Expansive soil, characterized by widespread fissures, is a special type of soil prone to localized fissure propagation, leading to failure and instability, often resulting in landslides. Numerous studies have applied fracture mechanics theory to analyze soil failure along fissures, but no standardized testing method has been established. This paper reviews existing soil fracture toughness testing methods, designs an integrated system combining digital image correlation(DIC) technique and electrical resistance testing, and employs the Cracked ChevronNotched Brazilian Disc (CCNBD) method to assess the fracture toughness of expansive soil. The deformation and internal damage accumulation processes of the specimens were monitored. The K & Iukcy;c and K & Iukcy;& Iukcy;c of expansive soil were tested at moisture contents of 15 %, 20 %, and 25 % using specimens with three different crack length ratios (a/R). The role of water was explored by injecting water into the fissures. The results showed that K & Iukcy;c of expansive soil ranged from 10 to 36 kPa center dot m0.5, with a linear negative correlation to moisture content and a proportional relationship to tensile strength, having a proportionality coefficient of 0.331. The K & Iukcy;& Iukcy;c ranged from 20 to 70 kPa center dot m0.5,and it is greater than K & Iukcy;c under the same conditions. Based on the load, internal damage, strain, and fissure area during the tests, the failure process of expansive soil along fissures was divided into four stages: initial deformation stage(I), quasi-elastic deformation stage(II), fissure extension stage(III), and failure stage(IV). Water injection into the fissures reduced the soil's fracture toughness, with a more significant reduction as a/R increased and the failure showed progressive behavior. The CCNBD method, combined with DIC technique and electrical resistance testing, effectively measures the fracture toughness of soil, aiding in understanding the failure mechanism along fissures and providing a basis for preventing and controlling landslides and other hazards in expansive soils.

来源平台：ENGINEERING GEOLOGY