We present results from cyclic tests conducted in the laboratory using a prototype in situ cyclic torsional cylindrical shear geotechnical testing system. The system is intended to advance our ability to design critical systems to resist earthquakes by improving our ability to analytically predict the behavior of soil-structure-equipment systems during earthquakes. It is to do so by providing, more reliably than we feel is now possible, estimates of the in situ cyclic shear stress vs strain characteristics needed by refined earthquake analyses. These characteristics include 1) resistances to initial liquefaction, cyclic degradation, and large cyclic deformations, and 2) undegraded, nonlinear, inelastic characteristics. The testing system was found to be effective under representative controlled laboratory conditions and promising for field use. Test results were found to be reasonable and consistent with published results of laboratory tests of a high quality. Additionally, we did not observe major limitations or encounter abnormal difficulties
