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Mooring dolphins & Piers

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Subcon has completed extensive grouting works of mooring dolphins and jetty piles commonly found on coastal resource infrastructure. Subcon has successfully completed grouting works on Australia’s largest export terminal jetty.

FAQ’s

All pile sleeves should have following things in common:
1/. A grouted annulus;
2/. Shear Keys;
3/. Grout Seals;
4/. Grout distribution system;

Often engineers specify non skrink grout believing the grout forms a chemical bond with the steel sleve. It does, however this bond is readily broken once the grout has set. Simple thermal expansion due to the sun will cause the sleeve diameter to grow sufficiently to break the bond with the grout. Over time this cyclic degradation will cause the grouted connection to fail. We recommend shear keys are used in 100% of cases. Shear keys are a cost effective way to create a mechanical bond between the pile and the sleeve, guaranteeing the connection for eth life of the asset. And expensive, non shrink grouts are not required!

All grout pours should be over pumped to displace any priming grout and diluted grout from the connection. Regardless of whether you have used antiwashout agents, grout will always mix and dilute with the seawater and surrounds. There is always water in the hose and often there is a small fall from the end of the grout hose to the base of the grout seal for example both of which cause some dilution of the grout.

So we recommend about 1m3 of grout is over poured or that allowance is made in the connection length to contain some lower strength grout.

Our preference is to grout through a stinger deployed to the base of the annulus and to retract this as the grout is placed. This means no expensive pipework is needed and the grout job can be halted and restarted as required.

Cold joints are not an issue as long as they are planned for. Grouting operations have to be stopped for many reasons: emergencies, weather stand offs, mechanical breakdowns, power outages to name a few. So it is essential that stoppages are allowed for. The key issue with a cold joint is the depth of the weaker material. Diluted grout will “float” to the top of a cold joint creating a zone of weaker material. This can be mitigated by allowing some contingency in the length of the connection and by incorporating shear keys at regular spacings of around 300mm. finally making allowance for a contingency grout stinger means the surface of the joint can be flushed and the new grout can be placed directly onto the surface of the previous pour, minimising mixing of the new grout and weakening of the joint.

Yes you do. Any fall through the water column will dilute and weaken the grout. We recommend the use of fixed piping for primary and secondary grout pours and to always allow for access with a stinger.

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