Application and comparison of multistage triaxial compression test procedures on reconstituted Ankara clay

¹ Norwegian University of Science and Technology, Department of Civil and Environmental Engineering, Trondheim, Norway
² Middle East Technical University, Department of Civil Engineering, Ankara, Turkey

^* Corresponding author: Amirahmad.Vakilinezhad@NTNU.no

Abstract

The ability to conduct conventional triaxial compression tests on multiple identical specimens is restricted by available sample quantity, sample homogeneity, as well as testing duration. Multistage triaxial testing is an alternative method to tackle these issues by using a single specimen sheared under different confining stresses to attain the strength parameters. Although there are widely accepted procedures to decide when to stop each shearing stage and proceed to the next stress level, the applicability of these procedures on different soil types is still a question. This study examines the applicability of combinations of two multistage triaxial testing procedures (Rational Procedure and Minimum Slope) under two different deviator stress conditions (Sustained or Cyclic) during confining stress increase. The outcome is compared to conventional triaxial test results for undrained and drained shearing of reconstituted specimens of high-plasticity Ankara Clay. Out of the four options, the rational procedure with cyclic deviator loading and minimum slope with cyclic deviatoric loading conditions, are found to give the most accurate strength parameters in reference to single-stage test results. The maximum number of the shearing-reconsolidation sequences applicable before strength loss is also investigated for each multistage triaxial testing procedure.