A device for blasting loose and soft surrounding rock and a tunnel construction method for loose and soft surrounding rock

Abstract

The application provides a device for loose soft surrounding rock blasting, which comprises a cylinder for loading explosive and detonator, wherein one end of the cylinder inserted into the bottom of a blast hole is provided with a front end cover, the end away from the cylinder is conical, and the other end of the cylinder is provided with a rear end cover. The device can push the explosive into the bottom of the blast hole without scanning the hole after the blast hole is drilled, and the explosive energy can be gathered at the bottom of the blast hole after the front end cover is quickly removed after blasting, so that the utilization rate of the blast hole reaches 87.5%, which is 1.8-2.7 times of the original, and the blasting effect is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of tunnel construction blasting technology, in particular to a loose soft surrounding rock blasting device and a loose soft surrounding rock tunnel construction method. BACKGROUND

[0002] The soft surrounding rock generally refers to the surrounding rock with weak rock mass, low bearing capacity, developed joint fissure and broken structure, wherein the loose soft surrounding rock refers to the rock mass with sand and gravel structure, broken and loose, poor cohesion and often containing seepage or gushing water. In the process of excavation by blasting method, when a blast hole is completed, the sand always falls down during the process of cleaning the blast hole by using a hole cleaner due to the characteristics of the loose soft surrounding rock, and the blast hole becomes larger and larger. Because of the sand in the blast hole, the explosive cannot be loaded to the bottom of the hole. There is water in the blast hole, and when the water is large, the explosive is automatically pushed out. The larger the hole diameter, the more difficult to seal the hole with stemming, and the more likely to pull out the blast hole during blasting, resulting in small blasting footage, low utilization rate of blast hole and slow construction progress. After full-face blasting, collapse is easily caused due to the delay of initial support, which not only has great safety hidden danger, but also increases the cost and affects the construction progress. SUMMARY

[0003] The present application provides a loose soft surrounding rock blasting device, which comprises a cylinder for loading explosive and detonator, one end of the cylinder inserted into the bottom of the blast hole is provided with a front end cover, and the end away from the cylinder is conical; the other end of the cylinder is provided with a rear end cover.

[0004] On the basis of the above-mentioned scheme, the front end cover comprises a cylindrical connecting part for connecting with the cylinder and a conical sharp head part.

[0005] On the basis of the above-mentioned scheme, the rear end cover is threadedly connected with the cylinder.

[0006] On the basis of the above-mentioned scheme, after the explosive and detonator are loaded in the cylinder, stemming is inserted between the explosive and the rear end cover.

[0007] The present application also provides a loose soft surrounding rock tunnel construction method using the above-mentioned device, which comprises the following steps:

[0008] S1 arch reinforcement

[0009] Before blasting construction of the blast hole, a small pipe filled with cement slurry in advance is punched into the arch to pre-reinforce the arch surrounding rock;

[0010] S2 construction by using upper and lower two-step blasting excavation

[0011] S21 the tunnel excavation section is divided into upper and lower two parts, the height of the upper part is one half to two thirds of the height of the tunnel excavation section; the upper part is first blasted and constructed;

[0012] S22 drilling the borehole at the upper part of the tunnel excavation section, and after drilling each borehole, a pre-prepared blasting device is loaded into the borehole to the bottom of the borehole; the blasting device is the device described above;

[0013] After all the blasting devices are installed, the blasting is connected;

[0014] S23 after the upper part of the tunnel excavation section is blasted, the spoil is not immediately removed, and the primary support is quickly performed;

[0015] S24 after step S23 is completed, the spoil is quickly removed and transported;

[0016] S25 after the spoil removal and transportation are completed, the primary support is performed;

[0017] S26 the lower part of the tunnel excavation section is excavated using the loosening blasting, the inverted arch is excavated using the excavator, and after the excavation is completed, the primary support is performed;

[0018] S3 secondary lining

[0019] After step S26 is completed, the secondary lining is performed.

[0020] Using the device of the present application, after the borehole drilling is completed, the eye is not needed to be swept, even if there is some sand in the borehole, the explosive can be pushed into the bottom of the borehole; at the same time, the front end cover can be quickly removed after blasting, so that the explosive energy can be concentrated at the bottom of the hole, the utilization rate of the borehole reaches 87.5%, which is 1.8-2.7 times of the original, and the blasting effect is improved; since the cylinder wall is relatively thin, the broken pipe wall does not affect the rock blasting footage, and the footage per shot reaches 2.8m, which is 2.0-3.1 times of the original. The rear end cover effectively prolongs the expansion time of the explosive gas, and plays a blocking role together with the stemming, which better breaks the rock and reduces the remaining length of the borehole. Using the blasting device of the present application, the stemming is blocked, the charging process time is shortened, and the construction speed is accelerated. The device and method of the present application are also suitable for controlled blasting of various rocks which are not yet formed but are under compression, and rocks which are formed but are strongly weathered or fully weathered, and the construction progress is fast and the safety performance is high. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a schematic diagram of the borehole arrangement in the excavation section of the blasting structure of the present application;

[0022] Figure 2 It is a schematic diagram of the piston type charging structure of the present application;

[0023] Figure 3 It is a schematic diagram of the structure of the bottom cover and the fixed shaft in the piston type charging structure of the present application;

[0024] Figure 4 It is a schematic diagram of the use state of the piston type charging structure of the present application. DETAILED DESCRIPTION

[0025] The application will be further described in conjunction with the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate the understanding of the application and do not limit the application in any way.

[0026] Example 1

[0027] As shown in the drawings, the present embodiment provides a device for loose soft rock blasting, which comprises a barrel 6-1 for loading explosives and detonators. The barrel 6-1 is inserted into the bottom of the blast hole, and one end of the barrel 6-1 is provided with a front end cap 6-2. The front end cap 6-2 is conical at the end away from the barrel 6-1. The other end of the barrel 6-1 is provided with a rear end cap 6-3. This design of the front end cap 6-2 eliminates the need to clean the hole even if there is sand in the hole during use. The sand can be pinned outside the conical tip. Figure 1 As shown in the drawings, as a specific embodiment, the front end cap 6-2 comprises a cylindrical connecting part 6-21 for connecting with the barrel 6-1 and a conical tip part 6-22. When the connecting part 6-21 is connected with the barrel 6-1, the connecting part 6-21 can be inserted into the barrel 6-1 or the barrel 6-1 can be inserted into the connecting part 6-21. Figure 2 The rear end cap 6-3 is connected with the barrel 1, which can seal the barrel 1 to prolong the expansion time of the blast gas. As a specific embodiment, the rear end cap 6-3 is threadedly connected with the barrel 6-1. In order to enhance the sealing effect, after the barrel 6-1 is loaded with explosives and detonators, a stemming is inserted between the explosives and the rear end cap 6-3.

[0028] As a specific use scheme, the barrel 6-1 uses a steel pipe with an inner diameter of 50mm, a wall thickness of 1-3mm, and the material of the front end cap 6-2 can be the same as that of the barrel 6-1, with a thickness of 1-3mm. The explosives use explosive rolls with a diameter of 50mm.

[0029]

[0030] ​​​In response to the problems existing in blasting loose and weak surrounding rock, the device provided in this embodiment effectively solves the following problems. First, the conical tip of the front cover 6-2 of the blasting device of this application can be set so that the hole does not need to be swept after the blast hole is dug. Even if there is some sand in the blast hole, the explosive can be pushed and loaded into the bottom of the hole. Secondly, the front cover 6-2 is a sleeve cover that can be quickly removed after blasting, allowing the explosive energy to concentrate at the bottom of the borehole, increasing the borehole utilization rate to 87.5%, which is 1.8 to 2.7 times that of the original, thus improving the blasting effect. Thirdly, the tube wall of the cylinder 6-1 is relatively thin, only 1 to 3 mm. Blastling the tube wall does not affect the rock blasting advance, with each blast reaching 2.8 m, which is 2.0 to 3.1 times that of the original. Fourthly, the rear cover 6-3 is connected to the cylinder 6-1 by screws. After tightening the cover, it effectively prolongs the expansion time of the explosive gas, and together with the stemming material inside and outside the cylinder 6-1, it plays a blocking role, better breaking the rock and reducing the remaining borehole length. Fifthly, even if there is water in the borehole, the blasting device is sealed, which has a good waterproof effect on the explosive inside. The presence of water will not push the explosive outward, ensuring the blasting effect.

[0031] Example 2

[0032] like Figure 3 As shown, this embodiment provides a construction method for tunnels in loose, weak surrounding rock. To ensure construction safety and prevent collapse accidents, the excavation method for this type of surrounding rock is changed from full-face blasting to separate upper and lower bench blasting excavation; including the following steps:

[0033] A construction method for tunnels in loose, weak surrounding rock, characterized by the following steps:

[0034] S1 Arch Reinforcement

[0035] Before blasting the boreholes, small guide pipes with a diameter of Φ42mm and a length of 6.0m are driven into the tunnel arch and filled with cement mortar or cement gravel (particle size less than 5mm) in advance, with a spacing of 450mm, to pre-reinforce the surrounding rock of the arch.

[0036] S2 is constructed using a two-stage blasting excavation method, with the upper stage excavating to a maximum depth of no more than 20m along the tunnel's extension direction, and the lower stage excavating to a maximum depth of no more than 30m along the tunnel's extension direction.

[0037] S21 divides the tunnel excavation section into two parts (the upper part is the upper step and the lower part is the lower step). The height of the upper part is one-half to two-thirds of the height of the tunnel excavation section. The upper part is blasted first.

[0038] S22 Drills blast holes in the upper part of the tunnel excavation section. For each blast hole drilled, a blasting device prefabricated in Example 1 is installed into the blast hole up to the bottom of the hole.

[0039] Specifically, as shown in Figure 3 , the blast hole comprises a cut hole 1, an expansion hole 2, an auxiliary hole 3, a peripheral hole 4 and a bottom hole 5; the cut hole 1 is arranged in two rows along the vertical direction on both sides of the tunnel center line; two rows of expansion holes 2 are arranged on the side of the cut hole 1 away from the tunnel center line; three circles of auxiliary holes 3 and peripheral holes 4 are sequentially arranged on the periphery of the expansion hole 3; and the bottom hole 5 is arranged at the connection of the upper and lower parts of the tunnel excavation section.

[0040] As shown in Figure 4 , the included angle between the cut hole 1 and the expansion hole 2 and the plane passing through the tunnel center line and perpendicular to the horizontal plane is 7°.

[0041] The depth of the cut hole 1, the expansion hole 2 and the bottom hole 5 is 3.4m, and the depth of other blast holes is 3.2m.

[0042] After the blasting device is loaded into the peripheral hole 4, only the entrance of the blast hole is blocked with stemming for 0.3m, and the other blast holes are filled with stemming.

[0043] After the installation of all blasting devices is completed, the blasting is connected; the blasting sequence is the cut hole 1, the expansion hole 2, the auxiliary hole 3, the peripheral hole 4 and the bottom hole 5.

[0044] S23 After the upper part of the tunnel excavation section is blasted, the muck is not immediately discharged, the working face is quickly excavated and leveled using an excavator, three arcs of 18mm diameter threaded steel bars are bent, the close-meshed net is tightly attached to the rock surface, and C25 grade concrete with a thickness of 50-100mm is quickly sprayed using a wet spraying machine to prevent the exposed rock layer from weathering and falling off;

[0045] S24 After step S23 is completed, the muck is quickly discharged and transported;

[0046] S25 After the muck discharge and transportation are completed, the primary support is carried out; as a specific embodiment, the upper step is supported by a standard I16 arch, the spacing is 0.8m per frame, and the arch wall is hung by a steel mesh, the lock foot is punched, and the arch is firmly welded with U-shaped steel bars, and C25 concrete with a thickness of 150mm is quickly sprayed. The next cycle punches hollow anchor rods in the arch, and mortar anchor rods in the side wall, with a spacing of 1.5m x 1.5m;

[0047] S26 The lower part of the tunnel excavation section is excavated using loose blasting, and after the muck is discharged, the long arch is connected, the lock foot anchor pipe is punched, the arch is firmly welded with U-shaped steel bars, and the concrete primary support is sprayed; the inverted arch is excavated using an excavator, the muck is discharged and cleaned, the inverted arch is erected, the lock foot anchor pipe is punched, the arch is firmly welded, the concrete primary support is sprayed, and then the concrete is backfilled according to the design requirements.

[0048] S3 secondary lining

[0049] Second lining, according to the design drawings, hang the drainage blind pipe, geotextile and waterproof board, bind the reinforcement, erect the formwork and correct it, and pour the concrete. The distance between the second lining and the working face is not more than 50 m, and the primary support is ensured not to invade the limit.

[0050] In the method of the embodiment, the position, number, depth, inclination angle of the blast hole and various parameters of the blasting can refer to Figure 3 and 4 and Table 1, which will not be described in detail one by one here.

[0051] Use case

[0052] During the construction of the Motianling tunnel, the 110 m range of the working face from the No. 2 inclined shaft is full-weathered or partially strong-weathered granite, the surrounding rock grade is V grade, most of which is gravel structure, and a very small number of which has massive structure, which becomes gravel after being knocked with a hammer, the color is grayish yellow, and the structure and structure have been completely destroyed. The rock stratum of the working face is sandy. There are many streamline water outlets on the working face, and the coarse-grained sand is in a saturated water state. When mechanical excavation is used, it cannot be dug in, and the excavator can only dig out a few tooth grooves, and the excavation efficiency is very poor, which cannot meet the progress requirement. When the full-face blasting scheme of the prior art is used for excavation, two layers of scaffolds are used, 10 YT-30 type wind drills (8 in use and 2 in standby), two kinds of diameter Φ28 mm hollow hexagonal steel drill pipes with lengths of 3.0 m and 3.5 m, diameter Φ42 mm cross-shaped drill bits, a 3.0 m deep undercutting eye, and other eyes with a depth of 2.8 m are used. After the undercutting eye, the auxiliary eye and the peripheral eye are all drilled, the eye is swept with an eye sweeper, and then the explosive is loaded and the line is placed. During the sweeping of the blast hole with the eye sweeper, sand always falls down, and the outside of the blast hole becomes larger and larger. Because there is always sand in the blast hole, the explosive cannot be loaded to the bottom of the hole. There is water in the blast hole, and when the water is large, the explosive is automatically pushed out. The larger the hole diameter, the more difficult it is to seal the hole with the stemming, and the easier it is to "pull the cylinder" during blasting. The blasting footage is 0.9-1.4 m, the blast hole utilization rate is 32.1%-50%, and the progress is slow. After full-face blasting, the initial support cannot be timely, which easily causes collapse, not only has great safety hidden dangers, but also increases the cost and affects the construction progress.

[0053] The method in Embodiment 2 of the present application is used for construction, and the specific steps are as follows:

[0054] S1 arch reinforcement

[0055] Before the blast hole is constructed, a small guide pipe with a diameter of Φ42 mm and a length of 6.0 m and filled with slurry in advance is punched into the tunnel arch, and the interval is 450 mm, so as to pre-reinforce the arch surrounding rock;

[0056] S2 construction by using the upper and lower bench blasting excavation method

[0057] The excavation section width x height of the single-line tunnel of the grade II railway is 8380 mm x 10151 mm, and the total excavation area is 71 m 2 The excavation section width x height of the single-line tunnel of the grade II railway is 8380 mm x 10151 mm, and the total excavation area is 71 m 2 .

[0058] S21 divides the tunnel excavation section into two parts, and first performs blasting construction on the upper part;

[0059] According to the blast hole layout diagram and parameter table Figure 3 、 Figure 4 and Table 1, 6 undercut holes, 8 expansion holes, and 12 bottom holes are drilled, with a hole depth of 3.4 m; 37 auxiliary holes and 34 peripheral holes are drilled, with a hole depth of 3.2 m. The total number of blast holes in the full section is 97.

[0060] S22 drills the blast holes in the upper part of the tunnel excavation section, and for each blast hole drilled, the blast device prepared in advance in Example 1 is loaded into the hole bottom;

[0061] According to the blast parameter design table 1, the blast device is preloaded (the detonator foot wire must be effectively twisted together), and the blast holes on the working face are checked, and for each blast hole drilled, the blast device is loaded into the hole bottom in time, and the remaining blast holes are filled with mortar except that the peripheral holes are only loaded with water mortar to seal the holes for 0.3 m. The total amount of explosive is 120 Kg, and the unit explosive consumption is 1.14 Kg / m 3 .

[0062] After the holes are drilled, the explosive and mortar are loaded, and the wiring is completed, all equipment and personnel are withdrawn to the safety warning line, and the blast foreman checks to ensure safety, and then the blast command is issued to the blaster. After the blast, ventilation is performed for 30 minutes, and the blast foreman and the blaster check the blasting situation, and after confirming safety, the personnel of the next process are notified to enter the construction.

[0063] After all the blast devices are installed, the blasting is performed;

[0064] Table 1 Soft weak surrounding rock bench blasting parameter design

[0065]

[0066] Table 2 Soft weak surrounding rock parameters and expected blasting effect

[0067]

[0068] S23 After blasting the upper part of the tunnel excavation section, the spoil is not immediately removed. A excavator is used to quickly excavate and level the working face. Three 18mm diameter steel bars are bent into an arc shape and the mesh is tightly attached to the rock surface. A wet spraying machine is used to quickly spray C25 grade concrete with a thickness of 50-100mm to prevent weathering and spalling of exposed rock layers;

[0069] S24 After step S23 is completed, the spoil is quickly removed and transported;

[0070] S25 The upper step is set to a standard I16 arch frame with a spacing of 0.8m per frame. The arch wall is hung with a standard steel mesh, and the lock foot is welded firmly with U-shaped steel to the arch frame. C25 concrete is quickly wet sprayed to a thickness of 150mm. In the next cycle, hollow anchor rods are drilled in the arch and masonry anchor rods are drilled in the side wall with a spacing of 1.5m x 1.5m;

[0071] S26 The lower part of the tunnel excavation section is excavated using loose blasting, and the step length is not more than 20m. The ring is quickly formed to prevent the arch from sinking more than 150mm.

[0072] S3 Secondary lining

[0073] The secondary lining is closely followed, and drainage pipes, geotextiles, and waterproof boards are hung according to the design drawings. The steel reinforcement is tied and the formwork is corrected and poured with concrete. The secondary lining distance from the working face is not more than 50m to ensure that the primary support does not exceed the limit.

[0074] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to make equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present application. Any modification, equivalent change and modification of the above embodiments based on the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A construction method of a loose soft rock tunnel, characterized in that, It comprises the following steps: S1 arch reinforcement: Before blasting the construction blast hole, a small pipe filled with cement slurry in advance is first driven into the tunnel arch to pre-reinforce the surrounding rock of the arch; S2 construction is performed in the way of upper and lower bench blasting: S21 the tunnel excavation section is divided into upper and lower parts, the height of the upper part is one half to two thirds of the height of the tunnel excavation section; the upper part is first subjected to blasting construction; S22 drilling of blast holes is performed on the upper part of the tunnel excavation section, and a pre-prepared blasting device is loaded into each blast hole to the bottom of the hole as each blast hole is drilled; the blasting device is a device for blasting soft and weak surrounding rock, and comprises a barrel (6-1) for loading explosives and detonators, one end of the barrel (6-1) inserted into the bottom of the blast hole is provided with a front end cover (6-2), the end portion of the front end cover (6-2) away from the barrel (6-1) is conical; the other end of the barrel (6-1) is provided with a rear end cover (6-3); After all the blasting devices are installed, the blasting is performed in sequence; S23 after the upper part of the tunnel excavation section is blasted, the muck is not immediately removed, and the primary support is quickly performed; S24 after step S23 is completed, the muck is quickly removed and transported; S25 after the muck removal and transportation are completed, the primary support is performed; S26 the lower part of the tunnel excavation section is excavated using loose blasting, the inverted arch is excavated using an excavator, and the primary support is performed after the excavation is completed; S3 secondary lining.

2. The construction method of a loose soft rock tunnel according to claim 1, characterized in that, The front end cover (6-2) comprises a cylindrical connecting portion (6-21) for connecting with the barrel (6-1) and a conical sharp head portion (6-22).

3. The construction method of a loose soft rock tunnel according to claim 1, characterized in that, The rear end cover (6-3) is threadedly connected with the barrel (6-1).

4. The construction method of a loose soft rock tunnel according to claim 2, characterized in that, After the barrel (6-1) is loaded with explosives and detonators, stemming is inserted between the explosives and the rear end cover (6-3).

5. The construction method of a loose soft rock tunnel according to claim 1, characterized in that, The blast holes in step S22 comprise a slotting eye (1), an expanding slot eye (2), an auxiliary eye (3), a peripheral eye (4) and a bottom eye (5); the slotting eyes (1) are arranged in two columns along the vertical direction on both sides of the tunnel center line; two columns of expanding slot eyes (2) are arranged on the side of the slotting eyes (1) away from the tunnel center line; the auxiliary eyes (3) and the peripheral eyes (4) are sequentially arranged on the periphery of the expanding slot eyes (2); the bottom eyes (5) are arranged at the connection between the upper and lower parts of the tunnel excavation section.

6. The construction method of a loose soft rock tunnel according to claim 5, characterized in that, The included angle between the slotting eyes (1) and the expanding slot eyes (2) and the plane passing through the tunnel center line and being perpendicular to the horizontal plane is 7°.

7. The method of claim 5, wherein the weak surrounding rock is loose and soft. The depth of the slotting eyes (1), the expanding slot eyes (2) and the bottom eyes (5) is 3.4 m, and the depth of the other blast holes is 3.2 m.

8. The method of claim 5, wherein the weak surrounding rock tunnel is a loose rock tunnel. After the blasting device is loaded into the peripheral eyes (4), only the entrance of the blast hole is blocked with stemming for 0.3 m, and the other blast holes are completely filled with stemming.

9. The method of claim 5, wherein the weak surrounding rock tunnel is a loose rock tunnel. The blasting sequence of step S22 is the slotting eyes (1), the expanding slot eyes (2), the auxiliary eyes (3), the peripheral eyes (4) and the bottom eyes (5).

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