At Campbell Associates, we are committed to providing the UK’s construction, demolition & acoustic industries with the most advanced and reliable environmental monitoring solutions. That’s why we were thrilled to showcase the power of our new Syscom Rock Vibration Monitor at the recent Institute of Acoustics meeting on “Measurement, Prediction and Assessment of Ground Borne Vibration.”

We seized the opportunity to put the Syscom Rock through its paces in a live, practical demonstration, highlighting its exceptional capabilities in real-world scenarios.

Putting the Rock to Work: A Live Demonstration

The practical session involved meticulously testing the vibration emitted by Geomatrix Ltd’s innovative system – a device renowned for assessing ground stiffness by emitting a precise sweep of frequencies (5Hz to 300Hz). This is crucial for understanding how vibration propagates, especially in complex urban areas where drilling, piling, and demolition are needed near sensitive structures.

Our new Syscom Rock monitor was strategically placed just 10 meters from the vibration source, alongside other leading systems, to meticulously measure ground-borne vibration across multiple cycles.

Real-Time Data, Real-World Insights with Sonitus Cloud

One of the Syscom Rock’s standout features is its seamless integration with the Syscom Cloud platform. As vibrations were generated, data was transferred in real-time, allowing us to immediately visualise critical insights. We demonstrated how background vibration levels were instantly displayed in X, Y, and Z directions, with clear indications of peak levels as the vibration source was activated and then scaled down.

The detailed signal files instantly revealed nuanced behaviours, such as the X and Y directions peaking earlier at a 30Hz frequency, indicating an observed decoupling effect of the machine. The Z direction, by contrast, peaked at 50Hz. This level of precise, real-time data empowers our clients to truly understand vibration propagation and make informed, proactive decisions on site.

Engineered for Efficiency: Solar Power & Single-Button Simplicity

Decision-makers in construction and demolition demand reliability and ease of use. The Syscom Rock delivers:

• Exceptional Power Efficiency: Powered by a compact, integrated solar panel, the Rock ensures continuous monitoring with minimal power consumption, even in remote locations.
• Effortless Setup: Its intuitive design means simple, single-button operation to initiate measurements, getting you up and running quickly with minimal training.

Secure Your Site’s Future with the Syscom Rock.

The Syscom Rock Vibration Monitor is more than just a device; it’s your solution for robust compliance, enhanced safety, and unparalleled insight into ground-borne vibration. Available or purchase and hire within the UK.

With increasing activities in and around our cities the importance of vibration has become a prominent feature. You might have heard of PPV, but what exactly is it and how does that affect us and our projects?

VIBRATION (PPV) – ALL THE ANSWERS!

What is vibration and where does it come from?

Ground vibrations are associated with different types of elastic waves propagating through the ground. These are surface waves, and bulk longitudinal waves and transverse waves (or shear waves) propagating into the ground depth. Typical frequency range for environmental ground vibrations is 1 – 200 Hz. Waves of lower frequencies (below 1 Hz) are usually called microseisms, and they are normally associated with natural phenomenae, e.g. water waves in the oceans.

Ground vibration is measured in terms of Peak Particle Velocity (PPV) with units in mm/s or mm/s-1. It should be noted that the PPV refers to the movement within the ground of molecular particles and not surface movement. The displacement value in mm refers to the movement of particles at the surface (surface movement).

Environmental ground vibrations generated by rail and road traffic may cause annoyance to residents of nearby buildings both directly and via generated structure-borne interior noise. Very strong ground vibrations, e.g. generated by heavy lorries on bumped roads, may even cause structural damage to very close buildings. Typical values of ground vibration particle velocity associated with vehicles passing over traffic calming road humps are in the range of 0.1 – 2 mm/s.

The main sources of ground vibrations at construction are pile driving, dynamic compaction, blasting, and operation of heavy construction equipment. These vibrations may harmfully affect surrounding buildings, and their effect ranges from disturbance of residents to visible structural damage.

Why do we monitor and what are the limits?

Ground vibration can cause serious structural damage but can also be a nuisance to local residents. There are clear limits mentioned for vibration due to construction/demolition in BS 5228-2. In table B.1 – page 36 of BS 5228-2 you will find the guidance on effects of vibration levels. These levels set out the human response to vibration, as in nuisance. When we look at potential damage to buildings table B.2 comes into place. Depending on the type of building there are different limits which are generally higher than the nuisance limits. In general, magnitudes of ground vibrations that are considered to be able to cause structural damage to buildings are above 15 mm/s.

Every ground vibration can be recorded and measured automatically. Since it is simple for everyone to protect people, buildings, infrastructure, soil, air and watercourses from negative environmental impact these days we see more and more demand for continuous automated monitoring so construction & demolition can move forward and communities can be developed with minimal disturbance.

To minimize the impact of vibration caused by construction & demolition works governing bodies often set limits that are aimed to protect individuals from levels likely to cause nuisance and potential cosmetic damage to buildings. You will often see limits of 10 mm/s which is a level likely to cause complaints and is close to the level of potential cosmetic damage in lightweight structures.  Amber alerts can also be sent at lower levels to give warning that vibration levels are getting closer to the limits.

It is also useful to store a waveform (very detailed data) when high vibration levels are recorded. This enables you to investigate the actual frequency content of the vibration event. BS 5228-2, table B.2 gives separate limits by frequency which can therefore be accurately assessed.

Please note that the levels in the tables below are for guidance.  You will see separate guidance/ limits on vibration close to historic buildings, utilities infrastructure and sensitive measurement equipment found in universities and hospitals.

HOW CAN CAMPBELL ASSOCIATES ASSIST YOU?

Our vibration monitors, processes and temporarily stores measurement data from vibrations and air shock waves locally in the instrument. Measurement data is automatically transmitted over the mobile phone network and the Internet to the Sonitus Cloud; our web-based measurement system according to an individual and adjustable schedule. Alerts are automatically sent by e-mail and SMS to those responsible when a measurement is registered that exceeds set limits or if a failure occurs, such as a cable break.

The monitor is fully automated and has full remote access to view & download data, print reports, set alerts and change settings. They are easy to install, maintain and can easily be relocated on site to ensure you can work confidently on site knowing you are working safely within vibration limits.

References:

Skipp, B.O. (ed), Ground Dynamics and Man-made Processes, The Institution of Civil Engineers, London, 1998.

Krylov, V.V. (ed), Noise and Vibration from High Speed Trains, Thomas Telford Publishing, London, 2001.

Santos, J.A. (ed), Application of Stress-Wave Theory to Piles: Science, Technology and Practice, IOS Press BV, Amsterdam, 2008.

Bull, J.W. (ed), Linear and Non-linear Numerical Analysis of Foundations, Taylor & Francis, New York, Abingdon, 2009.

AVA Monitoring – http://avamonitoring.com/en/vibration-measurement/ 2017

Observing the appearance of and measuring the change in crack width is a popular technique used to assess structural damage of buildings. Cracks are one of the first signs that there has been movement of the structure due to ground movements.

Typical ground movements associated with demolition and construction activities:

Heave When large structures are demolished there can be an upward movement of the ground beneath nearby structures as a result of soil expanding.

Settlement (also known as compaction) Downward movement as a result of soil being compressed by the weight of a building after construction.

Subsidence The ground beneath a building sinks which usually occurs when the ground loses moisture and shrinks. Areas with clay soil can be more susceptible. Changes to a water course, removing trees and vegetation and collapsing drain can all contribute to subsidence.

Landslip Downward movement of sloping ground.

Cracks can also indicate if there has been stress on the structure due to excessive transient and cyclical vibration. Guidance on vibration from construction and demolition activities is provided in BS5228-2 Code of practice for noise and vibration control on open sites.

Monitoring Crack Movement techniques The traditional method for measuring cracks is by installing a manual crack monitor

Figure 1 Manual crack monitor

Once the monitor is in position across a crack, movement can be read from the device and noted by the engineer during a construction project. This relies on regular site visits and good note keeping.

Automated Crack Monitors

In recent times it has become more popular to use digital crack monitors which can be linked to data loggers for remote access and to send you alarms if there are significant changes. The sensors often record temperature at the same time to display how a crack varies as structures naturally heat and cool. Data is typically displayed on a cloud platform at an hourly resolution for easy and complete analysis.

Figure 2 Ellitrack digital crack monitor and logger

The system should be left in place for as long as possible for you to build a picture of evidence to assess if the movement is still accruing and the direction. Modern loggers can run on internal batteries for several years to remove the need to visit site.

For further details please see https://www.campbell-associates.co.uk/crack-monitor

Understanding vibration levels and limits accurately is critical. So ensuring the device measuring the vibration is installed correctly is paramount. Our favourite device for measuring vibration in terms of protecting buildings and structures is the AVA-M80 vibration monitor with a tri-axial geophone. This unit will measure the Peak Particle Velocity in 3 directions and provide real-time email and SMS alerts as well as having a long term 8-month battery life.

Vibration limits are mentioned in BS5228-2 for construction and demolition works on open sites. Below are a few steps that should be taken when measuring according to the standard and guideline, in terms of the limits only. These points are general observations of the standard, and you should employee a qualified engineer to make an assessment on project and practice before commencing any works as these notes do not cover all important considerations when measuring vibration.

Step 1.

Identify who or what we are protecting. In BS5228-2, there are two tables with defined limits, one for human perception and one for structural damage. Let’s focus on structural damage only.

Step 2.

Identify the type of building. What are the limits? They are noted in Table B2.

Step 3.

Take note of the frequency range and limits accordingly. Notice how the vibration limits increases with frequency, but generally a lower limit for all is normal used, assuming the vibration sensor is setup to the correctly filter profile and standard. If we know the frequency and the level, potentially we can avoid a breach which is why the AVA-M80 monitor can collect this dataset with vibration waveform data.

In the table you will see at 4Hz the vibration limit is 15mm/s for cosmetic damage right up to 50mm/s at 40Hz.

Note that Figure B.1 refers to cosmetic damage! What is cosmetic damage?

• Cosmetic damage is usually considered as the formation of hairline cracks on drywall surfaces, or the growth of existing cracks in plaster or drywall surfaces; in addition, the formation of hairline cracks in mortar joints of brick/concrete block construction.

In the standard it also documents other types of damage such as:

• Minor damage is considered the formation of large cracks or loosening and falling of plaster or drywall surfaces, or cracks through bricks/concrete blocks.
• Major Damage to structural elements of the building, cracks in support columns, loosening of joints, splaying of masonry cracks, etc.

So, what are the limits for Minor and Major damage? Well as the standard mentions.