Holdfast Training Services Trial Blog

Site Two Fifty One – General Update

This week I thought I would blog generally about site activities taking place to give a feel of what I am doing. Main activities are: sub-station demolition, preparation for the capping beam installation, office ground bearing piles (CFA), pile mattress construction for a small section of sheet piling and the most laborious task of all, welfare establishment. My focus is on the capping beam, although when the project manager and project engineer are off-site my responsibilities tend to extend a little further, in fact, I am not sure where they stop!

All the activities themselves are fairly low level (no multi-span bridge beams for example) but the planning, co-ordination, resourcing and commercial aspects as a whole make for a varied experience.

Old sub-station at top of access ramp

Demolition of the old sub-station begins

and finishes pretty soon afterwards

Breaking of piles to cut off level

Underpinning the pre-existing wall

Preparation for the capping beam

Piling continues at much improved rate

Welfare cabins arrive.

Excavator sitting on pile mattress where future sheet piling will take place.

Progress. We are currently about 3 weeks behind schedule, mostly due to pile rig breakdowns, a few unforeseen ground conditions and a bit of a few things just taking longer than planned.

Foreseeable practical issues.

1. Sheet Piling – I can see that preparation for the sheet piling is going to be difficult – we have potentially struck a fibre optic cable (green pipe sheath below) and there are many other cables which led into the old substation. How to resolve – careful hand digging and attempting to recognise if cables were part of the old substation or not. How to resolve cutting a fibre optic cable – I am holding my breath.

Fibre optic cable strike? If the IT companies all arrive on site on Monday, I have a problem.

2. Capping beam – as you can see there are male pile tops to cut, king post (vertical steel columns) and a complicated as you like “shear stub” connection (Richard – this may ring bells from my questions away-back in December) for the ground force props to enable excavation of one further level. This is surmountable but is going to be painstaking threading re-bar through the stub as well as lifting them about (each way in excess of 200kg).

3. Ground water – the ground water level is about at bottom of blinding of the capping beam. We cannot drain the bath that is the entire site because the secant wall is not finished. Current method of resolution: Effectively at the moment we pump water out for it to recharge into the hole, albeit giving us long enough to work for the day. Should it rain heavily for days there will be a problem.

Other points:

ICE webinar brief on CDM 15 on Monday for those interested!

Another cyclist was killed by a construction vehicle in London this week. Laing O’Rourke are a Construction Logistics and Cyclist Safety (CLOCS) Champion but do all vehicles that deliver to site comply with the minimum safety requirements… to be continued!