EXISTING AND POTENTIAL CAPABILITIES OF THE TORSIONAL CYLINDRICAL IMPULSE SHEAR TEST

HENKE R., Dynamic in situ Geotechnical Testing, Bethesda, Maryland 20817, hroberthenke@aol.com.

My presentation is to summarize existing and potential capabilities of the torsional cylindrical impulse shear test. The impulse shear test may be relevant to urban seismic hazard mapping. The impulse shear test is a new in situ geotechnical testing technology originally intended to provide, for soil deposits, detailed information on in situ nonlinear inelastic shearing deformation characteristics. This information is needed for dynamic geotechnical earthquake engineering analysis procedures. The impulse shear test addresses the issue of reducing effects on inferred soil characteristics of disturbances to in situ conditions. Evaluative tests of a field prototype impulse shear testing system, carried out at a number of sites across the nation including the I-10/La Cienega Boulevard undercrossing in Los Angeles (site of a freeway structure that collapsed during the 1994 Northridge earthquake) and Treasure Island in the San Francisco Bay, seem to confirm the ability of the impulse shear test to provide the stated information. Additionally, the tests suggest that the impulse shear test may have the capability of providing reasonably precise indications of in situ resistances of soils to liquefaction and related deformations. I plan to present representative test results for soils that are particularly hazardous during earthquakes: a medium-stiff clayey soil and a highly liquefiable loose sandy soil.