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Continuous Profiling Technology to Detect Subsurface Cavities Before Road/Ground Sinks and Collapse

Description:

Geohazards such as sinkholes and road/ground collapse can occur as near-surface rock and soil can no longer support the ground surface either because an underlying cavity grows or near surface material is lost through underlying cracks or voids. Sinkholes that are life-threatening and may cause significant structural damage to transportation infrastructure are primarily a problem in karst areas where soluble bedrock is predominant. According to the US Geological Survey (USGS), about 20 percent of the nation’s land is susceptible to sinkholes and they are most likely to occur in the states of Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. Sinkholes create at least $300 million in damages each year in the United States (Weary, 2015). Worldwide, metropolitan cities such as Shanghai (China), Tokyo (Japan), Seoul (Korea), and Ottawa (Canada) have experienced massive sinkholes due to underground cavities; creating significant economic loss and traffic congestion, in addition to increased social fear due to news sensationalism. For man-made sinkholes, excessive underground development (e.g. subway, parking lot, quarries, etc.) and aging underground infrastructure (e.g. pipeline leakage) can be the main causes.

In order to prevent and mitigate ground sink and collapse, engineers need improved assessment tools and methods that can detect these underground cavities before they reach the surface and create catastrophic collapse. Current practice includes drilling and sampling conducted at discrete locations often thousands of feet apart with the objective of determining soil properties and subsurface stratigraphy. Some geophysical methods such as Ground Penetrating Radar (GPR) and seismic methods can assess some subsurface conditions. GPR is a powerful tool that continuously profiles underground images along the road and provides 2-D subsurface imaging; however, it has several limitations in that no structural or mechanical properties are provided, the signal cannot penetrate clay layers, and the penetration depth is generally limited to “shallow” depth compared to other geophysical methods. On the other hand, surface wave based methods (e.g. SASW, MASW) can provide shear wave velocity profiles which represent material stiffness but the current testing method is discrete (or stationary), which makes it difficult to cover large areas and requires traffic control on roadways. Likewise, electrical resistivity (ER) has been somewhat successful in detecting subsurface voids, but is also a currently stationary technology. Deflection-based testing methods (e.g. FWD, RWD) have been used to assess road subsurface conditions. FWD is a discrete testing method and not effective for coverage of large areas. Rolling Weight Deflectometer (RWD) provides a deflection profile as it travels at highway speeds; however its low data spatial resolution is not sufficient in detecting underground voids.

All current technologies are to some extent limited for the pre-detection of potential ground sinks along the roadway, particularly in urban areas. Therefore, it is proposed to i) identify state-of-the-art technologies capable of continuously assessing (or profiling) subsurface condition and ii) develop new technology by modifying and/or combining existing testing technologies to maximize its performance in detecting underground cavities that may lead to catastrophic road/ground sinks.

Objective:

The objectives of this research are to identify state-of-the-art technologies to assess subsurface condition and to develop a technology that continuously profiles the roadway subsurface condition, especially for pre-detection of potential road/ground sinks due to underground cavities.

Benefits:

The outcome will be the development of cutting-edge technology for sinkhole pre-detection prior to catastrophic ground collapse so that engineers are able to make repair/reinforcement recommendations before emergencies arise. This technology will also help to identify and delineate problematic areas of subsurface soils, which is an important input to road maintenance and rehabilitation.

Tasks:

1) Literature review of current state-of-the-practice geophysical or non-destructive testing methods.

2) Design and manufacture improved or new technology.

3) Test technology in field conditions.

Implementation:

The outcome will be the new innovative technology. If successful, the developed technology can be widely adopted by state DOTs and FHWA. Industry can also participate in developing and enhancing the technology.

Relevance:

Potential users of these research results are expected to be Departments of Transportation, municipalities and any other infrastructure owners.

Sponsoring Committee:AKG10, Engineering Geology
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Boo Hyun Nam, Ph.D., Associate Professor, University of Central Florida, Department of Civil, Environmental, and Construction Engineering, Orlando, FL 32816, email: boohyun.nam@ucf.edu
Date Posted:02/28/2018
Date Modified:04/20/2018
Index Terms:Soil profiles, Subsoil, Underground structures, Geological surveying, Underground cavities, Sinkholes, Collapse,
Cosponsoring Committees: 
Subjects    
Highways
Geotechnology

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