The ecological Alternative: Tunnel Excavation for the Cheves Hydroelectric Power Plant in Peru
In 2010, construction work began at the Cheves hydroelectric power plant that is located on the Huaura River approx. 130km north of Lima. When the plant is completed in 2015, it will add 168MW or 837GWh to the main electric grid via a 77km long transmission line. The underground construction portion of this project consists of approx. 19km of tunnels and a power house cavern with two turbines. The tunnel is manly excavated by drilling and blasting. Ground conditions in the project area vary greatly. The tunnels were driven through sedimentary, igneous and volcanic rocks as well as swelling clay and fault zones, which posed additional challenges for the participating companies. Furthermore, the high overburden of up to 1.2km resulted in stresses that exceeded the rock mass strength, causing rock bursts. Water inflows and rockbedded methane gas also made tunnel excavation difficult. Due to the difficult ground conditions, high quality and modern ground control solutions were provided for the Cheves Hydroelectric Power Plant project by DSI. Self-drilling DYWI® Drill Rock Bolts and Spiles were installed in combination with Lattice Girders to provide a safe underground environment during advancement and excavation. In total, DSI Peru supplied 4,038 4m long Ø R32 DYWI® Drill Hollow Bars, 1,917 3m long Ø R38 DYWI® Drill Hollow Bars, 300 4m long Ø R38 DYWI® Drill Hollow Bars and Lattice Girders for stabilizing the highly unstable zones. Furthermore, 921 Ø 22mm COMBI-BOLT Combination Rock Bolts in standard lengths of 2.4m were used for rock reinforcement in the hard rock areas. In addition, DSI Peru supplied DYWIDAG Cable Bolts and resin cartridges for rock stabilization. DSI Peru also supplied 7 mortar mixing pumps to the client. The project was registered as CDM (mechanism for environmentally friendly development) by the United Nations because it will balance the carbon dioxide driven energy mix in Peru by a more ecological alternative for generating energy. It is expected that the new hydroelectric power plant will reduce CO2 emissions by an estimated 394,000t per year.