Monday, 23 March 2015 07:14

Movement Gauge

Movement Gauges are the first available system that allows direct measurement of relative vertical movements in the base of wall or column structures in a cost effective manner. The numerical results, accurate to 0.1mm, provide engineers with irrefutable data upon which foundation and structural assessments can then be based.

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Pioneered by Structural & Civil Consultants Ltd. director Robert Thorniley-Walker MA(Oxon) FICE CEng MIStructE MIHT MIHBC CARE, the Movement Gauges have been successfully used in the monitoring of foundation movements since their initial trials in 1996. A paper on their advantages was prepared for the Institute of Structural Engineers (‘Movement Gauges: direct monitoring of foundations’, The Structural Engineer, Volume 84 Number 6, 21 March 2006) and a paper on their application and findings for the Institute of Civil Engineers Forensic Conference (‘Foundation Monitoring Techniques: Are they all they are cracked up to be?’ Proc. 3rd Int. Conf. Forensic Engineering, 10-11 Nov 2005, p119).

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The Gauges
The gauges are intended to be fixed either externally or internally to the walls around the building at convenient locations, and are read to 0.1mm with the telescope of an optical level set up within 5m of the gauge. Changes in relative level can then be monitored to produce characteristic graphs of foundation movements against time
. The gauges tend to be inconspicuous, and cause no significant damage to the fabric of the building.

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Advantages
As well as providing results to an accuracy of 0.1mm, the gauges constitute a simpler, cheaper, and safer method of movement monitoring when compared to alternative options. Traditional crack monitoring techniques such as the three pin system on their own give little forensic evidence on the cause or even whether distress emanated from the foundations or the superstructure. The gauges have been used to demonstrate the inaccuracy of the BRE Precise Levelling approach. Even the loss of a gauge only results in one set of missing data.
Movement gauges prevent unnecessary underpinning, with its associated fees. They frequently indicate that underpinning walls is not needed, even on historic buildings.

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Uses
Works associated with foundations tend to be very expensive and should only be recommended on definite data. Movement Gauges tend to pick up foundation movements in isolation from other structural movement. Sensitivity of just 0.1mm of relative movement allows the monitoring process to quickly provide useful quantitative data on which to assess the real need for foundation improvements or other wall strengthening techniques.