# Study on the Optimization of Pile Length of Micropiles in Soil Landslides
## 1 Introduction  
Landslides in China, as a common geological disaster, are characterized by fast movement, extensive range of destruction, and a strong impact on regional economic development [1]. For example, on 12 August 2015, a large landslide disaster occurred in Menggou Village, Zhongcun Town, Shanyang County, Shaanxi Province, resulting in 38 deaths, 1 injury, and 27 houses buried with extremely heavy losses [2]. On 23 July 2019, a landslide disaster occurred suddenly in Shuicheng County, located in Liupanshui City, Guizhou Province, resulting in 21 houses being buried, 1600 people affected, 9 missing, and 43 deaths [3]. Landslides in China are common geological disasters that move quickly, cause extensive damage, and hinder regional economic development. In the 1950s, [PERSON] in Italy proposed the micropile technology for foundation reinforcement. In the early 1970s, the Italian patent on micropile technology was terminated, and micropile technology saw real development internationally [4]. Over the past six decades, micropile technology has gained increasing recognition within the engineering community, evolving from its humble beginnings as a small-scale solution to its current status as a widely promoted and utilized technique. [PERSON] et al. [5] evaluated the effectiveness of a variety of management methods, including micropiles, applied to manage landslides inthe Polish Carpathians, showing that in most areas, micropile management solutions were effective. [PERSON] et al. [6] presented a case study of a micropile support scheme applied to a landslide remediation project, which served as temporary stabilization measures. With the continuous research on miniature piles, the research on the response of miniature piles under seismic dynamic action has gradually become a hot topic. Many scholars have studied the response characteristics and deformation law of micropiles under dynamic loads through numerical simulations or related shaking table tests and centrifugal shaking table tests. [PERSON] et al. [7] summarized their research on the dynamic characteristics of micropiles in sandy soil foundations under seismic loads using centrifugal model tests and pointed out that the fundamental frequency of micropiles is affected by the arrangement form. The monopile's base frequency is affected by its arrangement, and this frequency is closely linked to the inclination angle of minipile arrangements. When minipiles are arranged in rows, they provide stronger resistance against seismic loads while experiencing smaller bending moments and bearing displacements compared to regular piles under similar vibratory loads. In the numerical simulation of seismic dynamics, [PERSON] [8] established three numerical models of micropiles with different inclination angles using numerical simulation software to investigate the working performance of micropiles in liquefied sites under self-weight conditions and seismic action and derived the approximate distribution locations of the maximum bending moment of micropiles under seismic action and the variation law of pile top displacement with seismic wave intensity. Based on the results of numerical simulations, scholars have also made relevant suggestions for the seismic calculation of miniature piles. [PERSON] [9] adopted the numerical analysis tool to investigate the problems related to micropiles under dynamic loads and derived the dynamic response characteristics of micropile-reinforced slopes and the seismic calculation method of micropile combination structures based on the amplification factor method. However, the dynamic soil pressure law on the pile side derived from the simplified analytical model lacks verification through relevant shaking table tests or actual measurement data. For the study of pile length, [PERSON] [10] found that when the length of the embedded section of the minipile is insufficient, the horizontal resistance of the soil below the slip surface reaches its ultimate value, and the minipile as a whole undergoes rigid motion with the landslide.