Tunnels are critical infrastructure objects with design lifetimes of 100 years or more. Knowledge of the behavior of the tunnel linings is crucial to ensure a safe and efficient construction and to detect structural deterioration at an early stage. Our solutions based on distributed fiber optic sensing enable the detection, localization, interpretation and quantification of deformations of tunnel linings. The sensing cables can be embedded into shotcrete, pre-cast tunnel lining segments or integrated into on-site-cast inner linings. Applications include the assessment of the tunnel lining during the construction phase and the long term monitoring of the structural integrity of tunnels. Compared to other technologies, DFOS measurements do not interfere with the tunnel construction or tunnel operation. One instrument can be used to observe sensing lines of several tens of kilometers and simultaneous of several cross sections from one central measurement position is possible. Furthermore, sensing cables can also be placed on the surface of existing tunnels to assess their strain behavior and to detect and observe cracks. Our software solution is capable of automated data acquisition, data analysis and automated alarming. We have successfully installed DFOS monitoring systems in several highway and railway tunnels in Europe and are also involved in large tunnel projects worldwide.
Piles and anchors are used to provide a stable foundation for heavy structures or to stabilize slopes and embankments. On large construction sites hundreds of these components may be installed. To optimize their length and to proof their bearing capacity load tests are often mandatory. With our distributed fiber optic sensing systems, we are able to monitor the strain distribution along the entire element with a very high precision of about 1µm/m every 10 millimeters or even better. This is equivalent to a chain of several thousand of resistive strain gauges in case of a pile with a length of some 10 m. Due to the high spatial resolution, cracks in the grout material of the structural elements can be detected and the progressive failure of the interface between the grout and the object, e.g. anchor or pile, can be observed. Furthermore, the measurements deliver detailed information about the size and distribution of different soil layers. Our software solution delivers results in real-time to control processes like pre-tensioning. The installed fibers can be used for monitoring during load tests but also in the long term monitoring. We have successfully performed loading tests in several European countries and internationally and are also involved in long term monitoring projects.
Bridges are one of the most crucial civil engineering structures in many countries, as the average age of these structures is typically high and today’s traffic load on this structures often exceeds estimates made decades ago. Knowledge of the structural integrity is therefore important to ensure safety of users and to schedule maintenance work at the right time. Our distributed fiber optic measurements can determine strain changes and curvatures of bridge decks along their entire length. This enables the detection of local deficiencies like cracks or leakages. Furthermore, the reaction to temperature change can be assessed which in turn also enables the performance assessment of expansion joints and bridge bearings. Our sensing lines can be embedded into concrete structures during construction or applied to the surface of existing concrete or steel bridges. The performance of our solution is proven by laboratory investigations of concrete beams and by on-site investigations with independent reference measurements.