As you well know, tunnels and other civil structures are subject to factors like shifting and subsidence, putting them at risk of sudden catastrophic failure in extreme circumstances and making them prone to long-term damage as they age.
Obviously, continuous geotechnical monitoring of civil structures is one of the keys to ensuring safety, but unfortunately attempts to achieve this in the past have often proven very time-consuming and prohibitively expensive.
With this in mind, it seems as if there is a need for the invention of accurate, inexpensive equipment that can quickly alert civil engineers to instances of structural instability.
Or is there?
Actually, there is no need to develop devices like these – they already exist.
The use of extensometers, especially multi-point borehole extensometers like our SMART MPBX, is already a common practice in mines all over the world, where they are used to monitor dams and the walls of open-pit surface mines, for excavations and tunnels in underground mines, and for many other monitoring tasks.
The easy-to-acquire, accurate geotechnical data MPBXs provide has already made an invaluable contribution to safety management in mining, and it stands to reason that the use of extensometers for civil engineering purposes, e.g. the structural monitoring of subway and traffic tunnels, could reap the same benefits.
The rugged yet inexpensive MDT SMART MPBX (Multi-Point Borehole Extensometer) is compact (33mm diameter), flexible, light (0.5 kg/m), and can be manufactured in lengths up to 100m as required with six anchor points positioned at user-specified intervals. It is fitted with an integrated electronic readout head (making it ideal for civil wireless monitoring) that is small enough to be recessed into a standard 50 mm (2”) borehole, with no requirement for reamed collars or oversize holes.
Installation is very simple; the MPBXs that arrive on site fully complete and ready to install with no assembly required are simply placed into a standard borehole and grouted in place – and multiple MPBXs can be installed into a single long borehole.
Once installed, SMART MPBXs are immediately ready to provide useful geotechnical data to engineers.
Read more about how they are monitored in Part 2 of this blog series, coming soon.