# Impact of Arch Dam Cracking on Monitoring Data
## 5 Conclusions  
A total of 35 different cases were simulated with a finite element model of an arch dam based on 28 different cracks. It was determined how they affect the displacement recordings at 15 internal monitoring devices and 6 measurement points at the crest. Twelve of the cracks studied have opened, and a detailed analysis of these cracks leads to significant conclusions, supported by concrete data:  
Precision of Monitoring Devices: The precision of monitoring devices is crucial for effectively detecting cracks. Optical smart sensors and laser plumb lines, with precision up to 0.02 mm, are essential for capturing subtle displacements that indicate crack presence. A monitoring device with an accuracy of 0.05 mm can detect a crack horizontally away (40 m in the study) from the center of the crack if the maximum opening is relevant (at least 0.8 mm in the study). Influence of Crack Length and Depth: Data indicate that doubling the depth of the crack substantially amplifies the opening (by about 75% in the study) and largely amplifies the increments in the records of monitored devices (by about 160% in the study). At the same time, doubling the crack length amplifies in a comparable ratio the increments in records of monitored devices (multiplied by 2.35 in the study). Influence of Reservoir Level: Given a crack of considerable length (45.4 m in the study) and a depth of 30% of the dam thickness located in the most likely crack zone, increasing the reservoir by X meters multiplies the increases in displacements by a value an order of magnitude lower (close to X/7.3 in the study). Location of Cracks: Cracks in different locations exhibit distinct displacement patterns. Upstream cracks generate larger radial increments in displacements, whereas those downstream may not open under normal loads but still affect measurements due to relative vertical and radial sliding. Internal Hydrostatic Pressure: Ignoring hydrostatic pressure inside cracks leads to significant errors (averaging 42% when increments exceed 0.1 mm and up to 78% if they are smaller). Monitoring System Configuration: The arrangement and number of devices directly influence the ability to detect cracks. A well-distributed and dense system significantly enhances the detection of structural anomalies. The study employed additional virtual devices to simulate a more comprehensive system, located at mid-height and crest levels. It is not straightforward to identify the position of the crack directly from the monitoring results. The fact that the measurement point is 20 or 40 m horizontally distant from the center of the crack can be decisive for the detection of the crack. Relationship Between the Position of the Crack and the Position of the Monitoring Device: The alterations produced by crack A in the results recorded by device A are similar to the alterations produced by crack B in the results recorded by device B if both cracks have the same opening and the devices are located at the same distance from their crack. In summary, the most effective devices for detecting cracks, as shown in Table 1, can detect significant cracks located near the foundation (in the studied dam, that means openings greater than 0.62 mm and radial displacement increments over 0.27 mm). These findings underscore the critical importance of meticulous monitoring system design to ensure the continuous structural safety and operational integrity of arch dams. This study also serves as a basis for future lines of research, such as further developing the analysis of Figure 13 to determine which monitoring strategies are most appropriate depending on the expected reservoir levels. Conceptualization, M.A.T. ; methodology, M.A.T., A.C. and E.S. ; validation, A.C.; investigation, A.C.; writing--original draft preparation, A.C.; writing--review and editing, M.A.T. and E.S. ; supervision, M.A.T. and E.S. ; project administration, M.A.T. ; funding acquisition, M.A.T. All authors have read and agreed to the published version of the manuscript. Not applicable.