Sistema de medição automatizado e com transmissão de dados para monitoramento de recalques em obras de aterros sanitários.

Abstract

Landfill monitoring can be considered as one of the main components of the Municipal Solid Waste (MSW) management planning. As long as it assists the design, implementation, operation, control and closure phases of landfills. Understanding the mechanical and biodegradable behavior of landfill waste mass is fundamental to take preventive or corrective actions inherent to structural and environmental issues. Settlements are one of the best parameters that defines the behavior of these sanitary landfills. On of that parameter is the vertical displacement that occur at different velocities, time and magnitude, due to their own weight, applied loads and, mainly, due to biodegradation processes. Despite the importance of monitoring, most of the measurement systems used in landfills are adapted from classical geotechnical engineering, not taking into account the peculiarities of this scope. The objective of this work was is to develop an automated measurement system to monitor surface and in-depth settlements of landfills. This system relies on wireless and remote data transmission, allowing better access to data. The development of the automated measurement system is based on a conventional methodology used in geotechnical engineering field. The implementation of the measurement system presented in this research involves the correlation of knowledge in geotechnical engineering, electronics, computer science, mechanics and telecommunications. That confluence of knowledge allows the development of a remote monitoring equipment, using electronic and electromechanical devices that favored the automation of the system and the transmission of data. The automated measuring system consists of a secondary system, a main system and a plate for settlement measuring, besides the guide tube and magnetic plates distributed in the waste mass at different depths. Its operation consists of automated measurements, in pre-established dates and times, detecting the position of each magnetic plate based on the amount of steps performed by a stepper motor. In order to validate and calibrate the system, a laboratory prototype was developed, consisting of a support for fixing the guide tube, magnetic plates and measuring tape. Initially, the analysis of the two measurement systems consists in positioning a magnetic plate at a determined height, and verify through the measure tape located inside the guide tube which position is the plate, this position is adopted as true value. The values of the measurements obtained by the measurement systems are compared with the true value. Parameters such as accuracy, precision and error of each measuring system are analyzed by descriptive statistics. Subsequently, the measurement systems are evaluated to determine its efficiency for each system. In order to calibrate the automated measurement system, a simple linear regression model was used, obtaining the line length (position) as a function of the number of turns (number of steps). This model is used for the treatment of the data after the transmission of the magnetic plate position. The measurements obtained by the automated measurement system occurred in reduced time, presenting accuracy and precision, with an absolute error of 19.40 mm. It was verified that the developed system is a good alternative of measurement, since it does not require the presence of an operator in situ, and it allows performing the readings in pre-defined time, generating reliable data and suitable interpretations.