Michigan Aggregates Association

General Highwall Safety Guidelines

For Working Faces

Planning:

  1. Note and map the location of structural discontinuities (i.e., joints, faults, and bedding planes) and underground mine workings relative to the existing highwall and in the direction of mining.
  2. Anticipate unstable highwall conditions in the vicinity of intersecting structural discontinuities and underground mine workings.
  3. Design highwalls for stability in local geological conditions including stratification, structural discontinuities, rock strength, groundwater seepage, and underground mine workings.
  4. Shorter highwalls and wider benches can improve highwall stability by reducing overburden load and the amount of material that could become unstable.
  5. Surface runoff diversions and groundwater drains can improve highwall stability by reducing erosion and internal water pressure.

Inspection:

  1. Frequently inspect highwalls in the work area, especially after rainfalls, snowmelts, freeze/thaw events, and blasting.
  2. In addition to mass stability, situations were rockfall conditions may be present need to be considered.  The stability of detached blocks should be evaluated.  Sloping or irregular faces can cause a falling rocks to be projected away from the face.
  3. Excessive amounts of rainfall, runoff, or pooled water behind the crest, rapid freezing and thawing, or blast vibrations may destabilize the highwall.
  4. Inspect all portions a highwall (i.e., the toe, the face, and especially behind the crest) from several different angles.
  5. Cracks in the face or behind the crest, bulging at the toe, and fallen rocks at the toe may be signs of instability.
  6. Report noticeable changes in the condition of the highwall to supervisory personnel.

Operation:

  1. Avoid exiting vehicles and equipment when working near a highwall.
  2. Avoid placing yourself between equipment and the toe or crest of a highwall.
  3. Operate mobile equipment perpendicular to a highwall face to minimize exposure.
  4. Do not undercut the highwall face.

For Permanent Faces:

  1. Installing canopies (steel sets, arches, tunnel liners, etc.) at mine portals can protect personnel from falling debris.
  2. Wire mesh, screening, or other rock fall catchments can be installed on permanent highwalls to protect workers from rock falls where blocky conditions exist.
  3. Avoid unprotected access to the toe of a non-working highwall by posting warning signs and installing properly designed berms or other barriers at a safe distance.