A method of isolating different components of prop axial force through FFT&BWF signal filters

It is common practice to monitor the performance of structural elements in deep excavation projects for construction safety, particularly when measuring the load of supporting props. However, the accuracy of prop axial force derived from vibrating wire strain gauge (VWSG) readings is affected by ambient temperature fluctuations, as well as other construction activities. Structural props that are exposed to a construction environment experience frequent contraction and expansion with temperature changes, and from multiple construction activities (e.g. grouting), which creates difficulties in separating these variations from the axial force induced solely by excavation. This paper introduces a new method to identify and isolate different components of prop axial force measured by VWSG, through the application of fast Fourier transform and Butterworth signal filter. The method was successfully applied to process the prop axial force measured from the construction of Crossrail’s Tottenham Court Road station, western ticket hall, and to identify three different components of the prop axial force. The results demonstrate a remarkable enhancement in deriving the major prop force attributable to excavation. This new approach not only facilitates swift processing of prop axial force, but also allows for quantifying the degree of restraint of props throughout the monitoring period.