Warehouse Slab Testing, Doncaster, UK

Project summary

The presence of sand-balls was detected within the slab during the pouring process and subsequent investigations. However, the extent of the problem was unknown. The use of tap testing was initially undertaken to try and map the locations of sand-balls around warehouse racking. The tap-testing proved to be inconsistent and unreliable thus a new objective method was required. After trails were undertaken GPR was proved to find and map the sand-balls objectively, and reliably. Murphy Geospatial was brought in to complete the scanning of all rack legs.

Murphy Geospatial UK Ltd carried out a Non-Destructive Testing (NDT) survey, on 2562No. of concrete slab areas (600mm x 600mm each) using Ground Penetrating Radar, to determine the presence of defects, particularly uncured sand-balls, within the slab.

The brief

The presence of sandballs was detected within the slab during the pouring process and subsequent investigations. However, the extent of the problem was unknown. Tap-testing was initially undertaken to try and map the locations of sandballs around warehouse racking. The tap-testing proved inconsistent and unreliable; thus, a new objective method was required. After trials were undertaken, GPR located and mapped the sand balls objectively and reliably. Murphy Geospatial was brought in to complete the scanning of all rack legs.

While the data was being collected our team on site also marked up check areas to be drilled on site. These were based on the GPR data interrogated on site (which was repeatedly found to provide more accurate data that tap testing). These locations were drilled based on our results and found to be accurate.

The challenges:

The project was on a large scale and required detailed scanning around each leg. Murphy Geospatial devised a unique workflow for the collection and recording of data and the processing of the results.

The site was a live warehouse and the team worked alongside the warehouse team to move materials and ensure the safety of the team during the works.

Our team:

Murphy Geospatial deployed two three-person teams to the site to complete the works within the required time scale. The teams worked in two eight-hour shifts over 20 days.

All data was uploaded to our servers, combined and processed. Once processed the data was interrogated by our expert GPR team to extract the key information from the data.

Our work:

The team completed over 50,000 individual GPR scan profiles on site, around each leg of the warehouse racking.

*Figure 1: An example of the area scanned by the team. This was repeated over 2600 times.*

Due to the scale of the project, it was key to provide up to date information on what had been done and the results. Murphy Geospatial created a bespoke web portal that detailed every survey location. This was updated daily to inform the client on what has been completed and the extent of issues.

*Figure 2: Complated portal with all locations finsihed. Green – no anomlies detected, yellow – anomly detected, Red – anomliy detected and confirmed through drilling.*

Results:

The proposed GPR methodology was successful in detecting voids and anomalies in the floor slab. For each location a results page was provided showing the survey data and results.