We have successfully measured in-situ stresses in gold, copper, platinum, molybdenum, trona, oil shale, limestone, and coal mines and in tunnels, concrete dams, and other civil structures since 1978.  In our history, we have completed more than 1,000 overcore stress measurements.
We conduct three well-established types of in-situ stress measurements based on the overcoring method:

• U.S. Bureau of Mines (USBM) borehole deformation gauge (BDG) for 2D-stress measurements
• Sigra IST In-Situ Stress Measurement Tool for 2D-stress measurements
• CSIRO Hollow Inclusion Cell (HI Cell) for 3D-stress measurements

Our core drilling rigs (Ingetrol Explorer 75E, Boyle Super 300, SD-1500, LA-100, and CP-65) are ideal for overcoring up to 80 feet (25 meters) deep with the USBM BDG and HI Cell methods.  USBM BDG and HI Cell overcoring is well suited for determining stresses in mines, tunnels, and concrete dams.  As a general guideline, the in-situ stress state can be obtained by overcoring at a distance greater than 2.5 times the diameter of the opening.

USBM BDG two-dimensional stress determinations are conducted per ASTM D4623-08.

The HI Cell can be used to measure the full three-dimensional in-situ stress state, or as a long-term monitor of stress changes when set permanently in place.  Manufacture details about the HI Cell can be found on the ESS Earth Sciences HI Cell webpage and ESS Stress Measurements in Dams webpage.

Our smaller drill rigs are portable for difficult access locations and are permissible for use in “gassy” mines.  The rigs can be set up on tracks or skids and powered with diesel engine, electric motor, or pneumatic-hydraulic powerpacks.  Drilling can be completed from any angle ranging from holes vertical up to vertical down.

The Sigra IST method is designed for measuring two-dimensional stress in vertical down holes to depths of 5,000 feet (1,500 meters), in conjunction with normal HQ wireline coring operations using Boart Longyear HQ wireline drill string equipment.  Click here for more information: Sigra IST In-Situ Stress Measurement Tool.

Please see our dam stress measurement project summaries below.