A quick site update. Things were quiet with the sheet piling team at first, then suddenly everything ramped up.
The test results
The geotechnical engineer certified the platform for 250 kPa bearing capacity, and the nuclear density testing (an on-site test of how tightly the ground is compacted) backed that up.
The results were:
- 95% at one test location
- 97% at the other
The geotech report required more than 93% (measured against the material's maximum dry density, the tightest it can be packed in a lab test), so we comfortably met it.
Heavy rain, and a new certificate
We finished the testing last week. Then we had four to five days of serious rain that flooded the site. The ground was still extremely hard, but water softens compacted fill and can wash out the fine material, so after a rain event the engineer has to reissue the certificate to confirm the platform is still good.
Recertification and better drainage
The geotechnical engineer came back this morning and recertified the platform. The sheet piling company needs that certificate before they can set up on site.
We also brought in two truckloads of road base and built a gentle hump down the middle, so water runs off to the sides. We installed sump points along the edges as well (you can't fully see them yet).
To pump the water out, we used:
- a bucket with a hole in the bottom
- a sump pump with layflat pipe and a few joiners
- a short pipe into the low point
We set up one pump on the side first, then another at a low spot in the centre.
Once the gravel was down, we brought the 14-tonne roller back in and recompacted the platform.
The trade-off, and why we moved fast
Because the ground underneath was still wet, the new road base sits as a separate layer on a damp base instead of bonding into it (a lamination layer). It's not ideal, but the contractor asked for it, so we did it and had the platform reinspected. The perfect approach would be to wait about two weeks for everything to dry, but we don't have that luxury, and we don't want to pay the contractor remobilisation costs to reschedule their crew and machinery.
Once the 40-tonne rig starts moving around, any loose layers can get damaged, so time matters.
Sheet piling setup
The crew are rigging up the equipment now. They've taken possession of the site, so we're staying out of their way. They'll finish setting up this afternoon.
Vibration monitoring
The geotech team was also back today to install and start the vibration monitoring, with three sensor points around the site.
We've also marked the grid lines and where the external walls will sit (the blue lines), and given the crew the height for the tops of the sheet piles so we don't need to cut them off later.
The monitoring system took about two days to set up. Huge thanks to Bruno at Convergence Instruments in Canada. The instrument is excellent and very affordable: the subscription is about $185 a year, and the data streams live.
The devices connect through a Ubiquiti router, and right now they're the only devices on that network.
PacGeo's vibration monitoring covers all three points, including the fence area, and the geotech team gets an alert if vibration goes over the limit. We also have our own real-time monitoring running on site.
What's next
That's the last five days. I'll share another update once they start pre-drilling.
