AAI HAS THE UNIQUE EQUIPMENT AND PERSONNEL FOR CONDUCTING OVERCORING STRESS MEASUREMENTS IN LIMITED ACCESS SURFACE AND UNDERGROUND LOCATIONS.

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.

IST in-Situ Stress Measurement Tool
Sigra IST In-Situ Stress Measurement Tool

USBM and HI Cell Overcoring Stress Determinations Since 1994

Year Client No. of Successful Runs
2016-17 Duke Energy Walters Dam 47
2016 Stillwater East Boulder Mine 4
2014 Graymont Pleasant Gap Mine 13
2013 Dominion Roanoke Rapids Mine 74
2013 Subterra, LLC White Pine Copper Mine 3
2013 SURF former Homestake Mine 5
2010 Resolution Copper 4
2009 HDR Engineering, Koewee Dam 6
2008 Oxbow Mining LLC, Elk Creek Mine 5
2008 UtahAmerican Energy Inc., West Ridge Mine 4
2007 Gannett Fleming, Roanoke Rapids Dam 18
2007 Canyon Fuels, SUFCO Mine 2
2007 Chemical Lime Company, Kimballton Mine 11
2005 Climax, Henderson Mine 2
2004 Andalex Resources, Aberdeen Mine 4
2003 Acres International, Robert Moses Niagara Power Project 18
2003 U.S. Bureau of Reclamation, Seminoe Dam 19
2003 FMC, Westvaco Mine 12
2003 OCI Wyoming, LP, Big Island Mine 18
2002 OCI Wyoming, LP, Big Island Mine 6
2002 Dravo Lime Co., Black River Mine 15
2000 Mountain Coal Company, West Elk Mine 8
2000 OCI Wyoming, LP, Big Island
Mine
40
2000 NIOSH, Tanoma Mine 2
2000 CDC, Norton Energy Project 6
1999 CDC, Norton Energy Project 2
1999 Stone & Webster Engineering, Santeetlah Dam (Fall ’99) 15
1999 Solvay Minerals 35
1999 Stone & Webster Engineering, Santeetlah Dam (Winter ’99) 15
1998 Stone & Webster Engineering, Santeetlah Dam (Fall ’98) 67
1998 OCI Wyoming, LP, Big Island Mine 25
1998 Energy West, Deer Creek Mine 5
1998 Bowie Resources, Bowie #2 Mine 8
1998 Stone & Webster Engineering, Santeetlah Dam (Spring ’98) 68
1997 OCI Wyoming, LP, Big Island Mine 14
1997 Stone & Webster Engineering, Santeetlah Dam 20
1997 Energy West, Deer Creek Mine 20
1996 Solvay Minerals 9
1995 Solvay Minerals 72
1994 Sandia National Laboratories, DNA 9
Overcoring up from 4.5-ft wide by 7-ft high gallery in a concrete dam with a Longyear CP-65 pneumatically driven core drill.
CSIRO Hollow Cell Inclusion Gage
A CP-65 pneumatically powered core drill is mounted to the upstream face of a concrete dam for overcoring. A barge is tied off to the face of the dam for safe operation of the drill and overcoring activities.
Overcoring Horizontally in an Underground Trona Mine
Project Summaries & Publications: Stress Measurements
Have questions? Contact our technical staff for answers.