolidation of "tube" samples to recover the "in-situ" properties of the soils. It appeared that reconsolidation using SHANSEP procedures may not be applicable to these coastal soils. However, K₀-reconsolidation to "in-situ" stresses provided a better estimate of "in-situ" properties than other reconsolidation techniques.

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The applicability of a method for predicting 'bearing capacity increase'in reinforced sandy ground was examined using tests performed under various test conditions. It was found that the present method predicted, with reasonable accuracy, the bearing capacity increase in sandy ground, reinforced with stiff reinforcement. This method may not be applicable for sandy ground reinforced with extensible reinforcement due to the unsuccessful formation of a semirigid zone under the footing. An investigation into the settlement of a footing on reinforced sandy ground, at ultimate footing load condition, suggested that the settlement of footing for reaching peak footing load may be correlated to the 'deep-footing'and the 'wide-slab'mechanisms. That is, the ultimate settlement ratio between reinforced and unreinforced model sandy ground, SR_f, may be linearly correlated to 'BCR_D'and 'BCR_s', which represent 'deep-footing' and 'wide-slab'effects, respectively, on the ultimate bearing capacity increase in reinforced sandy ground.

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Deformation behavior of an unsaturated soil in collapse was studied using a modified triaxial test apparatus. Three kinds of wetting test were conducted on compacted clay specimens. (i) wetting tests under isotropic stress state, (ii) wetting tests under constant shear stress, and (iii) repeated wetting during shear test under a constant mean net stress. Collapse occurred later in comparison to isotropic stress state conditions under triaxial stress state when shear stress was kept constant. This phenomenon is due to the decrease of the coefficient of permeability, which relates to the changes associated with bulk water to meniscus water. The relationship between void ratio change and increase in water content observed under the different stress states tested showed similar behavior. In the repeated wetting during shear test, a continuous decrease in void ratio was observed with water absorption and drainage. This phenomenon is also related to the change of the bulk water to meniscus water. The secondary wetting process is observed in the experimental testing program discussed in this paper. The presently available constitutive models do not take into account the secondary wetting process. The research studies presented in this paper provide more insight into the collapse behavior.

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A semi-empirical computational technique is presented for predicting the depth of craters formed by dynamic compaction (DC) pounders after the first impact. This technique utilizes a correlation developed between the initial shear strength of the soil beneath the pounder, determined by a CPT profile, and the impact energy per unit area (specific impact energy). First, the correlation is established by a series of model impact tests involving different drop heights, drop weights and impact areas. Then, the correlation is verified by the results from a full-scale field test performed by the authors. Further, data from a DC project performed elsewhere is also shown to support the predictive technique. An illustrative example is provided to demonstrate how typical CPT data can be adapted to predict the crater depths during DC projects for a given level of applied impact energy. On the other hand, this method can be used to determine the maximum impact energy that can be applied without causing excessive initial penetration of pounders and thus preclude the need for trial impacts. Hence well in advance of heavy equipment mobilization, this technique can certainly aid in effective planning of DC projects on particularly weak ground where penetration predominates heave.

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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.

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In this paper, three methods for seismic evaluation, namely, a separated method using a dynamic analysis on a simplified sway-rocking model (S-R model), a responding displacement method, and a dynamic analysis on a full system, are invstigated by conducting a series of static and dynamic three-dimensional elasto-plastic finite element analyses. At first, the validity of a newly developed finite element analytical code DGPILE-3D, which is used throughout this paper, is checked through a dynamic model test on a pile foundation. Then, an elevated railway bridge with a pile foundation is investigated with the separated method and the responding displacement analysis, which are often used in seismic design, and a three-dimensional elasto-plastic dynamic analysis on a full system. Two types of ground are considered in order to understand the influence of the soil on the mechanical behaviors of upper structures and pile foundations. From these analyses, it is possible to understand the difference of the mechanical behaviors of pile foundation predicted by different methods. Based on the results obtained in this paper, fundamental knowledge needed for developing an applicable and easily conducted seismic design method with three-dimensional finite element analysis, is achieved.

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This paper presents an analysis of Weibull statistics applied to tensile failure of soil grains compressed between flat platens. The aim is to validate the use of Weibull applied to single soil grains, since such a statistical approach can then be used to analyse particle survival in aggregates comprising many soil particles. Particles of Quiou sand have been compressed diametrically between flat platens. A characteristic stress at failure can be defined as the diametral force divided by the square of the particle diameter at failure. Approximately 30 grains were tested for each of the following nominal particle sizes : 1 mm, 2 mm, 4 mm, 8 mm and 16 mm diameter. It was found that the data could be well described by the Weibull statistics of brittle ceramics, which requires an assumption of geometric similarity to be made, and the Weibull modulus could be taken to be about 1.5. This is shown to be in agreement with the observation that the average crushing force is not a strong function of particle size. The force required to break a small particle asperity is also shown not to be a strong function of the asperity size, consistent with the observed Weibull modulus. The paper provides evidence that Weibull can reasonably be applied to the tensile failure of soil grains, thus validating the use of Weibull as a tool in the analysis of particle crushing.

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Rapid and accurate measurement methods for pesticide sorption onto different soil types are needed to evaluate pesticide transport and fate in soil and for risk assessment of new pesticides. Sorption of two commonly used pesticides (asulam [N-acetyl-P-amino-sulphone amide] and simazine [2-chloro-4, 6 bis (ethylamino)-1, 3, 5 triazine]) in two different Japanese soils (sand and sandy loam) was measured using (i) a traditional batch experiment method and (ii) a high performance liquid chromatography (HPLC) micro-column method that measures the retardation of an adsorbing solute (e.g. pesticide) relative to a non-adsorbing solute (e.g. deuterium labeled water, D₂O) during different water transport conditions. The HPLC micro-column system requires only small amounts of soil and chemicals, and experiments are rapid and easy to perform compared to traditional batch or larger-scale column experiments. Retardation factors (R) for the two pesticides were estimated from both (i) batch experiments (adsorption isotherms) and (ii) microcolumn pesticide breakthrough curves using the public domain CXTFIT [U.S. Salinity Laboratory, USDA, USA] solute transport model for curve-fitting. Batch and micro-column experiments yielded similar R values ranging from 1.1 for asulam sorption onto Hiroshima sand to about 30 for simazine sorption onto Hiroshima loam. Similar values of R were obtained at two different water flow rates in the HPLC micro-column, confirming the reproducibility of the HPLC micro-column method.

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