IoT providing effective ground vibration monitoring.

Smart Cities are using wireless vibration sensors to protect people, buildings and machinery from underground drilling.

The impact of ground vibration during underground drilling is a global concern, with Melbourne coming under the spotlight recently due to planned tunnelling for the Melbourne Metro Tunnel.

Early next year, four massive tunnel boring machines (TBMs) will be used to construct twin nine-kilometre tunnels at depths of up to 40 metres.

Vibrations from the tunnelling may affect sensitive medical equipment at Parkville’s Victorian Comprehensive Cancer Centre (managed by the Peter MacCallum Cancer Centre) and the neighbouring Royal Melbourne Hospital for a brief period. However, the Melbourne Metro Rail Authority is confident the impact can be minimised.

Indeed, tunnelling for metro systems below fragile buildings and sensitive equipment has been done all over the world. In London, Crossrail’s high-profile project used eight TBMs over a three-year period to bore 42 kilometres of rail tunnels under the historical city snaking between the existing Tube network, sewers, utilities, and hidden rivers at depths of up to 40 metres.

Smart cities utilise wireless vibration sensors for monitoring ground vibration to ensure tremors are kept below recommended levels.

What are the Limits?

In Australia, the limits are defined in:

• AS 2670.2–1990 Evaluation of human exposure to whole-body vibration – continuous and shock-induced vibration in buildings (1 to 80 Hz)
• ISO 2631–2:2003 Mechanical vibration and shock – evaluation of human exposure to whole body vibration – Part 2: Vibration in buildings (1 to 80 Hz)
• BS 6472 –1:2008 Guide to evaluation of human exposure to vibration in buildings (sources other than blasting)
• BS 6472–2: 2008 Blast-induced vibration

Of course, humans are able to detect shaking at thresholds well below the level that is likely to cause damage to buildings and machinery.

As a result, the limit for human comfort (residential and offices) is set at 0.6mm/s – well below the limit for damage to buildings and machinery at 15mm/s.

It’s also important to note that tremors affecting human comfort are measured over an exposure time period. One or two loud noises won’t distress most people, but constant drilling over several hours will have a cumulative impact! On the other hand, the damage limit for buildings and machinery is an instantaneous reading.

Despite the differences, both human comfort and building/machinery vibrations require continuous monitoring. To maintain adequate human comfort, exposure needs monitoring over time. In the case of buildings and machinery, you are likely to miss a bad tremor if you just take spot readings.

Smart Cities Automate Ground Vibration Monitoring

While it is standard procedure to monitor tremors during underground drilling, the automation of ground vibration monitoring has many benefits.

At Minnovation, we have developed a range of Machine Health Monitors (MHM) to continuously process data. They send alerts if either threshold – human comfort/safety or building/machinery – are breached.

The MHM4 with the ViBX335 sensor can take measurements in real time and also for an online stream of data – this updates every hour and can be used to identify trends.

Rather than a site manager or consultant periodically logging in to the software to manually analyse the data, the artificial intelligence (AI) scripts do the monitoring for you.

The automated system is more accurate because it removes human error and bias. The AI scripts pick up issues that might otherwise be missed or that might take longer to notice.

This tool for continual improvement has major cost benefits because small issues can be rectified before they escalate into major problems.

ViBX335 Specs

• perfect for measuring human comfort/safety and seismic vibration in buildings and facilities
• operates in the 0-400Hz frequency range
• 10,000g shock survival
• compact size – 25mm round x 60mm
• SP13 military-grade connectors rated to IP68 dust and water protection
• low power consumption – 350 μA (typical)
• excellent temperature stability

The Ground Vibration Monitoring Solution

Automate your ground vibration monitoring with our MHMs featuring the ViBX335 sensor.