The dredging activity is increasing worldwide due to ships that require bigger drafts, and consequently deeper navigation channels. Some dredging projects requires the operation of cutter suction dredgers on open waters, once these are capable of removing compact sediments and rocks while still maintaining a good productivity. These facts motivated the creation of a weather driven downtime prediction software for this type of operation, based on simplified calculations of the main dredging systems of a CSD. The motions caused by waves, and the forces and moments caused on these dredgers by winds, waves and currents were analyzed in order to evaluate the influence of each parameter magnitude and direction on the behavior of the vessel. The main criteria of the dredger influenced by this conditions were determined by a literature review as being the swing winch required power, the interaction between the cutterhead and the soil, and the anchoring system resistance, this that can be both a spud pole system stress or the Christmas tree cable tension. In this research, only the spud pole system bending stress was considered. Three mathematical models were developed to represent those systems. Since the non-linearity of the relation between the reaction forces of the dredger and the soil was not an object of the study, this process is represented by a constant user defined reaction force and a horizontal cutterhead velocity model. The efficiency of these models were tested by applying them on a case study of the dredging of the Açu port on the Brazilian coast by the Taurus II dredger. Simultaneous wind, wave and current data data were used as input to these models by creating a time series scenario of the operation period. The results for both scenarios showed that the operation would be close to impossible due to wave generated dynamic stress on the spud pole.
This paper describes the procedures and results of an airborne magnetic survey using Unmanned Aerial Vehicle (UAV) conducted to support Search and Rescue (S&R) teams after the failure of a mining tailing dam at the Corrego do Feijão Mine, in the state of Minas Gerais, Southeast Brazil. The accident claimed 270 lives, practically destroying all the mine’s infrastructure. After the accident, the use of a fast, efficient, and cost-effective method to locate preferential sites for the rescue team to work was critical. Due to the difficulty of direct access to the impacted area, and since most of the affected infrastructure consisted of metallic materials, an airborne magnetometer was the logical choice. First, some performance tests were conducted in order to define the survey configurations, such as flight altitude, transect spacing and anomaly’s detectability threshold. After that, task priorities were set, and the survey area divided in small blocks according to their morphological characteristics using aerial photos of the impacted area. The results showed that the system was able to detect all relevant anomalies. The correlation of the anomalies with aerial photogrammetry helped to discard false anomalies, making the whole operation much more efficient. This increased the effectiveness of the S&R teams as well as the planning of the dredging operations by defining the preferential locations for the interventions.
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