Holdfast Training Services Trial Blog

I’m working on Phase 2 of the Battersea Power Station Development Project (the actual power station bit). This post is related to Heath and safety on site. On the surface of it they appear incredibly H&S conscious, with a site flooded with orange jacketed traffic marshals and slinger-signallers and the logo “safety first, second nature” plastered everywhere. However, with a bit of digging below the surface (quite literally) they don’t seem to be quite as worried about the slightly less obvious but potentially incredibly dangerous situations. This lack of safety manifests itself in two ways; 1) constantly putting workers down deep excavations without any attempt at slope stabilization and 2) loading the top of steeply battered slopes. The second of these situations is the one I’ll go into detail on.

The situation shown below grabbed my attention on site because the slope batter looked to be at an angle that is too steep to support construction plant so close to the edge. I mentioned this to the supervisor and construction manager on site, who were not worried, believing that 45 degrees was an “ok” batter (I think that 45 deg is generous). Recalling that the thi dash/2 plus 45 rule goes out of the window when loaded, I was not sure about this, so checked it with some analysis on Geo5.

Some quick calculations on Geo5 using the information obtained from the Ground Investigation Report show an unstable slope.

Load (mass 23000kg) = 226 kN

Modelled as a distributed load over the area of the excavator.

The ground profile is not certain, due to the possible presence of a scour feature. I have taken the case as being in the Short term, as the excavation is only to be at this angle for a couple of days. So the worst case is with granular made ground from 0 to -8, and scour infill from -8 to -15.

After some more digging (i’m sure this pun has been done 100 times before on this blog but it’s worth getting it in), I also found the Risk Assessment/ Method Statement, which states that the safe batter is 30 degrees, and that stop blocks should be positioned a minimum of 1.1 m from the edge. I informed my supervisor, who is also the senior project manager in charge of ground works, who said that he would look into it. They have since carried out a deeper excavation on a steeper slope elsewhere.  🙂