Constructing civil engineering structures, temporaly or permanent water proofing sheet piles often are used. The stability of seepage failure are carefully applied to those sheet piles, although many troubles of seepage failure were reported. On this problem the predictive method of the deformation and critical water head is required. In this study we carried out the model experiments which were designed for studying the seepage failure of soil behind fixed sheet piles and our elasto-plastic finite element method was applied to verify the effectiveness. Terzaghi method is very famous method for this problem and Terzaghi method was investigated by experiments data. As a result, it was confirmed that elasto-plastic finite element method was effectiveness and Terzaghi method was useful for this problem.
Turbid water inflow from paddy fields to river and lake especially during “spring agricultural practice in paddies” period which consists of plowing, paddling, and transplanting, is causing concern as one of the non-point source pollution. In a paddy watershed (4 ha) located on Lake Biwa basin, the investigation of suspended solid (SS) concentration and SS load at the end of the drainage and visual observation of progress in spring agricultural practice were carried out from the middle of April to the end of May 2004. During the investigation period, SS concentration and load showed two peaks. Relation between SS peaks and progress in spring agricultural practice suggests that movement of soil particles with water leakage through percolation contributes to the first peak, emerging between the beginning of irrigation and the practice of paddling. The causes of the second peak, emerging between the completing of paddling and the transplanting, are suggested to be overflow during paddling and artificial drainage just before transplanting. The loads during spring agricultural practice are 71 kg/ha/day for usual SS fraction (>1.0µm) and 104 kg/ha/day for fine SS fraction (>0.3µm). Many approaches for reducing the turbid water so far are mainly planed to measures against the second peak which is controllable by agricultural practices, however, the results indicated that it is also important to take effective measures against the first period.
The spatial distributions of denitrifier numbers in the tidal sediment (0∼4cm depth) in the interior parts of the Ariake Sea changed largely with the properties of tidal flat and seasons. The denitrifier numbers in summer were many in the muddy tidal flat in the interior parts of this bay and about 18,000MPNs/g-dry on the average. But, its numbers were few in the sandy and mud-sandy tidal flats in the east and west coast areas and about 1,700MPN/g-dry on the average. A close relation between the denitrifier numbers in the tidal sediment (0∼4cm depth) and its mud (clay and silt) content was found and its numbers rose with the increase of mud content. The vertical distribution of denitrifier numbers in the muddy tidal flat was high near the surface layer (0∼2cm depth) where Eh was almost zero in summer, but its distribution decreased in other season. The denitrification rate in the muddy tidal flat changed largely with time (0.35-13.86mg-N·m-2·d-1). The denitrification activity in the muddy tidal flat was assumed to be affected by the environmental factors and substrate concentration other than the denitrifier numbers.
Wind rises particular strong in April and May at Okunakayama Highland, located in Northern Iwate, where wind erosion damages highland vegetables and crops. In order to realize actual situations of wind erosion, quantity of wind- drift soil particles, wind velocity and soil water content were observed during April and May for three years from 2005 to 2007. It was found that wind erosion occurred when soil water content fell below 28% and wind velocity reached 8m·s-1. Also soil water content fell to nearly 28% within three days after significant rainfall. Past occurrence situations of wind erosion was estimated by using the data of drought days and wind velocity, based on the weather data in April and May of past 30 years. It was found that wind erosion was the yearly event, especially it occurred between mid-April and beginning of May. Also found that the quantity of wind-drift soil particles increased between 11 am and 3 pm, and wind erosion rarely occurred in the morning, the evening and the mid-night.
This is a print of a camera-ready Japanese manuscript for the Transactions of JSIDRE. This will provide an example and directions for the layout and font size/style to be used. Please refer to this when preparing the headings, figures/table and text of your manuscript. The manuscript should be submitted on A4 size. Changes in temperature, soil moisture, and carbon and nitrogen contents were measured in Andisol under soil surface burning. Soil samples were packed into an unglazed cylinder of 15 cm inner diameter and 30 cm high. Charcoal was burned for 6 hours on the surface of the soil column. During the burning soil surface temperature rose to between 600-700°C. In initially wet soil, rise in soil temperature was retarded for a while at around 95-100°C. On the other hand, in initially dry Toyoura sand showed more rapid temperature increase without retardation. The temperature retardation in the wet soil could be caused by consumption of latent heat by vaporization of soil water. Rate of proceeding of the 100°C front was proportional to square root of the burning time. This indicates that higher the initial volumetric water content, shallower the depth affected by burning. Soil samples suffered temperature above 500°C still had total carbon and nitrogen contents of over 20 and 1 g kg-1, respectively, whereas the soil that was heated up to over 500°C by muffle furnace contained less than 0.4 and 0.1 g kg-1 of the carbon and nitrogen.
Leaping behavior of Ayu (Plecoglossus altivelis altivelis), which is often seen in a pool-type fishway and groundsel, is discussed using video-recording of their migration above and below the water surface. The video was recorded through four types of experiments/observation prepared to clarify their leaping characteristics, i.e., 1) laboratory experiment using a testing flume, 2) on-site experiment using a slope temporary installed in an irrigation canal, 3) on-site experiment in an existing fish laddar and 4) field survey at a pool of groundsel. As a result, though many of the Ayu seem to accerelate toward the water surface just before leaping, their swiming speed varies widely and speedup and slowdown are repeated inconsitently, which would appear that the accerelation does not contribute directly to the leaping. It also becomes apparent that the swim required for the leap is within an extremely short period just below the water surface. In addition, the angle and the height of the leap finally attained depend on the depth of the pool and the fish tends to remain in the pool when the depth is too large. It indicates that the pool-depth of 20cm might be enough for Ayu to leap over small falls, which was conventionally considered insufficient.
Soil erosion and runoff have led to agricultural and environmental problems throughout the world. Especially in tropical or subtropical region, the corals have been damaged due to oversupply of sediment and nutrients from the river basin including agricultural zones. Therefore effective treatments which can reduce sediment yield in the farmland are necessary. The authors have carried out field plot tests in sugarcane fields to compare the amounts of sediment yield depending on the difference of agricultural practices. From the observations, no-tillage, intercropping, and grass strip reduced sediment yield by 89%, 45%, and 17%, respectively. Moreover, the managements of perennial sugarcane farming and combination of strip tillage planting and intercropping were found to reduce sediment yield by 85% and 69%, respectively. Therefore a sugarcane farming cycle combining these two managements is supposed to be the best-case scenario to reduce sediment yield.
The sedimentation and self-weight consolidation processes of thoroughly disturbed soft marine clay are relevant both to land reclamation work and to sediment accumulation on tidal flats of coastal lowland plains. The influences of grain-size distribution, iron oxide content and organic matter content on these processes and the final water contents of a low-activity mud were investigated at water contents from 500 to 6,000% over salinities ranging from 30 to 0.5g/L. Particle size distribution had a large effect; specifically, the lower the clay content the more rapid the differentiation of an upper sediment boundary and the self-weight consolidation of the accumulated sediment. Iron oxide addition had little effect on these characteristics for this low activity clay. Peroxide destruction of the original organic matter suggested that it had a mildly flocculating effect; the addition of 5% organic matter, in the form of fulvic and humic acids, had a dramatic dispersing effect and inhibited sediment accumulation and consolidation for all conditions tested. The experiments indicate that use of dredged mud with low organic matter content, lesser clay contents and lesser swelling clay content, applied at the lowest water content that is feasible, will provide for the most rapid sedimentation and self-weight consolidation in reclamation projects.
The limit state design has been introduced into the design criteria for geotechnical structures. This paper attempts to apply the reliability design method at Level II to the bearing capacity of the foundations of open channels from the viewpoint of the limit state design. To examine the applicability of the proposed procedure for practical structures, the reliability index is computed for evaluating the stability of the foundations of existing open channels designed by the usual method. It has been proven that the existing design method is on the safety side by obtaining larger values for the reliability index to be computed as 5.0 for sandy soil and 3.0 for clayey soil.
We calculated nitrogen balances on farm gate and soil surface on large-scale stock farms and discussed methods for reducing environmental nitrogen loads. Four different types of public stock farms (organic beef, calf supply and daily cows) were surveyed in Aomori Prefecture. (1) Farm gate and soil surface nitrogen inflows were both larger than the respective outflows on all types of farms. Farm gate nitrogen balance for beef farms were worse than that for dairy farms. (2) Soil surface nitrogen outflows and soil nitrogen retention were in proportion to soil surface nitrogen inflows. (3) Reductions in soil surface nitrogen retention were influenced by soil surface nitrogen inflows. (4) In order to reduce farm gate nitrogen retention, inflows of formula feed and chemical fertilizer need to be reduced. (5) In order to reduce soil surface nitrogen retention, inflows of fertilizer need to be reduced and nitrogen balance needs to be controlled.
Internal erosion caused within soil structures, such as earth dams and irrigation ponds, leads to the piping failures of the structures. Most of studies on the internal erosion of soils have been experimental and the computational method to analyze the phenomenon is currently limited. The purpose of this study is to propose a numerical method for solving the internal erosion and the transport of eroded soil particles and to verify the applicability of the method. In this paper, three equations concerning the seepage flow, the change of porosity due to internal erosion and the transport of the eroded soil particles are introduced and computationally solved. The equation of the seepage flow is solved with Finite Element Method, and Finite Volume Method is applied to the equation of the transport of the soil particles. It is shown that the numerical approach can reproduce the experimental data of the previous study.
In a kind of concrete canal, repair materials are applied for recovery of the deteriorated functions. However, due to the re-cracking of the repair material caused by the fluctuations of the crack width, there is a great possibility that the functional deterioration reoccurs after the repair. In this research, High Performance Fiber Reinforced Cement Composite (HPFRCC), which has multiple cracking feature, was evaluated as a repair material to prevent the functional deterioration after the repair. HPFRCC and mortar specimens were cracked and examined by permeability test. As a result, it was clarified that the leakage from the HPFRCC specimen was very little compared with the leakage from the mortar specimen. Moreover, it was confirmed that the leakage from the narrow cracks were gradually decreased.
The principals and procedures of ELISA (Enzyme-linked Immunosorbent Assay)-based determination of pesticides (Fenitrothion) in environmental samples were reviewed, and the applicability of the ELISA method for groundwater quality monitoring were validated through the experimental tracer tests in soil columns and the field test in Okinoerabu Island. The test results showed that the ELISA method could be useful not only for screening but also for quantitative analysis of pesticides. In the experimental tracer tests in soil columns, the retardation of pesticides leaching compared with conservative tracers were observed. In the field test, the contamination of the pesticide was detected in groundwater samples in Okinoerabu Island, even though the targeted pesticide was considered to be applied to the upland field 4 months ago. In order to investigate the transport and fate of pesticides in groundwater taking into account retardation from the field to groundwater table and the residue in groundwater, continuous observations of pesticides in groundwater are in a strong need, and the ELISA method is applicable to the long-term quality groundwater monitoring.
In recent years, a technique for the functional diagnosis of various structures and a verification approach have been developed in order to increase the life-span of agricultural irrigation facilities. This permits visual inspections to understand structural conditions of deteriorated hydraulic structures and to assess their soundness indices. To update or upgrade an agricultural irrigation canal on the other hand, it is necessary to establish performance-based design of the system. In addition to structural performance, this performance-based design system should include the evaluation of hydraulic performance and water serviceability. This report targets the irrigation canal system in an irrigation district consisting of paddy fields. It provides examples of the generation of a diagnosis chart for irrigation canal systems that can be effective as an investigation method involving functional diagnosis. This report also discusses a diagnosis example to evaluate the problem examination priority.