Assessment of the current state of the underground machine hall being constructed at the Rogun hydroelectric station

Abstract

A meeting of the joint council of Ail-Union Planning, Surveying, and Scientific-Research Institute (Gidroproekt) on underground structures for evaluating the current state of the underground machine hall under construction at the Rogun hydroelectric station was held at the end of 1990. The reason for raising the question was the numerous negative features in the state of the workings of the machine hall (MH) observed both visually and by means of on-site measurements. The main points and results of analysis of the state of the MH and its causes examined by the joint council are given below. Description of the Object -Engineering-Geological Data, Main Designs, Predictive Evaluations. The object was already characterized earlier on pages of the journal [1, 2], and therefore only data about it needed for understanding the essence of the problem are presented below. The machine hall of the underground powerhouse of the Rogun hydrostation, designed by the Tashkent branch of Gidroproekt, is an underground working unique in size: span 21 m, height 70 m, length 220 m. Parallel to it, at a distance of 63 m at the axes, is an also rather large working -the transformer room (TR): span 19 m, height 37 m, length 182 m. In conformity with the design, in addition to functional transverse tunnel workings (busbar ducts, draft tubes), the rock mass enclosing the powerhouse is weakened by a number of auxiliary workings. The most significant with respect to effect on the stress-strain state of the MH are the access adit P-lb driven in the pillar between the workings of the MH and TR, parallel to them (Fig. 1), and the 12 x 20-m assembly chamber (AC) for assembling the shells of the penstocks of units 5 and 6. The set of workings of the powerhouse is located at a depth of more than 400 m in a single tectonic block bounded by active faults No. 1 (Ionakhsh) and No. 35. Within this block is also noted a lower tectonic disturbance, fault No. 70, extending at an angle of 45 ~ to the longitudinal axis of the MH.