USING BRAZILIAN DISK TESTS TO DEFINE TENSILE STRENGTH OF TWO LITHOLOGIES FROM THE UPPER OATKA CREEK MEMBER OF THE MARCELLUS SHALE
Open Access
Author:
Cronin, Michael Brett
Area of Honors:
Geosciences
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Terry Engelder, Thesis Supervisor Terry Engelder, Thesis Supervisor Peter J Heaney, Thesis Honors Advisor
Keywords:
Marcellus Shale Tensile Strength
Abstract:
The Brazilian Disk test was used to evaluate the Mode I tensile strength of two lithologies (calcareous gray shale and shaley limestone) within the Upper Oatka Creek Member of the Marcellus Shale. Disks with dimensionless thickness ratios between 0.26 and 0.84 were systematically prepared with bedding oriented parallel to the disk face and loaded diametrally until failure at two different strain rates. It was discovered that there was no distinction between loading rates of 0.500mm/min and 1.000mm/min, and that average indirect tensile strengths of the two lithologies were 11.07 MPa (std . dev. = 1.45) and 11.14 MPa (st. dev. = 2.15) respectively. It was also noted that observed tensile strength was not a strong function of dimensionless sample geometry between L/D values of 0.4 and 0.6. Outside of this interval, disk preparation quality control became much more difficult for thinner and thicker samples. While the difference in strength between the two lithologies was not significant, the tensile strength values in the calcareous gray shale were much more consistent and obeyed one peak load (kN) vs. dimensionless sample thickness to diameter ratio trend, while the shaley limestone results displayed several possible trends indicative of a more complex mechanical stratigraphy. The implication is that additional lithofacies are required in limey units to properly describe their mechanical behavior. The future goal of this study is to incorporate current results of this study to existing sequence stratigraphy models in the Appalachian Basin to attempt to develop a predictive geomechanical –stratigraphic model.
