MECHANISM OF WATER ATTACK ON DRY COHESIVE SOIL SYSTEMS

Abstract

The mechanism of such attack has been analyzed theoretically and on the basis of data obtained on 5 natural soils and on a number of their homoionic modifications. 2 main factors appear to govern the consequences of the water attack: the driving force or the affinity of the internal soil surface for water, and the cohesive forces holding the system together; the relative magnitude of these forces determines the general reaction picture. The speed with which the particular reaction occurs depends to a great extent on the permeability of the soil system and on the ease with which free and adsorbed gases may escape from the pore space. If this escape is prevented, a type of failure may occur which possesses great similarity to an explosion, although, of course, not liberating so much energy. The concept that the driving force is the affinity of the internal surface for water makes it easy to understand why certain moist cohesive soil systems may be exposed to free water for any length of time without observable change. The affinity for water is satisfied in such systems. The exptl. data obtained appear to substantiate the developed theory as far as the erosive soils are concerned. As to the nonerosive soils, the exptl. techniques now available do not furnish all the information necessary for testing the theory, but no fundamental reasons why the general theory, as developed in this paper, should not hold for all types of cohesive soils appear to exist.