Say Goodbye to Blasting! Mechanical Rock Breaking and Well Drilling Technology

Preface

For a long time in the past, blast-hole drilling technology has dominated the mining industry. The principle behind it is that the enormous energy released instantaneously by the explosion of explosives subjects rock to intense shock and pressure, causing it to fracture. However, as mining depth and scale continue to increase, the drawbacks of this traditional technology have become increasingly apparent.

High security risks loom.

The intense vibrations generated during blasting represent an extremely challenging issue. According to relevant research and empirical data, if the peak velocity of blasting vibrations exceeds a certain threshold, it can pose a serious threat to the stability of wellbore walls and surrounding rock masses. In a specific mining operation example, when the peak velocity of blasting vibrations reached... At a rate of 50 cm/s, obvious cracks began to appear on the wellbore walls. Measurements revealed that the crack widths had reached 5–10 mm, and their depths extended as much as 30–50 cm into the rock mass. This not only increases the difficulty and cost of wellbore support but also poses an immediate threat to the safety of underground workers, as it could trigger a collapse at any time. Moreover, blasting activities may also set off secondary hazards such as gas explosions. Gas explosions require a specific concentration range; generally speaking, when the gas concentration is between 5% and 16%, even a small ignition source can easily lead to an explosion. The high temperatures and open flames generated by blasting undoubtedly serve as major triggers for gas explosions. Once a gas explosion occurs, the powerful shockwave and intense flames it produces can instantly destroy underground facilities, causing severe casualties and enormous property damage.

The efficiency bottleneck is becoming apparent.

The traditional method of blasting for well drilling involves a complex series of procedures, with each blast requiring multiple steps such as drilling holes, loading explosives, connecting detonators, carrying out the blast, ventilating and removing smoke, and removing waste rock. Taking a medium-sized mine as an example, the drilling operation for each blast could take up considerable time and effort. It takes 8 to 10 hours for charging and wiring, another 2 to 3 hours for these operations, and at least 1 to 2 hours for ventilation and smoke removal after blasting. Removing the blasted rock can take an additional 4 to 6 hours. Thus, completing one full blasting cycle requires a total of 15 to 20 hours. Moreover, the degree of rock fragmentation after blasting is often uneven, frequently leaving large boulders behind, which necessitates additional secondary crushing operations. According to statistics, secondary crushing operations account for 10% to 20% of the total working time, significantly reducing the overall efficiency of shaft sinking. Furthermore, to ensure safety, a waiting period is required after each blast to confirm that the underground environment is safe before resuming work, which also extends the construction period to some extent.

The environmental impact is hard to eliminate.

During blasting and well-drilling operations, large amounts of harmful gases such as carbon monoxide (CO) and nitrogen dioxide (NO₂) are generated. These harmful gases not only pose health risks to workers operating underground; prolonged inhalation of carbon monoxide can lead to hypoxia, causing symptoms such as headaches, dizziness, and nausea, and in severe cases, even coma and death. Nitrogen dioxide, on the other hand, irritates the respiratory tract, triggering symptoms like coughing and shortness of breath. Moreover, when these harmful gases are released into the atmosphere, they also contribute to pollution of the surrounding environment. According to relevant monitoring data, after a medium-scale blast, the concentration of carbon monoxide in underground air can reach 500–1,000 parts per million (ppm), while the concentration of nitrogen dioxide can reach 100–200 ppm—far exceeding the national safety standards. In addition, dust generated by blasting is another serious environmental issue. This dust remains suspended in the air, not only impairing visibility but also having adverse effects on the local ecosystem and residents' daily lives. In some areas around mines, due to long-term exposure to blasting dust, crop growth is inhibited, leading to reduced yields, and the incidence of respiratory diseases among residents has significantly increased.

Mechanical rock-breaking and well-drilling technology

In the face of numerous drawbacks associated with traditional blasting-based well-drilling techniques, non-blasting mechanical rock-breaking and well-drilling technologies have emerged, demonstrating unique advantages and significant potential. Next, let’s take a closer look at the principles underlying several common mechanical rock-breaking and well-drilling technologies.

Impact rock breaking

Impact rock breaking primarily relies on rock drills to achieve its purpose. The working process of a rock drill can be divided into three key stages: impact, rotation, and dust removal. During the impact stage, the piston inside the rock drill, driven by high-pressure gas or hydraulic fluid, strikes the drill rod at an extremely high velocity. The drill rod then transmits this impact force to the drill bit, generating an instantaneous and powerful impact on the rock. According to the principle of momentum, the impact force (where is the impact force, is the mass of the piston, and is the acceleration) can be calculated as follows: For example, in a certain model of rock drill, if the piston has a mass of 5 kg and the acceleration during operation can reach 1000 m/s², the resulting impact force would be . In the rotation stage, the drill rod drives the drill bit to rotate continuously, causing the drill bit to constantly change its point of impact on the rock surface, thereby creating a circular drilling trajectory. Finally, during the dust removal stage, compressed air or pressurized water is used to expel the rock dust generated during the drilling process out of the hole, ensuring smooth drilling operations. This method of rock breaking is particularly suitable for hard rocks, as these rocks have high compressive strength and require substantial impact forces to be broken. Impact rock breaking can instantly generate enormous impact forces that exceed the compressive strength of hard rocks, thus enabling the rocks to be shattered.

Rotary rock breaking

The typical equipment used for rotary rock breaking is the coal-electric drill. The coal-electric drill achieves rock breaking through three sequential steps: penetration, rotary cutting, and powder removal. During the penetration phase, a certain axial force is applied to the coal-electric drill, enabling the drill bit to cut into the rock. The magnitude of this axial force is closely related to the rock’s compressive strength. Generally, the required axial force must satisfy the following condition: (where σc represents the rock’s compressive strength and A represents the contact area between the drill bit and the rock). For example, if the rock’s compressive strength is 50 MPa and the contact area between the drill bit and the rock is 0.001 m², the required axial force would be . In the rotary cutting phase, the drill bit rotates at high speed driven by the motor, cutting into the rock and producing fragmented rock debris. At the same time, the torque of rotation plays an important role in rotary cutting; its relationship with the cutting force F and the cutting radius r is given by . Finally, a powder-removal device expels the rock debris from the borehole. Rotary rock breaking demonstrates clear advantages when applied to soft rocks or coal seams. Soft rocks and coal seams have relatively low strength, so they do not require excessively high axial forces or torques to achieve rock breaking. Moreover, the rotary rock-breaking method can break the rock more uniformly, thereby improving the efficiency of rock breaking.

Water swelling and rock fracturing

The principle behind water-induced fracturing technology for rock breaking is to leverage the immense pressure of high-pressure water to induce cracks within the rock, thereby achieving rock fracturing and fragmentation. Specifically, holes are first drilled into the rock, and then high-pressure water is injected into these holes. As the water pressure continues to rise, the stress inside the rock gradually increases. Once the stress generated by the water pressure exceeds the rock’s tensile strength, cracks begin to form in the rock. According to the principles of rock mechanics, the rock’s tensile strength is influenced by factors such as water pressure and the radius of the borehole. Under certain conditions, when the thickness of the rock (denoted as t) satisfies a specific relationship, the rock will crack. This technology finds wide application in fields such as coal mining. In coal seam extraction, water-induced fracturing can be used to pre-treat coal seams, making them easier to mine and significantly improving mining efficiency. In tunnel excavation, this technology can reduce damage to surrounding rock masses, ensuring the stability of tunnels. Water-induced fracturing technology boasts significant advantages, including high safety and environmental friendliness with zero pollution. It eliminates the safety risks associated with blasting operations and does not produce harmful gases or dust, aligning perfectly with the modern concept of green mining.

Common mechanical rock-breaking equipment

(1) Rock drill

Rock drills come in a variety of types, with common ones including handheld, pneumatic leg-mounted, and rail-guided models. Each type has its own unique features and is suited to specific application scenarios.
Handheld rock drills feature a compact structure, small size, and light weight—typically weighing around... Weighing approximately 20–25 kg, it is easy for operators to hold and handle. Thanks to its lightweight and flexible design, it finds wide application in confined spaces—such as tunnel mining in small mines or demolition and renovation work inside buildings. However, handheld rock drills have relatively lower power output, with impact frequencies typically ranging from 30 to 35 Hz. They are best suited for softer rocks, with a rock hardness coefficient f generally around 6 to 8. When performing secondary crushing operations at small quarries, handheld rock drills can flexibly drill holes in small rock fragments, preparing them for subsequent crushing processes.
The pneumatic leg rock drill is equipped with a pneumatic leg device, which provides support and propulsion, thereby reducing the operator's physical exertion. A common... Taking the YT28 pneumatic leg-type rock drill as an example, its weight is approximately 26 kg, with an impact frequency reaching around 36 Hz and an impact energy of ≥70 J. During operation, the required air pressure typically ranges from 0.4 to 0.63 MPa, while the water pressure requirement is about 0.2 to 0.3 MPa. The pneumatic leg-type rock drill is suitable for medium-hard or hard rocks and is widely used in scenarios such as mine roadway excavation and tunnel construction. It can drill both horizontal and inclined blast holes, with typical hole diameters ranging from 34 to 42 mm and economical hole depths exceeding 5 meters. In a medium-sized mine roadway excavation project, using the YT28 pneumatic leg-type rock drill, it is possible to complete drilling 50 to 80 blast holes per day, significantly boosting construction efficiency.
Rail-guided rock drills are typically mounted on rails, using the rails for precise positioning and movement, thereby ensuring the accuracy and quality of drilling operations. With relatively high power output, they are well-suited for large-scale mining operations and foundation construction for major engineering projects—for example, in stepped mining at large open-pit mines where a large number of deep holes need to be drilled. In such scenarios, rail-guided rock drills can fully leverage their advantages to deliver efficient and highly accurate drilling performance. Rail-guided rock drills can drill blast holes with larger diameters and greater depths; generally, the diameter of the drilled holes ranges from... 50–100 mm in diameter, with drilling depths reaching 10–30 m. In the mining operations of a large open-pit mine, the use of rail-guided rock drills enables the completion of 10–15 deep holes per day, providing strong support for subsequent blasting and mining activities.

(2) Coal mining drill

The coal drill consists mainly of a motor, a gearbox, a switch, a handle, and a cable clamp device. Its working principle is that the motor drives the drill rod and drill bit to rotate via a reduction mechanism. At the same time, the operator applies a certain amount of pushing force, enabling the drill bit to cut into rock or coal seams and carry out drilling operations. The coal drill is suitable for use in coal and... Soft rock layers with f < 3 are widely used in coal mines for drilling blast holes during mining and tunneling operations. Common coal-electric drills typically have a power rating of 1.2 to 1.5 kW, a rotational speed of 520 to 640 r/min, and operate at a voltage of 127 V. On coal mine tunneling faces, using coal-electric drills to drill blast holes allows each shift (8 hours) to complete 20 to 30 blast holes. The typical diameter of these drill holes ranges from 38 to 45 mm, with hole depths ranging from 1.2 to 2 meters. During drilling, coal dust is moistened by water and then discharged through the spiral grooves of the drill rod, enabling wet drilling. This effectively reduces the concentration of dust generated during operation, typically keeping the dust concentration within the range of 2.5 to 3.7 mg/m³.

(3) Splitting bar

The working principle of the rock-splitting hammer is to split hard rocks using powerful static pressure. It mainly consists of two major components: a hydraulic power unit and a splitting device. The hydraulic power unit generates high-pressure hydraulic oil, which is then transmitted through oil pipes into the cylinder of the splitting device. This hydraulic pressure controls the piston rod inside the splitting device, causing it to extend and retract. As the piston rod moves, it drives the wedge attached to it, which in turn causes the splitting blocks sandwiched between two wedges to expand and contract. This creates tensile forces around the blocks, with forces reaching several hundred tons. Under this intense static pressure, cracks form in the rock, eventually leading to its complete fracture. In mining operations, the rock-splitting hammer can break large ore blocks into smaller pieces, making them easier to transport and process. In tunnel excavation, the rock-splitting hammer enables safe and efficient rock breaking even when blasting is not permitted, significantly reducing disturbance to the surrounding rock mass. Compared to traditional methods such as blasting and demolition hammers, the rock-splitting hammer offers significant advantages in efficiency and energy savings. It does not require large amounts of explosives or energy consumption, yet maintains high operational efficiency—each splitting cycle takes only a few seconds. Moreover, it is safe and reliable, eliminating the safety risks associated with blasting and minimizing the vibrations and noise generated by demolition hammers, thus reducing their impact on the surrounding environment. In a certain tunneling project, using splitting rods to break rock allows for completion of... per day. The tunneling progress of 3 to 5 meters ensures both construction safety and the stability of the surrounding environment.