Environmental Engineering Reference
In-Depth Information
Tension
cracks
(h)
(e, g)
(e, g)
(L or m, r, q, n)
(e, g)
(o)
(L or m,
r, q, n)
(a, i)
(e, g)
(o)
(q, n)
(a)
(j)
(o)
FIGURE 4.41
Instrumentation for rock cut. Legend: (a) precise surveying; (e) tiltmeter; (g) convergence meter; (h) strain
meter; (i) terrestrial photography; (j) vibration monitoring; (L) inclinometer; (m) deflectometer; (n) shear-strip
indicator; (o) borehole extensometer; (q) acoustical emissions device; (r) piezometers.
geodimeter that provide rapid measurements of the entire slope, and terrestrial stereopho-
tography (i) that provides a periodic record of the entire slope face. GPS will find increas-
ing use for long-term monitoring.
Bottom heave is monitored by the optical survey of monuments or “settlement points”;
it often precedes a major slope failure.
Vibrations from blasting and traffic, which may affect stability, are monitored (j) and
cleft-water pressures are monitored with piezometers (r).
Installations
Inclinometers, deflectometers, piezometers, and extensometers are often limited to early
excavation stages to obtain data for the determinations of stable slope inclinations. They
are expensive instruments to install and monitor, and not only will they be lost if failure
occurs, but in mining operations many will be lost as excavation proceeds. In addition,
they monitor only limited areas by section.
Tiltmeters, convergence meters, and optical surveys are both economical and “retriev-
able,” and provide for observations of the entire slope rather than a few sections; therefore,
they provide the basic monitoring systems. In critical areas, where structures or workers are
endangered if a collapse occurs during mining operations, MPBX extensometers and the
acoustical-emissions device are used as early warning systems.
Case 2: Soil Slopes
Objectives
In soil slopes, the objectives are to detect movements when they first occur since in
many instances slope failures develop gradually; and, when movement occurs, to
