Hard rock presplitting blasting method of replacing down-the-hole drill with rotary drill

Abstract

This invention belongs to the field of pre-splitting blasting technology, specifically relating to a hard rock pre-splitting blasting method using a roller cone drill rig instead of a down-the-hole drill rig. The hard rock pre-splitting blasting method includes eight stages: parameter design, drill rig preparation, hole drilling, hole acceptance, charge packing, network connection inspection, blasting implementation, and post-blast acceptance. This invention optimizes the drilling parameters of the roller cone drill rig, adjusts the pre-splitting hole network parameters, matches the charge structure and detonation method, and establishes a closed-loop process control system. This achieves efficient, precise, and low-cost application of the roller cone drill rig in hard rock pre-splitting blasting, significantly improving hole drilling efficiency and pre-splitting quality, and ensuring the safety of open-pit mine slope mining. It overcomes the shortcomings of existing down-the-hole drill rigs in hard rock (f≥10) pre-splitting blasting, such as low hole drilling efficiency, large drilling deviation, discontinuous pre-splitting, high drill bit wear, and easy drill bit jamming and rod breakage.

Description

Technical Field

[0001] This invention belongs to the field of pre-splitting blasting technology, specifically relating to a hard rock pre-splitting blasting method that uses a roller cone drill to replace a down-the-hole drill. Background Technology

[0002] Pre-splitting blasting is one of the core technologies for slope control in open-pit mines. Its principle involves drilling a row of closely spaced pre-splitting holes along the designed slope outline before the main blasting zone. A small amount of explosive is placed in each hole and detonated first, forming a through-splitting crack. This reduces the damage to the slope rock mass caused by the blasting vibrations in the main blasting zone, ensuring the stability and smoothness of the slope. The effectiveness of pre-splitting blasting directly affects the safety of open-pit mining, slope lifespan, and subsequent support costs.

[0003] Currently, down-the-hole (DH) drills are commonly used for pre-splitting blasting in open-pit mines. DH drills are characterized by their suitable borehole diameter, maneuverability, and adaptability to medium-hardness rock formations. They are particularly well-established in use in medium-hard rock formations with a Protodyakonov hardness coefficient f ≤ 10. However, under conditions of hard rock with f≥10 (such as high magnetite, granite, quartzite, etc.), down-the-hole (DH) drills have revealed some technical defects, including low drilling efficiency: relying on the principle of impact crushing, the drilling speed of DH drills in hard rock is significantly reduced, and the drilling time for a single hole is often 3-5 times that of soft rock, which seriously affects the construction progress; large drilling deviation: the drill rod is prone to deflection in hard rock, and the deviation of hole position, hole depth, and inclination angle is difficult to control, and the actual qualified hole rate is generally less than 70%, resulting in discontinuous pre-cracks or deviation from the design outline; high drill bit wear: the carbide teeth of the DH drill bit wear out rapidly in hard rock, and the drill bit needs to be replaced every tens of meters of drilling. At the same time, accidents such as stuck drill and broken rod are prone to occur, increasing construction costs and safety risks; poor pre-crack quality: due to hole position deviation and hole diameter limitations, the charge linear density is difficult to control precisely, and pre-cracks often have problems such as faults and uneven width, resulting in low half-hole rate of slopes and the need for a lot of reinforcement and support in the later stage. To address these technical problems, those skilled in the art have attempted to improve them by increasing drilling accuracy control and optimizing the charge structure. However, due to the inherent limitations of down-the-hole drilling rigs in terms of their impact crushing and slag removal capabilities, their fundamental defects in hard rock are difficult to overcome completely.

[0004] Roller cone drills are the mainstream equipment for drilling in the main blasting area of ​​large open-pit mines. They rely on drilling pressure to crush and grind the rock with the roller cone drill bit, and are equipped with a high-power rotary mechanism and a powerful slag removal system. In hard rock with f≥10, they have significant advantages such as high drilling efficiency, good borehole verticality, intact borehole walls, and long drill bit life. Currently, roller cone drills are widely used for large-diameter (250mm-310mm) deep-hole blasting in the main blasting area, with a hole-forming speed 3-5 times that of down-the-hole drills, and drilling deviation controlled within the centimeter level.

[0005] Because the borehole diameter of the roller cone drill (≥250mm) is much larger than the conventional borehole diameter of pre-splitting blasting (≤165mm), it will result in an excessively high charge linear density, causing excessive damage to the slope during blasting; if the hole spacing of the large-diameter drill is designed according to the traditional pre-splitting blasting design, it will result in an excessively wide hole spacing, making it difficult for the pre-splitting cracks to be continuous; the drilling parameters of the roller cone drill (drilling pressure, rotation speed, air volume) were originally designed for large holes in the main blasting zone, and directly applying them to pre-splitting holes will cause problems such as hole wall collapse and deviation.

[0006] To date, no complete technical solution has been found for the systematic application of roller cone drilling rigs in pre-splitting blasting of hard rock slopes in open-pit mines, nor has a dedicated set of process parameters and quality control methods been found for roller cone drilling rig pre-splitting blasting. This invention provides a hard rock pre-splitting blasting method that uses roller cone drilling rigs to replace down-the-hole drilling rigs. It integrates roller cone drilling rigs with specific process steps and parameters, enabling the true application of roller cone drilling rigs in pre-splitting blasting scenarios. Each step and parameter is clearly defined, rather than merely remaining theoretical. Summary of the Invention

[0007] To address the shortcomings of the existing technology, this invention provides a hard rock pre-splitting blasting method that uses a roller cone drill as an alternative to a down-the-hole drill. It aims to overcome the limitations of existing down-the-hole drills in pre-splitting blasting of hard rock (f≥10), such as low hole formation efficiency, large drilling deviation, discontinuous pre-splitting, high drill bit wear, and easy drill bit jamming and rod breakage, as well as the long-standing technical prejudice in the field that "roller cone drills have large hole diameters and are not suitable for pre-splitting blasting."

[0008] This invention optimizes the drilling parameters of the roller cone drilling rig, adjusts the pre-splitting hole mesh parameters, matches the charge structure and detonation method, and establishes a closed-loop process control system. This enables the efficient, precise, and low-cost application of the roller cone drilling rig in hard rock pre-splitting blasting, significantly improving hole formation efficiency and pre-splitting quality, and ensuring the safety of open-pit mine slope mining.

[0009] To achieve the above objectives, the present invention adopts the following technical solution.

[0010] A method for hard rock pre-splitting blasting using a roller cone drill as an alternative to a down-the-hole drill includes the following steps: Step 1, Parameter Design: Design the drilling parameters, pre-splitting hole parameters, and charging parameters for the roller cone drilling rig; Step 2, Drilling Rig Preparation: Select a roller cone drilling rig, adjust the positioning system and tilt adjustment device, and accurately lay out the hole position; Step 3, Hole Formation: Drill using the method of "light pressure and slow drilling, gradually increasing pressure", and clean and seal the hole after completion; Step 4, Hole Inspection: Inspect each hole individually, and drill additional holes if any fail to meet the requirements; Step 5, Charge Packing: Air column interval coupling charge is used, and composite mud is layered and compacted for packing; Step 6, Network Connectivity Check: Check the continuity of the detonation network; Step 7, Detonation: Demarcate the warning area, clear the site, and then detonate; Step 8, Post-detonation inspection: Inspect the blast zone after detonation.

[0011] Furthermore, in step 1, the drilling parameters for the roller cone drilling rig are: drilling pressure 180-280kN, rotation speed 25-30r / min, and slag removal air volume 30-35m³. 3 / min; Pre-splitting hole parameters: hole diameter 250mm, hole spacing 120cm, hole depth is the design height of the slope plus 0.5-1.0m for extra depth; Charge parameters: waterproof emulsion explosive is used, charge linear density is 200-400g / m, air column interval coupling charge is used, the interval distance is 20-30cm, the filling length is 2.0-3.0m, detonation is carried out simultaneously in the same section, and the detonator is set in the middle of the charge section.

[0012] Further, step 2 specifically involves: selecting a 250mm diameter roller cone drilling rig; adjusting the total station + GPS dual positioning system to ensure that the layout deviation is ≤5cm; adjusting the tilt adjustment device to lock the drill rod swing angle to ≤±0.5° and ensure that the drilling tilt deviation is ≤±0.3°; and laying out the pre-splitting hole positions according to the design parameters, using paint and wooden stakes for double marking.

[0013] Further, step 3 specifically involves: adjusting the machine body to be level, aligning the drill bit with the center of the hole, adjusting the drill rod angle according to the designed inclination angle, and locking the drilling rig positioning and inclination device; starting the drilling rig according to the designed drilling parameters; "light pressure, slow drilling, and gradual pressure increase" specifically means: the drilling pressure is 30%-40% of the rated drilling pressure; the rotation speed is 40%-50% of the rated speed; parameters are adjusted every 2-3 meters of drilling, with a single increase in drilling pressure not exceeding 15% of the rated value and a single increase in rotation speed not exceeding 10% of the rated value, gradually increasing to the designed rated drilling parameters until entering the normal uniform speed hole formation construction state; during drilling, the slag discharge situation in the hole is monitored in real time through the slag discharge air volume, and when encountering sections with developed rock fissures, the rotation speed is reduced to 20 r / min and the slag discharge air volume is increased to 30 m³ / min. 3 / min; reduce drilling pressure and rotation speed 50cm before the end of the hole to control the hole depth; after reaching the designed depth, continue ventilation and slag removal for 3-5 minutes to thoroughly clean the rock powder and gravel in the hole and ensure the integrity of the hole wall; after the hole is formed, seal the hole opening with a plastic plug.

[0014] Further, step 4 specifically involves: the acceptance criteria matching the design parameters of the borehole mesh: borehole position deviation ≤ 5cm, borehole depth deviation ≤ ±20cm, borehole inclination angle deviation ≤ ±0.3°, borehole walls intact without collapse, no water accumulation or large pieces of gravel inside the borehole, and pre-splitting holes arranged in a straight and uniform manner.

[0015] Further, step 5 specifically involves: the charge length being the borehole depth minus the filling length; using air column interval coupling for charging, with an interval of 20-30cm, controlling the pushing speed to ≤0.15m / s, and pushing the charge cartridge to the bottom of the pre-splitting hole; placing the detonator in the middle of the charge section, with the detonator lead wire extending along the hole wall and fixed to the outside of the hole opening; and after the charge is completed, using rock powder-clay composite stemming mud to compact and fill the hole in layers.

[0016] Further, step 6 specifically involves: the detonation network is arranged along the outside of the pre-splitting hole; after the network is connected, it is confirmed that there are no blockages, broken pipes, or missing connections, and then the blasting warning stage is entered.

[0017] Furthermore, step 7 specifically involves: in accordance with the requirements of the open-pit mine blasting safety regulations, delineating a warning range of ≥300m, and after clearing the site, the person in charge of detonation shall issue a detonation warning signal of ≥5s through an alarm or siren, and after confirming again that there are no safety hazards in the blasting area and its surroundings, issue a detonation command.

[0018] Furthermore, step 8 specifically involves waiting ≥15 minutes after detonation before personnel enter the blast zone for on-site inspection.

[0019] The above steps are managed in a closed loop, and the next step can only proceed after the previous step has been accepted.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0021] 1. Significantly improved hole-forming efficiency: By using a roller cone drill instead of a down-the-hole drill, and with optimized drilling parameters and a "light pressure, slow drilling, and gradual pressure increase" process, the drilling time for a single hole is 45-50 minutes, which is more than 50% shorter than that of a down-the-hole drill (110 minutes in actual measurement), thus significantly accelerating the construction progress. Roller cone drills employ a crushing and grinding mechanism to break rocks, which differs from the impact crushing mechanism of down-the-hole drills. In hard rock with f≥10, impact crushing has high energy reflectivity and low energy utilization, while crushing and grinding have higher energy conversion efficiency and larger crushing volume per unit time. Setting the drilling pressure in the range of 180 to 280 kN ensures effective penetration of the roller cone into hard rock while avoiding abnormal wear or jamming of the drill bit due to excessive pressure. Matching the rotation speed of 25 to 30 r / min with the drilling pressure allows the roller cone teeth to form a continuous breaking surface between the breaking pits, avoiding idle rotation or repeated breaking. The "light pressure, slow drilling, and gradual pressure increase" start-up method avoids initial hole position deviation and reduces correction time; the adaptive adjustment of reducing rotation speed and increasing air volume in the fissure section prevents "drill blockage" and drilling stoppage caused by poor slag discharge.

[0022] 2. The quality of hole formation is significantly improved, with a hole qualification rate of over 98%. The pre-splitting holes are arranged in a straight and uniform manner, and the hole walls are intact without any collapse. Positioning: The total station + GPS dual positioning system controls the layout deviation to within 5cm, and the system is equipped with paint and wooden stakes; At the process control level: "Light pressure and slow drilling" at the start avoids initial hole deviation; 50cm before the end of the hole, the pressure is reduced and the speed is decreased, eliminating the excessive depth or deviation caused by the release of the drill rod's elastic deformation.

[0023] 3. Fundamental improvement in pre-crack continuity and slope quality; slope half-hole ratio can reach over 90%. For a 250mm borehole diameter, the optimal borehole spacing of 120cm was determined through theoretical calculations and field tests. This ensures that the stress waves between the boreholes are superimposed to form continuous cracks, while avoiding the increased costs and excessive damage to the slope caused by excessively dense drilling. The use of a "low linear density + air column spacing" charge structure ensures that the explosive energy is evenly distributed along the depth of the hole, avoiding the "upper crack but lower crack" phenomenon caused by the energy concentration at the bottom of the hole and insufficient energy at the opening of the hole in traditional continuous charges. The air column is used for intermittent coupling of explosive charges (interval 20-30cm). The air column plays a dual role of buffering and energy storage. The initial shock wave is attenuated by the air column and then acts on the borehole wall, reducing the crushing zone of the borehole wall. At the same time, the expansion of the air column does work, prolonging the quasi-static pressure time of the explosive gas on the borehole wall, which is conducive to the penetration and propagation of the crack. All pre-splitting holes are detonated simultaneously using detonators of the same section. The stress waves generated by each hole are superimposed between the holes to form a continuous tensile stress field, ensuring that the pre-splitting crack is penetrated in one go.

[0024] 4. Drill bit wear is significantly reduced, eliminating the need for frequent drill bit replacements and reducing subsequent slope repair and support costs.

[0025] 5. Overcoming technical biases: It breaks through the traditional perception in this field that "rotary cone drills have large boreholes and are not suitable for pre-splitting blasting," and provides a new, efficient, and reliable technical solution for slope control in hard rock open-pit mines. Detailed Implementation

[0026] The technical solutions of this invention will now be clearly and completely described. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] A method for hard rock pre-splitting blasting using a roller cone drill as an alternative to a down-the-hole drill includes the following steps: Step 1: Drilling parameters for the roller cone drill: drilling pressure 180-280kN, rotation speed 25-30r / min, slag removal air volume 30-35m³ / min. 3 / min; Pre-splitting hole parameters: hole diameter 250mm, hole spacing 120cm, hole depth is the design height of the slope plus 0.5-1.0m extra depth; Charge parameters: waterproof emulsion explosive is used, charge linear density is 200-400g / m, air column interval coupling charge is used, the interval distance is 20-30cm, the filling length is 2.0-3.0m, the same section is detonated simultaneously, and the detonator is set in the middle of the charge section; Step 2: Select a 250mm diameter roller cone drill rig, equipped with a ball-tooth drill bit and high-strength wear-resistant drill rod; adjust the drilling pressure, rotation speed, and slag discharge air volume to the design parameters; check the wear of the drill bits and replace any worn-out drill bits; adjust the total station + GPS dual positioning system to ensure that the layout deviation is ≤5cm; adjust the inclination adjustment device and lock the drill rod swing angle to ≤±0.5° to ensure that the drilling inclination deviation is ≤±0.3°; accurately lay out the pre-splitting hole positions according to the design parameters, and use paint and wooden stakes for double marking; Step 3: Adjust the machine body to be level, align the drill bit with the center of the hole, adjust the drill rod angle according to the designed inclination angle, and lock the drilling rig positioning and inclination device; start the drilling rig according to the designed drilling parameters, with the drilling pressure at 30%-40% of the rated drilling pressure and the rotation speed at 40%-50% of the rated speed; adjust the parameters every 2-3 meters, increasing the drilling pressure by no more than 15% of the rated value and the rotation speed by no more than 10% of the rated value in a single increment, gradually increasing to the designed rated drilling parameters until entering the normal uniform speed hole formation construction state, avoiding excessive initial drilling pressure that could cause hole position deviation; during drilling, monitor the slag discharge in the hole in real time through the slag discharge air volume, and when encountering sections with well-developed rock fissures, reduce the rotation speed to 20 r / min and increase the slag discharge air volume to 30 m³ / min. 3 / min; reduce drilling pressure and rotation speed 50cm before the end of the hole to accurately control the hole depth; after reaching the designed depth, continue ventilation and slag removal for 3-5 minutes to thoroughly clean the rock powder and gravel in the hole and ensure the integrity of the hole wall; immediately after the hole is formed, seal the hole opening with a plastic plug to prevent loose rocks and rainwater from falling in; record the drilling parameters, hole formation time, and actual hole depth of a single hole, and fill in the "Roller Cone Drilling Rig Pre-splitting Hole Formation Record"; Step 4: Hole-by-hole inspection. The inspection standards strictly match the design hole network parameters: hole position deviation ≤ 5cm, hole depth deviation ≤ ±20cm, drilling inclination angle deviation ≤ ±0.3°, hole wall intact without collapse, no water accumulation or large pieces of gravel inside the hole, and pre-splitting holes are arranged in a straight line and evenly. Unqualified holes are immediately marked and a re-drilling plan is formulated. Before re-drilling, the drilling rig positioning and inclination device are recalibrated to ensure that the hole quality of the re-drilled holes meets the standards. All pre-splitting holes pass the inspection and proceed to the next process. Step 5: Use waterproof emulsion explosives. The charge length is the borehole depth minus the filling length. Use air column interval coupling for charging, with an interval of 20-30cm. Hold the charging rod and push steadily, controlling the pushing speed to ≤0.15m / s. Push the charge smoothly to the bottom of the pre-splitting hole, ensuring that the charge is tightly attached to the hole wall to prevent it from falling or shifting. Place the detonator in the middle of the charging section. Gently lead the detonator lead wire along the hole wall and fix it to the outside of the hole opening with waterproof tape to protect it from damage. Immediately after charging, carry out the filling operation. Use rock powder-clay composite stemming mud to fill in layers and compact it. It is strictly forbidden to shorten the filling length. Step 6: The detonation network is arranged along the outside of the pre-splitting holes, away from the main blasting area and the work passage to prevent equipment crushing and human damage; after the network is connected, the detonation transmission performance is tested with a professional testing instrument to confirm that there are no blocked pipes, broken pipes, or missing connections; the blasting technical supervisor conducts the final acceptance of the detonation network, checking the correctness of the network connection, conductivity, and protection. After the acceptance is qualified, the supervisor signs to confirm and enters the blasting warning stage; Step 7: In accordance with the safety regulations for open-pit mine blasting, delineate a warning zone of ≥300m and set up warning posts at key locations such as roads, intersections, and work faces around the warning zone; each warning post is equipped with a dedicated person, walkie-talkie, and alarm, and the responsibilities, communication passwords, and emergency response procedures of each warning post are clearly defined; each warning post personnel shall conduct a comprehensive clearing of the area under their responsibility, ensuring that all irrelevant personnel, vehicles, and equipment are evacuated to a safe area, and report to the detonation supervisor one by one after the clearing is completed; after receiving reports from all warning posts that the clearing is complete, the detonation supervisor shall issue a detonation warning signal of ≥5s through the alarm or siren, and after confirming again through the walkie-talkie that there are no safety hazards in the blasting area and its surroundings, issue the detonation command; Step 8: After detonation, wait ≥15 minutes until the smoke and dust in the blasting area dissipate and the slope stabilizes. Then, the blasting technical supervisor shall lead certified blasters and safety management personnel into the blasting area to conduct on-site inspections, address potential hazards, and compile records.

[0028] Example 1.

[0029] Construction conditions: A large open-pit metal mine with a slope height of 12m and a rock hardness coefficient of f=12~14.

[0030] Construction equipment: KY-310 roller cone drill, 250mm diameter drill bit, equipped with ball tooth drill bit and high-strength wear-resistant drill rod.

[0031] Parameter design: Drilling parameters: Drilling pressure 220kN, rotation speed 28r / min, cuttings removal air volume 32m³ 3 / min; Pre-splitting hole parameters: hole spacing 120cm, hole depth 12.8m (slope height 12m + extra depth 0.8m); Charge parameters: waterproof emulsion explosive, charge linear density 300g / m, air column interval charge (interval 25cm), filling length 2.5m, simultaneous detonation in the same section.

[0032] Construction steps: Step 1: Drilling rig preparation: Debug the total station + GPS dual positioning system, ensuring the layout deviation is ≤5cm; debug the tilt adjustment device, locking the drill rod swing angle to ≤±0.5°; use both paint and wooden stakes to mark the hole positions; Step 2, Hole Formation: Adjust the machine body to be level, align the drill bit with the center of the hole, adjust the drill rod angle and lock it; start the drilling rig and drill using the "light pressure, slow drilling, and gradual pressure increase" method: the drilling pressure should be 30% of the rated drilling pressure; the rotation speed should be 40% of the rated speed; adjust the parameters every 3m of drilling, with a single increase in drilling pressure not exceeding 15% of the rated value and a single increase in rotation speed not exceeding 10% of the rated value, gradually increasing to the designed rated drilling parameters until normal uniform speed hole formation is achieved; when drilling to the fracture development section, reduce the rotation speed to 20r / min and increase the slag removal air volume to 30m³ / min. 3 / min, reduce drilling pressure and rotation speed 50cm before the end of the hole, and continue ventilation and slag removal for 4min after reaching the design depth. Immediately after the hole is formed, seal the hole opening with a plastic plug. Step 3, Hole Drilling Acceptance: Each hole is inspected individually. Hole position deviation ≤ 5cm, hole depth deviation ≤ ±20cm, inclination angle deviation ≤ ±0.3°, hole walls intact without collapse, no water accumulation or large stones inside, and pre-splitting holes arranged in a straight, uniform line. Pass rate 98%; Step 4, charging and packing: Use a charging rod to slowly feed the explosive roll into the bottom of the hole, ensuring that the explosive roll is tightly attached to the hole wall. The detonator is placed in the middle of the charging section. The packing is done by layering and compacting rock powder-clay composite stemming mud, with a packing length of 2.5m. Step 5, Network Connection and Inspection: The detonation network is arranged along the outside of the pre-splitting hole. The detonation transmission performance is tested with a professional testing instrument to confirm that there are no blocked pipes, broken pipes, or missing connections. Step 6, Demolition Implementation: Delineate a 300m warning zone, set up warning posts, and issue the detonation command after the site is cleared; Step 7, Post-detonation inspection: After detonation, wait 20 minutes before entering the blast zone for inspection; Results: Average drilling time per hole: 46 min; Hole qualification rate: 98%; Slope half-hole rate: 92%; Peak blasting vibration: 2.8 cm / s; Pre-cracks are continuous and without faults.

[0033] Comparative Example 1 (Down-the-hole drilling rig).

[0034] Under the same mine conditions and lithology, pre-splitting blasting was carried out using a conventional down-the-hole drill (150mm borehole diameter). Drilling parameters: drilling pressure 50kN, rotation speed 45r / min, air volume 15m³ / min. 3 / min, hole spacing 150cm, continuous coupled charge, charge linear density 400g / m.

[0035] Results: Single hole drilling time 110 min, hole completion rate 62%, slope half-hole rate 40%, stuck drill 3 times / 100 holes, pre-cracks discontinuous.

[0036] Comparative Example 2 (Roller Cone Drill Rig + Unoptimized Parameters).

[0037] The same roller cone drilling rig was used, but with standard main blast zone parameters: drilling pressure 350kN, rotation speed 40r / min, and air volume 20m³ / min. 3 / min, hole spacing 120cm, charge linear density 600g / m (continuously coupled charge).

[0038] Results: Single-hole drilling time was 32 minutes, hole wall collapse rate was 35%, blasting vibration peak was 5.6 cm / s (exceeding the limit), and hole qualification rate was only 45%, making it unsuitable for pre-splitting blasting.

[0039] Comparative Example 3 (Roller cone drill + excessive hole spacing).

[0040] A roller cone drill was used, with a hole spacing of 200cm and a charge linear density of 500g / m. The other parameters were the same as in Example 1.

[0041] Results: The pre-cracks showed obvious faults and discontinuities, and the slope half-hole ratio was only 45%, requiring secondary slope repair in the later stage.

[0042] Comparative Example 4 (Roller cone drill + low drilling pressure).

[0043] A roller cone drilling rig was used with a hole spacing of 120cm. Only the drilling pressure was adjusted, and low drilling pressure was used. The drilling pressure was set to 150kN. There was no "light pressure and slow drilling, gradually increasing pressure" method. Other parameters such as drilling speed and air volume were completely consistent with those in Example 1.

[0044] Effects: Slow drilling rate, excessive deviation in borehole verticality, poor borehole formation regularity, resulting in disordered blasting energy distribution, deviation in the extension direction of pre-cracks, and extremely poor slope formation quality.

[0045] Comparative Example 5 (Roller cone drill + high rotation speed).

[0046] Using a roller cone drilling rig, with standard drilling pressure, hole spacing, and charging parameters, only the rig's rotation speed was adjusted, increasing it to 65 r / min. There was no "light pressure, slow drilling, and gradual pressure increase" method. All other construction parameters were completely consistent with those in Example 1.

[0047] Effects: High-speed friction and impact between the drill bit and the rock mass generate severe vibrations, which accelerates drill bit wear, results in poor uniformity of borehole diameter and irregular hole shape; the diffusion of blasting energy is disordered, the pre-cracks extend discontinuously and are uneven in width, the half-hole forming quality is poor, and the protective effect of pre-crack blasting is significantly reduced.

[0048] The above embodiments and comparative examples show that only by using the combination of the roller cone drilling rig, specific drilling parameters, hole pattern parameters and charge parameters described in this invention can efficient and high-quality pre-splitting blasting be achieved in hard rock slopes with f≥10, resulting in unexpected technical effects.

Claims

1. A method for hard rock pre-splitting blasting using a roller cone drill rig instead of a down-the-hole drill rig, characterized in that, Includes the following steps: Step 1, Parameter Design: Design the drilling parameters, pre-splitting hole parameters, and charging parameters for the roller cone drilling rig; Step 2, Drilling Rig Preparation: Select a roller cone drilling rig, adjust the positioning system and tilt adjustment device, and accurately lay out the hole position; Step 3, Hole Formation: Drill using the method of "light pressure and slow drilling, gradually increasing pressure", and seal the hole after completion; Step 4, Hole Inspection: Inspect each hole individually, and drill additional holes if any fail to meet the requirements; Step 5, Charge Packing: Air column interval coupling charge is used, and composite mud is layered and compacted for packing; Step 6, Network Connectivity Check: Check the continuity of the detonation network; Step 7, Detonation: Demarcate the warning area, clear the site, and then detonate; Step 8, Post-detonation inspection: Inspect the blast zone after detonation.

2. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, In step 1, the drilling parameters for the roller cone drill are: drilling pressure 180-280kN, rotation speed 25-30r / min, and slag removal air volume 30-35m³. 3 / min; Pre-splitting hole parameters: hole diameter 250mm, hole spacing 120cm, hole depth is the design height of the slope plus 0.5-1.0m for extra depth; Charge parameters: waterproof emulsion explosive is used, charge linear density is 200-400g / m, air column interval coupling charge is used, the interval distance is 20-30cm, the filling length is 2.0-3.0m, detonation is carried out simultaneously in the same section, and the detonator is set in the middle of the charge section.

3. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, Step 2 specifically involves: selecting a 250mm diameter roller cone drilling rig; adjusting the total station + GPS dual positioning system to ensure that the layout deviation is ≤5cm; adjusting the tilt angle adjustment device to lock the drill rod swing angle to ≤±0.5° and ensure that the drilling tilt angle deviation is ≤±0.3°; and laying out the pre-splitting hole positions according to the design parameters, using paint and wooden stakes for double marking.

4. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, Step 3 specifically involves: adjusting the machine body to be level, aligning the drill bit with the center of the hole, adjusting the drill rod angle according to the designed inclination angle, and locking the drilling rig positioning and inclination device; starting the drilling rig according to the designed drilling parameters; "light pressure, slow drilling, and gradual pressure increase" specifically means: the drilling pressure should be 30%-40% of the rated drilling pressure; the rotation speed should be 40%-50% of the rated rotation speed; parameters should be adjusted every 2-3 meters of drilling, with a single increase in drilling pressure not exceeding 15% of the rated value and a single increase in rotation speed not exceeding 10% of the rated value, gradually increasing to the designed rated drilling parameters until entering the normal uniform speed hole formation construction state; when encountering sections with well-developed rock fissures, reduce the rotation speed to 20 r / min and increase the slag discharge air volume to 30 m³ / min. 3 / min; reduce drilling pressure and rotation speed 50cm before the end of the hole; after reaching the designed depth, continue ventilation and slag removal for 3-5 minutes; after the hole is formed, seal the hole opening with a plastic plug.

5. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, Step 4 specifically involves: matching the design parameters of the borehole mesh to the acceptance criteria: borehole position deviation ≤ 5cm, borehole depth deviation ≤ ±20cm, borehole inclination angle deviation ≤ ±0.3°, intact borehole walls without collapse, no water accumulation or large pieces of gravel inside the borehole, and pre-splitting holes arranged in a straight and uniform manner.

6. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, Step 5 specifically involves: the charge length being the borehole depth minus the filling length; using air column interval coupling for charging, with an interval of 20-30cm, and a pushing speed ≤0.15m / s, pushing the charge cartridge to the bottom of the pre-splitting hole; placing the detonator in the middle of the charge section, with the detonator lead wire extending along the hole wall and fixed to the outside of the hole opening; and after the charge is completed, using rock powder-clay composite stemming mud to compact and fill the hole in layers.

7. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, Step 6 specifically involves: the detonation network is arranged along the outside of the pre-splitting hole. After the network is connected, it is confirmed that there are no blockages, broken pipes, or missing connections, and then the blasting warning stage is entered.

8. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, Step 7 specifically involves: defining a warning zone of ≥300m; after clearing the area, the person in charge of detonation issues a detonation warning signal of ≥5s via an alarm or siren; and after confirming again that there are no safety hazards in the blasting area and its surroundings, issuing the detonation command.

9. The hard rock pre-splitting blasting method using a roller cone drill to replace a down-the-hole drill as described in claim 1, characterized in that, Step 8 specifically involves waiting ≥15 minutes after detonation before personnel enter the blast zone for on-site inspection.

10. The hard rock pre-splitting blasting method using a roller cone drill instead of a down-the-hole drill according to any one of claims 1-9, characterized in that, Each step is managed in a closed loop, and the next step can only begin after the previous step has been accepted.