Brazilian Test for Tensile Failure of Anisotropic Shale under Different Strain Rates at Quasi-static Loading

Abstract

Shale formations show obvious anisotropic characteristics in their mechanical properties due to pronounced bedding planes and natural fractures. This anisotropic behavior generally creates complex fracturing networks and is crucial to gas shale stimulation. Although much research has been done to study the anisotropic compression behaviors of shale with static and quasi-static strain rates, there are limited investigations addressing the anisotropic tensile behaviors of shale at quasi-static strain rate. In this work, the anisotropic tensile behaviors of Longmaxi shales were studied systematically at different strain rates from 10 −5 to 10 −2 s −1 by performing Brazilian splitting tests. Testing results reveal the tensile strength anisotropy, rate dependency, and the stimulated fracture pattern morphology. The results show that the orientation between the applied force and bedding direction has an obvious effect on the tensile strength and fracture pattern. The rate dependency of shale under different loading rates is different for shale samples with various orientations. It was suggested that a complex tensile fracture pattern can be easily formed when using a high loading rate. The result sheds light on how to stimulate a complex fracturing network during field hydraulic fracturing treatment.

An alternative approach to obtaining the direct tensile strength of the rocks from the indirect tensile strength

“…[47] tarafından çalışmada BÇD ve akustik emisyon deneylerinde yükleme yönüne bağlı olarak farklı tabaka yönelme durumlarında (farklı açılarda) anizotropik şist numunelerinin karakteristikleri incelenmiştir. [48] şeyl numuneleri üzerinde anizotropik çekme davranışını inceledikleri çalışmalarında Brezilya testinde sistematik olarak gerinim hızlarını değiştirmişler ve tabakalanma düzlemlerinin yükleme doğrultusu ile yaptıkları açıya bağlı olarak dolaylı ÇD'nın değişimini araştırmışlardır. Bu çalışmaların sonuçları, kayaçların litolojik özelliklerinin dayanım değeri üzerinde etkili olduğuna örnek olarak gösterilebilir.…”

Three‐dimensional discrete element simulation of indirect tensile behaviour of a transversely isotropic rock

“…The effect of anisotropy on the tensile behaviour of transversely isotropic rocks has been extensively studied for decades using analytical, experimental and numerical approaches [8,[10][11][12][13][14][15][16][17][18][19][20][21]. The published results have shown that the tensile behaviour of transversely isotropic rocks depends largely on the orientation of weakness planes (e.g., bedding plane and foliation plane) with respect to the loading direction.…”

Study on the Microscale Tensile Properties of Lower Cambrian Niutitang Formation Shale Based on Digital Images

“…He and Afolagboye [22] systematically studied the effect of weakly laminated surfaces and interlayer bonding forces on shale failure strength and fracture morphology by performing Brazilian splitting tests. Wang et al [23] studied the anisotropic tensile behaviour of the Longmaxi shale at different strain rates by performing Brazilian splitting tests. Nath and Mokhtari [24] used optical technology and image processing technology to study the relationship between shale tensile strength and the energy required for failure under Brazilian splitting test conditions.…”