How to easily understand the torsion correction function of ADM？ Sponsored

ADM deformation monitoring system is GINTEC's newly developed product for geotechnical engineering monitoring. 

You can visit their website: www.gintec.cn or contact them by overseas@gintec.cn to know more. 

How to easily understand the torsion correction function of ADM?

Some new clients seem to have diffuculty understanding ADM’s torsion correction function. In this article, we use a simple experiment to explain the torsion correction function of ADM works and its significance in real projects.

Why does the inclinometer casing experience torsion?

There are many reasons for torsion of the inclinometer casing, mainly including the following three aspects:

1. The material and producing technology of inclinometer casing. If the material is not stable, with the increase of time and external pressure, the inclinometer casing may experience torsion. It is also possible that the groove of the inclinometer casing twists when the inclinometer is produced, because of the producing ability.
2. The underground geological environment is complex, and the force of inclinometer casing in the hole can be uneven. In that case, torsion can be developed.
3. During the installation, torsion can be developed when the inclinometer casing is dropped down.
   

What’s the influence of torsion on the measurements?

Bind ADM to a vertical pole and put ADM against a wall at an angle. We can now envisage that ADM is monitoring a slope. The mark line point towards the wall.  

 

Based on the observation chart, we know that, before torsion is developed, the observation data are very stable. We will compare 4 parameters to illustrate the change after torsion happens.

1. X absolute value before torsion

The picture bellow shows the X absolute coordinates in 5 minutes. (X direction is same as the mark-line direction)

 

2. Deformation value of X and Y before torsion

The following graph shows the deformation value of X and Y. It can be seen that all deformation value are within 1.5mm.

 

 

3. Node deformation value before torsion

This 2m length ADMS has totally 4 nodes; with node 220086 being on the top. We can see that the deformation value of node 220086 is within 1.5mm.

 

4. Now, ADM is twisted 180 degrees; the mark line now points towards the opposite direction.

5. X absolute value after torsion

We can see that after torsion, absolute value of X is the negative of the value before torsion.

6. Deformation value of X and Y after torsion

We can see that now the deformation value of X is almost 1.8m, while the deformation value of Y is almost 0.5m; very large values.

 7. Node deformation value after torsion

We can see that node 220086’s deformation value becomes bigger abruptly, something that is abnormal.

 

How does ADM correct the influence on the measurement data?

For the ADM monitoring system, it just takes 3 easy steps, to correct the data for torsion and save them.

1. Select the moment before torsion occured.

 

2. Select the moment when torsion stopped

3. Then Click “Shift Correction”

 

4. After torsion correction, the deformation value of X is within 1mm, the deformation value of Y is within 3mm.

                       

  

Based on the test described above, we can see that the torsion of the inclinometer casing has a big effect on the measurement data. When the ADM is rotated 180 degrees, the angle between gravity and ADMS doesn’t change, but the deformation value shows a large change. Therefore, the torsion correction is necessary in horizontal deformation monitoring.