Project Brief

A section of the railway track needed protection against bank erosion. There had been several small slips which had resulted in a timber post and sleeper retaining wall being constructed – this was in the process of collapsing on to the S & T trough route.

Marshalls Civils & Drainage solution

A precast concrete modular block retaining wall was designed to replace the existing solution, the modular design allowed for short sections (4-6 metres) of the proposed concrete block wall to be constructed at a time, thus eliminating the possibility of damage to the S&T route.

The installation gang consisted of three men and an excavator (with an operator). The Redi Rock blocks were transferred to the worksite by a Road Railer towing a trailer, under the supervision of a machine controller. Excavated material was removed from site using the same recourses. One of the three-man gang was tasked to act as a slinger; blocks were removed from the trailer to be placed into the Redi-Rock modular block wall by the excavator. In this instance the foundation was constructed using compacted lean-mix concrete.

All works were completed during night-time possessions, with less than a four-hour working window. The wall was easily built by just two men and an excavator.

The location of the wall also suffered from ingress of water from natural springs and fissures in the rock. Due to the nature of the Redi-Rock modular blocks, temporary control of the water was easily dealt with by forcing the water around the blocks to the existing track drainage by forming small bunds.

The works were completed on time with shift targets being bettered on many occasions.

The design called for a second wall constructed behind the main wall with a small void between the two walls, which was filled with concrete. This greatly reduced the volume of loose material which would require compacting, thus increasing the works to be completed within the placed possession programme.