Blasting construction method for rock mass containing weak crack zone

Abstract

The invention discloses a blasting construction method for a rock mass containing a weak crack zone, and belongs to the technical field of rock blasting. And the problems of poor blasting effect and safety risk caused by complex geological conditions in soft crack zone rock mass blasting are solved. According to the technical scheme, the method comprises the steps that drilling and soft zone recognition recording are conducted, the position of a soft crack zone is recognized by monitoring the advancing speed of a drill rod and rock drilling sound changes, the starting depth and the ending depth are recorded, and the length of the soft zone and filler properties are obtained; according to differential charging based on soft belt characteristics, a continuous charging mode, a weakening charging mode or an interval charging mode is adopted according to the relation between the length of the soft belt and the length of a single-section standard explosive and filler properties, string-shaped grains are adopted in the weakening charging mode, and sandbags are placed in soft belt sections to serve as inert interval blocking bodies in the interval charging mode; and the blast hole is filled and detonated, and the filling length is properly reduced for the blast hole containing the soft crack belt. According to the method, the blasting effect and the construction safety of the rock mass containing the soft crack zone can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of rock and soil blasting engineering technology, specifically to a blasting construction method for rock masses containing weak fracture zones. Background Technology

[0002] In rock blasting projects such as mining and roadbed excavation, the blasted rock mass often contains "weak fracture zones" with weak mechanical properties, such as joints, faults, interstitial soil, and karst caves. These weak zones disrupt the homogeneity and continuity of the rock mass, bringing a series of technical challenges to conventional blasting operations.

[0003] Traditional blasting methods typically design for rock masses as homogeneous media, often relying on experience to address weak or crevice zones encountered during construction. During drilling, high-pressure, high-volume drilling with slow advancement is commonly used to force passage through these weak zones, but this easily creates cavities around the borehole walls. During charging, explosives tend to accumulate in these cavities, preventing the design charge height from being achieved and resulting in abnormally high local linear charge density. This leads to two serious consequences: first, it alters the design direction of the minimum resistance line; second, the high-temperature, high-pressure detonation gases preferentially escape along this "shortcut" of the weak zone, easily generating long-distance flying debris, posing a significant safety risk. Simultaneously, the escaped gas means a large amount of explosive energy is not used for rock breaking, leading to increased explosive consumption per unit area, poorer blasting results (increased proportion of large fragments), and increased construction costs. While some existing technologies attempt to address these problems, they have several drawbacks. For example, Chinese patent CN205897979U discloses a "retractable charge spacer for engineering blasting," which achieves in-hole spaced charging through a mechanical structure. However, such devices typically require custom manufacturing in factories, resulting in high costs, and do not address how to identify weak zones and dynamically decide on charging strategies under complex geological conditions. Similarly, patent CN107830774A, concerning a "charge packing device for crossing fissures and karst caves," focuses on a specific charging structure. These solutions are all "hardware" improvements and fail to systematically solve the entire construction process from "identification-judgment-decision-execution," particularly lacking flexibility and economy when dealing with varying weak zone lengths and lithologies.

[0004] Therefore, there is an urgent need to propose a systematic blasting construction method that can safely, economically, and efficiently handle rock masses containing weak fracture zones. Summary of the Invention

[0005] The technical problem this invention aims to solve is as follows: The primary objective is to provide a blasting method for rock masses containing weak fracture zones, fundamentally preventing blasting-related safety accidents caused by the presence of weak zones. A secondary objective is to improve the energy utilization rate of explosives and reduce the consumption of explosives per unit and overall construction costs while ensuring safety. A further objective is to solve the problems of drill bit jamming and hole failure when drilling through weak zones, as well as the problems of explosive accumulation in cavities within the weak zone section of the borehole, leading to construction difficulties.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a blasting construction method for rock masses containing weak fracture zones is provided, comprising the following sequential steps: Step 1: Drilling and weak zone identification and recording. During the drilling process, monitor the drill rod advance speed and rock drilling sound in real time. When the advance speed suddenly increases and / or the rock drilling sound changes from crisp to dull, it is determined that the drill bit has entered the weak interstic zone. The hole depth at this time is immediately recorded as the starting depth H1 of the weak zone. Switch the drilling rig to manual operation mode and continue drilling using slow advance and light impact. If the drill bit gets stuck or the hole is unstable, fill the hole with wet clay and use the drill rod to lift it up and down to make the clay adhere evenly to the hole wall, forming a temporary clay wall. When the drill rod advance resistance and rock drilling sound return to normal, it is determined that the weak fracture zone has been passed. The hole depth at this time is recorded as the end depth H2 of the weak zone. The blown rock cuttings are observed, and the nature of the filling material of the weak fracture zone is recorded as rock debris or soil. Thus, the length L = H2 - H1 of the weak fracture zone and its properties are obtained.

[0007] Preferably, in step two: differentiated charging based on the characteristics of the weak zone, during the charging operation, according to the length L of the weak gap and the properties of the filling material obtained in step one, the corresponding charging method is selected and executed according to the following rules: Method A: If L ≤ the length of a single standard explosive section, then in the weak zone section corresponding to depths H1 to H2, the same continuous charging method as the normal rock mass section shall be adopted; Method B: If L > the length of a single standard explosive section, and the filling material is rock debris, then perform reduced charging: bind and fix multiple explosive sections at preset intervals to a support to form a string of explosives, and then hoist the string of explosives as a whole and position it in the section from depth H1 to H2 in the hole; the support is selected from bamboo strips, plastic pipes or rods with a certain rigidity; Method C: If L > the length of a single standard explosive charge and the filling material is soil, then interval charging is performed: no explosives are filled in the section from depth H1 to H2 in the hole. Instead, prefabricated sandbags are fixed to the support and hoisted as a whole into this section as inert interval blocking bodies. The sandbags are made of cylindrical plastic bags filled with stemming material. At the same time, the detonating charge and explosives are normally filled in the holes below the weak zone section, and the explosives are filled in the holes above in the conventional manner.

[0008] Further, in step three: borehole filling and detonation, after the charge is completed, the borehole is filled. For boreholes with weak gaps, the filling length is reduced by 8% to 12% compared to the design value of similar boreholes without weak gaps. The filling must be compacted. Finally, detonation is carried out according to the designed detonation network.

[0009] Optionally, in step one, the specific operation for forming the clay wall is as follows: after filling the hole with an appropriate amount of wet clay, repeatedly pull up and down the drill rod to open the hole, so that the clay is evenly pasted on the borehole wall.

[0010] Optionally, in step two, the length of the support used in methods B and C is slightly greater than or equal to the length L of the weak gap.

[0011] Optionally, in step two, the sandbags in method C are fixed to the support at equal intervals or continuously by binding.

[0012] The beneficial effects of this invention are as follows: Compared with existing technologies, by adopting the core principle of classification and disposal, the charge density in weak zones is specifically reduced or completely avoided, effectively preventing the high-speed leakage of detonation gases along weak zones and eliminating the resulting directional blasting flyrock from the root. Related flyrock accidents can be reduced to zero, fundamentally improving safety performance. The explosive energy acts more concentratedly on the intact rock mass to be broken, resulting in high energy utilization and a reduction in explosive consumption by approximately 14.6%. Simple, locally sourced materials such as bamboo strips and waste plastic pipes are used as support components, replacing expensive factory-customized spacers, significantly reducing material costs and simplifying and accelerating construction. Significant economic benefits; the dynamic identification + clay wall protection technology used in the drilling stage effectively solves the problems of stuck drill bits and abandoned holes when crossing weak zones, reducing the stuck drill bit rate by about 68% and the abandoned hole rate by about 72%; the binding and hoisting method used in the charging stage overcomes the problem of explosive accumulation in the cavity, making the charging height controllable and the position accurate, reducing the hole blockage rate by about 90%, ensuring the realization of the designed charging structure, improving the blasting block size, and improving construction efficiency and quality; this invention provides a clear on-site decision-making process, with simple and clear logic, which is easy for front-line construction personnel to understand and master, and is applicable to various rock blasting projects with complex and weak geological structures, with strong adaptability and operability. Attached Figure Description

[0013] Figure 1A schematic diagram showing a borehole passing through a weak gap. Figure 2 This is a schematic diagram of a soft, narrow gap-loaded explosive structure.

[0014] Label Explanation: 1. Drilling; 2. Weak seam strip; 3. Emulsion explosives; 4. Bamboo strips; 5. Cavity; 6. Sandbags. Detailed Implementation

[0015] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0016] Example 1 Please refer to Figures 1 to 2 This invention provides a blasting construction method for rock masses containing weak fracture zones, using a limestone mine blasting project as an example for detailed explanation. The project involves a bench height of 15m, borehole diameter of 115mm, borehole spacing of 4.2-5.0m, row spacing of 3.2-4.0m, the use of 70mm diameter emulsion explosive 3, with a standard explosive section length of 40cm, and the use of a D45 integrated rock drilling rig.

[0017] Step 1: Drill Hole 1 and Weak Zone Identification Record The operator used a D45 drilling rig to drill hole 1 according to the design parameters, and monitored the changes in drill rod advance speed and rock drilling sound in real time during the drilling process. When the drilling reached a depth of 8.5m, it was found that the drill rod advance speed suddenly increased, and the rock drilling sound changed from crisp to dull. It was immediately determined that the drill bit had entered the weak interstic zone 2, and the hole depth H1 = 8.5m was recorded as the starting depth of the weak zone.

[0018] Immediately switch the drilling rig to manual operation mode and continue drilling using a slow, gentle impact method. Since the drilling cuttings appeared to be broken rock and there were no signs of jamming or unstable borehole formation, clay wall treatment was not used. When the drilling reached a depth of 10.5m, the drill rod advance resistance and drilling noise returned to normal, indicating that the weak fracture zone 2 had been passed. The borehole depth at this point, H2 = 10.5m, was recorded as the end depth of the weak zone. Observing that the blown-out rock cuttings were broken rock fragments, the filling material of the weak fracture zone 2 was recorded as rock fragments. Therefore, the length of the weak fracture zone 2, L = H2 - H1 = 10.5 - 8.5 = 2.0m, was obtained.

[0019] A similar situation occurred when drilling another borehole to a depth of 6.0m, with H1 recorded as 6.0m. However, the drill bit became stuck during further drilling attempts. The operators immediately filled the hole with a suitable amount of wet clay and then repeatedly pulled the drill rod to clear the hole, ensuring the clay was evenly spread on the borehole wall, forming a temporary clay wall. Drilling continued to a depth of 7.8m, passing through a weak zone, with H2 recorded as 7.8m. The expelled material was yellow clay, confirming that the filling material of this weak interstitial zone 2 was soil, with a length L = 1.8m. Information on weak zones in all boreholes was recorded in the borehole geological anomaly registration form.

[0020] Step 2: Differentiated charges based on weak zone characteristics Before loading the explosives, prepare tools such as bamboo strips (4), a machete, and electrical tape using locally available materials. Also, prepare cylindrical sandbags (6) made by filling 70mm diameter plastic bags with clay. Based on the length L of the weak crevice zone (2) obtained in step one and the properties of the filling material, select and execute the appropriate loading method according to the following rules: For weak zones with a length L = 2.0m, greater than the 40cm length of a single standard explosive section, and filled with rock debris, method B is used to reduce the explosive charge. A bamboo strip 4, approximately 2.2m long, is used as a support. The length of the support is slightly greater than the length L of the weak gap 2. Five sections of emulsion explosive 3 are tied and fixed to the bamboo strip 4 at predetermined intervals of approximately 40cm, forming a string of explosive charges. This string of explosive charges is then hoisted and precisely positioned within the weak zone section at a depth of 8.5-10.5m in the borehole using a rope.

[0021] For weak zones with a length L=1.8m, exceeding the standard explosive length of 40cm per section, and filled with soil, method C is used for interval charging. A bamboo strip 4 approximately 2.0m long is used as a support, its length equal to the length L of the weak gap 2. Four prefabricated sandbags 6 are continuously fixed to the bamboo strip 4 by binding. In the weak zone section with a depth of 6.0-7.8m within the borehole, no explosives are loaded; instead, the sandbags 6 are hoisted as a whole into this section as inert spacers. Simultaneously, in boreholes below 7.8m in the weak zone section, detonating charges and explosives are normally loaded to the design height. In borehole sections above 6.0m, explosives are continuously loaded using conventional methods.

[0022] For other short and weak zones with a length L≤40cm, method A is adopted, and the same continuous charging method as the normal rock mass zone is used in the corresponding weak zone borehole section.

[0023] Step 3: Filling the blast hole and detonating After the explosive charge is completed, the boreholes are filled. The standard filling length for this project is 3.5-4.3m. For boreholes with weak gaps (or weak cavities), the filling length is reduced by 10% compared to the design value for similar boreholes without weak gaps, a uniform reduction of 0.3m, i.e., filling to 3.2-4.0m. The filling material is stemming clay, which must be compacted and tamped. Finally, the detonating cords and detonators of all boreholes are connected, and detonation is performed according to the designed detonation network.

[0024] After adopting this method, the occurrence of stuck pins decreased from an average of 35 times per 100 holes to 11 times, a reduction of approximately 68%; the rate of wasted holes due to drilling failure decreased from 14% to 4%, a reduction of approximately 72%; the problem of explosive accumulation in cavity 5 was overcome, making the charge height controllable and the position accurate, ensuring the realization of the designed charge structure, improving the blasting block size, increasing construction efficiency and quality, and reducing related processing time by 90%; no long-range flyrock caused by energy leakage in weak zones occurred after blasting; the rate of large rock blocks was significantly reduced, and the explosive consumption per unit volume decreased from 0.48 kg / m³ to 0.41 kg / m³, a reduction of approximately 14.6%, saving the cost of purchasing special spacers.

[0025] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A blasting construction method for rock masses containing weak fracture zones, characterized in that, Includes the following sequential steps: Step 1: Drilling and weak zone identification and recording. During the drilling process, monitor the drill rod advance speed and rock drilling sound in real time. When the advance speed suddenly increases and / or the rock drilling sound changes from crisp to dull, it is determined that the drill bit has entered the weak gap zone, and the hole depth at this time is immediately recorded as the starting depth H1 of the weak zone. Switch the drilling rig to manual operation mode and continue drilling using slow advance and light impact. If the drill bit gets stuck or the hole is unstable, fill the hole with wet clay and use the drill rod to lift it up and down to make the clay adhere evenly to the hole wall, forming a temporary clay wall. When the drill rod advance resistance and rock drilling sound return to normal, it is determined that the weak fracture zone has been passed. The hole depth at this time is recorded as the end depth H2 of the weak zone. The blown rock cuttings are observed, and the nature of the filling material of the weak fracture zone is recorded as rock debris or soil. Thus, the length L = H2 - H1 of the weak fracture zone and its properties are obtained. Step Two: Differentiated charging based on the characteristics of the weak zone. During the charging operation, based on the length L of the weak gap obtained in Step One and the properties of the filling material, the corresponding charging method is selected and executed according to the following rules: Method A: If L ≤ the length of a single standard explosive section, then in the weak zone section corresponding to depths H1 to H2, the same continuous charging method as the normal rock mass section shall be adopted; Method B: If L > the length of a single standard explosive section, and the filling material is rock debris, then perform reduced charging: multiple explosive sections are tied and fixed to a support at a preset interval to form a string of explosives, and then the string of explosives is hoisted and positioned in the section from depth H1 to H2 in the hole; the support is selected from bamboo strips, plastic tubes or rods with a certain rigidity; Method C: If L > the length of a single standard explosive charge and the filling material is soil, then interval charging is performed: no explosives are filled in the section from depth H1 to H2 in the hole, but prefabricated sandbags are fixed to the support and hoisted as a whole into this section as inert interval blocking bodies; the sandbags are made of cylindrical plastic bags filled with stemming material; at the same time, the detonating charge and explosives are normally filled in the holes below the weak zone section, and the explosives are filled in the holes above in the conventional manner; Step 3: Hole filling and detonation. After the charge is completed, the borehole is filled. For boreholes with weak gaps, the filling length is reduced by 8% to 12% compared to the design value of similar boreholes without weak gaps. The filling must be compacted. Finally, detonation is carried out according to the designed detonation network.

2. The blasting construction method for rock masses containing weak fracture zones according to claim 1, characterized in that, In step one, the specific operation of forming the clay wall is as follows: after filling the hole with an appropriate amount of wet clay, repeatedly pull up and down the drill rod to open the hole, so that the clay is evenly pasted on the borehole wall.

3. The blasting construction method for rock masses containing weak fracture zones according to claim 1, characterized in that, In step two, the length of the support used in methods B and C is slightly greater than or equal to the length L of the weak gap.

4. The blasting construction method for rock masses containing weak fracture zones according to claim 1, characterized in that, In step two, the sandbags in method C are fixed to the support at equal intervals or continuously by binding.

5. The blasting construction method for rock masses containing weak fracture zones according to claim 1, characterized in that, The length of a single standard explosive charge is 40cm.

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