The Kambarata 2 blast-fill dam, Kyrgyz Republic:blast event, geophysical monitoring and dam structure modelling
Tóm tắt
The blast- and earth-fill dam of the Kambarata 2 hydropower station is situated in the seismically active Central Tien Shan region of the Kyrgyz Republic. More than 70% of the dam volume was produced during a blast event on December 22, 2009. In 2010–2011, dam construction was completed after earth filling on top of the blasted material and installing concrete and clay screens together with bentonite grouts. A geophysical survey had been completed in 2012–2013, mainly to monitor the resistivities inside the dam. The geophysical survey completed on the Kambarata 2 dam site showed lower resistivity zones in the earth fill and relatively higher resistivities in the blast-fill material. Topographic, geophysical and piezometric inputs had been compiled within a 3D geomodel constructed with GOCAD software. This model was compared with the design structure of the dam in order to define the upper limits of the underlying alluvium, the deposited blast fill, earth fill and top gravel materials (represented by the dam surface). The central cross-section of this model was extrapolated over the full length of the main dam profile. On the basis of a calibrated hydrogeological model and known geomechanical properties of the materials, dam stability calculations were completed for different scenarios considering different reservoir levels and varying seismic conditions. Some of these scenarios indicated a critical vulnerability of the dam, e.g., if impacted by a horizontal seismic acceleration of Ah = 0.3 g and a vertical seismic acceleration Av = 0.15 g, with an estimated return period of 475 years. As a general conclusion, it was noted that this case study can be used as an example for surveys on much larger natural – landslide or moraine – dams. A series of geophysical methods (e.g., electrical and electro-magnetic techniques, seismic and microseismic measurements) can be applied to investigate even very deep dam structures. These methods have the advantage over classical direct prospecting techniques, such as drilling, of using equipment that is much lighter and thus more easily transportable and applicable in difficult terrain. Furthermore, they can provide continuous information over wider areas. This specific application to a blast-fill dam allows us to better outline the strengths and weaknesses of the exploration types and geomodels as a series of investigated parameters can be verified more easily than for natural dams.
Tài liệu tham khảo
Abdrakhmatov K, Havenith HB, Delvaux D, Jongmans D, Trefois P (2003) Probabilistic PGA and arias intensity maps of Kyrgyzstan (Central Asia). J Seismol Soc Jpn 7:203–220
Adushkin VV (2000) Explosive initiation of creative processes in nature. Fizika Goreniya i Vzryva 36(6):21–33
Adushkin VV (2011) Russian experience with blast-fill Dam construction. In: Evans SG (ed) Natural and artificial rockslide dams. Springer, Berlin, Heidelberg, Lecture Notes in Earth Sciences, pp 595–616
Bindi D, Abdrakhmatov KY, Parolai S, Mucciarelli M, Grunthal G, Ischuk A (2012) Seismic hazard assessment in central Asia: outcomes from a site approach. Soil Dyn Earth Eng 37:84–97
Danneels G, Bourdeau C, Torgoev I, Havenith HB (2008) Geophysical investigation and numerical modelling of unstable slopes: case-study of Kainama (Kyrgyzstan). Geophys J Int 175:17–34
Gerashnov GB, Zinevich YN, Shapovalov GI (1979) The Medeo mudflow-protection dam. Gidrotekhnicheskoe Stroitel’stvo 9:44–48
Hermanns RL, Folguera A, Penna I, Fauqué L, Niedermann S (2011) Landslide Dams in the Central Andes of Argentina (Northern Patagonia and the Argentine Northwest). In: Evans SG SG et al (eds) Natural and artificial rockslide dams. Springer, Berlin, Heidelberg, Lecture Notes in Earth Sciences, pp 147–176
Koltuk S, Fernández-Steeger TM (2014) Evaluation of seismic stability of coherent landslides: analytical approach versus FEM. In: ᅟ Grützner, C. et al (eds) 5th International INQUA meeting on paleoseismology. Active Tectonics and Archeoseismology, Busan, Korea, pp 135–140, doi:10.13140/2.1.1815.9364
Korchevsky VF, Kolichko AV, Strom A, Pernik LM, Abdrakhmatov KE (2011) Utilisation of data derived from large-scale experiments and study of natural blockages for blast-fill Dam design. In: Evans SG SG et al (eds) Natural and artificial rockslide dams. Springer, Berlin, Heidelberg, Lecture Notes in Earth Sciences, pp 617–637
Korjenkov AM, Bobrovskii A, Mamyrov EM (2010) Evidence for strong Paleoearthquakes along the Talas-Fergana Fault Near the Kök-Bel Pass, Kyrgyzstan. Geotectonics 44(3):262–270
Lamair L. (2012) Calcul de l’aléa sismique pour une région dans le Tien Shan Central, étude in situ et modélisation dynamique de la réponse sismique de sites de bassin de retenue. Master Thesis, University of Liege
Nedriga VP, Pokrovskii GI, Korchevsky VF, Petrov GN (1978) Full-scale investigations of seepage in an experimental blast-fill dam. Gidrotekhnicheskoe Stroitel’stvo 7:21–24
Petrov GN, Reifman LS, Khusankhodzhaev FZ (1975) Dam construction by blasting. Gidrotekhnicheskoe Stroitel’stvo 10:15–19
Torgoev A., Lamair L., Torgoev I., Havenith H.B. (2013) A Review of Recent Case Studies of Landslides Investigated in the Tien Shan Using Microseismic and Other Geophysical Methods. In: Ugai K et al. (eds) Earthquake-Induced Landslides, Springer-Verlag Berlin Heidelberg 285–294
Xu Y. (2014) Geologische 3D Modellierung und Analyse der Standsicherheit des Kambarata-2 Sprengschuttdammes. Master Thesis, RWTH Aachen University