Pore air has a significant influence on the seepage and stress in an unsaturated ground. The aim of this study was to obtain the local collapse of the ground due to the increase in pore air pressure when pore air was entrapped in the ground following a rapid increase in the water level and the saturation of the surface ground. One-dimensional seepage tests were carried out, measuring the pore air pressure, the amount of charged water, and the displacement at the surface of the specimen. The experiments proved that the soil specimen had collapsed over the critical pore air pressure, which rose in proportion to the amount of infiltrated water. In addition, the rate of the collapse development was found to correlate linearly to that of the inflow water. The ground was threatened by collapse due to the ascent of air pressure when the surface ground was saturated or there was low permeability of the air. Rapid infiltration to the zones of accumulated air, such as subsurface cavities or pipes, induced the increase in air pressure.
The classification maps are required for management and for the estimation of agricultural disaster compensation; however, those techniques have yet to be established. Some supervised learning models may allow accurate classification. In this study, the Random Forest (RF) classifier and the classification and regression tree (CART) were applied to evaluate the potential of multi-temporal ALOS/PALSAR HH polarization data for classification of crop type. Furthermore, comparisons of the two algorithms and three orbits including one type of descending and two type of ascending data were carried out. In the study area, beans, beet, grasslands, maize, potato and winter wheat were cultivated, and these crop types were classified using the data set acquired in 2010. The classification results of RF were superior to those of CART and the overall accuracies were 83.2% with the kappa statistics of 0.785. This work indicates the usefulness of regular monitoring of agricultural fields using the ALOS-2/PALSAR-2 system, which was launched in 2014.
We performed a deterioration promotion test to determine damages from the initial stages of deterioration for bearings and gears of pump facilities using an actual machine, and artificially generated three kinds of wear on the frictional surface. Using the actual machine provides a technical inspection to detect signs of deterioration in operating pump facilities, and contributes to techniques for maintenance management and functional diagnosis of facilities. In this study, we measured the numbers of metal wear particles that were included in the lubricating oil to monitor the state of the frictional surface during a test. Furthermore, we observed the form and size of the metal wear particles from the lubricating oil for quick recognition of deterioration. As a result of three wear tests, the number, form and sizes of metal wear particles in the lubricating oil were confirmed as appropriate for detecting signs of deterioration in the facilities.
In this study, to clarify the effect of the rotational stiffness of the contact surface between particles on the one-dimensional compressive stiffness of granular materials, the rotational stiffness induced by the stress and displacement distribution, in accordance with Hertz contact theory, on the contact surface of the spherical elements has been analyzed using the discrete element method. It became evident that the rotational stiffness of the interparticle contact surface increased the strength of the structure of the granular material. Since the strength governs the mechanical stiffness of granular materials, the rotational stiffness led to increased compressive stiffness. Further, the effect of the rotational stiffness of the interparticle contact surface was observed to be significant in the test case of particles that were less angular, and thus, could rotate easily between other particles. This was also observed in the test cases of high confining pressure conditions and of low-elasticity particles wherein the interparticle contact area was large. These results are expected to contribute to advancing the application of the discrete element method for granular analysis that is applicable to a wide range of testing conditions, such as those involving confining pressure or different types of materials.
As pointed out in reports, the low economic viability of the large-scale irrigation projects resulted to the decline in irrigation investments by official development assistance. This finding was mainly through the assessment of the present overall status in the agricultural development. There are very few studies, however, that provide for constraints in the actual implementation of projects. In one of the Philippine's large-scale irrigation projects, the Pampanga Delta Irrigation Development Project, an assessment of four development stages from planning, design, review and actual implementation was undertaken. As the results, it was clarified constraints such as uncertain necessity of the project, determination of development area without due consideration of financial viability, modifications of designs by the development stages and uncertainty of project evaluation through economic analysis. For effective implementation of the large-scale irrigation projects, it is indispensable to establish a flexible implementation system with due consideration to the financial situation of the developing country. The system should also include a more realistic evaluation method to assess project's necessity and goal focusing more on financial viability than economic analysis.
In rural communities in Japan, aging population and increases in mixed inhabitation have reduced the workforce available to maintain irrigation/drainage canals, so non-farmers' cooperation is required. To promote the participation of non-farmers in maintenance activities, the level of factors that influence their participation need to be effectively improved. From this viewpoint, a previous study proposed a method using “path coefficient” for selecting these factors. However, the application conditions for this method limit users. Therefore, we focused on a different method - a method using the indicator “maximum effective number of target persons” - that is likely used by more users. To clarify the application conditions of the latter method as an alternative to the former method, this study analyzed differences in the selected factors and characteristics of the two methods with a questionnaire given to 300 non-farmers living in Niigata City. The following results were observed: (1) there was no difference between the two methods for the first to third ranks of selected factors, (2) the latter method could be applied only to data from a complete survey, and (3) the application conditions for the method using “maximum effective number of target persons” should use data from a complete survey and select factors that are from the first to third ranks.
This study investigated the effects of the input parameters on analyses of the stability of earth-filled dams based on experimental design, in particular an orthogonal design. Computer-based experiments that conformed to an orthogonal design were carried out to increase the efficiency of the stability analysis, and a linear regression model was used to analyze the results of the numerical experiments. The standardized regression coefficients (SRCs) obtained from the regression analysis were used as indexes of the sensitivity of Fs to the input parameters. The results of the sensitivity analysis showed that the parameters related to the geometry of earth-filled dams, such as the height and slope gradient, have a greater effect on Fs than those related to the hydraulic characteristics of the fill materials.
Rice husk that is Poaceae as well as a reed and is known to be a concrete admixture that takes a pozzolanic reaction by ashing. In this research, in order to control the reed vegetation in the water area and use it sustainably, chemical identification of reed ash and strength characteristics of mortar that was mixed reed ash as a concrete admixture was researched. As a result, it was confirmed that the main component of the reed ash is SiO2 same with rice husk ash. Depending on the burning conditions, the reed ash can be a material that takes a pozzolanic reaction. Also, the strength characteristics of the specimen that was mixed reed ash, it was confirmed that the reed ash could contribute to the reduction of unit cement content. In addition, reed that vegetated brackish water convert into ashes, it was not necessary to be concerned about reinforcing rod corrosion because concentration of chloride ions soluble to water is less than 1/1,000 of the JIS.