# Static and Dynamic Response of Micropiles Used for Reinforcing Slopes
## 1 Introduction  
Catastrophic landslides are considered to be environmental disasters around the world due to the tremendous economic losses and casualties that they cause every year [1, 2, 3, 4]. Landslides are one of the most serious and widespread natural hazards, and they can seriously endanger the lives and properties of residents living in the effected area [5]. For instance, from 1998-2017, landslides affected an estimated 4.8 million people and caused more than 18,000 deaths, with poor populations in developing or low-income countries being the most affected [6]. Therefore, conducting research on the stabilization technology of landslide disasters is of great significance for improving the prevention and treatment of regional landslide geological disasters, ensuring the safety of people's lives and property, and building a harmonious social and economic development. Regarding landslide stabilization technology, there are currently anti-slide piles, retaining walls, anchor cable frames, etc. Among all kinds of anti-slide supporting structures, micropileis a new type of supporting structure and is favored by scholars. Generally, micropiles refer to a small-diameter, strong-reinforced cast-in-place pile with a diameter of less than 300 mm and a slenderness ratio greater than 30 and is created using drilling and pressure grouting [7]. In the early stages of its development, most researchers mainly studied its performance in stabilizing slopes under static force [8]. Recent research in China supported by the Water and Environmental Department of China Geological Survey used a 1:2 large-scale physical model to conduct static model testing on micropiles [9; 10; 11]. The models consisted of single pile, row piles, and group piles, and they were tested and studied, respectively. The results proved that micropiles can significantly improve the stability of slopes. [PERSON] et al. [12] conducted a study on the performance of micropile groups and confirmed that they have immense working potential under horizontal loading. [PERSON] et al. [13] studied the load transfer law of the micropile groups used in a slope through physical model tests and further confirmed the importance of the connecting beam for the micropile reinforcement of the slope. [PERSON] et al. [14] has shown that micropile groups subjected to horizontal loads will produce pile group effects. The group effect refers to the phenomenon where the pile-soil interaction causes pile-side resistance, pile-tip resistance, and other properties that change after the pile group is subjected to a horizontal load, resulting in the unequal bearing capacity of each row of the micropile. [15] The horizontal bearing capacity of pile groups is less than the sum of the load capacities of its individual bearings. However, with the increased research on micropiles, the response of micropiles under seismic dynamics has become important to understand. As we all know, the direct action of seismic load on the landslide body will reduce the shear strength of the landslide body, and then trigger the landslide. [PERSON] et al. [16] emphasized the importance of the seismic process in regulating the failure of slopes. The results show that the occurrence of landslides is due to the significant reduction of slope material strength caused by past seismic activities and indicate that repeated seismic loading is a critical process for catastrophic failure. In this regard, many researchers have conducted related experiments and simulation. [PERSON] et al. [17] simulated a micropile-reinforcemed landslide under an earthquake via FEA and proved that micropile can greatly reduce the displacement of the pile top and the damage of the pile body caused by the earthquake. [PERSON] et al. [18] studied the dynamic characteristics of using inclined micropiles to reinforce landslides through shaking table tests and showed that dynamic amplifications of acceleration on micropiles and the soil surface can be reduced by inclining the micropiles. [PERSON] et al.