Landpac Ground Engineering Limited is working on the Trailblazer Project at the former Polkemmet Colliery, proving that where there's muck, there is indeed brass.

LANDPAC is a leading international ground improvement specialist with a tradition for innovation and excellence dating back to the 1990’s. The company provides the construction industry with specialised technically advanced solutions to improve the engineering properties of in-place soils at depth.

More recently, Landpac has revolutionised in-situ ground improvement with the introduction of the unique High Energy Impact Compaction (HEIC) application and the enhancement of its Continuous Impact Response (CIR) and Continuous Induced Settlement (CIS) monitoring systems, available to clients since the late 1990s.

Landpac HEIC application is an effective mechanism for executing a controlled process of dynamic loading to considerable depths, directly onto deep in-situ fills and weak natural soils. HEIC is suitable for brownfield and problem ground development sites within the industrial, commercial and residential development industries.

Landpac CIR, meanwhile, digitally records real time soil response during the HEIC process. Each impact is recorded, relative to its position on site as determined by an integrated GPS system. Actual soil test results obtained at specific locations can then be applied to the entire site, effectively monitoring 100 per cent of the site during the HEIC process. The CIS fulfils a similar role, but it measures induced settlement during the HEIC process.

Landpac HEIC treatment with CIR verification and CIS monitoring offers the benefit of a monitored uniform application across treated area, achieving significant effective depths of improvement and considerable increases in the in-situ soil strength.

A major project for the company recently has been its remediation work on the Polkemmet site in Whitburn, one of the largest brownfield regeneration sites in the UK, and the largest in Scotland. Since 2004, the developer Ecosse Regeneration has been retrieving coal on the vast former colliery site, and the completed site will act as a development platform for new homes and sporting facilities.

Managing director Dermot Kelly takes up the story: “The site is a perfect brownfield example. The total site covers over 500 hectares, and before the drive to regenerate it, it was essentially worthless. The ground was unstable thanks to open mineshafts and discarded surface materials, while the site was full of burning ‘bings’ – coal that had probably been smouldering for 40 or 50 years.

“Ecosse Regeneration have been retrieving the coal for the last four years, though only about two or three per cent of the dig is coal, so we need to put the other useable materials back. The average dig depth is 40 metres, and then we place and engineer, by High Energy Impact Compaction (HEIC), the earth in one metre layers. Ultimately, when the land has been made good again, it will, over the next 15 years, go on to be home to 2,500 houses, basically a whole new town, on the North side of the site, while the South side will house two PGA golf courses.

Our own reclamation work is scheduled to be completed in 2009, and it’s fair to say we’re pretty much at the tidying up stage now. Ecosse Regeneration finished extracting the coal, but there are still a few holes to fill.”

As well as the coal, the site comprises glacial clays and deposits of sandstones, mudstones, shale and siltstone, all of which had to be excavated and the coal mined and removed. Following completion of the mining operation, the resulting holes are backfilled using CAT 777 dumpers with the materials spread in layers of up to 1.2 m in thickness. The layers are then compacted using either LANDPACs 3-sided or 5-sided HEIC units.

The use of LANDPACs HEIC system has resulted in cost savings and programme reduction due to the following:

• The ability to place fills in lifts up to 1.2 m thick.
• Speed of HEIC units allow the compaction of up to 50 000 m3 per week (using two HEIC units).
• Reduction in effort spreading layers.
• Increase in maximum allowable particle size due to the use of thick layers.
• Reduction in exposure and deterioration of soils.
• Reduction in verification testing due to the use of LANDPAC’s Continuous Impact Response system allowing better targeting of test locations.

Verification testing is then carried out at the site under the supervision of the consulting engineer, WA Fairhurst & Partners, for the works. The testing includes insitu density testing using nuclear density tests and sand replacement testing, plate load testing, zone testing and monitoring of settlement pins.

The testing is carried out with the benefit of LANDPAC’s Continuous Impact Response mapping system which allows the engineer to target the testing at the most critical portions of the site, mainly those areas which are indicated on the CIR maps as being weaker than the surrounding soils.

This ability to target the testing is resulting in the test programme being cut by 50 per cent over what was originally envisaged.

The specification for the works require a dry density of 95 per cent of standard proctor to be achieved, and, so far, the results of the testing to date are confirming compliance with the specification.