Project outline

Murphy Ground Engineering (MGE) was engaged by Tide Construction Ltd to construct a Secant Piled Wall to form the double basement excavation and a Bearing Pile Solution to support both high rise cores for the accommodation blocks.

The works included:

  • Carrying out piling using a Llamada P140-TT CFA piling rig and Bauer BG30 Rotary Bored piling rig.
  • Executing a Secant Wall using the CFA technique and Bearing Piles using both the CFA technique and the Rotary Bored technique.
  • Pile diameters ranged from 450mm to 900mm and piles ranged in length from 10m for some temporary works retaining solutions to 32.0m deep for the heaviest loaded piles.

On completion, the 101 George Street development will comprise two of the world’s tallest towers built using modular construction, at 44-storeys and 38-storeys. The towers scheme, drawn up by HT Design, will be worth over £150m and will be a trailblazer for modular construction methods. Presently, the tallest prefabricated building in the world is a 32-storey block in New York. Tide is both a development and contracting company, and has delivered several projects in recent years using its off-site manufacturing system, Vision Modular Systems.

Project delivery and innovations:

To manage the site constraints and accessibility conditions, concrete was delivered to the concrete pump and agitators on the working platform by a boom concrete pump situated on College Road.

To enable Tide to take advantage of bulk excavation programme savings delivered during piling, MGE designed and delivered Contract Lifts to remove both rigs from the excavation, thus removing the need to leave exit ramps on site to facilitate demobilisation. The rigs were lifted straight onto waiting transport and demobilised.

Key challenges

George St was a very challenging project logistically. Due to planning constraints, George St could not be used for site access, meaning materials could only be brought in via College Road. Good coordination with Tide Construction Ltd was key in order to keep the remainder of the site running smoothly and keep good concrete supply to both rigs.

Programme challenges meant that there was a lag in design information. Collaboration between stakeholders was key to ensuring quick turnaround of design of the various elements of the project to ensure that the critical path of the project was unaffected.

Complex logistical and lifting operations were necessary to remove the large plant from the site once piling work was complete.

Mobilisation of a 13 Mega newton Load Test Set-up to carry out Maintained Load Testing on 2 No. piles to verify that the parameters built into the pile design were correct.

Key facts
  • 306 900 Male/750 Female Secant Wall Piles
  • 350 450, 600, 750 & 900 Ø Bearing Piles
  • Project Value - £2.5m
  • Approximately 6000 cubic meters of concrete placed.
  • Approximately 150 tonnes of reinforcement placed.
  • 7000 Man-Hours of Labour utilised on the project.
  • Programme duration of 19 Calendar Weeks
  • Llamada P140-TT piling rig working on 900/750 secant wall with Bauer BG30 commencing bearing piles.
    Llamada P140-TT piling rig working on 900/750 secant wall with Bauer BG30 commencing bearing piles.
  • Llamada P140-TT piling rig being removed from excavation by Contract Lift.
    Llamada P140-TT piling rig being removed from excavation by Contract Lift.
  • 13 MN Load Test Set-Up.
    13 MN Load Test Set-Up.

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The Ground Engineering team at Murphy offers in-house pile design, value engineering and bespoke technical solutions throughout the UK and Ireland. We have a proven track record of successfully delivering both minor and major works across a range of sectors.

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