I came across an interesting case study involving the installation of several vibrating wire crack monitors and data collection equipment at the 1st century B.C. to 1st century A.D., Roman built galleries beneath Lisbon, Portugal. The galleries were not discovered until 1755 when a large earthquake destroyed half of Lisbon. Apparently these galleries sit flooded all but three days of the year when they are drained for inspection and tours. During one of these times, Geokon equipment was installed to monitor cracks in the structure. The equipment is waterproof and wiring allows the sensors to be read year round. The new data coupled with piezometer data showed that the draining of the tunnels in conjunction with the fluctuation of the groundwater (tidal) caused the cracks. (Photo from CÊGÊ by way of Geokon)
