GPR Ground Scanning for Sinkhole and Subsurface Void Investigation
Sinkholes, underground voids, washouts, and soil loss can create serious concerns for buildings, parking areas, roadways, landscaped areas, and other developed sites. In many cases, the problem begins below the surface and may not be clearly visible until settlement or collapse occurs.
Ground Penetrating Radar (GPR) ground scanning is a non-destructive geophysical method that can help identify subsurface anomalies associated with voids, disturbed soil, washout, buried features, or changes in underground conditions.
How GPR Helps Investigate Potential Sinkholes
GPR transmits electromagnetic signals into the ground and records reflections created by changes in subsurface materials. Areas with different soil conditions, void spaces, buried objects, or disturbed ground may produce radar responses that differ from the surrounding material.
A GPR survey can therefore help identify areas requiring further investigation when there are concerns about:
- Potential sinkholes;
- Underground voids;
- Soil washout;
- Ground settlement;
- Loss of support beneath pavement or slabs;
- Disturbed or previously excavated ground;
- Buried structures or abandoned features; and
- Other unusual subsurface conditions.
GPR is especially useful because the survey can be completed from the surface without immediately excavating or disturbing the site.
Common Signs That May Require GPR Ground Scanning
A subsurface investigation may be appropriate when site personnel observe:
- Localized ground depressions;
- Sudden settlement;
- Cracking or settlement of pavement;
- Depressions near catch basins or manholes;
- Recurring repairs in the same location;
- Uneven ground surfaces;
- Suspected washout near underground drainage systems;
- Soft or unstable areas; or
- Unexplained changes in site grading.
These conditions do not necessarily confirm a sinkhole. However, they may indicate that additional subsurface assessment is warranted.
What Can GPR Detect?
Depending on soil conditions, moisture content, target size, and investigation depth, GPR may identify radar anomalies associated with:
- Air-filled or partially filled voids;
- Loose or disturbed soil;
- Changes between soil layers;
- Buried concrete or structural features;
- Former excavations or trenches;
- Subsurface erosion;
- Washout zones; and
- Other areas that differ from surrounding ground conditions.
GPR does not directly prove that a sinkhole exists. Instead, it identifies subsurface anomalies that can be evaluated together with site conditions and other investigation methods.
GPR for Sinkhole Investigation
Where a sinkhole or underground void is suspected, KR Engineering can conduct systematic GPR scanning across the affected area and surrounding ground.
The investigation may include:
- Review of visible settlement and site conditions;
- GPR scanning across the suspected area;
- Comparison of radar responses with surrounding ground;
- Identification of significant subsurface anomalies;
- Mapping of areas requiring additional investigation; and
- Engineering recommendations for further assessment, monitoring, or repair where appropriate.
Depending on the findings, additional verification may include boreholes, test pits, CCTV inspection of underground pipes, geotechnical investigation, or other targeted methods.
Advantages of GPR Ground Scanning
GPR offers several benefits for subsurface investigations:
Non-Destructive: The ground can be assessed without immediately excavating the site.
Rapid Coverage: Relatively large areas can be scanned efficiently.
Real-Time Assessment: Radar data can be reviewed during the field investigation.
Targeted Follow-Up: GPR can help identify locations where further investigation should be concentrated.
Reduced Unnecessary Excavation: Instead of excavating a large area, GPR may help narrow down the zones that require verification.
Limitations of GPR
GPR performance depends heavily on site conditions. Signal penetration may be reduced by:
- Clay-rich soils;
- High soil moisture;
- Conductive materials;
- Dense subsurface fill;
- Reinforcement or buried metal;
- Target depth; and
- Small or irregularly shaped features.
For this reason, GPR results should be interpreted together with visual observations, site history, drainage conditions, and geotechnical or structural information.
A radar anomaly should not automatically be classified as a sinkhole without appropriate engineering evaluation.
GPR Ground Scanning Services in Edmonton and Alberta
KR Engineering Inc. provides GPR ground scanning services for sinkhole, void, washout, settlement, and subsurface anomaly investigations in Edmonton and throughout Alberta.
Our GPR investigations can support assessments of:
- Suspected sinkholes;
- Ground settlement;
- Pavement depressions;
- Underground voids;
- Soil washout;
- Drainage-related ground loss;
- Areas around manholes and catch basins; and
- Other unexplained subsurface conditions.
Where required, GPR findings can be combined with geotechnical investigation, CCTV inspection, drilling, test pits, or engineering assessment to better understand the cause and extent of the problem.
Concerned about a sinkhole, ground settlement, or possible underground void?
KR Engineering Inc. can provide GPR ground scanning to help identify subsurface anomalies and determine where further investigation may be required.
