Key Takeaways & Executive Findings
- •• The rock breaking process by high-pressure water jet on thermal rock is divided into four distinct stages: initial fluid-solid contact, intense thermal exchange, perforation and fracturing, and crack propagation and penetration. • Increasing rock temperature significantly reduces jet reflection angles and cooling time, while enhancing crack number and propagation rate, shortening critical breaking time by up to 34.5%. • Numerical simulations show that the center temperature of granite at 400 °C drops from 390 °C to 260 °C within 0.7 seconds under jet impact, indicating rapid thermal exchange. • A critical temperature and critical heat flux prediction model was established to describe the staged breaking of hot rocks, offering guidance for deep geothermal rock excavation.
Abstract
In the application of high-pressure water jet assisted breaking of deep underground rock engineering, the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear. Therefore, the fluid evolution characteristics and rock fracture behavior during jet impingement were studied. The results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages: initial fluid-solid contact stage, intense thermal exchange stage, perforation and fracturing stage, and crack propagation and penetration stage. With the increase of rock temperature, the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease, while the number of cracks and crack propagation rate significantly increase, and the rock breaking critical time is shortened by up to 34.5%. Based on numerical simulation results, it was found that the center temperature of granite at 400 °C rapidly decreased from 390 to 260 °C within 0.7 s under jet impact. In addition, a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was established. These findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.
1. Introduction
As global shallow resources become increasingly depleted, energy development is trending towards deeper exploitation. Developments in geothermal energy, metal mining, and oil and gas resources are progressively extending beyond depths of 4000 m, making kilometer-level resource extraction a norm [1]. The development of deep-earth energy is crucial for ensuring energy supply security and sustainable utilization. Simultaneously, such developments involve extensive rock excavation scenarios, thereby imposing higher demands on rock-breaking technologies.
Current methods for excavating deep-earth rock mainly involve blasting and mechanical cutter breaking [2]. Blasting relies on shock waves and gases generated by explosives to fracture rock, presenting challenges such as uncontrollable energy and significant disturbance to the surrounding rock [3]. Mechanical cutter breaking, relies on the pressure and grinding action of cutter teeth, but its efficiency significantly decreases when encountering hard rock formations, leading to increased wear on tools and higher construction costs [4,5]. High pressure water jet serves as a non-mechanical rock-breaking technology, utilizes the high kinetic energy of high-velocity water jets to convert into the strain energy and internal energy required to fracture rock. This method offers advantages such as high rock-breaking efficiency, flexible application, and reduced dust generation [6–8]. It holds significant potential and broad prospects for use in deep-earth rock excavation.
Since the mid-1980s, water jets have been commonly used as an effective cooling technology due to their high heat transfer efficiency [9,10]. For rock fragmentation excavation, utilizing the excellent characteristics of high-speed jet impact and forced cooling can effectively improve the rock breaking effect [11]. The increase in mining depth leads to a sharp rise in rock temperature. When the jet fluid encounters high-temperature rocks, significant evaporation and vaporization phenomena occur near the fluid solid interaction interface. Taking low-temperature liquid nitrogen jet as an example, in the initial stage of rock breaking, the jet impact pressure stress is dominant, and the later thermal stress is mainly in the form of tensile stress [12]. Compared with pure water jet, the vortex ring structure of liquid nitrogen jet flow field increases the turbulence energy of the flow field and promotes heat exchange between fluid and solid [13]. In addition, some scholars have found that compared with pure water jets, low-temperature supercritical CO2 (Sc-CO2) jets have excellent heat transfer performance and can
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Jianming Shangguan, Zhaolong Ge, Qinglin Deng, Yuhuai Cui, Zhi Yao (2025). Fluid evolution and fragmentation characteristics under high pressure water jet impact on thermal rock. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.02.004
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Frequently Asked Questions
What are the four stages of rock breaking by high-pressure water jet on thermal rock?
The four stages are: initial fluid-solid contact stage, intense thermal exchange stage, perforation and fracturing stage, and crack propagation and penetration stage.
How does rock temperature affect the jet reflection angle and cooling time?
With increasing rock temperature, the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease.
What is the effect of higher rock temperature on crack formation and propagation?
Higher rock temperature significantly increases the number of cracks and crack propagation rate, and shortens the rock breaking critical time by up to 34.5%.
What was observed in numerical simulation regarding granite temperature under jet impact?
The center temperature of granite at 400 °C rapidly decreased from 390 °C to 260 °C within 0.7 seconds under jet impact.
What practical guidance does this research provide?
The findings provide valuable insights to guide water jet technology assisted deep ground hot rock excavation projects, including a critical temperature and heat flux prediction model.
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