Quantitative visualization and characterization of stress-field evolution during fracture rapid growth is critical for understanding the mechanisms that govern the deformation and failure of solids in various engineering applications. However, the direct capture and accurate characterization of a rapidly-changing stress field during crack propagation remains a challenge. We report an experimental method to quantitatively visualize and characterize rapid evolution of the stress-field during crack propagation in a transparent disc model containing a penetrating fusiform crack. Three-dimensional (3D) printing technology and a stress-sensitive photopolymer resin were adopted to produce the disc model and to alleviate the residual processing stress that usually blurs the dynamic stress field due to overlap. A photoelastic testing system that synchronized a high-speed digital camera and a pulsed laser with a nanosecond full width at half maximum (FWHM) was used to capture the rapid evolution of the stress field in the vicinity of crack tips. The results show that the proposed method is suitable to directly visualize and quantitatively characterize the stress-field evolution during crack rapid propagation. It is proved that the crack propagation velocity is strongly governed by the stress field around the crack tips.

Hydrofracturing technology has been widely used to stimulate the tight hydrocarbon reservoirs that usually comprise heterogeneous glutenites. Hydro‐mechanical coupling and leak‐off are essential characteristics of this process and need to be properly addressed in numerical simulation, which plays an important role in quantitatively evaluating the efficiency of this technology. Due to the challenges in accurately representing the complex structure and physical properties of heterogeneous glutenites as well as hydraulic‐driven crack propagation, however, the hydro‐mechanical coupling, leak‐off, and material heterogeneity have not yet been handled satisfactorily. To overcome these challenges, we use the continuum‐based discrete element method (CDEM) to simulate the hydraulic fracturing of heterogeneous glutenites, considering hydro‐mechanical coupling and leak‐off effects. The CDEM models are constructed using the geometrical and physical parameters that were extracted from natural heterogeneous glutenites using computed tomography, X‐ray diffraction, and triaxial tests, based on image processing and reconstruction approaches. The CDEM models are composed of hydraulic fractures and microscale pores, and Darcy's law was integrated within the model to govern fluid leak‐off; this is a non‐traditional approach to leak‐off effects. The coupled finite element–discrete element– finite volume approach is used to determine the fracturing behaviours of heterogeneous models. The fracturing crack propagation and distribution patterns of homogeneous and heterogeneous models under various horizontal in‐situ stress differences are characterised by fractal theory, and the models are compared to assess the influences of material heterogeneity and in‐situ stresses on the hydraulic fracturing of heterogeneous glutenites.