Research proves a better solution
Network Rail’s reference design consisted of 1200 tubular steel piles measuring 914mm diameter and with a combined length of 18km, forming continuous retaining structures either side of the embankment. Dry soil mixing uses an augur to whisk cement powder into the ground, creating columns of stiff material.
The technique was previously untried on the UK railway and we carried out research and trials to demonstrate the technique’s viability. Its benefits included plant that could be used adjacent to the live railway and within 2.75m of the overhead lines.
The cost of cement for the matrix of 11,500 soil mix columns was more than 50% less than that of the steel piles. 5500t of cement powder were used compared to 7300t of steel, representing embodied carbon dioxid of 5400t versus 17,600t. The number of vehicle movements to implement the solution were also fewer.
Client: Network Rail