The privately funded 10,000 Year Clock Project promotes long-term thinking. The project involves construction of a complex underground facility in West Texas to house a mechanical clock capable of keeping accurate time for 10,000 years. The clock’s underground openings include access tunnels, a raise bore shaft, and several underground chambers with complex geometries.
McMillen Jacobs Associates is providing geotechnical/geological engineering for the project. State-of-practice tools were used to collect, process, and, store geologic data. Site characterization included structural and geologic mapping at ground surface and in the access tunnel and shaft. Data collection involved vertical and horizontal scan-line geologic mapping.
Prior to initiating the field investigation, McMillen Jacobs Associates developed base maps in ARCGIS using existing aerial Lidar and photography. A ground-based Lidar scan of the shaft was “unrolled” using Lightwave 3D and exported to Adobe Photoshop to optimize intensity contrasts, creating shaft base maps. We mapped the shaft from a galloway using the intensity image maps generated from the shaft scan. These base maps were invaluable for mapping extremely continuous (>100 feet [30.5 m]) and irregular joints in the limestone.
Surface and subsurface rock mass data were compiled on stereonets for kinematic analysis of potential failure mechanisms associated with the proposed clock structures. McMillen Jacobs Associates, in collaboration with Mira Geoscience and Penguin ASI, developed a 3D model, incorporating the geologic data, and a 3D rendering of the underground openings to assist with visualization and analysis of rock mass/structure relationships. Shaft mapping information was digitized and imported into a 3D GoCad spatial model for evaluation of potential stability issues associated with underground openings. Major joints mapped in the shaft were incorporated into the model. We developed recommendations regarding siting of the underground openings based on interpretation of modeling results.
This project highlights the value of using available technological tools to collect and present complex geotechnical information. Use of 3D geologic/structure models will soon become state-of-practice for projects with complex geologic conditions and/or complex underground opening geometry.