Overview

The project scope was to excavate an existing life expired brick arch culvert structure, and surrounding area to allow for the installation of new pre-cast culvert box sections with suitable ground formation and foundations.

The culvert was over a 3 to 1 watercourse, and on a major route into Taunton. A road closure was implemented. The key challenge as with all culvert replacements and remediations is to ensure a fully dry works area.

Scope

Temporary Works

• Deploying road closure for duration of the works.
• Deploying dams and over pump watercourse to create dry
  working area.

Phase 1 – Taking down existing structure.

• Taking up existing coping stones, clean and setting aside for re-use
• Taking down existing parapet walls, cleaning stones, and setting aside
  for re- use.
• Excavating carriageway trench to expose arch barrel extrados and
  allowing sufficient working room.
• Demolition of existing arch barrel, with brickwork disposed of site.
• Taking up existing masonry spandrel walls, cleaning stones and setting
  aside for reuse.

Phase 2 – Preparing for Box Culvert Installation

• Breaking out existing concrete invert and disposal off site.
• Excavating invert to level to receive culvert bed.
• Placing and compacting bed of single sized 50mm aggregate.
• Allowing for some settlement once culvert units are landed.
• Erecting temporary stockproof fencing to corden off working area for
  crane lift of precast units.
• Taking up existing driven timber fencing and steel gate adjacent to
  bridge and setting aside for re-use.
• Taking up adjacent tree saplings where needed and setting
  aside for reuse.

Phase 3 – Landing New Precast Culverts

• Maneuvering units to alignment within trench and joining using
  culvert puller.

Phase 4 – Rebuilding Masonry Elevations

• Casting ST4 concrete footing for spandrel walls either side of culvert
  unit and beneath proposed brick headwall.
• Rebuilding of spandrel walls atop ends of culvert units
  re-using stonework.
• Rebuilding of brick headwall around
  existing highway drainage pipe.
• Rebuilding of parapet walls re-using
  existing stonework.
• Protecting all fresh lime mortar
  with hessian

Phase 5 – Reinstating Carriageway and Making Good

• Reinstatement of carriageway construction to:
• CB16/20 lean mix concrete (150mm min. depth over box unit)
  (Removal and dewatering temporary works once lean mix has set)
• 60mm (minimum) of AC20 binder course. (Profiled to provide a high
  point at the crown and a minimum 1:50 fall in all directions
• 40mm AC10 surface course.
• The total depth of carriageway construction was to provide a minimum
  of 300mm of cover to the top of the box units at all points.
• Re-instatement of driven timber stockproof fencing and steel gate to
  previous condition.
• Re-planting any saplings that needed to be dug out for crane access.
• Removal of temporary stockproof fence.
• Removal of road closure signage

Gallery