Page 306 - Buried Pipe Design

Rigid Pipe Products 277

Overfill (SW, ML, or CL)

H
/6 (Min.)
D O
D (Min.)
D O O

Haunch (see Table 5.12)
D i
Lower Side
(see Table 5.12)

Bedding (see Table 5.12) Middle Bedding
D /3
O
Outer Bedding Loosely Placed
Material and Uncompacted Bedding
Foundation
Compaction Each Except for Type 4
Side, Same
Requirements
as Haunch
Figure 5.10 Standard embankment installations.
(See ASCE Standard Practice for Concrete Pipe Design, Chap. 8 of ACPA
Concrete Pipe Technology Handbook, for details.)
Type 1 is considered the highest-quality standard installation.
Type 2 is the highest-quality standard installation where certain
native soils are permitted to be used with proper compaction in the
haunch and bedding zones.
Type 3 permits the use of soils in the haunch and bedding zones hav-
ing less stringent compaction requirements, justifying less stringent
inspection requirements with granular soils and some native soils.
Type 4 is intended for installations where the most cost-effective
design approach is to specify minimal requirements for embedment
soil type and density, together with a pipe having sufficient strength
to safely resist the increased structural effects that result from
using low-quality embedment soils. Thus, type 4 has no require-
ments for control of compaction and type of placed soil used in the
bedding and haunch zones; except if silty clay soils are used in the
haunch zone, or below this zone, they must be compacted to at least
85 percent of standard Proctor density, and plastic clays should not
be used in this zone.