Underground Deformation Measurement Using New Quartz Instruments

This work demonstrates the usage of two new quartz instruments, which are a tiltmeter and an extensometer that we developed lately to measure with high accuracy deformations of structures, volcanoes, tunnels, and ground surface. The stability of an underground quarry, near Paris in France was the subject of the study. The deformation of the quarry under different cases of loading during the process of constructing a highway that passes over it was analyzed. Tiltmeters were installed on the floor of the quarry and extensometers on the pillars to measure the deformations induced by the load of the fill materials applied over the quarry. The tilt and the compression were measured for different loading periods and for different durations depending on working conditions. Continuous records of measurements were executed during this experiment to show continuously all variations in the quarry deformation. The results of the tilt measurements showed instantaneous deformation associated with loading change. Meanwhile the compression measurement showed late effects after loading. A mathematical model was used to calculate the deformation under the same loading conditions. This was done in order to find positions of maximum tilt and compression in the quarry where the instruments can be installed. The model as well, enabled us to fix the range and sensitivity of the instruments. Finally, we compared between the measured and the theoretical values and we discussed the results.