Redesigning the San Roque Dam

by Daniel W. Osmun, P.E., Geotech. Engr.; Washington Group Int., Bellevue, WA,
Mark Rawlinson, P.E., Geotech. Engr.; Washington Group Int., Bellevue, WA,

Serial Information: Civil Engineering—ASCE, 2001, Vol. 71, Issue 4, Pg. 42-47,79

Document Type: Feature article


Engineers updated a 20-year-old design for the San Roque Dam in the Philippines to save time and money and improve the dam's ability to withstand earthquakes. The structure is a central-core, zoned-embankment dam with alluvial fill and rock-fill shells, along with 4 m wide transition, filter, and drain zones. Design improvements to the project included modifying the upstream cofferdam section, making use of excavated material that would otherwise have been spoil, and changing the dam's crest width. The filter, transition, and drain zones of the dam system were also modified to comply with current filter criteria and reduce the required quantity of processed materials. Because the site is in a seismically active area, the engineers conducted liquefaction studies on the design, and based on the results, set the minimum initial shell foundation excavation depth at 2 m for the majority of the site and at as much as 6 m in certain areas. In addition to the dam, the final project configuration includes a 345 MW hydroelectric power plant; a 430 m long concrete gated spillway with a total discharge capacity of 12,800 m�/s; a 1,200 m long power tunnel; and a 1,400 m long low-level outlet tunnel. The capacity of the reservoir impounded by the dam will be approximately 850 million m�.

Subject Headings: Seismic design | Power plants | Hydro power | Filters | Tunnels | Shell structures | Rockfill dams

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