# A Stability Analysis of the Ancient Site of Liye Based on the Strength Reduction Method
## 1 Introduction  
Soil is one of the widely used building materials in the early stages of mankind. Examination of soil architectural sites in different environments has facilitated a greater understanding of soil and the mastery of its associated properties and characteristics [1]. Because site selection, technology, and materials that comprise earth sites reflect differences in political, military, and cultural information across time, earth sites have considerable research value [2]. Unfortunately, as shown in Figure 1, given the limitations of the material properties, these sites experience surface peeling, foundation erosion, fissure gullies, and other damage due to the effects of time and space [3, 4]. Affected by climate conditions and the customs of local residents, the preservation of earth sites such as the [PERSON]'s manusoleum in Ningxia, the old city of Jiaobe in Xinjiang, and the Great Wall along the silk road has become a major challenge [5]. Plus, strong weathering and destruction resulting from concentrated heavy rainfall in recent years [6, 7, 8, 9] have led earth sites in Hunan also to be at risk. The soil site of Liye, an ancient city in the Hunan Province of China, is one example. Although the shape and scale of the original moat can be studied, the soil site has shown large-scale deterioration due to long-term environmental effects. [PERSON] et al. [10] documented the historical changes and the functional evolution of the Nanjing Ming city wall. They also constructed a system to evaluate and quantify the cultural heritage of the ancient wall historical corridor and ensured the scientificity and accuracy of cultural heritage protection. [PERSON] et al. [11] studied the deformation and failure modes of the wall by using the methods of classification and induction. By classifying the factors that have caused the deformation and failure of the ancient city wall, the authors put forward a set of corresponding protective measures and suggestions. Investigating four soil sites in the Qinghai Province, [PERSON] et al. [12] found the sites have been poorly preserved, showing surface erosion, gullies, cracks, collapse, man-made damage, and other factors. The authors proposed strengthening the wall at the observation site to improve its seismic stability and to reduce the potential for interaction with the soil site. [PERSON] et al. [13] showed that the moisture content/volume and the pore water pressure of the soil near the surface increased rapidly during rainfall and became saturated earlier than the lower levels of soil. Similarly, [PERSON] and [PERSON] [14] found that rainfall infiltration directly affected the stability of the Forbidden City wall, contributing to cracking, instability, and the collapse of the masonry outside the wall. Using the strength reduction method and ABAQUS software, this paper analyzed the mechanical properties and the stability of the Forbidden City wall to provide a basis for its safety evaluation, protection, and repair. The related literature mainly analyzed the mechanical properties of the soil using macro tests or numerical simulations. As such, prior studies have not established a relationship between macro and micro scales. The structure of this paper is as follows: this paper analyzes, evaluates, and summarizes the factors that have contributed to the deterioration of the ancient moat site in Liye. Through field investigation, sampling, and testing, we have analyzed the chemical composition and microstructure of soil samples from the moat site using an X-ray diffractometer and a scanning electron microscope. Using the ABAQUS software, we have also constructed two-dimensional models of the seriously damaged portions of the site. Finally, we have compared and analyzed the stability performance of the trench under its natural state and after rainfall to evaluate the safety and stability of the most dangerous sections. The innovation of this paper is: due to the strong weathering and damage caused by heavy rainfall, the soil sites in Hunan are in danger.