Abstract
Numerical simulations have been performed to assess the stability of a large underground powerhouse in the Himalayas, using both finite element and distinct element approaches. Large convergences (around 250–300 mm) along the 45 m high wall of the Machine Hall have been measured by total station measurements during construction and up to 60 mm in the post construction and operational phase. Displacements are continuing at a reduced rate of about 3 to 6 mm per year. A large number of rock bolts have failed in the powerhouse and the shotcrete liner presents cracks and failure marks, thus questioning the long-term integrity and stability of the existing rock support system. The purpose of the numerical analysis was to back-calculate the prevailing rock mass conditions surrounding the machine hall, thereby gaining a better understanding of the mechanisms responsible for the instability in the cavern. The results from the analysis indicate that there was possibly an underestimation of the rock support requirements needed for the cavern, coupled with a not so good installation (incomplete grouting of the bolts). Both the length and the capacity of the rock bolts were underestimated presumably due to the existence of a high stress regime in the area, which may not have been taken into consideration in the design of rock support. The effect of a possible earthquake, frequent in this area, has also been studied and proves to induce a significant increase of the displacements and the support failure.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Bhasin, R. and Høeg, K. (1997). “Numerical modelling of block size effects and influence of joint properties in multiply jointed rock.” Tunnelling and Underground Space Technology, Vol. 22, No. 3, pp. 407–415, DOI: 10.1016/S0886-7798(97)00030-8}.
Bhasin, R. and HØeg, K. (1998). “Parametric study for a large cavern in jointed rock using a distinct element model (UDEC-BB).” Int. J. Rock Mech. Min. Sci., Vol. 35, No. 1, pp. 17–29, DOI: 10.1016/S0148-9062(97)00312-4.
Bhasin, R. and Kaynia, A. M. (2004). “Static and dynamic simulation of a 700-m high rock slope in western Norway.” Engineering Geology, Vol. 71, pp. 213–226, DOI: 10.1016/S0013-7952(03)00135-2.
Bhasin, R., Pabst, T., and Olsson, R. (2013). “Numerical study of the stability of a large hydropower machine hall in the Himalayas under dynamic loading.” Proceedings of the 7th Nordic Grouting Symposium and 2nd Nordic Rock Mechanics Symposium, 13-14 November, Gothenburg, Sweden.
Chowdhry, A. K. (2007). “Crown failure in the machine hall cavern of Tala Hydroelectric Project, Bhutan Himalaya.” Proceedings of the International Workshop on Experiences Gained in Design and Construction of Tala Hydroelectric Project Bhutan, June 14-15, New Dehli, pp. 93–105.
Gupta, M., Chitra, R., and Dhawan, A. K. (2007). “Stability analysis of power house cavern of Tala H.E. project.” Proceedings of Int. Workshop on Experiences Gained in Design and Construction of Tala Hydroelectric Project Bhutan, June 14-15, New Delhi, pp. 321–327.
Hashash, Y. M. A., Hook, J. J., Schmidt, B., and Yao, J. I. C. (2001). “Seismic design and analysis of underground structures.” Tunnelling and Underground Space Technology, Vol. 16, No. 4, pp. 247–293, DOI: 10.1016/S0886-7798(01)00051-7.
Khazanchi, R. N., Tshering, S., and Tamang, B. (2004). “Hydropower development in Bhutan — A perspective.” Proceedings of Hydro Vision 2004, Montreal, Canada.
Kveldsvik, V., GrØneng, G., Lato, M. J., Wiig Sagen, H., and Martens, B. (2011). “The largest underground railway station in Europe — Site investigations, excavation methods and design of rock support.” Proceedings of Fjellsprengningskonferansen, No. 24, Oslo.
Li, C. C. (2010). “A new energy-absorbing bolt for rock support in high stress rock masses.” Int. J. Rock Mech. Min. Sci., Vol. 47, pp. 396–404, DOI: 10.1016/j.ijrmms.2010.01.005.
Naik, S. R., Nair, R., Sudhakar, K., and Nawani, P. C. (2011a). Final report on back analysis using numerical modeling of powerhouse complex of tala hydroelectric project, Bhutan, Report No. NM1003C.
Naik, S. R., Sudhakar, K., and Nair, R. (2011b). Final report on instrumentation, monitoring and data analysis at power complex, tala hydro power plant, Bhutan, Report No. NM1001C/02.
Palmström, A. (1995). “RMi- a system for characterizing rock mass strength for use in rock engineering.” Journal of Rock Mechanics and Tunnelling Technology, Vol. 1, No. 2, pp. 69–108.
Sengupta, S., Subrahmanyam, D. S., Joseph, D., and Sinha, R. K. (2007). “The role of National Institute of Rock Mechanics in in situ geotechnical investigations (1979 to 2002) at Tala hydroelectric project Bhutan.” Proceedings of Int. Workshop on Experiences Gained in Design and Construction of Tala Hydroelectric Project Bhutan, June 14-15, New Dehli, pp. 150–172.
Sharma, B. N., Singh, R., Goyal, D. P., and Khanzanchi, R. N. (2004). “Experience of Dywidag rock bolts in machine hall cavern at Tala project.” Journal of New Building Materials & Construction World, Vol. 9, No. 11, pp. 68–74.
Singh, R. (2005). Instrumentation at Tala hydroelectric project in Bhutan, Training Course on Geotechnical Instrumentation for River Valley Projects, New Delhi, February 28 — March 9, pp. 42–66.
Singh, R., Chowdhry, A. K., Sharma, R. N., Goyal, D. P., and Khazanchi, R. N. (2002). “Wall support system for powerhouse cavern of Tala Hydroelectric Project in Bhutan Himalayas.” Proceedings of Indian Rock Conference, 28-29 Nov, New Delhi, pp. 132–142.
Singh, R. and Goyal, D. P. (2005). Compendium of published papers on 1020 MW Tala hydroelectric project, Tala Hydroelectric Project Authority Gedu, Bhutan.
Singh, R. and Sthapak, A. K. (2007). Experiences gained in design and construction of Tala hydroelectric project Bhutan, International Workshop, June 14-15, New Dehli.
Sripad Rao, R. V., Gupta, R. N., Sudhakar, K., Raju, G. D., Singh, R., and Sharma, B. N. (2003). “Instrumentation to study rock mass behaviour of machine hall cavern at Tala hydroelectric project, Bhutan.” Proceedings of the International Conference on Accelerated Construction of Hydropower Projects, Gedu, Bhutan, October 15-17, Vol. 1, pp. VII 1–12.
Venugopala Rao, R., Alagh, P.K., Chowdhry, A. K., Sharma, B. N., and Theraja, D. V. (2003a). “Evaluation of rock bolt failure mechanism in Tala HE project, Bhutan.” Proceedings of the International Conference on Accelerated Construction of Hydropower Projects, Gedu, Bhutan, October 15-17, Vol. II, pp. V 30–37.
Venugopala Rao, R., Gupta, R. N., Raju, G. D., Chowdhry, A. K., Chug, I. K., and Alagh, P. K. (2003b). “Performance of rigid support system in cross openings around major caverns.” Proceedings of the International Conference on Accelerated Construction of Hydropower Projects, Gedu, Bhutan, October 15-17, Vol. II, pp. V 38–46.
Venugopala Rao, R., Raju, G. D., and Chowdhry, A. K. (2007). “Stress analysis of desilting chamber complex of Tala Hydroelectric Project.” Proceedings of the International Workshop on Experiences Gained in Design and Construction of Tala Hydroelectric Project Bhutan, June 14-15, New Dehli, pp. 283–297.
WAPCOS (2011). Draft report of DGPC, tala hydroelectric project, on additional rock bolt installation for strengthening of power house caverns.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Bhasin, R., Pabst, T. Finite element and distinct element analysis of the stability of a large underground hydropower machine hall in the Himalayas. KSCE J Civ Eng 19, 725–732 (2015). https://doi.org/10.1007/s12205-013-1351-4
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12205-013-1351-4