Abstract
This paper presents experimental investigations on particular failure patterns of foundation piles found in Hyogo-ken Nambu earthquake that were probably induced by seismic up-down vibrations. Impact tests on cylindrical mortar specimens were conducted in different loading modes. Vertical splitting failure was observed in static compression tests whereas horizontal tensional fracture occurred in static tension tests and impact tension tests. Depending on the level of impact energy, failure patterns in impact compression tests were found varying from cone splitting failure to X-shape shearing failure to cone shearing failure to 45-degree shearing failure, and to horizontal tensional fracture due to reflection stress wave.
