KTP dewatering system

Pipe jacking is a trenchless technology used to install utilities below the surface with minimum disruption to the ground surface. There are three interrelated processes in pipe jacking: firstly the excavation of the soils through which the pipe is being jacked; secondly the transport of the excavated soils to the surface using slurry; and thirdly the dewatering process which removes the soil particles from the slurry.

As the soil at the face of a tunnel is excavated a pipe is jacked forward to prevent collapse of the tunnel. The excavated material is mixed with water to create a slurry which is transported back to the surface. The slurry is passed through sieves and hydrocyclones to remove as much of the solids as possible during the pipe jacking process. The fine particles are removed by an offline process in which slurry treated with additives is passed through a centrifuge.

GCG took part in a Knowledge Transfer Partnership (KTP) focusing on the dewatering systems used to separate the solids from the slurry. The KTP was part-funded by the Department for Trade and Industry and included reviews of current management and procurement processes, direct involvement in and observation of dewatering processes on various sites, laboratory testing, and controlled testing using a scaled-down centrifuge. This KTP has led to an improved understanding of the solid separation process in the pipe jacking industry and has developed a logical approach to identifying and using effective and efficient dewatering systems, thus sharing best practice and introducing innovation into the process. The partnership was also able to produce a number of technical papers, guidelines and presentations to inform the industry and clients of the issues and how best to overcome those issues. Through initiatives like this KTP, GCG have been able to maintain its position at the forefront of technical knowledge.

References

Phillips, N. (2010). Refining the Art: progress made in the development of slurries and on-site slurry plants used for pipe-jacking projects. World Tunnelling, October 2010.

Phillips, N. (2012). A process of separation. Trenchless World, Jan/Feb 2012.