Laboratory Measurement and Interpretation of Soft Clay Mechanical Behavior

This paper describes laboratory methods for measuring soft clay stress-strain-strength behavior and interpretation of test results for selection of design parameters. The paper traces the major practical contributions of experimental research to our understanding of soft clay mechanical behavior. Recommendations are given for implementation of research results in practice with the goal of improving the engineering state-of-the-practice, which often lags well behind the research state-of-the-art. Particular emphasis is given to the results of work produced by researchers working at the Massachusetts Institute of Technology under the leadership of Professor Charles C. Ladd. Significant advances in the understanding of clay behavior have been realized in the past 40 years including such issues as the influence of anisotropy, stress history, rate effects, and sample disturbance. Of these issues, sample disturbance remains by far the most difficult one to deal with in practice and in fact is often ignored. Field sampling and laboratory techniques that can reduce sample disturbance are described together with methods for quantifying sample disturbance. The merits of laboratory reconsolidation methods are discussed and are demonstrated through the use of three case studies ranging in sophistication in sampling and laboratory testing from the highest level down to the level more commonly encountered in practice.