**1. Introduction**

Coral sand is a special geotechnical medium that is rich in calcium carbonate and deposited by marine protozoan skeletons. Coral sand is widely distributed in the coasts and reefs of Australia, the Gulf of Mexico, and the South China Sea [1]. When compared with the common terrigenous sands, coral sand has special physical properties, such as multi-voids, irregular particle shape, and fragility. These properties lead to the difference of compressibility, shear strength, and permeability between the coral sands and the common terrigenous sands [2–5]. With the expansion of construction scale on coral reefs recent years, the seismic safety of coral reefs has attracted considerable attention [6–9]. Historically, a magnitude 8.1 earthquake struck Guam in the Pacific Ocean on August 8, 1993, which caused severe liquefaction of coral sandy sites in dredger fills and lake sediments [10]. Large-scale liquefaction of coral sand also occurred in the Hawaii earthquake in 2006 and Haiti earthquake in 2010, which caused irreparable losses to local infrastructure and people's lives and property [11–13].

Xiao et al. analyzed the dynamic strength, cyclic deformation, and pore pressure of saturated coral sand and microbial reinforced coral sand by the dynamic triaxial test in order to study the dynamic response characteristics of pile-soil-structure system in coral sand under earthquake [1]. Salem et al. pointed out that the calcareous sand has higher dynamic strength than siliceous sands and suggested the dynamic resistance ratio-confining pressure-relative density relationship of calcareous sand from North Coast Dabaa [14]. Xu et al. studied the transmission law of explosive stress wave

in saturated coral sand and quartz sand, and concluded that saturated coral sand has a stronger absorption and attenuation effect on explosive stress wave than quartz sand [15]. Sandoval et al. found the differences of dynamic response between Puerto Rico coral sand and Ottawa siliceous sand through the result of dynamic triaxial tests [16]. Other scholars have also carried out some research on the dynamic characteristics of coral sands [17,18]. However, the former researches mainly focused on the strength, deformation, and pore pressure characteristics of coral sands in small-scale models, and it does not involve the dynamic response while considering the interaction between structures and soil in large-scale coral sands sites.

The shaking table test is an important method for studying the dynamic response of liquefiable sites and the structures on them under earthquakes. Tang et al. performed the failure mode of pile foundation of bridge under earthquakes while considering the pile-soil interaction [19]. Dashti et al. carried out a series of liquefaction model tests of low-rise buildings through the centrifuge shaking table test; the mechanism of building settlement that was caused by liquefaction was discussed [20]. Chen et al. studied the dynamic characteristics and damage law of subway station [21]. Other scholars have also undertaken a lot of research on the dynamic response of various structures and foundations under earthquake using shaking table test and found that the depth and compactness of soil, the existence of structures, and the input parameters of shaking excitation have obvious effects on site liquefaction and dynamic response of structures and soil [22–30]. However, the above studies are aimed at the terrigenous sands, and there are few studies on coral sand at present.

Important military buildings for large equipment and heavy machinery on coral sand sites often use the low-rise concrete structures that are supported by pile group foundations. A series of shaking table tests of buildings with nine-pile foundation in coral sand were carried out in order to study the seismic response of coral sand and the structures on it. Shaking table tests on quartz sand sites in the same situation were also performed as comparative tests. The differences and similarities of dynamic characteristics of coral sand and Fujian sand were compared and analyzed based on the results of pore water pressure, acceleration, displacement, and dynamic bending moment.
