Strain Gauges & Pressure Cells
Pressure transducers in tunnel construction can be placed either “tangentially” to measure the strain in the shell, or “radially” between shell and rock. Pressure pads with larger surfaces are used, for instance, for measuring stress under foundations or in embankments.
Arc-Weldable Strain Meter WSM1Arc-weldable strain gauges are used to measure strain in steel and cast iron members. Typical applications include monitoring strain in structural members of buildings, bridges, dams, pipelines, reinforcing bars or piles as well as monitoring load in struts used to braced excavations. It can measure in tension and compression.
The strain gauge operates on the principle that a tensioned wire, when plucked, vibrates at its resonant frequency. The square of this frequency is proportional to the strain in the wire. The gauge is constructed so that a wire is held in tension between to mounting blocks that are welded to the structural member. Loading of the structural member changes the distance between the two mounting blocks and results in a change in the tension of the wire.
Our innovative system has a unique integral magnet design which incorporates a miniatur magnet coil assembly positioned inside a stainless tube of diameter 15 mm. The same tube has a high tensile strength, heat-treatened and tempered steel wire stretched between two end blocks. The wire is sealed in the tube by means of a set of double O-rings.
Shotcrete Strain Meter SSM-1Concrete strain gauges are particularly useful for the identification of compression and strain in shotcrete. The stress and shear forces can be calculated from the measured displacements, based on the stress-strain relationship and the appropriate material characteristics. Underground construction is a significant area of application for concrete strain gauges.
Especially the ongoing monitoring of the shotcrete loads and the subsequent optimisation of the support are indispensable preconditions to efficient and safe tunnel construction. Strain measurements are in addition often used for long-term monitoring of the inner shell of tunnels.