## 2 Methodology  
### Sample Preparation  
The sampling site is located in Yan'an City, Shaanxi Province, China, which features two typical engineering projects, namely GMRL and MECC. Four types of loess samples were collected (Figure 2), namely, intact loess from the late Pleistocene (Q\({}_{3}\) loess), intact loess from the middle Pleistocene (Q\({}_{2}\) loess), remolded loess from the GMRL site (F1) and remolded loess from the MECC site (C1). The experimental soil samples in this study were all undisturbed soil samples obtained in the field. Since these four sets of soil samples are located in the excavation area and filling area of two typical engineering projects of GMRL and MECC, the sampling points are located at four locations. The intact Q\({}_{2}\) was collected from a cut slope of the MECC project (Figure 2b), while the C1 loess was obtained from a well dug in the filling area of the MECC project (Figure 2c) at a depth of 23 m. The intact Q\({}_{3}\) was collected from an excavation slope at the GMRL site (Figure 2d), and the F1 loess was taken from the filling area of the same site (Figure 2d).  
For the sampling process, an undisturbed soil block measuring approximately \(250\times 200\times 200\) mm was obtained first. Then we pressed the PVC tube onto the top of the soil block while trimming the soil sample to fit inside. The PVC tubes were pre-cut to appropriate dimensions (160 mm in height and 110 mm in diameter). Afterward, we wrapped the prepared soil sample in the PVC tube with multiple layers of plastic wrap, followed by sealing with adhesive tape to prevent moisture loss. We pre-cut circular covers with a diameter of 11 cm from discarded cardboard and placed them on both ends of the soil sample tube to prevent deformation under pressure. We sealed the entire tube with adhesive tape, labeled it, and then placed the soil sample in a designated box for transport back to the laboratory.  
Figure 2: Location of the sampling site: (**a**) satellite image from Google Earth of the study area; (**b**) the excavated slope profile; (**c,d**) the newly created land.  
The basic physical properties of the loess specimens were measured in the laboratory, including dry density, natural water content, void ratio, saturated water content, Afterberg limits (plastic limit, liquid limit, and plasticity index), and grain size distribution, following the relevant ASTM standards. According to the regulations of the test standard, each group should have two specimens, and if the difference between the two values is within the error range, the average of the two is taken as the result. The results are presented in Table 1 and Figure 3. The C1 specimen has the highest dry density of 1.66 g/cm\({}^{3}\) and the lowest void ratio of 0.63, followed by the F1 specimen, with a dry density of 1.61 g/cm\({}^{3}\) and a void ratio of 0.58. The intact Q\({}_{3}\) possesses a loose structure, with a dry density of 1.37 g/cm\({}^{3}\) and a void ratio of 0.97. In comparison, the Q\({}_{2}\) loess has a denser structure, with a higher dry density of 1.54 g/cm\({}^{3}\) and a lower void ratio of 0.75. The natural water contents of the Q\({}_{3}\), Q\({}_{2}\), F1, and C1 specimens are 9.7%, 13.9%, 16.5%, and 13.9%, respectively. The Afterberg limits (plastic limit, liquid limit, and plasticity index) (Table 1) and the grain size distribution of the specimens (Figure 3) are similar.