The main restrictions were the close proximity of the pile locations to the working airport, noise levels, height restrictions and confined space areas. With this in mind Denver Construction Services opted to install sectional augered mini piles and continuous flight auger (CFA) piles as both systems are non percussive piling methods that generate a minimum amount of ground borne vibration and noise.

The piles designed by Denver Construction Services were 250mm diameter, 300mm diameter and 450mm diameter with compressive loads up to 250 kn (mini piles) and 750 kn (CFA Piles).

Additonal logistical problems facing the project were the miles of electrical cables, fibre optics, and service / drainage ducts that lay at assumed depths below the existing reinforced concrete airport slab areas. To overcome the disastrous consequences of drilling into any live airport services, it was decided that each pile cap location (consisting of 4-8 piles) would be carefully excavated to locate services, and then large diameter ducting pipe would be installed to eventually auger through on completion of backfilling to finished levels.

Each pile cap area was approximately 4.0 mtrs square with hard seawash aggregate reinforced concrete floor areas above each location. To negate the use of high noise level demolition hammers, Denver Construction Services were given the task of Diamond Floor Saw Cutting the reinforced concrete foundation pile cap areas with each cap area cut into approx 20 No sections, which in turn were carefully lifted and removed from site prior to excavation works.

To accommodate both the height and access restrictions associated with the project, Denver Construction Services decided to use its TD 610W mini piling hydraulic rig which although compact in size is actually more powerful than many larger rigs twice its size. The rig itself was designed to drill holes up to 500mm diameter and with its 100mm diameter hollow main shaft in the rotation head allowing concrete to be pumped directly to the bottom of the hole if required, it made the TD 610W rig the ideal machine for CFA and mini pile drilling

Prior to commencement of augered drilling works it had been assumed by information provided, that the ground conditions would consist mainly of clays and chalk. However during auger piling a very hard flint was found to be present throughout the ground strata.

The flint itself was so hard that conventional lead auger shoes were unable to penetrate the strata without causing auger damage.

To overcome this problem Denver Construction Services had special Rock Ripper Lead Augers with Tungsten Picks manufactured which enabled them to successfully drill through the hard flint strata and onto the pile depth required.

After drilling, one of the major additional problems facing Denver Construction Services was the concrete infill construction of the piles. Because of height and access restrictions Denver Construction Services had to use high pressure concrete pumps and tankers to pump concrete to distances ranging from 25.0 mtrs up to 50 mtrs with roof access sometimes the only viable solution.

Throughout the project, Denver Construction Services engineers carried out Simbat Dynamic Load testing, Integrity testing and concrete cube testing on specified piles as instructed by the main contractor.