The following posters represented the geosciences at CUR’s Posters on the Hill, April 24, 2013.
STUDENT: Neerja Zambare
INSTITUTION: Montana State University -Bozeman
FACULTY ADVISOR: Robin Gerlach
POSTER TITLE: Biofilm Induced Biomineralization in a Radial Flow Reactor
SPONSORING AGENCY: Department of Energy – NETL and NSF Collaboration in Mathematical Geosciences
ABSTRACT: Microbially induced carbonate precipitation (MICP) occurs when bacteria create conditions favorable to formation of minerals, such as calcium carbonate also loosely referred to as ‘biocement’. MICP has been proposed for soil stabilization (in dikes, building foundations and road construction), bioremediation (immobilization of contaminants) and well-remediation. We are studying this process in the context of geologic carbon storage and sequestration where MICP can be used to remediate potential leakage pathways around improperly abandoned wells. Subsurface environments can almost always be accessed only via injection wells but our understanding of radial flow systems is limited. We use a Radial Flow Reactor (RFR) to represent the type of flow encountered around pumping or injection wells. Fluid flows into the RFR through a centered influent port and its flow radially outward can be observed visually through a transparent plate. In the RFR experiments, biocement formation is catalyzed by the bacterium Sporosarcina pasteurii, which hydrolyzes urea, increases the alkalinity in its vicinity and precipitates calcium carbonate. The mineral adheres to the glass beads, cementing them together and plugging pore space, thus influencing radial flow patterns. Dye tracer studies and imaging techniques together with chemical analyses are used to study reactive transport patterns. This research will contribute to our understanding of transport and reaction mechanisms in a radial flow setting, which will be very useful in predicting and ultimately controlling the extent of precipitation on a larger scale such as in carbon capture and sequestration projects.
STUDENT: Alberto N. Morgante
INSTITUTION: Manhattan College
FACULTY ADVISOR: Anirban De
POSTER TITLE: Centrifuge and Numerical Modeling of Surface Blast Effects on Underground Tunnels
SPONSORING AGENCY: National Science Foundation
ABSTRACT: Explosions on the ground surface, due to terrorist activities or accidents, may pose significant threat towards any substructures, such as a tunnel or a pipeline. These blasts can cause considerable damage and it is critical to understand the relationships between the damage to the structure and the size of the blast. Factors, such as the depth of the structure and the nature of the soil, will affect the level of damage. In order to study these effects, both centrifuge models and numerical models are used. Centrifuge modeling utilizes physical models at a reduced scale, subjected to high gravitational forces. The higher gravitational forces make it possible to use small amounts of explosives that achieve the same effects as a full-scale model. In addition to the centrifuge models, numerical computer models are used to simulate the effects of explosion, from which damage to the structure is evaluated. Four different centrifuge tests were performed using pipes representing the underground structure. Each model had a different protective cover, made of either concrete or polyurethane foam and instrumented with strain gages. The models were buried at different depths, while the surrounding soil and amount of explosive remained constant. The main objective was to measure the strains on the pipe and the crater depths. Important conclusions are then made from comparisons between different protective covers and depths below ground surface. These tests provide reliable methods for the design and construction of subway tunnels and large pipes that will keep them safe from surface explosions.
STUDENT: Jocelyn Levis | Jamie Moran
INSTITUTION: Allegheny College
FACULTY ADVISOR: Rachel O ‘Brien
POSTER TITLE: Uncovering the Hidden Landscape: Mapping Bedrock Elevation for the Glaciated Region of Northwestern Pennsylvania
ABSTRACT: In an energy-driven world, oil and gas are critically important resources. The Marcellus and Utica shales in the eastern US serve as unconventional, productive sources for natural gas; drilling has already begun to tap into these resources. However, to prevent ground water contamination in shallow aquifers, Pennsylvania law requires oil and gas wells must be cased through any unconsolidated sediments overlying bedrock and the deepest freshwater zone. But in northwestern Pennsylvania there are no maps of depth to bedrock or the deepest groundwater zone. We accumulated approximately 6,600 oil, gas, and water well records for a 2,688 km2 region of northwestern PA covered by Quaternary glacial sediments. The records were located using a geographic information system (GIS) and analyzed for lithologic data (rock type) and well construction details. We plotted the information from these wells, contoured the bedrock surface elevation at the 1:24,000 scale, and digitized our map. The results of this project illustrate the depth to bedrock throughout the region, including the depth, width, and shape of buried bedrock stream valleys. Inaddition to practical applications for oil and gas drilling and protection of water supplies, our results will allow us to re-interpret the pre-glacial landscape in the region. The data suggest that some pre-glacial streams flowed to the south, not north to the St. Lawrence River, as previously believed.
STUDENT: Elizabeth Anne Godfrey
INSTITUTION: Virginia Polytechnic and State University
FACULTY ADVISOR: Celal Guney Olgun
POSTER TITLE: Site Amplification in the Washington, DC Area During the 2011 Virginia Earthquake
SPONSORING AGENCY: National Science Foundation
ABSTRACT: The 2011 Virginia Earthquake occurred on August 23, 2011 in the Piedmont region of central Virginia. The epicenter of this M5.8 event was near Mineral, VA, about 132 km southwest of Washington, DC. One of the only ground surface motion recordings near Washington, DC was at Reston Fire Station, about 122 km from the earthquake epicenter, with a recorded peak ground acceleration of 0.09g. Using site response analysis software, the deconvoluted recorded motion was applied to the base of the recently measured Washington Monument soil profile. The resulting response and surface shaking levels at the Washington Monument were compared with specified building code seismic hazard design values. Seismic hazard design procedures are largely based on empirical data from tectonically active areas, such as the Western US. However, the geological conditions typical of Central and Eastern US (CEUS), which are not considered by building code assumptions, potentially amplify earthquake motions at higher levels than current design assumptions. This phenomenon occurs due to major contrasts in CEUS geology compared to that of the Western US, where rock is more fractured from frequent earthquakes. The findings of this study exemplify unexpected amplification during the 2011 Virginia Earthquake and point to a need for reexamining current seismic hazard design procedures. Greater attention should be given to the surprisingly high vulnerability of Washington, DC to earthquake damage, especially considering the dense population and national importance. This study presents the findings of site response analyses performed at the Washington Monument modeling the 2011 Virginia Earthquake.