Our Services
 

GeoStructures offers a wide range of professional services in the geotechnical engineering and construction monitoring fields. All of our work is backed by an unwavering commitment to excellence, innovation, and practicality.

 
Concrete Laboratory Testing
Construction Monitoring
Dams Analysis & Rehabilitation
Environmental Assessments
Foundation Investigation & Design
Geotechnical Laboratory Testing
Highway and Bridge Geotechniques
Lime and Cement Stabilization
Mine Subsidence Analysis & Remediation
Pavement Design & Rehabilitation
Percolation/Permeability In-Situ Testing
Pond and Lagoon Liners Design
Research and Special Studies
Sinkhole Evaluation & Remediation
Slope/Retaining Wall Evaluation & Design
Soil Improvement Technologies
Soil-Structure Interaction
Subsurface Investigations

Sinkholes and Karst Regions: Investigation and Remediation

Legends of disappearing streams and underground lakes and rivers are common in karst regions, where sinkholes seem to appear overnight to swallow a building or close a commuter roadway. Sinkholes are a natural consequence of soil loss into underlying bedrock solution openings that have formed over eons of time. Erosion domes are the most dramatic and potentially damaging. These features form in cohesive soils and progress upward like “bubbles” through incremental roof collapse until they reach the ground surface. Roof collapse occurs when the width of an underground opening exceeds the ability of the overlying material to arch across it. This process is similar to that of mine subsidence. With water as the accelerator of roof collapse, it follows that areas of focused infiltration such as recently cleared construction sites, drainage channels, and unlined stormwater basins are especially vulnerable to sinkholes.

 

 
Chemical decomposition of carbonate rocks such as limestone and dolomite is a natural process. Corrosive agents include rainwater made slightly acidic by dissolved carbon dioxide or groundwater containing dissolved hydrogen sulfide gas from the breakdown of organics. Contrary to popular belief, normal fluctuations in pH—natural or artificial—have virtually no effect on this process over the lifespan of a structure even though some building codes reflect this misconception. In humid climates of the eastern United States fracture surface denudation is only 1 to 1-½ in. per 1,000 years. At this rate, it would take at least 100,000 years to form a 12-ft wide slot in the rock and millions of years to create extensive underground caverns!

 

 
Building with confidence in karst demands detailed subsurface investigations to identify incipient sinkholes and characterize a site’s unique hydrogeologic factors. Universal tools of intrusive investigation include borings, percussion probes, and test pits. Recognizing that high angle discontinuities are more vulnerable to large openings, geologic mapping of rock exposures on or near a job site for weathering and fracturing can provide insight into the alignment of underground slots in the bedrock. In the absence of visible outcrops and as a complement to geologic mapping, aerial photo stereo pairs can be obtained for many sites. Such photos are examined for fracture traces—recognizable as lineaments of dark ground caused by deep weathering, increased moisture and dense vegetation. Geophysical tools may also be applied to obtain 2-D profiles of the ground and rock between discrete borings. Effective techniques include microgravity, electromagnetic (EM), DC resistivity, and seismic refraction surveys.

 

 
Building with confidence in karst demands detailed subsurface investigations to identify incipient sinkholes and characterize a site’s unique hydrogeologic factors. Universal tools of intrusive investigation include borings, percussion probes, and test pits. Recognizing that high angle discontinuities are more vulnerable to large openings, geologic mapping of rock exposures on or near a job site for weathering and fracturing can provide insight into the alignment of underground slots in the bedrock. In the absence of visible outcrops and as a complement to geologic mapping, aerial photo stereo pairs can be obtained for many sites. Such photos are examined for fracture traces—recognizable as lineaments of dark ground caused by deep weathering, increased moisture and dense vegetation. Geophysical tools may also be applied to obtain 2-D profiles of the ground and rock between discrete borings. Effective techniques include microgravity, electromagnetic (EM), DC resistivity, and seismic refraction surveys.

 

 
 
 
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