A subway connecting passage carbon dioxide fracturing device excavation method

Abstract

The application discloses a kind of carbon dioxide fracturing device excavation methods of subway connecting passage, comprising the following steps: step 1: hole is arranged on working face, including the 4 carbon dioxide fracturing holes of diamond arrangement being arranged in the center of working face, center hole being arranged in the center of the diamond and the peripheral hole around the carbon dioxide fracturing hole, the center hole and peripheral hole are used as buffer empty hole;Step 2: carbon dioxide fracturing device is arranged in carbon dioxide fracturing hole;Step 3: all carbon dioxide fracturing devices are simultaneously detonated;Pick up fracturing device;Step 4: secondary crushing is carried out manually using air pick;The application process is spark-free, easy to operate, and although only the loosening and protrusion of frozen soil can be seen on the working face after blasting, a large number of cracks are generated in the frozen rock-soil layer, and the air pick is easier to operate when manually breaking, compared with pure manual air pick excavation, the application can improve the excavation efficiency and reduce the excavation period.

Description

Technical Field

[0001] This invention relates to the field of construction technology for subway connecting passages using freezing methods. Specifically, it relates to a method for excavating subway connecting passages using carbon dioxide fracturing equipment. Background Technology

[0002] Artificial ground freezing has been widely used in subway connection projects. This method uses the frozen walls formed to reinforce the ground and isolate groundwater. However, it inevitably requires the excavation of frozen soil. Frozen soil has a significant difference in properties from thawed soil. Its strength is about 10 to 20 times that of thawed soil, or even higher, which increases the difficulty of excavating frozen soil. General soil excavation methods are no longer applicable to frozen soil.

[0003] Currently, frozen soil excavation methods can be broadly categorized into three types: mechanical methods, heating and thawing methods, and blasting methods. Mechanical excavation is the most common method used in engineering construction. Because subway connecting passages are mostly located underground in urban areas, explosive blasting involves significant vibration and noise over a large area, and is generally prohibited. Therefore, mechanical excavation is the more prevalent method. Currently, manual excavation using handheld pneumatic picks is common, but this method is inefficient in breaking rock, requires a large workforce, and has a long construction period. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a simple and safe method for excavating subway connecting passages using carbon dioxide fracturing devices, which can safely and accurately blast frozen walls.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A method for excavating a subway connecting passage using a carbon dioxide fracturing device, comprising the following steps:

[0007] Step 1: Make holes on the working face, including four carbon dioxide fracturing holes arranged in a rhombus at the center of the working face, a central hole at the center of the rhombus, and peripheral holes around the carbon dioxide fracturing holes, wherein the central hole and peripheral holes serve as buffer holes.

[0008] Step 2: Arrange carbon dioxide fracturing devices in the carbon dioxide fracturing holes. Only one carbon dioxide fracturing device is installed in each fracturing hole. The decoupling and non-uniform charging method is adopted. The detonation wire extends out of the carbon dioxide fracturing hole and the opening of the carbon dioxide fracturing hole is plugged with a wedge. The wire is then connected to the detonator.

[0009] Step 3: Detonate all carbon dioxide fracturing devices simultaneously; after ventilation is completed in the tunnel and safety is confirmed, personnel enter the working face to retrieve the fracturing devices.

[0010] Step 4: After the fracturing is completed, check the excavation situation, and then manually use a pneumatic hammer to carry out secondary crushing.

[0011] Furthermore, the diameter of the carbon dioxide fracturing hole is 80 mm and the depth is 1.5 m, the diameter of the carbon dioxide fracturing device is 51 mm, and the carbon dioxide fracturing device is placed in the middle of the carbon dioxide fracturing hole.

[0012] Furthermore, the carbon dioxide fracturing device is 1.1m long, the air column length of the head section of the carbon dioxide fracturing hole is 10cm, and the air column length of the tail section of the carbon dioxide fracturing hole is 30cm.

[0013] Furthermore, the weight of liquid carbon dioxide injected into a single carbon dioxide fracturing device is 1000±50g.

[0014] Furthermore, the peripheral holes are arranged in a circle along the outline of the subway connecting passage and the overall shape of the water collection well, and the peripheral hole circle is reserved at least 20cm away from the outline of the subway connecting passage as a protective layer; the diameter and depth of the buffer hole are the same as the carbon dioxide fracturing hole.

[0015] Furthermore, nine peripheral holes are arranged along the outline of the subway connecting passage and nine peripheral holes are arranged along the outline of the water collection well.

[0016] Furthermore, the three carbon dioxide fracturing holes are located within the outline of the subway connecting passage, with one of the carbon dioxide fracturing holes in the middle of the outline of the subway connecting passage, the other two carbon dioxide fracturing holes at the bottom of the outline of the subway connecting passage and on the same horizontal line as the central hole and the two peripheral holes; and the last carbon dioxide fracturing hole in the middle of the outline of the water collection well.

[0017] Furthermore, the excavation method for the carbon dioxide fracturing device in the subway connecting passage also includes step 5: after the excavation is completed, a waterproof layer is constructed, and reinforced concrete structure construction is carried out.

[0018] The technical solution of the present invention achieves the following beneficial technical effects:

[0019] This invention utilizes a carbon dioxide fracturing device for excavating subway connecting passages. The fracturing process is spark-free and easy to operate. After blasting, no throwing funnel is formed. Although only the loosening and protrusion of frozen soil can be seen at the working face, the cracking of the frozen soil and rock layer produces a large number of gaps, making it easier to break the rock and soil with a pneumatic pick. Compared with pure manual pneumatic pick excavation, this invention can improve excavation efficiency and reduce the excavation period.

[0020] This invention employs weak loosening blasting technology and uncoupled non-uniform charging technology, which minimizes vibration damage to the frozen wall, reduces noise, eliminates flying rocks during blasting, is safer, and causes virtually no environmental pollution. It is highly suitable for the excavation of subway connecting passages.

[0021] This invention uses only four carbon dioxide fracturing holes. Through a reasonable layout of the charging holes and empty holes, it achieves simultaneous blasting and fracturing of subway connecting passages and water collection wells, saving the amount of carbon dioxide fracturing devices used and reducing blasting costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the outline and location of the connecting passage to be excavated;

[0023] Figure 2 This is a schematic diagram of the hole positions according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the carbon dioxide destructive charge loading according to an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the subway connecting passage after excavation and air venting support, according to an embodiment of the present invention.

[0026] The reference numerals in the figure are as follows: 1-Carbon dioxide fracturing hole, 2-Central hole, 3-Peripheral hole, 4-Protective layer, 5-Frozen wall, 6-Water collection well, 7-Reinforced concrete structure, 8-Melting soil, 9-Head section air column, 10-Middle section air column, 11-Tail section air column, 12-Carbon dioxide fracturing device, 13-Outline of subway connecting passage. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0028] The excavation method for subway connecting passages using carbon dioxide fracturing equipment involves excavating the tunnel face after the frozen wall 5 has been formed using carbon dioxide blasting, including the following steps:

[0029] Step 1: Create holes on the working face, including four carbon dioxide fracturing holes 1 arranged in a rhombus shape at the center of the working face, a central hole 2 located at the center of the rhombus, and peripheral holes 3 surrounding the carbon dioxide fracturing holes 1. The hole positions are as follows: Figure 2 As shown; the carbon dioxide fracturing holes 1 are located at the four corners of the rhombus, and the upper and lower ends of the rhombus are located within the outline of the subway connecting passage 13 and the outline of the water collection well 6, respectively; the length of the short diagonal of the rhombus is 27% of the width of the subway connecting passage, and the length of the long diagonal of the rhombus is 40% of the height of the subway connecting passage.

[0030] The central hole 2 provides an auxiliary free surface and expansion space for breaking frozen soil, and can reduce the throwing height of frozen soil; the central hole 2 and the peripheral holes 3 serve as buffer holes; the diameter and depth of the buffer holes are the same as those of the carbon dioxide fracturing hole 1; the buffer holes and the carbon dioxide fracturing hole 1 are drilled using a down-the-hole drill along a direction perpendicular to the working face.

[0031] Step 2: As Figure 3 As shown, carbon dioxide fracturing devices 12 are arranged in carbon dioxide fracturing holes 1, with only one carbon dioxide fracturing device 12 installed in each fracturing hole, using a fully uncoupled and non-uniform charging method. The detonating wire extends out of the carbon dioxide fracturing hole 1, with about 10cm of wire left for connection. The opening of the carbon dioxide fracturing hole 1 is plugged with a wooden wedge. After all the carbon dioxide fracturing devices 12 are installed, the wires of the four carbon dioxide fracturing holes 1 are connected in series, and the conductivity is measured. Finally, the wire is connected to the busbar of the detonator. Because the number of carbon dioxide fracturing devices used in this application is small, a series connection method is sufficient, and the operation is simple. Since the carbon dioxide fracturing device 12 will eventually fly out of the carbon dioxide fracturing hole 1 due to gas expansion, the purpose of plugging the opening of the carbon dioxide fracturing hole 1 with a wooden wedge is to prolong the time that the carbon dioxide fracturing device 12 is in the carbon dioxide fracturing hole 1, thereby improving the utilization rate of carbon dioxide gas.

[0032] Step 3: Simultaneously detonate all carbon dioxide fracturing devices 12: After the detonation head of the carbon dioxide fracturing device 12 is ignited by the detonation current, the low-voltage fuse in the heater triggers a rapid reaction, causing the carbon dioxide in the tube to rapidly change from liquid to gas. Within 40ms, the volume expands instantaneously by more than 600 times, and the pressure inside the tube can increase dramatically to 130MPa. When the preset pressure is reached, the constant pressure shear plate in the release head is opened, and the carbon dioxide gas bursts outward rapidly through the pressure relief hole. Utilizing the powerful thrust generated instantaneously, the carbon dioxide gas propels along the induced fracture surface, thereby fracturing the frozen rock and soil layer. The entire process is completed within 1 second.

[0033] After ventilation inside the tunnel is completed and safety is confirmed, personnel enter the working face to retrieve the fracturing device.

[0034] Step 4: After the fracturing is completed, check the excavation situation, and then manually use a pneumatic hammer for secondary crushing;

[0035] Step 5: After excavation, construct the waterproof layer and then carry out the reinforced concrete structure 7 construction to form a structure as shown in the image. Figure 4 The structure shown; subsequently, the frozen wall 5 melts, and the presence of the melted soil 8 will not affect the subway connecting passage and the water collection well 6;

[0036] It should be noted that prior to step 1, the frozen wall 5 of the subway connecting passage using artificial freezing technology had already been formed. The average temperature and thickness of the frozen wall 5 met the design requirements, and all excavation preparation work was completed, achieving the desired result. Figure 1 The state shown;

[0037] It should be noted that in step 2, the carbon dioxide storage tube inside the carbon dioxide fracturing device 12 is pre-injected with liquid carbon dioxide using a dedicated high-pressure pump. After the carbon dioxide fracturing hole 1 is drilled at the working face, two wires are connected to the inflation valve of the carbon dioxide fracturing device 12, which are then sealed with waterproof tape. The carbon dioxide fracturing device 12 is then placed into the carbon dioxide fracturing hole 1.

[0038] The carbon dioxide fracturing orifice 1 has a diameter of 80 mm and a depth of 1.5 m. The carbon dioxide fracturing device 12 has a diameter of 51 mm and a length of 1.1 m. The carbon dioxide fracturing device 12 is placed in the middle of the carbon dioxide fracturing orifice 1. The length of the air column 9 at the head of the carbon dioxide fracturing orifice 1 is 10 cm, and the length of the air column 11 at the tail of the carbon dioxide fracturing orifice 1 is 30 cm.

[0039] This invention employs a fully uncoupled, non-uniform charge technology, placing the carbon dioxide fracturing device 12 in the middle of the carbon dioxide fracturing hole 1; (1) the head section of the carbon dioxide fracturing hole 1 is an air column. The purpose of eliminating the sealing and blocking of the stemming mud is to allow the gas pressure inside the fracturing hole to quickly drop from its maximum value to atmospheric pressure, thereby reducing the thermal efficiency of the fracturing device at the face surface; (2) the fracturing device is installed in the middle section of the carbon dioxide fracturing hole 1. The carbon dioxide fracturing device 12 and the carbon dioxide fracturing hole 1 are uncoupled charges, and a middle section air column 10 is formed between the periphery of the carbon dioxide fracturing device 12 and the carbon dioxide fracturing hole 1. Due to the presence of air, the thermal efficiency of the liquid carbon dioxide after heating is greatly reduced. The initial impact pressure and tensile stress of the high-pressure gas acting on the borehole wall are converted into the crushing ring radius and the energy utilization rate is increased. At the same time, due to the extended action time of carbon dioxide gas, the formation of the cracks between the holes is more complete than that of coupled charge, the energy utilization is more efficient, and the block size is more uniform. Therefore, the use of non-coupled and non-uniform charge can improve the energy utilization of the fracturing device and improve the blasting effect. (3) The tail section of the carbon dioxide fracturing hole 1 is also an air column. The use of air-interval charge can reduce the peak impact pressure acting on the bottom wall of the fracturing hole, increase the stress wave action time, increase the impulse of the stress wave transmitted to the frozen soil, and the specific impulse is more uniformly distributed along the fracturing hole.

[0040] This invention employs a weak loosening blasting technique. The weight of liquid carbon dioxide injected into a single carbon dioxide fracturing device 12 is 1000±50g. Liquid carbon dioxide fracturing is a physical fracturing process, which is safer than explosive blasting, with a power approximately 1 / 6 that of explosives, and it produces no sparks during the fracturing process. The equivalent of the liquid carbon dioxide in this invention is approximately 25% of the emulsion explosive used in standard throwing blasting. The gas-filling end of the carbon dioxide fracturing device 12 faces the opening of the carbon dioxide fracturing hole 1, and the energy-dissipating end of the carbon dioxide fracturing device 12 faces the bottom of the carbon dioxide fracturing hole 1. After detonation, no throwing funnel is formed, and only the loosening and protrusion of the frozen soil can be seen on the working face, without damaging the frozen wall 5. Then, secondary fracturing is carried out manually using a pneumatic pick.

[0041] The function of the frozen wall 5 is to isolate water and bear load. If the frozen wall 5 is damaged, it will cause a serious safety production accident. Therefore, peripheral holes 3 are set around the carbon dioxide fracturing hole 1. The peripheral holes 3 are arranged in a circle along the outline of the subway connecting passage and the water collection well 6. The peripheral holes 3 are reserved at least 20cm thick from the outline of the subway connecting passage as a protective layer 4. The diameter and depth of the buffer hole are the same as those of the carbon dioxide fracturing hole 1. The main purpose of using peripheral holes 3 is to reduce the back impact and seismic effect of the fracturing hole, control over-explosion, and protect the stability of the frozen wall 5. The thickness of the protective layer 4 is at least 20cm. The thickness of the peripheral protective layer 4 can be appropriately increased to avoid over-excavation of the frozen wall 5.

[0042] Specifically, nine peripheral holes 3 are arranged along the outline 13 of the subway connecting passage, and nine peripheral holes 3 are arranged along the outline of the water collection well 6; three carbon dioxide fracturing holes 1 are within the outline 13 of the subway connecting passage, one of which is in the middle of the outline 13, and the other two are at the bottom of the outline 13 and are on the same horizontal line as the central hole 2 and the two peripheral holes 3. After the row of carbon dioxide fracturing holes 1, central hole 2 and two peripheral holes 3 are blasted, the bottom of the subway connecting passage is formed; the last carbon dioxide fracturing hole 1 is in the middle of the outline of the water collection well 6; the bottom of the subway connecting passage is separated from the top of the water collection well 6.

[0043] This invention employs weak loosening blasting technology, non-coupled and non-uniform charging technology, sets up anti-blast holes in the center and around the connecting channel, and sets up a protective layer 4 around the perimeter, achieving the technical effects of reducing blasting vibration, ensuring the safety of the frozen wall 5, improving the utilization rate of carbon dioxide blasting energy, and improving rock breaking efficiency.

[0044] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for excavating a subway connecting passage using a carbon dioxide fracturing device, characterized in that, The following steps are included in the process of excavating the working face of the connecting passage formed by the frozen wall (5) using the carbon dioxide blasting method: Step 1: Make holes on the working face, including four carbon dioxide fracturing holes (1) arranged in a rhombus at the center of the working face, a central hole (2) set at the center of the rhombus, and peripheral holes (3) surrounding the carbon dioxide fracturing holes (1), wherein the central hole (2) and peripheral holes (3) serve as buffer holes. Step 2: Arrange carbon dioxide fracturing device (12) in carbon dioxide fracturing hole (1). Only one carbon dioxide fracturing device (12) is installed in each fracturing hole. The decoupling and non-uniform charging method is adopted. The detonation wire extends out of the carbon dioxide fracturing hole (1) and the opening of the carbon dioxide fracturing hole (1) is plugged with a wedge. The wire is connected to the detonator. Step 3: Simultaneously detonate all carbon dioxide fracturing devices (12); After ventilation in the tunnel is completed and safety is confirmed, personnel enter the working face to retrieve the fracturing devices. Step 4: After the fracturing is completed, check the excavation situation, and then manually use a pneumatic hammer for secondary crushing; The carbon dioxide fracturing hole (1) has a diameter of 80 mm and a depth of 1.5 m. The carbon dioxide fracturing device (12) has a diameter of 51 mm and is placed in the middle of the carbon dioxide fracturing hole (1). The peripheral holes (3) are arranged in a circle along the outline of the subway connecting passage and the water collection well (6). The peripheral holes (3) are reserved at least 20cm away from the outline of the subway connecting passage as a protective layer (4). The diameter and depth of the buffer hole are the same as those of the carbon dioxide fracturing hole (1). The length of the carbon dioxide fracturing device (12) is 1.1m, the length of the air column (9) at the head of the carbon dioxide fracturing hole (1) is 10cm, and the length of the air column (11) at the tail of the carbon dioxide fracturing hole (1) is 30cm; the weight of liquid carbon dioxide injected into a single carbon dioxide fracturing device (12) is 1000±50g. The three carbon dioxide fracturing holes (1) are within the outline (13) of the subway connecting passage. One of the carbon dioxide fracturing holes (1) is in the middle of the outline (13) of the subway connecting passage. The other two carbon dioxide fracturing holes (1) are at the bottom of the outline (13) of the subway connecting passage and are on the same horizontal line as the central hole (2) and the two peripheral holes (3). The last carbon dioxide fracturing hole (1) is in the middle of the outline of the water collection well (6).

2. The method for excavating subway connecting passages using carbon dioxide fracturing equipment according to claim 1, characterized in that, Nine peripheral holes (3) are arranged along the outline of the subway connection passage (13) and nine peripheral holes (3) are arranged along the outline of the water collection well (6).

3. The method for excavating a subway connecting passage using a carbon dioxide fracturing device according to claim 1, characterized in that, It also includes step 5: After the excavation is completed, the waterproof layer is constructed and the reinforced concrete structure (7) is constructed.

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