Long Itchington – North Portal

Duration:Project Contractor:
Duration: May 2020 – Feb 2021 Project Contractor: Balfour Beatty Vinci
Client: HS2 Value: £4m
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Project Statistics



Site area length


Bulk cut/fill


Aggregate import
Scope of works

  • Site clearance
  • Compound installation
  • Utility protection – gas main crossing & water main diversion
  • Topsoil, upper subsoil and lower subsoil strip
  • Segregation of subsoil classifications in singular stockpiles using a straw chopped marker layer
  • Lime and Cement stabilisation to mainline works
  • Overdig and re-engineer unsuitable gypsum material
  • Working in tandem with SB3’s Soil Nailers
  • Installation of filter drainage
  • Concrete Blinding
  • Construction of CBGM Transitional slabs
  • Construction of bentonite slabs and precast muck bin structure
  • Treatment & Modification of unsuitable bentonite slurry

Project Description

We were first approached by Balfour Beatty Vinci to construct the first major portal excavation at Long Itchington Wood commencing in May 2020. The works involved a mass portal excavation to a depth in excess of 15m, stripping and segregating layers of upper and lower subsoil to adhere to HS2 farm pack criteria & installation of 12 soil nailing/anchoring platforms to reinforce the main portal face.

Following a successful completion of the North Portal we later transitioned onto the South Portal and Bromford East Portal works. These portals involved construction of the diaphragm wall piling platforms to enable the D-Wall portal construction. On these portals Collins proposed a stabilised solution rather than previously intended traditional build ups. Our proposal drastically, reduced the importation of granular sub-base by over 60%, negated the need for geogrid installation and considerably improved the programme of works from 26 to 18 weeks.

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