Computer-Automated Triaxial Testing System for Assessing and Mitigating Sample Disturbance in a Natural Clay in the Laboratory

Abstract

A computer automation for a manual triaxial cell involved in designing new test instrumentation components and connections and in developing new controller software and supportive hardware for accurate functioning of the system during long test durations was undertaken to run high-quality, sophisticated triaxial tests for measuring the stressstrain properties of clays. For validation and further evaluation of the developed computerautomated triaxial testing system, a laboratory testing program was performed to investigate the effects of sample disturbance on laboratory-measured clay soil behavior and the mitigation of disturbance effects in the laboratory using two reconsolidation methods, the stress history and normalized soil properties (SHANSEP) method and the recompression method. Computer-automated triaxial tests were performed on specimens of Boston blue clay (BBC) from a test site (Newbury, MA) sampled using a Sherbrooke-type block sampler. The test results from the laboratory testing program are presented, including for (i) onedimensionally consolidated undrained compression (CKoUC) tests on both normally consolidated (NC) and mechanically overconsolidated (OC) specimens using the SHANSEP method and (ii) anisotropically consolidated undrained compression (CAUC) tests using the recompression method. The CKoUC(NC) tests were performed to provide baseline SHANSEP data, and results were compared between CKoUC(OC) SHANSEP and CAUC recompression tests.