This article presents an experimental investigation on the erosion of soils using a continuous water jet. The experimental work shows the erosive behavior of the water jet and studies the different effects of its impact on the soil. The study presents empirical relations for the volume of soil cut, the jet diameter and its expansion with the distance, and also relations for the variation of the penetration rate and the eroded soil mass with varying water jet parameters. The results of the experiment show a critical velocity below which no penetration or erosion occurs. This critical velocity fundamentally depends on the soil properties and has been related to the resistance of the soils tested.

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A micromechanics model is used to analyse the stiffness anisotropy of soils at small strains. Five material constants for a cross-anisotropic elastic material are related to micromechanics variables such as fabric anisotropy, contact stiffness, particle radius, and the number of contacts in a given volume of particulate assembly. The analytical results from the model are compared with the published experimental data on small-strain stiffness anisotropy in order to estimate typical soil fabric conditions of sands and clays. The relationship between the small-strain shear modulus obtained from triaxial tests and shear tests is examined using the micromechanics model. The analysis shows that, when a soil is stiffer in the horizontal direction, the shear modulus evaluated from the conventional triaxial drained tests underestimates G_vh and G_vh. The opposite is true when a soil is stiffer in the vertical direction. When a soil is sheared in undrained condition, the measured shear modulus is closer to G_vh than G_vh, especially when the soil is stiffer in the horizontal direction. The effect of soil anisotropy on the stiffness measured from different stress paths in triaxial condition is investigated.

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This paper presents a Laser-Aided Tomography/plane strain compression (LAT/PSC) testing method, a new PSC test allowing for a discussion of granular micromechanics with visualized granular fabrics. LAT technique is utilized to visualize in real time any arbitrary cross-section of a granular specimen. An image processing algorithm, suited for LAT imageries, was successfully developed to extract irregular perimeters of 3D grains, their fabric, and their motions (displacements and rotations) caused by loading. This micromechanical information together with the overall behavior of the granular assemblage, such as stress-strain curves and dilatancy characteristics, are quite useful for validating various empirical rules and/or numerical simulations, and also for providing new physical insights in this field.

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The description of the deformation behavior of Shirasu (volcanic sandy soil) by the elastoplastic constitutive equation is studied adopting a subloading surface model with rotational hardening. Also, test results for isotropic consolidation and triaxial compression with several lateral stresses under the drained and the undrained conditions for various initial void ratios are reported. Further, simulation by the constitutive equation is compared with the test results. High ability of the constitutive equation for the prediction of mechanical behavior of Shirasu is verified by the comparison.

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In critical state soil mechanics, the volume change behavior of soils has typically been analyzed based upon conventional "e-logp' relationships". However, compaction/densification of loose sand, for example, can sometimes occur even without any significant increase of mean effective stresses. This study presents a model which considers the fact that volume change can occur due to decay/collapse of the structure of soils. Taking into consideration the differences between clay and sand, this study models super-subloading surfaces together with rotational hardening using the modified Cam-clay model. The effects of decay of the soil structure, loss of overconsolidation and evolution of anisotropy are mutually discussed concerning their relationship with ongoing plastic deformation. Fundamental constitutive model responses are illustrated in the present study particularly for "compaction" of sand. Repeated application of low-level shear stress upon loose sand yields a huge amount of volume compression, which is due to the rapid collapse of the initial soil structure. Repetition of the loading also results in a rapid increase of the overconsolidation ratio. Drained and undrained shear behavior of the sand naturally changes remarkably along this densification/compaction procedure, which is also consistently predicted using a single set of soil parameters. Elasto-plastic behavior of the same sand at various densities is thus totally described in the present study in a single the-oretical framework based on soil parameters independent of density.

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In order to investigate the anisotropic behavior of soft sedimentary rock, a series of triaxial compression tests are performed on Tomuro stone, sampled in different directions. From the test results, it is confirmed that the deformation characteristics and strength are strongly dependent on the direction; in other words, Tomuro stone is a transversely isotropic body. The authors have developed an anisotropic elasto-plastic constitutive model which can describe anisotropic behavior through triaxial tests. The model is based on the elasto-plastic constitutive model with strain softening proposed by Adachi and Oka (1995). In the formulation of the model, a generalized Hooke's law is adopted for the elastic strain increment, and the transformation stress concept proposed by Boehler and Sawczuk (1977) is used for the plastic strain. Five independent elastic moduli are used for the transversely isotropic body, and three independent parameters are introduced for the plastic anisotropy. These parameters can be determined from the triaxial compression tests performed with specimens sampled in different directions. Comparisons between the experimental data from triaxial tests and simulated results from tests using the model indicate that the proposed constitutive model can well reproduce the direction dependent behavior of soft sedimentary rock.

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Offshore skirted foundations can be simulated as pre-embedded foundations, since disturbance during installation is limited to a small region around the skirts themselves. The bearing capacity of this type of foundation may be assessed using limit analysis, based on a rigid-plastic idealisation of the soil. However, recent results have shown a significant gap between lower and upper bound estimates of capacity as the skirt depth increases. It is therefore necessary to use techniques such as the finite element method to assess appropriate bearing capacity factors more precisely, and also to identify the transition from shallow to deep failure mechanisms. The soil is considered as normally consolidated clay with undrained shear strength increasing linearly with depth. Soil flow mechanisms have been studied for embedment ratios of up to 5 and the flow mechanisms in normally consolidated soil have been compared with those in homogeneous soil. It has been found that, with increasing embedment ratio, the soil flow mechanism will change from surface failure to a deep, cavity expansion mode and that this transition occurs at a higher embedment ratio in a normally consolidated soil (with significant strength gradient) than in homogeneous soil. Limit analysis can give a reasonable prediction at shallow embedments before this transition. However, at deeper embedments it is necessary to employ a large penetration analysis in order to arrive at a true limiting capacity. In this paper, the limit bearing capacity and transition depths are evaluated and compared with corresponding results for homogeneous soil.

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In order to study stress-strain-strength and yielding characteristics of lime treated clay, an extensive testing program was conducted on lime treated clay. It was found that the main effect of lime treatment was to change the soft clay from normally consolidated to overconsolidated behavior. Heavily overconsolidated characteristics were observed for stress states inside the volumetric yield locus obtained from anisotropic consolidation tests. The volumetric yield loci of lime treated clays were found to be more pronounced than distortional or strain path yield locus. Outside the volumetric yield locus, the behavior was found to consist of an initial pseudo-elastic phase followed by a stage where the behavior appears to be similar to that of a work-hardening plastic material as the stress path proceeds towards the curved failure envelopes. The treated clays strain-softened after failure with the residual stress states lying close to the critical state line of the untreated clay. A conceptual model to describe the behavior of lime treated clay is introduced, in which the presence of distortional yield locus shifts with lime content and curing time.

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The aim of this study is to establish a procedure to rationally determine the partial factors for a vertically loaded pile in the limit state design format based on a sound reliability theory. The frequency of the usage of pile types and dimensions are investigated first. Several design examples are selected, and load ranges and combinations on typical piles are studied. Based on these results, typical load intensities, load combinations and soil profiles are set for the code calibration. Also, uncertainties involved in seismic loading are investigated based on the historical seismic data using an extreme statistical analysis, so called POT (peaks over threshold) analysis. Uncertainties concerning resistances of piles are taken from two well known studies: Okahara et al. (1991) and AIJ (2000). FORM (first order reliability method) analysis is carried out to find out the current level of reliability index. Finally, the design value method is employed to determine the partial factors.

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In this paper, sample recovery ratios, fluid pressure and sampler penetration resistance in tube sampling are discussed. The samplers were taken by two types of hydraulic piston samplers, one a two-chambered sampler with inner diameters of 45 mm and 50 mm, and the second a one-chambered sampler having a 70 mm diameter. The second type is the one commonly used in Japan and which was also used at the Meike Elementary School, the JGS-1989 investigation site. These samplers are here after referred to as the 45D, 50D and 70S samplers. The mean value of the sample recovery ratios from the 45D and 50D samplers was 93% greater than that of the 70S sampler. This value remained independent of the sands having N= 3∼54 from the standard penetration test. Guidelines for estimating the pump fluid pressure for tube sampling of sand, sampler and drilling equipment penetration resistance forces and the relationship between the sample recovery ratios and the drilling mud densities, etc., were established for Niigata sand. The end results contribute to a safer and more reliable sampling method.

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