# Study on Mechanism of Static Blasting-Induced Hard Rock Fracture Expansion
## 1 Introduction
[PERSON] [24] examined the effects of hole diameter, hole spacing, and hole depth on the static fracture of rock using FLAC3D software. Static blasting can successfully fracture coal rock and promote permeability growth according to [PERSON] et al. [25], who employed RFPA software to dynamically evolve the fissure expansion during the procedure. To simulate and study the variation rules of stress and displacement fields within the concrete with expansion-cracked pre-drilled voids, [PERSON] [26] employed ANSYSR software. To provide data references for engineering applications, [PERSON] et al. [27] employed COSMSQ software to investigate the expansion fracturing range of a static crusher in coal seams. To understand the rock crack expansion rule, [PERSON] [28] employed the RFPA calculation approach to model double-hole expansion fracturing based on the cloth-hole parameter test. Less research has been conducted on the practical application of static crushers and the crack expansion law in complicated stress environments. [PERSON], [PERSON] et al. [29; 30] conducted a comprehensive study on the manufacturing process and properties of Hadfield manganese steel. They specifically focused on analyzing the impact of trace elements on their wear resistance, and the effects of temperature and time of the austempering process on microstructural evolutions, phase equilibrium, mechanical properties, and fracture mode of weld metal in Hadfield steel joints were evaluated. [PERSON] et al. [31] proposed the method of subjecting hard roofs to ground fracturing, and physical simulation was used to study the control effect of ground fracturing on the strata structure and energy release. [PERSON] et al. [32] employed the CFD-DEM coupling method to conduct a detailed analysis of the macroscopic and microscopic effects of the transmission effect on diffusion and analysis of the force-chain network and anisotropic characteristics of specimens are examined from the micromechanical aspect. In this study, lab-scale crater blasting experiments on sandstone specimens under various equal biaxial compressive stresses were conducted to investigate the effects of in situ stress on blasting effects and the mechanism of in situ stress affecting rock blasting. The initiation and propagation of the crack network, morphological characteristics of the blasting crater, and distribution characteristics of blasting fragments under biaxial in situ stress were studied. Besides, the quantitative relationships between biaxial in situ stress and blasting crater parameters (diameter, area, and volume) were analyzed [33]. [PERSON] et al. [34] utilized a coupled computational fluid dynamics and discrete element method (CFD-DEM) to develop a numerical model that simulates the evolution of suffixes in various fabric anisotropy configurations under controlled flow conditions. In this study, we conducted expansion pressure tests and single-hole specimen fracturing experiments to quantitatively analyze the expansion and fracturing performance of the pill roll crusher. By combining theory and mechanics, we analyzed the action mechanism and mechanism of static crushing technology, taking into account the rational use of the pill roll. Additionally, we utilized the PFC2D inversion test procedure to demonstrate the feasibility of PFC simulation for fracturing specimens using a static crusher and to validate the rationality of parameter selection. Moreover, we analyzed the internal dynamic effects, crack extension, and distribution characteristics, as well as the development law of double-hole expansion pressure in specimens of different hole diameters, hole spacings, and circumferential pressures under the influence of expansion.