Use of Seismic Refraction in Determining Rock Mass Anisotropy
[Thesis]
Oyan, Mohammad Najmush Sakib
Aydin, Adnan
The University of Mississippi
2019
97
M.S.
The University of Mississippi
2019
Seismic refraction is a popular method used by geological/geotechnical engineers to understand subsurface conditions. This method, along with information collected from borings, produce a realistic image of the ground beneath us. The goal of this study is to define and test a set of procedures to use seismic refraction alone to create high quality images of subsurface conditions. The focus is on areas with several meters of soil overlain by bedrock. The application of these procedures will minimize construction costs by eliminating the need for multiple boreholes. The results show that two important criteria must be met for successful application of the method: a bedrock outcrop near the survey area and an area wide enough for geophone spacing to reach the bedrock. Seismic profiles are to be laid radially in an orthogonal position, preferably intersecting in the middle or in a quarter position but not at the end. Single channel geode is used for data acquisition and Rayfract® for data processing. Surfer® and Voxler® are used for graphical representations. Seismic refraction procedures are tested at two different sites: a road cut and an abandoned quarry. In one case (road cut) analysis did not show any anisotropy, which resulted from failure to meet the second criterion (geophone spacing). Analysis from second area (quarry) exhibited a clear anisotropic nature of bedrock, confirmed by observations on the exposed outcrop in the quarry. This is a qualitative study that can predict the orientation of major joint sets if the above criteria have been met.