Abrasive water jet rock breaking method with secondary impact effect and composite abrasive particle

Abstract

This invention discloses an abrasive waterjet rock-breaking method with a secondary impact effect and composite abrasive particles. The composite abrasive consists of a core, an intermediate layer, and an outer shell. The method uses a nozzle to accelerate the jet and impact the rock. First, the composite abrasive particles as a whole undergo an initial impact, forming a damaged zone. Subsequently, the impact load causes the outer shell and intermediate layers of the particles to fracture as designed, releasing the core particles. The core particles, driven by the high-speed water flow, precisely impact the aforementioned damaged zone a second time. The intermediate layer has a lower body strength than the outer shell and core, and its interfacial bonding strength with adjacent layers is precisely designed to ensure stability during transport, while reliably failing during the first impact to release the core. This invention achieves sequential energy utilization through a synergistic "impact-release" mechanism, significantly improving the rock-breaking efficiency of hard rock and the utilization rate of abrasive kinetic energy.

Description

Technical Field

[0001] This invention relates to the field of rock crushing engineering technology, and in particular to an abrasive water jet rock crushing method. Background Technology

[0002] Underground space construction is crucial for the extraction, transportation, and storage of deep-earth energy. Current tunneling technologies primarily rely on traditional rock drilling and blasting, and TBM (Tunnel Boring Machine) mechanical cutting. Blasting utilizes explosives to generate detonation waves that break up rock. Traditional rock drilling and blasting methods are complex and poorly integrated, with non-explosive auxiliary processes such as drilling and ventilation accounting for 60-70% of the time. Furthermore, only 10-15% of the energy is used for rock breaking, resulting in extremely low energy utilization. Mechanical cutting relies on cutting teeth to compress and form dense, fragmented rock. However, it suffers from severe tooth wear in hard rock cutting and poor adaptability of mechanical equipment to tunnel excavation sections. Both methods, due to their inherent rock-breaking mechanisms, still present significant challenges in hard rock mass construction, exhibiting low rock-breaking efficiency, high production costs, and significant construction hazards. Therefore, it is necessary to adopt a green and efficient rock-breaking method.

[0003] Abrasive waterjet rock breaking technology is a green and efficient rock breaking method that relies on high-pressure, high-speed water flow to carry abrasive particles and utilize the high-speed impact kinetic energy of the abrasive particles to break rocks. Compared with traditional mechanical rock breaking and blasting rock breaking methods, it has advantages such as no dust pollution, no vibration damage, high rock breaking precision, and strong equipment adaptability. It is increasingly widely used in fields such as deep hard rock mining and complex geological tunnel construction.

[0004] However, existing conventional abrasive waterjet rock breaking technologies mostly use single homogeneous abrasive particles, such as quartz sand, corundum, and ordinary steel shot. When these abrasives are jetted at high speed and impact the rock surface, they can only produce a single impact, and the impact kinetic energy of the abrasive itself cannot be fully utilized. At the same time, the stress wave generated by a single impact has a limited range, the initiation and propagation rate of internal cracks in hard rock is slow, the rock breaking efficiency is low, and the abrasive utilization rate is not high. Summary of the Invention

[0005] In view of this, the present invention provides an abrasive waterjet rock breaking method with a secondary impact effect and composite abrasive particles, in order to solve the technical problems of existing single homogeneous abrasive waterjet rock breaking technology, which can only achieve a single impact, has low abrasive kinetic energy utilization rate, and poor rock breaking effect in hard rock.

[0006] The abrasive waterjet rock-breaking method with secondary impact effect in this invention includes:

[0007] Composite abrasive particles are added to a high-pressure water jet system to form a mixed flow of abrasive and water. The composite abrasive particles consist of a core particle, an intermediate layer covering the core particle, and an outer shell layer covering the intermediate layer.

[0008] The composite abrasive particles mixed with water are accelerated and sprayed onto the surface of the rock to be crushed through a nozzle. The composite abrasive particles as a whole generate the first impact on the rock surface. The load of the first impact breaks the outer shell and middle layer of the composite abrasive particles, releasing the core particles, which then conduct a second impact on the damaged area formed by the first impact.

[0009] The present invention also discloses a composite abrasive particle for use in the above-mentioned abrasive waterjet rock breaking method, comprising a core particle, an intermediate layer covering the core particle, and an outer shell layer covering the intermediate layer. The bulk strength of the intermediate layer is lower than that of the outer shell layer and the core particle. The interfacial bonding strength between the intermediate layer and the adjacent layer is higher than the load borne by the interface of the abrasive particle during the conveying process, and lower than the load borne by the interface during the first impact on the rock.

[0010] Furthermore, the overall diameter of the composite abrasive particles is 0.2–0.5 mm, and the particle size of the core particles is 0.05–0.15 mm.

[0011] Furthermore, the thickness of the outer shell layer is 5%–15% of the overall diameter of the composite abrasive particles, and the thickness of the intermediate layer is 20%–30% of the overall diameter of the composite abrasive particles.

[0012] Furthermore, the core particles are tungsten alloy particles.

[0013] The beneficial effects of this invention are:

[0014] 1. This invention relates to an abrasive waterjet rock-breaking method with a secondary impact effect and composite abrasive particles, which overcomes the limitations of single impact from traditional homogeneous abrasives. Through the three-layer structure design of the composite abrasive particles—"outer shell layer - middle layer - core"—the rock-breaking process is divided into two functionally synergistic stages: First, the integral particles, protected by a high-strength outer shell layer, undergo the first impact, forming an impact pit on the rock surface and inducing an initial crack network. Subsequently, under the triggering impact load, the weakly bonded middle layer fails as designed, releasing high-density core particles that, driven by high-speed water flow, undergo a second impact on the aforementioned pre-damaged area. The two impacts are closely linked in time and space. The first impact creates a stress concentration zone for the second, and the second impact not only allows the core particles to continue impacting the cracked area but also allows them to embed into the cracks generated by the first impact, achieving efficient crack expansion and connection. The two impacts produce a significant synergistic effect. This mechanism is particularly suitable for hard rock masses, effectively promoting efficient rock fragmentation primarily through volumetric stripping, thus achieving breakthrough improvements in rock-breaking depth, fragmentation volume, and operating speed.

[0015] 2. This invention, through structural innovation in abrasive particles, alters the transmission path and sequence of abrasive impact kinetic energy. At the moment of high-speed impact, the total kinetic energy of the entire composite particle is used for the initial rock-breaking. Simultaneously, through the "controllable interface failure" design of the intermediate layer, most of the kinetic energy carried by the core is purposefully retained. After release, the core particle, under the continuous dragging and even secondary acceleration of the high-speed water jet, concentrates its retained kinetic energy onto the first impact damage zone, achieving a sequential and progressive energy transfer. Compared to the traditional mode where kinetic energy is dissipated after a single abrasive impact, this invention allows for more complete and efficient utilization of the kinetic energy of a single abrasive particle. While achieving the same or better rock-breaking effect, the time required is shorter, and less abrasive is consumed, resulting in significant energy-saving and consumption-reducing economic benefits.

[0016] 3. In this invention, the three-layer structure of the composite abrasive particles each performs its own function, together forming a reliable and controllable "impact-release" system:

[0017] The high-strength outer shell provides wear and breakage protection during transportation, ensuring that the entire structure can withstand the first impact.

[0018] The intermediate layer, acting as a "mechanical trigger" for the secondary impact, is the weakest layer, ensuring it breaks first upon the initial impact. Its interfacial bonding strength is precisely designed to be higher than the load during transport but lower than the load during the first impact. This ensures the intermediate layer breaks before the outer shell breaks and separates from the core particle during the first impact, guaranteeing reliable release of the core particle after breakage and preventing it from dispersing and detaching from the target area along with the outer and intermediate layers. If designed as a two-layer structure with the outer shell encasing the core particle, this separation before the outer shell breaks would be impossible, preventing the outer shell from separating from the core and hindering the secondary impact. Furthermore, early outer shell breakage significantly reduces energy loss in the core particle during the first impact, and the separated core particle maintains a certain distance from the target area. This distance allows the high-speed water flow to continue propelling and accelerating the core particle, enhancing its secondary impact energy.

[0019] The core particles, after separating and being released upon the first impact, continue to impact the damaged area created by the previous impact, producing a secondary impact effect. Furthermore, due to their tiny size, the core particles can embed themselves into the cracks generated by the previous impact, thereby expanding and connecting the cracks.

[0020] Therefore, the synergistic effect of the three-layer structure of the composite abrasive particles ensures the achievement of the goal of efficient rock breaking in the second impact. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of composite abrasive particles.

[0022] Figure 2 This is a schematic diagram of an abrasive waterjet system. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Example 1: The abrasive waterjet rock-breaking method with secondary impact effect in this example includes:

[0025] Composite abrasive particles are added to a high-pressure water jet system to form a mixed flow of abrasive and water. For example... Figure 1 As shown, the composite abrasive particles consist of a core particle 3, an intermediate layer 2 covering the core particle, and an outer shell layer 1 covering the intermediate layer.

[0026] The composite abrasive particles mixed with water are accelerated and sprayed onto the surface of the rock to be crushed through a nozzle. The composite abrasive particles as a whole generate the first impact on the rock surface. The load of the first impact breaks the outer shell and middle layer of the composite abrasive particles, releasing the core particles, which then conduct a second impact on the damaged area formed by the first impact.

[0027] Figure 2 A waterjet abrasive system is demonstrated, comprising a water tank 4, a high-pressure water pump 5, a water supply valve 6, a water inlet valve 7, an abrasive hopper 8, a sand inlet valve 9, an abrasive container 10, a sand outlet valve 11, a grinding slurry pipeline 12, a mixing chamber 13, a mixing flow delivery pipeline 14, and a nozzle 15. Composite abrasive particles are added to the abrasive container 10 through the abrasive hopper 8 and the sand inlet valve 9, and then enter the mixing chamber 13 through the sand outlet valve 11 and the grinding slurry pipeline 12. Water from the water tank 4 is pumped out by the high-pressure water pump 5 and then enters the mixing chamber 13 through the water supply valve 6. Under the impact of the water flow, the composite abrasive particles are uniformly dispersed in the mixing chamber 13 and enter the nozzle 15 through the mixing flow delivery pipeline 14, where they are accelerated and sprayed onto the rock surface 16. Of course, there are abrasive waterjet systems with different structures in the existing technology. The abrasive waterjet rock-breaking method with secondary impact effect in this embodiment is universal. Existing homogeneous abrasive waterjet systems can also be used to implement the abrasive waterjet rock-breaking method with secondary impact effect described in this embodiment.

[0028] Example 2: A composite abrasive particle used in the abrasive waterjet rock-breaking method described in Example 1, such as... Figure 1As shown, it includes a core particle 3, an intermediate layer 2 covering the core particle, and an outer shell layer 1 covering the intermediate layer. The strength of the intermediate layer is lower than that of the outer shell layer and the core particle. The interfacial bonding strength between the intermediate layer and the adjacent layer is higher than the load borne by the interface of the abrasive particle during the conveying process, but lower than the load borne by the interface during the first impact on the rock.

[0029] As an improvement to the above embodiment, the overall diameter of the composite abrasive particles is 0.2–0.5 mm, and the particle size of the core particles is 0.05–0.15 mm. The small particle size of the core particles allows them to embed into the cracks generated by the first impact, preventing crack closure and producing a splitting effect, thereby achieving efficient crack propagation and rock stripping.

[0030] As an improvement to the above embodiment, the thickness of the outer shell layer is 5%–15% of the overall diameter of the composite abrasive particles, and the thickness of the intermediate layer is 20%–30% of the overall diameter of the composite abrasive particles. The relatively thin thickness of the outer shell layer and the intermediate layer allows them to reliably fracture upon the first impact, thereby releasing the core particles.

[0031] As an improvement to the above embodiment, the core particles are tungsten alloy particles. Tungsten alloy particles have high strength, high density, and high energy density, which can produce a stronger secondary impact rock-breaking effect.

[0032] In a specific implementation, the composite abrasive particles can be prepared using a suspension coating method, and the preparation process is as follows:

[0033] Tungsten alloy microparticles with a particle size of 0.05–0.15 mm were placed in ethanol or deionized water and stirred at a low shear rate of 100–200 r / min to form a uniform suspension system. A low-viscosity, weak binder was added to form a monolayer to nanoscale ultrathin film on the particle surface. By controlling the solid-liquid ratio and the amount of binder added, only weak interfacial attraction was generated between the particles, which spontaneously agglomerated into core clusters of 0.1–0.25 mm under gentle stirring. Subsequently, the particles were pre-cured at a low temperature of 40–60 °C for 0.5–1 h to fix the cluster morphology and avoid excessive agglomeration or dispersion.

[0034] The fixed-morphology tungsten alloy core clusters were redispersed in ethanol and ultrasonically dispersed for 10 min to obtain a stable suspension. An intermediate layer material, which is a low-viscosity epoxy resin or an inorganic weak binder, was added as a binder. The mixture was stirred at a low speed of 150–300 r / min and coated at 30–50℃ for 1 h–2 h to form a uniform intermediate layer on the surface of the tungsten alloy core clusters. Then, an outer shell material, which is one of alumina ceramic microparticles, silicon carbide ceramic microparticles, carbon steel microparticles, or stainless steel microparticles, was added. The mixture was stirred at a low speed for 1 h–3 h to form a complete outer shell layer on the outside of the intermediate layer. Finally, the mixture was cured at a low temperature of 60–80℃ and sieved to obtain composite abrasive particles with an overall particle size of 0.2–0.5 mm.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method of rock breaking by abrasive water jet with secondary impact effect, characterized in that: The application relates to a composite structure abrasive particle and a method for breaking rock. The composite structure abrasive particle is composed of an inner core particle, a middle layer coated outside the inner core particle and an outer shell layer coated outside the middle layer. The composite structure abrasive particle and water are accelerated and sprayed through a nozzle to the surface of rock to be broken, the whole composite structure abrasive particle impacts the rock surface for the first time, the outer shell layer and the middle layer of the composite structure abrasive particle are broken by the load of the first impact to release the inner core particle, and the inner core particle impacts the damage area formed by the first impact for the second time.

2. A composite abrasive particle for use in the method of claim 1, wherein: The composite structure abrasive particle is composed of an inner core particle, a middle layer coated outside the inner core particle and an outer shell layer coated outside the middle layer.

3. The composite abrasive particle of claim 2, wherein: The whole diameter of the composite structure abrasive particle is 0.2-0.5 mm, and the particle size of the inner core particle is 0.05-0.15 mm.

4. The composite abrasive particle of claim 2, wherein: The thickness of the outer shell layer is 5%-15% of the whole diameter of the composite structure abrasive particle, and the thickness of the middle layer is 20%-30% of the whole diameter of the composite structure abrasive particle.

5. The composite abrasive particle of claim 2, wherein: The inner core particle is a tungsten alloy particle.

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