Response of Soil to Impulse Loads Using the Split-Hopkinson Pressure Bar Technique

摘要

The split-Hopkinson pressure bar (SHPB) technique has been adapted to measure the dynamic response of soil to impulse loads. The SHPB technique is relatively simple and can significantly extend the range of stresses and strain-rates that can be applied beyond the capabilities of current equipment used for dynamic laboratory soil investigations. This capability will assist in satisfying the demand for soil property data which more closely reflects environments related to weapon effects problems. The various considerations involved in designing an SHPB experiment and evaluating the data with soil as a specimen are discussed in detail. Soils have several characteristics which complicate their use as specimens in an SHPB experiment: low wave speeds, nonlinear hysteretic behavior, and low unconfined compressive strength compared to the applied loads. Insight is provided as to how these factors affect experimental accuracy and data reliability. It has been shown herein that the assumption necessary to obtain meaningful data from an SHPB experiment can be satisfied when using compacted soil specimens constrained to a nearly uniaxial strain state. Also the ability to replicate experimental results has been established. In addition, the dynamic soil stress-strain response was found to be governed principally by the initial gas porosity of the specimen and no strain-rate dependency was exhibited at strains less than the initial gas porosity. A compliment of stress-strain curves are presented for specimens prepared at several combinations of moisture and density.