Study on Dynamic Mechanical Properties of Bedding Shale Under Impact Load

Abstract

In the actual mining process of shale gas, the loads and disturbances imposed on shale by man-made activities are a dynamic process. Therefore, the study of the dynamic constitutive theory of bedding shale under impact load has important theoretical value for the study of fracturing reformation of shale reservoirs and shale gas production. The objective is to explore the dynamic mechanical properties and fracture characteristics of shale with different bedding dip angles under medium and high strain rate loading. The split Hopkinson bar (SHPB) is used to conduct rock dynamic tests on shales with bedding dip angle of 0°, 30°, 60°, 90°. Based on fractal theory, we calculate the relationship between fractal dimension and broken fragments. The results show that the compressive strength and elastic modulus of shale change slowly when loaded at low strain rate, but when loaded at high strain rate, its compressive strength and elastic modulus increase significantly. The failure mode of shale is also transitioned from splitting failure at low strain rate to shear failure at high strain rate. Under high strain rate loading, the impact of loading rate on the dynamic mechanical properties of shale is greater than that of bedding dip. The mechanical behavior of shale under dynamic load is of great significance to the safe exploitation of shale gas and other resources.

Anisotropy and Energy Evolution Characteristics of Shales: A Case Study of the Longmaxi Formation in Southern Sichuan Basin, China

“…They observed that both uniaxial compressive strength and triaxial compressive strength were minimal when β = 60 °. Chen et al [6] studied the anisotropy of the black shale in the Niutitang Formation of the Lower Cambrian. They conjectured that the bedding angle of the shale with the minimum uniaxial compressive strength is 60 °when the confining pressure of the shale is 0, 30, and 40 MPa, and that of the shale with the minimum compressive strength is 45 °at 10 and 20 MPa.…”

“…In the process of shale deposition and diagenesis, the mineral type and content, sedimentary environment, and sedimentary tectonic history of rocks [5] cause large differences in the acoustic and mechanical parameters of shale across regions. In addition, within the same region, the characteristics and occurrence of shale may differ substantially [6][7][8]. Currently, research on the anisotropy of the Longmaxi Formation shale mainly entails stress-strain curves, fracture type evaluation, and acoustic velocity determination.…”

“…Currently, research on the anisotropy of the Longmaxi Formation shale mainly entails stress-strain curves, fracture type evaluation, and acoustic velocity determination. Chen et al [6] studied the mechanical characteristics and anisotropy of the black shale of the Lower Cambrian Niutitang Formation. Hou et al [8] studied the stress-strain curve and rock fracture type of the Longmaxi Formation shale in Pengshui, Chongqing, through a uniaxial compression test.…”