Wall length-based deformation monitoring method of brick-concrete buildings in mining area using terrestrial laser scanning

For brick-concrete buildings which are easily damaged by mining activities, this study conducted measurements using a terrestrial laser scanning and adopted the wall length as a deformation monitoring index. First, the point cloud data of the individual walls are extracted by segmenting the building-point cloud data and redistributing the wall-point cloud data. Second, after individual walls were rotated, the boundary points of all the wall-point clouds were estimated. Third, based on boundary points, the top boundary lines are fitted using the weighted iterative least squares method by applying the constraint that two adjacent (top) boundary lines intersect at a common point. Fourth, multiple regions of interest were constructed by performing downward translations on each wall, and the length of the wall was calculated at these regions. Finally, for a brick-concrete building in the coal mining area, the difference between the wall lengths of two consecutive measurements at the same interest-region was estimated to obtain the deformation information about the building. The results show that the deformation estimated using the proposed method is consistent with the actual deformation of the building as reflected by the wall fractures. The method exhibits millimeter-level accuracy in determining the wall length, with an absolute error in the range – 6 to 6 mm.