15 AUGUST 2005
Factors Controlling Excavation Stability
Analyze safe slopes (see UFC3-220-10N) or bracing
requirement (see Chapter 8-1.3), effects of stress reduction
on over consolidated, soft or swelling soils and shales.
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.
To support vertical
See Chapter 6 for wall design. Reduce earth movements and
excavation walls, to
bracing stresses,where necessary, by installing laggingon
stabilize trenching in
front flange of soldier pile. Consider effect of vibrations due to
driving sheet piles or soldier piles. Consider dewatering
requirements as well as wall stability in calculating sheeting
depth. Movement monitoring may be
To remove or to
Consider effect of vibrations on settlement or damage to
adjacent areas. Design and monitor or require the contractor
removal of rock in
to design and monitor blasting in critical areas; require a pre
construction survey of nearby structures.
Anchor or Strut
To obtain support
Major excavations require careful installation and monitoring,
e.g., case anchor holes in collapsible soils; measure stress in
Wedging of Struts,
ties and struts; wedging, etc.