ARM
The Problem
A mass poured retaining wall had failed in the horizontal position due to over overloading and poor construction. The top of the retaining wall was sliding off its base towards an open highway. In the event of failure a carriageway would have been closed causing delays and potential safety issues to the public. The wall could have been reactively repaired causing non planned delays to traffic and an increased repair unit rate. A remote monitoring solution was chosen to manage the risk and review the decay in the interim while a planned repair was designed and commissioned.
The Solution
The width of the wall was measured and a piston gauge was installed to monitor the overhang of the failed wall. Trigger levels were set at 30, 40 and 45% overhang, this was assuming at 50% overhang the top of the wall would fail. The trigger levels were given a RAG status with alerts set at each interval:
R.A.G. Status
- 30% Green Text / Email to asset manager - Keep monitoring
- 40% Amber Text / Email to asset manager and senior asset manager - Site visit and escalate repair
- 45% Red Text / Email to asset manager and senior asset manager - Site visit to assess the risk and start emergency repair.
The Outcome
The wall was monitored over 6 weeks. During this time the wall moved 40% setting off the amber status. A repair was designed in the 6 weeks and installed. Using remote monitoring saved 50% of the cost where as a reactive repair would have cost double the planned repair. The safety risk was managed during this time and a greater understanding of this type of failure was gained by the client.
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