Extensometers and Settlement Gauges

ROD EXTENSOMETERS:

Rod or multiple point extensometers with long base, allow precise monitoring of displacement, relative movement and deformation of rock and soil at different depths and distant from the measuring point.

The extensometers are made of one or more rods of different material depending on the specific application, to a maximum of six, which are inserted in a borehole and anchored, by means of a specific device, at different depths or distances (horizontal holes). The opposite end of each rod is then connected to a reference head and left free to slide inside this. Displacements of the anchor points relative to the reference head, or vice versa, movements of the reference head relative to the anchor points of the individual rods are measured directly at the head by means of mechanical and manual instrumentation for example centesimal dial gauges and calipers, or automatically by means of special electrical displacement gauges (LVDT, potentiometric and vibrating wire).

The rods can be made of stainless steel, Invar steel or fiberglass, depending on the material of the structure and the type of measurement required.

Typical applications include the shifting and settling of foundations, relaxation or failure of the rock around tunnels, shafts, caves, excavations in general, monitoring of natural slopes, quarries and mining operations, monitoring of deformation of retaining walls, bridge piers, dam shoulders, dam foundations and various other works.

SETTLEMENT PLATE:

This device is used for the measurement of settlement in the ground, foundations and other areas of embankments and has only one measuring point per column.

The settlement gauge plate is formed by a sturdy plate integrated with the measuring point or reference point, to which the measuring rod is connected with a flexible tube for protection and guidance. The opposite end is free to slide inside the guide element which is fixed to the external measuring and reference point. A graduated leveling staff or centesimal gauge located on the rod measures changes of distance between the plate and the external reference point.

Fittings are available for the installation of automatic sensor heads for the measurement.

USBR extensometer:

The USBR extensometer allows the measurement of deformation in embankments, both in the foundations and in the various layers of the embankment itself. It consists of a extensometer column made of pairs of galvanized iron tubes, of differing diameter which can slide between themselves and are attached to a steel plate fixed to the ground.

Using the USBR probe, the position of the lower part of the smaller diameter tube can be measured.

The measuring unit is composed of a graduated tape in stainless steel mounted on a roller support that is fixed to the column head and holds a metric vernier; The USBR probe is attached to the free end of the tape which supports it during its descent and ascent inside the settlement column during measuring. Devices for collimation, leveling and triangulation can be applied to the head element enabling its correlation with external fixed points.