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The CCS Hydropower Station in Ecuador is characterized by the axis of the diversion to power generation system up to 2 800 m long, the internal and external heads more than 600m, the large groundwater recharge, the developed steeply dipping broken zone and the densely caves criss-crossly arranged, all of these result in gushing water problems during construction and many key and difficult points in waterproof-drainage design. According to the sensitivity analysis of internal water leakage based on seepage field's analysis over various conditions by FLAC 3D, multi-factor instability analysis for wedges considering joints' and fractures' water pressure coupling of in-situ stress by 3DEC, combining with the high-pressure permeability characteristics analysis based on high water pressure tests results, features analysis of the safety monitoring data at the characteristic times after the water-filling test until recently, the research on key technologies for waterproof-drainage and also certification for control measures were finally put forward. Using water-permeable lining, combining with geomembrane, consolidation grouting, curtain grouting for the upstream high-head water diversion system, drainage hole curtain based on drainage gallery and system drainage holes for the downstream power generation system and so on, after all these permanent and temporary combination measures, the power station currently is running well, the safety monitoring data are not anomaly and have been converged for a long time, which certifies the rationality of the waterproof-drainage design for diversion to power generation system under the high internal and external water condition. [ABSTRACT FROM AUTHOR]

The underground powerhouse system of CCS hydropower station in Ecuador is characterized by large-span caverns and three directions short distance in space, which brings about complicated three directions thin pillar problems. The joints development and strike unfavorable in the caverns area, it is easy to form unstable wedge. Based on the European and American codes, using domestic and foreign engineering analogy method, two-dimensional and three-dimensional analysis methods, and based on the “NATM”, the design ideas of integrally using shotcrete with wire mesh and bolts, partially considering shotcrete with steel set and bolts for supporting, and the design concept of partial reinforcement for wedges on the basis of integral system support were finally put forward. This project had avoided the delayed construction period by large-scale pre-stressed anchors and cables. At present, the power station is running well, the safety monitoring data are not anomaly and have been converged for a long time, which certifies the rationality of the support structures for underground caverns. [ABSTRACT FROM AUTHOR]

The area of CCS Hydropower Station tailrace channel belongs to high earthquake degree area, where the geological condition is poor, overburden is deep, the elevation of bedrock surface varies greatly and the tailrace channel is very closely to the only major road of the power station, directly leading to the limitation of excavation range of tailrace channel and forming a stability issue for high and steep slope condition. This project included multiple difficult points and complex conditions, which was a typical case of slope design. In order to make sure safety, “multiple parameter truth value inversion analysis” was adopted to obtain geological parameter, designer put forward the combined supporting design idea of ground wall, pre-stress cable, top beam anti-slide pile, pre-stress rock bolt and grout bolt. This project guaranteed the road safety and avoided the delayed construction period by other road plan. At present, the power station is running well, the safety monitoring data are not anomaly and have been converged for a long time, which certifies the rationality of design idea and support plan for tailrace channel slope. [ABSTRACT FROM AUTHOR]