## 2 Experimental Setup  
The full-scale test system employed for laboratory testing has rigid external walls and a hydraulic loading system (Figure 2). The full-scale tests, plotted to scale in Figure 2a, utilize units in meters (m). The system consists of two types namely; the test without a pipe (S test) and the test with a pipe (P test). In these tests, the load cell type earth pressure cells (L) were employed to measure the stresses around the pipe, while potentiometers were utilised to measure the deflections of the pipe. Base on the pipe's position, the load cells were placed as illustrated in Figure 2. All of the 10 load cells positioned around the pipe were numbered to enhance the clarity of the tex.  
Load cells of L1 and L2, which are not visible in Figure 2b, are located under the pipe and are aligned with L3 and L4.  
Figure 2: Full-scale test system and instrumentation scheme; (**a**) front view and (**b**) top view.  
The load cells used have a maximum operating temperature of 60 \({}^{\circ}\)C and a minimum operating temperature of \(-\)20 \({}^{\circ}\)C. Throughout the tests, the laboratory temperature remained within the operating limits of the load cells, minimising the effect of environmental temperature on their performance. Although the load cells are supplied with a calibration certificate for specific temperature ranges, all of the load cells were calibrated in the laboratory and within the backfill, providing results in line with the values stated on the calibration certificate.  
Considering the location of the pipe in Figure 2, four load cells were strategically placed at 0.50 m from the tank wall, where the endpoints of the pipe make contact. These load cells were used to determine the vertical stresses at the crown of the pipe (L3 and L4) and at the invert of the pipe (L1 and L2). These measurements were conducted using TML KDG-500 kPa cells imported from Japan. Furthermore, horizontal soil stresses at the pipe springline (L5 and L6) were determined using TML KDG-200 kPa cells. The cells made direct contact with the pipe wall. Additionally, another set of four cells was used in the soil to record vertical stresses within the pipe zone. The center of two of these cells were located 0.08 m to the right and 0.08 m to the left of the springline (L7 and L8). These measurements were performed using TML KDG-200 kPa cells. The centers of the remaining two cells, which are smaller than the others, are 0.01 m to the right and 0.01 m to the left of the pipe springline (L9 and L10). Moreover, for the purpose of measuring both vertical and horizontal pipe deflections throughout the loading stages, potentiometric displacement sensors were fixed within the pipe at its midpoint section, utilising Burster 8709-5100 sensors manufactured in Germany (Figure 3e). Also, two extra linear variable differential transformers (LVDT) were positioned at the top of the loading plate to measure surface displacement (S4) during both the S and P tests (Figure 3c).  
In the S and P tests, the backfill was compacted in a controlled manner using two steel plates. The first plate measures 0.15 m \(\times\) 0.15 m \(\times\) 0.02 m and weighs 2.5 kg, while the second plate measures 0.30 m \(\times\) 0.30 m \(\times\) 0.02 m and weighs 4.5 kg (Figure 3b). The burial depth in both tests is equal to the pipe diameter, D, (0.315 m) and the loads are applied as a strip along the pipe cross-section. This burial depth complies with the minimum of 0.305 m recommended by [PERSON] [17] and [PERSON] et al. [18]. The test cross-sections are shown in Figure 3.  
Figure 3: Stages for full-scale test; (**a**) control of unit weight (**b**) compaction plates and scale (**c**) LVDT (**d**) pipe layout (**e**) potentiometers and (**f**) software and data logger.