UFC 3-220-01N
15 AUGUST 2005
TABLE 8-1.2
Factors Controlling Excavation Stability
Construction
Objectives
Comments
Activity
Excavation and
Pipe trenching,
Analyze safe slopes (see UFC3-220-10N) or bracing
Grading
basement
requirement (see Chapter 8-1.3), effects of stress reduction
excavation, site
on over consolidated, soft or swelling soils and shales.
grading.
Consider horizontal and vertical movements in adjacent
areas due to excavation and effect on nearby structures.
Keep equipment and stockpiles a
safe distance from top of excavation.
Excavation Wall
To support vertical
See Chapter 6 for wall design. Reduce earth movements and
Construction
excavation walls, to
bracing stresses,where necessary, by installing laggingon
stabilize trenching in
front flange of soldier pile. Consider effect of vibrations due to
limited space.
driving sheet piles or soldier piles. Consider dewatering
requirements as well as wall stability in calculating sheeting
depth. Movement monitoring may be
warranted.
Blasting
To remove or to
Consider effect of vibrations on settlement or damage to
facilitate the
adjacent areas. Design and monitor or require the contractor
removal of rock in
to design and monitor blasting in critical areas; require a pre
the excavation.
construction survey of nearby structures.
Anchor or Strut
To obtain support
Major excavations require careful installation and monitoring,
Installation,
system
e.g., case anchor holes in collapsible soils; measure stress in
Wedging of Struts,
stiffness and
ties and struts; wedging, etc.
Pre-stressing Ties
interaction.
8-5
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