Gravitational deformation mechanisms of slate slopes revealed by model tests and discrete element analysis

• The gravitational deformation characteristics of slate slopes in Taiwan were investigated.
• The deformation of slate slopes was compared with the results from physical model tests.
• The discrete element method was employed in simulations to elucidate the behavior of slate slopes.
• The major factors influencing slope deformation include slope angle, foliation angle, and material deterioration.

This study investigated the factors influencing the gravitational deformation of slate slopes prior to sliding failure, including the slope angle, foliation angle, and material deterioration. To simulate these phenomena, physical model tests were performed in the laboratory under simplified environmental conditions. Subsequently, the discrete element method was employed in simulations to elucidate the deformation behavior exhibited by slate slopes under the long-term influence of gravity and material deterioration. The physical model tests revealed two types of gravitational deformation of slate slopes. The first type is flexural toppling, which was observed in obsequent slopes with high-angle foliation. The second type is fold extrusion near the slope toe; this was exhibited by consequent slopes with low-angle foliation and is attributable to gravitation and deterioration caused by wetness. The results of the physical model test were used to verify the results of the discrete element simulation. The simulated deforming patterns were in strong agreement with the actual deformation at various slope angles. Regarding the factors influencing slope deformation, the simulation showed that the fold in consequent slopes became sharper and the folding area increased as the foliation angle increased; moreover, the folding area rose as the slope angle increased. In obsequent slopes, higher slope and foliation angles induced more substantial flexural toppling deformation.