Detection, stabilization, and remediation of sinkhole features in karst terrians are one of the significant problems facing geo-profession als in general and in the state of Florida in particular. Sudden or gradual sinkhole development can be catastrophic to overlaying structures. Hydrogeologic interpretation can be difficult where covered or relic sinkholes intercept multiple aquifers. Soil boring programs often provide insufficient data to properly evaluate sinkhole potential of a property. Properly selected and applied geophysical technology offers a means to help locate sinkhole features.

• site reconnaissance, review of aerial photographs and available geologic maps supplemented by stratigraphy characterization conclusive to snkhole development,
• determination depth and character of rock surface,
• location voids and caviites,
• search for facture zones and lineaments are key elements of sinkhole related investigation.

To effectively address this problem and assist in its remediation is a challenge.  An assessment of the state-of-practice in sinkhole detection by utilizing effective geotechnical and geophysical techniquies is, therefore, required.

Paving

Backfilling

ASC's areas of expertise include:

• Sinkhole Damage Claims Investigations
• Sinkhole(s) Linament Determination
• Verification of Sinkhole Activity
• SPT Borings (SPT) and/or PCPT (Piezocone) Soundings
• Geophysical Surveys (GPR, ER, MER, Seismic Reflection/Refraction) to enhance the decision making process
• Test Pits, Manual Auger Borings and Cone Probes
• Inspection and Pre-Condition Survey including Floor Elevation Survey
• Grouting Methods (Compaction, Chemical, and Pressure)
• Remediation Procedures including monitoring
• Post Grouting Testing and Acceptance Letter
• Expert Witness Services and Litigation Proceedings Support

Piering Remediation

Developed Site

Sinkholes are the most serious geologic hazard in karst terrain because they can damage structures, drain ponds and lakes, and allow direct infiltration of groundwater contamination.   The potential hazard of sinkholes is most difficult to assess in mantled-karst area where the soluble bedrock is overlain by thick deposits of unconsolidated siliciclastic sediment that obscure the potential for subsurface erosion which causes sinkholes.  Site-specific evaluations of sinkhole conditions depend on the accurate characterization of irregular buried bedrock topography, soil or sediment stratigraphy,  soil mechanical properties, and subsurface drainage releationships.  Subsurface conditions can be documented by use of standard penetration test borings and electric piezocone soundings both inside and outside of the affected area, ground penetrating radar to show lateral continuity of subsurface horizons, and piezometers to establish direction and velocity of groundwater flow.  The investigation should be designed to produce a two- or three-dimensional “picture” of the subsurface.  Correct interpretation of the data depends upon the evaluator having a thorough understanding of karst processes.  The risk of sinkhole development can be estimated quantitatively by analyzing the historical frequency of new sinkhole development per unit area per unit time, for areas of comparable hydrogeologic conditions.  However, changes in the hydologic balance caused by nature or man’s activities may induce sinkholes where non previously occurred.

Results of geophysical methods demonstrate their value to augment borehole data in economical investigations of sinkhole potential in karstic terrains.

GEOPHYSICAL EXPLORATION - Uses the most suitable geophysical method for a specific site.  Unlike many other consultants who use GPR (with large frequency antennas) in all site subsoil conditions.  GPR cannot penetrate clays and peat layers and has a limited depth capability to 30 feet for sandy soils and can indicate raveling conditions only.  An advance knowledge of subsurface conditions and associated sinkhole related potential allows for the design of remediation and monitoring programs that are more effective, as a result, more cost-effective.

STRUCTURAL REMEDIATION (grouting and/or underpinning) PROCEDURE - Has an in-house structural engineer (with over 37 years experience) to prepare remediation plans and specifications and provide coordination with specialty remediation subcontractors, and understanding of project requirements.

REMEDIATION MONITORING - Has experienced, large, available staff of trained inspectors with equipment to monitor and inspect remediation methods.

A properly planned and effectively implemented field exploration program consisting of geotechnical SPT borings and/or piezocone soundings, supplemented by a site specific geophysical survey, is a pre-requisite for sinkhole related claims.

PROVIDES TOTAL SERVICES - Investigation and geotechnical/geophysical exploration, remediation procedure(s) and plan(s) preparation, remediation monitoring, post grouting investigation, and issuance of a completion letter for insurance continuation.

GEOTECHNICAL EXPLORATION - 3 drill and/or a Piezocone Penetration rigs with experienced drillers knowledgeable of sinkhole effected soils backed up by experienced geotechnical operators/engineers who have performed geotechnical services on many projects where sinkhole related claims have been alleged.

TEST PITS, HAND AUGER BORINGS AND MANUAL CONE PROBES - Experienced field engineering personnel perform test pits to expose and obtain data about foundation types and sizes.  In addition, cone probes are made to obtain information about shallow sub-soils in difficult access areas.