A study was undertaken to determine some of the chemical and mineralogical characteristics of the Alberni Slay, a Vancouver Island soil which is the representative of the concretionary Brown Group of soils. Chemical analyses showed that iron, silica and aluminum are leached from the profile and though considerable quantities of these elements are precipitated on the surfaces of peds in the deeper horizons of the soil, no horizon of accumulation was formed. The retention of iron in the surface horizon in the form of free iron oxides maintained the percentage of iron in that horizon comparable with the percentage in the C horizon, and resulted in the formation of highly stable concretions in the A-B horizon of the soil. The formation of concretions seemed to have been influenced by the high magnetite content of the soil. The interaction between the positively charged surface of the magnetite particles and organic anion complexes of the cations of the first transitional series impeded the movement of these complexes through the slowly permeable soil and permitted absorption and precipitation to form concretions. The x-ray analyses of the clays revealed a weathering sequence in which chlorite was developed, from weathered primary minerals. The formula for the chlorite separated from the surface horizon clays was calculated and it was found to be a dioctahedral Al-chlorite which had been predicted by Grim and by Brindley, but which had not been previously identified in soils. / Land and Food Systems, Faculty of / Graduate

The study was undertaken to investigate the effects of rate of strain and structure on the development of true cohesion and true friction in a saturated cohesive soil. The soil investigated was a locally available sensitive clay. The various methods proposed by different investigators to measure true cohesion and true friction are reviewed. After some trials the method adopted was that proposed by Bishop (1962) in which over-consolidation is used to obtain samples at the same void ratio but different initial effective stress. All samples were tested in undrained triaxial compression. To investigate the effects of rate of strain on the development of true cohesion and true friction, the results were compared for two identical sets of samples tested at two significantly different strain rates. To investigate the effects of structure on the development of true cohesion and true friction, a technique was developed to remold the specimens in place at constant void ratio after they had been sheared in the undisturbed state. Remolding has the effect of breaking-down the structure of a sensitive undisturbed clay. The test results from undisturbed and remolded samples were compared. In general the investigation showed that in the undisturbed clay the strength in terms of maximum (Ϭ₁-Ϭ₃) decreased with decreasing strain rate, however, the strength in terms of (Ϭ⁻₁/Ϭ⁻₃) max, was not significantly affected by strain rate when compared on an effective stress basis. In remolded clays there was a tendency for the strength in terms of maximum (Ϭ₁-Ϭ₃) to increase with increasing time to failure. In the undisturbed clay true cohesion developed rapidly at small strains, attained a peak and decreased to zero at large strains. True friction was mobilized slowly and attained a maximum value at large strains. At strains less than 8% both true friction and true, cohesion increased with increasing strain rate. However, at large strains true friction and true cohesion were not affected by strain rate. In the remolded clay true cohesion developed slowly attaining a small but significant value which remained constant with strain. The maximum value of true cohesion in the remolded clay was very much lower than that for the undisturbed clay. The development of true friction with strain was essentially unaffected by remolding and both the undisturbed and remolded clay developed about the same maximum value of true friction at large strains. The observed behaviour was explained in terms of changes in clay structure with strain rate and remolding. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate