ANALYSIS OF THE ARCHING ACTION IN GRANULAR MASS

When the lining of a tunnel is more flexible than the surrounding soil, the pressure applied to the fining is in general far smaller than the value estimated from the weight of the overburden. Pressure applied to an underground conduit or a trapdoor is also smaller than the weight of overburden. Similarly, earth pressure applied to a retaining wall or to the timbering of an open cut, and particularly to the lower part of the wall or the cut, is sometimes smaller than the values estimated from the theory of earth pressure. Some studies of this arching action to the soil assume that the soil remains in an elastic state; others assume a plastic soil model with a Tresca yield criterion. In this Paper the stress distribution in the soil is analysed assuming that the soil is in a state of plastic equilibrium and that Mohr-Coulomb's failure hypothesis is satisfied. Results are compared with those obtained by measuring the inner air pressure of models made of vinyl tubes or bags buried in dry sand or gravel.