n hataf - Assistant Professor, Department of Civil Engineerring, Shiraz University, Shiraz, Iran
s aghaebrahimi - M. Sc. Student, Department of Civil Engineerring, Shiraz University, Shiraz, Iran

The engineering parameters of soil such as strength and stiffness measured in monotonic loading triaxial testing are used routinely in engineering practice. The changes in these parameters are becoming increasingly important in the design of structures subjected to dynamic loading such as earthquake, wave loading, etc. Investigating the behaviour of soils under cyclic loading, however, requires automated systems with continous control and data recording. This paper presents such an automated system developed by modifying a commercially available triaxial apparatus at Shiraz University. Different features of the system such as controlling unit, cell modifications, special caps, etc. are described. The characteristics of the system in applying the strain controlled cyclic loading are discussed. The system used to investigate the behaviour of Shiraz silty clay under monotonic and cyclic conditions. Typical results of such tests on yndisturbed specimens are presented.