Atacama Desert, Chile
Minera Escondida, Organic Growth Project 1, Tunnel 4
Expansion of the Minera Escondida copper mine included constructing a corrugated steel structural plate arch tunnel. The tunnel acts as a buried bridge to carry a haul road over the mine’s conveyor system. During construction of the embankment, the tunnel experienced differential settlement along the length and across the span. On behalf of the contractor, SGH evaluated distress in the tunnel structure and its reinforced concrete footings, and designed repairs.
SGH visited the site to inspect the tunnel and its footings, assess the tunnel shape, make observations at test-pits, and evaluate soil samples to determine the as-constructed condition. We used the collected information to perform a structural evaluation, including the following:
- Developing and analyzing two-dimensional, finite element models of the corrugated steel structure to match measured settlement
- Evaluating the effects of settlement on the reinforced concrete footings
- Analyzing the structure to determine if it can accommodate additional differential settlement
SGH concluded concrete footings and certain tunnel sections would be adequate to resist the intended heavy haul loads and effects of settlement. We recommended a structural liner for remaining tunnel sections and repairs to locally damaged rings. To help the contractor avoid these issues during the construction of future tunnels at the mine, we recommended a process for pre-loading the foundation soil.