Manual

EXTERNAL LOAD CALCULATIONS FOR DIRECT BURIED CONDUIT
25701 Science Park Drive
Cleveland, Ohio 44122
216-464-3400
1-800-3CARLON (322-7566)
www.carlon.com
EXTERNAL LOADS ON DIRECT BURIED PVC OR HDPE CONDUIT OR DUCT
FALL INTO TWO CATEGORIES, DEAD LOADS (EARTH LOADS) AND LIVE
LOADS. DEAD LOADS ARE BASED ON THE WEIGHT OF THE COLUMN OF
SOIL ABOVE THE BURIED CONDUIT OR DUCT. LIVE LOADS ARE FROM
DIFFERENT SOURCES SUCH AS HIGHWAYS, AIRPORT RUNWAYS OR
RAILWAYS. LIVE LOADS HAVE LITTLE EFFECT ON CONDUIT
PERFORMANCE EXCEPT AT SHALLOW DEPTHS (4’ OR LESS FOR
HIGHWAY LOADS).
THE TOTAL LOAD IS THE SUMMATION OF THE DEAD LOADS AND OF THE
LIVE LOADS. THE TOTAL LOAD SHALL BE LESS THAN THE LOAD
(MAXIMUM LOAD) REQUIRED TO CHANGE THE INSIDE DIAMETER OF THE
CONDUIT OR DUCT BY ARBITRARY DATUM OF 5% DEFLECTION. THIS
DEFLECTION, CAUSED BY THE TOTAL LOAD, IS FAR BELOW THAT WHICH
WOULD CAUSE DAMAGE TO THE PVC WALL OF THE CONDUIT OR DUCT.
THE MAXIMUM LOAD (W) CAN BE CALCULATED WITH THE FOLLOWING
FORMULA:
W = [∆∆
∆∆
X *(0.149*PS + 0.061*E
1
)]/[D*K]
W = MAXIMUM LOAD (lb/in
2
)
∆∆
∆∆
X = DEFLECTION (%/100)
PS = PIPE STIFFNESS (lb/in
2
)
E_ = BEDDING SOIL MODULUS (lb/in
2
)
D = DEFLECTION LAG FACTOR
K = BEDDING CONSTANT
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