Quality control of ground stabilisation by seismic measurement with optic fibre

Purpose and goal

The goal is to develop a method for controlling soil stabilization, which can be used routinely to ensure that the procedure has involved the entire volume of soil that was intended to treat. Seismic measurement with optical fiber is a newly developed technology, which has not previously been tested in this context. A big advantage is that the sensors are cheap and robust, and the same sensor cables can be used for temperature measurement. The main part of the project is the evaluation whether sufficient geometrical resolution and signal quality can be achieved via fiber optic sensors.

Expected results and effects

Resultaten bevisar att signalen från fiberoptik är analog till de akustiska mätningar med accelerometer och geofoner. Resultatet med dagens teknik att fiberoptiska sensorer motsvarar en spatial upplösning som motsvarar konventionell mätning med 2m sensoravstånd. DAS är för närvarande under utveckling och man kan förvänta att den spatiala upplösningen snart kan komma att bli bättre. Vi analyserade ett extremt fall och vi är övertygade om att metoden kan vara användbar för undersökning av andra typer av markstabilisering (t.e.x. Masstabilisering) än de som presenterats här.

Planned approach and implementation

The main limit of DAS systems for civil engineering and environmental applications is the spatial resolution (Gauge length) that cannot be smaller than 2 m and partially restricts the frequency content of the recorded signal. In spite of this, the test along a concrete pile shows the possibility of recording high frequencies. In this specific case, the resolution plays a role only if we look at the distribution of the signal along the cable, but it seems to do not affect the single traces that are in perfect agreement with the reference measurements via an accelerometer.