Gerry Manley, in his article, 'Railways - appropriate technology' (conference supplement, GE January 05) refers to embankment remediation by grouting, including 600 sites in the Great Western Territory.
I took responsibility for design of such works between 1952 and 1989 as the system was developed. I am not aware of a number of medium term failures which Manley alleges.
Over 37 years embankment grouting treatment was regularly and repeatedly requested by headquarters and divisional civil engineers who sought safe track with good running.
These chartered civil engineers (about 50 of them) would certainly have reported such failures to me. The relatively small number of slips over that time implies a successful method.
The accuracy of placing grout of the right type, location and quantity was improved after the 1950s with a change from a 50mm to a 19mm bore tube and angle driving tubes for the upper horizons. This reduced variability in track modulus and improved the transition support from embankment to bridge - one of the few economic systems not requiring track removal.
Success depends on a proper investigation, correct design of grout points, material quantities and supervision. It costs less than a third of classic treatment methods and does not require line closure. The cost increases linearly with embankment height.
In 1979 slips in an 18m high embankment on the up side East Coast Main Line near Durham were priced at £400,000 to treat a 90m length by excavation and recompaction.
My section produced plans and supervised the grouting work which was extended with track grouting on the down side to obtain uniform track modulus on to the adjacent viaduct.
The work cost £51,539 against my section's estimate of £50,000. Grouting is a skill which does not finish when the mix leaves the pump;that is when it starts.
Use of the application stopped because staff skilled in design and supervision were not replaced on retirement in the period before privatisation of British Rail. The grouting equipment went to depot and has not emerged since.
Doug Ayres, Soil Mechanics Engineer British Railways Board (retired)