As the anisotropic behavior of sandstones and limestone along the Khorramabad-Zal expressway has not been studied, this research aims to examine the impact of layer orientation on the strength characteristics and failure patterns of layered sedimentary rocks using the Brazilian test. For this purpose, a total of 8 rock blocks were gathered from Kashkan sandstones and Sarvak limestones in three different locations along the Khorramabad-Zal highway in western Iran. The core specimens were drilled with 54 mm diameter and parallel to the laminations. Overall 150 disc-shaped specimens were subjected to Brazilian tensile strength (BTS) in ten different anisotropy angles, which refers to the angle between the loading direction and the lamination plane. The findings revealed that the highest and lowest BTS values were obtained at β = 70° and 20° for all three types of rock. After analyzing the samples that experienced the Brazilian test and examining their failure patterns, three primary modes of failure were identified: parallel to the lamination (PL), across the lamination (AL), and curved fracture (CF). Furthermore, the transitional angle, which signifies the point at which the dominant pattern of failure shifts from PL to AL or from PL to CF, was also determined.

由于尚未研究霍拉马巴德-扎尔高速公路沿线砂岩和石灰岩的各向异性行为，本研究旨在利用巴西试验研究层状取向对层状沉积岩强度特征和破坏模式的影响。为此，我们从伊朗西部霍拉马巴德-扎尔高速公路沿线三个不同地点的卡什坎砂岩和萨尔瓦克石灰岩中收集了总共 8 块岩石。岩芯样本的钻孔直径为 54 毫米，且与叠片平行。总共 150 个盘形样本在 10 个不同的各向异性角度（指加载方向与层合平面之间的角度）下承受巴西拉伸强度 (BTS)。研究结果表明，对于所有三种类型的岩石，在 β = 70° 和 20° 时获得最高和最低 BTS 值。在分析经历巴西测试的样品并检查其失效模式后，确定了三种主要失效模式：平行于叠层（PL）、跨叠层（AL）和弯曲断裂（CF）。此外，还确定了过渡角，该角表示主要失效模式从 PL 转移到 AL 或从 PL 转移到 CF 的点。