Carlon External Load Calculation for Buried Conduit - Manual (Page 3)

EXTERNAL LOAD CALCULATIONS FOR DIRECT BURIED CONDUIT
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THE MOMENT OF INERTIA (I) EQUALS THE WALL THICKNESS (t) CUBED,
DIVIDED BY TWELVE (12). I = t
3
/12.
THE MEAN RADIUS (r) EQUALS THE OUTSIDE DIAMETER (O.D.) MINUS
THE WALL THICKNESS (t) DIVIDED BY TWO (2). r = (O.D. - t)/2
PIPE STIFFNESS FOR DB60 IS EQUAL TO 60 lb/in
2
AND FOR DB120 IS
EQUAL TO 120 lb/in
2
. 4” SCHEDULE 40 CONDUIT WILL HAVE A PIPE
STIFFNESS OF 346 lb/in
2
(MINIMUM WALL THICKNESS).
MATERIALS SUITABLE FOR FOUNDATION AND EMBEDMENT ARE
DEFINED ACCORDING TO THE UNIFIED SOIL CLASSIFICATION SYSTEMS
(USCS) IN ASTM D2487, “STANDARD METHOD FOR CLASSIFICATION OF
SOILS FOR ENGINEERING PURPOSES”. BEDDING SOIL MODULUS (E
1
)
SHALL BE 2000 LB/IN
2
FOR CLASS IA AND IB SOILS AND 1000 LB/IN
2
FOR
CLASS III SOIL. CLASS IA MATERIALS PROVIDE MAXIMUM STABILITY AND
PIPE SUPPORT FOR A GIVEN DENSITY DUE TO ANGULAR INTERLOCK OF
PARTICLES. CLASS III MATERIALS PROVIDE LESS SUPPORT FOR A
GIVEN DENSITY THAN CLASS I MATERIALS. HIGH LEVELS OF
COMPACTIVE EFFORT MAY BE REQUIRED UNLESS MOISTURE CONTENT
IS CONTROLLED.
DEAD LOAD (DL) IS EQUAL TO THE UNIT WEIGHT OF THE BACKFILL ( γ)
TIMES THE HEIGHT OF COVER (H) DIVIDED BY 144.
DL = γγγγ * H/144
DL = DEAD LOAD (lb/in
2
)
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