# Influence of a Landslide on a Tunnel in Loess-Bedrock Ground
## 3 Results
### Deformation of Loess-Bedrock Interface  
The deformation behavior of the loess-bedrock contact zone was monitored by strain gauges in real time, and the landslide was analyzed layer by layer from the back edge to the front edge. In the deformation-time curve, there is an obvious step-like change, which indicates that, in the process of landslide deformation, the energy on the loess-bedrock contact surface accumulates and releases, resulting in an instantaneous deformation. The deformation increment and duration at different stages can be used to characterize the energy change at the loess-bedrock interface. The larger the deformation increment, the longer the deformation duration, indicating that more energy accumulated during the deformation process. The total deformation increment represents the total energy accumulated by the landslide, which can be used to judge the sliding trend of the landslide. In addition, the different sliding time of the soil indicates the deformation speed and deformation stage of the landslide. When the strain is negative, the strain gauge is compressed, and the soil movement direction is consistent with the thrust direction. While the strain is positive, the strain gauge is strained, and the deformation is in the opposite direction to the thrust (Figure 10). In the 7 th layer, the deformation increased negatively due to the pressure from the trailing edge in the early stage. As the sliding body moved downward and reached the tunnel roof, it was constrained and the deformation decreased, which caused soil accumulation. In addition, there was an upward reaction force on the overlying soil, which caused the deformation of the 7 th layer to increase positively. The 6 th layer is located at the tunnel, where the soil was in a state of compression, and the deformation increased positively. Layers 1-5 are located at the bottom of the tunnel, and here the soil continued to move downward, and the deformation continued to show a negative growth trend. Over time, the load changes show fluctuation characteristics, indicating that the slope continued to slide, and that the trailing edge of the slope repeatedly separated from and contacted with the loading system. Figure 9: Soil displacement field after loading. Figure 10: Strain monitored by strain gauges in the loess-bedrock contact zone. The distribution of the location of each layer is shown in Figure 2(a). The deformation data regarding the loess-bedrock interface at different times were collected, and the deformation contour of the interface is shown in Figure 11. At 30 min, the trailing edge was thrust and deformed downward, and the deformation in the tunnel and surrounding soil was zero. With the increasing movement of the trailing edge, the soil near the tunnel began to deform. The deformation of tunnel sides was large. At 270 min, a small deformation began to appear at the leading edge of the soil. With the passage of time, the amount of deformation gradually increased and the range of deformation gradually expanded. At 360 min, the upper soil was completely deformed. When it reached the top of the tunnel, the soil was subjected to the tunnel reaction force and tended to move upward, so the direction of movement gradually developed to the back edge of the slope. At 600 min, the reaction force of the tunnel on the soil was higher than that of the thrust, and the soil began to exhibit an extrusion deformation at the trailing edge. The location of the tunnel became the boundary of the displacement deformation. The upper soil of the tunnel moved upward, mainly manifested as soil uplift. In the lower part of the tunnel, the soil continued to move downward, showing a sliding failure mode. The simulated displacement contour changes in the loess-bedrock interface are shown in Figure 12. When the velocity was applied to the back edge of loess, the soil near the  
Figure 11: Loess-bedrock interface deformation contour measured by strain gauges 600 min into the test. tunnel began to deform, but the deformation was mainly on both sides.