WHEN USE THE LPMH SYSTEM?

• When lack of space: embankments with a narrow top, widening of an existing road,……
• Noise abatement walls made of residual waste
• Backfilling waterways 
• Embankments made of incineration residue 
• If continued monitoring of settlement is required after completion 
• Monitoring of the behaviour of underground pipes 
• Monitoring subsidence at waste disposal sites/landfills 
• When using level rods is considered not sufficiently accurate 

We carry-out these measurements with our own vehicles on a day rate basis.

Downloads:

  LPMH measuring soil settlement
  Monitoring the Rotterdam-Rijn pipeline

The SAAF (ShapeAccelArray/Field) consists of an articulated chain of sensor elements (segments) with a length of 0,305 or 0,500m. Each segment contains a multi-axial MEMS chip accelerometer that measures its angle of inclination in both X- and Y-direction. The segments are interconnected such that the SAAF can adopt any shape and thereby can follow the deformation of the soil in any direction. Result: in one picture the fully distributed 3D deformation of the soil over the full depth (up to 100m) with an unrivalled accuracy of 1mm over 30m. The SAAF can even be used horizontally to measure vertical deformations. 

Examples:

  Horizontal and vertical settlement of embankments
  Deformation of quay walls, sheet piling, diaphragm walls
  Determining the exact level and shape of underground pipes
  Deformation of subsoil suchas at tunnel construction sites

Download:

  SAAF

On construction drawings grout injection anchors are drawn as straight lines. Practice can be quite different: during the drilling process anchors can deviate easily from the intended path, both in the vertical and horizontal direction. There are good reasons why you would want to know the real shape of the anchor once it is in place.
To solve this measurement problem we developed ANCHORVIEW: an articulated chain of MEMS-chip multi-axial inclinometer segments that is lowered into the hollow core of the anchor. By subsequently reading-out all the segments in the chain the exact shape of the anchor is determined. As the measurement results are produced right on the spot in a matter of minutes ANCHORVIEW often is even used to verify the correct angle and shape during the drilling process itself. This technology is also used for soil freezing pipes, grout lines, boreholes and even things like prestressing ducts in concrete structures.

We carry-out these measurements as an independent party on a day rate basis.

This technology utilizes a special cable containing two parallel optical fibers: one fiber (the strain
fiber) is embedded in the cable jacket whereas the other one (the temperature fiber) lies strainless inside a tube that forms part of the same cable. Whenever the soil deforms at a certain location the cable is put under strain at that particular spot. This strain is transduced to the strain fiber. The temperature fiber will not experience any strain as it is lying loose and serves to compensate the strain measurements for variations in temperature.

The cable is connected to a reading unit that continuously launches a high frequency light pulse of one particular wavelength into the fibers and that analyses the backscattered spectrum. Independent of the length of the cable (up to tenths of kms) the spatial resolution is 1 (one!) meter. This means that even very minor local deformations are located with an accuracy of only 1 meter!

For very demanding applications under harsh conditions we apply a geotextile with factory-integrated fibers instead of single cables.

A number of fiber optic FBG sensors in series are embedded in the grout core of the anchor. This arrangement does not only produce the total anchor force but can also provide valuable information on the distributed absorption of the force along the length of the anchor rod. Irrespective of the number of sensors in series, only one single cable leaves the anchor head. Permanent installation of these sensors in gout anchors is often part of a Structural Health Monitoring system of a quay wall. The strain can be measured already during tensioning of the anchor. This enables a very accurate establishment of the relation between strain and applied load.

The early warning system for dikes and levees. A couple of optical fibers are embedded at a shallow depth at specific spots along the circumference of the dike's cross-section. The fibers are connected to a reading unit that continuously launches a light pulse through the fibers and that analyses the backscattered spectrum. From the shift of the so-called Brillouin wave length the reading unit automatically produces the distributed deformation over the full length of the fibers and thus the dike section under surveillance.

If at any location the deformation reaches a pre-set magnitude, an alarm is raised automatically. At the same time the location of the event is indicated with an accuracy of one meter, even if the dike is more than 30km long.

The system can be set to detect millimeter-scale deformations with a one meter spatial resolution. So a 20km long optic fiber is the equivalent of 20.000 sensors!