Crooked Brook near Gatwick

Client – AMCO RAIL 

EMERGENCY CALL OUT – Eden Bridge, near Gatwick.

There was an embankment circular slip/rotation which  caused damage to a culvert which runs diagonally under the tracks. The purpose of the works was to insert a Weholite HDPE pipe through the deformed culvert and fill the annulus with micro-concrete to stabilise the structure. 

  • A tirfor was installed outside the upstream end of the culvert to facilitate installation of track and pipe
  • A sump was created on the upstream end of the culvert by others and the water course was diverted through the pipe to allow a relatively dry working area.

Installation of pipe into the Culvert

  • To assist with the installation of the HDPE pipe, a pre-fabricated track was laid on the invert of the culvert. 
  • The track was assembled outside the culvert and pulled through one section at a time from the downstream to the upstream using the tirfor wire. 
  • When a suitable number of tracks had been pulled through the culvert, the pipe was lifted into position with certified lifting strops by the 21T excavator. 
  • A pulling bar was placed across the rear face of the pipe and the tirfor wire was connected to the pulling eye. 
  • Under manual control, the pipe was pulled through the culvert until the rear face was just outside the culvert entrance 
  •  A second pipe was lowered into position then attached to the first with steel fish plates to prevent separation during installation; the rubber connection band was then  positioned over the joint. 
  • The pulling bar was re-positioned over the rear face of the second pipe and the process  repeated. 
  • When the pipe sections reached the end of the track, operatives could walk through the new pipe sections and continue to lay more track on the invert within the safety of the pipe, as they did, the pipe was pulled through until the culvert had been re-lined.

 

AMCO RAIL

 

Installation of pipe to damaged Upstream Entrance

  •  Due to the condition of the arch on the upstream entrance, a smaller diameter pipe was inserted through the large pipe and positioned under the collapsed area. 
  • This allowed the damaged section to be removed carefully and re-built by others. 

Grout installation to the annulus

  •  When the pipe installation was complete, timber formwork was  placed on the upstream and downstream ends of the pipe. 
  • Grout injection points were inserted through the formwork and installed at pre-determined locations along the inside of the pipe. 
  • A 2nd pipe was inserted into the formwork and protruded vertically above soffit level to act as a ‘tell tale’, when the grout discharged through this 2nd pipe it  concluded that the annulus was full. 
  • The structural grout mixture consisted of a P555 cement and sand design with no aggregate to allow it to flow freely in to all the voids around the pipe.
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