# A Large-Scale Model of Lateral Pressure on a Buried Pipeline in Medium Dense Sand
## 3 Results and Discussion  
In this study, a large-scale model, developed to assess the stress on buried pipes due to lateral ground movement, is presented. Earth pressure cell sensors were used to measure the stress along the buried High-Density Poly-Ethylene (HDPE) pipe, which was subjected to lateral ground movement in the large-scale physical model. A strain measurement data logger was used to record the stress values. Figure 5 demonstrates the recorded stress values at various positions on the buried pipe. The movable plate displacements were recorded using a wire displacement sensor. In general, the stress values rose steadily (either positively or negatively) along the buried pipe as the soil displacement increased. Figure 6a illustrates the behavior of the stresses at the front side of the pipe (EPC 1, 2, 3, 4, and 5) during the initial stages of plate motions that were measured using wire displacement sensors (50 mm, 100 mm, and 150 mm). At 50 mm of plate movement, EPC 2 and EPC 4 (located at the unstable soil boundary) recorded the highest stresses with an average value of \(-14.35\) kPa. The middle section of the pipe (EPC 3) recorded pressure of \(-3\) kPa, whereas in the stable soil zones (EPC 1 and EPC 5) minimum pressures were recorded, i.e., the average pressure was only 1.3 kPa. The negative stress values indicate the active soil pressures at EPC 2, EPC 3, and EPC 4. In contrast, the positive stress values in EPC 1 and EPC 5 indicate that soil pressures on the pipe were in the passive zone. Referring to Figure 5; Figure 6a, the stresses at EPC 2 and EPC 4 started to drop when the displacement of the movable plate had exceeded 50 mm, which indicates the failure of soil at the boundary of the landslide. In contrast, the stress values of EPC 3 began to rise (located at the middle of pipe). Figure 5: Stress values on the buried pipe at different positions. Figure 6b shows stress values at the plate displacement from 200 mm to 500 mm with no significant stress changes. The soil pressure began to increase again in small amounts at the boundary of the landslide. In contrast, at the middle of the pipe, the soil pressures were not constant (increases and decreases in an unregulated manner). At 550 mm of plate movement, the stresses at the boundary of the landslide began to increase because the wall was approaching closer to the pipe (see Figure 6c). In comparison, the pressures in the mid-section began to decrease due to the soil failure in the middle of the landslide area. Figure 6: (a) Load distribution along the pipe at plate stages from 50 to 150 mm. (b) Load distribution along the pipe at plate stages from 200 to 500 mm. (c) Load distribution along the pipe at plate stages from 550 to 700 mm. According to the analysis of lateral soil pressure on the pipeline, the section of the buried pipeline located in the landslide area experienced the greatest stress [30]. The lateral pressure increased as soil displacement increased, and soil surface deformations appeared above the pipe position [9]. In this experiment, a camera was mounted next to the model box to monitor the soil surface deformations. The evolution process of soil instability and failure was recorded in real-time by the camera. Figure 7 illustrates the surface displacement of the soil before and after moving the movable plate. Figure 7a displays the soil surface position before starting the experiment, while Figure 7b presents the surface of the soil after displacing the moving plate by 50 mm. The dashed black lines represent the original location of the ground before the displacement. Some initial cracks appeared on the surface of the soil due to the accidental movement of the ground. Most of the cracks at 50 mm were superficial as marked by the brown arrows, and these cracks represent the boundaries of subsidence and heating of the soil zones (see Figure 8). When the movable plate reached 100 mm, tension cracks appeared in the unstable zone and behind the buried pipe due to increased stress on the pipe.