In terms of maintenance, it is essential to evaluate deformation of sheet pile materials in corroded canal revetment. In this paper, for beam-type agricultural canals, inclination angles of steel sheet pile revetment are estimated by using image data with the Hough Transform (HT) which is one of figure detection methods. Detecting straight lines is performed on the digital images of steel sheet pile revetment. In analytical images of steel sheet pile canals, straight lines are detected which are based on not only steel sheet piles but also coping concrete, beams and cross section defects. It is revealed that inclination angles of steel sheet piles are estimated by the HT. It is suggested that inclination angles of steel sheet piles are evaluated by using digital images.

In order to identify indicators for controlling the deterioration of soil physical properties during large-sized farmland consolidation work, this study examined the soil moisture condition during work and soil physical properties before and after work. The surface soil of the study plot was light or silty clay and the subsoil was low peat soil. Since the surface soil (0 to 15 cm deep) before consolidation work is the plowed soil layer and the surface soil (15 to 30 cm deep) is the plow pan layer, it was found that the indicators of the consolidation work start can be shown by the soil moisture condition during construction work that controlls the deterioration of the physical properties of the surface soil (0 to 15 cm deep). In order to control the deterioration of the physical properties of the surface soil (0 to 15 cm deep), it was found that consolidation work needed to be carried out when the soil was in a dry condition with a pF of 2.0-2.5 (-9.8∼-31 kPa). Surface soil (0 to 15 cm deep) with a pF of 2.0-2.5 (-9.8∼-31 kPa) has a bearing capacity of 0.58-0.69 MPa, which is considered to be one of the indicators that can be used to decide when to start consolidation work after rainfall.

We identified environmental factors influencing habitat suitability for the endemic Japanese pond turtle, Mauremys japonica. To do so, we surveyed ten irrigation ponds in Shiso city, Hyogo Prefecture from May to November 2015 and collected data on 17 environmental variables. We examined relationships between each of these variables and the density of M. japonica as a dependent variable, using multiple regression analyses. We found that ponds with a higher density of M. japonica had structures such as exposed rocks and logs within the ponds that can be used for basking. Those ponds were also surrounded by less wooded and more open areas, providing suitable conditions for basking due to reduced shading. We also assessed the movement patterns of female M. japonica during the nesting season in June, by tracking them with data loggers attached to their carapaces. The maximum home range was 12,640 m² and the maximum distance moved from the point of release was 210 m. Turtles used various habitats around the ponds, in particular, the terrestrial areas immediately adjacent to the ponds as well as one of the nearby rice fields. These findings suggest that for the conservation of the endemic M. japonica, it is important to preserve not only ponds themselves but also the surrounding terrestrial habitats including paddy fields.

In this study, we proposed a low cost portable fishway system for quick improvement of the flow condition on the rapid slope section of agricultural channels that divide habitats of aquatic animals. As a result of arranging the blocks for adjusting the flow condition in the fishway in a staggered array according to the length of the back water occurred by a block, the water depth was increased more than 5 times that before the installation of the fishway, and the flow velocity was reduced. In particular, the flow velocity immediately below blocks was reduced to about 20% of that before the installation, and it was thought that it would function as a resting place for aquatic animals using the fishway at the site. In field experiments, fish with a body length of 3.4 cm or less migrated upstream by the fishway. It was confirmed that small fishes used the migration environment constructed in a short time by the proposed fishway system.

Recently, concrete facilities in snowy cold regions have become subject to survey and diagnosis of frost damage and abrasion, and repair and reinforcement against such damage. In such survey and diagnosis, it is important to understand the deterioration that has occurred in the concrete surface. In this study, we took core samples and conducted a detailed survey of concrete that was exposed to water at open channels or head works in Hokkaido. We found that concrete facilities that have been in service for a long time in snowy cold regions may have serious deterioration involving declines in mechanical properties, such as reductions in compressive strength and relative dynamic modulus of elasticity, and experience combined deterioration of frost damage at and around the surface and abrasion involving the leaching of calcium.

Internal loading method (ILM) was applied to the buried and the unburied RC pipes, in order to evaluate the effect of restraint by the earth pressure for cross-sectional stiffness of the pipes. As a result, the relationship between load and deformation of the buried RC pipe had strong positive correlation. It was confirmed to be same as the case of earth pressure didn't act. It was verified that ILM deformed the cross section of the buried RC pipe into ellipse and accrued local bulges at loading points, considering vertical and horizontal earth pressure and circumferential strain distributions on outside of the pipe. The circumferential strains at top and bottom on the outside of buried RC pipe at a certain deformation (20μm) increased due to the effect of restraint by earth pressure. Finally, it was shown that the stress from cross-sections of an RC pipe (diameter: 400 mm) was transmitted to less than 40 cm along the longitudinal direction.

The purpose of this study is to clarify effects of light environment differences due to the complex topography in the mountainous areas on paddy rice yield. The relationships between paddy rice yield (Koshihikari BL) and meteorological environments, especially light condition, were investigated in the Higashi-shimogumi district, Tokamachi City, Niigata Prefecture for three years. The results show that no significant difference in yield was found between two fields with different light environment. As a factor, total number of paddies per 1 m² (sink ability) was significantly positively correlated with the cumulative PPFD during the 60 to 30 days before heading, 2) the photosynthetic ability of individual leaves in the lower-light filed was increased due to the adjusting function against lower-light condition, 3) canopy's sink ability in higher-light field was greater than that in lower-light field and the assimilate production to satisfy sink was not enough, resulting ripening rate in higher-light field was lower than that in lower-light field. These results will assist in the model development for predicting rice yields in mountainous regions and agricultural technologies that make us of diverse weather conditions.

In the repair design of agricultural irrigation facilities, it is important to assess the durability performance of the repair material before construction. In this study, we estimate the acceleration factor of the accelerated weathering test for the organic repair material used in the construction of an agricultural canal to protect it from deterioration factors. We identify the relationship between the exposure period and the accelerated weathering test time by comparing the rate of the deterioration area in the field survey with that in the accelerated weathering test. Consequently, the surface deterioration above the water level, over eight years of exposure, corresponded to that of 1,500 h of accelerated weathering test in the side wall facing north-northwest, and 2,000 h of accelerated weathering test in the side wall facing south-southeast. It was assumed that in this study area the exposure period and the accelerated weathering test time are almost linear.

A donut type TBM, which has an opening at the center of its cutter head, is proposed as a hard rock TBM (full-face type TBM). The proposed donut type TBM, has various mechanical excavation characteristics that are different from those of conventional full-face type TBMs, including elimination of center cutters due to the center of the face not being excavated and reduction in the number of cutters installed as a result of reduction of the area excavated. In this study, in order to evaluate these excavation characteristics, new experimental equipment that excavates the entire area that comes into contact with the cutter head was produced and used to excavate a high-strength mortar specimen. The excavation experiment using this equipment reproduced TBM's rock breakage mechanism and demonstrated that the center cutters cause an increase in the cutting resistance. The study including the experiment showed that the donut type TBM has a greater excavation speed, which leads to a decrease in a specific energy.

To clarify the optimum compaction condition for soil-bentonite mixture, shear strength of saturated specimens which have different dry density and degree of saturation at the end of compaction were evaluated by consolidated constant volume box shear tests. It was revealed that shear strength of saturated soil-bentonite mixture became larger with an increase in degree of saturation at the end of compaction, and this effect became larger with an increase in dry density. In the compaction of soil-bentonite mixture, great attention needs to be paid to water content of soil-bentonite mixture. However, suitable compaction condition for soil-bentonite mixture in the aspect of achievement of higher shear strength was similar with that for general soil to achieve lower hydraulic conductivity. Therefore, the quality control method currently used in construction of reservoirs would achieve not only lower hydraulic conductivity but also higher shear strength of soil-bentonite mixture.

Direct shear tests using specimens which have the identical condition of bonded interface but have different shapes of cross sections were conducted to determine an appropriate method to evaluate shear bond strength between inorganic materials. The maximum shear stress generated in bonded interface at bonding failures were significantly affected by the shapes of the cross sections of specimens and the ratio of the maximum value to the minimum value were around 1.7. In contrast, the average shear stress generated in bonded interface at bonding failures were almost identical regardless the shapes of the cross sections of specimens. These results indicate that detachment at bonded interface due to shear stress occurs when the average shear stress reaches a certain value, which can be regarded as the shear bond strength. Therefore, it can be concluded that, in direct shear test, shear bond strength should be evaluated based on the average shear stress.

Previous studies on the flow through the gates have exclusively directed towards discharge evaluation, and the upstream depth evaluation, which is directly related to inundation due to extraordinarily heavy rain frequently occurring in recent years, has not been treated as the major problem. This study attempts to evaluate the upstream depth of sluice gates for both free outflow and submerged flow on the basis of fundamental hydraulic equations. As for free outflow, momentum theorem was applied with the approximations equivalent to the previous studies, and the mutual dependent relationship was deduced between the critical depth, upstream depth and gate opening. The relationship was formulated employing the experimental data, then the formula for the upstream depth was obtained. As for submerged flow, a cubic equation for the upstream depth was obtained combining Bernoulli's equation applied to upstream cross-section and contraction cross-section and momentum theorem applied to the water between contraction cross-section and downstream cross-section. The derived equations for the upstream depth evaluation showed good agreement with experimental data obtained in the laboratory.

We investigated effects of incorporation of wood-based biochar and composted cattle manure on physicochemical properties of a sandy soil with low organic carbon. The total carbon content, soil pH, cation exchangeable capacity (CEC), easily readily available water capacity and ratio of macro-aggregate (>1 mm) of the soil significantly increased as incorporation ratio of biochar increased. Co-application of biochar and compost significantly increased total carbon content, soil pH, CEC and ratio of macro-aggregate (>1 mm). Although the readily available water capacity was enhanced with solo-biochar application, that was not effectively increased with co-application. In addition, excessive increase in soil pH after the compost application should be paid attention. We need more efforts to seek effective combinations for the sandy soil with low carbon content.

With regard to the collapse of farmland stone walls, the groundwater movement behind the farmland stone walls during heavy rainfall and the collapse of the farmland stone walls in order to clarify the relationship between the two, a soil moisture meter and a water level gauge were installed behind the stone wall in the farmland to measure the water movement. These results showed that there were vertical water flow along the stone wall and horizontal groundwater movement along the bedrock in the farmland. The simple equation that was the SOIL WATER INDEX multiplied by 10 and subtracted by the value specific to the observation site predicted the process of increase and peak groundwater level accurately. Then, by using the cumulative predicted groundwater levels as a risk indicator, the collapse risk of the farmland stone walls for the entire region was estimated. The number of collapsed farmland stone walls for the past disaster record was predicted relatively accurately by the indicator. The result showed that the risk of stone wall collapses in agricultural land increased from rainfall of landslide warning level in the SOIL WATER INDEX.

The conventional method of seismic performance verification analyzes the seismic response and the permanent deformation individually and does not allow for assessing the seismic response across the entire range of possible soil deformations. This paper develops velocity-based single-field Space-Time Finite Element Method (v-ST/FEM) for the seismic response analysis of fill dams which undergo the permanent deformation during strong-motion earthquakes. The results of a nonlinear spring analysis obtained by the time integration method of v-ST/FEM are compared with those by Newmark-β and those results highlight the effectiveness of v-ST/FEM in reducing numerical error and increasing stability. An elasto-plastic constitutive model based on Mohr-Coulomb criterion is implemented in v-ST/FEM to compute the dynamic ground motion and the permanent deformation of fill dams and 1D and 2D analysis examples are studied in the infinitesimal deformation range.

Implementing countermeasures for improving the seismic stability of the many reservoirs that exist across Japan is a matter of urgency, and the demand for low-cost stability measures is increasing. This paper looks at the slope protection work that has been established for reservoirs in order to prevent wave erosion, work not normally considered in stability calculations. It verifies the effects of such reservoir stability improvement through a centrifuge model experiment and an analysis using a dynamic finite element methodology. Comparisons are carried out with facing blocks, block mats and concrete mats, which are all generally used in reservoir slope protection. The results clearly show that concrete mats, strong single structures made of fabric and concrete, are highly effective in improving the stability of reservoirs due to the way in which the edges of the mats are fixed to the earth. Moreover, it is confirmed that in order to further augment the effects of using concrete mat protection, the requirements are (1) to increase the strength of the fabric material or lessen the permissible distortion and (2) to deeply embed the lower part of these mats.

We evaluated hydraulic and water serviceability functions of a farm ditch that was changed from an open channel to a gravitational irrigation pipeline fed by hydrostatic pressure from an open channel. The evaluation was based on a steady flow analysis, hearing investigation and field surveys in a paddy irrigation district of Yamagata prefecture. The steady flow analysis showed that the effective water head in the pipeline was less than 0.3 m when all hydrants were opened, but the effective water head could be increased to more than 0.3 m by reducing the number of open hydrants. The hearing investigation showed that the pipeline maintained its effective water head during rotational water delivery and the labor of water management was reduced by operating a hydrant. The field surveys showed that the water supply met the fluctuating water demand with less than the plan discharge in the field irrigated by the pipeline, whereas water delivery loss was about 40% of the plan discharge in an adjacent field that was irrigated by an open channel. The field surveys also showed that the flow velocity of the pipeline was less than 0.3 m/s and the pipeline function might be degraded.

Estimating soil water and heat flows during freezing and consequent frost depth is important to conserve and manage farmland in cold regions. In this study, we performed column-freezing experiments using Andisol with three different initial water contents (θ_init) to investigate effects of soil water content on heat flow during freezing. When the surface air was cooled to subzero temperature, the soil was frozen from the surface and the soil temperature and liquid water content decreased as well as the ice content increased. Despite same cooling condition was applied, soil froze slower with higher θ_init. Amount of water flowed from unfrozen to frozen layer of the soil was highly depended on the hydraulic conductivity of the unfrozen layer. Analyzing heat balance of the column experiments revealed the followings: (i) Sensible heat released from freezing soil little varied with θ_init. (ii) Latent heat was highly dependent on θ_init. (iii) Total and surface heat fluxes became higher with increasing θ_init. (iv) Advection accounted for small part of total heat flux and did not depend on θ_init very much.

Recently, 3-dimensional measurement can be conducted easily by using the UAV as like drones. Although the precise geological survey has been possible by the new technology, the 2-dimensional dynamic finite element analysis is still common in the design problems. The 3-dimensional finite element modeling technic by extending the 3-dimensional measurement results to the subsurface area, has been developed by the authors. In this research, the 3-dimensional measurement is conducted by using a drone, from the taken pictures of an earth-fill dam, 3-dimensional point group data are generated, and 3-dimensional finite element model of the earth-fill dam is completed from the point group data. Based on the model, 3-dimensional seismic response analysis can be conducted. Consequently, from the analytical results, the structural weak points of the earth-fill dam have been clarified, and in the comparison between 2-dimensional and 3-dimensional analyses, the possibility of underestimation for the seismic behavior by the 2-dimensional analysis have been suggested.

For a region with no direct measurements of net radiation, net longwave radiation is estimated using air temperature, relative humidity, sunshine duration by FAO’s or Penman’s formula, and net shortwave radiation is estimated using solar radiation and albedo. However, the coefficients of these formulas were determined by foreign meteorological data, not the Japanese ones. This paper describes that the coefficients are determined on daily and hourly data based on the three national research institutes in Japan. The coefficients are determined by optimization procedure from measured longwave radiation at the three sites as possible as reproducing the longwave radiation by the formula. As a result, the coefficients have a difference in region by region; therefore, the coefficients should be determined principally for an individual region. By limiting the period to the crop growing season (April to October) that has a snowfall region, the estimation accuracy of the formula was remarkably improved. In the analysis of albedo based on the above materials, the effect of the hourly changes of the albedo on shortwave radiation shows about 0.20 during the crop growing season, excluding the snow season.

This study clarified the factors that facilitate consensus in a farmland improvement project through investigating the area where Farmland Consolidation Project related Cropland Intermediary Management Institution has been implemented since 2018. The method of project implementation was assessed with an interview survey, land use survey, and questionnaire survey to be employed to identify intentions of both landowners and renters. The study area is an orchard located on a slope—it is particularly difficult to gain landowners' agreement for a land improvement project. This is primarily due to the increased local financial burden from higher earthwork volume and the extended nonprofit period associated with felling citrus trees. The investigation revealed that the following three factors facilitate the project. Firstly, there is a consensus in the intentions of landowners who want to protect the area from landslides and the renters who wish to manage and operate farmland in favorable conditions. Secondly, the Farmland Consolidation Project imposes zero financial burden, and there is a minimum financial risk to landowners. Thirdly, there is a sense of security based on the guaranteed long-term loan agreement between landowners and renters provided by the intermediation of the Japan Agriculture Cooperatives and the Cropland Intermediary Management Institution.

We examined a crop classification method that uses multi-temporal X-band and C-band synthetic aperture radar (SAR) satellite data from the perspectives of accuracy and efficiency. Backscattering coefficients and several polarimetric parameters were derived from each SAR scene, and three types of decision-tree machine learning algorithm were employed for the classification using derived variables. The most accurate algorithm of the three was Extremely Randomized Trees (ERT). We compared the accuracy and characteristics of the classification tendency between C-band and X-band data using ERT. The results obtained for several scenes showed that the C-band had higher accuracy than the X-band for almost all patterns. We established a classification method by selecting satellite scenes. The method is efficient and highly accurate in classification without using all scenes from both bands, so as to reduce utilization costs. The combination of the C-band up to early July and the X-band from mid-July onwards achieved the same accuracy as classification using all C-band and X-band data. This method is proposed as a particularly efficient crop classification method.

In recently years, acoustic emission (AE) method has been proposed to detect drought-induced stress as a biological information in plants. For the practical application of the AE method to measure drought-induced stress in plants, it is necessary to extract AE generated in plants (burst-type AE) from a large number of environmental noises. In this paper, automatic discrimination between burst-type AE and noises is attempted using decision tree and random forest classifiers. Both decision tree and random forest classifiers could discriminate between them with an accuracy of more than 0.85. In particular, the random forest classifier with many explanatory variables mitigated overlearning and discriminated the burst-type AE more accurately.

This study proposed some measures for the sustainable management of an irrigation pond in a rurban area in Japan (Yanagisawa village, Ueda city, Nagano Prefecture). This paper focused on the status of implementation of cultivation and analyzed the factors motivating participation in the management of the pond using a questionnaire survey.

Multilinear regression analysis showed that cultivators who recognized the value of the flood mitigation function were more motivated to participate in the management of the pond than non-cultivators. Thus, it is suggested that an exchange program to provide agricultural experiences for non-farmers living in the area should be implemented to introduce them to cultivation and pond management practices. Finally, it was recommended that the pond management system was reviewed so that females can participate in management because many females expressed their desire to do so.

We considered the material characteristics of embankment and foundation ground round the small earth dams for irrigation damaged by the past large-scale earthquakes in five prefectures to use a Geographic Information System (GIS) with the reservoir ledger data. These small earth dams for irrigation could be the historic agricultural hydraulic structures supported cultivated land development during modernization in Aomori Pref. and Fukushima Pref.. As the results of considering quantitatively the material combination ratio of the embankment and foundation ground of the existent small earth dams for irrigation around those dams reported to damage by liquefaction in Aomori Pref., Akita Pref. and Hyogo Pref., there were a lot of the foundation ground materials with sand and it indicated the possibility of damage by liquefaction. Also, because there was no great influence by the possible ratio of damage occurrence even if assuming that the foundation ground in many uninvestigated places was the same material as the embankment, the importance of making the material properties of embankments clear by being able to investigate easily the embankment material was indicated.

Many irrigation tunnels were constructed using the mountain tunnel method. Because of the immaturity of this construction technology in the past, some tunnels have a continuous void behind a concrete lining. In this study, destructive testing of horseshoe-shaped irrigation tunnels was carried out to identify the effect of that void. The specimen used consisted of a mortar lining was surrounded by ground. The neighboring ground was made with low-strength mortar. A vertical deformation was executed to specimens with different void ranges.

In cases where there was no void, or the range of the void was 30 degree, the lining was deformed in the vertical direction. Whereas, in cases where the void range was 60 or 90 degree, the neighboring ground pushed the lining into the tunnel with the progress of the deformation. Finally, a longitudinal crack occurred in the arch of the lining, and the inner section was expanded in the vertical direction and reduced in the horizontal direction.

The maintenance and renewal of social capital accumulated during the period of high economic growth in Japan must be carried out under severe financial constraints, and the national government has formulated a basic plan for extending the life of infrastructure and is currently working on it. The national Kahokugata water area reclamation and agricultural land improvement project completed in 1986 is one of them, and the renewal project has been started. This study investigates and analyzes the maintenance history of the tidal lock and drainage pump stations as main facilities of the Kahokugata reclaimed land from the construction of these facilities to the present. We extracted and pointed out the importance of the designing of the maintenance cycle and the implementation timing of the countermeasures to extend the life. According to these results, it is necessary to establish a management system based on the facts from the actual maintenance cost in the previous projects, when implementing sustainable maintenance management based on the stock management of facilities in the future.

Irrigation scheduling in converted paddy fields is very important to avoid wet and dry stress. The objective of this study was to develop a simple method for estimating the amount of water stored in the cultivation layer of converted paddy fields using an agro-meteorological database. A bucket model with two parameters, maximum and minimum water storage depths, was employed for estimation. Two parameters were specified based on the soil water measurement in fields and compared with soil water characteristic curves. The simple method was applied for three converted paddy fields. It was found that the estimated amount of water stored in the cultivation layer is in excellent agreement with the measured data in comparison to both field capacity and permanent wilting point specified as the two parameters. Moreover, a different method of soil water measurement (two kinds of capacitance sensor and two installations of the sensors) to specify the two parameters hardly affects the estimated results. Thus, we proposed the water storage ratio which is calculated from the amount of water stored in the cultivation layer, as an indicator for irrigation scheduling.

This paper reviews the research on the detection of elastic waves generated from plants by the Acoustic Emission (AE) method during the 54 years from 1966 to 2019, and summarizes the future issues regarding the use of AE methods in agricultural production. Nowadays, AE generation behavior and AE characteristics of energy and frequency can be acquired with high precision. So, the AE method is useful for evaluating vulnerability of trees and diagnosing the precise growth of agricultural products. Future research topics include networking of environmental, management and biometric information to contribute to the spread of smart agriculture. It is necessary to establish a method for processing a large amount of acquired waveform data and an accurate method for discriminating AE waves with different waveform features. In addition, it is necessary to elucidate the bubble generation mechanism in the vessel and to examine the relationship with the vessel structure, plant physiology and AE characteristics.