The Failure Rate of Low-Head Ground Dams of Dangerous and Unsatisfactory Safety Level
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Vol. 54, No. 3, September, 2020
THE FAILURE RATE OF LOW-HEAD GROUND DAMS OF DANGEROUS AND UNSATISFACTORY SAFETY LEVEL D. V. Kozlov,1 O. S. Simonovich,2 and V. L. Snezhko3 Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 4, April 2020, pp. 18 – 24.
The results of an expert survey of 1024 ground dams of class IV located in the Moscow Region were processed by the methods of the system theory of reliability. Exponential curves for unsatisfactory and dangerous safety levels retained by structures are constructed. The period during which the dam safety level will decrease and the number of dams, the safety level of which will decrease by an order of magnitude, are estimated. Using Markov analysis, a probabilistic forecast of the dam’s compliance with each safety level over time was made. A method for calculating the recovery frequency of the safety level of low-head ground dams is proposed. Keywords: low-head hydraulic structures; ground dams; safety level; probabilistic forecast.
According to the current regulatory documents, ground dams of class IV (low-danger hydraulic structures) are the structures up to 15 m high, erected on sandy, coarse-clastic or clayey soils, or up to 20 m high, erected on rocky soils. For retaining hydraulic structures of meliorative hydraulic facilities of class IV, the reservoir volume should not exceed 50 million m. When the water retaining structures are located within the populated territories, the maximum design head on the dam should not exceed 8 m. An emergency, appearing as a result of an accident at such dams, spreads within the territory of one economic entity [1]. According to official data, at the beginning of 2018, the total number of hydraulic structure (HS) complexes included in the Rostekhnadzor database was 25,457, of which 23,382 HS (92%) were of class IV. The share of HS of the water industry was 82%, 13% of HS were considered ownerless, 3% of HS complexes were used for storing liquid industrial waste and 2% belonged to the fuel and energy complex. The HS safety level was distributed as follows: normal — 39.4% of complexes, reduced — 43.4%, unsatisfactory — 12.5%, dangerous — 4.7%. During inspections of structures on the threshold of the flood waters passage, Rostekhnadzor revealed a number of characteristic violations, namely: unsatisfactory technical condition of structures, failure to perform routine and major repairs, absence of operating organizations
or insufficient qualification of operating personnel [2]. In the report of Rostekhnadzor, it was noted that the cause of accidents at the hydraulic facilities in most cases was the destruction of the dam made of ground materials. The situation with low-head HS in Russia is also typical for a number of post-Soviet countries. For example, most of the hydraulic facilities in Tajikistan were built more than 30 years ago. Over the past 15 years, not only reconstruction or repairs, but also current surveys of hydraulic structures have not been carried out on them [3]. On the territory of Kazakhstan, 41% of the HS does n
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