Sazzad Bin-Shafique

Person-place-time analysis of vehicle fatalities caused by flash floods in Texas

A significant number of crashes on roads are caused by adverse weather conditions. Among the most serious consequences of rainfall and flooding in regard to road safety are the motor vehicle-related flash flood fatalities. These fatalities are of particular concern in Texas. Information on motor vehicle fatalities caused by flash floods was extracted from the National Climatic Data Center Storm Data reports. Review of reports on flash flood fatalities in general, where the death circumstances are provided, reveals that most fatalities are motor vehicle-related (80%). Moreover, data from the reports indicate that from 1959 to 2009 the number of motor vehicle-related flash flood fatalities in Texas exceeds by far the total number of flood fatalities in any other state. Demographic analysis of the flash flood fatalities indicates that, in Texas, all ages are at risk and that males are much more affected than females. Spatial analysis indicates that the highest numbers of fatalities occur in counties having major urban areas. The increase in the frequency and intensity of storms and floods that is projected to result from climate changes and variability, and the rapid urbanization in the region may considerably increase the impacts of weather on road safety in Texas.

Motor Vehicle-Related Flood Fatalities in Texas, 1959–2008

The number of related fatalities is one of the most essential socioeconomic characteristics of a natural disaster as death is the most serious and irreversible consequence of a disaster. Texas leads the nation in flash flood fatalities. From 1959 through 2008 the flood fatalities in Texas (839) were more than three times the fatalities in the next leading state, Pennsylvania (265). Flood fatalities in Texas represent a serious public health problem. Flood fatality statistics were extracted from National Climatic Data Center Storm Data publications. Review of the flood fatalities, where the death circumstances are provided, reveals that most fatalities are motor vehicle related (77%). Data analysis indicates that, in Texas, males are much more likely to be the victims of motor vehicle–related flood accidents than are females. Most motor vehicle–related fatalities happened at night (56%). Most fatalities resulted from flash floods. Spatial analysis indicates that the highest numbers of fatalities occur in counties having major urban areas. Flood fatalities in Texas can be reduced through a combination of improved hydrometeorological forecasting, educational programs aimed at enhancing the public awareness of flood risk and the seriousness of flood warnings, and timely and appropriate action by local emergency and safety authorities.

Soil-Strength Enhancements from Polymer-Infused Roots

AbstractThis research investigates the use of polymer-infused roots for soil-improvement applications. By infusing polymer through the easily accessible above-surface plant stems, polymer-infused roots can be created without subsurface excavations. Evaluation of this technique involves identifying the improvements from polymer-infused roots by measuring in situ shear strength of soil using a vane shear apparatus and by measuring the tensile strength using split-tension tests in the laboratory. Roots of Ruellia squarrosa and Artemisia annua plants were infused with a mixture of epoxy resin and polyoxyalkylamine blend hardener. Compared with noninfused roots, polymer-infused roots provided an additional 22 kPa (28%) of shear strength for elastic silt and an additional 13.1 kPa (25%) of shear strength for low-plasticity clay with a corresponding 13.6-kPa (55%) increase in tensile strength for the low-plasticity clay. Acid hydrolysis testing was performed to ascertain the potential durability of the polymer-i...

Tieback Retaining Wall in High Plasticity Expansive Soil

AbstractThis study evaluated the impact of moisture-induced swelling pressure on a tieback wall constructed in high plasticity expansive soil. The study was based on laboratory soil characterization, field monitored seasonal fluctuation of moisture content, and numerical simulation. Soil samples were retrieved from a construction site at the intersection of I-35 and Walters Street in San Antonio, Texas, and two boreholes were installed to monitor the moisture profile at the site. Considering the field setting, a numerical model was developed to simulate the construction and performance of a tieback wall subjected to significant lateral earth pressure due to swelling. The model further assessed the impacts of different factors on the behavior of the tieback wall, such as moisture profile, surcharge, unbonded length of the soil anchor, and wall rigidity. The study indicated that more drastic changes in soil suction profiles between construction and in-service conditions may generate lateral stresses that re...

Numerical Simulation of a Drilled Shaft in an MSE Wall under Cyclic Loading

A numerical simulation was conducted using FLAC3D to investigate the interaction between the drilled shaft and the MSE wall under lateral cyclic loading that are often encountered from bridges, traffic signs, and sound walls. The drilled shaft was built within the reinforced zone of an MSE wall and loaded toward the MSE wall under force-control mode. An elastoplastic constitutive model, able to consider shear and compression hardening, was selected for the backfill material. The MSE wall facing was simulated by discrete blocks which interacted with each other by friction. The selected constitutive model was calibrated by triaxial test data. Thereafter, the numerical modeling was conducted to simulate a published full-scale field study on the interaction between the drilled shaft and the MSE wall. It was found the developed numerical model can well represent the loading-unloading behavior of the drilled shaft and the MSE wall. As the drilled shaft was laterally loaded to a large deflection, only small percentage of the deflection could recover when the load was removed. As to the MSE wall, nearly all the deformations induced were not recoverable. It was suggested the numerical model be further improved by accounting for the separation between the MSE wall facing blocks.

Performance of Soil Nail Wall in High Plasticity Expansive Soil

The swelling pressure induced lateral stress and deformation in soil, the maximum nail load, and the nail head load of a soil nail wall constructed in high plasticity expansive soil are determined using finite element model. Soil samples were collected from the construction site and were subjected to various laboratory testing to measure the soil parameters related to volume change due to change in soil suction and to establish the soil water characteristic curve for the soil. The moisture content profile of the construction site was monitored for two years and a wetting envelope was developed to represent the maximum change in moisture content due to seasonal fluctuation. A finite element model is developed to simulate the soil nail wall in high plasticity expansive soil, which shows that the lateral stress and deformation in soil, the maximum nail load, and the nail head load of a soil nail wall increases significantly due to seasonal fluctuation of the moisture content.

Effect of Direct Droppings from Bridge Nesting Birds on Bacterial Concentration of Underneath Surface Water

Concentrations of indicator bacteria, such as E. Coli, fecal coliform, and Enterococci were measured from upstream, underneath, and downstream of a bridge over the Guadalupe River near Kerrville, TX, to evaluate the effect of direct droppings of birds residing under the bridge structures on the bacterial loading in the underneath water. The bacterial loadings in all sampling locations increased as soon as the migratory birds started nesting on the bridge. The concentrations of bacteria in water beneath the bridge were significantly higher than those in upstream water. The concentrations of bacteria in downstream water were slightly higher than those in upstream water and significantly lower than those in water underneath the bridge due to dilution and decay. The probability analysis of the concentration of bacteria in water underneath the bridge showed that the concentrations of E. Coli, fecal coliform, and Enterococci are likely to remain within the Texas Commission on Environmental Quality specified contact recreation limit for 71, 68, and 35 percent of the time, respectively, during the nesting season.