# A Stability Analysis of the Ancient Site of Liye Based on the Strength Reduction Method
## 5 Stability Analysis
### Stability Analysis  
In the ABAQUS software, the \(X\)-axis is generally regarded as 1-axis, \(Y\)-axis as 2-axis and \(Z\)-axis as 3-axis. S22 then represents the stress in the \(Y\)-axis direction, the positive value is tensile stress and the negative value is compressive stress. Under different water content conditions, the soil sites mainly undergo downward deformation. Therefore, in this study, the stress changes in Y direction (longitudinal direction) are mainly analyzed. Figure 9 shows the diagram of the simulation results of displacement obtained from the numerical simulation of the four dangerous sections of the trench under condition 1. Figure 10 shows the diagram of the simulation results of longitudinal stress of the dangerous sections under condition 1. Given the assumption of condition 1, there is displacement at the top of the city wall and at the bottom of the trench, and the bank of the trench is large, with the earnten soil on the side facade tending to peel off. As a result, damage in the near future is not expected. However, when the external environment changes, the site soil will also deteriorate slowly, especially with the undercutting at the base being more serious and the displacement at the base generally being larger than that in the upper area. Figure 11 shows the diagram of the simulation results of displacement of the dangerous sections under condition 2. Figure 12 shows the diagram of the simulation results of longitudinal stress of the dangerous sections under condition 2. It can be seen from Figures 11 and 12 that the maximum vertical stress on the soil is found at the bottom of the model, while the surface stress of the soil is small. This is in line with the actual situation. In the actual environment, rain, seepage, and other factors cause the most serious damage to the site soil base. Therefore, the site is prone to erosion damage as the pores in the soil expand, the skeleton collapses, and the connection between particles weakens. Figure 13 shows the relationship between the displacement in the longitudinal direction and the safety factor of the wall slope top for each of the four dangerous sections. The reason why the ordinate in Figure 13 is negative is that the numerical model will produce longitudinal downward displacement under self-weight load. When the soil moisture content is 20%, the safety factor is 1.35. As the soil moisture content increases to 26%, the safety factor declines to 1.1. Under the action of load, the numerical model will produce small displacement, but when the displacement changes suddenly, it means that this time is the critical value for the destruction of earth sites, such as the position when the safety factor = 1.35 in Figure 13a and safety factor = 1.1 in Figure 13b. With the sudden change of displacement, the safety factor basically does not increase, which shows that the inflection point position (safety factor = 1.35 and safety factor = 1.1) is the failure limit condition of the soil sites. The results show that when the soil moisture content is low, the overall stability safety factor of each section is greater than 1, and the displacement magnitude is less than 1 mm. That is, the existing trench largely remains stable since the deterioration is not enough to pose a sudden threat to wall stability in the development period, and the surface cracks and gullies have little impact on the overall stability of the trench. When the moisture content of the soil is high, however, the safety factor of the trench decreases. This indicates that rainwater has a certain impact on the strength of the site wall. To prevent complex joint damage to the wall from rainwater and existing deterioration factors, we suggest that dewatering and drainage measures should be employed for the rammed earth at the top of the wall and the outside based on existing protective measures.