Walers, Dyvidags and Rubber Ducks

The piling works are complete which will result in a lot less of the continuous noise experienced in the area. Thanks to our neighbours for their patience while this took place. New words continue to be thrown at me but at least they're more entertaining than my usual diet of arts and local governmnet acronyms!

This week we are continuing to dig out the first part of the new basement area for the glass wing extension by the Lyceum Theatre. The process has been explained to me a number of times but I still end up feeling like I am back at school having logarithms explained to me.

John Neilson, our Site Liaison Manager can explain it better: "The limit of the excavation works is bounded by the previously completed piling works, which as the ground is dug away exposes the buried steel H-section columns or 'kingposts' spaced at approximate 2.0 metre centres. As the steel columns are initially exposed to a depth of approximately 1.2 metres, plywood shutters are then erected between the adjacent kingposts to form a retaining wall, on an install one, skip one basis which facilitates the pouring sequence. The internal shutters are strengthened by timber members called 'walers' or 'strongbacks' and are clamped to the steel sections by special clamps called 'dyvidags' (many of which are sacrificed in the pours) to prevent the plywood shutters from moving when the concrete is poured. As the external side of the retaining wall is against the existing ground which it is to hold back, no shutters are required and the concrete can be poured directly against this ground. Once the concrete is poured and the concrete hardened, the first set of shutters are stripped, and the process is repeated for the skipped sections of the retaining wall.

Once the adjacent retaining wall sections in one area of the basement are poured and the concrete is strong enough to retain the ground behind it, excavation will commence once again to a depth of approximately 2.0 metres to 2.4 metres deep, and the shuttering process repeated using a slightly modified method which allows the concrete to be poured behind the shutter by means of a method similar to the way the postman inserts letters into your letterbox. This method is then repeated over and over in approximate 1.0 metre depths until the full depth of the Basement is achieved and the full height retaining wall completed. Any excess concrete from the 'letterbox' pours is carefully removed as works progress to give a fairly smooth finished surface to the retaining wall. It should be noted that as the excavation works for the basement get deeper, the more likely the chances of striking rock which will require the use of the 'pecker' or pneumatic drill mounted on the front end of the rubber wheeled excavator (or as the machine is known in the construction trade 'a rubber duck'). This operation is what may cause the noise and/or some minor vibration that you may hear or experience.