Study on the relation of river morphology and tsunami propagation in rivers

The relations of river morphology and tsunami propagation in rivers were studied at several rivers in the Tohoku region during The Great Chilean Tsunami of 2010 and The Great East Japan Tsunami of 2011. It was found that river mouth morphological features play an important role in the intrusion of low magnitude tsunamis in which the geological and geographical conditions are an important factor. Nevertheless, the effects of these features were not found in the case of an extreme tsunami wave. As the wave enters the river, the propagation depends on other factors. It was found that the intrusion distance correlates well to the riverbed slope. The measurements of water level and riverbed slope were analyzed to propose an empirical method for estimating the damping coefficient for the tsunami propagation in rivers based on the tsunami of 2011. The proposed empirical method was used to approximate the length of the tsunami intrusion into a river by assuming that the furthest distance is given for the ratio of local tsunami wave height to the tsunami wave height at the river entrance of 0.05 (5 %). The estimated intrusion length from the proposed method in this study shows a good comparison with measurement data.     

Characterization of corrosion products in the permeable reactive barriers

 The impact of geochemical processes and microbial activity has been a major concern for the long-term performance of reactive iron barriers because corrosion products and precipitates during the water treatment with reactive materials will decrease the reactivity and permeability of the iron bed. This study characterizes corrosion products in reactive iron barrier as well as evaluates the effect of the iron corrosion products and precipitates on iron wall performance during contaminated-water treatment under varying conditions. Major phases in the reactive iron barrier include iron oxides, carbonates, iron sulfides, and elemental sulfur, depending on the degree of iron oxidation, groundwater chemistry, and microbial activity. Detailed geochemical and mineralogical characteristics are imperative for long-range predictions of the reactive iron wall performance on water treatment because the surface coating materials reduce the effectiveness of the zero-valent iron media. Received: 17 September 1999 · Accepted: 11 April 2000     

Modeling and cyclic behavior of segmental bridge column connected with shape memory alloy bars

This paper examines the quasi-static cyclic behavior,lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy(SMA) link-bars.Moment-curvature constitutive relationships are formulated and analysis tools are developed for the PT column,including a modified four-spring model prepared for the SMA bars.The suggested system is exemplified using a column with an aspect ratio of 7.5 and twelve 36.5 mm diameter NiTi martensitic SMA bars.A post-tensioning force of 40% to 60% of the tendon yield strength is applied in order to obtain a self re-centering system,considering the residual stress of the martensitic SMA bars.The cyclic response results show that the lateral strength remains consistently around 10% of the total vertical load and the equivalent viscous damping ratios reach 10%-12% of critical.When large diameter NiTi superelastic SMA bars are incorporated into the column system,the cyclic response varies substantially.The creep behavior of the superelastic SMA bar is accounted for since it affects the re-centering capability of the column.Two examples are presented to emphasize the modeling sensitivities for these special bars and quantify their cyclic behavior effects within the column assembly.     

Mineralogical characterization of saprolite at the FRC background site in Oak Ridge,Tennessee

The Field Research Center (FRC) including five contaminated sites and a clean background area was established in Oak Ridge, Tennessee, as a part of the U.S. Department of Energy’s Natural and Accelerated Bioremediation Research (NABIR) program. This study investigates the mineralogy and mineralogical pathways of saprolite at the FRC background site to provide a fundamental basis for the remediation strategy for contaminated sites. The background site is underlain interbedded shales, siltstones, and limestones with nearly identical characteristics to the contaminated sites. Bulk samples of saprolite were collected by hand picking approximately at 1 m depth (C horizon) from the soil surface. The soil pH of 4.3 and cation exchange capacity (CEC) of 10.5 cmol/kg measured are in the range of the typical shallow depth saprolite layer in this area. Total Fe by citrate-bicarbonate-dithionate (CBD) and ammonium oxalate extractable (amorphous) were 17.6 and 0.61 g/kg, respectively. Total Mn extracted by NH₂OH·HCl was 0.17 g/kg. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicate that quartz, illite, and microcline (K-feldspar) are the dominant minerals, occupying 95% of mineral composition. The saprolite samples analyzed have shown characteristics of oxic conditions overall, and the degrees of weathering for three sampling locations were various, most for S1 and least for S3, likely influenced either by the flow channels developed through saprolite or by seasonal fluctuation of the groundwater table. The source of the manganese oxide that observed from the site is likely to be Mn-rich muscovite in the shale or Mn-rich biotite in the blackish band in the limestone. The results such as abundant Mn and Fe contents identified encouraging prospects for conducting remediation projects in FRC sites.     

Modelling chronic winter hazards as a function of precipitation and temperature

In previous research, winter weather conditions like precipitation and cold were recognized as factors affecting the change in traffic volume, and a simulation has been conducted to model the effect of weather factor on variations in traffic flow. A winter weather hazard model considering natural chronic hazards in the winter season has been proposed. To achieve this purpose, this research formulated a dummy variable winter weather traffic model while considering explanatory variables such as expected daily volume, snowfall, and temperature. This model was derived using six-year traffic data that were collected on a weigh-in-motion site on Highway 44, in Alberta, Canada. Precipitation and cold data collected from a weather station were linked with traffic data to model traffic variations caused by weather factors. The performance of the model, on the ground of temporal transferability and model specification, was tested using data from different years. The temporal transferability test confirmed that the model can be successfully applied regardless of the year. It was also revealed that each vehicle class prefers a different model specification in estimating correct traffic volume.