A method for constructing a long, deformable tunnel without ductwork for ventilation.

Abstract

This invention discloses a ductless tunnel ventilation construction method for long and deformable tunnels. The method involves excavating a parallel pilot tunnel for the main tunnel; excavating a transverse passage between the parallel pilot tunnel and the main tunnel; and excavating the main tunnel. During the excavation of the main tunnel, the parallel pilot tunnel serves as the fresh air intake channel, and the main tunnel serves as the waste air exhaust channel. The fresh air intake channel includes continuous multi-stage ventilation chambers. The outlet of the ventilation chamber furthest from the entrance of the fresh air intake channel delivers fresh air to each excavation face via a duct. When a ventilation section is in a severely deformed area where ductwork cannot be installed, the parallel pilot tunnel serves as the fresh air intake channel, and the main tunnel serves as the waste air exhaust channel. This divides the entire tunnel's ventilation system into multiple relatively independent ventilation chambers. Through the transition and adjustment functions of the ventilation chambers, uniform and efficient ventilation is achieved for each working face.

Description

Technical Field

[0001] This invention belongs to the field of tunnel ventilation technology, and in particular relates to a method for constructing a ductless tunnel ventilation system for long and deformable tunnels. Background Technology

[0002] Long and deformable tunnels refer to mountain tunnels that are long, deep, with weak surrounding rock, high ground stress, large deformation of surrounding rock (usually >30-50cm), fast deformation rate, and long duration. They are mostly located in complex geological areas in western my country and are the key control projects of major railway / highway projects.

[0003] In the construction of long and deformable tunnels, tunnel ventilation is a very common ventilation method. For large deformation tunnels (referring to tunnels where the surrounding rock clearance converges by more than 30cm, and the deformation continues to develop, with frequent cracking of the support structure / torsion of the steel frame / encroachment, requiring special design and control), the deformation of the surrounding rock causes damage to the original ventilation pipes and makes it difficult to install new ventilation pipes, resulting in great difficulty in tunnel ventilation, serious pollution of the working environment, threats to the health and safety of construction personnel, and reduced construction efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a ductless ventilation construction method for long and deformable tunnels, which solves the problem of ventilation difficulties in long and deformable tunnels by establishing an open continuous ventilation chamber.

[0005] This invention adopts the following technical solution: a method for constructing a ductless ventilation system for long, deformable tunnels, comprising the following steps: Excavation of a parallel pilot tunnel for the main tunnel; Excavate a transverse passage between the parallel pilot tunnel and the main tunnel; Excavation of the main tunnel section; During the excavation of the main tunnel, parallel pilot tunnels are used as fresh air intake channels, and the main tunnel is used as waste air exhaust channels. The fresh air intake channel consists of a series of multi-stage air chambers. The outlet of the air chamber furthest from the entrance of the fresh air intake channel delivers fresh air to each level of the excavation face through air ducts.

[0006] The beneficial effects of this invention are: when a ventilation section is in a severely deformed section and it is impossible to lay air ducts, the parallel guide tunnel is used as the fresh air introduction channel and the main tunnel of the tunnel is used as the sewage air discharge channel. The ventilation system of the entire tunnel is divided into multiple relatively independent air chambers. Through the transition and adjustment function of the air chambers, uniform and efficient ventilation of each working face is achieved. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the ventilation status when the 8# horizontal passage section is not completed in this embodiment of the invention; Figure 2 This is a schematic diagram of the ventilation status after the completion of the 8#, 9#, 10#, and 11# horizontal channels in an embodiment of the present invention. Detailed Implementation

[0008] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0009] To address the ventilation challenges of long, deformable tunnels, this invention employs a combination of "continuous air chamber segmented relay" and "ductless open-tunnel ventilation." The ductless open-tunnel ventilation technology uses the tunnel body (tunnel deck and main tunnel) as the air duct, constructing a unidirectional flow ventilation network through wall separation and main fan pressurization, achieving efficient ventilation without the need for traditional ductwork. Continuous air chamber ventilation involves setting up continuous air chamber structures within the tunnel, dividing the entire tunnel's ventilation system into multiple relatively independent ventilation zones. Through the transition and adjustment functions of the air chambers, uniform and efficient ventilation is achieved across all work surfaces, ensuring the effectiveness and reliability of the ventilation system.

[0010] The core design of this invention, a ductless open continuous ventilation chamber for large deformation tunnels, lies in "ductless operation, open ventilation duct, continuous ventilation chamber, and forced ventilation." Taking existing tunnel ventilation construction projects as an example, the specific technical steps are as follows: (1) Ventilation system planning: The tunnel pilot tunnel (parallel pilot tunnel) is selected as the main channel for fresh air introduction, and the main tunnel that has been completed is used as the channel for exhausting polluted air. The pilot tunnel body and the cross passage are used to construct a multi-level continuous air chamber consisting of a primary air chamber and a secondary air chamber. The spacing between the air chambers is determined according to the tunnel ventilation distance and the distribution of the working face. The secondary air chamber is located in a position where vehicles do not pass, and the front of the fan can be sealed off. In this way, the fresh air can be smoothly injected into the underpass air chamber (secondary air chamber) through the pressure increase of the air outlet and the negative pressure of the air intake of the underpass section, effectively determining the location of the secondary air chamber.

[0011] It should be noted that the height of the parallel pilot tunnel is lower than the height of the main tunnel. When the parallel pilot tunnel passes from one side of the main tunnel to the other, the cross passage does not intersect with the main tunnel.

[0012] (2) Sealing wall construction: a sealed sealing wall is built at the boundary of the ventilation chamber, the entrance of the cross passage and the tunnel connection surface. The sealing wall adopts a 50cm thick brick structure or concrete structure. The gap between the sealing wall and the tunnel rock wall is sealed with polyurethane foam. The air leakage rate is controlled within 3%. The sealing wall is reserved with adjustable air vents with a size of Φ1.6m-Φ2.0m.

[0013] (3) Layout of main fan and relay fan: Two or more high-power axial flow main fans are installed at the entrance of the primary air chamber. The power of the main fan is not less than 2×200kW. Relay fans are set in the secondary air chamber. The power of the relay fans is configured as 2×75kW-2×110kW according to the air volume requirements of the air chamber zone. The fans are fixed by steel brackets, and the brackets are anchored to the ground with expansion bolts.

[0014] (4) Ventilation system commissioning: Start the main fan and relay fan, use the smoke test method to verify the airflow direction, and ensure that a unidirectional flow organization of "horizontal guide air intake - air chamber diversion - working face air use - main tunnel or horizontal guide exhaust" is formed. Adjust the sealing wall air outlet valve and fan speed to ensure that the wind speed on each working face is not less than 0.2m / s, and the wind speed on the working face of the high gas tunnel is not less than 0.5m / s.

[0015] (5) Operation and maintenance: Real-time monitoring of gas concentration, temperature and wind speed parameters at each work site. When the gas concentration exceeds 0.5%, the fan air volume is automatically increased. When the temperature exceeds 28℃, the auxiliary cooling equipment is started. The sealing performance of the wall and the operating status of the fan are checked regularly, and the ventilation parameters are dynamically adjusted.

[0016] (1) Selection of air duct: The tunnel guide is selected as the main channel for fresh air introduction. The cross-sectional dimensions of the guide are not less than 7m (width) × 6.5m (height) to ensure that the dual needs of ventilation and vehicle transportation are met. The main tunnel that has been completed is used as the channel for exhausting polluted air. The cross passage between the guide and the main tunnel (the main tunnel) is used to achieve airflow diversion and air supply to the working face. (2) Construction of air chambers: Multi-level continuous air chambers are constructed. The first-level air chamber is constructed using the tunnel body of the cross passage section 1#-9# of the guide. The length is determined according to the ventilation distance and is 4000m-6000m. The second-level air chamber is constructed using the cross passage section 12# of the guide under the main tunnel. The air chamber is divided into sections by partitions or sealing walls to form relatively independent ventilation areas and achieve segmented relay ventilation.

[0017] Key component design and construction: (1) Sealing wall design: The sealing wall adopts a 50cm thick brick structure or C25 concrete structure, and a 10cm thick C20 concrete pad is laid on the foundation to ensure stable bearing. The gap between the sealing wall and the tunnel rock wall is filled and sealed with polyurethane foam, and the air leakage rate is controlled within 3%. The sealing wall is reserved with Φ1.6m-Φ2.0m adjustable air outlets, equipped with manual or electric regulating valves for precise control of air volume distribution. (2) Fan selection and layout: Two or more high-power axial flow main fans are installed at the entrance of the first-level air chamber. The power of the main fan is selected according to the ventilation requirements, from 2×200kW to 2×355kW. The 2×355kW model is preferred for high-gas tunnels to provide initial air supply power. Relay fans are set in each level of air chamber, with a power of 2×75kW-2×110kW, to achieve secondary pressurization and precise distribution of air volume. The fans are fixed by I-beam I20a steel brackets, and the brackets are anchored to the ground with expansion bolts to prevent displacement due to vibration during operation.

[0018] Ventilation system operation and control: (1) Airflow organization: After starting the main fan and the relay fan, fresh air enters the primary air chamber from the horizontal inlet, is pressurized by the main fan and sent to the secondary air chamber, and then distributed to each working face through the relay fan and the adjustable air vents of the sealing wall. Sewage flows into the main tunnel through the cross passage and is finally discharged from the main tunnel outlet, forming a unidirectional flow system of "horizontal inlet air intake - air chamber distribution - working face air supply - main tunnel exhaust". (2) Parameter control: By adjusting the valves of the sealing wall air vents and the fan speed, the wind speed of each working face is kept stable at 0.2m / s-6m / s, and the wind speed of the working face in the high gas tunnel is not less than 0.5m / s; the total air supply is determined according to the number of working faces, and the air supply is not less than 15000m when multiple working faces are constructed simultaneously. 3 / min.

[0019] Operation, maintenance and safety assurance: (1) Real-time monitoring: Anemometers, gas detectors and temperature sensors are installed in the air intake area, working face and exhaust area respectively. The monitoring data is transmitted to the monitoring center in real time. When the gas concentration exceeds 0.5%, an alarm is automatically triggered and the fan volume is increased. When it exceeds 1.0%, the machine is immediately stopped and personnel are evacuated. When the temperature exceeds 28℃, the phase change refrigerator and water curtain are automatically started. (2) Daily maintenance: The sealing performance of the sealing wall is checked every week. Cracks and leaks are repaired with cement mortar in time. The dust on the fan blades is cleaned every month and the motor operation status is checked. The number of standby fans is not less than 1 / 2 of the number of operating fans. Emergency power supply is provided to ensure quick switching when the fan fails. (3) Construction coordination: The sealing wall construction and fan installation avoid the peak transportation period of the main tunnel and adopt segmented and block operation. The large deformation section adopts a one-way design. The ventilation area and transportation channel are separated by the middle partition railing. Special personnel are arranged to guide traffic to avoid mutual interference between transportation and ventilation.

[0020] Specifically, this invention discloses a ductless tunnel ventilation construction method for long and deformable tunnels, comprising the following steps: excavating a parallel pilot tunnel for the main tunnel; excavating a transverse passage between the parallel pilot tunnel and the main tunnel; and excavating the main tunnel. During the excavation of the main tunnel, the parallel pilot tunnel serves as the fresh air intake channel, and the main tunnel serves as the waste air exhaust channel. The fresh air intake channel includes a series of multi-stage ventilation chambers, and the outlet of the ventilation chamber furthest from the entrance of the fresh air intake channel delivers fresh air to each level of the excavation face via a duct.

[0021] When a ventilation section is in a severely deformed area and it is impossible to lay air ducts, a parallel pilot tunnel is used as the fresh air introduction channel, and the main tunnel of the through tunnel is used as the sewage air discharge channel. The ventilation system of the entire tunnel is divided into multiple relatively independent air chambers. Through the transition and adjustment function of the air chambers, uniform and efficient ventilation is achieved for each working face.

[0022] Step 1: Excavate the parallel pilot tunnel for the main tunnel.

[0023] A parallel pilot tunnel refers to an auxiliary tunnel excavated roughly parallel to the main tunnel, located to the side of it, serving as the main channel for introducing fresh air into the entire ventilation system. The cross-sectional dimensions of the parallel pilot tunnel are determined based on ventilation volume and transportation requirements, for example, a cross-sectional area of ​​not less than 45.5 square meters (7m wide × 6.5m high) to meet the needs of transporting large volumes of air at low velocities. This parallel pilot tunnel is excavated using conventional tunneling techniques such as drill-and-blast or TBM methods. Its function is to replace traditional long-distance ventilation ducts, utilizing the stable tunnel space created by the tunnel itself to guide fresh air into the construction area. The parallel pilot tunnel is connected to the main tunnel via subsequently excavated transverse passages, together forming the basic framework of a multi-stage continuous ventilation system.

[0024] Step 2: Excavate the transverse passage between the parallel pilot tunnel and the main tunnel.

[0025] A cross passage refers to a transverse connecting channel between the parallel pilot tunnel and the main tunnel, used to achieve airflow zoning and air supply conversion at the work face. Cross passages are excavated between the parallel pilot tunnel and the main tunnel according to the tunnel construction organization design at predetermined intervals (e.g., every 400 to 600 meters). The cross passage serves as the entrance for fresh air from the parallel pilot tunnel into each construction zone, and also as the necessary path for stale air to exit from the work face. During excavation, the cross passage's cross section must meet the requirements for smooth airflow and form a connected network structure with the parallel pilot tunnel and the main tunnel, providing physical connections for constructing relatively independent ventilation zones.

[0026] Step 3: Excavate the main tunnel.

[0027] The main tunnel section can refer to the main driving or passageway portion of the tunnel. In this method, it serves as a stale air exhaust channel after its completion. The excavation of the main tunnel section is based on the previously established network of parallel pilot tunnels and cross passages. As the main tunnel continues to advance, exhaust channels are formed using the completed sections. This step allows fresh air to reach the excavation face via the parallel pilot tunnels and cross passages, while stale air generated during operations flows along the main tunnel towards the outlet, thus creating a unidirectional airflow path of pilot tunnel intake and main tunnel exhaust, effectively preventing short-circuit circulation between fresh and stale air.

[0028] During the excavation of the main tunnel, parallel pilot tunnels serve as fresh air intake channels, while the main tunnel serves as waste air exhaust channels. The fresh air intake channels include continuous multi-stage ventilation chambers, with the ventilation chamber outlet furthest from the entrance of the fresh air intake channel delivering fresh air to each level of the excavation face via ductwork.

[0029] A continuous multi-stage ventilation system refers to multiple independent ventilation spaces connected in series, separated by different sections of parallel guide tunnels and transverse passages. For example... Figure 1As shown, the connection and layout of the parallel pilot tunnel, the main tunnel, and the transverse passage are illustrated in detail. Specifically, the fresh air introduction channel is composed of parallel pilot tunnels, which are internally divided into multiple continuous air chambers, such as primary and secondary air chambers, by setting up sealing walls (such as brick or concrete structures). Each air chamber forms a relatively independent ventilation area, and the outlet of the previous air chamber is the inlet of the next air chamber, realizing the successive relay transmission of air pressure. At the outlet of the air chamber farthest from the inlet of the fresh air introduction channel, a short-distance air duct (red line in the figure) is connected. This air duct directly and accurately delivers the fresh air, which has been pressure-stabilized by multiple air chambers, to the current excavation face. For example, when the tunnel excavation length reaches 5000 meters, multiple air chambers can be built. The first 4000 meters utilize the parallel pilot tunnel as a ductless ventilation channel, and only the outlet of the last 1000 meters is ducted to the working face. This combination of ductless tunnels and short end ducts can significantly reduce wind resistance loss in long-distance ventilation, avoid the risk of damage to long ducts in large deformation sections, and ensure air supply to the farthest working face.

[0030] By excavating parallel pilot tunnels as fresh air intake channels and utilizing the main tunnel as a stale air exhaust channel, and constructing continuous multi-stage ventilation chambers within the fresh air intake channels, efficient ventilation has been achieved in long and deformable tunnels. The combination of parallel pilot tunnels and transverse channels transforms traditional long-distance duct ventilation into tunnel-style ventilation utilizing the tunnel's internal space, using only short ducts at the ends. This effectively solves the technical challenge of long ducts being impossible to install or frequently damaged due to large deformations of the surrounding rock. The multi-stage ventilation chambers create a segmented, relay-style ventilation mechanism, using sealing walls to separate independent ventilation areas, reducing air leakage and improving air pressure transmission efficiency. This ensures that fresh air is delivered evenly and stably to each level of the excavation face, while stale air is smoothly exhausted through the main tunnel, significantly improving the working environment within the tunnel and enhancing construction safety and efficiency.

[0031] In one embodiment, when the excavation length of the main tunnel is less than a first preset length, no ventilation chamber is built, and fresh air is directly supplied to the excavation faces of each level through parallel pilot tunnels and cross passages; wherein, the first preset length is the length between the far end of the first-level ventilation chamber and the entrance of the parallel pilot tunnel; the far end is the end away from the entrance of the parallel pilot tunnel.

[0032] The first preset length refers to the critical distance threshold between the far end of the primary ventilation chamber and the entrance of the parallel pilot tunnel. This length is calculated based on the effective air supply radius and wind resistance loss of the ventilation system, and is used to define whether an independent ventilation chamber structure needs to be constructed. The far end is defined as the end furthest from the entrance of the parallel pilot tunnel, that is, the end position of the ventilation chamber structure in the tunnel extension direction. Not constructing a ventilation chamber can mean that in the early stage of tunnel excavation, due to the short extension distance of the main tunnel, the fresh air entering from the entrance of the parallel pilot tunnel has sufficient air pressure and volume to overcome the resistance along the way and directly reach the working face. Therefore, there is no need to build a sealing wall to divide an independent ventilation area, thus omitting the ventilation chamber construction process. The parallel pilot tunnel serves as the main channel for fresh air introduction, and the cross passage serves as a branch channel connecting the main channel and the working face. Together, they form an open tunnel-type ventilation network. For example, when the first preset length is set to 2000 meters, if the current excavation length of the main tunnel is only 800 meters, the system determines that there is no need to start the ventilation chamber construction process. The fresh air flows directly through the parallel pilot tunnel and is naturally distributed to each excavation face through the excavated cross passage.

[0033] Under short tunneling length conditions, the fresh air intake channel is not equipped with any sealing walls or ventilation shafts. After entering from the parallel pilot tunnel entrance, the airflow smoothly passes through the cross passage to the excavation face. This step aims to utilize the tunnel's own roadway space characteristics to simplify the ventilation system architecture in the early stages of tunneling, avoiding premature investment in ventilation shaft construction resources. The direct connection between the parallel pilot tunnel and the cross passage significantly reduces the complexity and material costs of early-stage construction, while simultaneously improving the ventilation system's response speed to short-distance tunneling operations.

[0034] A primary ventilation unit refers to the first-level independent ventilation unit in a ventilation system that is closest to the fresh air source. Its distal position determines the maximum effective ventilation distance it can cover. The first preset length is determined based on fluid dynamics simulations and engineering experience data, taking into account fan power, tunnel cross-sectional dimensions, and expected air leakage rate. It is set as a fixed or dynamically adjusted value. When the actual excavation length does not reach this length, it means that the energy loss of the airflow within the tunnel is still within a controllable range, and there is no need for pressurization or rectification through sealing walls. For example, if the planned length of the primary ventilation unit is 3000 meters, then the first preset length is 3000 meters. As long as the excavation front of the main tunnel does not exceed this distance marker, the no-ventilation-unit mode is maintained. This feature, closely coordinated with the aforementioned operation of not establishing ventilation units, provides a clear quantitative basis for judgment, ensuring that the construction team can accurately identify the timing of ventilation mode switching. By clearly defining the first preset length and its geometric meaning, ambiguities in the construction process are eliminated, ensuring the scientific and accurate switching of ventilation strategies, thereby maximizing construction efficiency while ensuring air quality at the work face.

[0035] By determining whether the excavation length of the main tunnel is less than a first preset length, the construction strategy of the ventilation system is dynamically adjusted. Based on this, when the excavation length is in the initial, shorter stage, fresh air is directly delivered using the natural tunnel space formed by parallel pilot tunnels and cross passages, eliminating the cumbersome procedures of building sealing walls and dividing ventilation chambers. This design not only saves on building materials and labor costs but also avoids potential interference from surrounding rock deformation caused by prematurely constructing rigid ventilation chamber structures. Furthermore, the open ventilation path reduces wind resistance, resulting in lower fan energy consumption and higher ventilation efficiency over short distances. Ultimately, this method achieves adaptive adjustment of the ventilation mode according to the project progress, meeting the ventilation needs of short-term excavation while reserving a technical interface for transitioning to a multi-stage ventilation chamber mode during subsequent long-distance excavation, effectively solving the problem of optimizing ventilation resource allocation at different construction stages in long and deformable tunnels.

[0036] In one embodiment, the primary ventilation chamber is connected to the parallel pilot tunnel inlet via a duct. The primary ventilation chamber can be defined as the first-level ventilation zone closest to the parallel pilot tunnel inlet in the fresh air intake channel, with its far end defined as the end furthest from the parallel pilot tunnel inlet. The duct is a flexible or rigid air-guiding component used to connect the parallel pilot tunnel inlet to a specific location within the primary ventilation chamber. Its function is to serve as a temporary or transitional channel for fresh air delivery when the main tunnel excavation length has not yet reached the point where a complete ventilation chamber structure can be established, or before the primary ventilation chamber is fully enclosed. The specific specifications of the duct can be determined based on the airflow of the main fan at the parallel pilot tunnel inlet and the design volume of the primary ventilation chamber. It is typically made of high-strength, flame-retardant materials to withstand the complex environment within the tunnel.

[0037] This step aims to address the technical challenges of unstable or inefficient fresh air introduction paths during the initial construction of the ventilation system or under special operating conditions. Based on the aforementioned fresh air resources obtained from the parallel pilot tunnel and its inlet, the construction system deploys ductwork as a forced airflow medium to precisely deliver fresh air from the parallel pilot tunnel inlet to the primary ventilation chamber. The execution is carried out by the tunnel ventilation construction team or automated ductwork equipment. Specific operations include measuring the distance from the parallel pilot tunnel inlet to the predetermined location of the primary ventilation chamber, selecting ductwork of appropriate length, and fixing both ends to the fan outlet at the inlet and the reserved interface inside the primary ventilation chamber, respectively. This results in a forced ventilation link independent of the natural tunnel of the parallel pilot tunnel. This provides a stable source of fresh air for the subsequent formal establishment of a multi-stage continuous ventilation system, effectively avoiding fresh air leakage due to incomplete ventilation chamber closure, and significantly improving the reliability and continuity of the ventilation system during the transition period.

[0038] By connecting the primary ventilation chamber with the entrance of the parallel pilot tunnel using ductwork, a seamless connection of the ventilation system during dynamic construction is achieved. Furthermore, the ductwork serves as a temporary fresh air delivery carrier, complementing the natural main airflow of the parallel pilot tunnel: when the primary ventilation chamber is not yet fully enclosed, the ductwork undertakes the primary directional air delivery function, preventing the disorderly diffusion of fresh air in the long parallel pilot tunnel; and once the primary ventilation chamber is fully constructed, the ductwork can serve as an auxiliary pressurization channel or a backup channel, further enhancing the airflow stability within the ventilation chamber. This hybrid approach of tunnel + ductwork not only ensures the continuity of fresh air introduction during changes in tunneling length but also reduces wind resistance loss through the constraint effect of the ductwork, allowing fresh air to reach each level of the excavation face more efficiently. Ultimately, this synergistic cooperation ensures that the ventilation system maintains efficient operation regardless of the tunnel's excavation stage, effectively solving the technical challenges of ventilation difficulties and insufficient airflow during the construction transition period of long and deformable tunnels.

[0039] In one embodiment, when the excavation length of the main tunnel is greater than or equal to a first preset length and less than a Nth preset length, an N-1 level ventilation shaft is established; where N is the level of the ventilation shaft and is a positive integer; the Nth preset length is the length between the far end of the Nth level ventilation shaft and the entrance of the parallel pilot tunnel.

[0040] This step aims to dynamically adjust the structural scale of the ventilation system based on the actual excavation progress of the main tunnel, in order to solve the problem of insufficient air supply capacity of a single ventilation mode during long-distance excavation. Specifically, as the excavation face advances, the ventilation resistance inside the tunnel gradually increases. When the excavation length exceeds the limit of direct air supply from the parallel pilot tunnel and cross passage (i.e., the first preset length), the construction system activates a graded ventilation system. At this point, the system no longer maintains a no-ventilation-storage state, but instead determines the total number of ventilation levels N to be constructed based on the current excavation length range, and then establishes an N-1 level ventilation structure. For example, if the first preset length is set to 2000 meters and the second preset length (corresponding to N=3) is 5000 meters, when the main tunnel reaches 3500 meters, since this length is greater than 2000 meters but less than 5000 meters, it is determined that a second level of ventilation (i.e., N-1=2) needs to be established. At this time, two continuous and independent ventilation areas are formed between the parallel pilot tunnel and the main tunnel using the already connected cross passage and the masonry sealing wall.

[0041] N represents the maximum theoretical level of the ventilation system design. It is a positive integer variable that is pre-set according to the engineering plan or dynamically adjusted according to geological conditions, used to define the critical points of different ventilation stages. The Nth preset length is the spatial limit indicator that triggers the establishment of the Nth level ventilation system. Its physical meaning is the cumulative distance from the parallel pilot tunnel entrance along the ventilation path to the farthest end of the Nth level ventilation system (i.e., the end furthest from the entrance). The determination of this parameter depends on the fluid dynamics calculation results such as fan power, duct diameter, tunnel cross-sectional dimensions, and the minimum allowable end wind speed. Specifically, the setting of the Nth preset length ensures that the previous level (N-1 level) ventilation system can still maintain effective ventilation before the Nth level ventilation system is fully built and put into operation, thus achieving seamless connection of the construction process. For example, when N is 3, the third preset length may be set to 6000 meters, meaning that the system is configured with a level 2 ventilation system only when the tunneling length is close to but does not exceed 6000 meters; once the tunneling length reaches or exceeds this threshold, a level 3 ventilation system needs to be upgraded. This length definition method clearly establishes the mapping relationship between the number of ventilation chamber levels and the tunnel mileage, providing a clear and executable standard for the expansion of the ventilation system. With precise control over the Nth preset length, the construction team can plan the construction location of the sealing wall and the layout of adjustable air vents in advance, ensuring that each ventilation chamber forms a relatively independent ventilation area upon activation, thereby achieving precise distribution of air pressure and air volume.

[0042] By combining the technical feature of dynamically establishing N-1 level ventilation chambers based on the tunneling length with the technical feature of limiting the number of ventilation chamber levels N and the Nth preset length, an adaptive ventilation construction logic for long tunnels was formed. Based on this, the natural tunnel space formed by parallel pilot tunnels and cross passages, combined with the partitioning effect of sealing walls, divides the originally connected huge space into multiple independent ventilation chambers with reasonable pressure gradients. Furthermore, by setting strict first and Nth preset lengths as switching thresholds, the timing of ventilation system expansion is ensured to be highly matched with the tunnel excavation progress. This avoids resource waste and construction interference caused by prematurely constructing multiple levels of ventilation chambers, and also prevents ventilation dead zones and safety hazards caused by delayed chamber construction. Ultimately, this tiered and progressively increasing chamber construction method ensures that fresh air enters from the parallel pilot tunnel entrance, is relayed through each level of ventilation chamber, and finally reaches the furthest excavation face with sufficient wind speed and volume, while simultaneously expelling polluted air smoothly through the main tunnel, significantly improving ventilation efficiency and safety in long-distance tunnel construction.

[0043] In one embodiment, when the excavation of the section corresponding to the cross passage is completed, a sealing wall is constructed within the cross passage. The cross passage can refer to a connecting channel between the parallel pilot tunnel and the main tunnel, serving as a critical path for fresh air to enter the various working faces of the main tunnel from the parallel pilot tunnel. The completion of section excavation can mean that the specific tunnel section served by the cross passage has completed initial support or secondary lining construction, and the cross passage is no longer needed as the main fresh air inlet. At this point, keeping the cross passage open would cause a short-circuit leak in the fresh air flow through the completed area, preventing it from effectively reaching the working face ahead and resulting in reduced ventilation efficiency.

[0044] A sealing wall can refer to a barrier structure built inside a cross passageway to cut off the connection between the completed section of the cross passageway and the main ventilation system, thereby changing the airflow path and forcing fresh air to flow towards the subsequent work areas that still require air supply. The timing of the sealing wall construction is strictly controlled after the excavation of the corresponding section is completed to ensure that the cross passageway can function normally as a ventilation guide during construction, and immediately transforms into an isolation barrier after its function is completed.

[0045] For example, during tunnel construction, once the excavation and support work for the main tunnel section from K10+000 to K10+200, corresponding to the No. 8 cross passage, is completed, the construction workers immediately stop using the cross passage for active ventilation and begin the sealing wall construction process. This is achieved by constructing a wall on the side of the No. 8 cross passage near the parallel pilot tunnel or in the middle of the cross passage, thus sealing the passage.

[0046] This step aims to address air leakage and airflow short-circuiting issues caused by the completion of partial sections of the ventilation network by dynamically adjusting its topology. Based on the aforementioned information regarding the completion status of excavated sections, the construction team performs masonry work within the cross passages, thereby creating physical isolation barriers. This significantly improves the airflow utilization rate of the ventilation system, ensuring that limited air sources can be concentrated to supply the high-demand excavation face ahead, effectively avoiding ineffective air loss, and guaranteeing air quality and safety in the construction environment of long and deformable tunnels.

[0047] In one embodiment, multi-stage ventilation chambers are partitioned by sealing walls to form relatively independent ventilation zones. A sealing wall is a physical isolation structure built at the connection between adjacent ventilation chambers or at key nodes within the same ventilation chamber. Its function is to divide the continuous tunnel space into multiple relatively independent pressure zones. The sealing wall is specifically located between the far end of the preceding ventilation chamber and the near end of the following ventilation chamber, or at the boundary between different cross passages corresponding to different sections. The sealing wall is formed by constructing brick or concrete structures between the tunnel walls, arch, and floor slab. The gap between the sealing wall and the tunnel walls is sealed using materials such as foaming agents to ensure that the air leakage rate is less than a preset air leakage rate threshold (e.g., controlled within 3%).

[0048] A relatively independent ventilation zone can refer to a closed or semi-closed space enclosed by a sealing wall, possessing a specific wind pressure gradient and airflow organization pattern. Each ventilation zone corresponds to the air supply needs of one or more excavation faces, and a specific positive pressure state is maintained within the zone through relay fans. The extent of the ventilation zone is determined based on the number N of the ventilation chambers and the distribution of the cross passages. As the tunneling length increases, new ventilation zones are dynamically expanded by adding sealing walls. For example, when the tunnel has been excavated to the Nth preset length, a new sealing wall is constructed between the N-1th level ventilation chamber and the Nth level ventilation chamber, thus defining the Nth relatively independent ventilation zone. The wind speed within this zone can be independently controlled to no less than 0.2 m / s (no less than 0.5 m / s for high-gas tunnels) without affecting the wind speed setting of the upstream ventilation chamber. This achieves segmented management and precise control of ventilation in long-distance tunnels.

[0049] For example, during tunnel construction, by constructing sealing walls at cross passages #8, #9, and #10, three independent ventilation zones were created. Even if severe surrounding rock deformation occurred in a section, preventing the installation of ventilation ducts, each independent zone could still maintain normal ventilation using the space within the tunnel itself, avoiding the paralyzing effect of localized disasters on the entire ventilation system. Through the independent zoning and relay air supply of multi-level ventilation chambers, wind resistance losses during long-distance ventilation were significantly reduced, and the air volume utilization rate was increased to over 90%, effectively ensuring the construction safety and operational efficiency of deeply buried tunnels with large deformations.

[0050] By using sealed walls to partition the multi-stage ventilation chambers, modular, relatively independent ventilation areas are constructed. These sealed walls not only serve as physical barriers but also, in conjunction with pre-installed adjustable vents, enable graded control of air pressure and on-demand distribution of airflow. The segmented isolation of the fresh air intake channels through these sealed walls prevents air pressure interference between adjacent ventilation chambers, ensuring each chamber provides a stable supply of fresh air to the excavation face within its service area. Simultaneously, this independent partitioning structure gives the ventilation system strong adaptability. When a section encounters large deformations in the surrounding rock or sudden emergencies, the impact can be limited to a localized area by closing or adjusting the vents in the corresponding sealed walls, preventing contaminated air from flowing back into other work areas. Ultimately, through the synergistic effect of sealed wall partitioning and tunnel-style ventilation, the technical challenges of traditional long-distance duct ventilation under large deformation geological conditions—such as susceptibility to damage, high leakage rates, and uneven air supply—are solved, achieving efficient, safe, and low-cost ventilation for tunnel construction.

[0051] In one embodiment, the sealing wall adopts a brick or concrete structure, the gap between the sealing wall and the tunnel rock wall is sealed, the air leakage rate is less than the preset air leakage rate threshold, and the sealing wall is reserved with adjustable air vents.

[0052] Brick masonry structures refer to walls constructed using standard bricks and high-strength mortar, while concrete structures refer to monolithic walls formed by casting C25 or higher grade concrete using formwork. As a key component separating multi-stage ventilation chambers, the sealing wall's function is to withstand the wind pressure difference within the tunnel and prevent the mixing of fresh and polluted air, ensuring the independence of each ventilation zone. The structural form of the sealing wall can be selected based on the stability of the surrounding rock and ease of construction. For example, in sections with relatively stable surrounding rock and requiring rapid construction, a 50cm thick brick masonry structure can be used; while in sections with complex geological conditions and extremely high structural strength requirements, a C25 concrete structure is used.

[0053] Tunnel wall refers to the natural or supported contour surface formed after tunnel excavation, while gap sealing refers to the filling of gaps at the contact point between the sealing wall edge and the tunnel wall. The purpose of gap sealing between the sealing wall and the tunnel wall is to eliminate voids caused by irregular tunnel cross-sections or excavation errors, preventing fresh air from leaking directly into the contaminated air passage without passing through the working face. Sealing can be achieved by spraying polyurethane foam, injecting cement grout, or laying flexible sealing gaskets. The preset leakage rate threshold is usually set below 3% to ensure ventilation efficiency. Specifically, after the sealing wall is constructed, inspectors will conduct a comprehensive inspection of the junction between the sealing wall and the tunnel wall. If any tiny gaps are found, they will be immediately filled with high-pressure grouting or foaming materials until a dense sealing layer is formed. This sealing measure, used in conjunction with the main structure of the sealing wall, can significantly reduce ineffective air leakage in the system, allowing most of the fresh air to flow through each level of the excavation face along a predetermined path, thus ensuring the air volume utilization rate during long-distance ventilation.

[0054] Adjustable air vents are ventilation openings with adjustable diameters pre-installed during the construction of sealed walls. Their function is to serve as control nodes connecting adjacent air chambers or distributing airflow to specific work areas. Adjustable air vents can dynamically adjust their opening area according to the airflow requirements of different construction stages, enabling precise control of wind speed and direction in each zone. The diameter of adjustable air vents is typically set between 1.6m and 2.0m, and they are equipped with sliding baffles or louver structures.

[0055] By employing brick or concrete structures to construct the sealing walls, combined with gap sealing technology and adjustable vent designs, a highly airtight ventilation isolation system with flexible adjustment capabilities is formed. The selection of high-strength materials ensures the durability of the sealing walls under complex geological conditions, while strict gap sealing treatment controls the air leakage rate to an extremely low level, effectively solving the problem of insufficient airflow at distant points caused by severe air leakage in traditional ventilation. Furthermore, the reserved adjustable vents further endow the system with dynamic balancing capabilities, allowing for precise distribution of fresh air according to the actual needs of each zone. This synergistic combination of structure and function not only significantly improves the ventilation efficiency of long and deformable tunnels in ductless mode but also significantly reduces the safety risks caused by poor ventilation, adapting to the unique challenges of variable working conditions and limited space in the construction of large deformation tunnels.

[0056] Taking the Xingshan East Tunnel as an example, the specific implementation of the present invention will be described in detail below: Project Background: The Xingdong Tunnel is 16,883.5m long with a maximum burial depth of 1,256m. It is a high-gas, large-deformation tunnel, equipped with one pilot tunnel and one inclined shaft as auxiliary tunnels. The pilot tunnel is 16,963m long and has 34 cross passages. During construction, severe deformation occurred in the 9#-10# and 8F-9F pilot tunnel sections, resulting in a cross-sectional clearance of less than 2.5m. Traditional ventilation ducts were no longer suitable for installation. The Xingdong Tunnel needed to supply ventilation to up to 18 work faces simultaneously. The implementation layout of the "ductless open continuous ventilation chamber" construction ventilation method in the Xingdong Tunnel is shown in the diagram. Figure 1 and Figure 2 As shown, the ventilation effect during construction of the Xingdong East Tunnel after application is as follows: Adaptable to large deformation conditions: No need to lay traditional air ducts, directly use the tunnel guide and main tunnel as ventilation channels, fundamentally solving the problems of difficult air duct installation and frequent damage in large deformation sections. The air chamber and sealing wall structure can adapt to complex geological conditions such as surrounding rock heave and arch collapse.

[0057] High ventilation efficiency: The cross-section of the open air duct is much larger than that of traditional air ducts, reducing airflow resistance by 30%-50%. Combined with multi-stage continuous air chambers for segmented relay ventilation, it effectively reduces wind pressure loss. When ventilating over long distances (over 5km), the air volume attenuation rate is ≤10%, ensuring sufficient and stable air volume at the work site.

[0058] Low safety risk: The ventilation shaft structure is isolated by sealing the walls, achieving complete physical isolation between fresh air and stale air, avoiding cross-contamination; in high-gas environments, gas circulation caused by air leakage in the duct is eliminated, and combined with real-time monitoring and automatic control, the risk of gas explosion and poisoning is significantly reduced.

[0059] Minimal construction disruption: The ventilation system shares tunnel space with the vehicle transport channel, eliminating the need for separate ductwork installation; the ventilation chamber utilizes existing tunnel space, eliminating the need for additional ventilation corridor excavation, thus minimizing disruption to the main construction.

[0060] Advantageous in terms of economy: It eliminates the costs of purchasing, installing and maintaining traditional air ducts, reduces the extra energy consumption of the fan due to overcoming the resistance of the air duct, and can save more than 40,000 yuan per month in ventilation electricity and material maintenance costs, reducing the overall cost by 20%-30%.

[0061] This invention discloses a "ductless open continuous ventilation chamber" method for ventilation in tunnels with large deformation. This method addresses the problems of traditional ducted ventilation in such tunnels, including difficulties in duct installation, significant pressure loss, and poor ventilation stability. Corners may exist at pilot tunnels or inclined shafts, leading to substantial energy loss, low axial flow fan efficiency, reduced air velocity, and a poor working environment with high temperatures within the tunnel. Through the core design of "tunnel ductification, continuous ventilation chambers, and wall-separated partitions," an open ventilation channel and multi-stage continuous ventilation chambers are constructed using existing spaces in the pilot tunnel and main tunnel. Combined with wall separation and high-power main fan pressurization, a unidirectional flow ventilation system is formed: "pilot tunnel air intake—ventilator diversion—work face air supply—main tunnel or pilot tunnel exhaust." This results in better ventilation, higher fan utilization, and can be used for continuous ventilation chamber ventilation in tunnels. It eliminates the need for traditional ventilation ducts, adapts to complex working conditions with large deformation of surrounding rock and limited cross-section, and has advantages such as low ventilation resistance, high efficiency, low safety risk, and minimal construction interference. It effectively solves the ventilation problems of large deformation, long distance, and high gas tunnels, ensuring construction safety and operational efficiency.

[0062] The "continuous ventilation method" involves constructing a continuous ventilation structure consisting of primary and secondary ventilation chambers within the tunnel's pilot tunnel and cross passages. In this embodiment, the secondary ventilation chamber is formed using the underpass section of the pilot tunnel, dividing the entire tunnel's ventilation system into multiple relatively independent ventilation zones. Through the transition and adjustment functions of the ventilation chambers, uniform and efficient ventilation is achieved for each work surface.

[0063] The "ductless open-tunnel ventilation method" is used in a ventilation section that is in a severely deformed section where it is impossible to lay ducts. The tunnel space of the horizontal guide is used as a natural air duct. Combined with the synergistic effect of jet and axial flow fans, a directional circulation is formed through the airflow induction mechanism to achieve fresh air supply and exhaust of polluted gas. It is suitable for complex working conditions where the structure of the large deformation section is unstable and fixed ducts cannot be laid.

Claims

1. A method for constructing a long, deformable tunnel without ductwork for ventilation, characterized in that, Includes the following steps: Excavation of a parallel pilot tunnel for the main tunnel; Excavate the transverse passage between the parallel pilot tunnel and the main tunnel; Excavation of the main tunnel section; During the excavation of the main tunnel, the parallel pilot tunnel serves as the fresh air intake channel, while the main tunnel serves as the waste air exhaust channel. The fresh air introduction channel includes a series of multi-stage air chambers. The outlet of the air chamber furthest from the entrance of the fresh air introduction channel delivers fresh air to each level of the excavation face through air ducts.

2. The method for constructing a long, deformable tunnel without ventilation ducts as described in claim 1, characterized in that, When the excavation length of the main tunnel is less than the first preset length, no ventilation chamber is built, and fresh air is directly supplied to the excavation face at each level through the parallel pilot tunnel and the cross passage. Wherein, the first preset length is the length between the far end of the primary wind tunnel and the entrance of the parallel guide tunnel; the far end is the end away from the entrance of the parallel guide tunnel.

3. The method for constructing a long, deformable tunnel without ductwork ventilation as described in claim 2, characterized in that, The primary ventilation shaft and the parallel guide tunnel inlet are connected by ventilation ducts.

4. The method for constructing a ductless ventilation system for long, deformable tunnels as described in claim 2, characterized in that, When the excavation length of the main tunnel is greater than or equal to the first preset length and less than the Nth preset length, an N-1 level ventilation shaft is established; Wherein, N is the level of the wind turbine, which is a positive integer; the Nth preset length is the length between the far end of the Nth level wind turbine and the entrance of the parallel guide tunnel.

5. The method for constructing a ductless ventilation system for long, deformable tunnels as described in claim 3, characterized in that, When the excavation of the section corresponding to the transverse passage is completed, a sealing wall is built inside the transverse passage.

6. The method for constructing a ductless ventilation system for long, deformable tunnels as described in claim 5, characterized in that, Multi-stage ventilation chambers are partitioned by sealing walls to form relatively independent ventilation areas.

7. A method for constructing a ductless ventilation system for long, deformable tunnels as described in claim 5 or 6, characterized in that, The sealing wall adopts a brick or concrete structure, and the gap between the sealing wall and the tunnel rock wall is sealed, with an air leakage rate less than the preset air leakage rate threshold. The sealing wall is also reserved with adjustable air vents.

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