Strain distribution based geometric models for characterizing the deformation of a sliding zone

Distributed optical fiber sensing technology was used to establish a deformation monitoring system for the Majiagou landslide in the Three Gorges Reservoir area, China. The monitoring methods were introduced. The strain distribution of the optical sensing cables can be utilized to accurately detect the position of the sliding zone and to reveal the movement of the landslide, which was verified by comparisons with GPS and inclinometer data. It was found that the strain distributions of the optical sensing cable in the sliding zone were different. In order to reasonably explain the shear deformation of the sliding zone based on the strain distribution and its changes, three geometric models reflecting the spatial relationship between the sliding zone and the optical cable were proposed. The results indicate that the strain distributions depend on the angle between the optical sensing cable and the sliding zone, the position of the main slip surface within the sliding zone, as well as the shear deformation of the sliding zone. The correctness of the geometric models is verified by the monitored strain distribution of the sensing cable. The proposed geometric models can be used to precisely describe the deformation of the sliding zone and reveal the evolutionary stage of the landslide.