Technical diagnostics of hydraulic structures

Abstract

Technical diagnostics as a method of diagnosing the condition of engineering systems was created in connection wlth the increase of requirements imposed on the safety, no-failure operation, and service llfe of complex and costly engineering systems. Technical diagnostics establishes and studies the features characterizing the condition of engineering systems for predicting and revealing deviations beyond the permissible limits; it also develops methods and means of checking the condition of these systems for the purpose of timely prevention of disturbance of their normal operating regime. In certain engineering fields (instrument making and machine construction) technical diagnostics and prediction of the reliability of engineering systems have reached a hig~ level of development. Hydraulic structures represent complex engineering constructions which have a considerable effect on the formation of the economic and cultural appearance of entire regions and transform their natural conditions. At present, in connection with the increase in the numbe~ and size of hydraulic structures and economic development of regions located in the zone of influence of large hydropower stations, the problem of the timely detection of possible deviations of hydraulic structures from normal conditions is acquiring special urgency, since their failures are associated with large material losses and death of people, and the largest failures have the character of a national disaster. The problem of using principles of technical diagnostics for evaluating the state of hydraulic structures, exemplified by earth d~ms, is examined in this article. Works in this area were conducted by the Department of Hydraulic Structures of the V. V. Kuibyshev Moscow Civil Engineering Institute (MISI) Jointly with the All-Un/on Power Engineering Industrial Association (Soyuztekh~nergo) in scientific and technical collaboration with the Department of Hydraulic Engineering of the Budapest Engineering University. Hydraulic structures are exposed to a considerable number of external loads (water pressure, atmospheric, seismic, and hydrodynamic loads, loads from moving vehicles, etc.) and internal loads (pore pressure, thermal stresses, seepage forces, etc.) differing in character and force and varying in time. The technical condition of hydraulic structures changes under the effect of loads and natural factors. In this case the structure or structural component can be in one of three conditions: good (and operable), operable (but faulty), and inoperable (faulty). An event in which the object becomes faulty, i.e., ceases to meet at least one of the standard technical requirements, is called a malfunction. An event after the occurrence of which the object becomes inoperable, i.e., does not meet at least one of the functional requirements, is called a failure. The following types of failures are distinguished according to the extent of the losses caused by failures on dams [i]. ~f the failure had a partial character and only expenses for repair were its consequence, then such a failure is called an incident. Destruction of portions of the revetment of the dam crest and stormwater and drainage ditches should be included among such failures. If elimination of the failure was associated not only with expenses for repair but also with a decrease of the operating indices of the structure (decrease of head or discharge of water) during the repair period, then such a failure is called an accident. Accidents on earth dams include considerable destruction of the revetment slabs of the upstresm slope, formation of through cracks in cutoffs, and sliding of the dam slopes. In the case when the accident leads to destruction of the hydraulic structure with damages to other structures, flooding of inhabited territories, and human victims, it should be regarded as a catastrophe, And, finally, if the accident had an effect on the llfe of an entire region or country, it should be defined as a national disaster.