Influence of Storage and Reconsolidation Procedures on Clay Properties

The delay between sampling and testing of clay specimens and the control kept over their volumes during storage are known to affect the strengths and compressibilities subsequently measured in the laboratory. The measured properties are also affected by reconsolidation procedures. This paper deals with reconstituted specimens of illite stored for fixed periods of up to one week, reconsolidated using three different procedures, and then sheared undrained. Results are compared for overconsolidated specimens (OCR = 2) prepared with Koc= 0.53 or 1.0. The paper provides qualitative evidence for the well-known result that the best recovery of stress-strain behavior is obtained from specimens stored at constant volume (undrained) for as short a time as possible and then reconsolidated to their in-ground stress state before shearing. Providing this is done, results suggest that undrained strengths suand Af-values should be recoverable with an accuracy of about ±5 to 6%. Much larger differences can be expected in the relative stiffness E50/su.