Makes you wish you had volunteered for submarines!
I have just returned from an awesome week away with the family in Noosa. However, today reality has hit hard.
We have rapidly built our way out of the basement and have reached basement level 2 just underneath the props. Now that the permanent structure was in at B2 – B6, it was time to start removing the props that were used to support the basement. The culmination of nearly 3 months planning was coming to fruition.
Old aerial photo of the site (highlighted area props to be removed, North is up).
I started my checklist:
- Cylinder crush results above 25 MPa – check
- Slab over 3 days old-check
- Exclusion zones in place – check
- Construction Union on side – check
- Actions and loads – check
- Risk assessment complete – check
- Access way in place – check
- Agreement from designers – check
- Confirmation that slab is in place from the structural site engineer – check
- Risk/Issue registers reviewed – check
- Final walk around and confirmation…
SW Corner – A big hole where a slab should be
Someone hadn’t built the stairs! (North is left)
Things started to unravel pretty quickly when I discovered that the stair penetration had grown from 4 x 2.5 m to 7.8 x 10 m. I attempted to find out what capacity I had in the slab/secant pile wall/walers in order to avoid a 5 day delay but to no avail. Despite pressure from the management, I called off the demolition. This will now result in $150,000 in lost time and considerable extra work. I now need to supervise the closing of this penetration and the adjustment of the programme.
Morals of the story
- Trust but verify! If I hadn’t checked up on other people this could have gone badly wrong.
- If there is a corner to be cut, people will cut it.
- Don’t assume that just because someone has been doing a job longer than you that they know what they are doing.
- Integrity, the pressure to crack on was extreme but, if in doubt don’t.
Where I would have rather been today…
Great Sandy National Park- The sand cliffs behind were formed during the last ice age from blown sand dunes and are a great place to study slope stability of coarse grained soils. The rusty colour comes from the oxidation of the Iron in the sand (Can I claim this trip on JPA now?)
Holdfast Training Services Trial Blog 
Doug
Welcome back to reality. If you had not been there would they have just removed the props. I suppose the issue is the much larger hole and so a weaker permanent prop?
Kind regards.
Neil
Hi Neil,
Reality sucks! Unfortunately I think they would have removed the struts. I kept on being asked what will happen if we rip it out? Well buckled waler, damaged access way, cracked retaining wall and cracked slab.
I think there is a real possibility that they would have ripped the prop out.
The initial concern from the designer was, as you say, a weaker prop but this was partially resolved. The key concern is that there is no restraint to the wall in the peno. The wall designers were happy with the soil arching over 2 hard piles but the hole has grown to 3x the width anticipated. Effectively they wanted the wall to cantilever from 8.2m. I can get probably 6.5 m from it but no more.
Best wishes,
Doug