Abstract The modern improved engineering technologies in the field of rock mechanics and the successful identification of the hydrocarbon potential of gas shales have turned the tight shale formations as a profitable resource for the natural gas. In the current study, Jhiri shale was tested for its strength; deformational failure attributes and mechanism at different strain rates in order to understand the dependence of the deformation rate upon various geomechanical properties. The rock samples were subjected to varied strain rates during loading and the resultant geomechanical properties such as uniaxial compressive strength (UCS), tensile strength (σt), Young's modulus (E), failure strain ( e f ), mode I and mode II fracture toughness (KIC and KIIC) and brittleness index (B1 and B2) were determined in each case. The stress-strain behaviour of the Jhiri shale was estimated at four different strain rates that varied from 1.7 × 10−2 s−1 to 7.9 × 10−5 s−1. It was found that all of the mechanical parameters of the rock that are mentioned above, except for the failure strain, increased with increasing strain rates. Such behaviour of the rock due to the strain rates may be due to stress redistribution during grain fracturing. At a strain rate of 7.9 × 10−5 s−1, UCS, tensile strength, mode I fracture toughness and mode II fracture toughness of Jhiri shale were found to be 25.45 MPa, 7.71 MPa, 0.171 MPa m1/2 and 0.083 MPa m1/2, respectively, which increased up to 50.57 MPa, 13.06 MPa, 0.565 MPa m1/2 and 0.467 MPa m1/2, respectively, at a strain rate of 1.7 × 10−2 s−1. Critical and appropriate empirical equations have been proposed to evaluate the strain-rate dependence of the mechanical properties of the rock.

中文翻译：

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应变速率对强度影响的实验研究 日日页岩破坏属性及机理

摘要 岩石力学领域现代工程技术的进步和页岩油气潜力的成功识别，使致密页岩地层成为天然气的有利可图的资源。在目前的研究中，对 Jhiri 页岩的强度进行了测试；不同应变率下的变形破坏属性和机制，以了解变形率对各种地质力学特性的依赖性。岩石样品在加载过程中承受不同的应变率，由此产生的地质力学特性，如单轴抗压强度 (UCS)、拉伸强度 (σt)、杨氏模量 (E)、破坏应变 (ef)、I 型和 II 型断裂韧性(KIC 和 KIIC) 和脆性指数 (B1 和 B2) 在每种情况下都被确定。Jhiri 页岩的应力-应变行为估计在四种不同的应变率下，从 1.7 × 10-2 s-1 到 7.9 × 10-5 s-1。发现除了破坏应变外，上述岩石的所有力学参数都随着应变率的增加而增加。由应变率引起的岩石的这种行为可能是由于晶粒破裂期间的应力重新分布。在应变速率为 7.9 × 10-5 s-1 时，发现 Jhiri 页岩的 UCS、拉伸强度、I 型断裂韧度和 II 型断裂韧度分别为 25.45 MPa、7.71 MPa、0.171 MPa m1/2 和 0.083 MPa m1 /2，分别增加到 50.57 MPa、13.06 MPa、0.565 MPa m1/2 和 0.467 MPa m1/2，应变速率为 1.7 × 10-2 s-1。