# Experimental Study on Dynamic Response Characteristics of RPC and RC Micro Piles in SAJBs
## 1 Introduction
Therefore, it is of great significance to study the dynamic response characteristics of micro pile-soil interaction under a seismic wave load. [PERSON] [22] conducted a shaking table test on a single circular steel tube micro pile-soil system to investigate the energy consumption of the micro pile under a different counterweight load at the top of the pile, and then the energy dissipation mechanism of the micro pile under sandy soil conditions were discussed in detail. [PERSON] et al. [23] investigated the effect of reaming on the mechanical properties of micro piles based on the shaking table test, and the energy dissipation mechanism of micro piles were obtained. However, the energy dissipation effect of ordinary concrete micro piles is not desirable. [PERSON] [24] also studied the influences of reaming conditions on the mechanical properties of the micro pile foundation based on a quasi-static test. It was found that the'm' method and the 'API' method were modified according to the test results, and the static \(p\)-\(y\) curves of micro pile-soil suitable for sandy soil conditions was deduced and proposed. In addition, there are numerous research studies based on finite element model (FEM) analysis to simulate the interaction effect between the micro pile and the soil. Based on the Winkler foundation beam model, the soil resilience distributed continuously is discretized to be the force performed by a series of discontinued beam elements with springs. This  
Figure 1: A new-type semi-integral abutment jointless bridge (SIAJB). measure can simplify the analysis of the pile-soil interaction [25; 26]. The horizontal deformation and rotation can be considered in the note where the masses of pile were discretized and concentrated, while the soil surrounding the pile is simulated by a series of discretized spring-damper elements in which the stiffness of spring is determined by \(p\)-\(y\) curves such as proposed by National Cooperative Highway Research Program (NCHRP) [27], American Petroleum Institute. (API-RP2A) [28], and Reese [29]. Regarding all of the above, including a number of studies on micro piles-soil interaction, they mainly focus on static loads and numerical simulation investigations. However, limited research studies have been focused on the dynamic response of micro pile-interaction, and these research studies are relatively monotonous, failing to reflect the micro pile-soil system under dynamic loads and relatively poor seismic capacity under an earthquake load. To be noted, most of the piles used in above studies are ordinary concrete micro piles whose seismic performance is relatively poor. Therefore, it needs further investigation to improve the seismic performance of the micro pile-soil system in semi-integral abutment jointless bridge (SAJB). The reactive powder concrete (RPC) micro pile is a new type of micro pile, which was usually made by ultra-high concrete. Compared with the conventional reinforce concrete (C40) pile, the RPC pile has more performances composed of ultra-high compressive strength, more high durability, and more high toughness, which, as a new type, the pile in material could satisfy the requirements of the approach slab's foundation [30]. However, there are limited research studies focused on this type of pile, especially for its dynamic response properties during seismic wave load, which leaves this applicability in doubt. In past decades, researchers mainly focused on the vertical mechanical properties and bearing capacities of RPC piles, while only a small amount of them were on the dynamic response characteristics under seismic wave excitation. Therefore, in order to make a further study on the dynamic characteristics of the micro pile-soil interaction, the shaking table tests on dynamic response properties of reactive powder concrete (RPC) and reinforce concrete (RC) micro piles were carried out. Under the dynamic load excitation, the fundamental frequencies of micro piles were obtained.