UFC 3-220-01N
15 AUGUST 2005
Exacavation Stabilization, Monitoring, and Safety
8-1.5
8-1.5.1
Stabilization. During the planning and design stage, if analyses indicate
potential slope instability, means for slope stabilization or retention should be
considered. Some methods for consideration are given in Chapter 6.
On occasion, the complexity of a situation may dictate using very specialized
stabilization methods. These may include grouting and injection, ground freezing, deep
drainage and stabilization, such as vacuum wells or electro-osmosis, and diaphragm
walls.
8-1.5.2
Monitoring. During excavation, potential bottom heave, lateral wall or
slope movement, and settlement of areas behind the wall or slope should be inspected
carefully and monitored if critical. Monitoring can be accomplished by conventional
survey techniques, or by more sophisticated means such as heave points, settlement
plates, extensometers or inclinometers, and a variety of other devices. See UFC 3-220-
10N.
8-1.5.3
Safety. Detailed safety requirements vary from project to project. As a
guide, safety requirements are specified by OSHA, see Public Law 91-596. A summary
of the 1980 requirements follows:
Banks more than 1.2 m (4 ft) high shall be shored or sloped to the angle of
repose where a danger of slides or cave-ins exists as a result of
excavation.
Sides of trenches in unstable or soft material, 1.2 m (4 ft) or more in depth,
shall be shored, sheeted, braced, sloped, or otherwise supported by
means of sufficient strength to protect the employee working within them.
Sides of trenches in hard or compact soil, including embankments, shall
be shored or otherwise supported when the trench is more than 1.2 m (4
ft) in depth and 2.4 m (8 ft) or more in length. In lieu of shoring, the sides
of the trench above the 1.2 m (4 ft) level may be sloped to preclude
collapse, but shall not be steeper than a 305 mm (1 ft) rise to each 152
mm (6 in) horizontal. When the outside diameter of a pipe is greater than
1.8 m (6 ft), a bench of 1.2 m (4 ft) minimum shall be provided at the toe of
the sloped portion.
Materials used for sheeting and sheet piling, bracing, shoring, and
underpinning shall be in good serviceable condition. Timbers used shall
be sound and free from large or loose knots, and shall be designed and
installed so as to be effective to the bottom of the excavation.
Additional precautions by way of shoring and bracing shall be taken to
prevent slides or cave-ins when:
o Excavations or trenches are made in locations adjacent to
backfilled excavations; or
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