Research On Deformation Monitoring Method Of Tunnel Sections By 3D Laser Scanning

With the massive development of municipal railroad transportation construction,public security issues like subway-induced surface deformation in the bustling area of the city has become the concern of the state and society. Especially owing to its long construction period and operation time span, factors leading to deformation of tunnel are multi-directional,multi-level and delay able.Based on the thorough analysis and conclusion of the methods of deformation monitoring in subway tunnel and section extraction of point data, this paper study the key technology of point data filtering,high accurate extraction of tunnel centerline and fast construction of arbitrary cross section, in order to establish a novel monitoring method to search for an effective way to extract tunnel section deformation rapidly and then provide a guideline for deformation monitoring and operation in subway engineering.Given the tunnel characteristics such as space-constrained, hard in the inner wall,reflection labels suitable for the special environment are designed and made to inspect the monitoring accuracy of laser scanner. By using the labels, precise engineering control network is established.Focusing on the nature of point data, a new model of filtering algorithm based on statistical characteristics and Euclid clustering with constraints is proposed to effectively erase the “error points”(like screws, bolts, metal stand,etc) on shield rings;modified ICP algorithm is used in point cloud registration to construct DSM and DEM of tunnel with high accuracy.This paper proposes a tunnel axis extraction method by using quadratic polynomial fitting for median projection of point data on XOY and YOZ plane, and then introduces a method of arbitrary cross section construction in tunnel by extracted tunnel axis, and finally achieved accurate expression of comprehensive spatial variation information.This paper carries out the related validation tasks of validity about tunnel section deformation monitoring in test area using terrestrial laser scanning technology, and proves feasibility and practicability of proposed methods through statistics andquantitative analysis of monitoring data in two phases.