“2-metre rule” simulation for slab flatness
A dispute between the owner and the contractor responsible for construction of a slab on an industrial site (a distribution centre). We were tasked with checking the work carried out by the contractor.
This procedure can be tedious and time-consuming if the slab is to be checked thoroughly.
- Total area : 3000 m2
- Distribution centre already operational
- Checking departures from flatness under a 2 m straight-edge
- Computerised plot representing departures from flatness
- Use of the 2 metre straight-edge to determine areas which are out of tolerance
- Contoured plot
- Required accuracy : 2 mm
- 4 operations (one quarter of the slab per operation)
In the spirit of the R&D policy of TPLM-3D, we developed a new and rapid tool for flatness checking and acceptance of slabs and screeds. A very precise digital copy of the slab is produced and then subjected to a computer simulation of the 2-metre-rule procedure.
The slab data was captured in four stages (for internal organisational reasons at the distribution centre). The challenge for us was to guarantee reliable and homogeneous results, accurate to 2 mm, when the four surveys were combined. The slab is defined by several million points, one every 3 to 4 cm, thus providing an extremely realistic representation of the whole. By using appropriate computation procedures on the captured point cloud, we are able to bring the accuracy of our survey to the required 2 mm. In parallel with the laser scans, the emplacement of permanent reference points and their meticulous measurement was of fundamental importance in guaranteeing results at this level of accuracy. This systematic use of computational rather than manual procedures enabled the identification and unambiguous recording of out-of-tolerance points.
The final result is thus an AutoCAD file showing the position of every such point. Several colour-coded layers within AutoCAD indicate different categories of point : in the example shown here, grey and blue for high points and green and yellow for hollows.
To provide an overview of the deformations, we also supply a colour-coded map with contours at equal intervals. This cartographic representation provides an image which is easy to interpret.
- 1 deformation analysis in raster form, in an AutoCAD plot in DWG and PDF formats.
1 simulated 2-metre-rule flatness analysis in the form of an AutoCAD plot in DWG and PDF formats