When the spoil material from a major culvert replacement project was found to be retaining too much moisture and therefore unsuitable for the planned disbursement elsewhere on the site, Monmouthshire based soil stabilisation specialists SMR (UK), in partnership with Richardson Recycling, were brought on-board to stabilise the excavated material; making it suitable for re-use and removing the need to import a sub base product and the need to send 3,500 tonnes of spoil to landfill.
As part of major culvert refurbishment works at the MOD/Crown owned Longmoor site, located just off the A3 on the Surrey/Hampshire border, soil analysis identified that around 1500m3 (3,500 tonnes) of the spoil material was moisture rich and unusable, and that treating it was the best solution. SMR (UK), working in collaboration with Richardson Recycling, used an SMR additive (Stabilised Material for Reinstatement) to reduce the moisture content. A processing plant was set up on site using a specially modified Powertrack 800 screener and mixer and the excavated spoil was mixed with the special SMR Batch-Mix additive to reduce the retained water percentage. Working over a 10 day period, a two-man crew treated all 3,500 tonnes of material, removing the need to send it to landfill.
Andy Bareham, the newly appointed technical support manager for SMR (UK) comments: “Two other options were considered but both were rejected. New material could have been imported to meet immediate project requirements, with the existing moisture retaining soil sent to landfill but this would add transport cost plus increase the environmental impact of the project. Alternatively, the saturated material could have be left to naturally dry for longer on the site, however, this would significantly push back the completion date resulting in costly time delays to the project and there was still no guarantee of a positive outcome and the material could still need to go to landfill.“
The SMR soil stabiliser solution is a specially formulated additive which when combined with the excavated spoil transforms it into a high quality sub-base replacement within minutes. When the SMR material comes in contact with the excessive moisture present within the spoil a chemical reaction commences and ultimately results in a high quality structural reinstatement material being created which consistently outperform traditional materials such as Type1 GSB.
SMR not only dries out and stabilises excess moisture for optimum compaction, but also bonds soil particles together increasing density and strengthening the soil by as much as 600%. A total of ten batches were blended, ranging in size from around 100 tonnes at the start and end of the process, with each of the main batches being around the 400-500 tonnes mark.
“In this particular instance the soil was totally saturated with more than 45% moisture being present so in order to use it elsewhere on the site this needed to be reduced to below 12%,” explained Daniel Richardson, of Richardson Recycling. “Under normal circumstances around 2% of SMR Batch-Mix would typically be added to the soil to stabilise it, but in this instance the soil was saturated. Soil samples were initially taken away for testing and by creating different batch percentages we ensured we got the mix right. When we came back to site the most favourable mix ratio of 4% had been identified and was used when blending the SMR with the soil to guarantee the stability and performance of the material, and this ultimately resulted in the moisture content being reduced to below the required target.”
Compression test blocks were created as part of the delivery process so that cube tests could be taken on each batch and these were subsequently tested. After the initial seven days soil strength of between 2.2 and 5.3 Newton/m2 was achieved, rising to between 4.3 and 8.7 Newton/m2 after 28 days.
“These results were excellent, particularly given the saturated starting point,” concluded Andy Bareham. “This material proved to be highly stable and totally reusable on the site and it was subsequently added to create an embankment as originally intended. Soil strength is a major reason for contractors turning to SMR (UK) when they encounter problems but in this instance the focus was more on reducing the moisture content. We were delighted that our approach was chosen and that it proved to deliver stable and useable soil that resulted in a cost effective solution with minimal additional environmental impact.”
Landmarc Support Services currently manage the Longmoor site on behalf of the MOD and awarded the culvert reinstatement works to Hampshire based R&W Langley as part of the National Training Estate prime contract, with a value of around £550k. The project elements delivered by R&W Langley included completely replacing of an existing culvert, plus an element of pipe sleeving, embankment stabilisation as well as extensive gabion basket and mattress works. This technological additive based solution meant the worn material remained onsite, was used on the project, minimising the additional environmental impact, avoiding multiple vehicle movements and cost significantly less than resorting to landfill.
“Using the SMR Batch-Mix product was by far the preferred and best solution in this instance,” added John Quigley, the R&W Langley operations manager responsible for project. “Not only did it ensure the environmental impact of the project was minimised by negating the need for around 4,000 potential additional lorry movements and the expense of landfill but it also enabled us to keep the project on its original time line. Land stewardship is a key part of the vast majority of projects we’re involved in and we strive to leave every site on which we operate in a better condition than when we arrive.”
Founded in 1999 SMR (UK) has developed and delivers one of the leading technologies to stabilise excavated spoil; cost effectively transforming it into high quality products that outperform traditional materials such as Type1 GSB and this can be reused on existing construction sites, therefore negating the need to send it to landfill.
With its HQ and automated manufacturing facility in Caldicot, Wales SMR provides a national Batch-Mix solution service that enables clients to meet challenging waste management compliance and landfill diversion targets plus decrease their carbon footprint.
SMR (UK) units 10&B, Norman Way, Severnbridge Industrial Estate, Portskewett, Caldicot, Monmouthshire NP26 5PT | Sales Hotline:01252 710772 www.smruk.com