Key Technology Of 3D Laser Scanning In Subway Tunnel Deformation Monitoring

Real-time monitoring during the construction and operation of the subway tunnel can effectively guarantee the security operations and the stability of subway surrounding environment. Traditional convergence meter, Total Station and other deformation monitoring technology can only get single point of data, it is difficult to fully reflect the overall deformation characteristics of tunnel. Three-dimensional laser scanning technology can improve the level of automation for extract information,compared with the traditional monitoring methods which based on single point,and expressive more details of the object and influenced little by the environment and other advantages. This paper mainly research the data acquisition, preprocessing and point cloud model for the three-dimensional laser scanning technology in the subway tunnel.Take into account the banded distribution of tunnel, for the efficient management of massive point cloud data, presenting regard the tunnel axis as a reference, according to the mileage block storage points, the search method not only improves the single points’ searched speed and more efficiency extraction cross-section of the tunnel at any mileage; For the presence of terrestrial laser scanner(TLS) points’ interval farther away from the scanning distance lead to the problem of uneven density, this paper put forward a compression algorithm based on the point cloud spacing of scanning-lines and establish the compression ratio with a given threshold’s reciprocal polynomial fitting model; The large number of bolts and screws that attached on the subway shield ring plates, along with the great amount of accessories of metal stents and electrical equipments mounted on the tunnel walls, this paper proposed a filtering method for the point cloud based on the elliptic cylindrical model.Establish the deformation monitoring methods based on continuous sections and tunnel DSM using points which through compression, filtering and registration. The former is capture cross section of the interval angle such as fitting for the coordinates of the parties a two phase of the data analysis of the deformation; The latter based on DSM taken directly to analysis by superposition modeling, then offset different magnitude’s tunnel monitoring deformation.