Detail Design of Blackfriars Gas Main Diversions under the District & Circle Line, London

The Thames Tideway Tunnel (TTT) involves the construction of a 25 km (16 mile) tunnel running under the River Thames. This will provide an upgraded system to intercept, store and transfer raw sewerage and rainwater discharge that currently overflows directly into the river. Construction work commenced in 2016 and the target completion year is 2022.

A damage assessment undertaken by the client concluded that a section of the National Grid Gas mains running within the Victoria Embankment service subway would fail because of the main tideway works. The gas mains comprise a 36” cast iron low pressure (LP) and a 36” cast iron medium pressure (MP) pipe, both of which will have to be diverted prior to commencement of the main tideway works.

Rendel Limited has been engaged by the diversion works contractor, Barhale Limited to undertake the structural (shaft and tunnels) and geotechnical design for the proposed gas main diversions in accordance with their previously completed feasibility study.

Rendel is currently producing the detail design for the diversion of two gas mains through two vertical shafts and connecting micro-tunnels.

Our role includes:

  • Review of existing available ground investigation
  • Assessment of design soil parameters, ground profile, groundwater and potential ground related hazards
  • Analysis in PLAXIS 3D
  • Designing of shafts, shunts and micro-tunnels
  • Designing the construction sequence
  • Designing the diversion of all affected services and utilities
  • Developing of geotechnical and structural 2D and 3D models
  • Developing a monitoring plan