Dam Spatial Temperature Deformations Model Development Based on GNSS Data

The Dnipro hydroelectric power plant (HPP) is the oldest hydroelectric power station in Ukraine built almost 100 years ago. The HPP dam was heavily damaged during World War II. Long-term operation of the dam requires the monitoring of spatial movements and its deformation processes. The purpose of the research is to develop a spatial displacement monitoring model of the global navigation satellite system (GNSS) dams at the Dnipro HPP. The study is based on the data received both from an automated monitoring system and changes in ambient temperature from 2017 to 2020. The input data are presented by time series of changes in GNSS coordinates. They are based on the results of around-the-clock measurements obtained at the points of the Dnipro HPP dam during 2017–2020. The information also includes the results of measuring the average daily air temperature at the Dnipro HPP. A specially developed software product analyzed the time series of GNSS measurements to determine seasonal spatial displacements. It also revealed their connection with seasonal changes in air temperature. As a result we managed to find the decisive influence of ambient temperature on the seasonal spatial displacements of dams, though significant changes in the reservoir water level were absent. The crest of the dam shifted toward the reservoir and rose in the first 6 months. In the second half year, the horizontal displacements were directed toward the lower reaches, and vertical subsidence took place. The velocity distribution of spatial displacements along the dam’s crest was uneven in time. The magnitude of extreme displacements and the epoch of their representation depended on the dam’s design and technical parameters. They were different for each dam. The study helped to develop an average statistical model that revealed the dependence of the spatial displacements at the Dnipro HPP dam crest on the average integrated air temperature. The conducted research allows us to establish and predict the values of seasonal spatial deformations of the Dnipro HPP dam, as well as disclose the effect of air temperature. Deviations from the temperature deformation model might be considered as possible changes at certain points of the dam during either its operational period or technical defects obtained during its construction. Such deformations can cause cracks in the dam’s body and thus impact its stability. The pattern of the connection between the change of temperature and the displacements of GNSS points was revealed as a result of the study. This can be used for research on processing and analysis of monitoring data of other engineering constructions.

The paper presents the method of computation an average statistical model demonstrating the dependence of the dam spatial displacements on the average integrated air temperature. This method can become an addition to automated GNSS monitoring systems installed on hydroelectric dams. This makes it possible to identify problem areas in the structure deformation field that may be invisible from the outside. However, they can manifest as stresses, deformations and subsidence of reinforced concrete structures, the appearance of cracks, and water seepage. Timely detection of these anomalies enables to clarify the safety state of the concrete dam. The proposed technique can be integrated into automated GNSS monitoring systems of other large engineering structures (high-rise buildings, bridges, pipelines). This is especially relevant for engineering structures that are operated under the influence of seismic activity or located in areas of military operations where natural or human-made earth’s surface vibrations lead to the internal irreversible structure deformations. According to the forecasts, global warming and climate change can lead to an increase in the intensity and frequency of extreme weather conditions (hurricanes, floods, temperature changes). Therefore, we emphasize the importance of the automated GNSS monitoring of large engineering structures. Furthermore, modeling the influence of these factors on their deformation fields is absolutely relevant.