Oblique impact on sand.

By the very nature of its subject, soil mechanics as compared to a modern science is inexact. Of necessity, idealized sections have been assumed in the determination of the various theories which govern the action of a soil. However, in the field all the local vagaries of nature come into play and the resulting heterogeneous mass is difficult to analyse and inconsistent in its properties. Thus, the field or soil mechanics has seen two parallel paths utilized in its development. The theoretical path has led to a fuller understanding of the stresses and strains which affect the soil; but the rigorous application of these theories has not proved completely satisfactory in the field