LANDFILL IN THE SOUTHWEST
Key Project Details
Client: RSK
Sector: Waste
Contract Value: £80,000
Services: CPTu and Unexploded Ordnance (UXO)
In August 2022, Central Alliance was contracted by RSK to conduct a static cone penetration test (CPT) campaign at an old industrial landfill site in the Southwest of England. This involved 186 combined CPTu/magnetometer tests. This was completed over two separate visits to the site. The objective was to clear the site of UXO risk and provide the client with an understanding of the soil behaviour below the landfill.
The site was a post-war industrial landfill over tidal flat deposits; the site was also topped with 3-6 m of heavily compacted piling mat to make the site level and suitable for access by large piling rigs. The landfill was considered contaminated, and the soils below were identified as an unexploded ordnance (UXO) risk, and therefore a UXO engineer was present on the rig throughout the testing campaign.
Testing was carried out on both visits using our 200 kN tracked CPT rig, utilising a combined magnetometer and DP15 CPTu piezocone, and adhered strictly to BS EN ISO 224576-1:2012. After discussions with the client, a target depth of 20 m was agreed upon, with the client’s on-site rep informed of any positions not reaching that depth to come up with an alternative method.
CPT testing was chosen for this site due to it being classed as RED on the contamination scale, meaning the costs and risks for a conventional drilling campaign would be far too high.
On the first visit it was not possible to complete the planned testing campaign; this was either due to the pressure required to break through the 6 m thick mat and heavily compacted upper layers or due to high probe inclination within the landfill.
The CPT engineer stated that this landfill presented unique testing difficulties because of the mixed contents of the landfill (essentially household and industrial waste); the probe will often follow the path of least resistance, leading to high inclination, which can damage the equipment.
To counter these issues, RSK hired a sonic drilling rig to pre-drill to the base of the landfill and install a plastic pipe to allow the CPT a straight push into the tidal flats below. The drillers had to take care not to push beyond the bottom of the fill due to the UXO risk in the natural material below. Sonic drilling was chosen because of its ability to drill without flush, thus reducing the contamination risk that conventional drilling would create. The install was chosen to be no larger than 100 mm in diameter to allow the CPT rods to retain lateral support as they push through the natural material below.
Our results from the testing confirmed there was no UXO risk at the client’s pile locations, and the CPT results were sent on to the client to use in their design calculations. In addition, a bespoke report provided the client with the thickness of the landfill at each location, which was determined by cross-referencing changes in the CPT soil behaviour with a decrease in ferrous readings from the magnetometer.
In August 2022, Central Alliance was contracted by RSK to conduct a static cone penetration test (CPT) campaign at an old industrial landfill site in the Southwest of England. This involved 186 combined CPTu/magnetometer tests. This was completed over two separate visits to the site. The objective was to clear the site of UXO risk and provide the client with an understanding of the soil behaviour below the landfill.
The site was a post-war industrial landfill over tidal flat deposits; the site was also topped with 3-6 m of heavily compacted piling mat to make the site level and suitable for access by large piling rigs. The landfill was considered contaminated, and the soils below were identified as an unexploded ordnance (UXO) risk, and therefore a UXO engineer was present on the rig throughout the testing campaign.
Testing was carried out on both visits using our 200 kN tracked CPT rig, utilising a combined magnetometer and DP15 CPTu piezocone, and adhered strictly to BS EN ISO 224576-1:2012. After discussions with the client, a target depth of 20 m was agreed upon, with the client’s on-site rep informed of any positions not reaching that depth to come up with an alternative method.
CPT testing was chosen for this site due to it being classed as RED on the contamination scale, meaning the costs and risks for a conventional drilling campaign would be far too high.
On the first visit it was not possible to complete the planned testing campaign; this was either due to the pressure required to break through the 6 m thick mat and heavily compacted upper layers or due to high probe inclination within the landfill.
The CPT engineer stated that this landfill presented unique testing difficulties because of the mixed contents of the landfill (essentially household and industrial waste); the probe will often follow the path of least resistance, leading to high inclination, which can damage the equipment.
To counter these issues, RSK hired a sonic drilling rig to pre-drill to the base of the landfill and install a plastic pipe to allow the CPT a straight push into the tidal flats below. The drillers had to take care not to push beyond the bottom of the fill due to the UXO risk in the natural material below. Sonic drilling was chosen because of its ability to drill without flush, thus reducing the contamination risk that conventional drilling would create. The install was chosen to be no larger than 100 mm in diameter to allow the CPT rods to retain lateral support as they push through the natural material below.
Our results from the testing confirmed there was no UXO risk at the client’s pile locations, and the CPT results were sent on to the client to use in their design calculations. In addition, a bespoke report provided the client with the thickness of the landfill at each location, which was determined by cross-referencing changes in the CPT soil behaviour with a decrease in ferrous readings from the magnetometer.
Key Project Details
Client: RSK
Sector: Waste
Contract Value: £80,000
Services: CPTu and Unexploded Ordnance (UXO)