36
Geotechnical News • December 2015
GEOTECHNICAL INSTRUMENTATION NEWS
Table 1. Some instruments that can be considered for monitoring internally braced excavations
Possible geotechnical
questions
Measurement
Some instruments that can be considered
What are the initial site
conditions?
Groundwater pressure
Vertical displacement
Widths of cracks in structures
Open standpipe piezometers
Vibrating wire piezometers installed by the fully-
grouted method
(Pneumatic piezometers)
Conventional surveying methods
Remote methods
Crack gauges
Are the struts being installed
correctly?
Load in struts
Calibrated hydraulic jack
Is the excavation stable, and
are nearby structures
being affected adversely
by ground movements?
Settlement of ground surface,
structures and top of support-
ing wall
Horizontal displacement of
ground surface, structures, and
exposed part of supporting
wall
Change in width of cracks in
structures and utilities
Subsurface horizontal desplace-
ment of ground
Subsurface settlement of ground
and utilities
Load in struts
Groundwater pressure
Bottom heave
Conventional surveying methods
Remote methods
Conventional surveying methods
Remote methods
(Convergence gauges)
Crack gauges
Inclinometers
In-place inclinometers
(Fixed borehole extensometers)
(Fibre-optic instruments)
Probe extensometers
(Fixed borehole extensometers)
Surface-mounted strain gauges
Open standpipe piezometers
Vibrating wire piezometers installed by the fully-
grouted method
(Pneumatic piezometers)
Probe extensometers
Is an individual strut being
overloaded?
Load in strut
Surface-mounted strain gauges
Is the groundwater table
being lowered?
Groundwater pressure
Open standpipe piezometers
Vibrating wire piezometers installed by the fully-
grouted method
(Pneumatic piezometers)
Is excessive bottom heave
occurring?
Bottom heave
Subsurface horizontal displace-
ment
Probe extensometers
Inclinometers
In-place inclinometers
