Detection of underground voids and karst

Underground voids — karst caves, zones washed out by water, old wells, cellars, tunnels and abandoned quarry workings — can cause unexpected subsidence beneath buildings and roads. The widespread limestone layers on the Absheron peninsula, old stone quarries and leaking utilities make this risk especially relevant around Baku.

A void is hard to find by drilling alone, because a borehole can easily miss it by a few metres. Geophysical methods cover the whole site with continuous profiles instead. Electrical resistivity tomography (ERT) shows voids and washouts as resistivity anomalies, GPR images shallow cavities and settlement beneath paving in detail, and seismic methods pick out weakened and fractured zones by their lower wave velocities.

Once anomalies are found, they are accurately positioned with GNSS RTK and recommendations are given for verifying them with targeted boreholes. This keeps drilling to a minimum while improving confidence in the results.

The survey is used on new construction sites, at existing buildings showing cracks or settlement, and on roads and yards where sinkholes have appeared. The results help designers choose appropriate foundation solutions and ground improvement measures.

When you need it

• New construction on limestone or gypsum
• Design on former stone quarry areas
• Investigating causes of cracks and settlement in existing buildings
• Studying sinkholes on roads and yards
• Finding washout zones around leaking utilities

What's included

• Review of geological and historical site data
• Electrical resistivity tomography (ERT) profiles
• GPR survey of shallow zones
• Seismic profiles where required
• GNSS RTK positioning of anomalies
• Recommendations for verification drilling

How we work

1. Studying the problem and the site
2. Selecting methods and profile grid
3. Geophysical fieldwork
4. Integrated interpretation and anomaly mapping
5. Report and recommendations

Deliverables

• Resistivity and radar sections
• Map of probable voids and weak zones
• Coordinate list of anomalies
• Recommendations on verification drilling and foundations
• Technical report