Environmental Engineering Reference
In-Depth Information
FIGURE 4.21
Schematics of the multiple-position borehole extensometer: (a) rod type, (b) wire type. (From Silvera, J.F.A.,
Proceedings of the 1st Congress
, Brasileira de Geologia de Engenharia, Rio de Janeiro, August, Vol. 1, 1976, pp.
131-154. With permission.)
4.3.5
Acoustical Emissions
Description
Acoustical emissions refer to subaudible noises resulting from distress in soil and rock
masses. They are also termed microseismic activity, microseisms, seismic-acoustic activity,
stress-wave activity, and rock noise.
Applications
Monitoring acoustical emissions provides an aid to the anticipation of failure by rupture
or internal erosion. The method was first used in the underground mining industry to
detect the instability of the mine roof, face, or pillar rock.
