# Study on Mechanism of Static Blasting-Induced Hard Rock Fracture Expansion
## 2 Principles and Mechanisms of Hard Rock Fracturing Using Static Blasting Technology
### Analysis of the Static Crusher's Hard Rock Fracturing Mechanism  
When the hydration slurry of the static crushing agent is injected into the rock hole, it undergoes a hydration reaction, resulting in the expansion of the slurry within the confined space. This expansion creates an increasing pressure over time. Simultaneously, the pore wall exerts a reaction force on the crushing agent, which is equal in magnitude and direction. This reaction force causes the crushing agent to gradually transform from a hydrated fluid to a solid state. At this stage, the crushing agent can be considered solid, similar to the rock, but with a lower solid modulus of elasticity and higher plastic deformation compared to the rock. Because of these characteristics, the volume change of the crushing agent can be likened to rheological and elastic strain.  
Assuming that the solid modulus of elasticity of the crusher is very low, in this scenario, the static pressure on the pore wall will persist even if the volume of the crusher is rapidly increasing. During rheological depressurization, the main directions of flow for the crusher are the rock's pore wall and fractured fracture surface. However, the creation of rheological depressurization significantly reduces the expansion pressure of the crushing agent on the rock hole, which can negatively impact the rock's fracturing. Therefore, it can be inferred that the expansion pressure is primarily caused by the crusher's elastic strain. In the study of the crusher's transformation into a solid, increasing the contribution of elastic strain (in combination with rheological strain) can enhance the expansion pressure of the crusher and improve its ability to fracture the rock.  
Figure 4: Multiple free surfaces in rock fractures.  
The rheology of the static crusher offers certain advantages. However, due to variations in the composition, mixing, injection methods, gravity, and other factors of the crusher slurry, the expansion rates of its different components differ, resulting in the simultaneous occurrence of different elastic strains. Consequently, high expansion pressure becomes localized within the crusher slurry. The high reaction force generated when this high expansion pressure interacts with the crusher itself leads to a redistribution of the localized high expansion pressure region to the local low expansion pressure region, thus balancing the expansion pressure.  
In conclusion, as depicted in Figure 5, controlling the high elastic strain of the static crushing agent and maintaining specific rheology can enhance the stabilization of expansion pressure. As a result, the tensile stress on the rock will increase proportionally to the tensile stress in the rock hole along the axis of the hole surface, leading to the formation of multiple radial cracks. These cracks propagate over time, causing additional pore walls to fracture, ultimately resulting in the formation of a continuous fractured zone. The static crusher is then employed to complete the process of fracturing the rock.