Jim Shiau, Brian Lamb, Mathew Sams, and Jay Lobwein. “STABILITY CHARTS FOR UNSUPPORTED CIRCULAR TUNNELS IN COHESIVE SOILS”. GEOMATE Journal 13, no. 39 (November 30, 2017): 95–102. Accessed April 18, 2024. https://geomatejournal.com/geomate/article/view/2916.