HYDRO POWER CAVERNS | TECHNICAL


In Figure 4 a ratio of intact rock compressive strength and maximum cavern contour stress is presented as a rough indication of local collapse safety of the designed section. Extremely low values in the range of “two” require intense monitoring. Medium values in the range of “five” are desirable. Larger values up to “14” are no design criteria but coinciding. For illustration purposes six metamorphic host rock formations are summarized either with calcareous or clastic sediments Cover height above roof when evaluating sedimentary


and magmatic formations in China shows that a larger cavern roof overburden is more acceptable for magmatic rocks than for bedded formations. The overburden height above the cavern roof is only


reported for 25 cases, along with rock formation type, and it appears that very high cover stress is more likely to be acceptable with magmatic rocks. Such information on some older conventional and pumped storage plants has not been made available. In Figure 6 cavern rock mass failure modes are


distinguished for calcareous and clastic sediments, effusive and intrusive magmatic rocks, and 10 other/ unknown rock formations. Metamorphic rock sites may be evenly distributed to calcareous and clastic sediment-based metamorphic. The remaining unknown rock formations may be possibly be magmatic rocks. An investigation of 10 and 8 calcareous and clastic sedimentary host rocks, 10 and 8 effusive and intrusive


magmatic host rocks, and ten other host rock case histories in China was carried out. A total of 90 failure modes can be summed up in


four formation groups and are roughly ~50% structural modes, ~30% other site response to excavation, and ~20% design/construction-related modes: the first group prevails for bedded rocks, the second group prevails for other rocks, and the third group prevails for magmatic rocks. In previous editions of the International Water Power &


Dam Construction Yearbook mitigations to avoid potential failures reported in China have been discussed in length, a summary of which follows: 1 Immediate support reinforcement 2 Design/modelling improvement 3 Monitoring system reinforcement 4 Risk analysis precedent application


ACKNOWLEDGEMENT The compilation of pumped storage caverns in China was carried out by Yijun Zhu of Fichtner’s Hydropower Department, in Stuttgart, Germany. The data may be incorrect due to late design changes.


This report was previously published in T&T’s sister title International Water Power & Dam Construction’s 2023 Yearbook and is republished with kind permission


REFERENCES: 1


2 3


Barton, N et al, ‘Engineering classification of rock masses for tunnel support’, Rock Mechanics, Vol. 6, No. 4, pp189-236, 1974. Bieniawski, Z T, ‘Engineering rock mass classification in mining and tunneling’, Wiley & Sons, New York, US, 1989.


Broch, E, ‘Why did the hydropower industry go underground?’, Underground Space Use Analysis of the Past, Erdem & Solak (Eds), 2005.


4 Cooke, J B & Strassburger, A G, ‘Bibliography: Underground hydroelectric power plants’, Journal of the Power Division, ASCE, PO4, pp1350/1-36, 1957.


5 6 7


8


Finzi, D et al, ‘Underground power stations in Italy’, Proceedings, ASCE, Power Division, No. 12, pp63-99, 1959. Hee, Soon Shin, ‘Use of underground space in Korea’, Tunnels & Tunnelling, pp37-40, 2011.


Hendron, A & Fernandez, G, ‘Dynamic and static design considerations for underground chambers’, (Howard, T R (Ed.)), Seismic design of embankments and caverns, ASCE Symp. Phil., pp157-198, 1983.


Hibino, S & Motojima, M, ‘Behaviour of rocks around large caverns during excavation’, Proceedings, 5th Int. Congr. ISRM, pp496-507, 1983, also in: Comprehensive Rock Engineering, Hudson, J (Ed.) Vol. 4, Pergamon, 1993.


9 Hoek, E & Brown, E T, ‘Underground excavations in rock’, Institute of Mining & Metallurgy, London, UK, 1980. 10 Hoek, E & Marinos, P, ‘Predicting squeeze’, Tunnels & Tunnelling, Vol. 11 & 12, pp45-51 & pp33-36, 2000. 11 Hudson, J & Feng, X T, ‘Rock failure mechanism’, Mining Sciences, Vol. 47, Issue 6, pp877-888, 2010. 12 Hudson, J & Feng, X T, ‘Rock engineering risk’, Technology & Engineering, ISRM- Book, 2015. 13 Hveding, V, ‘Hydropower development in Norway’, Vol. 1, Norwegian Institute of Technology, 1992. 14 Lawton, F L, ‘Underground hydroelectric power stations’, Engineering Journal, pp33-51, 1959. 15 Barbosa Texeira, F et al, ‘EDP’s hydroelectric construction programme in Portugal’, Hydropower & Dams, V5, pp64- 69, 2014. 16 The Swedish Power Association & The Swedish State Power Board, Angelin, Stig et al, ‘Hydropower in Sweden’, 1981. 17 Tokyo Electric Power Co, ‘History of underground power stations’, Rock Mechanics in Japan, Japanese Comm. for ISRM, Vol. 6, pp99-10, 1991.


18 Tveitan, I & Buen, B, ‘Compact design of caverns for hydropower stations in Norway’, pp11-37, 1982. 19 Yevdjevich, V M, ‘Underground power plants in Yugoslavia’, Journal of the Power Division, ASCE, PO 3, pp81-92, 1961. 20 Yufin, S et al, ‘Aftermath of the USSR’, International Water Power & Dam Construction, pp36-38, 1999.


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