\ Akkerman GBMs Aid London’s Crossrail Project

Akkerman GBMs Aid London’s Crossrail Project

Akkerman GBMs Aid London’s Crossrail Project Crossrail, the mammoth transportation project in southeast London, involves the installation of 42 km of tunnels and 10 underground railway stations, linking new to existing railway services for the United Kingdom’s Department for Transport. Two Akkerman GBM systems with Eliminator tooling are being employed on this project to complete small but essential drainage functions, contributing to the overall integrity of the design.

Terra Solutions Ltd. was hired by Bam Ferrovial Kier JV to install a 37 m drainage pipeline in a large tunnel shaft wall in early 2014 on the Farringdon Station C435 project of Crossrail. This marked the first instance of use of a GBM system with an Eliminator on Crossrail.

Shortly thereafter, five short drainage lines ranging from 8 to 15 m were installed with the Eliminator by subcontractor Chiltern Thrust Bore on Crossrail projects.

Akkerman GBMs Aid London’s Crossrail Project Contractor Hochtief Murphy JV was awarded a project on Crossrail which encompassed the Plumstead to North Woolwich connections. They required a solution capable of installing 37 and 62 m drainage tunnels from sumps in the tunnel’s inverts to a drainage main in the platform of the tunnel’s cross-passage at exact line and grade.

The solution had to be able to excavate geology that contained chalk dispersed with high n value hard flints.

Additionally, the tunnel region, located under the River Thames, had a water table tested at 4.5 bar. The system and ancillary equipment had to be sized appropriately for transport into the restricted cross-passage and fit in a 3 m shaft. These factors made the Akkerman GBM system with the Eliminator the most ideal equipment choice.

The Eliminator tooling is able to excavate non-displaceable ground conditions and installs pipe in a two-step process. It concurrently pilots an accurate course while the cutter face excavates the ground, eliminating the requirement to first install pilot tubes. Spoils are transported through casings and augers and travel to the launch shaft for removal. The Eliminator features three independent steering control shoes to maintain line and grade accuracy.

Hochtief Murphy JV hired GBM equipment, the expertise of a technician from Akkerman’s U.K. distributor, Tunnel Engineering Services Ltd. (TES), and an experienced GBM equipment operator from B & W Tunneling, a long-time Akkerman customer. The TES technician provided Eliminator training for the B&W Tunneling operator and Hochtief Murphy JV crew in order to run two shifts for the duration of the project.

The product pipe was a 300-mm ID clay Naylor Denlok pipe with a reinforced pipe joint, finished with a pressure grouted annulus to meet project requirements.

First up was the shorter 37 m drive. The GBM 308A jacking frame was disassembled, transported and reassembled in the shaft in the cross passage. The Eliminator was launched through a pit seal in January 2015. Despite the seal, the production rate was sluggish due to the influx of large amounts of ground water in the shaft.

At one point a misalignment occurred that could not be corrected and the Eliminator was pulled back to the launch shaft. Since the Eliminator is predominantly designed for non-displaceable rock vs. high water table conditions, it was discovered that water penetrated the seal and entered the unit’s electronics causing the misalignment. Upon repair of the electronics and resealing, the unit was re-launched. The crew was able to persevere at a respectable pace and completed the bore on grade.

Knowing what to expect from the tooling in these ground conditions significantly increased the crews’ installation rate on the second bore. They launched the Eliminator again in early February 2015 and were able to complete the 62 m drive in four, 12-hour shifts.

Currently, 10 GBM and Eliminator drainage bores totaling 73 m with the same pipe specification are being installed by Terra Solutions Ltd. for contractor Dragados Sisk JV on the C305 Limmo Peninsula Cross Passage Drainage of Crossrail. They began in November 2014 and anticipate completion in summer 2015.

Once Terra Solutions completes these bores, Crossrail will contain a total of 22 GBM system installed drainage alignments.

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