UFC 3-220-01N
15 AUGUST 2005
Table 8-2.2
Compaction Density as a Percent of ASTM D 1557 Laboratory Test Density
ASTM D 1557 Maximum Density, in Percentage
Cohesive Soils
Cohesionless Soils
Fill/Embankment/Backfill
Under proposed structures, building
95a
Slabs, steps, paved areas
90
Under sidewalks and grassed areas
85
90
Sub-grade
Under building slabs, steps and
Paved areas / top 300 mm (12inches)
90
95
Under sidewalks, top 150 mm (6 inches)
85
90
a
Maybe 85% relative density / whichever is higher
8-3
BACKFILL
8-3.1
Introduction. The greatest deficiencies in earthwork operations around deep-
seated or subsurface structures occur because of improper backfilling procedures and
inadequate construction control during this phase of the work. Therefore, primary emphasis in
this section is on backfilling procedures. Design and planning considerations, evaluation and
selection of materials, and other phases of earthwork construction are discussed where
pertinent to successful backfill operations. Although the information in this section is primarily
applicable to backfilling around large and important deep-seated or buried structures, it is also
applicable in varying degrees to backfilling operations around all structures, including conduits.
8-3.2
Planning and Design of Structures and Excavations to Accommodate
Backfill Operations. Many earthwork construction problems can be eliminated or minimized
through proper design, thorough planning, and recognition of problem areas effecting backfill
operations. Recognition and consideration must be given in planning to design features that
will make backfilling operations less difficult to accomplish. Examples of problem areas and
how forethought in design and planning can help to eliminate backfill deficiencies are
presented in the following paragraphs.
8-3.2.1
Effect of Excavation And Structural Configuration On Backfill Operations.
Some of the problems encountered in earthwork construction are related to the excavation and
the configuration of the structures around which backfill is to be placed. It is the designer's
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