Bonding, Effective Stresses, and Strength of Soils

The theory of rate processes has been used to deduce values of interparticle bond energies and the number of interparticle bonds in different soils from the results of creep tests. Measured values of activation energy for creep are of the order of 30 kcal to 45 kcal per mole. The effective consolidation pressure was found to be directly proportional to the number of interparticle bonds per unit area of cross section. A single linear relationship was found to hold between the number of interparticle bonds and compressive strength which applies equally to wet and dried remolded illite, undisturbed normally consolidated and overconsolidated San Francisco Bay mud, and dry sand. These results support the hypothesis that the interparticle contact is the only significant region between soil grains where effective normal and shear stresses can be transmitted, interparticle contacts are effectively solid to solid, a single interparticle contact may contain many interparticle bonds, and the number of bonds per contact depends on the compressive force transmitted at the contact.