An improved numerical model for the accurate prediction of the fault rupture mechanism through the overlying soil gives confidence to the engineers in sitting the structures near or above faults. In this work, a sophisticated numerical model incorporating a hardening-softening constitutive model with shear band effect is calibrated from the direct shear model test results and validated for the prediction of the behavior of medium dense Fontainebleau sand bed due to quasi-static normal movement of the bed rock of fault with dip angle equals to 60°. The numerical results show satisfactory agreement with the experimental data from centrifuge (115g) and 1g model tests in terms of normalized vertical displacements profile of the ground surface, minimum relative vertical base displacement for the rupture to reach the ground, the average dip angle propagated into the soil as well as the horizontal extent of the deformed surface ground. The effect of the very low stress fields in the 1g tests (scale effect) is discussed.
Due to the growing concern for natural environment conservation in Japan, agricultural channels have recently been required to provide structures for an aquatic habitat. Following such request, an irrigation channel running in To-on, Ehime, was reconstructed for aiming to create the aquatic habitat by widening a part of the channel. This paper deals with the flow and material transport in the channel with a side-cavity, by means of field observation and numerical experiment. The field observation revealed a clock-wise eddy in the cavity. The average velocity in the cavity was less than 10 cm/s and flow in the cavity was always calm, not so depend on the discharge in the channel. To simulate the flow and then investigate the material transport in the channel, a horizontally 2-D shallow water flow model combined with quadtree numerical grids was used. The materials were modeled to be transported horizontally with the same speed as water flow. At the same time, however, they settle down following the Stokes law of resistance. The computed result showed that the material having small settling velocity is easy to be transported into inner part of the cavity.
A multiobjective optimization model is developed for controlling TN (Total Nitrogen) load discharged from field plots in an agricultural watershed. In optimization, maximizations of allowable TN discharge per unit area and total yield of rice are intended while complying with an effluent limitation standard prescribed for river water quality management. The discharge from a field plot is separated into two components, i.e., direct runoff and baseflow. As discharged TN from a plot travels with these components toward an outlet of the watershed, the amount of TN is assumed to decrease due to distance-related self-purification occurring in subsurface zone, drainage canal and river. Locations of field plots and traveling routes of TN are identified or predicted by a GIS (Geographic Information System) with a digital elevation model and by field surveys. The model developed is applied to an agricultural watershed bordering with Lake Biwa in Shiga Prefecture, Japan. The result demonstrates that the optimal allocation of maximum allowable discharged TN load among field plots is helpful in prioritizing plots where fertilization should be reduced.