High Strain Rate Effects on a Clayey Sand Mixture

Understanding soil behavior under different strain rates is a key factor in many geotechnical applications, including earthquakes, dynamic compaction, rapid pile testing, roadway subgrade design, and projectile penetration. In this study, the stress-strain response of a clayey sand mixture at strain rates ranging from 0.0001/s to 10/s was studied. Remolded samples were prepared using a mixed soil consisting of 30% clay and 70% sand at a water content of 11%. This material is believed to represent materials commonly encountered in several formerly used defense sites that are in need of environmental remediation. The information is helpful for predicting the likely depth of burial of projectiles within the material to be remediated. Unconfined compression and unconsolidated undrained (UU) triaxial tests were conducted on 38-mm diameter cylindrical test specimens that were formed using previously hydrated mixed soils. The specimens were statically compacted at a constant rate of 1 mm/min. A hydraulic loading system equipped with an ultra-precise load cell and data acquisition system was used to capture load during tests. A strain rate logarithmic correlation was fitted to both unconfined and triaxial test results. Visual inspection of the test specimens suggests that rate dependence is due in part to changes in the failure mode. Test results can be implemented to account for the effect of strain rate in numerical simulation and analytical models.