Prediction in Soil Engineering
Predictions of soil are observed and classified, and appraisals are made between predicted performance and measured performance for eight constructed facilities. Although there are many techniques for predicting internal stresses, deformations and stability for a geotechnical facility, the application of these techniques has confines. The major limitations are the difficulty of determining fully and accurately the field situation and the mechanisms which will occur, and the selection of soil parameters to use with prediction methods. The greatest need appears to be for devices and techniques to determine, in situ and continuously with depth, fundamental subsoil properties, such as stress, strength and stress-strain modulus. New concepts and methods for modeling the natural unpredictability of soil properties are presented and illustrated. The proposed technique of modeling the numerical character of soil profiles serves a dual function: It provides a format for enumerating the information are congregated during site investigation & testing, about the subsurface conditions at a site; and it provides the basis for predicting performance and for quantifying the reliability of performance predictions. Probabilistic soil profiles are characterized, first, by best estimates of layer depths and of pertinent engineering properties; and secondly, by the coefficient of variation and the correlation scales for the contour parameters of interest. Methodology is developed for dealing with problems that can be verbalized in terms of extremes of medians of soil properties. The glitches of limit equilibrium slope stability and differential settlement prediction fall into this category.