Capabilities

DA Smith conducts 2D and 3D in situ stress measurements in rock and concrete via the United States Bureau of Mines (USBM) borehole deformation gage (BDG) or Commonwealth Scientific and Industrial Research Organisation (CSIRO) hollow inclusion cell (HI Cell) methods.

  • Biaxial testing for dam concrete Young's modulus, Walters Dam, Waynesville, North Carolina
    Biaxial testing for dam concrete Young's modulus, Walters Dam, Waynesville, North Carolina
  • HI Cell overcoring stress measurements, SURF, Lead, South Dakota
    HI Cell overcoring stress measurements, SURF, Lead, South Dakota
  • 6-inch overcore with HI Cell for biaxial testing of rock Young's modulus
    6-inch overcore with HI Cell for biaxial testing of rock Young's modulus
  • HI Cell halved after stress testing to inspect strain gauge bond integrity
    HI Cell halved after stress testing to inspect strain gauge bond integrity
  • Preparing HI Cell for placement downhole, Resolution Copper, Superior, Arizona
    Preparing HI Cell for placement downhole, Resolution Copper, Superior, Arizona
  • BDG overcore stress measurements, Robert Moses Niagara Dam, Lewiston, New York
    BDG overcore stress measurements, Robert Moses Niagara Dam, Lewiston, New York
  • HI Cell preparation, Peabody coal mine
    HI Cell preparation, Peabody coal mine
  • Overcoring stress measurements, Arch Coal Leer Mining Complex, Leer Coal Mine, Grafton, West Virginia
    Overcoring stress measurements, Arch Coal Leer Mining Complex, Leer Coal Mine, Grafton, West Virginia
  • Overcoring stress measurements, Resolution Copper Mine, Superior, Arizona
    Overcoring stress measurements, Resolution Copper Mine, Superior, Arizona
  • Stress relief response, East Boulder Mine, Stillwater, Montana
    Stress relief response, East Boulder Mine, Stillwater, Montana
Overcoring for Measuring Stress
Overcoring for Measuring Stress

Stresses in rock are sometimes sufficiently high to cause rock bursting, spalling, buckling, heaving, or other ground control problems. In such cases, knowledge of the stress is of fundamental importance to the design and construction of structures in rock. Even in cases where the effects of stress are less dramatic, the optimum shape, orientation, and layout of underground structures, as well as the effectiveness and ultimate cost of rock support systems can be significantly impacted by the in situ rock stress. Stress measurements in concrete dams are also a valuable tool for evaluating structural stability and calibrate numerical models.

We measure rock stress via the two most common types of overcoring which utilize either the USBM borehole deformation gauge or the CSIRO hollow inclusion cell. Both instruments measure strain relief in the borehole wall of a pilot hole (1.5-inch-diameter) as it is overcored using a larger diameter (6-inch-diameter) bit.

We have completed more than 1,500 overcore stress measurements with our equipment in gold, copper, platinum, molybdenum, trona, oil shale, limestone, and coal mines, and in tunnels, concrete dams, and other civil structures.

Overcore Drilling
Overcore Drilling

Our core drilling rigs 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 stress in mines, tunnels, and concrete dams. As a general guideline, the pre-mining (native) stress state can be obtained by overcoring at a distance greater than 2.5 times the effective diameter of the entry.

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, angled, horizontal, to vertical down.