Roadway blasting and tunneling method based on super-shearing fracture of layered hard rock structure surface

Abstract

This invention relates to the field of mining blasting and tunneling technology, and discloses a tunnel blasting and tunneling method based on the super-shear fracturing of layered hard rock structural surfaces. The blasting method first induces super-shear fracturing of the hard rock structural surfaces through blasting. The generated Mach cone high-frequency shock wave and Rayleigh wave jointly promote the generation of shear and tensile cracks on both sides and the surface of the structural surfaces. Then, a fractured cavity is formed by delayed blasting through deep and shallow holes. The tunneling method utilizes the fractured cavity formed by blasting and the surrounding cracks. The cutting head of the roadheader penetrates into the cavity and laterally spins and breaks the rock, which is beneficial to the breaking of hard rock. This invention forms a highly efficient and coordinated rock breaking system of "blasting-machinery" for layered hard rock tunnels, which solves the problems of low rock breaking efficiency, large cutting tooth wear, unreasonable explosive dosage, and insufficient free surface in traditional hard rock tunneling.

Description

Technical Field

[0001] This invention belongs to the field of mining blasting and tunneling technology, specifically a tunnel blasting and tunneling method based on super-shear fracturing of layered hard rock structural planes. Background Technology

[0002] Tunnel excavation is a core link in the coal mine mining and excavation process. The existing technologies have several main problems, including: 1. Conflict between explosive usage and free face: Traditional blasting requires a large number of blast holes and explosives to achieve effective rock breaking, but the amount of explosives used underground is strictly limited; traditional drilling creates free faces, which increases the workload, and the free face range of the blast holes is small, resulting in large energy loss and poor breaking effect.

[0003] 2. Rock mass energy is not fully utilized: A large amount of elastic potential energy is accumulated inside layered hard rock. Traditional methods have not effectively released this energy to assist in rock breaking, and only rely on external blasting energy, resulting in low rock breaking efficiency and high cost.

[0004] 3. Poor mechanical rock breaking conditions: Hard rock is in a triaxial compression state with high strength. The cutting teeth of the roadheader face great resistance to rock breaking, resulting in severe wear, slow tunneling speed, and high cost due to frequent replacement of cutting teeth.

[0005] 4. Poor synergy between blasting and mechanical rock breaking: Traditional blasting results in uneven rock fragmentation, with many large rock pieces. Mechanical cutting is time-consuming, failing to form an efficient synergy system of "blasting pre-splitting - mechanical rock breaking". Summary of the Invention

[0006] The purpose of this invention is to provide a tunnel blasting and tunneling method based on super-shear fracturing of layered hard rock structures, which solves the problems of low rock breaking efficiency, high cutting tooth wear, unreasonable explosive dosage, and insufficient free surface in traditional hard rock tunneling. It achieves precise blasting, coordinated release of rock mass energy and mechanical cutting tooth rock breaking, improves the tunneling speed of hard rock tunnels, reduces the cost of hard rock tunneling, and reduces tunnel deformation and disaster risks.

[0007] This invention is achieved through the following technical solution: The tunnel blasting method based on overshear fracturing of layered hard rock structural planes includes the following two stages: The first stage is blasting-induced super-shear fracture of the structural surface: blast holes are arranged along the slope of the structural surface and detonated simultaneously; during the blasting process, the explosive stress wave propagates along the structural surface, inducing super-shear fracture of the structural surface, generating Mach cone high-frequency shock waves on both sides of the structural surface, and Rayleigh waves on the surface of the structural surface at the same time; the Mach cone exerts shear damage on the rock mass on both sides of the structural surface, and the Rayleigh waves exert tensile damage on the surface of the structural surface, jointly causing cracks to form on the surface and both sides of the structural surface.

[0008] The second stage involves delayed blasting of the hard rock on both sides of the structural plane: by identifying the start and end times of the high-frequency pulse signal of the Mach cone, the completion time of the supershear fracture of the structural plane is determined, and the completion time is used as the delayed detonation time of the delayed blasting.

[0009] Furthermore, vibration sensors are installed at the intersection of the structural surface and the tunnel outline. The vibration sensors are connected to a data acquisition instrument to monitor the high-frequency pulse signals generated by blasting in real time. The data acquisition instrument analyzes the pulse signals to identify the start and end times of the Mach cone high-frequency pulse signals.

[0010] Furthermore, the arrangement of the blast holes for delayed blasting is as follows: in the hard rock on both sides of the structural plane, the subsequent blasting blast holes are symmetrically arranged along the direction parallel to the structural plane. There are multiple rows of subsequent blasting blast holes on each side, arranged in an alternating manner of one row of deep holes and one row of shallow holes, and the adjacent rows of deep holes and shallow holes are staggered.

[0011] Furthermore, internal thread grooves are machined on the inner walls of both deep and shallow holes.

[0012] Furthermore, based on the determined delayed detonation time, subsequent blasting holes are detonated, with the detonation sequence being deep holes first, followed by shallow holes.

[0013] Furthermore, after the deep hole is detonated, the shallow hole is detonated at 25ms intervals. The deep hole first produces a large-scale fracture, and the shallow hole further breaks up large pieces of rock.

[0014] The tunnel excavation method based on the overshear fracturing of layered hard rock structures, which employs a roadheader for lateral rotary shearing after the aforementioned tunnel blasting method, includes the following steps: After the delayed blasting is completed, a fractured cavity is formed in the tunnel cross section. The cutting head of the roadheader is pushed into the fractured cavity formed by the blasting to perform lateral rotary cutting and rock breaking. The cutting teeth of the cutting head cut and peel off the fractured rock from the side, and the blasting fracture network is used to assist in the rock peeling.

[0015] Furthermore, after breaking the rock, the cross-section is trimmed.

[0016] Furthermore, after completing the excavation of a section of the tunnel, the steps of over-shear blasting, delayed blasting, and lateral rotary shearing are repeated to continue the tunnel excavation until the entire tunnel is completed.

[0017] The beneficial effects of this invention compared to the prior art are as follows: 1. This invention induces overshear fracturing of the structural plane through blasting, generating Mach cone high-frequency shock waves on both sides of the structural plane and Rayleigh waves on the surface of the structural plane. The Mach cone high-frequency shock waves cause shear failure on the hard rock on both sides of the structural plane, while the Rayleigh waves cause tensile failure on the surface of the structural plane. This invention cleverly utilizes the layered structural features of hard rock, inducing overshear fracturing through blasting to release rock mass energy to assist in rock breaking and reduce the roadway's dependence on external blasting energy. After the rock mass energy is released, it also reduces stress concentration in the roadway later, reducing the risk of roadway deformation and failure and the occurrence of disasters.

[0018] 2. The blasting induces overshear fracture of the structural surface. The gas generated by the blast then ejects debris from the structural surface, providing new free boundaries for subsequent blasts. The stress wave from the subsequent blast generates reflected tensile waves at the fracture surface. Hard rock is resistant to compression but not tension, which is conducive to the complete fracturing of hard rock.

[0019] 3. The blasting holes on both sides of the structural surface are arranged with alternating deep and shallow holes, so that the explosive energy is evenly distributed in the direction of tunnel excavation. The deep holes are detonated first to create large-scale cracks, and the shallow holes are detonated later to break up large pieces of rock, which increases the degree of rock fragmentation and avoids the shortcomings of previous blasting methods that only broke the bottom of the blasting hole.

[0020] 4. The inner walls of the deep and shallow holes on both sides of the structural surface are internally threaded grooves, which guide the initiation of explosive cracks, ensuring uniform axial fragmentation of the borehole and making full use of the entire borehole. Moreover, the internally threaded grooves increase the friction of the explosive plugging inside the borehole, improving the compactness of the explosive plugging.

[0021] 5. The method of this invention creates blasting cavities locally in the tunnel cross-section, rather than through full-section drilling and blasting, thus reducing the amount of explosives and drilling work. The cutting head of the roadheader rotates at high speed, and the cutting teeth on the cutting head laterally cut and break the rock. Compared to the previous direct frontal rock breaking, the lateral rock breaking cutting teeth rotate at a higher speed, and the rock changes from a three-dimensional compression state to a unidirectional compression state, reducing the rock strength and facilitating rock fragmentation. Attached Figure Description

[0022] Figure 1 It is a schematic diagram of the layout of the structural surfaces and blast holes in a hard rock tunnel; Figure 2 This is a schematic diagram illustrating the principle of blast-induced supershear of structural surfaces; Figure 3 This is a schematic diagram of the cracks formed after the blasting of a blast hole containing an internal threaded groove; Figure 4 This is a schematic diagram of the cutting head of a roadheader laterally rotary cutting and breaking rock inside the blasting and crushing trough. Detailed Implementation

[0023] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0024] See Figure 1 and Figure 4 This embodiment proposes a tunnel blasting and excavation method based on super-shear fracturing of layered hard rock structural planes. This method is applicable to tunneling of layered hard rock tunnels in coal mines, especially for steep slopes and high-hardness layered hard rock tunnels with a uniaxial compressive strength of ≥100MPa. It solves the problems of low efficiency and high wear of cutting teeth when relying solely on mechanical rock breaking, and can be widely used in mine blasting and excavation engineering, as well as adaptable to similar tunneling operations in underground layered hard rock engineering. Specifically, it includes the following three stages: Phase 1: Structural Surface Overshear Demolition 1. Hole Layout: Along the dip of the structural plane, boreholes are constructed manually or mechanically on the structural plane, with a spacing of 600mm, a diameter of 43mm, and a depth of 2m. Ensure the borehole axis is parallel to the structural plane, with a hole position deviation not exceeding ±50mm and a hole depth deviation not exceeding ±100mm. After drilling, use high-pressure air to remove rock powder from the boreholes, ensuring the boreholes are clean and free of debris (see...). Figure 1 ).

[0025] 2. Weakening treatment: Inject clean water into each borehole, the injection volume is 1 / 2 of the borehole depth (about 1m), soak for 5-10 minutes to weaken the friction coefficient between the structural surfaces (from 0.6-0.8 to 0.3-0.4), which is conducive to the subsequent blasting to induce super-shear fracture; if the structural surfaces are dry, the soaking time can be extended to 10-15 minutes.

[0026] 3. Explosive loading and sealing: The emulsion explosive is loaded into the borehole in sections, with the length of each section controlled to be about 1m (in this embodiment, each section is 300mm long, and there are 3 sections in total). The explosive loading density is 0.8-1.0kg / m. After the explosive is loaded, the borehole is sealed with stemming clay and water stemming clay. The sealing section is 1m long. When sealing the borehole, ensure that it is dense to avoid the phenomenon of blasting during the explosion.

[0027] 4. Sensor Placement and Detonation: Two to three vibration sensors are placed at the intersection of the structural face and the roadway outline. These sensors are connected to a data acquisition unit. After commissioning, all boreholes on the structural face are detonated using electric detonators of the same section. During detonation, operators must evacuate to the warning area and confirm the detonation command via explosion-proof walkie-talkie.

[0028] 5. Fracturing Confirmation and Determination of Delay Time: During the blasting of the structural plane, the explosive stress wave propagates along the structural plane, generating Mach cone high-frequency shock waves on both sides of the structural plane, and simultaneously forming Rayleigh waves on the surface of the structural plane. The Mach cone high-frequency shock waves cause shear failure of the rock mass on both sides of the structural plane, while the Rayleigh waves cause tensile failure of the structural plane surface, jointly causing cracks to form on the surface and sides of the structural plane (see...). Figure 2 ).

[0029] Vibration sensors are used to monitor the high-frequency pulse signals generated by the blast in real time. Data acquisition devices are then used to analyze the pulse signals, identify the start and end times of the Mach cone high-frequency pulse signals, and determine the time when the structural surface completes super-shear fracture (i.e., the time from initiation to the disappearance of the pulse signal). This time is used as the delayed initiation time for subsequent blasts, and the data is recorded.

[0030] Phase 2: Delayed blasting on both sides of the structural plane 1. Hole Layout: In the hard rock on both sides of the structural plane, subsequent blasting holes are symmetrically arranged along a direction parallel to the structural plane. Multiple rows of subsequent blasting holes are set on each side, using an alternating arrangement of one row of deep holes (43mm diameter, 2m depth) and one row of shallow holes (43mm diameter, 1m depth), with adjacent rows of deep and shallow holes staggered (see...). Figure 1 In this embodiment, the subsequent blasting holes on one side include two rows of deep holes and one row of shallow holes. The deep holes are 600-900mm away from the structural surface, and the hole spacing of each row of deep holes is 600mm. The row of shallow holes is located in the middle of the two rows of deep holes to ensure that the blasting holes are evenly arranged and the hole position deviation does not exceed ±50mm.

[0031] 2. Hole grooving: Using a grooving tool, internal thread-like grooves are machined on the inner wall of both deep and shallow holes (see...). Figure 3 The groove width is 5-10mm, the depth is 5-10mm, and the pitch is 50-80mm. During the grooving process, ensure the grooving is continuous and uniform, avoiding broken or shallow grooves. After grooving, use high-pressure air to clean debris from the hole. Creating an internal thread groove within the hole changes the previously smooth hole wall, facilitating three-dimensional explosive crushing and improving the degree of fragmentation.

[0032] 3. Explosive loading and sealing: For deep holes, the explosive loading section is 1m long, and the sealing section is 1m long; for shallow holes, the explosive loading section is 0.5m long, and the sealing section is 0.5m long. The explosive loading density is consistent with the borehole density on the structural surface. The borehole is sealed with stemming clay and water-based stemming clay to ensure compaction and prevent leakage of blasting energy.

[0033] 4. Delayed Detonation: Based on the pre-determined delayed detonation time, millisecond-delay detonators are used to detonate subsequent blasting holes. The detonation sequence is deep holes first, then shallow holes. After the deep holes are detonated, the shallow holes are detonated after a 25ms interval, ensuring that the deep holes first produce large-scale fracturing, and the shallow holes further break up large pieces of rock. Vibration signals are continuously monitored during the detonation process to ensure blasting safety.

[0034] 5. Blasting effect inspection: After blasting, wait for the smoke to dissipate (30-40 minutes), and construction personnel wearing protective masks enter the work area to check the shape of the crushing trough and the cracks formed around the trough. Record the proportion of large rocks (>500mm), which should not exceed 20% of the trough space.

[0035] Phase 3: Lateral rotary cutting and rock breaking by roadheader (tunneling phase) 1. Equipment debugging: Start the roadheader, adjust the cutting head speed, let it idle to the maximum speed (≥30r / min), check the operation of the cutting teeth to ensure there is no jamming or abnormal noise, adjust the advance speed to 0.5-1m / min, and prepare for tunneling.

[0036] 2. Cutting teeth insertion: After all the blast holes are blasted, a fractured cavity is formed in the roadway cross section; the cutting head of the roadheader is slowly pushed into the fractured cavity formed by the blasting, ensuring that the cutting teeth penetrate into the cavity to a depth of ≥500mm, avoiding direct contact between the cutting teeth and the unbroken rock mass, and preventing the cutting teeth from getting stuck.

[0037] 3. Lateral Rotary Cutting and Rock Breaking: After the cutting teeth reach their maximum speed, slowly move the roadheader so that the cutting teeth contact the inner wall of the trench from the side, rotary cutting and stripping away the broken rock mass. Fully utilize the blasting fractures around the trench to assist in the breaking and stripping of hard rock (see...). Figure 4 During the rotary cutting process, construction personnel observe the rock spalling in real time and adjust the advance speed and cutting tooth rotation speed to avoid problems such as excessive wear of the cutting teeth and rock blockage. Due to the crack network generated around the cavity by the pre-existing over-shear fracturing and delayed blasting, the rock is peeled off and broken along the crack direction during the rotary cutting process, and the range of the crushing cavity is gradually expanded until the design dimensions of the tunnel cross-section are reached.

[0038] 4. Cross-section trimming: Gradually expand the range of the crushing cavity until the design dimensions of the roadway cross-section are achieved (width and height deviation not exceeding ±50mm). Further trim the roadway outline, clean the rock blocks and debris in the cavity, and ensure that the roadway cross-section is flat and meets the design requirements.

[0039] Cyclic operation: After completing the excavation of a section of the tunnel (1.5-2m in length), repeat the above steps of "structural surface over-shear blasting - delayed blasting - mechanical lateral rotary shearing" to continuously advance the tunnel until the entire tunnel excavation task is completed. After each cycle of operation, conduct tunnel quality inspection and equipment maintenance to ensure the smooth progress of subsequent operations.

[0040] The core of this method is to utilize the mechanical properties of layered hard rock structures and achieve efficient rock-breaking tunneling through a synergistic mode of "two-stage blasting and mechanical lateral rotary shearing." The specific principle is as follows: 1. The first stage is structural plane overshear blasting: blast holes are arranged along the structural plane of layered hard rock. Overshear blasting is induced to induce structural plane fracture, which instantly releases the elastic potential energy accumulated inside the rock mass. At the same time, Mach cone high-frequency shock waves (causing shear failure) and Rayleigh waves (causing tensile failure) are generated on both sides of the structural plane, forming a through fracture surface. This provides a natural free boundary for subsequent blasting and reduces the propagation loss of blasting energy into the deeper rock mass.

[0041] 2. The second stage is delayed blasting: Based on the completion time of the super-shear fracture of the structural surface, the alternating deep and shallow blast holes on both sides of the structural surface are detonated with a delay. Utilizing the free boundaries formed in the early stage, the blasting stress wave generates a reflected tensile wave that breaks the rock. Combined with the guiding effect of the threaded groove inside the blast hole, the rock mass is three-dimensionally and uniformly fractured, forming a fracture cavity.

[0042] 3. The third stage is mechanical lateral rotary cutting: the fractured cavity formed by blasting changes the hard rock from a triaxial compression state to a uniaxial compression state, reducing the rock mass strength; the cutting teeth of the roadheader penetrate into the cavity, rotate at high speed to laterally cut and peel off the rock, and use the blasting cracks to achieve directional rock breaking, and finally expand the cavity to the tunnel design outline to complete the tunneling.

[0043] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A tunnel blasting method based on overshear fracturing of layered hard rock structural planes, characterized in that, It includes the following two stages: The first stage is structural plane super-shear blasting: blast holes are arranged along the slope of the structural plane and detonated simultaneously; during the structural plane blasting process, the explosive stress wave propagates along the structural plane, generating Mach cone high-frequency shock waves on both sides of the structural plane, and Rayleigh waves are generated on the surface of the structural plane at the same time; the Mach cones cause shear failure to the rock mass on both sides of the structural plane, and the Rayleigh waves cause tensile failure to the surface of the structural plane, which together cause cracks to form on the surface and both sides of the structural plane; The second stage involves delayed blasting on both sides of the structural surface. By identifying the start and end times of the high-frequency pulse signal of the Mach cone, the completion time of the super-shear fracture of the structural surface is determined, and the completion time is used as the delayed detonation time of the delayed blasting.

2. The tunnel blasting method based on overshear fracturing of layered hard rock structural planes according to claim 1, characterized in that, Vibration sensors are installed at the intersection of the structural surface and the roadway outline. The vibration sensors are connected to a data acquisition instrument to monitor the high-frequency pulse vibration signals generated by blasting in real time. The data acquisition instrument analyzes the vibration signals and identifies the start and end times of the Mach cone high-frequency pulse signals.

3. The tunnel blasting method based on overshear fracturing of layered hard rock structural planes according to claim 1, characterized in that, The arrangement of blast holes for delayed blasting is as follows: in the hard rock on both sides of the structural plane, the subsequent blasting blast holes are symmetrically arranged along the direction parallel to the structural plane. There are multiple rows of subsequent blasting blast holes on each side, arranged in an alternating manner of one row of deep holes and one row of shallow holes, and the adjacent rows of deep holes and shallow holes are staggered.

4. The tunnel blasting method based on overshear fracturing of layered hard rock structural planes according to claim 3, characterized in that, Internal thread grooves are machined on the inner walls of deep and shallow holes.

5. The tunnel blasting method based on overshear fracturing of layered hard rock structural planes according to claim 4, characterized in that, Based on the determined delayed detonation time, subsequent blasting holes are detonated, with the detonation sequence being deep holes first, followed by shallow holes.

6. The tunnel blasting method based on overshear fracturing of layered hard rock structural planes according to claim 5, characterized in that, After the deep hole is detonated, the shallow hole is detonated at 25ms interval. The deep hole first produces a large-scale fracture, and the shallow hole further breaks up large pieces of hard rock.

7. A tunnel excavation method based on overshear fracturing of layered hard rock structural planes, characterized in that, Following the tunnel blasting method according to any one of claims 1-6, a roadheader is used for lateral rotary cutting of rock, comprising the following steps: After the delayed blasting is completed, a fractured cavity is formed in the tunnel cross section. The cutting head of the roadheader is pushed into the fractured cavity formed by the blasting to perform lateral rotary cutting and rock breaking. The cutting teeth of the cutting head cut and peel off the fractured rock from the side, and the blasting fracture network is used to assist in the rock peeling.

8. The tunnel excavation method based on overshear fracturing of layered hard rock structural planes according to claim 7, characterized in that, After breaking through the rock, the cross-section is trimmed to ensure that the tunnel outline meets the design requirements.

9. The tunnel excavation method based on overshear fracturing of layered hard rock structural planes according to claim 7, characterized in that, After completing the excavation of a section of the tunnel, the steps of over-shear blasting, delayed blasting, and lateral rotary shearing are repeated to continue the tunnel excavation until the entire tunnel is completed.

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