Dynamic behaviors of calcareous sand under repeated one-dimensional impacts

Abstract

Based on the background of the development of China's South China Sea, few studies can provide a reference for pile foundation construction in calcareous sand layers. In this paper, one-dimensional impact tests were conducted on three uniformly graded (0.25–0.50 mm, 0.50–1.00 mm, and 1.00–2.00 mm) and one mixed graded (0.075–2.00 mm) calcareous sand and silica sand specimens with the aid of a split Hopkinson pressure bar (SHPB) system, while several sets of mixed graded specimens with different moisture contents and relative densities were studied for comparison. Each specimen was impacted at least 10 times. The results of the tests based on the effect of the number of impacts, particle size, moisture content and relative density on the dynamic behavior of calcareous sand are summarized as follows. The dynamic apparent stiffness of calcareous sand is approximately 1/8–1/9 that of silica sand due to their different particle shapes and mineral compositions. The dynamic/bulk/shear apparent modulus of calcareous sand decreases with an increase in the mean diameter, d50. After repeated impact, the apparent modulus of specimens with different particle sizes continued to increase and decreased with an increase in d50. For calcareous sand, with increasing particle size, the compression index Cc increases, and the yield pressure is approximately 40% that of silica sand under the same conditions. Compared to silica sand, calcareous sand reaches a better energy absorption capacity at a lower stress. Under the same axial stress, the energy absorption efficiency increases with increasing particle size and decreases with an increase in the number of impacts.