Displacement Mapping of Point Clouds for Retaining Structure Considering Shape of Sheet Pile and Soil Fall Effects during Excavation

An entire large-scale retaining structure can be monitored by simulating a three-dimensional point cloud obtained by laser scanning. The behavior of a retaining structure composed of sheet piles according to excavation was analyzed by the displacement mapping method in this paper. The displacement errors can be generated due to inclined sections, U-shaped protrusions of sheet piles and cutting point clouds, and the fall and deposition of soil adhering to the sheet pile. Therefore, the analysis error was minimized by pretreatment of the point cloud considering the shape of the sheet pile before displacement mapping. For displacement mapping, the cloud to mesh (C2M) distance was calculated by segmenting the point cloud of the retaining structure into 5 rows and 20 columns, which have about 100 elements. Analysis of seven monitoring results from Day 0 to Day 35 was performed, and the maximum displacement occurrence point and the expansion of displacement with time were evaluated by displacement mapping. In an in-depth analysis after displacement mapping, it was possible to estimate the displacement variation in the vertical direction of a pile in which the excessive displacement occurred as well as the change pattern of the displacement in the horizontal direction of the entire pile head. A crack found at the top of a sheet pile occurred due to excessive displacement, which was verified by visual inspection