EQUIPMENT AND TESTING PROCEDURES FOR SMALL STRAIN TRIAXIAL TESTS

摘要

Errors of measuring the stress-strain behavior of soils using the conventional triaxial apparatus may be induced by manmade errors during preparation of a sample, low precision of instruments, inaccurate measurement methods, and improper arrangement of the conventional triaxial apparatus. In this study, such errors are investigated and two solutions are proposed: 1) develop a set of high-resolution triaxial apparatus installed with Hall effect local strain transducer and bender elements; 2) establish the recommended testing procedure (RTP) for preparing the set up of a sample. Then, a series of K_0-consolidated undrained axial compression (CK_0 UAC) tests were carried out on undisturbed Taipei silty clay using the developed triaxial apparatus and the RTP. Results showed that the Taipei silty clay displays high initial stiffness and nonlinear stress-strain behavior at small strain levels greater than 10~(-5). The initial stiffness of the Taipei silty clay measured in this study is significantly higher than that measured from conventional triaxial tests but is close to that obtained from in-situ seismic tests. The capability of the developed triaxial apparatus with the RTP in measuring the small strain stress-strain behavior of soils is validated.