Collecting Discontinuity Data at Kartchner Caverns Using LIDAR for the Purpose of Numerical Modeling

Bates, M. (University of Arizona) | Kemeny, J. (University of Arizona) | Wu, H. (University of Science and Technology Beijing) | Chen, N. (Wuhan University)

OnePetro 

Abstract:

The addition of discontinuity data into geomechanical numerical models can allow for a better understanding of the behavior of the overall rock mass. For this study, LIDAR data has been collected at the Kartchner Caverns site in Cochise County, Arizona. The discontinuity data collected at this site can be divided into two types. The first type is the overall trends of small to medium-sized discontinuities such as short joints and small fracture faces that appear consistently in the LIDAR point clouds. When added to the numerical model, these fractures can be applied throughout the entire model as joint sets. This is done by inputting statistical information representative of all of the discontinuities in the set such as the mean discontinuity plane orientation, a measure of orientation scatter such as the Fisher constant, and statistical information about joint spacing and joint roughness. The second type of discontinuity information is data collected on a single specific discontinuity such as a major fault or a persistent bedding plane. Because the interaction of these large scale features with one another and with the overall geometry of the cave openings may be relevant to the overall stability of the system, it may be advantageous to model these discontinuities individually, and input them into the numerical model in their actual location.

Introduction

Discontinuities commonly occur in rock masses. In order to ensure proper rock mass classification, safety, and long-term stability in many modern geomechanics projects, the acquisition of geotechnical information about the discontinuities is required. Geometric information about rock mass discontinuities such as dip, dip direction, location, and information related to the persistence or extent size of the discontinuities are important indices to evaluate. Finding a comprehensive, rapid and accurate method for accessing the geometrical and location information is a foundation of rock mass stability assessment. This information can be and has been traditionally measured using a manual compass and a tape measure. However, the rock masses of interest are often located in difficult to access places, and due to poor geological conditions, surveying and mapping may be difficult and dangerous. The traditional methods for engineering geological surveying and mapping work are a time-consuming, labor-intensive, costly, and highly difficult problem. To solve these problems, engineers both in the US and abroad have utilized new technologies, such as 2D digital photo interpretation, 3D digital photogrammetry, and terrestrial laser scanning (TLS). The use of 3D laser scanning technologies provides an effective, practical and advanced technical means, to solve the problems mentioned above.