## 4 Results and Discussion  
### Major Cracks and Displacement  
For the convenience of presentation, the ratio of the unit load to the slope shoulder displacement is defined as the deformation rate (DR hereafter). According to DRs, the landslide evolution process can be divided into four stages, namely compression, uniform, acceleration, and failure stages. (1) Compression stage (0-40 kN): The deformation of the soil slope at this stage was mainly manifested in the obvious compression of the soils under the bearing plate and small horizontal displacement at the slope shoulder, as shown in Figure 4a. At the end of this stage, the slope shoulder displacement was 1.44 mm, and the average value of DRs was 0.033. No cracks were observed at this stage. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & **Unit Weight** & **Effective Cohesion** & **Effective Friction Angle** & **Young’s Modulus** & \multirow{2}{*}{**Poisson’s Ratio**} \\ \cline{2-5}  & **(kN/m\({}^{3}\))** & **(kPa)** & **(\({}^{\circ}\))** & **(MPa)** & \\ \hline Slip Mass & 19.88 & 16.00 & 21.00 & \(1.00\times 10^{9}\) & 0.30 \\ \hline Slide Bed & 30.00 & 5.00 \(\times\)\(10^{3}\) & 35.00 & \(1.00\times 10^{9}\) & 0.30 \\ \hline \multirow{3}{*}{Sliding Surface} & Cohesion & Friction Angle & Normal Stiffness & Tangential Stiffness & Dilation Angle \\ \cline{2-5}  & (kPa) & (\({}^{\circ}\)) & (MPa) & (MPa) & (\({}^{\circ}\)) \\ \cline{1-1} \cline{2-5}  & 0.80 & 18.00 & 2.00 & 20.00 & 18.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical and mechanical parameters of the model test materials. Figure 3: Particle size distribution of the used clay in the model test. The abscissae are in the form of logarithms, and the ordinates are mass percentages. After being air-dried and grounded, the clay was sieved through 5, 2, 0.5, 0.25, and 0.075 mm sieves in sequence. When the particle size was less than 0.075 mm, a pipette method was adopted. (2) Uniform stage (40-100 kN): While the soil slope was gradually compacted, there was an obvious horizontal displacement change at the slope shoulder. The DRs of the soil slope under each step were in the range of 0.12-0.15, the deformation of the slope showed a certain degree of stability, and the average value of DRs was 0.144. When the load reached 100 kN, a vertical crack appeared at the rear edge of the loading position, as shown in Figure 4b. (3) Acceleration stage (100-140 kN): The slope shoulder displacement increased rapidly, reaching 21.61 mm. The average value of the DRs was 0.289, which was nearly 9 times that of the compression stage. The DRs increased from 0.264 to 0.313, showing the characteristics of accelerated deformation. At this stage, as load increased, the vertical crack at the trailing edge continued to develop downward and the width of the crack gradually increased, as shown in Figure 4c. When it was 120 kN, a crack began to appear in the soils under the front edge of the bearing plate, and the crack gradually extended toward the toe of the slope as load continued. With the development of the front edge crack, the slope shoulder displacement further intensified. (4) Failure stage (140-150 kN): At this stage, the DR increased sharply to 0.793, and the slope slid down along the slip surface. The test loading system could no longer maintain a stable load and landslide occurred, as shown in Figure 4d. As can be seen, the progressive development of slope displacement was closely related to the initiation-development process of cracks. When there were no cracks, the slope displacement increased slowly or uniformly. When cracks appeared on the rear edge of  
Figure 4: Typical development stages of landslide under laboratory conditions: (**a**) compressive deformation stage (0–40 kN), (**b**) crack generation (100 kN), (**c**) crack development stage (100–140 kN), and (**d**) slope failure stage (140–150 kN). the bearing plate (corresponding to 100 kN), the displacement began to increase rapidly.