Elevated Water Storage Tank - Structural Monitoring

In Germany, the construction of a new drinking water storage tank required the excavation of a 10 m deep construction pit in the immediate vicinity of an existing tank.  This meant the existing tank would need to be monitored in order to manage the risk of structural damage arising from deformation associated with the excavation and construction activity.

Senceive partner Allsat recommended Senceive's tiltmeters for this application for a number of reasons including automated readings and alerts, cost effectiveness, ease of installation and durablity: 

"The advantages of Senceive technology over traditional monitoring solutions are obvious. In principle, automated monitoring systems are worthwhile compared to regular manual measurements, for example with a total station or level, even if the project duration is quite short. The savings in personnel costs, compared to daily levelling for example, soon make an automated system attractive in terms of price. In addition to cost efficiency, Senceive's monitoring system impresses with its fast and flexible use. The sensors arrive pre-configured and can be installed on the structure using various mounting options, such as gluing, drilling or magnetic fixings. Due to the internal batteries of the sensors and the wireless networking, the use of power and data cables is no longer necessary. At the same time, the sensors are virtually maintenance-free, even during monitoring projects that extend over several years. The design provides optimum protection against weather and damage. Installation of the system is so simple that it can be carried out by non-specialists."

Allsat installed five NanoMacro Triaxial Tilt Sensors on the wall of the existing water tank. These were configured to provide scheduled reporting of detected movement to sub-millimetre accuracy and to send alerts in the event of any movement thresholds being exceeded.

When the client, Harzwasserwerke GmbH reviewed the data they confirmed that patterns in the tilt meter data correlated with the activity on the adjacent construction site. There was also a very clear correlation with the water level in the tank. Allsat remarked that "this impressively demonstrates the measurement accuracy of the Senceive sensors and the enormous added value of a continuous monitoring system."

Figure 1 Excerpt from WebMonitor

Figure 1 shows an excerpt from WebMonitor™ - Senceive's data viewing platform. The inclination of the outer wall of the container is shown outwards, i.e. orthogonal to the course of the structure. For better comprehension, the measured inclination in degrees is converted into millimetres per 7 metres, i.e the height of the structure. The period of subsidence and re-damming of the reservoir can be clearly seen between February 16th February 23rd in the data. The outer sensors 1 and 5 (light blue and grey) show less movement than the sensors in between, which can be explained by the square design of the structure. Before and after the deformation event, the temperature-related diurnal cycle of the structure becomes visible. The recorded deformations (< 1 mm) were well below a critical range.

One of the key benefits of Senceive technology in this type of application is its suitability for monitoring both during construction activity, and for an extended period after that activity. The typical battery life of a tilt meter is 10 to 15 years and only minimal maintenance is required.

"By means of a continuous monitoring system from Senceive, many classic monitoring solutions can be replaced easily and cost-effectively and precise measurement results can be achieved. The system impresses above all with its uncomplicated installation and durability without maintenance. There are many  possible applications: ranging from deformation monitoring during construction to longer-term monitoring of structural health after construction." (Allsat)

The system has provided the client with the data they need to make well-informed decisions. "We are simply thrilled with the Senceive sensors. The deformation results are impressive." (Ullrich Britz, Harzwasserwerke GmbH)