Various elastoplastic constitutive equation providing the fundamental base of elastoplasticity have been proposed up to present. Among them only the subloading surface model has the pertinent structure fulfilling the mechanical requirements for constitutive equations. In this article the basic structure and the main features of the subloading surface model are shown and the present advancement of the model is described. Further, the wide applicability and the high ability of the future development for the synthetic description of mechanical behavior of solids from the elastoplastic deformation of solids to the friction phenomena between solids are described.

View full abstract

Recently developed lightweight dynamic cone penetrometer was successfully applied to investigate spatial variability of in-situ strength of Masado profiles in Hiroshima prefecture, Japan. Six patterns were identified based on the penetration resistance varying with the depth. Fairly good correlations were developed between penetration resistances obtained by lightweight dynamic cone penetrometer and portable dynamic cone penetrometer. Spatial variability analyses conducted on different grid spaces showed that the coefficient of variance of cone resistance varies from 0% to 40%. Semi-variogram analyses showed that the Spherical Models could be used for representation of spatial autocorrelation of Masado profiles.

View full abstract

Aseismic design method of earth structure concerns only the safety factor and the permanent displacement; however, the estimation of the range of slope failures is necessary to make a safety regulations for construction of buildings on a slope. Based on slope stability analysis for a case history in the 2001 Geiyo earthquake, and a parametric study in consideration of the heterogeneity of the ground strength, the range of slope failures due to earthquakes were investigated. The results was summarized as a rational criteria for the range of slope failures considering slope angles, slope height and input motion level. Thus, the proposed criteria enables a rational safety assessement of buildings close to a slope.

View full abstract

The objective of this paper is to make a clear the influences of the analytical dimension for modeling the spatial distribution due to the inhomogenity of soil properties on the strong nonlinear seismic response. 2D and 1D FE models are used to consider either the vertical and horizontal distribution of the soil property or the vertical distribution of the soil property. The hyperbolic model is used as a nonlinear model of the soil property. The shear wave velocity and the internal friction angle in the model are taken into account of the variables with the spatial distribution. The spatial distribution is generated by using a sample function of a discretized Gausian stochastic field and is considered the characteristics values to be realistic. It is found that the earthquake responses of the two dimensional model behavior like one dimension. The issue is obtained that the information with the spatial distribution is not sufficient.

View full abstract

In geological disposal of high-level radioactive wastes, bentonite based buffer fills up the space between waste-container and bedrock, because it has a swelling property and low permeability. High-level radioactive wastes generate decay-heat, and it is apprehended that the swelling characteristics of bentonite declines by the decay-heat of wastes. To contribute to this problem, this study investigated swelling-pressure and swelling-deformation of bentonites experienced some thermal histories in the laboratory. Moreover, this study discusses mechanism of thermal influences to bentonite-swelling by considering the above experimental results with chemical analyses about heated bentonites.

View full abstract

Compression curve after inundation represents one of foundamental characteristics for unsaturated soils. Many constitutive models for unsaturated soils contain it as an important parameter. In this paper, we studied the compression curve for compacted silty clay specimen in soaking test with oedmeter test apparatus. From the test results, we found that the compression curve obtained was different from the compression curve for slurry specimen, and that in some case, compaction effort affect on the compression indexes for compacted specimen. These results mean that the compression curve after inundation is essentially different from that for slurry specimen of the same sample.

View full abstract

The earthquake resistant reinforcement method for pile foundations is limited by various unfavorable construction conditions. The authors proposed a new method for earthquake resistant reinforcement applicable to either new or existing pile foundations, which was confirmed model shaking table test under 1g gravitational field and the numerical simulation analysis. A full-scale model test of the proposed method was conducted to examine the construction performance and the quality of reinforcement body in the pile foundation. The full-scale test includes lateral loading tests, vibration tests and excavation of the reinforcement body for observation. Based on the test results, applicability of the proposed reinforcement method for a real pile foundation was confirmed.

View full abstract

To study the micro-mechanics of granular flows, disc flow are generated by using two-dimensional rapid flow apparatus and shear stress and particle movement are measured. To decrease the friction between disc and floor, which disturbs particle moving, polyethylene disc instead of steel sphere are selected. By using disc particles and the rapid shear apparatus, (a) effect of solid fraction on shear stress generation, (b) effect of shear strain rate on the stress generation and (c) distribution of particle velocity are studied. It can be said that the relationship between shear strain rate and shear stress measured in disc flow is qualitatively similar to the relationship measured by using steel sphere and same apparatus. In comparison between disc and sphere, it can be said that disc has an advantage in tracking particle movement by PTV software.

View full abstract

Authors proposed the sheet-pile foundation that combined sheet piles with footing. Sheet-pile foundation can expect the reinforcement effect of constraint of the ground. Because sheet piles reinforce the inside ground of sheet piles, the sheet-pile foundation has higher bearing capacity than footing foundation.
In this research, the series of vertical loading tests of sheet-pile foundation and footing foundation were conducted. The pressures of the bottom of the footing were measured, and the ground displacement was calculated by image processing system. It was found from these results that sheet-pile foundation had the improved effect of bearing capacity of bottom ground and friction of sheet piles.

View full abstract

In developing countries, lack of trafficability of the rural roads has been identified as one of the main causes of the poverty of the rural people. To keep the accessibility of all-weather roads in the rural area, in this study a new method to maintain the unpaved rural access road with “do-nou (soil bag)” is being developed. This method is labor based technology and requires the bags and material put inside the bag, which are readily available to the people in developing countries. Through the tensile strength tests and full size model driving tests, their applicabilities to the road structure were ascertained and the appropriate road structure maintained by the do-nou was proposed.

View full abstract

In order to grasp mechanical behavior of anisotropic ground beneath a structure subjected to cyclic loading, a series of model tests was performed under several depositional conditions. In particular, applicability of countermeasures constructed by either side wall or sheet pile was examined detailedly. The result showed that the installation of side wall or of sheet pile had advantageous as countermeasures against such a ground failure, however the installation effect was different depending on the changes in depositional condition of the ground.

View full abstract

The paper proposes a precise technique to compute the limit state exceedance probability of earth slopes using a low-discrepancy sequence Monte Carlo (LDSMC) method and an importance sampling with a low discrepancy sequence Monte Carlo (ISLDSMC) method under uncertainties of backfill and clay properties having normal distributions. To increase the computational efficiency, the low-discrepancy sequence (LDS) is adopted in this study, which is one of the quasi-random numbers having a uniform distribution. Estimation of the design points near the failure region is essential to apply the importance sampling algorithm. We found that the recently developed subset Markov chain Monte Carlo (MCMC) method is useful to find multiple design points although a first-order reliability method (FORM) is applicable for simple cases. The numerical simulation in this study revealed that the LDSMC and ISLDSMC method can effectively compute the accurate limit state exceedance probability of earth slopes with a small number of simulations by comparing with the conventionally used crude Monte Carlo simulation.

View full abstract

A lot of undersea tunnels have been constructed in Japan, after first construction of the Kannmon Tunnel, as conventional railway in 1944. If a situation such as flooding occurs in the undersea tunnel in the operating line, the probability of human casualty is very high, and it results in the great threat to the safety of the social infrastructure. However, there are so many uncertain things in the operating tunnel that the maintenance of existing tunnels relies on the experiences of past deformed tunnels. Accordingly the same idea is employed to the undersea tunnels.
In this paper, the long-term measurement records since 1988 in the Seikan Tunnel are interpreted, the long-term behavior of this tunnel is examined. Consequently a proposal is made of a new idea on maintenance of the undersea tunnel.

View full abstract

The ground deformation analysis that takes account of frost heave ratios based on the experimental formula, is proposed to seek for a countermeasure against the expansive displacement caused by the freezing method. The frost heave ratios of each area divided according to the heat flow direction, are calculated by two models considering the cooling surface shape, and this method is incorporated with the three-dimensional elastic FEM.
The validity of this method is confirmed by the measurements in two sites, of which installation direction of the freezing pipes are different. Moreover, the effectiveness of this analysis is verified by comparison with the cases assuming the one-dimensional and the isotropic frost expansions.

View full abstract

The design method of bearing capacity of rubble foundations for breakwaters were constructed assuming of the linear distributed load support system by rubble foundations. Recent experimental study, however, revealed that load support system by rubble foundations were inhomogeneous and discrete. The fact suggests the necessity for the construction of more rational design method of bearing capacity for breakwaters. In this study, we conducted series of loading tests in order to evaluate the load distribution characteristic inside rubble foundations and deformation characteristic of rubble in accordance with the increase of the load. We furthermore conducted two-dimensional distinct element analyses to simulate the result of experiments.

View full abstract

This study is about the recycling technology of soft clay and scrape tire as geomaterial. And, the purpose of this paper is describing the advantageous mechanical properties of cement treated clay mixed with tire chips.
Generally, cement treated clay shows the brittle deformation property, but it is found that it is able to improve its toughness by adding tire chips at 10 to 20% volume. In this paper, it is shown the results of some laboratory tests, unconfined compression test and triaxial compression tests about this composite material, in order to explain the effect of improvement in its deformation property by mixing tire chips, quantitively. And it is tried to show the consideration of its mechanism.

View full abstract

Hazard maps support effective disaster management of rock mass failure. In this study we compiled reliability prediction charts of hazard areas caused by rock mass failure debris, which are the basis of hazard maps. In addition to the predicted debris hazard areas, we took into account other factors such as rock slope stability and the effects of countermeasures obtained from published data to prepare hazard maps for risk assessment. Applying map-based risk assessment to rock mass failure allowed us to visually identify risks by size, location, and section, consequently enabling reasonable logical judgment from a broad perspective in setting priorities for countermeasures and inspections against rock mass failure.

View full abstract

This paper developed a rock fall simulation by using discontinuous deformation analysis (DDA). In the simulation, the energy loss of rock fall was expressed respectively in response to every movement feature of rock fall by using absolute parameter. The energy losses of the rock fall were categorized to three forms of the energy loss in friction, the energy loss considering collision and the energy loss by vegetation. The energy loss model by using absolute parameter have been built in the DDA method. Additionally, using the improved DDA, the simulation of field rock fall experiments was performed. The results of the movement feature, velocity and the jump height of the rock fall were in good agreement with the field experiment. Herewith, the new technique considering the slope absorbability, vegetation condition and shapes of the falling rock block has been established a new methodology for design of road disaster prevention of rock falls.

View full abstract

An impermeable vertical seawall of steel sheet piles or steel pipe piles is considered one of the most useful methods for the hydraulic barrier work of confined disposal facitilies, because the steel seawall can be embedded deeply into the impermeable seabed. The present paper describes field performance tests about seven types of steel seawalls newly developed. Test facilities were designed and constructed, then the performance was evaluated by leakage tests by filling water. In addition, the applicability of the steel seawalls is discussed and tabulated in the paper in consideration of the fail-safe design concept including backup functions, inspections, monitoring, and repairing.

View full abstract

In order to investigate the influence of the water on compression characteristic for decomposed granite soils, a single particle crushing and one-dimensional compression tests were carried out on three decomposed granite soils and Silica sand. The initial fracture strength for single particle reduced and variability of the strength increases due to weakening by existing of water. Moreover it was recognized that the one-dimensional compression characteristic was related to the initial fracture strength characteristic. And the initial fracture strength also has the effect of weathering.

View full abstract

The minimum effective stress is a lower limit of the effective stress and it is required in some effective stress analyses for the numerical stability. This study applies the minimum effective stress concept proposed by Sento et al. (2004) to an existing effective stress analysis in the framework of elasto-plastic theory. Liquefaction occurrence during shaking and settlement due to dissipation of excess pore water pressure were quantitatively predicted. Performance of this method was verified through the numerical simulations of laboratory tests as well as dynamic centrifuge tests.

View full abstract