  Shale, a fine-grained sedimentary rock, is the key source rock for many of
the world's most important oil and natural gas deposits. A deep understanding
of the mechanical properties of shale is of vital importance in various
geotechnical applications, including oil and gas exploitation. In this work,
deformability, strength, and fracturing properties of Marcellus shale were
investigated through an experimental study. Firstly, uniaxial compression,
direct tension, and Brazilian tests were performed on the Marcellus shale
specimens in various bedding plane orientations with respect to loading
directions to measure the static mechanical properties and their anisotropy.
Furthermore, the deformability of Marcellus shale was also studied through
seismic velocity measurements for comparison with the static measurements. The
experimental results revealed that the transversely isotropic model is
applicable for describing the elastic behaviors of Marcellus shale in pure
tension and compression. The elastic properties measured from these two
experiments, however, were not exactly the same. Strength results showed that
differences exist between splitting (Brazilian) and direct tensile strengths,
both of which varied with bedding plane orientations and loading directions and
were associated with different failure modes. Finally, a series of
three-point-bending tests were conducted on specimens of increasing size in
three different principal notch orientations to investigate the fracture
properties of the material. It was found that there exists a significant size
effect on the fracture properties calculated from the measured peak loads and
by using the Linear Elastic Fracture Mechanics (LEFM) theory. The fracture
properties can be uniquely identified, however, by using Bazant's Size Effect
Law and they were found to be anisotropic.
