- Copyright © 2016, Environmental & Engineering Geoscience
To determine stability of rock slopes, discontinuity orientations must be measured accurately. Several methods exist for taking field measurements of discontinuity orientations. The objective of this study was to compare the traditional method of hand measuring discontinuity orientations using a Brunton compass to the more modern methods of measuring discontinuities using smartphone applications and ground-based Lidar laser scanning. The field site is a rock outcrop along Stroubles Road on Price Mountain, in Montgomery County, Virginia. The Price Mountain structure is a doubly plunging anticline exposed in a window in the Pulaski Thrust Sheet. The rock outcrop consists of a Mississippian sandstone mapped as the Upper Price Formation. The site features a set of bedding planes that dip steeply into the cut slope face, yielding toppling failures. In addition, two distinct sets of joints exist creating both planar and wedge failures in the cut slope. Using window mapping, discontinuity orientations were measured along 200 feet (61 meters) of outcrop using a Brunton compass and a smartphone application, along with a laser scan. These measurements were compared using stereonet analyses to determine the relative accuracy of the different methods. The results show a strong agreement between measurements taken with the Brunton compass and the smartphone application. However, the laser scan shows that scanner data needs calibration with field measurements and observations to yield equally good results. Remote sensing methods like laser scanning, such as terrestrial photogrammetry, cannot be used completely independent of traditional field characterization and input from experienced professionals.