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Soil out and Props in
We have had a very busy couple of days on Hope St, the big props are now in on the North side and the Acid Suphate Soil (ASS) is being rapidly extracted. We excavated 1368 cubic metres yesterday and over 600 cubic metres the day before. The site is starting to look better and progress is being made. Everyone is getting gradually less stressed.
It looks like the working platform will work and there is enough spare capacity in the props and wailer to cope with the lateral loads from the excavators (but we knew this anyway). I thought the photos might help future students on Exercise Cofferdam. Note the splices in the props, the ramp for outloading dirt and the excavator pairs working in tandem. .
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Doug, looks good. Are there any plans to paint the props a different colour? Do you have any monitoring schemes going on? I suspect as soon as you are at formation level there will be a push to blind and get reinforcement in. Any tower crane plans?
Good stuff! What is your role now other than the ASS monitor?
Doug
Some good pics and nice props. Are all the prop to waler connections welded?
Kind Regards
Neil
Hi, telstra isbuggering about with my internet connection so it’s been tough to reply. Damo – no monitoring other than surveying deformation of wall twice per week and I don’t understand why you would paint the props.
These are very dum props and have been welded together with a disastrous impact on the programme. Funnily enough the prop splices are bolted together and they went in so easily. Hmm makes you wonder if they had bolted it together I would have to work Easter.
My job on site is site engineer and I am responsible for everything from the props downwards. So I’m chasing the designer on finalising the ground anchor solutions it’s been problematic as the levels have have been conflicting with the slabs. Basicsihear you cry and you would be right. The Geotechs have not been great so I got the ground anchor job by calling their bluff.
So ground anchors to foundations (will be working on bearing capacity shortly). The foundations are pads laid on Phyllite (a cross between slate and schist). I handover to the other site engineer on the pads who is handling the RC for the basement. We aren’t welding the walings of the ground anchors and each section of secant pile wall will work independently of each other. I will send you a pic after Easter.
Hopefully that should leave me in charge of the PT concrete.
Hi Doug, All sounds very good. The maximum load the props take will probably be due to thermal loading from expansion with ends fixed. Therefore reducing the absorption/thermal properties of the props would be achieved by having lighter coloured props (white/yellow).
I think there was a case where some CHS props buckled because of this thermal loading. Perhaps you don’t see high temperature ranges… Also there might be some practical use in having lighter coloured props in that they are more obvious, therefore less likely to be hit.
I would be interested to know more about the ground anchors. My geometry has been fully tested trying to understand what area a pull out cone of resistance is generated using ground anchors. Especially when the cones overlap due to narrow spacing.
Hi Damo, the ground anchors are going in at 2.4 m centres and will be tested to 1.25 WL. I am currently awaiting the details of the load off tests but essentially they are tested up to 1.25 with elongation measurements at 0.1 WL 0.5 WL WL and 1.25 WL then back down to 0.1 WL. The lock off procedure then happens. Load off tests can be 24 hrs, 48, or 72 hrs to check for relaxation of steel cable.