Case Study: Unexpected Karst Void Found During Highway Embankment Construction in Kentucky (2017)
Project Overview
• Name: KY-90 Improvement Project
• Location: Pulaski County, Kentucky
• Year: 2017
• Project Size: $120 million
• Scope: Highway embankment and roadway widening
• Lead Agencies/Contractors: Kentucky Transportation Cabinet /
Category of the Issue, Problem, or Challenge
• Geotechnical
• Differing Site Conditions
Summary of the Issue, Problem, or Challenge
Construction revealed previously unknown karst voids beneath embankment area, requiring extensive ground stabilization and redesign.
Root Cause Analysis
- Initial site investigations missed karst features due to limited geophysical survey.
- Lack of detailed sinkhole and subsurface cavity mapping in project area.
- Design did not anticipate high karst risk, leading to inadequate foundation preparation.
Impacts Due to the Issue, Problem, or Challenge
- Work stopped for 5 months to perform grouting and void filling.
- Project costs increased due to additional ground improvement measures.
- Safety concerns for workers and future roadway users.
Corrective Actions Taken
- Conducted thorough geophysical surveys (electrical resistivity, ground-penetrating radar).
- Applied pressure grouting and compaction grouting to fill voids.
- Modified embankment design to include reinforced foundation layers.
- Implemented karst risk assessment protocols for future projects.
Lessons Learned
- Karst terrains require specialized geophysical investigations pre-construction.
- Designs must include contingencies for subsurface voids in karst areas.
- Early detection prevents costly delays and safety risks.
Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation
- Are karst risk assessments performed early in project planning?
- Have appropriate geophysical surveys been completed?
- Are void mitigation and monitoring plans included?