This study treats the effect of the interaction between underground structures and the surrounding soil in reducin6 the loads transmitted to the structure, the so-called "arching" phenomenon.A continuum theory of soils proposed by G. A. Geniev is applied to a quasi-static, plane-stradn problem of arching. The basic partial differential equations are shown to form a hyperbolic set and are solved by the method of characteristics.Consistent stress and velocity fields are obtained.Comparison with available experimental results shows that the Geniev theory underestimates the surface pressure required for failure of an underground structure in relatively dense granular soils.The source of this difficulty is explained and an atnrovimate method of overcoming it is presented.