Quick T-joint structure for new and old concrete air ducts of coal mine and construction method of quick T-joint structure

Abstract

The invention relates to the field of coal mine ground ventilation system air duct engineering, in particular to a coal mine new and old concrete air duct rapid T-joint structure and a construction method thereof. According to the structure, through the high-strength glue planting anchoring technology and the multi-dimensional steel bar planting connecting technology, the special-shaped reinforcing steel plate and the cast-in-place end of the newly-built air duct are tightly engaged, and a composite joint system with the ultrahigh shear rigidity and the high air tightness is formed. According to the matched construction operation method, the process logic is reconstructed, a newly-built air duct main structure and an outer side reinforcing component are constructed on the periphery, and after the strength of the newly-built part reaches the standard, short air suspension is carried out so as to carry out precise wall cutting and punching and rapid assembling and welding of internal steel components. According to the invention, the fatal hidden danger of underground gas accumulation caused by long-term wind stop in the prior art is completely eliminated, absolute blocking of system airtightness under extremely high negative pressure is realized, and the construction and installation cost and wind resistance and power consumption are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of ventilation duct technology for coal mine ground ventilation systems, and in particular to a rapid T-connection structure for new and old concrete ventilation ducts in coal mines and its construction method. Background Technology

[0002] With the increase in coal production capacity, the ventilation volume and negative pressure of the original single-duct system are often seriously insufficient. It is usually necessary to add a new parallel duct and connect it to the original duct to achieve parallel ventilation of two ducts.

[0003] Currently, ventilation ducts commonly employ reinforced concrete box-type structures. In the T-junction renovation of old and new ventilation ducts, the conventional cast-in-place connection method requires first completely stopping ventilation, removing the original duct sidewalls to create openings, then lapping and binding the reinforcing bars of the new duct with the exposed main reinforcing bars of the original duct, and finally erecting formwork and casting the entire structure in place. This traditional process has the following serious drawbacks: First, the entire process of breaking up concrete, setting up formwork, pouring in place, and initial curing must be carried out under ventilation-stopped conditions. Some of the expansion and modification projects have resulted in production disruptions lasting for months, severely restricting the release of coal production capacity and posing a significant risk of underground gas exceeding limits in outburst-prone mines.

[0004] Secondly, large-scale excavation directly cuts off the closed loop of the original air duct, which can easily cause stress concentration and damage at the corner of the opening; due to the difference in material shrinkage rate, the interface between the old and new concrete is prone to micro-cracks and serious air leakage under the long-term impact of high-pressure airflow and piston wind, which greatly increases the waste power loss of the ventilation fan.

[0005] In addition, regarding structural reinforcement, the U-shaped steel shed internal support reinforcement method tried by some mines has fatal drawbacks such as easy to twist and deform under lateral pressure and severe reduction of the wind passage cross section, which cannot meet the stiffness and hydrodynamic requirements of the ground heavy-load main air duct node.

[0006] Therefore, developing a rapid T-connection structure and construction method for new and old concrete ventilation ducts in coal mines that is mechanically stable, has excellent airtightness, and can minimize construction downtime is of great practical engineering significance. Summary of the Invention

[0007] To overcome the engineering defects in the existing technology for the expansion and renovation of the main air duct network of the ground ventilation system in coal mines, such as the need for long-term ventilation shutdown, easy shrinkage and cracking at the interface between the old and new structures leading to serious air leakage, and difficulty in ensuring the spatial shear stiffness at the joint, this invention provides a rapid T-connection structure for new and old concrete air ducts in coal mines and its construction method, which has reasonable mechanical design, good fluid dynamics compatibility, short construction period, and minimal interference with normal mine production.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: The rapid T-joint structure for new and old concrete ventilation ducts in coal mines includes an outer top anchored steel plate, an outer side anchored steel plate, an inner bottom welded steel plate, an inner top welded steel plate, an inner middle anchored angle steel, a connecting plate, a port column, and a port beam. The outer top anchored steel plate is fixed to the top of the original ventilation duct roof and arranged along the edge of the opening. The outer side anchored steel plate is set along the outer perimeter of the opening. The inner bottom welded steel plate is fixed to the top of the original ventilation duct floor. The inner top welded steel plate is fixed to the bottom of the original ventilation duct roof. The inner middle anchored angle steel is fixed to the middle section of the original ventilation duct. The connecting plate welds the outer side anchored steel plate and the inner middle anchored angle steel together. The port column and port beam form an irregular cross-section and are set at the port of the new ventilation duct. The new ventilation duct port is located outside the original ventilation duct. The port column and port beam are vertically and tightly connected to the original ventilation duct through the connecting components set on the outer side anchored steel plate.

[0009] Furthermore, in order to better realize the present invention, the outer top anchor steel plate is arranged 60mm away from the edge of the opening, the outer top anchor steel plate is 150mm wide and 8mm thick, and the two ends of the outer top anchor steel plate extend 600mm beyond the opening; the outer top anchor steel plate is fixed by a single row of adhesive anchor bolts with a spacing of 200mm.

[0010] Furthermore, in order to better realize the present invention, the two ends of the outer top anchor steel plate are fixed with steel plate pressure strips. The steel plate pressure strips are 150mm wide, 8mm thick, and 450mm long, and two adhesive anchor bolts are set at each end for fixing.

[0011] Furthermore, in order to better realize the present invention, the width of the outer side anchor steel plate is 250mm and the thickness is 10mm; the outer side anchor steel plate is fixed by double rows of cross-arranged adhesive anchor bolts with a spacing of 200mm.

[0012] Furthermore, to better realize the present invention, short ribs are welded to the outer surface of the outer side anchor steel plate. The short ribs have a diameter of 16mm, a spacing of 250mm, and a length of 70mm. Rebars are provided on the outer side of the outer side anchor steel plate. The rebars have a diameter of 16mm, a spacing of 250mm, a total length of 350mm, and an implantation depth of 180mm. The port column and port beam are connected to the original air duct through the short ribs and rebars.

[0013] Furthermore, in order to better realize the present invention, the inner bottom welded steel plate is set along the entire length, with a width of 250mm and a thickness of 10mm. The inner bottom welded steel plate is fully welded to the main reinforcing steel exposed after the protective layer of the original air duct bottom plate is chiseled out. The inner top welded steel plate has a width of 250mm and a thickness of 10mm. The inner top welded steel plate is fully welded to the main reinforcing steel exposed after the protective layer of the original air duct top plate is chiseled out.

[0014] Furthermore, in order to better realize the present invention, the inner middle anchor angle steel is of model L180×110×10 and is fixed by adhesive anchor bolts with a single row spacing of 200mm; the width of the connecting plate is 100mm and the thickness is 6mm, and the spacing between two adjacent connecting plates is 200mm.

[0015] This invention also provides a construction method for a rapid T-joint structure of new and old concrete ventilation ducts in coal mines, comprising the following steps: Step A: Clean the concrete surface around the opening of the original air duct down to the structural layer, process and install the outer top anchor steel plate and the outer side anchor steel plate, and complete the rebar installation at the predetermined position. Step B involves pouring and constructing the port beams and port columns of the new air duct outside the original air duct. Step C: Suspend ventilation inside the original air duct and open a hole in the original air duct using a combination of manual excavation and concrete cutting machine. Step D involves the installation and welding of the inner bottom welded steel plate, the inner top welded steel plate, the inner middle anchored angle steel, and the connecting gusset plate. After the structural reinforcement and connection are completed, the ventilation of the air duct is restored.

[0016] Furthermore, in order to better realize the present invention, in step A, when cleaning the concrete surface, the exposed steel bars need to be derusted and protected against corrosion, the peeling debris and corrosion layer on the base surface need to be removed, and the surface to be bonded needs to be ground until the fresh concrete structure surface is completely exposed. After cleaning the dust in the holes, structural adhesive is injected to install the anchor bolts.

[0017] Furthermore, in order to better realize the present invention, in step D, before the inner bottom welded steel plate and the inner top welded steel plate are installed, the concrete protective layer of the original air duct bottom plate and top plate needs to be manually chiseled until the original structural main reinforcement is exposed. Then the steel plate is reliably welded to the main reinforcement to form a closed stress system.

[0018] The beneficial effects of this invention are: (1) The construction of the new ventilation duct and the connection structure between the old and new ventilation ducts were carried out first, and the ventilation was stopped and the opening was opened, which reduced the impact on normal ventilation in the well. (2) The original air duct openings were reinforced with anchored steel plates, and the new air duct ports were reinforced with port beams and port columns to ensure the strength of the connection structure. (3) The installation of short steel bars and anchor steel plates on the outer side of the opening ensures the airtight connection between the old and new air ducts and avoids the occurrence of air leakage accidents.

[0019] (4) The construction process is simple, the construction speed is fast, and the construction cost is low. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the connection between the old and new air ducts in this invention; Figure 2 This is an elevation view of the hole anchoring steel plate reinforcement of the present invention; Figure 3 This is a cross-sectional view of the hole anchoring steel plate reinforcement of the present invention.

[0021] In the picture, 1. Outer top anchor steel plate; 2. Outer side anchor steel plate; 3. Inner bottom welded steel plate; 4. Inner top welded steel plate; 5. Inner middle anchor angle steel; 6. Connecting gusset plate; 7. Port column; 8. Port beam. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] Combined with appendix Figure 1 To be continued Figure 3 As shown, this invention discloses a rapid T-joint structure for new and old concrete ventilation ducts in coal mines, specifically designed for heavy-load and high-negative-pressure operation. This structural system highly integrates three subsystems in its spatial form: an external prestressed pre-reinforcement module, a high-rigidity interlocking module for new and old nodes, and an internal closed-loop reinforcement and encapsulation module, forming a composite load-bearing component with excellent synergistic stress-bearing characteristics. Specifically, the structure mainly includes an outer top anchored steel plate 1, an outer side anchored steel plate 2, an inner bottom welded steel plate 3, an inner top welded steel plate 4, an inner middle anchored angle steel 5, a connecting plate 6, and newly cast-in-place end columns 7 and end beams 8 designed for docking.

[0025] The table below details the material specifications and design parameters of the key metal reinforcement components in this embodiment to illustrate the basis for their mechanical strength:

[0026] Before connecting parallel new air ducts to the main ventilation network on the coal mine surface, the mechanical stability of the original box-type reinforced concrete air duct structure must be absolutely guaranteed. Traditional methods, due to blindly creating openings, are prone to causing instantaneous subsidence of the roof or large-scale instability and collapse of the sidewalls. This embodiment adopts the following reinforcement concept: First, an outer top anchored steel plate 1 is installed. This steel plate is attached to the top area of ​​the outer edge of the original air duct roof and is strictly arranged parallel to the edge of the planned opening. To prevent concrete punching shear failure or brittle cracking due to tensile stress concentration at the opening edge under high stress gradient, the outer top anchored steel plate 1 is not tightly attached to the opening, but is set back outwards, leaving a safety buffer distance of 60mm from the edge of the opening. The geometric dimensions of this steel plate are set to be 150mm wide and 8mm thick. Based on the principle of sufficient anchorage length, the two ends of the steel plate extend outwards, each exceeding the full width of the opening by 600mm, thus forming a reliable anchorage extension section for stress transmission to the outer complete structure.

[0027] Regarding the anchoring process parameters, the outer top anchored steel plate 1 is locked in place by M12 adhesive-coated anchor bolts fixed with a single row of holes, with the longitudinal spacing strictly set at 200mm. Furthermore, to address the common problem in bridge and underground space reinforcement projects where the ends of bonded steel reinforcement are prone to brittle peeling failure due to peak shear stress, mechanical end-pressing and fixing of the outer top anchored steel plate 1 is specifically employed at both ends. The dimensions of this adhesive-coated steel plate are matched to the main steel plate, being 150mm wide, 8mm thick, and 450mm long. Two M12 adhesive-coated anchor bolts are used for independent pressure at each end, forming a self-balancing tensile band with end-locking functionality for the entire top reinforcement component.

[0028] The vertical lateral facades surrounding the ventilation duct opening are the core area of ​​the entire T-joint structure, resisting geological shear deformation, overcoming complex three-dimensional lateral earth pressure, and resisting the expansion force of internal high-frequency pulsating wind pressure. For this area, the outer side anchored steel plate 2 is laid continuously along the outer perimeter of the planned excavation opening. Compared to the top, the side stress is more complex, therefore its cross-sectional dimensions are increased to a width of 250mm and a thickness of 10mm. The anchoring method has also been systematically strengthened, abandoning the single-row design and upgrading to a double-row, cross-arranged arrangement of M12 adhesive anchor bolts with a spacing of 200mm. This double-row, staggered anchoring layout makes the shear stress distribution at the interface between the ventilation duct concrete and the high-strength structural adhesive layer more uniform and wider.

[0029] One of the core inventive points of this invention is the complex mechanical structure design of the outer working surface of the outer side anchor steel plate 2, which achieves a high-strength mechanical bond between the original duct reinforcement system and the newly constructed cast-in-place concrete structure of the duct. On one hand, the steel plate surface is densely welded with an array of short reinforcing bars. These bars are made of high-quality low-carbon steel, 16mm in diameter, and distributed in a grid pattern with horizontal and vertical spacing of 250mm, extending outwards by 70mm. On the other hand, along the outer side of the vertical side anchor steel plate, long-lasting reinforcing bars are embedded diagonally or vertically into the original duct concrete using deep-hole injection technology. These reinforcing bars also have a diameter of 16mm and a hole spacing of 250mm. The total length of these reinforcing bars is set at 350mm, with a precisely controlled implantation depth of 180mm into the original concrete, ensuring that the pull-out failure load of the reinforcing bars is far greater than the yield load of the reinforcing steel.

[0030] When the port beams 8 and port columns 7 of the newly constructed air duct are specially designed with irregular cross-sections based on aerodynamic characteristics to facilitate smooth airflow during the cast-in-place operation, the aforementioned pre-designed short reinforcement array and the rebar tails extending from the steel plate surface are completely submerged and tightly wrapped within the high-grade cast-in-place concrete of the new air duct. After the concrete hydrates and hardens, the function of the outer side anchored steel plate 2 changes; it is not only a reinforcement structure to prevent damage and cracking of the original air duct's outer surface, but also becomes a core shear-resistant connection key connecting the old and new building structures. This deep mechanical anchoring completely eliminates the concrete cold joint shrinkage sliding surface that is inevitably generated by traditional cast-in-place connection methods, effectively preventing joint fatigue cracking and continuous air leakage hazards during high negative pressure pulse airflow operation.

[0031] From the perspective of the original duct interior, the structural reinforcement logic shifted from external surface crack prevention and stress transfer to internal rigid circumferential skeleton reconstruction. Internally, there are inner bottom welded steel plates 3 and inner top welded steel plates 4. Inner bottom welded steel plate 3 is located at the top of the original duct floor slab and runs the entire length of the opening, with a width of 250mm and a thickness of 10mm; inner top welded steel plate 4 is located at the bottom of the original duct top slab, with a width of 250mm and a thickness of 10mm. These two main load-bearing plates were not fixed using traditional surface bonding or simple expansion bolts, as these would not be able to withstand the out-of-plane torsional forces caused by the truncation of the floor and top slabs. The connection method required construction workers to thoroughly excavate the concrete protective layer of the original duct floor and top slabs until the original structural main reinforcing steel was fully exposed. Subsequently, the inner edges of steel plates 3 and 4 were fully welded to the exposed original structural main reinforcing steel. This forced the addition of high-strength, thick steel plates into the original primary load-bearing frame of the air duct, which had already been cut off, greatly enhancing the bending stiffness at the nodes above and below the opening.

[0032] To provide effective support within the sidewall to resist the lateral pressure of the deep surrounding rock and the internal vacuum negative pressure difference, an inner central anchored angle steel 5 was installed vertically. To meet the instability resistance requirements under a large slenderness ratio, a large-section heavy-duty model L180×110×10 was selected for the angle steel, and it was firmly bound to the inner wall of the original air duct using adhesive anchor bolts spaced 200mm in a single row.

[0033] However, simply having independent internal and external plates is insufficient to form a three-dimensional resistance. Therefore, this embodiment introduces an array of connecting plates 6. The dimensions of the connecting plates 6 have been rigorously calculated, with a width of 100mm and a thickness of 6mm, arranged in an extremely dense array along the height direction at a spacing of 200mm. Each plate is fully welded to the outer side anchored steel plate 2 and the inner center anchored angle steel 5 at both ends. This structure originates from the concept of lattice columns, widely used in high-rise buildings or heavy industrial plants to avoid conflicts with the longitudinal reinforcement of large-section reinforced concrete. Just as the core function of the connecting plates in lattice columns is to ensure the overall rigidity of the separated limbs and bear the enormous shear force generated by the cross-section, the connecting plates 6 in this structure pass through the core area of ​​the opening cross-section at high frequency, tightly and rigidly connecting the external rigid reinforcing steel plate and the internal bending angle steel in a spatial dimension. From a structural mechanics perspective, it fundamentally locks all relative displacement and torsional degrees of freedom of the old and new structural concrete components at the interface.

[0034] In conjunction with the aforementioned complex structural hardware, this invention delves into the spatiotemporal constraints of safe construction in mines, proposing a standardized construction method for rapid T-joint structures of new and old concrete ventilation ducts in coal mines, characterized by extremely stringent time node control and high safety redundancy. This method divides the construction process into four clearly defined process nodes, completely deconstructing the traditional long-cycle ventilation shutdown operation mode.

[0035] Step A, Preliminary Construction of the External Reinforcement System and Interface Preparation: This stage is primarily conducted under the condition of maintaining full load and high negative pressure ventilation of the mine's main ventilation fan without interrupting production. The construction team accurately conducted surveying and layout outside the original ventilation duct. The existing concrete surface around the planned excavation opening of the original ventilation duct was thoroughly cleaned. According to the first step of the high-strength anchor bonding operation specifications, all aged protective layers, peeling debris, voids, and corrosion layers on the base surface were completely removed. For any exposed structural steel bars during the cleaning process, professional anti-corrosion and rust-removing agents were used for rust and corrosion prevention. Subsequently, the bonding surfaces of the steel plates to be bonded were deeply mechanically ground until the fresh concrete structural surface was completely exposed. After cleaning the dust inside the holes and on the surface, the outer top anchor steel plate 1 and the outer side anchor steel plate 2 were precisely processed according to the drawings. Fixed-point drilling was performed, high-performance two-component epoxy resin structural adhesive was injected, anchor bolts were installed, and tightened for curing. Deep-hole rebar installation was completed at the same frequency. During the curing of the colloid, the steel plate is kept under stable pressure to completely eliminate any air bubbles that may remain at the interface, forming an absolutely dense and airtight adhesive surface.

[0036] Step B, Large-volume Casting and Curing of the New Air Duct Interface: During this stage, the original air duct remains operational. The construction unit concentrates resources on completing the reinforcement binding and precision formwork for the port beam 8 and port column 7 of the new parallel air duct outside the original air duct. When pouring high-grade impermeable concrete, ensure that all pre-welded short reinforcement arrays on the outer side anchor plate 2 and the exposed deep-hole rebars are completely submerged and wrapped by the cast-in-place concrete, and use a high-frequency vibrator for thorough compaction. It is essential to strictly wait for the concrete at the junction of the new air duct to undergo standard curing and for its mechanical strength to fully reach 100% of the design value.

[0037] Step C, Short-Term Ventilation Interruption and Micro-Vibration Opening: This step is the only one in the entire renovation project that necessitates the interruption of normal underground ventilation in the mine. Upon receiving the order to stop the main ventilation fan, the demolition team quickly moved in. Using a combination of a water-cooled diamond wire saw and a heavy-duty circular saw, and employing micro-vibration techniques, they precisely cut and removed the thick walls of the original ventilation duct along the predetermined lines. Since the most demanding external anchoring and stress transfer of the new structure had been completed and were fully effective, the severe stress redistribution caused by the opening in the original ventilation duct structure had been completely absorbed by the outer steel frame.

[0038] Step D, Internal Rapid Restoration and Ventilation Test: After the cut concrete wall blocks are removed, the small protective layer of the top and bottom slabs inside the newly opened opening is immediately chipped away with a pneumatic hammer until the original structural main longitudinal reinforcement bars are clearly exposed. Then, the inner bottom welded steel plate 3, the inner top welded steel plate 4, and the inner middle anchored angle steel 5 are placed together. Welders quickly and continuously weld the large inner and outer steel plate assemblies to the connecting gusset plates 6 and the original structural main reinforcement bars. After the welding is confirmed to be correct and the area has cooled down, workers spray a high-polymer sealing and anti-corrosion coating on all joints and heat-affected zones. After quality inspectors confirm that the overall T-joint structure system is physically fully sealed and meets the air leakage prevention specifications, a ventilation command is sent to the ground control room to restore ventilation in the air ducts.

[0039] This construction method simplifies the work during the extremely high-risk period of ventilation shutdown and tunnel opening, reducing it to simple mechanical cutting and demolition and standardized metal structural component welding and placement. It eliminates the most uncontrollable aspects of traditional processes, such as the construction of underground concrete formwork systems and the long waiting period for strength enhancement and curing, thus minimizing the risk of system failure.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A quick T-joint structure for new and old concrete ventilation ducts in coal mines, comprising an outer top anchored steel plate (1), an outer side anchored steel plate (2), an inner bottom welded steel plate (3), an inner top welded steel plate (4), an inner middle anchored angle steel (5), a connecting plate (6), a port column (7), and a port beam (8), characterized in that: The outer top anchor steel plate (1) is fixed to the top of the original air duct top plate and arranged along the edge of the opening; the outer side anchor steel plate (2) is set along the outer perimeter of the opening; the inner bottom welded steel plate (3) is fixed to the top of the original air duct bottom plate; the inner top welded steel plate (4) is fixed to the bottom of the original air duct top plate; the inner middle anchor angle steel (5) is fixed to the inner middle section of the original air duct; the connecting plate (6) welds the outer side anchor steel plate (2) and the inner middle anchor angle steel (5) together; the port column (7) and the port beam (8) form an irregular cross section and are set at the port of the new air duct. The new air duct port is located outside the original air duct. The port column (7) and the port beam (8) are vertically and tightly connected to the original air duct through the connecting components set on the outer side anchor steel plate (2).

2. The rapid T-connection structure for new and old concrete ventilation ducts in coal mines according to claim 1, characterized in that: The outer top anchor steel plate (1) is arranged 60mm away from the edge of the opening. The outer top anchor steel plate (1) is 150mm wide and 8mm thick. Both ends of the outer top anchor steel plate (1) extend 600mm beyond the opening. The outer top anchor steel plate (1) is fixed by a single row of adhesive anchor bolts with a spacing of 200mm.

3. The rapid T-connection structure for new and old concrete ventilation ducts in coal mines according to claim 2, characterized in that: The two ends of the outer top anchor steel plate (1) are fixed with steel plate pressure strips. The steel plate pressure strips are 150mm wide, 8mm thick, and 450mm long. Two adhesive anchor bolts are set at each end for fixing.

4. The rapid T-connection structure for new and old concrete ventilation ducts in coal mines according to claim 1, characterized in that: The outer side anchor plate (2) has a width of 250mm and a thickness of 10mm; the outer side anchor plate (2) is fixed by double-row cross-arranged adhesive anchor bolts with a spacing of 200mm.

5. The rapid T-connection structure for new and old concrete ventilation ducts in coal mines according to claim 4, characterized in that: The outer surface of the outer side anchor steel plate (2) is welded with short ribs, the diameter of which is 16mm, the spacing is 250mm, and the length is 70mm; the outer side of the outer side anchor steel plate (2) is provided with anchor bars, the diameter of which is 16mm, the spacing is 250mm, the total length is 350mm, and the implantation depth is 180mm; the port column (7) and the port beam (8) are connected to the original air duct through the short ribs and anchor bars.

6. The rapid T-connection structure for new and old concrete ventilation ducts in coal mines according to claim 1, characterized in that: The inner bottom welded steel plate (3) is set along the entire length, with a width of 250mm and a thickness of 10mm. The inner bottom welded steel plate (3) is fully welded to the main reinforcing bars exposed after the protective layer of the original air duct bottom plate is chiseled. The inner top welded steel plate (4) has a width of 250mm and a thickness of 10mm. The inner top welded steel plate (4) is fully welded to the main reinforcing bars exposed after the protective layer of the original air duct top plate is chiseled.

7. The rapid T-connection structure for new and old concrete ventilation ducts in coal mines according to claim 1, characterized in that: The inner middle anchor angle steel (5) is model L180×110×10 and is fixed by adhesive anchor bolts with a single row spacing of 200mm; the width of the connecting plate (6) is 100mm and the thickness is 6mm, and the spacing between two adjacent connecting plates (6) is 200mm.

8. A construction method for a rapid T-joint structure of new and old concrete ventilation ducts in coal mines as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step A: Clean the concrete surface around the opening of the original air duct down to the structural layer, process and install the outer top anchor steel plate (1) and the outer side anchor steel plate (2), and complete the rebar installation at the predetermined position. Step B involves pouring and constructing the port beam (8) and port column (7) of the new air duct outside the original air duct. Step C: Suspend ventilation inside the original air duct and open a hole in the original air duct using a combination of manual excavation and concrete cutting machine. Step D involves the installation and welding of the inner bottom welded steel plate (3), the inner top welded steel plate (4), the inner middle anchored angle steel (5), and the connecting gusset plate (6). After the structural reinforcement connection is completed, the ventilation of the air duct is restored.

Images