Understanding the anisotropic fracture behavior and the characteristics of the fracture process zone (FPZ) under size effects in laminated rocks, as well as its role in rock fracturing, is crucial for various engineering applications. In this study, three-point bending tests were conducted on shale specimens with varying bedding angles and sizes. The anisotropic characteristics and size effects of fracture parameters were revealed. A comparative analysis was performed on the evolutions of FPZs computed using size effect theory, digital image correlation (DIC), and linear elastic fracture mechanics. The results divulged that: (i) With increasing bedding angles, there is a noticeable decrease in apparent fracture toughness (KICA), apparent fracture energy (GICA), and nominal strength (sNu). When the bedding angle of shale is less than 45 degrees, the crack propagation and fracture parameters are mainly influenced by the matrix. Contrary, shale with bedding angles greater than 60 degrees, the crack propagation and fracture parameters are mainly controlled by the bedding. When the bedding angle is between 45 degrees and 60 degrees, the fracture propagation evolves from permeating the matrix to extending along the bedding; (ii) The fracture parameters exhibit significant size dependent behavior, as KICA and GICA rise with increasing specimen size, but sNu falls with increasing specimen sizes. The fracture parameters align with the theoretical predictions of Bazant size effect law; and (iii) The lengths of DIC-based FPZ, effective FPZ, and inelastic zone follow Wshape variations with bedding angle. The dimensionless sizes of FPZ and inelastic zone decrease with specimen size, indicating a size effect. Furthermore, there is a negative relation between KICA and the dimensionless size of the FPZ, while sNu is positively correlated to the dimensionless size of the FPZ. This highlights the essential role of the FPZ in the size effect of rock fracture. The bedding angle exerts an influence on the FPZ, subsequently affecting the anisotropic fracture and size-dependent behavior of shale. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/

In order to realize the resource utilization of solid waste and improve the tensile strength and toughness of soil, CCR-GGBS-FA all-solid-waste binder (CGF) composed of general industrial solid waste calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS) and fly ash (FA) was used instead of cement and combined with polypropylene fiber to strengthen the silty soil taken from Dongying City, China. An unconfined compressive strength test (UCS test) and a uniaxial tensile test (UT test) were carried out on 10 groups of samples with five different fiber contents to uncover the effect of fiber content on tensile and compressive properties, and the reinforcement mechanism was studied using a scanning electron microscopy (SEM) test. The test results show that the unconfined compressive strength, the uniaxial tensile strength, the deformation modulus, the tensile modulus, the fracture energy and the residual strength of fiber-reinforced CGF-solidified soil are significantly improved compared with nonfiber-solidified soil. The compressive strength and the tensile strength of polypropylene-fiber-reinforced CGF-solidified soil reach the maximum value when the fiber content is 0.25%, as the unconfined compressive strength and the tensile strength are 3985.7 kPa and 905.9 kPa, respectively, which are 116.60% and 186.16% higher than those of nonfiber-solidified soil, respectively. The macro-micro tests identify that the hydration products generated by CGF improve the compactness through gelling and filling in solidified soil, and the fiber enhances the resistance to deformation by bridging and forming a three-dimensional network structure. The addition of fiber effectively improves the toughness and stiffness of solidified soil and makes the failure mode of CGF-solidified soil transition from typical brittle failure to plastic failure. The research results can provide a theoretical basis for the application of fiber-reinforced CGF-solidified soil in practical engineering.