Symposium: Tenth Int. Conf. on Stress Wave Theory and Testing of Deep Foundations, San Diego, 2018 SOIL DAMPING AND RATE DEPENDENT SOIL STRENGTH CHANGES DUE TO IMPACT AND RAPID LOADS ON DEEP FOUNDATIONS Frank Rausche1, Patrick Hannigan2, and Camilo Alvarez3 1PileDynamics Inc., Cleveland, OH, 44139; email
[email protected] 2GRL Engineers, Inc., Cleveland, OH, 44139; email
[email protected] 3GRL Engineers, Inc., Los Angeles, CA, 90065; email
[email protected] ABSTRACT Measurement of the static soil resistance of deep foundations can be done by either static or dynamic loading tests. The dynamic test applies a load to the pile by impact of a large mass onto the highly or minimally cushioned pile top. Measuring the resulting force on top of the deep foundation (pile) and the associated motion and performing a dynamic analysis of the pile-soil system allows for the separation of static from dynamic soil resistance components and the calculation of an equivalent static load-displacement curve. This result can be compared with the same type of curve obtained by the static loading test. For certain plastic soils, it has been found that the static resistance derived by analysis from the dynamic test may not completely account for the fact that quickly loaded materials exhibit a strength greater than a slowly loaded material. The resulting static resistance should then be reduced by a rate factor which depends on basic soil parameters. This paper reviews different approaches of loading rate and damping effect identification. It also presents several examples of dynamic test results on piles driven or drilled into soils with different levels of plasticity.