A super-large crushing chamber downward slicing pressure control construction method with double shafts and coordinated ventilation

Abstract

The application provides a double-sluicing shaft coordinated ventilation super-large broken chamber downward slicing pressure control construction method, which comprises the following steps: carrying out geological surrounding rock grading survey to determine a support system, completing measurement and line laying, calibrating chamber contour, sluicing shaft position, guide chamber strike and slope control line; constructing through low-position sluicing shaft and high-position sluicing shaft to form a differential pressure ventilation system with low-position air inlet and high-position air outlet; constructing a turning guide chamber with a set slope from the bottom of the main transportation inclined shaft to form a passageway for trackless equipment; dividing the chamber into several uniform slices from top to bottom, applying temporary shotcrete sealing surrounding rock after each slice is excavated, and then following up to implement permanent support; carrying out drilling and blasting operation by adopting smooth blasting process, ventilating and discharging smoke after blasting; and transporting slag and stone through the turning guide chamber and by the low-position sluicing shaft to external transportation. The application uniformly slices the super-high chamber from top to bottom, releases high ground stress of surrounding rock layer by layer, reduces stress concentration of large-span free surface, controls development of surrounding rock loose circle and reduces collapse risk.

Description

Technical Field

[0001] This invention relates to the field of mining construction technology, and in particular to a method for downward layered pressure control construction of an ultra-large crushed chamber with coordinated ventilation of two chutes. Background Technology

[0002] With the development of deep mining of mineral resources, mines are gradually shifting from open-pit to underground mining. A large number of crushing stations, hoisting systems, and transfer equipment need to be located underground, leading to a continuous increase in the excavation span and height of underground crushing chambers, resulting in ultra-high and ultra-large cross-section chambers. These chambers have large exposed rock areas, wide open surfaces, and significant high ground stress. Under Class III-IV fractured rock conditions, they are highly susceptible to spalling, roof collapse, and surrounding rock instability disasters.

[0003] In existing technologies, conventional tunnel construction methods mainly include the one-time excavation method, the pilot tunnel excavation method, and the upward layered construction method. However, each of these methods has inherent defects. The one-time excavation method is only suitable for small-section tunnels and cannot be adapted to large tunnels. The stress concentration in the surrounding rock during a single excavation is severe, resulting in a very high risk of collapse. The pilot tunnel excavation method requires significant height for later excavation work, necessitating frequent erection of high-altitude work platforms, resulting in high labor input, lengthy setup and dismantling times, numerous loose rocks on the roof, a low safety factor, and slow construction progress. The upward layered construction method excavates from bottom to top, leaving the upper surrounding rock suspended for extended periods. Muck removal relies on electric scrapers and small machinery for transport, leading to low efficiency, significant overlap in work processes, and widespread delays in support.

[0004] Therefore, traditional techniques generally suffer from problems such as smog retention at the top of the chamber, poor ventilation, large disturbance to the surrounding rock during blasting, conflict between slag removal and support procedures, and excessively long periods of exposed roof space, making them unsuitable for use in ultra-large underground chambers. Summary of the Invention

[0005] This invention provides a method for downward layered pressure control construction of an ultra-large fracture chamber with coordinated ventilation of two chutes, in order to solve at least one of the technical problems mentioned above.

[0006] This invention provides a method for downward stratified pressure control construction of an ultra-large fractured chamber with coordinated ventilation through dual chutes, comprising: S1. Conduct geological and rock classification investigation to determine the support system, complete surveying and setting out, and mark the outline of the chamber, the location of the chute, the direction of the guide tunnel and the slope control line; S2. Construction connects the low-level chute and the high-level chute. The low-level chute serves as an air intake and slag transfer channel, while the top of the high-level chute's circulation chamber serves as a smoke exhaust channel, forming a differential pressure ventilation system with low-level air intake and high-level air exhaust. S3. Construct a turnaround guide tunnel with a set slope from the bottom of the main transport inclined shaft to form a passage for trackless equipment; S4. Divide the chamber into several uniform layers from top to bottom, and excavate layer by layer according to the principle of first top and then bottom, first middle and then both sides. During excavation, reserve a buffer protection layer of surrounding rock around the chamber. S5. After each layer of excavation is completed, temporary shotcrete is applied to seal the surrounding rock, followed by permanent support to control the time of exposure of the surrounding rock. S6. Smooth blasting technology shall be used for drilling and blasting operations, and ventilation and smoke exhaust shall be carried out after blasting. S7. Trackless slag removal equipment is used to transfer the slag through the return guide tunnel and then to the low-level chute for external transport.

[0007] According to the present invention, a method for downward layered pressure control construction of an ultra-large fractured chamber with coordinated ventilation of two chutes is provided. In step S3, the cross-section of the reversing guide tunnel is a 4.0m*4.0m three-center arch cross-section, and the construction slope of the guide tunnel is 11°-15°. First, it is excavated towards the high-level chute, and after reaching the designated elevation, it is reversed and excavated towards the low-level chute to achieve breakthrough.

[0008] According to the present invention, a method for constructing a super-large fractured chamber with dual chutes and coordinated ventilation, with downward layered pressure control, in step S4, the height of the chamber is divided into multiple uniform layers from top to bottom, and the excavation height of a single layer is controlled at 3.2m-3.8m; the excavation height of each layer is first excavated with a small cross section, and then expanded to the design outline, with a 0.5m surrounding rock buffer protection layer reserved around the chamber.

[0009] According to the present invention, a method for downward layered pressure control construction of a super-large fractured chamber with dual chutes and coordinated ventilation is provided. In step S5, after excavation, a temporary shotcrete with a thickness of 50 mm is applied to seal the surrounding rock, and the exposure time of the surrounding rock is controlled within 30 minutes.

[0010] According to the present invention, a method for constructing a large fractured chamber with dual-well coordinated ventilation and downward layered pressure control is provided. In step S6, a pneumatic rock drill is used to drill holes and cut grooves in a straight line with a peripheral hole spacing of 400-500mm. The blasting operation is carried out by reverse decoupled charge, hole plugging with stemming material, and non-electric micro-differential detonation.

[0011] According to the present invention, a method for downward layered pressure control construction of an ultra-large fractured chamber with dual-well coordinated ventilation is provided. In step S1, the geological surrounding rock is classified into Class III and Class IV surrounding rock. The Class III surrounding rock is supported by a combination of shotcrete, anchor, and mesh; the Class IV surrounding rock is supported by shotcrete, anchor, mesh, anchor cables, and steel grid.

[0012] According to the present invention, a method for downward layered pressure control construction of an ultra-large fractured chamber with dual-well coordinated ventilation is provided. The parameters of the three-level surrounding rock shotcrete-anchor-mesh combined support are as follows: shotcrete thickness 250mm, concrete strength grade C30; cement mortar anchors are used, with anchor length 3.5-4.5m, arranged in a staggered pattern, and anchor spacing 1m; the steel mesh specification is ∅8 steel bars, and the mesh spacing is 150mm×150mm.

[0013] According to the present invention, a method for downward layered pressure control construction of an ultra-large fractured chamber with dual-access shaft coordinated ventilation is provided. The parameters of the four-level surrounding rock shotcrete and anchor mesh reinforced support are as follows: the total thickness of the shotcrete is 250mm, the concrete strength grade is C30, low prestressed fat roll anchors are used, the anchor length is 4.0-5.0m, arranged in a staggered pattern, and the anchor spacing is 1m; the anchor cable is made of ∅15.24mm steel strand, the anchor cable hole depth is greater than 10m and extends into the hard rock by no less than 1m, and the anchor cable is arranged in a 3.0m×3.0m diamond pattern; a double layer of ∅8 steel mesh is set, and the main reinforcement of the steel mesh is ∅22mm threaded steel.

[0014] According to the present invention, a method for downward layered pressure control construction of an ultra-large fractured chamber with coordinated ventilation of two chutes is provided. In step S2, both the low-level chute and the high-level chute are constructed by using a riser drilling rig.

[0015] According to the present invention, a method for constructing a super-large crushing chamber with dual chute coordinated ventilation and downward layered pressure control is provided. In step S7, the trackless slag removal equipment includes a loader and a mining truck. The slag is transferred through the low-level chute to the drainage level chamber and then transported to the spoil heap.

[0016] The present invention provides a method for constructing ultra-large fractured chambers with dual-well coordinated ventilation, which involves excavating the ultra-high chambers in uniform layers from top to bottom, releasing the high ground stress of the surrounding rock layer by layer, reducing stress concentration on the large-span free face, controlling the development of the loosened zone of the surrounding rock, and reducing the risk of collapse.

[0017] The system employs a division of labor between low-level and high-level chutes. The low-level chutes are responsible for air intake and slag transfer, while the high-level chutes are connected to a dedicated smoke exhaust system at the top of the chamber, forming a natural pressure difference air convection, which solves the problem of smoke accumulation at the top of the ultra-large chamber.

[0018] Control the exposure time of the surrounding rock, temporarily seal it after excavation, and follow up with permanent support layer by layer to prevent unsupported operation and inhibit weathering, deformation and loosening of the surrounding rock.

[0019] By utilizing the fixed-slope turnaround guide tunnel adapted for trackless equipment passage, rock drilling, blasting, slag removal and transportation, and staggered support construction operations can be carried out smoothly and without interference, achieving simultaneous improvement in safety and efficiency.

[0020] Support parameters are configured according to the classification of Grade III surrounding rock and Grade IV surrounding rock, so that simple support is adopted for stable surrounding rock and reinforced support is adopted for broken surrounding rock, giving consideration to both safety and economy. Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without any creative effort.

[0022] Figure 1 is a plan view of an extra-large underground chamber provided by the present invention; Figure 2 is a sectional view provided by the present invention.

[0023] Reference Numerals of the Drawings: 1. Low-level ore pass; 2. High-level ore pass. Detailed Description of the Embodiments

[0024] To make the purposes, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0025] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientation or positional relationships shown in the drawings, which are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance.

[0026] The following is combined with Figures 1-2 to describe the downward layered pressure-controlled construction method for an extra-large crushing chamber with double ore pass coordinated ventilation according to the present invention, wherein, Figure 1 the belt inclined shaft in the drawings is a supporting transportation inclined shaft for the chamber, and the construction method includes the following steps: S1. Conduct geological and rock classification surveys to determine the support system, complete surveying and setting out, and mark the outline of the chamber, the location of the ore pass, the direction of the guide tunnel, and the slope control line. Through preliminary geological surveys, understand the integrity of the surrounding rock and the in-situ stress conditions, and at the same time, conduct surveying and setting out to determine the spatial location of each project.

[0027] The above steps enable the matching of suitable support schemes in advance, ensuring the accuracy of subsequent construction positions and avoiding construction deviations.

[0028] S2. Construction connects the low-level chute 1 and the high-level chute 2. The low-level chute 1 serves as an air intake and slag transfer channel, while the high-level chute 2 serves as a smoke exhaust channel through the top of the circulation chamber, forming a differential pressure ventilation system with low-level air intake and high-level air exhaust.

[0029] In the above steps, the high and low level chute 1 is used to form a high pressure difference convection ventilation path, which specifically solves the problem of vortex retention of blasting smoke at the top of the ultra-large chamber, shortens the ventilation and smoke exhaust time after blasting, and improves the underground working environment.

[0030] S3. Construct a turnaround guide tunnel with a set slope from the bottom of the main transport inclined shaft to form a passage for trackless equipment.

[0031] In the above steps, a dedicated working channel is constructed by turning back the guide tunnel, enabling trackless equipment to directly reach the working surface, abandoning the traditional electric scraper for slag removal and high-altitude working platform, and reducing high-risk high-altitude working procedures.

[0032] S4. Divide the chamber into several uniform layers from top to bottom, and excavate layer by layer according to the principle of top to bottom and middle to sides. During excavation, a buffer protection layer of surrounding rock is reserved around the chamber. Excavate layer by layer from top to bottom, in conjunction with the surrounding rock buffer protection layer.

[0033] The above steps can release the high ground stress in the chamber layer by layer, inhibit the expansion of the loosened zone of the surrounding rock, reduce the disturbance of the original surrounding rock by blasting, and reduce the risk of roof collapse.

[0034] S5. After each layer of excavation is completed, temporary shotcrete is applied to seal the surrounding rock, followed by permanent support to control the time of exposure of the surrounding rock.

[0035] In the above steps, timely sealing and support of the surrounding rock after excavation can shorten the exposure time of the surrounding rock, prevent weathering and deformation of the surrounding rock, eliminate unsupported roof operations, and improve construction safety.

[0036] S6. Smooth blasting technology is used for drilling and blasting operations, and ventilation and smoke extraction are carried out after blasting.

[0037] In the above steps, smooth blasting is used to control the blasting quality, forced ventilation is provided after blasting to ensure the regularity of the excavation outline of the chamber, and blast fumes are removed in a timely manner to meet the safety conditions for personnel to enter and work.

[0038] S7. The slag is transported out via a trackless slag removal device through a return guide tunnel and then through a low-level chute 1.

[0039] The above steps achieve mechanized and efficient slag removal, with staggered operations of rock drilling, slag removal, and support processes to prevent interference between each other and improve slag removal efficiency.

[0040] In a specific embodiment of the present invention, in step S3, the cross-section of the reversing guide tunnel is a 4.0m×4.0m three-center arch cross-section, and the construction slope of the guide tunnel is 11°-15°. First, it is excavated towards the high-level chute 2, and after reaching the designated elevation, it is reversed and excavated towards the low-level chute 1 to achieve breakthrough.

[0041] In the above embodiments, the cross-sectional dimensions and slopes are adapted to the driving requirements of trackless equipment such as underground loaders and mining trucks. The turnaround tunneling method enables spatial connection between the two ends of the high-level chute 2 and the low-level chute 1, eliminating the need for secondary expansion and reshaping of the guide tunnel. This ensures smooth passage of trackless equipment, avoids congestion in the transportation channel, and guarantees continuous slag removal operations.

[0042] In a specific embodiment of the present invention, in step S4, the height of the chamber is divided into multiple uniform layers from top to bottom, with the excavation height of each layer controlled between 3.2m and 3.8m; each layer is first excavated with a small cross-section, and then widened to the designed outline, with a 0.5m surrounding rock buffer protection layer reserved around the chamber. More specifically, the total height of the chamber is divided into five uniform layers.

[0043] In the above embodiments, stress concentration is avoided due to excessively large open face during a single excavation. High ground stress is released gradually in layers. The buffer protective layer weakens the damage of the blast shock wave to the surrounding rock of the chamber, maintains the bearing capacity of the surrounding rock itself, and reduces the risk of collapse.

[0044] In a specific embodiment of the present invention, in step S5, after the excavation is completed, a temporary shotcrete with a thickness of 50 mm is applied to seal the surrounding rock, and the exposure time of the surrounding rock is controlled within 30 minutes.

[0045] In the above embodiment, after the layered excavation and blasting of slag are completed, a 50mm thick shotcrete layer is applied to seal the surrounding rock surface within a 30-minute time window. This quickly isolates the surrounding rock from the underground air, preventing the surrounding rock from weathering and peeling off due to water or air exposure, shortening the exposure time of the unsupported roof, solving the potential instability risk of the surrounding rock caused by the lag in traditional support methods, and providing safe working conditions for subsequent permanent support.

[0046] In a specific embodiment of the present invention, in step S6, a pneumatic rock drill is used to drill holes and cut grooves in a straight line with a peripheral hole spacing of 400-500mm. The blasting operation is carried out using reverse decoupled charge, hole plugging with stemming material, and non-electric micro-delay initiation.

[0047] In the above embodiments, the blasting vibration effect can be reduced, the damage of blasting to the unexcavated surrounding rock can be reduced, the smooth blasting effect is good, the chamber is formed in a regular manner, and the amount of subsequent trimming work is reduced.

[0048] In a specific embodiment of the present invention, in step S1, the geological surrounding rock classification includes Class III surrounding rock and Class IV surrounding rock. Class III surrounding rock is supported by a combination of shotcrete, anchor, and mesh; Class IV surrounding rock is supported by shotcrete, anchor, mesh, anchor cable, and steel grid.

[0049] In the above embodiments, the support system can be matched with the surrounding rock conditions. When the surrounding rock is good, excessive support is not required to save material costs. When the surrounding rock is broken, the support is strengthened to ensure the stability of the chamber, thus taking into account both construction safety and engineering economy.

[0050] In a specific embodiment of the present invention, the parameters for the three-level surrounding rock shotcrete-anchor-mesh combined support are as follows: the shotcrete thickness is 250mm and the concrete strength grade is C30; cement mortar anchors are used, with an anchor length of 3.5 to 4.5m, arranged in a staggered pattern, and the anchor spacing is 1m; the steel mesh specification is ∅8 steel bars, and the mesh spacing is 150mm×150mm.

[0051] In the above embodiments, the deformation of the surrounding rock is constrained by the synergistic effect of the sprayed layer, anchor bolts, and steel mesh, giving full play to the bearing capacity of the Class III surrounding rock itself, and controlling the support input while ensuring the stability of the chamber.

[0052] In a specific embodiment of the present invention, the parameters for the grade IV surrounding rock shotcrete and anchor mesh reinforced support are as follows: total shotcrete thickness 250mm, concrete strength grade C30, low prestressed fat roll anchors, anchor length 4.0-5.0m, staggered arrangement, anchor spacing 1m; anchor cables using ∅15.24mm steel strand, anchor hole depth greater than 10m and extending into hard rock no less than 1m, anchor cables arranged in a 3.0m×3.0m diamond pattern; double-layer ∅8 steel mesh is installed, the main reinforcement of the steel mesh is ∅22mm threaded steel.

[0053] In the above embodiments, the overall rigidity of the support is improved by steel grating, the anchor cables anchor the deep stable rock mass and the shallow support structure into a whole, and the double-layer steel mesh combined with shotcrete restrains the falling of broken surrounding rock, which can effectively control the large deformation of broken surrounding rock and ensure the safety of the chamber in long-term heavy-load service.

[0054] In a specific embodiment of the present invention, in step S2, both the low-level well 1 and the high-level well 2 are connected by a raise boring machine.

[0055] In the above embodiments, the ore pass can be completed quickly with the above settings, and the operators do not need to enter the ore pass for high-risk operations, which improves the safety of ore pass construction. The ore pass wall is formed in a regular shape, which ensures smooth subsequent air intake, smoke exhaust and slag removal and transportation.

[0056] In a specific embodiment of the present invention, in step S7, the trackless slag removal equipment includes a loader and a mining truck. The slag is transferred through the low-level chute 1 to the drainage tunnel and then transported to the spoil heap.

[0057] In the above embodiments, the use of the chute's own weight for slag removal and transportation reduces short-distance transport links, and the mechanized slag removal operation is highly efficient. The rock drilling, support, and slag removal processes are carried out in staggered shifts without interfering with each other, and the overall monthly excavation volume can reach 3000m³, shortening the overall construction period.

[0058] In summary, the downward layered pressure control construction method for ultra-large crushing chambers with dual chute coordinated ventilation provided by this invention forms natural convection pressure difference ventilation through a special ventilation structure with air intake and slag discharge in the low-level chute 1 and smoke exhaust at the top of the high-level chute 2, solving the problems of slag vortex retention at the top of ultra-large chambers, long ventilation cycles, and poor working environment.

[0059] Uniform layered unloading excavation is adopted, and the height of each layer is strictly controlled to release high ground stress layer by layer, inhibit the expansion of the loosened zone of the surrounding rock, reduce the risk of roof collapse and slab fall, and achieve controllable stress during the excavation of large-section chambers.

[0060] Using a sloped guide tunnel, it is compatible with trackless loaders and mine cars. The passage does not require secondary repair, the slag discharge path is minimized, and the traditional electric scraper transfer and high-altitude operation platform are abandoned, resulting in a smooth and congestion-free process.

[0061] A buffer layer of surrounding rock is reserved around the chamber, which, combined with smooth blasting technology, reduces the disturbance of the original surrounding rock caused by blasting. The chamber is well-formed, the surrounding rock is highly intact, and the long-term service life of the underground chamber is extended.

[0062] The support level is automatically matched according to the level 3 and level 4 fractured surrounding rock. The support is strengthened for weak surrounding rock and simplified for good surrounding rock, so as to avoid instability due to insufficient support and waste due to excessive support, and to take into account both construction safety and project economy.

[0063] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "method," "specific method," or "some methods," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or method is included in at least one embodiment or method of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or method. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or methods. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or methods described in this specification, as well as the features of different embodiments or methods.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for downward layered pressure control construction of an ultra-large fracture chamber with dual chute coordinated ventilation, characterized in that, include: S1. Conduct geological and rock classification investigation to determine the support system, complete surveying and setting out, and mark the outline of the chamber, the location of the chute, the direction of the guide tunnel and the slope control line; S2. Construction connects the low-level chute (1) and the high-level chute (2). The low-level chute (1) serves as an air intake and slag transfer channel, and the high-level chute (2) flows through the top of the chamber as a smoke exhaust channel, forming a differential pressure ventilation system with low-level air intake and high-level air exhaust. S3. Construct a turnaround guide tunnel with a set slope from the bottom of the main transport inclined shaft to form a passage for trackless equipment; S4. Divide the chamber into several uniform layers from top to bottom, and excavate layer by layer according to the principle of first top and then bottom, first middle and then both sides. During excavation, reserve a buffer protection layer of surrounding rock around the chamber. S5. After each layer of excavation is completed, temporary shotcrete is applied to seal the surrounding rock, followed by permanent support to control the time of exposure of the surrounding rock. S6. Smooth blasting technology shall be used for drilling and blasting operations, and ventilation and smoke exhaust shall be carried out after blasting. S7. The slag is transported out of the tunnel via a trackless slag removal device and then through a low-level chute (1).

2. The method for downward layered pressure control construction of an ultra-large fracture chamber with coordinated ventilation of dual chutes as described in claim 1, characterized in that, In step S3, the cross-section of the reversing guide tunnel is a 4.0m*4.0m three-center arch cross-section, and the construction slope of the guide tunnel is 11°-15°. First, it is excavated towards the high-level chute (2), and after reaching the designated elevation, it is reversed and excavated towards the low-level chute (1) to achieve breakthrough.

3. The method for downward layered pressure control construction of an ultra-large fracture chamber with coordinated ventilation of dual chutes as described in claim 1, characterized in that, In step S4, the height of the chamber is divided into multiple uniform layers from top to bottom, and the excavation height of a single layer is controlled between 3.2m and 3.8m. Each layer is first excavated with a small cross section, and then expanded to the design outline. A 0.5m buffer protection layer of surrounding rock is reserved around the chamber.

4. The method for downward layered pressure control construction of an ultra-large fracture chamber with dual-access shaft synergistic ventilation as described in claim 1, characterized in that, In step S5, after the excavation is completed, a temporary shotcrete layer with a thickness of 50mm is applied to seal the surrounding rock, and the time of exposure of the surrounding rock is controlled within 30 minutes.

5. The method for downward layered pressure control construction of an ultra-large fracture chamber with dual-access shaft synergistic ventilation as described in claim 1, characterized in that, In step S6, a pneumatic rock drill is used to drill holes and cut grooves in a straight line. The spacing between the holes is 400-500mm. The blasting operation is carried out using reverse decoupled charges, plugging of the holes with stemming material, and non-electric micro-delay initiation.

6. The method for downward layered pressure control construction of an ultra-large fracture chamber with dual-access shaft synergistic ventilation as described in claim 1, characterized in that, In step S1, the geological surrounding rock is classified into Class III and Class IV surrounding rock. Class III surrounding rock is supported by a combination of shotcrete, anchor, and mesh; Class IV surrounding rock is supported by shotcrete, anchor, mesh, anchor cables, and steel grid.

7. The method for downward layered pressure control construction of an ultra-large fracture chamber with coordinated ventilation of dual chutes as described in claim 6, characterized in that, The parameters for the three-level surrounding rock shotcrete-anchor-mesh combined support are as follows: shotcrete thickness 250mm, concrete strength grade C30; cement mortar anchors are used, with anchor length 3.5-4.5m, arranged in a staggered pattern, and anchor spacing 1m; the steel mesh specification is ∅8 steel bars, with mesh spacing of 150mm×150mm.

8. The method for downward layered pressure control construction of an ultra-large fracture chamber with dual-access shaft synergistic ventilation as described in claim 6, characterized in that, The parameters for the Class IV surrounding rock shotcrete and anchor mesh reinforced support are as follows: total shotcrete thickness 250mm, concrete strength grade C30, low prestressed fat roll anchors, anchor length 4.0-5.0m, staggered arrangement, anchor spacing 1m; anchor cables using ∅15.24mm steel strand, anchor hole depth greater than 10m and extending into hard rock no less than 1m, anchor cables arranged in a 3.0m×3.0m diamond pattern; double-layer ∅8 steel mesh is installed, the main reinforcement of the steel mesh is ∅22mm threaded steel.

9. The method for downward layered pressure control construction of an ultra-large fracture chamber with dual-access shaft synergistic ventilation as described in claim 1, characterized in that, In step S2, both the low-level chute (1) and the high-level chute (2) are constructed using a reverse drilling rig.

10. The method for downward layered pressure control construction of an ultra-large fracture chamber with dual-access shaft synergistic ventilation as described in claim 1, characterized in that, In step S7, the trackless slag removal equipment includes a loader and a mining truck. The slag is transported through the low-level chute (1) to the spillway and then transported to the spoil heap.

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