Tideway Batching Plant

Chambers Wharf is one of Tideway’s main drive sites. Shotcrete was on site at Chambers Warf (CHAWF) simultaneous construction of two adits and associated sprayed concrete batching and to supply concrete for the shaft slipform.

After extensive research Shotcrete opted for a McCrory MCM 60 plant capable of mixing up to 50m3/hr from a very small footprint. The plant is exceptionally compact and mobile and can be delivered and set up in a single day as it hydraulically unfolds into position. The fully integrated electrical and constituent dosage setup leaves only the installation of silo feeds into the hoppers to be completed. The whole unit can be set up, calibrated and fully operational with 5 days. This major benefit reduces the man hours required on site, minimizing work from height risks and eliminating typical commissioning issues.

The concrete is mixed by a 1.6m3 capacity twin shaft mixer. The plant is controlled by the Practicon software system that is programmed with all the required mix information. During the concrete production the batcher can monitor the control screen which shows each constituent flowing into the mixer, the mixing operation and the discharging of the material.

The plant operation is fully triple ISO certified and concrete carries BSi Kitemark™ product certification.

CHAWF operated on a 24/7 and 24/5 shift patterns to allow for continuous progress in slipform and both adits through alternating operations. Resourcing multiple specialist roles within a challenging environment became even more constrained when the CoVID-19 pandemic struck halfway through the project.

The first contract for this plant was to supply 7000m³ of a high performance Slipform mix which was used to line the previously constructed diaphragm wall. We worked extensively with the Client, Slipform contractor and material suppliers to achieve the correct mixes, responding rapidly when changes were required.

The second contract for this batching plant was for the supply of the material for the sprayed concrete lining to a set of launch and reception chambers circa 10m in diameter with Shotcrete taking on the full package of Tunnelling works and the supply of sprayed concrete materials. Concrete was delivered to the spraying unit using a combination of all terrain mixers and concrete skip to transfer the material to pit bottom. Due to the unexpected ground conditions the mix had to outperform its initial trialled specification to deal with water ingress and inflows of material.

Added to task of batching high specification concrete inside an acoustic shed, on a small footprint, while working underground, under the river Thames, several technical and the logistical challenges had to be overcome to ensure the smooth and safe progress of this critical path project activity:

• Balancing reduced storage capacity with minimising traffic movements
• Receiving just-in-time constituent deliveries via barges, tankers and NTT articulated trucks in a confined space (extensive swept-path analysis were needed to achieve the optimum layout)
• Managing stock levels to ensure continued production over long weekends
• Scheduling maintenance activities as not to disrupt production
• Consistently achieving J2 modified strength curve with 28 day strength of 40MPa

Remarkably, despite the multitude of challenges in the middle of a first wave of a pandemic, the project was handed over snag free two weeks ahead of schedule and without incident.