CIVIL ENGINEERING FORMULAS

HIGHWAY AND ROAD FORMULAS 287

than one pipe diameter, the total load TL is assumed to act on the pipe, and
TLPv; that is,

(11.30)

When the height of cover is equal to, or greater than, one pipe diameter,

(11.31)

where Pvdesign pressure, kip/ft^2 (MPa/m^2 )
Kload factor
DLdead load, kip/ft^2 (MPa /m^2 )
LLlive load, kip/ft^2 (MPa /m^2 )
Iimpact, kip/ft^2 (MPa /m^2 )
Hheight of cover, ft (m)
Sspan or pipe diameter, ft (m)

Ring Compression

The compressive thrust C, kip/ft (MPa /m), on the conduit wall equals the radi-
al pressure Pv,kip/ft^2 (MPa /m^2 ), acting on the wall multiplied by the wall
radiusR, ft (m); or CPvR. This thrust, called ring compression, is the force

PvK(DLLLI) HS

PvDLLLI HS

1.8

1.6

1.4

1.2

Load factor,

K

1.0

0.8

0.6

70 75 80

Specified soil compaction, %

Standard AASHTO T-99

85

At 85%

Std. density

K = 0.86

90 95

FIGURE 11.11 Load factors for corrugated steel pipe are plotted

as a function of specified compaction of backfill.