Civil Engineering Reference
In-Depth Information
requires careful consideration. Large-scale tests have demonstrated this type of
clamp does not transfer structural forces. Furthermore, the typical coefficient of
friction between liner and steel is considerably lower than previously assumed
values. These clamps require periodic inspection to confirm bolt tension.
In summary, a stressed elastomer-lined clamp is one of the quickest clamps
to deploy and requires a reasonably detailed survey. It has poor axial and bend-
ing load transfer capacity. It is ideal for clamping on intact tubular members or
for adding members and appurtenance supports.
The required equipment for installation is the same as for the stressed
grouted clamp.
7.12.10 Example: Drilling Platform Stabilization after
Hurricane Lili
A drilling platform located in 71 m of water was severely damaged when
Hurricane Lili passed through the Gulf of Mexico in 2002. In order to stabilize
the platform during well plug, in 2003 additional piles were installed to
strengthen the damaged platform.
The leeward pile was severed at 6.3 m below the base of jacket leg. The pile
severance was located at the mud line due to the lean of the platform. In addi-
tion, the remaining three piles were assumed to be damaged at or below the mud
line due to platform rotation.
Divers performed member cleaning, clamp installation and grouting opera-
tions. Once the grout had sufficiently cured within the clamp annulus, the stud-
bolts were tensioned to the required tensile loads. Heavy lifting and pile installation
were carried out.
Note that several trials using different repair methods were considered, such
as guy wires to piles and attached to the undamaged nearest platform. Analyses
indicated that templates were required in addition to severed pile reinstatement
to provide sufficient torsional resistance against potential hurricane wave loads.
The strengthening scheme consisted of two templates, a stressed grouted clamp
and five piles.
The repair procedure for the platform was:
Clean exposed pile
●
Cut holes in base of severed pile and place support clamp
●
Install sleeve clamp around exposed pile using support clamp
●
Close clamp and hand-tighten several bolts
●
Check seals for leakage and place grout
●
Once grout has reached required cube strength, stress the 32 2-inch stud-
bolts to required tensile load
●
Lower piles through sleeves to self-penetration depth
●
Hammer piles to the required 200 feet of penetration
●
Grout pile sleeves.
●
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