(1) The Tianshengqiao hydropower station, built in the1980s, includes three diversion tunnels, dia.10.4m, length 9.8km, which were constructed in developed karst.To speed up excavation, two second-hand TBMs, dia.10.8m, were imported from abroad. Because of the presence of karst debris and underground rivers, construction proceeded slowly and was finished behind schedule.
(2) Gansu Yindaruqin diversion project, built in the early 1990s. The 30A tunnel, 11. 6km long and 5.5m in dia., is one of the longest tunnels in the project, which was built by the CMC company. The use of a double shielded TBM enabled the tunnel to be completed in 13. 5 months. With a best daily advance of 65.5m and a best monthly advance of 1300m, construction aroused interest in using TBMs.
(3) The Shanxi Wanjiazhai Yellow River diversion project now under way consists of the main, south and north sections, which include192km long tunnels. The longest, the No.7 tunnel, is approximately 43km long. It was excavated by TBM and finished in late 1999. Construction of the tunnels in the main section and south section is nearly finished.
The underground powerhouse for the Liujiaxia hydropower station, built in the 1960s, is 24.5m wide and 62. 5m high. In the 1980s and 1990s, several underground powerhouses were built. Hydropower stations currently under construction include the Dayaoshan and the Xiaolangdi power stations; in design are the Longtang, Xiluodu and Xiaowang power stations. In the Xiluodu power station, one of the largest underground powerhouses in the world will be built, at 277m long, 30m wide and 75m high. Considerable research has been carried out in the field of geological surveys; classification and stability analyses of surrounding rock; evaluation of mountain stability; excavation and support techniques; measures against karst and rock blast or other unfavourable geology. Much experience has been accumulated in engineering practice for pumped storage construction.
