## 4 Results
### The Influence of Coal Mining Subsidence on Slope Length of Loess Slope  
2.1 The Variation Characteristics of Slope Length of Subsidence Slope Under the Same Natural Slope Shape  
According to Table 4, the comparison chart of the reduction and the change in the slope length of the loess slope after the mining subsidence under the same natural slope condition is drawn; this is shown in Figure 6.  
Figure 6: Under the same natural slope shape, the comparison chart of slope length reduction and decrease after full mining. It can be seen from Figure 6 that no matter what kind of slope shape, coal mining subsidence will lead to the decrease in the slope length of the loess natural slope, and the smaller the natural slope, the greater the decrease in slope length. Specifically:  
Firstly, under the condition of full mining, when the natural slope is [5\({}^{\circ}\), 15\({}^{\circ}\)), the average decrease in the slope length of the linear, concave, convex, and composite loess slopes is 3.44%, 5.09%, 2.82%, and 4.75%, respectively. When the natural slope was [15\({}^{\circ}\), 25\({}^{\circ}\)), the average decrease in the slope length of the four loess slopes was 3.10%, 4.72%, 2.62%, and 4.18%, respectively. When the natural slope was [25\({}^{\circ}\), 35\({}^{\circ}\)), the average decrease in the slope length of the four loess slopes was 2.86%, 3.84%, 2.27%, and 3.50%, respectively. When the natural slope is [35\({}^{\circ}\), 45\({}^{\circ}\)], the average decrease in the slope length of these four loess slopes is 2.06%, 2.44%, 1.51%, and 2.11%, respectively. It can be seen that coal mining subsidence will lead to the decrease in the slope length of the loess slope with the increase in the natural slope. Secondly, under the condition of full mining, the slope length of the linear, concave, convex, and composite loess slopes with a natural slope of 5\({}^{\circ}\) has the largest decrease, which is 1.44 times, 1.47 times, 1.43 times, and 1.63 times that of the average decrease in the slope length of the four slopes with a natural slope of 15\({}^{\circ}\), 25\({}^{\circ}\), 35\({}^{\circ}\), and 45\({}^{\circ}\). It can be seen that the influence of coal mining subsidence on the slope length of the loess slope is the most obvious when the natural slope is 5\({}^{\circ}\), and its change trend conforms to the characteristics of a quadratic polynomial function, as shown in Equations (5)-(8). The slope length reduction amplitude equation of straight slope : \(Li=-0.0011i^{2}+0.0048i+3.597\) \(R^{2}=0.9394\) (5)  
The slope length reduction amplitude equation of concave slope : \(Li=-0.0022i^{2}+0.023i+5.1784\) \(R^{2}=0.9929\) (6)  
The slope length reduction amplitude equation of convex slope : \(Li=-0.0013i^{2}+0.0196i+2.8265\) \(R^{2}=0.9873\) (7)  
The slope length reduction equation of composite slope : \(Li=-0.0019i^{2}+0.0025i+5.0356\) \(R^{2}=0.9836\) (8)  
In the equation: \(i\)--The natural slope of four kinds of slope shape of loess slope, \({}^{\circ}\); \(Li\)--Reduction in slope length, %. 4.2.2 The Variation Characteristics of Slope Length of Subsidence Slope Under the Same Natural Slope  
According to Table 4, under the same natural slope conditions, the curves of the decrease and decrease in the slope length of the loess slope after mining subsidence are drawn and are straight, concave, convex, and composite. See Figures 7 and 8. Figure 7: The change curve of slope length reduction after full mining under the same slope. It can be seen from Figures 7 and 8 that under the same natural slope, the influence of coal mining subsidence on the slope length of the linear, concave, convex, and composite loess slopes is different. Specifically:  
Firstly, under the condition of full mining, when the natural slope is [5\({}^{\circ}\), 25\({}^{\circ}\)], the average decrease in the slope length of the linear, concave, convex, and compound loess slopes caused by mining subsidence is 3.31%, 4.90%, 2.73%, and 4.49%, respectively.