FLOOD06430

• County: Statewide
• Basin: Statewide
• Title: Conduits, Culverts and Pipes
• Date: 3/3/1969
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

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EM 1110-2-290Z
S Mar 1969

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For Case 1, W. - 1.5 y b,H. __ _ __ __ _ __ _ _ _ _ _ _ _ _ __ __ __ _ _ _ _ __ _ _ __ _ U _ __ _ __ __ __ _ U _ _ (8)

For Case 2, W. - y b,H. __ __ _ _ _ _ __ __ __ _ __ _ __ _ __ _ __ _ __ _ h _ __ _ __ U U _ _ _ _ _ __ __ _ U (9)

or the unit vertical load, w.. is given by the equations:

For Case 1, w. - 1.5 y H. _ __ _ _ __ __ _ _ _ _ _ _ _ __ __ __ _ _ _ __ _ __ __ _ _ __ __ __ U _ _ __ __ -- _ h - (10)

For Case 2, w. = y H. __ _ _ __ __ _ _ __ __ __ _ __ _ __ __ _ __ __ _ _ _ __ __ _ _ __ __ U U h __ _ _ __ _ _ - (11)

The horizontal loading per square foot should be taken as follows:

For Case 1, P. - 0.5 y H __ __ _ _ __ __ __ __ __ _ _ __ _ _ _ __ __ __ _ _ __ __ _ _ _ _ __ __ __ __ __ _ -- -- - (12)

For Case 2, P. - y H _ __ __ _ __ __ _ _ Uh __ ___ __ _ _ _ _ __ __ __ _ -- -- -- ou_ --. _ -- -- -- -- -- (18)

Normal allowable working stresses should apply for both Case 1 and Case 2.
Where submergence and water surcharge are applicable, the effects thereof must be consid-
ered as for Condition 1. In such cases, the vertical load as computed by equation 8, 9, 10, or 11
using the submerged weight of the material should be increased by the weight of the projected
volume. of water above the conduit including any surcharge water above the fill surface. Note
that where a clay blanket is applied to the face of the dam, the weight of water above the blan-
ket must be included but the soil weight below the blanket and above the phreatic line (or the
line of saturation where capillarity exists) is that for the natural drained condition. The hori-
zontal unit pressure is found by adding full hydrostatic pressure to the value of P. obtained
from equation 12 or 13 using the submerged weight of the material.
(4) Special Conditions. If conditions are encountered that are considered to warrant
deviation from the above loading criteria, justification for the change should be submitted with
the analysis of design. However, the designer must first satisfy himself that he has selected the
most economical method of installation. Where the rock surface occurs above the elevation of
the bottom of the conduit, the designer should investigate the relative costa of (a) excavating
away from the conduit and backfilling between the conduit and the excavation line, allowing
sufficient space between the conduit and the excavation line for operation of compaction rollers,
and (b) placing the conduit directly against rock as indicated for the following conditions.
Where the conduit walls are placed directly against rock and the rock surface is at or
above the top of the crown, the soil weight should be taken as 1.0 times the weight of mate-
rial above, rather than 1.5, and the lateral pressure should be hydrostatic only, where applica-
ble. Where the rock surface is at an intermediate level between crown and invert, judgement
must be used in selecting a value between 1.0 and 1.5 to multiply by the weight of material above
to obtain the correct soil design load. Lateral soil pressure should be applied only above the rock
level and hydrostatic pressure as applicable over the full height of conduit. For either of the
above cases, the condition with no hydrostatic pressure should also be considered.

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5. Design.

a. Reinforced concrete design stresses.
(1) Cast-in-place conduits.
fo' = 4000 psi or 5000 psi (except for small conduits under low fills).
f, = 0.45 fo' (max. fiber stress)
f, :<; 2 VfT(Principal tensile stress)
f, - 20,000 psi allowable tension based on intermediate grade steel.
Shear and diagonal tension requirements have been met when the principal diagonal tension,
f" at points of maximum shear, does not exceed 2 \/T.'. This may be determined by the formula:

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