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This paper summarizes the results of a controlled series of undrained shock tests conducted on mixtures of Monterey No. 0/30 sand, water, and hollow glass microspheres. Hollow glass microspheres, utilized to entrap gas in the sand, have a collapse strength of about 1700 kPa, are stable over time, and remain passive until a pressure sufficient to collapse them is applied. When subjected to a sub-millisecond compressive stress pulse of about 2300 kPa, peak stress transmission ratio decreased about 50% as the saturation decreased from 100 to 99.5%. Positive residual excess pore pressures (decreases in effective stress) were measured at saturations of 100, 99.9, and 99.8%. Negative residual excess pore pressures (increases in effective stress) were measured at saturations of 99.7, 99.6, and 99.5%. Analysis indicates that no change in residual pore pressure should occur at a saturation of 99.77%. The results indicated that microspheres may be used as a passive measure to inhibit blast-induced liquefaction and for reducing peak blast-induced stress in saturated soils.
Professor and geotechnical engineering program leader, Colorado State University, Fort Collins, CO
Geotechnical engineer, City of Los Angeles, Geotechnical Services, Los Angeles, CA
Professor and head, Colorado State University, Fort Collins, CO
Stock #: GTJ10250J