To investigate the tensile behavior of rock bedding planes, a series of direct tensile tests were conducted on cylindrical limestone and sandstone specimens with a distinct bedding plane perpendicular to the axial direction. Different tensile strain rates of the bedding plane areas within the magnitude range from 10 −6 to 10 −2 s −1 were considered. The results indicate that the limestone fracture surfaces maintain the original roughness of bedding planes with few grain fractures. However, the sandstone fracture surfaces display many intergranular and transgranular fractures and are rough at the grain scale. The stress–strain curves of limestone specimens can be divided into elastic deformation stage and yield stage (the nonlinearity of yield stage is weaker with the increase of strain rate), while that of sandstone specimens develop in a nonlinear way accompanied by plastic deformation throughout the loading process. The strain rate significantly affects the tensile deformation and strength of the tested specimens (except the average deformation modulus of sandstone specimens). The elastic modulus, average deformation modulus, peak strain and tensile strength increase as strain rate goes up and have a linear relation with the logarithm of strain rate under the tested strain rate range (namely, under a relatively low strain rate range).

中文翻译：

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不同应变率下具有层理面的石灰岩和砂岩的直接拉伸行为

为了研究岩石层理面的拉伸行为，对具有垂直于轴向的不同层理面的圆柱形石灰岩和砂岩试样进行了一系列直接拉伸试验。考虑了在10 -6 到10 -2 s -1 范围内的层理平面区域的不同拉伸应变率。结果表明，石灰岩断口面保持层理面的原始粗糙度，晶粒裂隙较少。但砂岩裂隙面多为沿晶和穿晶裂缝，颗粒尺度粗糙。石灰岩试件的应力-应变曲线可分为弹性变形阶段和屈服阶段（屈服阶段的非线性随着应变速率的增加而减弱），而砂岩试件则在整个加载过程中以非线性方式发展，伴随着塑性变形。应变速率显着影响试验试样的拉伸变形和强度（砂岩试样的平均变形模量除外）。弹性模量、平均变形模量、峰值应变和拉伸强度随着应变速率的增加而增加，并在测试应变速率范围内（即在相对较低的应变速率范围内）与应变速率的对数呈线性关系。