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 MIL-HDBK-1025/4
4.10.4
Toe of Wall Embedded in Stiff, Nonsensitive Fine Grained Soil.
Locate hinge (by trial and error) so that the value of:
Equation:
CxD
or
CxD
>
4.7
(1)
)))
)))
)
R'+B,
R+B,
Where:
C
=
Shear strength of the soil below drainage level.
D
=
Depth below hinge.
R+b, =
or R'+B, = Reaction at hinge.
This method is limited to cases where the vertical effective pressure at the
dredge line is less than 2C (see Figure 34).
4.11
Detailed Design Considerations. General details of design shall
conform to the requirements of MIL-HDBK-1025/6.
4.11.1
Deadmen and Sheet Pile Anchors.
Design according to the
requirements of DM-7.02.
4.11.2
Pile Supported Anchors.
Design shall conform to the requirements
of DM-7.02.
4.11.3
Wales. Wales should be located at a level which minimizes the
moment in the sheet piling. Usually, this means as low a level as is
economical. Generally, the wales are set at mean low water, as a compromise
between the cost of installing the anchor system and the cost of (moment in)
the sheet piling.
An advantage of setting the wales near mean low water is that the
tie rods are in permanently saturated ground. This reduces the corrosion rate
in the portions of the tie rods behind the wall. However, the wales, the
projecting end of the tie rods and the bolts, plates, and washers on the
outside face of the wall are in a zone of active corrosion and should be sized
generously.
Wales may be set at lower levels where required, but levels more
than 2 ft (0.61 m) below mean low water require installation by divers.
(Refer to Section 4, para. 4.3.2.
Tie Rods.
Threaded portions of tie rods should be upset.
4.11.4
Tie rods and appurtenances shall be protected against corrosion in
accordance with the requirements of NAVFAC Guide Specification NFGS-09809,
Protection of Buried Steel Piping and Steel Bulkhead Tie Rods. If this is
done, experience suggests that cathodic protection is not required unless
special circumstances of chemical activity or stray current exist.
Deterioration of the tie rods is concentrated in the 3- to 5-ft (0.914 to
1.52 m) section adjacent to the bulkhead, and special protection should be
provided in that location. In general, do not use wire rope for tie rods.
Where tie rods are long, vertical intermediate supports shall be
provided at maximum 30-ft (9.14 m) centers to prevent sagging. Consider use
of a box over the tie rod to avoid loading the rod as the subsoil
consolidates.
49
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