With the continuous expansion of human activities to the ocean and the development of marine engineering, the stability of submarine landslides has attracted increasing attention. Monitoring data of the stability of submarine landslides under the action of strong wind and waves remain lacking because of limited observation technology and complex real sea conditions. This paper reports the long-term and continuous stability monitoring of submarine landslides under the action of wind and waves in the seabed of the Zhujiajian landslide area of Zhoushan by using a self-developed observation equipment. Effective data were collected, and variations in the pore pressure and displacement of seabed under the action of wind and waves were analyzed. Then, problems related to the change of displacement of seabed under the action of waves were explored. A typhoon event occurred during the observation period, and the significant wave height increased significantly from about 0.1 m under calm sea conditions to 0.5 m. The excess pore pressure in the sediment of 1 m under the seabed fluctuated obviously under the action of waves, with an amplitude of 2–4 kPa. By contrast, the amplitude of excess pore pressure oscillation was about 0.5 kPa under calm sea conditions, and the wave enhancement significantly increased the excess pore pressure oscillation in shallow sediments. The displacement of 0.5 mm occurred from 12 m to 13.5 m under the seabed, and the rapid accumulation or large fluctuation of lateral displacement occurred at different depths during the three periods when the significant wave height peaked.

Instability of submarine slopes in Zhoushan Islands is widespread. Frequent submarine landslides pose a great threat to offshore facilities such as submarine optical cables, reclamation projects, ports and docks. In this paper, a self-developed in-situ observation system is used to observe the deformation of submarine slopes on the southwest side of Zhujiajian Island in Zhoushan Islands for 75 days. The results show that the deformation characteristics of sediments at different depths of the submarine slope are different, and the lateral deformation of bottom sediments is about 0.75 mm, which is three times as much as the deformation of overlying sediments. The deformation process presents a step-like change, and the deformation direction is consistent with the trend of submarine slope.

Monitoring and early warning of submarine landslides could provide instant predictions for landslides, which is to avoid the destructive damage of submarine facilities such as pipelines and optical cable, etc effectively. However, researches on submarine landslide focus on numerical simulation and laboratory test, lacking support of in-situ observation data. This paper established the submarine landslide monitoring and early warning system by combining real-time monitoring data with web network platform and database technique. Based on the computational analysis of key monitoring parameters in the process of seabed deformation and sliding, the system has realized the accurate prediction and early warning of submarine landslides. The system has been applied to the submarine landslide monitoring in Zhoushan sea area, Zhejiang province, China, which has ensured the safety of offshore platforms and submarine projects in this area. The establishment of this system provides a new idea and method for submarine landslide warning.