Unformatted text preview: Karst
Karst features include sinkholes, caves, springs, sinking streams, cavities, dissolutionenlarged joints and/or bedding planes, and cutter-pinnacle zones, not all of which may be present or obvious. http://www.technosinc.com/geomethods.html Karst
The proper characterization of karst conditions is of vital importance for groundwater flow and structural stability models of a site. Its complexity and variation from site to site pose a significant challenge to site characterization efforts
The United States is stepping up a hightech effort to combat the labyrinth of tunnels built by Mexican drug cartels that could someday become conduits for terrorists. "The threat posed by tunneling is a serious and growing concern for United States' national security," according to the Homeland Security Department's Science and Technology directorate, in a request to businesses that asks for development of a tunnel detection project.
Mimi Hall 2007 Tunnels
As those efforts, combined with the hiring of thousands more Border Patrol agents, have discouraged land crossings, smugglers increasingly are going underground, building deeper tunnels that are difficult to detect. Mimi Hall 2007 Gravity
Applications Identify karst features (caves, voids, sinkholes, weathered zones) Map topofrock Map erosional features (buried channels) Characterize stratigraphic thickness and structure Identify manmade structures (tunnels and mines) Gravity
Advantages Provides a means to characterize conditions in geologic and cultural environments, where other geophysical methods may fail Data can be interpreted to provide estimates of depth, size, and the nature of the anomaly Requires a single operator Can be used inside buildings and structures http://www.technosinc.com/geomethods.html Gravity
Limitations A large number of corrections (latitudinal, elevational, topographical, tidal and drift) have to be applied to the data before they can be modeled Local sources of vibrations, wind, storms, and distant earthquakes can produce interference Gravity surveys can only provide location of void space and depth estimations but little if any information about the structure of the void.
(et al Gibson 2004) http://www.technosinc.com/geomethods.html Resistivity Applications determine the depth and thickness of geologic strata, detect lateral changes and locate anomalous geologic conditions, azimuthal measurements to determine fracture orientation and create a detailed 3D resistivity model http://www.technosinc.com/geomethods.html Resistivity
Advantages Depth range of up to 200 feet Various electrode configurations are available for different applications Such as void detection
Limitations Length of electrode array is typically 5 times the depth of exploration. Finding sufficient accessible space can sometimes be a problem. Susceptible to interference from nearby grounded metal fences, buried pipes, cables, etc. Dry, highly resistive surface materials will limit the amount of electrical current injected in the ground and will reduce the signal to noise ratio
Applications include identify natural and manmade ferrous objects, map geologic structure and stratigraphy, and map karstic features within magnetic soils and rock (et al technosinc). http://www.technosinc.com/geomethods.html Magnetics
Advantages Measurements are relatively easy to make Does not require intrusive ground contact Carried by hand or vehiclemounted http://www.technosinc.com/geomethods.html Magnetics
Limitations Susceptible to interference from steel pipes, fences, vehicles and buildings Total field measurements susceptible to natural fluctuations in Earth's magnetic field (a base station must be used to remove natural fluctuations in Earth's field) http://www.technosinc.com/geomethods.html Gibson, P.J., Lyle, P., George, D.M.,August 2004. Application of resistivity and magnetometry geophysical techniques for near-surface investigations in karstic terranes in Ireland. Journal of Cave and Karst Studies, v. 66; no. 2; p. 35-38. http://www.technos-inc.com/geomethods.html Mimi Hall, Title: U.S. taking aim at border tunnels, USA Today, 07347456, MAR 08, 2007Database: Academic Search Complete ...
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- Fall '07
- Magnetic Field, Void, Karst topography, Sinkhole, Mimi Hall