Wireless Load Monitoring of Retention Systems

In some cases in today’s basement building process the construction contract documents require the contractor to establish a monitoring system to observe the behaviour of the excavation support system. Traditionally monitoring systems such as inclinometers are installed at settlement points along the sides of the excavation and tape extensometer measurements across the excavation.
The latest development in proprietary support systems gives us the ability to equip struts with integrated wireless load monitoring capability. This fully automated service is a huge leap forward in the field of excavation monitoring and offers engineers instant access to the real-time performance of their temporary works schemes by simply logging onto a website and accessing the data all without leaving the comfort of the office.

Coates Hire's wireless load monitoring system and our hydraulic struts are frequently used in conjunction with bored and sheet piled walls where progressive support is required during the excavation process. They can be used directly against capping beams and conventional steel framing where they can be readily relocated, as the construction process requires. The integral hydraulic ram can be used for load monitoring, and can pre-stress or pre-load a support system to minimise the risk of wall deflection and consequent ground settlement around the excavation.

The heart of the system is a load sensing pin located within the end swivel connection of the prop. Each of these load pins is connected to a radio telemetry acquisition module via a short length of cable which is then housed away from potential damage within the strut casing, adjacent to the hydraulic ram.
The battery powered telemetry acquisition module draws data on demand from the pin and transmits the live load data to one of two available viewable receiving sources. Coates Hire offers two options to their customers for the collection and viewing of the load data.

In its simplest form the receiver is a wireless hand held display which will pick up data from any of the struts. The handhelds have line of sight distances of up to 200m and enable the user to scroll through and manually record the data on each prop. Coates Hire configures the handhelds to display in tonnes, meaning that no further conversion calculations are necessary for their customers.
The second option introduces a more comprehensive and fully automated remote monitoring service that can be tailor made to suit specific customer requirements. GPRS sampling device and battery pack are located conveniently onsite and within range of the pins. The unit automatically gathers data at pre-set intervals, and transfers this via the GPRS network. There is the potential to set the destination for the data as text message, e-mailed data file, or both, which then enables the information to be easily compiled in graphical format for simple comparative purposes.

There is a warning trigger system that runs in parallel with this general data collection system, which uses up to 20 pre-programmed warnings keeping the user up to date with any substantial load increases without having to continuously keep an eye on the data. If measured loads in any of the props exceed any of these pre-set levels, the unit will in turn trigger either an automatic email or a text message to be sent to the nominated recipients.