Yasuhiro Mitani

Spatial probabilistic modeling of slope failure using an integrated GIS Monte Carlo simulation approach

Spatial probabilistic modeling of slope failure using a combined Geographic Information System (GIS), infinite-slope stability model and Monte Carlo simulation approach is proposed and applied in the landslide-prone area of Sasebo city, southern Japan. A digital elevation model (DEM) for the study area has been created at a scale of 1/2500. Calculated results of slope angle and slope aspect derived from the DEM are discussed. Through the spatial interpolation of the identified stream network, the thickness distribution of the colluvium above Tertiary strata is determined with precision. Finally, by integrating an infinite-slope stability model and Monte Carlo simulation with GIS, and applying spatial processing, a slope failure probability distribution map is obtained for the case of both low and high water levels.

Development of a shear-flow test apparatus and determination of coupled properties for a single rock joint

Abstract A new laboratory technique for coupled shear-flow tests of rock joints was developed and used to investigate the coupled effect of joint shear deformation and dilatancy on hydraulic conductivity of rock joints. This technique was used to carry out coupled shear-flow tests with an artificial created granite joint sample under constant normal loads and up to residual shear deformations of 20 mm. The hydraulic conductivity was estimated by using a finite difference method and an approximate equation assuming the cubic law. The shear-flow testing results revealed that the change of hydraulic conductivity is approximately similar to that of the dilatancy of a joint. The hydraulic conductivity increases rapidly, by about 1.2–1.6 orders of magnitude for the first 5 mm of shear displacement. After passing the residual shear stress, the hydraulic conductivity becomes gradually a constant value with increasing shear displacement. On the other hand, the hydraulic conductivity after shearing is about one order of magnitude larger than that prior to shearing. Shear-flow coupling characteristics obtained from these tests have a consistent trend with Bartons model prediction during the initial shear process. However, increasing deviation between measured and predicted hydraulic conductivity of rock joint samples has been observed with increasing shear displacement.

Critical Reynolds number for nonlinear flow through rough‐walled fractures: The role of shear processes

This paper experimentally investigates the role of shear processes on the variation of critical Reynolds number and nonlinear flow through rough-walled rock fractures. A quantitative criterion was developed to quantify the onset of nonlinear flow by comprehensive combination of Forchheimers law and Reynolds number. At each shear displacement, several high-precision water flow tests were carried out with different hydraulic gradients then the critical Reynolds number was determined based on the developed criterion. The results show that (i) the Forchheimers law was fitted very well to experimental results of nonlinear fluid flow through rough-walled fractures, (ii) the coefficients of viscous and inertial pressure drops experience 4 and 7 orders of magnitude reduction during shear displacement, respectively, and (iii) the critical Reynolds number varies from 0.001 to 25 and experiences 4 orders of magnitude enlargement by increasing shear displacement from 0 to 20 mm. These findings may prove useful in proper understanding of fluid flow through rock fractures, or inclusions in computational studies of large-scale nonlinear flow in fractured rocks.

Rigorous theoretical analysis of a flow pump permeability test

With the growing importance of environmental issues in our society, extremely low-permeability geotechnical materials are being studied increasingly for their long-term stability and effectiveness in retarding the transport of hazardous wastes. Relatively rapid measurements of the permeability and specific storage of the materials, using relatively low hydraulic gradients, can be obtained with a constant flow pump and the corresponding theoretical analysis proposed by Morin and Olsen (1987). However, the accuracy of this method is limited because their theoretical analysis does not take into account the storage capacity of the experimental system. This paper presents a more general theoretical analysis and shows how it can be used to determine not only the permeability and specific storage of a test specimen, but also the storage capacity of the experimental system. Experimental data are presented that illustrate the accuracy and efficiency of the general theoretical analysis.

Residential proximity to main roads during pregnancy and the risk of allergic disorders in Japanese infants: The Osaka Maternal and Child Health Study

Miyake Y, Tanaka K, Fujiwara H, Mitani Y, Ikemi H, Sasaki S, Ohya Y, Hirota Y. Residential proximity to main roads during pregnancy and the risk of allergic disorders in Japanese infants: The Osaka Maternal and Child Health Study.
Pediatr Allergy Immunol 2010: 21: 22–28.
© 2009 John Wiley & Sons A/S

A GIS-based prediction method to evaluate subsidence-induced damage from coal mining beneath a reservoir, Kyushu, Japan

The occurrence of subsidence caused by mining may be a complex process that causes damage to the environment. In the last century there was significant development in prediction methods for calculating surface subsidence. However, because mining may take place by multi-seam extraction, the use of current prediction methods to obtain the distribution of subsidence is a difficult and time-consuming task. Furthermore, it is impracticable to evaluate damage accurately by this method. In this paper, a new prediction method has been developed to calculate 3D subsidence by combining a stochastic model of ground movements and a geographical information system (GIS). All the subsidence calculations are implemented by a computational program, where the components of the GIS are used to fulfil the spatial–temporal analysis function. This subsidence prediction technique has been applied to calculate ground movements resulting from 21 years of coal mining under a reservoir in Japan. Details of movement were sequentially predicted and simulated in terms of years. Furthermore, subsidence-induced damage owing to progressive horizontal strain was assessed. These values conformed to the acceptable strains in reservoir dams, thus ensuring safety against tensile failure of the concrete and consequent flooding.

GIS-Based Computational Method for Simulating the Components of 3D Dynamic Ground Subsidence during the Process of Undermining

Most research has focused on using the subsidence prediction method to calculate final movement at the center line above mining operations and assess the surface structural damage without taking into account the dynamic extraction process. Nevertheless, the occurrence of subsidence caused by underground mining has three-dimensional (3D) time-dependent components of movement in which each of these components has a different effect on the types of structures subject to subsidence. In this paper, a new computational method is proposed to calculate 3D dynamic subsidence during the process of undermining by combining the stochastic theory, the Knothe model, and the Geographic Information System (GIS). A case of 3D dynamic modeling was simulated for a rapid undermining scenario to demonstrate the effect of different advancing mining faces on the development of traveling strain. In addition, an application of the GIS-based method to actual field conditions in coal-mining subsidence in China is presented in this ...

Effect of Precipitation Timescale Selection on Tempo-spatial Assessment of Paddy Water Demand in Chikugo-Saga Plain, Japan

For the purpose of fully understanding tempo-spatial water circulation in the rice growing region of Chikugo-Saga, Japan, an assessment model of paddy water demand at daily/monthly time and one-kilometer space scales was established by using agro-statistic data, land use and meteorological data under GIS environment. Then, the daily and monthly precipitation data were, respectively, imported into the model to assess the tempo-spatial distribution of paddy water demand. Through the comparison between the two estimated results, it is shown that the selection of precipitation timescale has significant influence on the assessment of paddy water requirements during non-drought seasons while hardly effects the paddy water demand estimated for drought seasons. Furthermore, the daily-time-series analysis of the paddy water demand assessment was performed. It is found that the timescale-induced difference in the paddy water demand has a direct relation to the frequency and the amount of the concentrated heavy rainfall. From the investigation, it can be concluded that the proposed GIS-based model is suitable to be used to quantitatively carry out the tempo-spatial assessment of paddy water demand, and the daily precipitation data are more reasonably adopted to estimate paddy water requirements in non-drought seasons than the monthly precipitation data are done.

Integrated Shear and Flow Parameter Measurement

Studies on the variation of permeability and the specific storage of bentonite-sand mixtures with shear deformations that may be caused by earthquakes and/or other geological events are of fundamental importance for long-term safety assessments of radioactive nuclear waste disposal facilities. This paper presents a recently developed and improved method for integrated shear and flow parameter measurements on a mixture of Kunigeru V1 Bentonite and D-Sand. This material will be used in low-level radioactive nuclear waste disposal facilities in Japan. The results of this study show that: (1) temperature control is important for measuring hydraulic parameters of low-permeability materials with the flow pump method; (2) shear strains up to about 3% did not significantly influence either the permeability or the specific storage of the bentonite-sand mixture; and (3) permeability and specific storage values interpreted from different time intervals during the transient rise and transient decay phases of the flow pump permeability tests were almost the same, which suggests that the reliability of both the experimental results and the newly derived theoretical analysis used to interpret the hydraulic parameters.

Estimation of RUSLE EI 30 based on 10 min interval rainfall data and GIS-based development of rainfall erosivity maps for Hitotsuse basin in Kyushu Japan

Land erosion is regarded as one of the most important phenomenon causes land degradation. In revised universal soil loss equation (RUSLE) erosion model, rainfall erosivity factor (R) is one of the important parameters. Ideally, the calculation of EI30 (R factor) uses breakpoint rainfall intensity data which is calculated manually from graphical charts that are generated by continuously recording rain gauges. However, due to limited availability of breakpoint rainfall data, many simple methods for estimating EI30 have been developed by using yearly, monthly and daily rainfall data. In this research, due to limited data availability, pluviograph data at 10 minute interval from eight stations in Hitotsuse basin were used to compute EI30 (R factor) for RUSLE. The approach used in this research is based on storm rainfall and duration data from 1990 to 2009. This method is based on the calculation of rainfall energy per unit depth of rainfall, total storm kinetic energy (E), rainfall intensity for a particular increment of a rainfall, and maximum 30 minute rainfall intensity. Furthermore, EI30 were computed, and then GIS method was used to create rainfall erosivity maps. The annual rainfall erosivity values prediction model was developed based on MFI values.