This paper evaluated an influence of backfill relaxation on progressive failure and particle size effect in retaining wall problem on passive mode with dense sand, by comparing with experimental and calculated results. The relaxation process was conducted by pulling the wall (active mode) before the test was performed on passive mode. The relaxation displacements (R_d) were given for 0.0mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 2.0mm and 4.0mm. Sands used for the test were Toyoura sand and Soma sand because of evaluating a particle size effect due to progressive failure. The height of sand mass was 10cm and earth pressure was measured by earth pressure cells. The calculation was performed using the finite element analysis proposed by Tanaka. This analysis employed a constitutive model in which the non-associated strain hardening-softening behavior of an elasto-plastic material was assumed and the effect of shear band thickness was introduced, and it was available to predict the anchor, footing and retaining wall problems. The conclusions obtained from the results could be summarized as follows;
1. There was no backfill relaxation until the relaxation displacement as same as the mean grain diameter of sands.
2. Using R_d/D₅₀ (R_d; active displacement, D₅₀; mean grain diameter), until R_d/D₅₀ of 1, there was no backfill relaxation but there was clear evidence of particle size effect. Within the R_d/D₅₀ range from 1 to 5, backfill relaxation was recognized and coefficient of passive earth pressure decreased with increasing active displacement. Above R_d/D₅₀ of 5, the coefficient of passive earth pressure approached to residual constant value because of forming backfill relaxation completely, and there was not clear evidence of the particle size effect. These phenomenon was concerned with the influence of backfill relaxation.
3. The difference of progressive failure and particle size effect dependent on backfill relaxation was attributed to forming a domain of loose density in sand mass.

View full abstract

This study was conducted in order to define the actual conditions and the characteristics of the lanned reuse of the treated wastewater from rural sewerage for irrigation. This study was carried out with the data of 18 rural sewerage and 4 public sewerage. Main findings were described below. 1) The main purpose of the utilization of treated wastewater was the prevention of the irrigation water shortage. Fertilizer effect of the treated wastewater and the water purification function in the farmland were not considered. 2) The treated wastewater was mainly utilized for paddy fields. However, the treated wastewater was also used for many kinds of field crops. Many treatment plants utilized the treated effluent for the plural kind of crops. 3) In many cases, the treated wastewater was used throughout the irrigation season every year, not only in the drought years. 4) The sending systems of the treated wastewater for the farmland were very diverse, especially with the small treatment plants. 5) The planning conditions of treated wastewater were determined in accordance with the usual standards of rural sewerage or usual regulations for general treatment plants without the wastewater reuse. 6) A wide variety of wastewater treatment systems was employed in rural sewerage. In this study, the problems for the actual conditions of the reuse systems of rural sewerage were also examined.

View full abstract

This study measured the physical characteristics that characterized the pleasantness of stream sounds. Two kinds of sensory test were carried out on 117 subjects to determine the most appealing loudness and pitch of stream sound. The results of the tests and analysis were as follows:(2) The appeal of the loudness of stream sound could be evaluated by the sound level. However, the pleasantness of loudness was affected by the pitch of the stream sound and bythe manner in which the subjects listened to it.(2) The appeal of the pitch of the stream sound was affected by the local fluctuation of the sound pressure levels over the frequency range of 200 to 8, 000 Hz.(3) A psychological model of stream sound was formulated by a linear discriminant function composed of the sound level and the difference between the local minimum value of the sound pressure level over the frequency range of about 200 to 500Hz and the local maximum value of the sound pressure level over the frequency range of about 1, 000 to 4, 000Hz.

View full abstract

The concentration of nitrogen and phosphorous in field water standing on clay loam in eight pots was measured 1, 3, 5 and 7 days after the experiment was conducted. The experimental conditions were as follows: 1. Unpuddled and no fertilizer, 2. Puddled and no fertilizer, 3. Unpuddled and phosphate fertilizer, 4. Puddled and phosphate fertilizer, 5. Unpuddled and synthesized chemical fertilizer, 6. Puddled and, synthesized chemical fertilizer, 7. Unpuddled and coated fertilizer and 8. Puddled and coated fertilizer.
By analysis of variance, the effective factor for nitrogen and phosphorous concentration was the puddling operation. The mean value of T-N concentration in the first day was 9.9mg/L for puddled pots and 2.1mg/L for other unpuddled pots; 2.2mg/L and 0.21mg/L for T-P respectively. The effect of the kind of nitrogen fertilizer seems to be more significant with synthesized chemical fertilizer than others.

View full abstract

River load discharges during rainstorm runoff were investigated on two watersheds in the southwestern part of Hokkaido, Japan. One watershed is entirely covered by forest, and the other also has forest, but agricultural activity is prominent. The discharge-load relation differs in each event and between watersheds. By using Water Storage of Watershed (Is) as an index of the hydrological conditions of the watershed, we evaluated the characteristics of river load discharge during rainstorm runoff. The Discharge-Weighted Average Concentration (C_dwa) is higher when the rainstorm runoff occurred on low Is condition on the agricultural watershed. Forested watershed did not show such a tendency. The range of C_dwa on forested watershed is much less than that of agricultural watershed. In some cases of low Is in forested watershed, the C_dwa shows a decline, especially in the summer season. The above-mentioned characteristics were very apparent for NO₃-N.

View full abstract

The results of a consolidation test for remolded clays were arranged by three methods, e-log p (e: void ratio, p: consolidation pressure), log e-log p and n-log p (n: porosity), and the characteristics of each arrangement method were studied. For remolded clays, the log e-log p and the n-log p relationships can be found as two groups of straight lines of different gradients, but both the elastic consolidation and plastic consolidation regions of e-log p relationship are expressed as a curve. In this paper, the porosity of consolidation yield n_y, consolidation yield stress p_y, and the gradient of the plastic consolidation region C'_p were represented by the log e-log p method, and n_c, p_cn and C'_cn were represented by the n-log p method. After the meaning and the relationships of each value were studied, the results obtained are as follows, 1) The relationship between n_c and initial porosity n₀ can be expressed as an exponential equation with a high correlation coefficient. 2) p_cn decreases with an increase of liquidity index I_L, and the relationship between p_cn and p_y can be expressed as p_cn≥p_y. 3) The ratio of the C'_cn to C'_cfor remolded clays can beexpressed as_C'_cn/C'_c=(10-0.86n₀/10)²4) The ratio of the C'_cn to C'_p for remolded clays can be expressed as C'_cn/C'_p=1.98n₀(1-0.86n₀/100)_5) The ratio of the C'_p to C'_c for remolded clays can be expressed as C'_p/C'_c=1/2.30(100/0.86n₀-1)

View full abstract

The present study was an attempt to estimate the mass budget of an irrigation pond located at Kyotanabe area. Studies and analyses on major ions and nutrients showed that the water quality between the inflow and outflow was different. It was found that Na⁺ loading was increased in the pond while other cation items were in decreased amounts. Moreover, except NO₃^-, the anions loading were found in increased amounts. About nitrogen, the rate for which the amount of sediment release to the total amount of inflow loads accounts was about 10%. About phosphorus, the rate for which the amount of sediment release to the total amount of inflow loads accounts was about 5% which was lower than the same for nitrogen. In the study it was observed that suspended solid (SS) was removed in the pond.However, the organic matter in the pond did not show any change in the amount. The reason might be considered as the influence of increased phytoplankton inside the pond.

View full abstract

With respect to comprehensive water management, including cyclic-use water resources and disaster prevention, it is important to evaluate the storage capacity of various basins. In this paper, simple methods based upon daily rainfall, discharge and evapotranspiration data are used to evaluate two types of storage depth: water use storage depth (WUSD) and total storage depth (TSD). The WUSD addresses the contribution associated with the moderation of the droughty flow, and the TSD addresses the contribution to conversion from a rainfall time series to a discharge time series. Using two forest basins and one reclaimed farmland basin in a snow area as case studies, this study compares storage depths. The results demonstrate that the forest basins provide, on average, more effective neutralization of the rainfall discharge, although both the WUSD and the TSD in any basin vary widely depending on the climate conditions in any given year, and that the snow cover has a significant effect especially on the TSD. Lastly, the extension of the method used here for evaluation of the storage depths is also introduced.

View full abstract

Perfect water application uniformity is a key concern in design and operation of an irrigation system. In this paper, theoretical aspects and experimental validity are presented for ensuring uniform discharge throughout a sprinkler irrigation system. The purpose of this study is to develop a low-cost and easy method to design sprinkler irrigation system in which all sprinklers have the same discharge. An experiment is carried out for different size of orifices by setting them inside of 25-mm diameter pipes and a relationship is found between the orifice diameters and coefficients. Based on the determined relationship, the orifice diameters for simulated risers and the operating pressure head of a sprinkler irrigation system are designed. Different pressure head losses occur at the risers due to the different diameter orifices inside the risers and consequently, a uniform pressure head, which ensures uniform discharges, remains at all the sprinklers. Thus, it is found that the sprinkler flow variation caused by water pressure variation in a sprinkler irrigation system can be controlled by designing proper size of orifices and setting them inside the risers. In addition to designing a sprinkler system for a uniform discharge, the sensitivity that relates the changes of discharges due to an alteration of system operating pressure head at various levels, is analyzed. Further, a proper operating pressure head can be selected for an allowable range of discharge variation.

View full abstract

Standard consolidation tests were carried out to investigate the characteristics of the coefficient of secondary consolidation using pure clay minerals, a remolded clay soil, and undisturbed Ariake clays. The coefficient of secondary consolidation was almost constant for kaolinite, serisite and a halloysite soil over a given range of consolidation pressure, while the coefficient of secondary consolidation versus consolidation pressure relations showed upward convex curves for bentonite and Ariake clay. The secondary consolidation characteristics of remolded clay samples were different according to the type of clay mineral of the samples. With increasing the consolidation pressure, the coefficient of secondary consolidation increased up to a maximum at around a consolidation yield stress for the undisturbed Ariake clays and then decreased. The ratio of the coefficient of secondary consolidation to compression index was almost constant for the undisturbed Ariake clays, with 0.029 to 0.049 in a 95% confidence interval, at the consolidation pressures above the consolidation yield stress, which was within a range proposed by Ladd et al.

View full abstract