Introduction

Abstract

This symposium serves three important purposes—first, it illustrates the wide range, variety, and character of consolidation problems encountered in soil and foundation work; second, it presents the different approaches and consolidation testing techniques used in the analyses of these problems; and third, it advances the knowledge and understanding of the nature of consolidation phenomena. The authors of these papers are particularly well qualified to write on this subject through the many years of practical experience in soil and foundation work from which they have drawn these interesting cases. Certain important facts should be quite evident. In each case the methods used in the consolidation tests differed in certain important respects, which were essentially related to the specific problems involved. Also certain fundamental principles of consolidation testing are discernible. It is important to consider and to understand clearly why these basic differences in consolidation testing methods should be necessary and what fundamental principles are applicable as a basic framework for consolidation testing methods. The obvious and essential purposes of consolidation testing of soils are to investigate and to determine the consolidation stress-strain and time-consolidation properties of soils; these data are directly needed for making reliable estimates of settlements of structures. The principal difficulty encountered, however, in the consolidation test and in fact in all soil property tests, is that of making observations and measurements of such properties under conditions reasonably identical to those to which the soils are actually to be subjected in soil and foundation work. This difficulty is created first by the removal of soil samples from their natural environment and natural stress conditions; second, by soil disturbance effects accompanying the sampling operation in the field and the sample preparation in the laboratory; and third, of greater importance the fact that during the observation and measurement of properties in a soil test the observed property itself is changed by the test methods used, frequently to an important and unknown degree. The observed and measured properties are those of the soil changed and modified by the conditions imposed in the test, not necessarily those having a significant and direct relation to the actual properties of the soil and to the actual conditions in the natural situation. It is within the range of elastic behavior only that the properties of materials are not affected by the conditions imposed in a test, and that tests can be relied upon to yield results which not only have a high degree of consistency and reproducibility but also have well established, constant, and predictable relations to the actual behavior and performance of the materials under service conditions in structures. This is true in general for the common structural materials because they have uniform, constant, physical properties within the range of common usages and of working stresses below the elastic limit, and because these properties are practically unaffected by the common stress and other conditions to which the materials may be subjected during and subsequent to construction of structures and in service. The principal objectives for testing structural materials for use in structures are to determine the uniformity, quality, and acceptability of such materials manufactured or processed in large quantities to definite specifications. These are the basic concepts involved in the standard test approach and they constitute the principal justification for its use in the case of the common structural materials. Under such conditions standard testing procedures can be straightforward readily applied statements of techniques for the conduct of a test, which have a general application to all of the common design and construction problems. Such test procedures as a consequence involve practically no elements of uncertainty and require little or no judgment in their application.