Rock fracture toughness is an important parameter for the engineering geological design. In this present study, chevron straight-notched semi-circular bend (CSNSCB) specimens with wide-flat liner chevron ligament (Type-A) and long-narrow liner chevron ligament (Type-B) were designed and prepared using wire cutting method. Mode-I fracture toughness K_IC values and dimensionless stress intensity factor Y* were calculated. Moreover, these two types rock failure properties and K_IC values variation features were both analyzed. The obtained results indicate that the width of precast artificial crack is small which can ensure the flatness and symmetry of cutting plane and then the tested Stress Intensity Factor (SIF) which has smaller deviation is more accurate and reliable. The Y* values for each type of configuration were calculated using Finite Element Method (FEM) and Slice Synthesis Method (SSM) and they firstly had a decreased trend and then an increased trend with the increasing of normalized crack length α, which represent the transition from stable crack propagation (α > α_m) to unstable crack propagation (α < α_m). Compared to Type-A specimens, Type-B specimens had the calculated minimum dimensionless stress intensity factor Y*_min with smaller deviation and average K_IC values with smaller variation coefficients. Moreover, Type-A specimen has the average fractal dimension D value of 1.2209 which is 4.79% larger than that of 1.1651 for Type-B specimen, indicating its more complex crack generation and rougher fracture surfaces. That is to say, Type-B specimen has the advantages of small crack FPZ and crack propagation without deviation as well as smooth fracture surface. Since it can offset the harmful influence of rock anisotropy and good crack guided effect, its K_IC value is much satisfactory and closer to the true fracture toughness of rock-like materials.

岩石断裂韧性是工程地质设计的重要参数。在本研究中，使用线切割方法设计和制备了具有宽平衬里人字形韧带（A 型）和长窄衬里人字形韧带（B 型）的 V 形直切口半圆弯曲 (CSNSCB) 试样。计算 I 型断裂韧性K _IC值和无量纲应力强度因子Y *。此外，这两种类型的岩石破坏特性和K _IC值变化特征都进行了分析。所得结果表明，预制人工裂纹宽度较小，可以保证切割面的平整度和对称性，从而使测试的偏差较小的应力强度因子（SIF）更加准确可靠。使用有限元法（FEM）和切片合成法（SSM）计算了每种构型的Y * 值，随着标准化裂纹长度α的增加，它们先呈下降趋势，然后呈上升趋势，代表过渡从稳定的裂纹扩展 ( α > α _m ) 到不稳定的裂纹扩展 ( α < α _{m )}）。与 A 型试样相比，B 型试样计算出的最小无量纲应力强度因子Y * _min偏差更小，平均K _IC值具有更小的变异系数。此外，A型试样的平均分形维数D值为1.2209，比B型试样的1.1651大4.79%，表明其裂纹产生更复杂，断裂面更粗糙。即B型试样具有裂纹FPZ小、裂纹扩展无偏差、断口光滑等优点。由于它可以抵消岩石各向异性的有害影响和良好的裂纹引导效果，其K _IC 值非常令人满意，更接近于类岩石材料的真实断裂韧性。