Sondex Settlement System


The Sondex Settlement System is used to monitor settlement and heave in excavations, foundations, dams, and embankments. It can also be installed behind retaining structures, such as sheet piles and slurry walls, and above underground openings, such as tunnels and shafts. The Sondex system indicates the depths at which settlement has occurred as well as the total amount of settlement.

Sondex Settlement System


The Sondex Settlement System consists of a probe, signal cable, a cable reel with a built-in voltmeter, and a number of stainless steel sensing rings. A survey tape is typically connected to the probe.

The sensing rings are fixed to a continuous length of corrugated plastic pipe which is installed coaxially with inclinometer casing or access pipe. The annulus between the corrugated pipe and the borehole wall is grouted. The corrugated pipe and its sensing rings settle with the surrounding ground.

To obtain measurements, the operator draws the probe through the access pipe. The buzzer sounds when the probe is near a ring, and the voltmeter reading peaks when the probe is aligned with a ring. The operator refers to the survey tape and records the depth of the ring. A sensitivity adjustment allows operation adjacent to steel pipes, piles, or other metal objects. Settlement and heave are calculated by comparing the current depth of each ring to its initial depth.

Installed Components

Access Pipe: Flush-coupled inclinometer casing is used when inclinometer readings are required. Otherwise flush-coupled PVC pipe can be used. After pipe and magnets are installed, the borehole is backfilled with grout.

Corrugated Pipe: Polyethylene drain pipe with 3 inch or 4 inch ID. Pipe can be installed in a continuous length or in 10 foot sections that are coupled and sealed carefully to prevent entry of grout.

Sensing Rings: Sensing rings are attached to the corrugated pipe at the specified depths. Rings can be attached to the corrugated pipe at the factory or by the user. The bottom ring is considered the datum ring.

schematic diagram of Sondex Settlement System in use

For more information

Please download the datasheet for the Sondex Settlement System. The data sheet can be viewed and printed with Adobe Acrobat Reader.

Sondex Settlement System Specifications

Readout with 50 m cable50810305
Readout & 100 m cable50810310
Readout & 150 m cable50810315
Readout & 150' cable50810015
Readout & 300' cable50810030
Readout & 500' cable50810050
Sondex readout includes reel, electronics, batteries, laser-marked cable, and probe. Survey tape is not included
ResolutionMetric gauging tapes have 1 mm graduations. English gauging tapes have 1/16 inch graduations. The laser-marked cable that is connected to the probe has 2mm or 0.01 foot graduations
RepeatabilityWhen the system used with a reference stand, precision approaches resolution of the tape
Probe Diameter43mm (1.7") OD
Temp Range-20- 50°C (0- 120°F)
Batteries3 AA batteries
Reel Diameter230 or 280 mm (9 or 11")
Sondex Corrugated Pipe, 3" ID50801600Use 3" pipe (3.625"OD) with 70 mm inclinometer casing
Sondex Corrugated PIpe, 4" ID50801700Use 4" pipe (4.3"OD) with 85mm casing
Coupling, 3" ID50801602For joining lengths of corrugated pipe
Coupling, 4" ID50801702
Cap, 3" ID50801601For bottom of corrugated pipe
Cap, 4" ID50801701
Mastic Tape51003800For sealing Sondex pipe couplings. Mastic is applied to gaps in coupling. Tape is then wrapped over coupling. Finally, cable-ties are strapped on to provide strength
Sensing Ring, Factory Installed50801800Stainless steel straps can be factory installed at user-specified intervals. Factory installation includes overwrapping with mastic and tape to protect against corrosion. Rings can also be installed by the user
Sensing Ring, User Installed02842004