Long-footage blasting construction method for soft rock tunnel

Abstract

A long-footage blasting construction method for a soft rock tunnel comprises the following steps that firstly, surrounding rock of a tunnel face is sampled, and the tensile strength of the surrounding rock is determined; 2, determining lithology of surrounding rock of the tunnel face; step 3, determining a charging structure; fourthly, charging is conducted according to selection in the third step; fifthly, the blast holes are blocked through stemming; and 6, blasting operation is conducted. Different charging structures are provided according to different lithology, and the method can adapt to tunnels with complex field surrounding rocks. And the peripheral holes adopt an energy-gathered interval charging structure, so that the energy utilization rate during explosive explosion can be improved to the greatest extent. By optimizing the charging structure of the peripheral holes and changing the energy distribution, the damage degree of the surrounding rock can be reduced, the back break condition can be well controlled, the flatness of the contour line is ensured, and the construction cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction blasting, in particular to a long-footage blasting construction method for a soft rock tunnel. Background Art

[0002] At present, in order to control over-excavation and reduce surrounding rock damage during the construction process of the drilling and blasting method, the method of "short footage, less charge" is usually adopted for soft rock tunnels. The damage to the surrounding rock is reduced by reducing the amount of charge. The charge amount of each hole is adjusted according to the hole depth of the short footage. Among them, the peripheral holes have the greatest impact on the damage of the surrounding rock, so the charge amount of the peripheral holes is the most critical. However, due to the short footage and the different surrounding rock characteristics and peripheral holes at different sites, if half an emulsion explosive or one-third of an emulsion explosive is used for charging, the time and cost of the construction process will be increased, and the energy utilization rate of the charge will be low. Moreover, in the actual application process on site, it is necessary to seal the peripheral holes with gun mud after charging. Usually, the length of the gun mud is fixed during the sealing. However, if the length of the gun hole sealing does not match the depth of the gun hole, it is easy to cause a large overflow of explosive energy during the explosion, affecting the blasting effect. Summary of the invention

[0003] In order to solve the technical problems that the existing charging structure in the above-mentioned background technology increases the time and cost of the construction process, has low charging energy utilization rate, and the length of the gun mud does not match the depth of the blasthole, the present invention provides a long-footage blasting construction method for a soft rock tunnel.

[0004] The technical solution of the present invention is as follows:

[0005] A long-footage blasting construction method for a soft rock tunnel comprises the following steps:

[0006] Step 1: Take samples of the surrounding rock at the tunnel face to determine the tensile strength of the surrounding rock;

[0007] Sampling of surrounding rock of the tunnel face where blasting is required, sampling of rock around the peripheral holes, ensuring that the sampled test blocks can represent the conditions of most surrounding rock of the tunnel face, and conducting tensile strength tests on the sampled test blocks to determine the tensile strength of the surrounding rock;

[0008] Step 2: Determine the lithology of the surrounding rock of the tunnel face;

[0009] Rock specimens are classified according to their tensile strength: rocks with a tensile strength of less than 5 MPa are defined as extremely soft rocks, rocks with a tensile strength between 5 MPa and 15 MPa are defined as soft rocks, and rocks with a tensile strength between 15 MPa and 30 MPa are defined as relatively soft rocks.

[0010] Step 3: Determine the charge structure;

[0011] Taking into account the footage and surrounding rock strength grade, the corresponding charging structure is selected according to different lithology classifications, which are specifically divided into the following situations:

[0012] A. If the rock test block is classified as extremely soft rock and the penetration is greater than 3.1m and less than 4m, a four-section shaped charge structure of "half-branch + half-branch + half-branch + half-branch" with equal spacing of 0.5m is adopted;

[0013] B. If the rock test block is classified as soft rock and the penetration is greater than 3.2m and less than 4.1m, a three-stage concentrated charge structure of "half branch + half branch + one branch" with equal spacing of 0.5m is adopted;

[0014] C. If the rock test block is classified as relatively soft rock and the penetration is greater than 3.4m and less than 4.3m, a two-stage concentrated charge structure of "one + one" with equal spacing of 0.5m is adopted;

[0015] Among them, one stick and half stick respectively represent one stick of emulsion explosive and half stick of emulsion explosive; and an energy-gathering device is provided between two adjacent explosives, and the energy-gathering device is provided on the side of the explosive away from the bottom of the blasthole;

[0016] Step 4: Charge according to the selection in step 3;

[0017] Step 5: Seal the blasthole with blasthole mud;

[0018] Step 6: Carry out blasting operations.

[0019] By increasing the footage, the construction progress was accelerated and the cost was saved. Different charging structures were provided according to different rock types, which could adapt to tunnels with complex surrounding rocks on site. In addition, the peripheral holes adopted the energy-gathering interval charging structure, which could maximize the energy utilization rate of the explosives during explosion. The particle size distribution of the blast pile after the explosion was reasonable, and the overall crushing degree was good, which provided great convenience for subsequent construction.

[0020] Specifically speaking, in order to avoid the situation where the energy dissipation is large due to insufficient length of the blasthole blockage, the length of the blasthole mud in step 5 along the length direction of the blasthole satisfies:

[0021]

[0022] Wherein, L is the depth of blasthole, L1 is the length of an emulsion explosive, L2 is the distance between the explosive and the energy-gathering device on the adjacent explosive, L3 is the length of the cannon mud, L4 is the distance between the last section of the explosive and the cannon mud, n is the number of emulsion explosives, m is the number of explosive spacings, and k is a constant, with a value range of 0.8 to 0.16.

[0023] Furthermore, step four is specifically as follows:

[0024] A. Fix the energy-gathering device to one end of one of the emulsion explosives, insert the electronic detonator into the other end of the emulsion explosive, point the detonator toward the depth of the blasthole, pound the explosive into the bottom of the hole through the blasting stick, and ensure that the foot line is led out of the detonator to the outside of the hole mouth;

[0025] B. Continue to fix the energy-gathering device on one end of the remaining explosives, and use the gun stick to push the end of the explosives without the energy-gathering device into the depth direction of the blasthole, and ensure that the distance between the energy-gathering devices on the explosives and the adjacent explosives is 0.5m. To ensure the accuracy of the distance, mark the 0.5m position on one end of the gun stick, and gradually extend the non-marked end of the gun stick into the blasthole. When the 0.5m position of the gun stick coincides with the position of the hole mouth, take out the gun stick to ensure the 0.5m distance.

[0026] The explosives are pounded into the blasthole using a blasting stick, which facilitates operation and speeds up construction progress. The 0.5m spacing can ensure better blasting effects.

[0027] Specifically, the energy-gathering device comprises a cylindrical body with one end capable of being transversely inserted into the explosive, a columnar energy-gathering tube connected to the non-insertion end thereof, and a trumpet-shaped energy-gathering cover recessed toward the main body is provided at the end of the energy-gathering tube away from the main body. The main body is inserted into the explosive, which facilitates the installation of the energy-gathering device, and the setting of the energy-gathering cover improves the energy utilization rate when the explosive explodes.

[0028] Preferably, an energy-gathering groove is provided inside the main body along its length direction, the cross section of the energy-gathering groove is V-shaped, and its opening side is connected to the inner wall of the main body. The energy-gathering groove can be inserted into the explosive with the main body to enhance the energy-gathering effect during blasting.

[0029] In order to further improve the energy-gathering effect of the energy-gathering groove and the power of the explosive, two energy-gathering grooves are symmetrically arranged along the axis of the main body, which can save explosives and reduce smoke and dust.

[0030] As a preferred embodiment, the side wall of the main body is provided with openings extending to both ends thereof along its length direction, so as to facilitate the insertion of the main body into the explosive along the length direction of the explosive, and the operation is fast and efficient.

[0031] Preferably, the cannon mud is made of natural clay material, which can improve the blasting effect of explosives, and the material is safe and easy to obtain, and the cannon mud can be made quickly and at low cost.

[0032] Through the above design, the beneficial effects of the long-footage blasting construction method for soft rock tunnels of the present invention are:

[0033] (1) By increasing the footage, the construction progress is accelerated, time costs are saved, and construction efficiency is improved.

[0034] (2) Different charging structures are provided according to different rock types, which can adapt to tunnels with complex surrounding rock on site.

[0035] (3) The peripheral holes adopt an energy-gathering interval charging structure, which can maximize the energy utilization rate of the explosive explosion. The particle size distribution of the explosion pile after explosion is reasonable and the overall crushing degree is good, which provides great convenience for subsequent construction.

[0036] (4) By optimizing the charging structure of the peripheral holes and changing the energy distribution, the degree of damage to the surrounding rock can be reduced, the over-excavation and under-excavation can be better controlled, the contour line can be ensured to be smooth, and the construction cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the attached picture:

[0038] Figure 1 is a flow chart of the present invention;

[0039] Figure 2 Schematic diagram of the energy gathering device in the embodiment;

[0040] Figure 3 Schematic diagram of the energy-gathering tube in the embodiment;

[0041] Figure 4 It is a schematic diagram of the main body in the embodiment;

[0042] Figure 5 A schematic cross-sectional view of the insertion of the energy-gathering device into the explosive;

[0043] Figure 6 It is a schematic diagram of the structure of two-stage shaped charge intervals;

[0044] Figure 7 It is a schematic diagram of the three-stage shaped charge spacer structure;

[0045] Figure 8 It is a schematic diagram of the structure of four-stage shaped charge intervals;

[0046] Fig. 9 Statistics of the post-blasting effects of the present invention in the field application;

[0047] The components represented by the reference numerals in the figure are:

[0048] 1. Energy-gathering device; 101. Energy-gathering cover; 102. Energy-gathering tube; 103. Energy-gathering trough; 104. Main body; 2. One emulsion explosive; 3. Half of one emulsion explosive; 4. Detonator; 5. Leg line; 6. Cannon mud. DETAILED DESCRIPTION

[0049] Example

[0050] See also Figure 1 This embodiment provides a long-footage blasting construction method for a soft rock tunnel, comprising the following steps:

[0051] Step 1: Take samples of the surrounding rock at the tunnel face to determine the tensile strength of the surrounding rock;

[0052] Sampling is carried out on the surrounding rock of the tunnel face where blasting construction is required. The rock around the peripheral holes is sampled, and the lithology is consistent with that of most of the rocks on the tunnel face. This ensures that the sampled test blocks can represent the conditions of most of the surrounding rock on the tunnel face. A tensile strength test is carried out on the sampled test blocks to determine the tensile strength of the surrounding rock.

[0053] Step 2: Determine the lithology of the surrounding rock of the tunnel face;

[0054] Rock specimens are classified according to their tensile strength: rocks with a tensile strength less than 5 MPa are defined as extremely soft rocks, rocks with a tensile strength between 5 MPa and 15 MPa are defined as soft rocks, and rocks with a tensile strength between 15 MPa and 30 MPa are defined as relatively soft rocks.

[0055] The tensile strength of the field test block in this embodiment is 8.63 MPa, which belongs to the soft rock range.

[0056] Step 3: Determine the charge structure;

[0057] Taking into account the footage and surrounding rock strength grade, the corresponding charging structure is selected according to different lithology classifications, which are specifically divided into the following situations:

[0058] A. See Figure 8 If the rock test block is classified as extremely soft rock and the penetration is greater than 3.1m and less than 4m, a four-section energy-gathering interval charging structure of "half-branch + half-branch + half-branch + half-branch" with equal spacing of 0.5m is adopted;

[0059] B. See Figure 7 If the rock test block is classified as soft rock and the penetration is greater than 3.2m and less than 4.1m, a three-stage concentrated charge structure of "half branch + half branch + one branch" with equal spacing of 0.5m is adopted;

[0060] C. See Figure 6 If the rock test block is classified as relatively soft rock and the penetration is greater than 3.4m and less than 4.3m, a two-stage concentrated charge structure of "one + one" with equal spacing of 0.5m is adopted;

[0061] Among them, one and half represent one emulsion explosive 2 and half emulsion explosive 3 respectively; and an energy gathering device 1 is provided between two adjacent explosives, and the energy gathering device 1 is provided on the side of the explosive away from the bottom of the blast hole.

[0062] In this embodiment, the peripheral hole depth is designed to be 4.3m, and the slot hole depth is 4.5m, ensuring the footage is about 4.0m. Combining the above three situations A, B, and C, as well as the judgment of the surrounding rock lithology in step 2, a three-section energy-gathering interval charging structure is selected.

[0063] Step 4: Charge according to the surrounding rock properties of the tunnel face on site and the selection in step 3;

[0064] Furthermore, step four is specifically as follows:

[0065] A. Fix the energy-gathering device 1 to one end of one of the emulsion explosives, insert the electronic detonator 4 into the other end of the emulsion explosive, point the detonator 4 toward the depth of the blasthole, pound the explosive into the bottom of the hole through the blasting stick, and ensure that the leg wire 5 is led out of the detonator 4 to the outside of the hole mouth;

[0066] B. Continue to fix the energy-gathering device 1 on one end of the remaining explosive, and use the gun stick to push the end of the explosive without the energy-gathering device 1 into the depth direction of the blasthole, and ensure that the distance between the energy-gathering device 1 on the adjacent explosive is 0.5m. To ensure the accuracy of the distance, mark the 0.5m position on one end of the gun stick, and gradually extend the non-marked end of the gun stick into the blasthole. When the 0.5m position of the gun stick coincides with the position of the hole mouth, take out the gun stick to ensure the 0.5m distance.

[0067] The explosives are pounded into the blasthole using a blasting stick, which facilitates operation and speeds up construction progress. The 0.5m spacing can ensure better blasting effects.

[0068] See also Figure 2 , Figure 3 , Figure 5 Specifically, the energy gathering device 1 comprises a cylindrical body 104 with one end capable of being transversely inserted into the explosive, a columnar energy gathering tube 102 connected to the non-insertion end thereof, and a trumpet-shaped energy gathering cover 101 recessed toward the main body 104 is provided at one end of the energy gathering tube 102 away from the main body 104. The main body 104 is inserted into the explosive, which facilitates the installation of the energy gathering device 1, and the provision of the energy gathering cover 101 improves the energy utilization rate when the explosive explodes.

[0069] Exemplarily, the one stick of emulsion explosive 2 or the half stick of emulsion explosive 3 are both packaged in plastic film, and the main body 104 can be inserted into the plastic film package of the explosive by pressing.

[0070] See also Figure 4 Preferably, an energy-gathering groove 103 is provided inside the main body 104 along its length direction, and the cross section of the energy-gathering groove 103 is V-shaped, and its opening side is connected to the inner wall of the main body 104. The energy-gathering groove 103 can be inserted into the explosive along with the main body 104 to enhance the energy-gathering effect during blasting.

[0071] In order to further improve the energy gathering effect of the energy gathering groove 103 and the power of the explosive, two energy gathering grooves 103 are symmetrically provided along the axis of the main body 104, which can save explosives and reduce smoke.

[0072] As a preferred embodiment, the side wall of the main body 104 is provided with openings extending to both ends thereof along its length direction, so as to facilitate the insertion of the main body 104 into the explosive along the length direction of the explosive, and the operation is fast and efficient.

[0073] Step 5: After the charging is completed, the blasthole is sealed with blasthole mud 6 based on the blasthole depth and surrounding rock strength grade.

[0074] Specifically speaking, in order to avoid the situation where the energy dissipation is large due to the insufficient length of the blasthole blockage, the length of the blasthole mud 6 in step 5 along the length direction of the blasthole satisfies:

[0075]

[0076] Wherein, L is the depth of the blasthole, L1 is the length of an emulsion explosive 2, L2 is the distance between the explosive and the energy-gathering device on the adjacent explosive, L3 is the length of the taphole mud 6, L4 is the distance between the last section of the explosive and the taphole mud 6, n is the number of emulsion explosives 2, m is the number of explosive spacings, and k is a constant, and the value range of k is 0.8 to 0.16.

[0077] In specific implementation, the value range of k depends on the stability of the surrounding rock. If the surrounding rock is less stable, k is 0.8 to 0.13. If the surrounding rock is more stable, k is 0.13 to 0.16.

[0078] Further preferably, the cannon mud 6 is made of natural clay material and is produced according to the diameter of the blasthole to ensure that it can fit the blasthole and improve the blasting effect of the explosives. In addition, the material is safe and easy to obtain, and the cannon mud 6 is produced quickly and at low cost.

[0079] Step 6: Carry out blasting operations.

[0080] See also Fig. 9 According to the statistics of the post-blasting effect of the three-stage energy-gathering interval charging structure applied on site, when the penetration is about 4m, the peripheral holes adopt a three-stage energy-gathering interval charging structure of "one branch + half branch + half branch" with equal charging spacing of 0.5m. After the blast, the half-hole rate is above 75%, the half-hole length is above 70%, the damage to the surrounding rock is small, and the overall post-blasting effect is good.

[0081] The long-footage blasting construction method for soft rock tunnels of the present invention speeds up the construction progress by increasing the footage, saves time cost, and improves construction efficiency. Different charging structures are provided according to different rock properties, which can adapt to tunnels with complex surrounding rocks on site. The peripheral holes adopt an energy-gathering interval charging structure, which can maximize the energy utilization rate of the explosives during explosion. The particle size distribution of the blast pile after the explosion is reasonable, and the overall crushing degree is good, which provides great convenience for subsequent construction. By optimizing the charging structure of the peripheral holes and changing the distribution of its energy, the degree of damage to the surrounding rock can be reduced, the over-excavation and under-excavation can be better controlled, the flatness of the contour line can be ensured, and the construction cost can be reduced.

Claims

1. A long-footage blasting construction method for a soft rock tunnel, characterized in that: The following steps are involved: Step 1: Take samples of the surrounding rock at the tunnel face to determine the tensile strength of the surrounding rock; Sampling of surrounding rock of the tunnel face where blasting is required, sampling of rock around the peripheral holes, ensuring that the sampled test blocks can represent the conditions of most surrounding rock of the tunnel face, and conducting tensile strength tests on the sampled test blocks to determine the tensile strength of the surrounding rock; Step 2: Determine the lithology of the surrounding rock of the tunnel face; Rock specimens are classified according to their tensile strength: rocks with a tensile strength of less than 5 MPa are defined as extremely soft rocks, rocks with a tensile strength between 5 MPa and 15 MPa are defined as soft rocks, and rocks with a tensile strength between 15 MPa and 30 MPa are defined as relatively soft rocks. Step 3: Determine the charge structure; Taking into account the footage and surrounding rock strength grade, the corresponding charging structure is selected according to different lithology classifications, which are specifically divided into the following situations: A. If the rock test block is classified as extremely soft rock and the penetration is greater than 3.1m and less than 4m, a four-section shaped charge structure of "half-branch + half-branch + half-branch + half-branch" with equal spacing of 0.5m is adopted; B. If the rock test block is classified as soft rock and the penetration is greater than 3.2m and less than 4.1m, a three-stage concentrated charge structure of "half branch + half branch + one branch" with equal spacing of 0.5m is adopted; C. If the rock test block is classified as relatively soft rock and the penetration is greater than 3.4m and less than 4.3m, a "one + one" two-stage energy-gathering interval charge structure with equal spacing of 0.5m is adopted; Among them, one stick and half stick respectively represent one stick of emulsion explosive (2) and half stick of emulsion explosive (3); and an energy focusing device (1) is provided between two adjacent explosives, and the energy focusing device (1) is provided on the side of the explosive away from the bottom of the blast hole; Step 4: Charge according to the selection in step 3; Step 5: Seal the blasthole with blasthole mud (6); Step 6: Carry out blasting operations.

2. A long-footage blasting construction method for soft rock tunnels according to claim 1, characterized in that: The length of the taphole mud (6) in step 5 along the length direction of the taphole satisfies: Wherein, L is the depth of the blasthole, L1 is the length of an emulsion explosive (2), L2 is the distance between the explosive and the energy-gathering device (1) on the adjacent explosive, L3 is the length of the taphole mud, L4 is the distance between the last section of the explosive and the taphole mud (6), n is the number of emulsion explosives (2), m is the number of distances between the explosives, and k is a constant that depends on the stability of the surrounding rock. When the surrounding rock stability is poor, k is 0.8 to 0.13, and when the surrounding rock stability is good, k is 0.13 to 0.

16.

3. A long-footage blasting construction method for soft rock tunnels according to claim 1, characterized in that: Step 4 is as follows: A. Fix the energy-gathering device (1) to one end of one of the emulsion explosives, insert the electronic detonator (4) into the other end of the emulsion explosive, point the detonator (4) toward the depth of the blasthole, pound the explosive into the bottom of the hole through the blasting stick, and ensure that the foot line (5) is led out of the detonator (4) to the outside of the hole mouth; B. Continue to fix the energy-gathering device (1) on one end of the remaining explosive, and use a blasting stick to push the end of the explosive without the energy-gathering device (1) into the depth direction of the blasthole, and ensure that the distance between the energy-gathering device on the adjacent explosive is 0.5m.

4. A long-footage blasting construction method for soft rock tunnels according to claim 1, characterized in that: The energy focusing device (1) comprises a cylindrical main body (104) with one end capable of being transversely inserted into explosives, a columnar energy focusing tube (102) being connected to the non-insertion end thereof, and a trumpet-shaped energy focusing cover (101) recessed toward the main body (104) being provided at the end of the energy focusing tube (102) away from the main body (104).

5. A long-footage blasting construction method for soft rock tunnels according to claim 4, characterized in that: An energy-gathering groove (103) is provided inside the main body (104) along its length direction. The cross section of the energy-gathering groove (103) is V-shaped, and its opening side is connected to the inner wall of the main body (104).

6. A long-footage blasting construction method for soft rock tunnels according to claim 5, characterized in that: Two energy-gathering grooves (103) are symmetrically arranged along the axis of the main body (104).

7. A long-footage blasting construction method for soft rock tunnels according to claim 5, characterized in that: The side wall of the main body (104) is provided with openings extending through both ends thereof along its length direction.

8. The long-footage blasting construction method for soft rock tunnels according to claim 1 is characterized in that: The taphole mud (6) is made of natural clay material.

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