Potential of Terrestrial Laser Scanner techniques and Geographic Information System for Concrete Dam Monitoring
Abstract
Monitoring the deformation of concrete dams is of vital importance for avoiding catastrophic loss of infrastructure and life. However, dams monitoring still being a challenging task. In the last years, significant efforts have been undertaken by international researchers to find an efficient way for deformation monitoring of this kind of structures. This paper aims threefold. Firstly, to present different methods and means using for monitoring concrete dams. Secondly, to identify the opportunities that could potentially improve the inspections and the monitoring behavior using Terrestrial Laser Scanner (TLS) techniques. Based on a dense and accurate 3D point cloud and images provided by TLS, it is possible to detect vertical and horizontal deformations and all pathologies affecting the dam safety, such as cracks. Thirdly, to show the importance of Geographic Information System (GIS) that allows managing a 3D database, spatial analysis of all external pathologies, planning with developing a suitable monitoring plan and decision making. In this paper, it is clearly highlighted the importance of using TLS and GIS in order to develop an effective dam monitoring process that can help identify structural problems before they become critical and endanger public safety.
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Introduction
In the field of civil engineering, dams have always been considered as specific engineering structures [1]. However, as all concrete structure, aging is a problem that concerns more and more structures in use [2]. This mechanism is an important concern for the operator of this type of structure because it causes damage [3] that can reduce the life span and affect the stability of the structure [4]. For avoiding catastrophic loss of infrastructure and life, dams monitoring is of vital importance [5]. It is based, inter alia, on the instrumentation whose efficiency is related to two factors: the early detection of anomalies and the measures transmission speed [6]. Corollary to the security process, it sets in conjunction visual inspection, nondestructive auscultation (geophysics methods) and instrumentation, that is, the installation of measuring instruments outside and inside the structure [7].
In the last years, significant efforts have been undertaken by international researchers to find an efficient way for deformation monitoring of this structures. Measuring and monitoring deformations of these structures still being a challenging task. Several techniques and means are used for dams monitoring such as geodesy, geomatics, sensor technology, remote sensing, photogrammetry and Multi Temporal Interferometry (MTI) techniques [8],[9],[10] . However such technique, though undeniably very accurate and reliable, has disadvantages.
Also, GIS is used extensively in the fields of architecture and civil engineering for monitoring engineering structures but rarely for monitoring dams. Even commercial solutions available in the GIS market are pretty poor in 3D.
This paper aims to introduce a new method based on TLS and GIS to monitor, periodically in 3D, the behavior and the evolution of external pathologies, in particular cracks affecting downstream of a dam and be able to draw good interpretations by making interventions in time. This solution is based on a 3D survey obtained by high precision TLS carried out in 2012 and 2016 on a vault dam named Asfalou, located in Morocco at 65km from the city of Taounat.
Conclusion
In conclusion, we can say that the developed solution has demonstrated its interest and relevance in the context of the management and monitoring of the evolution of the cracks that may affect the downstream face of a concrete dam. Indeed, benefiting from the characteristics of TLS and strength of GIS, the application allows:
Capitalize the information, gather them into a single tool,
Establish a platform for monitoring the health of the dam of Asfalou,
Update continuously and accurately the database according to different auscultations,
Provide a communication tool: it allows the user to view the cracks by characteristics or by adopted thresholds.
Plan and make fair and right decisions.
And finally, it saves time and cost.