Ground freezing plant to rescue the stalled Portsmouth sewer was being assembled last month as British Drilling & Freezing moved onto a site in the city. The firm has been subcontracted by main contractor Edmund Nuttall to stabilise a 20m long section of the tunnel which has cracked and deformed concrete lining segments. Nuttall was forced to stop work on a 4km long TBM drive at the end of May after discovery of the problem. An inspection under low pressure compressed air showed some fifteen segment rings will need to be replaced. Segments show the lining has squatted with tension cracks in the crown and compression cracking below.
