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Hybrid Pile

Hybrid Pile. Definition A pile installed by combining driven and auger/drilled techniques. Why use a ‘Hybrid’? by incorporating a ‘driven element’, the pile installation costs are significantly reduced.

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Hybrid Pile

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  1. Hybrid Pile • Definition • A pile installed by combining driven and auger/drilled techniques. • Why use a ‘Hybrid’? • by incorporating a ‘driven element’, the pile installation costs are significantly reduced. • On many occasions in the UK and further afield expensive drilled solutions have been adopted where a cheaper and quicker hybrid solution would be more economical.

  2. Case Study 1 • Major Bridge Project - Scotland Problems • Concerns with vibration and ‘drawing in’ of granular material with temporary cased auger/sub-artesion pressure causing blow back into pile bore • 3.5m headroom Solution • 344mm dia temporary cased and 300 dia auger in upper 4m - casing advanced ahead of auger. Install closed ended steel tube 273 dia then bottom drive to set at 15m.

  3. Case Study 2 • Rail Project - Scotland Problems • Very dense material in upper 5-6m (SPT 30-50), major obstructions, overlying very loose material (SPT<5), rockhead at 25m. • Vibration Solution • In upper 6m we used a Symmetrix concetric ODS to penetrate dense material/obstructions. • The base of the pile was grouted to form a 1.5m deep plug. Pile was then left for three days, drained then bottom driven keeping vibration levels <8mm/sec (PPV).

  4. Case Study 2 • Static Load Test Results 4 • Pile vertical load capacity of 3250KN was held but pile reached its serviceability level at around 2.75 x working load (2750KN). • The pile also withstood a significant horizontal test load of 300KN although its serviceable limit was reached at approx 2.0 x working load (200KN).

  5. Case Study 3 • Environmental Project Problem • Highly contaminated ground Solution • Proposal is to install a 323mm dia bottom driven steel tube installed to rockhead at approx 3m below ground level. Pile toe is sealed using a 0.5m deep concrete plug. • Concrete plug will then be drilled out using water flush rock roller to form 3m long x 250 dia socket • Solution has to cater for seismic event.

  6. Hybrid Advantages • Environmental Impact • reduced spoil • mitigates risk of grout seepage • low vibration • Cost Effective • due to driven pile element • Versatility • can be employed in a wide range of ground conditions

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