# Study on the Steepness of Landslide-Induced Wave and Nonlinear Motion of Container Ships
## 5 The Ship Motion Characteristics Caused by Landslide Surges
### The Influence of the Navigation Position on Ship Roll Characteristics  
The width of the channel determines the energy dissipation degree of the landslide-induced surge, which has different effects on the motion characteristics of ships in areas of steep attenuation and gentle attenuation. In this part, \(1\times 0.5\times 0.6\) m (length \(\times\) width \(\times\) height) sliding bodies were selected for water entry to study the influence of the navigation position on the rolling characteristics of ships.  
As can be seen in Figure 11, the rolling motion of the ship has many nonlinear effects. When the ship's zero speed is at three positions in the curved channel, the landslide-induced surge has different effects on the roll motion of the ship. Because the water entry point of the landslide is close to the second position, the landslide-induced surge spreads to the ship first and interacts with it. In other words, during a period of 0-20 s, the ship in Position #2 had a large roll motion first, followed by Position #1 and Position #3. When the period of the landslide-induced surge is close to the natural period of the roll, the roll motion of the ship has a peak value. As shown in Figure 9, the period and wavelength of the landslide-induced surge change at different times during the propagation process. When the ship is in Positions #1, #2, and #3, the maximum rolling motion of the ship occurs at different times.  
The propagation of the landslide-induced surge is irregular and random. When the period of the landslide-induced surge is an integral multiple of the natural period of ship rolling, a larger peak of rolling occur. When the ship's zero speed is at Position #3, the landslide-induced surge spreads to the vicinity of the ship. The ship has its first large roll movement within a period of 10-30 s. With the increase of time, the landslide-induced surge energy gradually decreases. When the landslide-induced surge is transmitted to the other side, the ship is subjected to the reflection effect of the shore wall, the wave is superimposed, and the composite wave acts upon the ship. The second large rolling amplitude occurs in the 70-85 s period. The rolling amplitude decreases gradually, and the ship does not lose its stability due to its self-restoring moment. At the same time, the ship's motion in the large wave surge shows obvious nonlinearity. Combining with the propagation characteristics of the wave surge in the cross-section of the river, it can be seen that the rise and change of the wave surge cause the ship's roll  
Figure 11: Rolling motion of the ship by different positions in the landslide-induced wave region.  
nonlinearity, which also indirectly reflects the ship's transverse motion nonlinearity. When the ship sails at different positions in the river, the wave steepness at #2 is the largest, resulting in the ship's roll value at #2 being the largest.  
The outside environment of the channel and the sudden change should be considered in water level. When a ship sails into a curved river channel, it should pay special attention to any secondary damage to the ship caused by the external load. When a ship is sailing in a high-wave and steep region, it shall pay attention to the submerged bow and the waves on the deck to ensure the safety of the ship's navigation.