Settlement monitoring is essential to evaluate the possible problems and for risk management related to ground displacement on surface or underground constructions.
The most common applications are: Tunneling, Dams, Embankments, Deep excavations, Foundations, Pile testing, Retaining walls as diaphragm walls, Buildings affected by possible differential settlement, Structural health monitoring.
Fixed extensometers are basically columns used to monitor the settlement between two points. The lower point is a platform installed within an embankment or an anchor installed in a borehole. At the top head usually settlement is measured by topographic surveying. Measurements can also be taken automatic and remote by using special displacement transducers.
If a multipoint settlement monitoring is requested, three different models of magnet settlement gauge are available: The BRS extensometer, the T-REX extensometer and the DEX in-place extensometer.
The BRS magnetic extensometer is a column consists of a guide tube, an anti-friction corrugated sheath and a number of magnetic reference rings fixed on the sheath. The column is lowered into a borehole and grouted to the surrounding soil. Any settlement or heave occurring in the ground will be transferred to the magnetic rings. A simple magnetic probe attached to a graduated flat cable inserted into the guide tube, is able to detect the position of the magnetic rings and thus the vertical movement in the ground. The BRS extensometer being not a very accurate settlement gauge, but is inexpensive and allows measurement of many reference settlement points within one column.
The T-REX is a high accurate incremental extensometer able to detect meter by meter ground settlement. The guide tube is an ABS inclinometer column with reference magnetic rings installed at 1 meter spacing to each other. The incremental extensometer survey is taken with the T-REX system. This system consists of the T-REX extensometer probe connected to the measuring cable and is managed by the portable Archimede readout device. The T-REX system can be used not only vertically, but, by using pushing-rods, in any direction. In tunneling, with a horizontal T-REX tube installed horizontally from the excavation front, the customer is able to have accurate incremental displacement measurements ahead of the excavation front.
DEX in-place extensometer have the same working principle as the T-REX system. The significant difference is that the DEX consists of chain of in-place probes able to detect the position of the magnetic rings. With a DEX column operated with an automatic data acquisition system, the customer will be provided with automatic and very accurate settlement/heave monitoring results.
The DEX-S probe incorporates in addition to the DEX a built-in biaxial inclinometer sensor so that a DEX-S chain is able to provide continuous taken 3-D deformation profiles.
The H-Level is an automatic system for long-term monitoring of differential settlements in buildings, tunnels, and other civil structures. The system consists of a series of H-Level gauges that are connected hydraulically to a reference tank located at a stable location. Each H-Level gauge includes a high resolution pressure sensor that monitors the head of liquid resulting from the difference in elevation of the gauge and the reference tank.
The multipoint settlement system is an hydraulic system that can be used to monitor embankments or earth fill dams. The system consists of a number of pressure transducer hydraulically connected to an external reference vessel. This pressure transducers, equipped with a base plate are installed within the embankment.
The manual operated hydrostatic profile gauge is used for measuring vertical displacement in and below embankment. This easy to operate instrument of limited accuracy provides settlement profiles. Therefore a probe is pulled through a pipe previously installed in the embankment. The probe consists of a high precise pressure transducer that is interconnected to a reference vessel. The reference vessel is mounted on a electric hydraulic cable winch. The readings are taken with on the digital display at regular intervals by pulling the probe through the pipe.