The numerical modelling of complex surface geometries represents a challenging task in computational geotechnics. Corresponding problem classes include non-horizontal topographic surfaces (TS) in mountainous terrain, rock mass discontinuities or steep slopes, presumably inducing significant stress redistributions in the project domain that need to be considered. This raises an obvious question at the interface with geographic information systems: How to integrate point-based surveying measurements defining the TS into the numerical modelling process? In this respect, we present a step-by-step methodology based on survey data from two infrastructure projects in Austria, at the core of which NURBS surfaces are used to generate TS models with high accuracy.
The growing advancement of hardware and software technologies has paved the way to large-scale three-dimensional (3D) finite element analyses (FEA), allowing for the consideration of large topographic surfaces (TS) in combination with reasonably fine finite element mesh resolutions. In this respect, powerful features that deserve attention include but not limited to advanced preconditioning strategies to efficiently approximate the solution to boundary value problems (Chaudhary et al. 2013) and drone-enabled topographical surveying methods, such as photogrammetry or LiDAR (light detection and ranging).
The set of 3D spatial point vectors x ∈ ℝ3 obtained from the latter can subsequently be integrated into the finite element modelling process (FEMP) by employing spatial interpolation techniques, shifting the emphasis of analyses from analytical or empirical approaches to large-scale 3D FEA; typical civil engineering problems where large-scale simulations are proving increasingly beneficial comprise multi-temporal analyses of open-pit mines (Jerman et al. 2021), remediation designs for powerhouse caverns (Tschuchnigg und Dich 2020), ground pressure estimations required for the dimensioning of pressure shafts (Innerhofer und Greiner 2019) or the determination of alarm values during the construction of underground railway passages (Granitzer et al. 2021).
As a scientific contribution to this work, we propose a NURBS surface-based procedure for integrating terrestrial 3D point cloud vector data (NPTP) into the FEMP. The paper is therefore structured as follows: Section 2 gives an overview of the theoretical framework with respect to the NPTP on the basis of synthetic demonstration cases, using point cloud (PC) data from an ongoing railway construction project in Austria (Seywald und Rettenbacher 2022). In section 3, we present a case study in which the NPTP has been employed to perform FEA in course of the pumped-storage hydropower plant project Lünerseewerk II, Austria. Section 4 highlights the main conclusions.
