An automated control system for undrained monotonic and cyclic simple shear tests

A standard NGI type Direct Simple Shear (DSS) apparatus has been modified to enable the application of unidirectionalsimple shear monotonic and cyclic loading through an automated electro-mechanical control system. Twoalgorithms were implemented in a computer control software, one for constant height control during the undrainedshearing phase and the other for controlling the horizontal load or horizontal displacement in cyclic stress and straincontrolled tests, respectively. It is shown that the adopted automated electro-mechanical control system represents avalid solution for low frequency cyclic tests under constant volume conditions. Typical cyclic test results under bothstress and strain-controlled conditions are also presented in connection with the development of laboratory methodsfor the analysis of seismic pore water pressure build up and liquefaction at level ground.