15 December 2010
Why you need to check the bearing capacity – the Waikato crane accident video
Posted by Dave Petley
This accident occurred last week in Waikato, near to Auckland in New Zealand. The crane is a 200 tonne Terex All Terrain machine. It was lifting one of the sections of a new foot and cycle bridge into place when the embankment upon which one of the crane footings was located slipped under the load, sending the crane toppling over:
http://www.youtube.com/watch?v=xz71eVreMDc
A series of photos before and after are available here. This one in particular shows the slip after the event:
The morphology of the slide is interesting. Note the extensional cracks running across the surface. This is quite unusual, probably resulting from the rather unusual failure mode of essentially point loading at the top of the slope. Second, the materials look weak and wet, such that I am surprised that the footing was located so close to the crest of the slope. Locating the footings in such situations is always difficult though. Finally, the bridge section was swinging, which will have applied a dynamic load.
The driver was not seriously hurt. His final actions as the crane tipped of turning the crane so that he facing upwards were well-judged.
Comments and thoughts?
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
From the remaining gravel fill it does not give the impression that it was compacted properly. Also, I would think it they had reinforced at least the lower layers of the fill with grid or textile it may not have failed the underlying, saturated, fine grained soils.
Not sure about New Zealand but the US has just amended the OSHA standards to include, among many other things, accountability for site conditions. Details!
Yes, it looks like they just dumped a bunch of gravel on the river bank and set their outrigger pads on it. Talk about hasty !
Not a surprising result too !
It should of had interlocking I-beams pile driven down in a semi-circle, then gravel dumped and compacted by something heavy being driven over it or thumped by the pile driver awhile.
That would have likely held the crane’s weight, tho the crane’s engine vibration likely was the ‘triggering’ effect that caused the initial liquifaction leading to the soil slippage resulting in the tipover.
That didn’t happen in Waikato.. It was down the road from my personal residence, over the creek next to the road bridge on Triangle Rd, in Massey Auckland, New Zealand. Not Waikato. They were trying to put a cyclist’s bridge over the creek.
Being in the U S I can only speculate on the site conditions, but having done construction on or at the waters edge using mostly cranes, I would guess by viewing the after photo which showes an elevation difference between the waters edge and the vegitation along the non moving stream that ther is tidel infulance on the water level which would keep the bank saturated.A larger crane setting further back from the stream would probably have done the trick. Viewing the vidio just befor the crane topples you can see a verticle break in the fill which indicates to me that the fill was cut out with an excavator and probably a deeper uncompacted fill put back possibly worsening the situation.
In the US the crane operator can always say no, but the dynamics of the forman directing the operation and meeting scedules some times takes over.
This was a two crane pick is more than twice as difficult to cordinate. The load should have been set in the stream the moment the bank started give away, but the forman was still more concerned about the load than the men and the crane or oblivious to what was going to happen. Bring the load in next to the outrigger and attempting to swing the load up the bank required the crane to have the boom almost verticle. With the load center moved in closer to the center pin and the crane way off level the counter weight took control ayay from the operator, swinging the crane rapidly and tipping it c over. Accidents always happen fast. RT
Well he may have saved the crane if he just set the load down in the creek and left the crane where it was, yes it may have slid but I doubt it would have fell over. The operator learned about backward stability of a crane.
I agree with Lars, should have installed a revetment for stability under the outriggers. The fracture lines indicate the liquefaction that occurred.
I notice also that these two rigs are operating under high voltage transmission lines; what is the vertical clearance?
There are a number of issues here that wouldn’t fly on the projects I’ve been involved with.
the crane operator did a good job of booming up and landing the load to reduce the boom load and probably save the guys on the pier, But he had absolutely nothing to do with swinging the house in the right direction, it was all gravity taking the counterweight for a ride and swinging the house. What a terrible feeling that must have been for the operator (not ot mention the crane owner).
I have been in the Industry over thirty years as an operator and Trainer / Assessor and I would never have let this lift go ahead if it was done during an assessment or simulated training. The ground was unstable, The Crane was set up to close taking in account an acceptable level of gradient. The “Dogman” failed to notice at least five warning signs that the shit was about to hit the fan. Not sure if compact tests were done prior to the configuration of the crane. Every thing about this lift is wrong and its lucky someone wasnt killed or seriously injured. To answer a post before about,,,”does NZ have standards??? to be perfectly honest, we have a Code of practice for Cranes and a Code of Practice for Load Lift Rigging. Both of these codes are NOT compulsory in New Zealand and it is because of this that we are the laughing stock of the international crane community. How do I know this? Because I run the Philippines Crane and Construction centre where we send operators to Dubai and other places and all are assessed to British Standards, a Country where you actually have to hold a ticket to operate a Crane.
oh any feed back or intelligent comments email me at [email protected]
http://www.cranetraining.co.nz
http://www.cranetraining.com.ph