Uncertainty analysis and visualization of geological subsurface and its application in metro station construction

To visualize and analyze the impact of uncertainty on the geological subsurface,on the term of the geological attribute probabilities(GAP),a vector parameters-based method is presented.Perturbing local data with error distribution,a GAP isosurface suite is first obtained by the Monte Carlo simulation.Several vector parameters including normal vector,curvatures and their entropy are used to measure uncertainties of the isosurface suite.The vector parameters except curvature and curvature entropy are visualized as line features by distributing them over their respective equivalent structure surfaces or concentrating on the initial surface.The curvature and curvature entropy presented with color map to reveal the geometrical variation on the perturbed zone.The multiple-dimensional scaling(MDS)method is used to map GAP isosurfaces to a set of points in lowdimensional space to obtain the total diversity among these equivalent probability surfaces.An example of a bedrock surface structure in a metro station shows that the presented method is applicable to quantitative description and visualization of uncertainties in geological subsurface.MDS plots shows differences of total diversity caused by different error distribution parameters or different distribution types.

Development of a 3D modeling algorithm for tunnel deformation monitoring based on terrestrial laser scanning

Deformation monitoring is vital for tunnel engineering.Traditional monitoring techniques measure only a few data points,which is insufficient to understand the deformation of the entire tunnel.Terrestrial Laser Scanning(TLS)is a newly developed technique that can collect thousands of data points in a few minutes,with promising applications to tunnel deformation monitoring.The raw point cloud collected from TLS cannot display tunnel deformation;therefore,a new 3D modeling algorithm was developed for this purpose.The 3D modeling algorithm includes modules for preprocessing the point cloud,extracting the tunnel axis,performing coordinate transformations,performing noise reduction and generating the 3D model.Measurement results from TLS were compared to the results of total station and numerical simulation,confirming the reliability of TLS for tunnel deformation monitoring.Finally,a case study of the Shanghai West Changjiang Road tunnel is introduced,where TLS was applied to measure shield tunnel deformation over multiple sections.Settlement,segment dislocation and cross section convergence were measured and visualized using the proposed 3D modeling algorithm.