Lienhart W, Lackner S, Supp G, Marte R (2013) Evaluation of State of the Art Methods for Surface Monitoring of Earth Filled Dams, Proc. 2 nd Joint International Symposium on Deformation Monitoring (JISDM), Nottingham, UK: 8 S. Evaluation of State of the Art Methods for Surface Monitoring of Earth Filled Dams W. Lienhart, S. Lackner Institute of Engineering Geodesy and Measurement Systems Graz University of Technology Graz, Austria werner.lienhart@tugraz.at G. Supp, R. Marte Institute of Soil Mechanics and Foundation Engineering Graz University of Technology Graz, Austria Earth filled dams are commonly used as flood prevention dams and for hydroelectric power plants. Their stability is critical for an uninterrupted operation and a reliable protection from catastrophic incidents. Graz University of Technology carried out a series of life-size experiments to evaluate different state of the art methods for monitoring surface movements of earth filled dams. Controlled vertical load was applied in these experiments to an earth filled dam and the resulting deformations were measured with geodetic and fiber optic methods. Single points on the slope were continuously tracked with robotic total stations. Additionally, the whole dam surface was monitored using a scanning total station. Finally, relative movements between points on the dam were measured with fiber optic sensors based on fiber bragg gratings. The achievable measurement precision and the relation between acting load and resulting deformation is investigated in detail for every measurement technique. We show in our evaluation that absolute deformations can reliably be detected with the geodetic methods. However, individual loading steps cannot be resolved due to the limited precision of the geodetic measurements. Our results demonstrate that the sensitivity of the structural health monitoring (SHM) system can be significantly increased with the fiber optic sensors and the scanning data also contribute to assess the stability of the experiment setup. Structural Health Monitoring; Deformation Analysis; Fiber Bragg Grating; Scanning Total Station; Flood Prevention Dam I. INTRODUCTION In 2012 a new hydroelectric power plant was built on the river Mur in the south of Graz, Austria. Earth filled flood protection dams were erected on both sides of the river as part of the safety plan of this project [8]. An experimental dam with 3.5m (width) x 3.0m (height) x 27.0m (length) was constructed in the vicinity of the water plant to verify the stability of the flood prevention dams. The dam material of the test dam was the same as the material used for the flood prevention dams. The slope angle was 60°. In the experiments slope failures in longitudinal direction were forced by applying vertical loads up to 800kN/m² on the dam crest. The goals of these experiments were to determine the shear parameters of the dam material, to evaluate the performance of modern slope stabilization methods and to assess different monitoring methods. In this paper we focus on the evaluation of the geodetic and fiber optic monitoring program developed for this project. II. LOADING EXPERIMENTS Several loading experiments have been carried out. In each experiment vertical load was applied onto the dam crest with a steel traverse and two hydraulic presses, see Fig. 1. Surface deformations of several centimeters were predicted from numerical simulations. The dam was either not stabilized, stabilized with two Spideranchors as indicated in Fig. 2, or stabilized with two Spideranchors and a geotextile. A Spideranchor consists of an iron anchor head and iron rods which are screwed through this anchor head in different angles into the ground [9]. The idea of the Spideranchor is to stabilize the dam like the roots of a tree. Figure 1. Experimental dam in the vicinity of the hydroelectric power plant