Material Unit-Based Rock Core Logging for Geotechnical Applications

The process of recording rock descriptions on boring logs (rock core logging) is the primary means of communicating rock properties that should be considered in the design and construction of underground works including foundations in and on rock, rock slope and tunnel support, and excavations in rock. The quality of rock descriptions can have far-reaching implications for the success of a project. An appropriate level of detail (as determined by the project-specific end use objective) must be collected and conveyed. In this paper, important considerations for rock core logging are discussed. First, rock descriptions should be developed for each rock material unit, defined herein as a discrete mass exhibiting a different set of geologic and engineering properties than adjacent materials. Material unit-based rock core logging minimizes the risk of overlooking design-critical rock mass conditions. Secondly, material unit descriptions should be constructed using a standard descriptive code consisting of well-defined terminology arranged in a consistent format. Standardization of the rock core logging descriptive code (at least for individual projects) will result in more useful rock descriptions to facilitate geo-engineering interpretation, spatial correlation of material units, and engineering analysis for developing design recommendations and construction considerations.