## 5 Results and Discussion  
In this paper, based on the potential failure mode of overtopping, the mechanism of soil internal force transfer at the top of double-row buried piles is described, and the design calculation method of pile length at the load section of a double-row buried pile is proposed.  
(1) Based on the simplified calculation model of the pile length of the loading section of the single-row buried pile, a theoretical analysis model of the double-row buried pile is established. The soil mechanical transfer mechanism of the double-row buried pile in the case of overtopping failure is expounded. In order to achieve a better anti-sliding effect, the pile length of the load section of the front pile should be slightly higher than that of the back pile. When overtopping failure occurs, a new rupture angle will be generated when the soil thrust acts on the front pile.  
(2) Based on the established theoretical analysis model of double-row buried piles, the transfer coefficient method and rigid body limit equilibrium theory are used to analyze the force on the potential sliding surface over the top and the sliding body surrounding the slope. Moreover, the design calculation equation of the pile length at the load section is obtained when the pile position is horizontal and inclined.  
(3) Taking a landslide project in Yan'an City, Shaanxi Province, China, as an example, the landslide control effects of single row length, double row length and double row sinking are compared. Compared with double-row full-length pile, the double-row buried pile saves about a quarter of the material and improves the economy of engineering treatment under the condition that the strength meets the requirement.  
(4) The pile length design and calculation of the load section of the double-row buried pile in the landslide control project have been completed. The engineering feasibility of the proposed design calculation method is verified by practical application, which can provide engineering reference value for the use of the double-row buried anti-slide pile structure in similar large-scale landslide treatment.  
(5) The design method of pile length at the load section of the double-row buried pile derived in this paper is suitable for landslides with a thick sliding body. When the sliding body is thick, it will produce a large landslide thrust if the use of double row of full-length pile treatment cost is greater and the construction difficulty is greater. At this time, double rows of buried piles can be used for treatment, which can avoid material waste and save costs under the premise that the strength meets the requirements.  
(6) In order to facilitate calculation, the soil in front of the pile is assumed to be a rigid body in the analytical model in this paper, but the soil is actually an elastic material, so the equation derived in this paper has certain errors. The design method is used to analyze the strength of a landslide project in Yan'an, and the reliability of the calculation method is verified. It is hoped that future research will address these limitations and provide further insights.  
Conceptualization, X.L.; methodology, X.L.; software, M.W.; validation, M.W. and X.L.; formal analysis, M.W.; investigation, M.W.; resources, W.Y.; data curation, R.X.; writing--original draft preparation, M.W.; writing--review and editing, M.W.; visualization, W.Y.; supervision, R.X. and X.P.; project administration, X.P. All authors have read and agreed to the published version of the manuscript.  
Natural Science Basic Research Program of Shaanxi (Program No. 2022 JM-280).  
Not applicable.  
**Data Availability Statement:** All data used during the study appear in the submitted article.  
**Conflicts of Interest:** The authors declare no conflicts of interest.