Experimental study on soil-pile-structure interaction in liquefiable sand subjected to blast-induced ground motion

Vibration tests of a pile-supported structure in a liquefiable sand deposit were performed at Black Thunder Mine in Wyoming USA. Ground motions from large-scale mining blasts were used as input motions for the test structure. The test structure was constructed in an excavated 3m-deep pit and the pit was backfilled with water-saturated sand. Accelerations of the test site, the test structure and one of the piles were measured. Pore water pressures in the pit and strains of the pile were also measured. Vibration tests were performed six times with different levels of input motions. The maximum horizontal acceleration recorded at the adjacent ground surface increased from 20 Gals to 1,352Gals as the blast area approached the test site. The excess pore water pressures also increased with the levels of input motions and sand boiling phenomena were observed in the test pit. It was thus clarified that this vibration test method was very effective in verifying the soil nonlinearity including the liquefaction and the dynamic behavior of the pile-supported structure.