Lyon Way, Frimley Flood Alleviation Scheme


Clients: J Murphy & Sons and Thames Water 

Duration: 12 weeks 

Location: Lyon Way, Frimley

            


Description of works: 

M&A Roarty Construction, working for J Murphy & Sons have completed
a 15m diameter caisson concrete segmental shaft, 13.5m deep, at
Lyon Way.  The shaft included a 2m x 3m collar and a 3m deep plug, 
which formed part of the permanent works for anti-flotation.

A driven sheet piled wall was installed to allow excavation of the collar,
without the requirement for secondary waling systems for either the 
excavation itself or to support the adjacent crane pads.
 
Two stage dewatering was required. The upper aquifer within the river
terrace gravels deposits was dewatered using a conventional system 
with well-points installed within the pans of the sheet piles.

The lower level within the Camberley Sands/ Windlesham formations was
dewatered using an ejector system, installed to 28m deep.

Dewatering was used in preference to sinking the shaft under wet 
conditions, to remove the risk of settlement to the adjacent rail lines 
or highway structures.