UFC 3-220-01N
15 AUGUST 2005
Borrow Excavation
8-1.7
8-1.7.1
Borrow Pit Exploration. Make exploratory investigations to determine
the suitable sources of borrow material. Laboratory tests to determine the suitability of
available materials include natural water contents, compaction characteristics,
grain-size distribution, Atterberg limits, shear strength, and consolidation. Typical
properties of compacted materials for use in preliminary analyses are given in Table 8-
1.4. The susceptibility to frost action also should he considered in analyzing the
potential behavior of fill material. The scope of laboratory testing on compacted
samples depends on the size and cost of the structure, thickness and extent of the fill,
and also strength and compressibility of underlying soils. Coarse-grained soils are
preferred for fill; however, most fine-grained soils can be used advantageously if
attention is given to drainage, compaction requirements, compaction moisture, and
density control.
The number and spacing of borings or test pits for borrow exploration must be sufficient
to determine the approximate quantity and quality of construction materials within an
economical haul distance from the project. For mass earthwork, initial exploration
should be on a 61 meters (200 foot) grid. If variable conditions are found during the
initial explorations, perform intermediate borings or test pits. Explorations should
develop the following information:
A reasonably accurate subsurface profile to the anticipated depth of
excavation
Engineering properties of each material considered for use
Approximate volume of each material considered for use
Water level
Presence of salts, gypsums, or undesirable minerals
Extent of organic or contaminated soils, if encountered
8-1.7.2
Excavation Methods. Consider the following when determining
excavation methods:
Design and efficiency of excavation equipment improves each year.
Check various construction industry publications for specifications.
Determine rippability of soil or rock by borings (RQD and core recovery,
see UFC 3-220-10N), geophysical exploration, and/or trial excavation.
8-1.7.3
Utilization of Excavated Materials. In the process of earthmoving there
may be a reduction of the volume ("shrinkage") because of waste and densification, or
an increase of volume ("swell") in the case of rock or dense soils, because the final
density is less than its original density.
Determine total borrow volume, VB, required for compacted fill as follows:
8-30
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