Discussion

SESSION 7

N.T. LONG, Laboratoire Central des Ponts et Chaussees (LCPC) I want to give you some information about the improvement of walls. Ten works using Pneusol to reduce active earth pressure are known to have been built in France. The first of these structures, built in, 1986 is a cantilever retaining wall, 54 m long and 5 m high, founded on two rows of piles. Before filling behind the wall, the contractor became aware that the shell of the wall was too thin. 'Heavy' Pneusol was used to relieve the active earth pressure and also to eliminate tensile forces on the piles. It was made of treads arranged in layers and tied together with polyester tapes. Since the fill inside the treads exerts no active earth pressure and that between two layers it is highly confined, the Pneusol mass, provided that the spacing between layers is small, behaves like a gravity wall made up of thousands of tiny gabions stacked one on top of the other. But the structure most like those used in the tests is that of the Fonderie Wall. One hour before work to widen a heavily travelled road was begun, this 18th centruy wall was classified as a historic monument, so it could not be demolished. It is made up of more or less closely spaced blocks. The