A comparison of the behavior of intact and Resedimented Boston Blue Clay (BBC)

Abstract

Resedimented Boston Blue Clay (RBBC) has been used as an analog test material for research at MIT for decades, due to local variability and the high cost of sampling. However, a comprehensive study of the differences in behavior between intact and resedimented BBC has not been completed recently. This thesis analyzes test data from laboratory CRS and triaxial tests conducted at MIT on intact and RBBC. Typical ranges for compression ratio, hydraulic conductivity, coefficient of consolidation, lateral stress ratio, preconsolidation pressure and peak friction angle of RBBC were within ranges for intact BBC. Ranges for secant friction angle, swell ratio and undrained strength for intact BBC overlapped and were lower than ranges reported for RBBC. Both intact and RBBC CRS data plotted to the right of the sedimentation compression line (SCL) in the Burland (1990) framework, showing significant structure and clay fabric. The Jaky equation (1948) was found to overestimate KO for intact BBC when using the peak friction angle, and underestimate KO when using the secant friction angle. Despite these differences, RBBC should continue to be used as an analog test material for studying clay behavior of BBC. Future research should expand the comparison into different test modes and additional clay mineralogies.