A SIMPLE STATISTICAL APPROACH TO DIFFERENTIAL SETTLEMENTS ON CLAY

This thesis develops a simple procedure for using stochastic parameters in the consolidation equation to calculate a range of anticipated settlements for specific conditions at Bay Mud sites. The procedure permits consideration of the effect of secondary compression and a desiccated crust on the value of the settlement calculated. The factor of aging is found to be significant for light fill loads on crusted Bay Mud. A parameter called the coefficient of preconsolidation is developed to allow consideration of variations in preconsolidation over large areas. This parameter is found to be unnecessary to obtain good results for small areas. The calculated ranges of settlement are compared to observed settlements at several sites in the San Francisco Bay Area having varying conditions. Agreement between calculated ranges and observed settlements is found to be good. The procedure is extended to the case of absolute relative or differential settlements. Differential settlement is considered to be the sum of a stochastic component and a deterministic component. The value of differential settlement calculated is considered to be the maximum value which should not be exceeded about two thirds of the time. Comparisons are made between observed and calculated differential settlements for the sites previously studied. Agreement is reasonable. The procedure has the advantage of permitting evaluations to be made at a particular time after the start of the consolidation process.