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Some demolition gratification!
So a few weeks ago we had a drone on site to film the progress so far. This is a client directed activity, but something we had to make allowance for on site.
You can probably guess that some of this may not be 100% as per the RAMS.
The tallest of the excavators, an HITACHI Ultra-high reach excavator, is the plant we are having issues with over the tunnels.
Points of interest:
0:12 – The majority of the buildings in this shot will eventually be demolished (except very top left)
0:23 – Ground dust suppression cannon
0:52 – Plant mounted dust suppression cannon
1:25 – Red hose feeding dust suppression cannon (these are quite exposed and often tracked by the plant)
1:44 – Some of the “off-site” works can be seen here, road upgrades and reallignment as part of the development
1:55 – The New Library can be seen here – another Carillion Project which helped them secure this project. (You can also see the Hyatt, the mirrored building, which Andy Bayley has a good story about)
2:10 – This highlights how constrained the site is and why the dust suppression is so important – there is a dedicated liaison manager who keeps all the stakeholders happy
2:35 – The white-roofed, red brick building is currently the site office – although this is going to be demolished
2:45 – The building on the left is the Birmingham Conservertoire (concerts and stuff) and is still in use – more steakholder management.
Paradise Circus, Birmingham
Welcome to Paradise
On the 22 February I started work with Carillion PLC on the Paradise Circus Demolition/Construction in Birmingham.
The development scheme involves the transformation of 17 acres at Paradise Circus in the heart of the city centre. The £500m development is being brought forward through the joint venture company, Paradise Circus Limited Partnership (PCLP), a partnership between Birmingham City Council (BCC) and BT Pension Scheme, managed by Hermes Real Estate with Argent as development manager. In addition to the developer other interested parties include Amey who maintain the A38 Queensway Tunnel on behalf of BCC.
The project is currently in the Phase 1; primarily demolition of the RC concrete structure of Library and office buildings. Phase 1 also includes some large bore piling, up to 1200mm and the construction of a podium deck car park. This will be the platform for future development (contracts that Carillion are highly competitive for at the moment, but have not been awarded). The future development aims to bring over 300,000 sq ft of grade “A” office space to Birmingham City Centre.
Area in blue includes the 17 acre redevolpment and road improvement scheme
Demolition of the main building, the reference library, is primarily being completed through use of a high-reach excavator. This plant weighs in excess of 1600kN with the potential to put a very large point load on the ground beneath.
I have been tasked with the monitoring of the A38 (Queensway bypass) that passes under the site through a combination “cut and cover” and bored tunnel. The majority of the tunnel has a precast pre-stressed inverted T-beam roof. These are infilled with concrete and laid edge to edge.
Demoliton zone – Red; A38 Queensway tunnel – Blue
There is a concern that the high-reach excavator is too heavy to use in proximity to the tunnel. To mitigate the risk of the plant load, the site has been divided in to zones 1-4. Zone 4 not requiring a specific RA for the tunnel, down to Zone 1 which needs a full RAMS and approval from the BCC Engineers. Zone 1 is above the tunnel or within a 45 degree angle from the base of the tunnel.
Trigger levels have been set by theoretical modelling of the tunnel. Remaining capacity of the T-beams is calculated and the Red trigger level is set around 80% of the ULS (evidence of this is assessment is elusive). Monitoring has been installed in the tunnel and the normal deflection pattern established (this is over a 2 week period, but I cannot seem to find any evidence or analysis of this). Interestingly – or not – the normal pattern of life seems to move the tunnel through twice the deflection that has been set as the Red trigger level. This has resulted in the Section manager and project director receiving upwards of 300 alerts last week alone (I haven’t received my work phone yet so I’m dodging that bullet at the moment). The tunnel hasn’t collapsed…yet.
A load test is being conducted on the inverted T-beams to test the theoretical model. Type 1 Aggregate is compacted in layers over the course of 4 days. The first three days, 2 layers are compacted with two layers of 150mm compacted on day 4. Each morning a materials technician from Environmental Services Group (ESG) carries out a Nuclear Density Test on the aggregate to ensure the sub-contractor has reached 90% compaction density.
The final layer of aggregate is currently being placed by the sub-contractor. The senior engineer and I are responsible for checking the levels of the beam – currently we have 0.5mm deflection throughout. This is done through a series of 3m rebar pins that have been set in concrete on the roof of the tunnel (as well as the automatic monitoring inside the tunnel).
I am still trying to get my head around the expected outcomes and controls that have been applied to this test. It seems to me that the trigger levels have been set too low and the equipment monitoring the deflection in the tunnels are not that accurate (influences such as temperature, traffic flow and pollution can impact the results).
I will add an update when the test is complete and we have the results interrogated.
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