Tunnel overlapping cavern construction method and system

Abstract

The application discloses a tunnel overlapping cavern construction method and system, and belongs to the technical field of tunnel construction. The specific construction method comprises the following steps: staggered distance excavation of a first side flat guide and a main tunnel; determining whether the lateral rock pillar width between a second side flat guide and the main tunnel belongs to a small distance range, if yes, adopting hierarchical controlled blasting and controlling the vibration speed below a preset threshold; starting upper layer ventilation structure construction and continuously re-measuring the deformation of the middle partition rock pillar in the construction process, obtaining deformation data through monitoring measurement, and determining stability when the preset determination condition is met. Through three-step progressive construction and quantitative parameter control, the whole process stability control of the middle partition rock pillar is realized, and the method has the characteristics of construction safety, short construction period and low cost, and can be widely applied to underground engineering with overlapping cavern structure.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and specifically to a method and system for constructing overlapping tunnel chambers. Background Technology

[0002] As my country's railway tunnel engineering continues to develop towards greater length and depth, tunnel operation safety and disaster prevention have become a focus of industry attention. Railway tunnel emergency rescue stations, as key facilities for ensuring operational safety, are typically designed using traditional methods such as parallel pilot tunnel evacuation or single-section widening. However, to meet the dual functional requirements of ventilation and smoke extraction as well as personnel evacuation, railway tunnel rescue stations often require multiple chambers, including the main tunnel, left and right pilot tunnels, air supply ducts, smoke exhaust ducts, and vertical shafts, forming a three-dimensional, intersecting structure where the main tunnel and pilot tunnels are horizontally parallel, and the main tunnel and smoke exhaust ducts overlap vertically. In this overlapping chamber layout, the rock strata between the main tunnel and the upper smoke exhaust duct are only 3-5 meters thick, forming a central rock column with a complex stress state, the stability of which directly determines the safety of the entire rescue station structure.

[0003] However, in the current construction process, for multi-chamber overlapping systems including the main tunnel, double-sided pilot tunnels, ventilation ducts, and vertical shafts, there are problems such as repeated disturbance to the central rock pillar caused by multiple excavations, complex redistribution of surrounding rock stress, and great difficulty in deformation control. At the same time, cracking or even instability can easily occur during construction due to blasting vibration or improper timing. Summary of the Invention

[0004] The purpose of this invention is to overcome the difficulty in controlling the stability of the central rock column during existing overlapping tunnel construction, and to provide a method and system for constructing overlapping tunnels. The construction method includes staggered excavation of the first side pilot tunnel and the main tunnel, followed by graded controlled blasting after determining the minimum clearance range, and construction of the upper structure after the central rock column has stabilized. Through this scheme, the surrounding rock stability is controllable. Engineering verification has shown that the central rock column has not cracked or become unstable, effectively shortening the construction period and saving costs.

[0005] The first aspect of this invention provides a method for constructing overlapping tunnel chambers, comprising the following steps:

[0006] Step 1: Construct the inclined shaft, and then construct the first side pilot tunnel and the main tunnel through the inclined shaft; wherein, the working faces of the first side pilot tunnel and the main tunnel are staggered during excavation; Step 2: After the first side pilot tunnel is excavated, the second side pilot tunnel is constructed. When the width of the lateral rock pillar between the second side pilot tunnel and the main tunnel is within the small clearance range, controlled blasting is used for excavation, and the blasting parameters are adjusted in real time through blasting vibration monitoring to control the blasting vibration velocity at the lateral rock pillar below the preset threshold. After steps 3, 1, and 2 are completed, construction of the upper ventilation structure will commence. During construction, the settlement and horizontal convergence of the arch of the central diaphragm column will be re-measured after each excavation cycle. If the re-measured deformation rate meets the preset stability criteria, the next excavation cycle can proceed. If the re-measured deformation rate exceeds the preset value, construction will be suspended and temporary reinforcement measures will be taken. Work will resume once the stability criteria are met again. Deformation data of the central diaphragm column will be obtained through monitoring and measurement. When the deformation data meets the preset stability criteria, the deformation of the central diaphragm column will be determined to be stable.

[0007] This application provides a method for constructing overlapping tunnel chambers, comprising first constructing an inclined shaft, and then constructing a first side pilot tunnel and a main tunnel through the inclined shaft; wherein the first side pilot tunnel and the main tunnel face are excavated at a staggered distance, which spatially isolates the mutual interference of blasting vibrations between the two tunnels, laying the foundation for subsequent construction; then, after the excavation of the first side pilot tunnel is completed, a second side pilot tunnel is constructed; wherein, when the width of the lateral rock pillar between the second side pilot tunnel and the main tunnel is within the small clearance range, controlled blasting is used for excavation, and blasting parameters are adjusted in real time through blasting vibration monitoring to control the blasting vibration velocity at the lateral rock pillar below a preset threshold; a small clearance judgment mechanism is introduced during the construction of the second side pilot tunnel, and blasting is only carried out when the width of the lateral rock pillar is within the small clearance range. Controlled blasting and vibration monitoring were implemented to avoid insufficient safety redundancy or overly conservative approaches caused by one-size-fits-all blasting, thus achieving precise protection of the lateral rock pillars. After the completion of steps 1 and 2, the construction of the upper ventilation structure was initiated. During construction, the settlement and horizontal convergence of the arch of the central rock pillar were re-measured after each excavation cycle. If the re-measured deformation rate met the preset stability judgment conditions, the next cycle of excavation could proceed. If the re-measured deformation rate exceeded the preset value, construction was suspended and temporary reinforcement measures were taken. Work resumed after the stability judgment conditions were met again. Among these measures, deformation data of the central rock pillar was obtained through monitoring and measurement. When the deformation data met the preset stability judgment conditions, the deformation of the central rock pillar was determined to be stable. This construction method first avoids mutual interference between the two tunnels through staggered excavation, then protects the lateral rock pillars through graded judgment and precise controlled blasting, and finally re-measures the deformation of the central rock pillar during the construction of the upper ventilation structure. If the deformation exceeds the limit, reinforcement is suspended; it continues only when the conditions are met, ensuring that deformation is controlled throughout the process. This effectively solves the technical problem of repeated disturbance of the surrounding rock and difficulty in ensuring the stability of the central rock pillar during the construction of overlapping tunnels. Engineering verification shows that this method effectively shortens the construction period and saves costs while ensuring that the central rock pillar does not crack or become unstable.

[0008] Furthermore, the overlapping tunnel chambers include a main tunnel, a first side guide located to the left of the main tunnel, a second side guide located to the right of the main tunnel, and an upper ventilation structure located above the main tunnel. The rock strata between the main tunnel and the upper ventilation structure are intermediate rock pillars, and the rock strata between the second side guide and the main tunnel are lateral rock pillars.

[0009] Furthermore, in step 1, the working face offset between the main tunnel and the first side pilot tunnel is ≥30m. Setting a reasonable offset range can provide a safe working space for the simultaneous construction of the first side pilot tunnel and the main tunnel, ensuring that the working faces on both sides do not interfere with each other, and avoiding a decrease in construction efficiency due to excessive offset, thus achieving a balance between safety and efficiency.

[0010] Furthermore, the minimum clearance range is determined based on the surrounding rock grade: in Grade III surrounding rock, a minimum clearance range is defined as the width of the lateral rock pillar between the main tunnel and the pilot tunnel being 1.0 to 1.5 times the excavation span of the main tunnel; in Grade IV surrounding rock, a minimum clearance range is defined as 1.5 to 2.0 times the excavation span of the main tunnel. Numerical simulation analysis of the stress distribution and plastic zone range of the surrounding rock under different surrounding rock grades and rock pillar widths was conducted using FLAC³D finite element software. When the width of the lateral rock pillar in Grade III surrounding rock is less than 1.0 times the excavation span, a continuous plastic zone appears in the lateral rock pillar, and the surrounding rock between the main tunnel and the pilot tunnel will completely lose its self-supporting capacity, requiring strengthened support and controlled blasting measures; when the width is 1.0 to 1.5 times, the range of the plastic zone within the lateral rock pillar is controllable, and the overall stability of the surrounding rock can be maintained; when the width is greater than 1.5 times, it can be constructed as a separated tunnel, without the need for special treatment of the minimum clearance. Due to the development of joints and fissures and the reduction of self-stabilizing ability, the critical value of Class IV surrounding rock increases to 1.5 to 2.0 times the excavation span.

[0011] Based on the surrounding rock grade, the selection range of the minimum clearance was determined through a tiered approach. Grade III surrounding rock exhibits good integrity and strong self-stabilizing ability, allowing for a more appropriate reduction in the critical value to avoid overly conservative approaches and improve construction efficiency. Grade IV surrounding rock shows well-developed joints and fissures and poor stability, necessitating a corresponding increase in the critical value to ensure safety redundancy. This tiered quantitative standard is technically linked to the blasting vibration velocity tiered thresholds (8–12 cm / s for Grade III, 5–8 cm / s for Grade IV), avoiding safety risks or efficiency losses caused by uniform critical values ​​and providing a scientific basis for controlling the initiation of blasting.

[0012] Furthermore, the main tunnel excavation span refers to the horizontal width of the designed excavation outline of the main tunnel. Furthermore, the preset threshold for blasting vibration velocity in step 2 is: 8-12 cm / s for Class III surrounding rock and 5-8 cm / s for Class IV surrounding rock.

[0013] By linking vibration velocity thresholds to surrounding rock grades, precise graded control is provided. A relatively high threshold is used for Grade III surrounding rock to avoid excessive conservatism that could lead to decreased blasting efficiency and extended construction periods. A lower threshold is used for Grade IV surrounding rock to ensure that lateral rock columns do not suffer damage or cracking under blasting loads, effectively preventing rock column instability. This graded threshold, along with the rock column width grading standards (Grade III 1.0–1.5B, Grade IV 1.5–2.0B), forms a complete technical chain: first, the rock column width and surrounding rock grade are used to determine whether it falls within the small clearance range (initiating controlled blasting); then, a specific vibration velocity control target is determined based on the same surrounding rock grade (implementing graded control). Engineering verification shows that blasting construction controlled by this threshold did not result in significant cracking or instability of the lateral rock columns, while blasting efficiency was ensured, achieving a balance between safety and efficiency.

[0014] Furthermore, in step 2, when using controlled blasting for excavation, the maximum charge per section is controlled between 5 and 15 kg, the cut location is far from the lateral rock pillar, and the micro-delay is ≥100 ms.

[0015] The charge weight is positively correlated with the blasting vibration velocity. A quantitative range of 5–15 kg represents a balance between ensuring rock-breaking effectiveness and controlling vibration intensity. Charges below 5 kg are insufficient for effective rock breaking and may lead to under-excavation, while charges above 15 kg may cause the vibration velocity to exceed the safety threshold, damaging lateral rock pillars. Slotting blasting is the most concentrated and vibrating stage in a single charge, significantly impacting the vibration of lateral rock pillars. Placing the slotting holes away from the lateral rock pillars ensures the main propagation direction of the vibration wave is away from the protected rock pillar, effectively reducing the impact on the lateral rock pillar from the propagation path. Micro-delay blasting, by grouping the total charge and detonating it sequentially, ensures that when the micro-delay is ≥100 ms, the vibration wave from the previous blast has sufficiently attenuated before detonating the next blast. This results in significantly staggered vibration peaks and negligible superposition effects, avoiding the larger combined amplitude formed by the superposition of vibration waves. The three measures work together and are indispensable, ensuring that the blasting vibration velocity at the lateral rock pillar is always below the limited safety threshold (8-12 cm / s for Level III and 5-8 cm / s for Level IV), thus achieving all-round protection for the lateral rock pillar.

[0016] Furthermore, in step 2, after the excavation of the first side guide tunnel is completed, the second side guide tunnel and its ancillary caverns are constructed. The ancillary caverns for the rescue station include a cross passage, a transportation and maintenance passage, and a fan installation passage. The construction of the ancillary caverns is carried out concurrently with the construction of the second side guide tunnel to minimize mutual interference.

[0017] Furthermore, the preset stability judgment condition is: the arch subsidence rate and the horizontal convergence rate are both ≤0.2mm / d for 7 consecutive days. After the second side tunnel and its auxiliary caverns are fully excavated and initially supported in step 2, deformation and stability monitoring of the central diaphragm rock column begins. When both the crown settlement rate and the horizontal convergence rate are less than 0.2 mm / d, the surrounding rock is in a basically stable state, and secondary lining can be carried out. The requirement of continuous observation for 7 days eliminates interference from short-term accidental factors (such as blasting disturbances, temperature changes, mechanical vibrations, etc.) on the monitoring data, ensuring that the surrounding rock has reached a sufficiently convergent and stable state. Crown settlement reflects the vertical deformation of the central diaphragm column, while horizontal convergence reflects the impact of the lateral compression of the central diaphragm column on the tunnel wall. Stability can only be determined when both meet the threshold requirements. This provides a double safety guarantee for thin-layered central diaphragm columns with a thickness of only 3-5 m, avoiding the dual problems of premature secondary lining construction leading to excessive surrounding rock pressure and cracking, or premature secondary lining construction leading to project delays, thus achieving a balance between safety and efficiency. Engineering verification shows that secondary lining construction after determining the central diaphragm column to be stable according to this standard did not result in lining cracking due to surrounding rock deformation, verifying the scientific validity and reliability of this quantitative standard.

[0018] Furthermore, the upper ventilation structure described in step 3 includes an air supply duct, an air supply shaft, and a smoke exhaust duct.

[0019] A second aspect of the present invention provides a tunnel overlapping chamber construction system for implementing the above method, comprising: a monitoring unit, including a total station, a convergence meter and a blasting vibration meter deployed in the central rock column and adjacent chambers, for real-time acquisition of crown settlement data, horizontal convergence data and blasting vibration velocity data at the lateral rock columns; The data processing unit, connected to the monitoring unit, is used to receive and process monitoring data, calculate the deformation rate of the central rock column and compare it with the threshold in the preset stability judgment condition, and compare the measured blasting vibration velocity with the preset threshold. The control unit is pre-set with timing control logic corresponding to steps 1 to 3, which is used to: when the data processing unit determines that the deformation rate of the diaphragm rock column meets the stability judgment condition for 7 consecutive days, issue a process conversion instruction to allow the construction of the upper ventilation structure; when the upper ventilation structure is fully constructed and the deformation rate of the diaphragm rock column meets the stability judgment condition again, issue a process conversion instruction to allow the construction of the secondary lining; when the measured blasting vibration velocity exceeds the preset threshold, issue a blasting parameter adjustment instruction; if the parameter still exceeds the standard after adjustment for two consecutive blasting cycles, issue a blocking signal to suspend blasting operations.

[0020] This invention provides a tunnel overlapping chamber construction system for implementing the above-described method, comprising a monitoring unit, a data processing unit, and a control unit. The monitoring unit uses a total station, convergence meter, and blasting vibration meter deployed at the central rock column and adjacent chambers to collect real-time data on the arch subsidence of the central rock column, horizontal convergence data, and blasting vibration velocity at the lateral rock columns, providing raw data support for subsequent judgments. The data processing unit is connected to the monitoring unit, receives and processes the monitoring data, calculates the deformation rate of the central rock column and compares it with a threshold value (≤0.2 mm / d for 7 consecutive days) in the preset stability judgment conditions, and simultaneously compares the measured blasting vibration velocity with the preset threshold value (Level III 8-12 cm / d). The system compares the blasting vibration velocity (5-8 cm / s) of Class IV and Class IV blasting vibrations, transforming the raw monitoring data into quantifiable results. The control unit connects to the data processing unit and automatically outputs process conversion commands or blasting parameter adjustment commands based on the comparison results. When the deformation data of the central rock column meets the stability criteria, a command is issued permitting secondary lining construction, upgrading the decision-making process for secondary lining construction from manual experience to automatic system determination. When the measured blasting vibration velocity exceeds a preset threshold, a blasting parameter adjustment command is issued to reduce the single-stage charge and / or adjust the cut position and / or increase the micro-delay. If necessary, a blocking signal to suspend blasting operations is issued, achieving closed-loop control of real-time monitoring and immediate adjustment of blasting vibration. This makes safety risk control during construction more timely, accurate, and reliable.

[0021] Furthermore, the monitoring unit also includes multi-point displacement gauges and / or stress gauges deployed at the diaphragm rock column to acquire deep deformation and / or stress state data of the diaphragm rock column.

[0022] Furthermore, the process conversion instructions output by the control unit include: when the deformation data of the diaphragm rock column meets the conditions, issuing an instruction to allow the construction of secondary lining; when the measured blasting vibration velocity exceeds the threshold, issuing an instruction to reduce the single-stage charge amount and / or adjust the slotting position and / or increase the micro-delay blasting parameter adjustment.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This application provides a method for constructing overlapping tunnel chambers, comprising first constructing an inclined shaft, and then constructing a first side pilot tunnel and a main tunnel through the inclined shaft; wherein, the working faces of the first side pilot tunnel and the main tunnel are staggered during excavation, spatially isolating the mutual interference of blasting vibrations between the two tunnels, laying the foundation for subsequent construction; then, after the excavation of the first side pilot tunnel is completed, a second side pilot tunnel is constructed; wherein, when the width of the lateral rock pillar between the second side pilot tunnel and the main tunnel is within the small clearance range, controlled blasting is used for excavation, and blasting parameters are adjusted in real time through blasting vibration monitoring to control the blasting vibration velocity at the lateral rock pillar below a preset threshold; a small clearance judgment mechanism is introduced during the construction of the second side pilot tunnel, and blasting is only carried out when the width of the lateral rock pillar is within the small clearance range. Controlled blasting and vibration monitoring were implemented to avoid insufficient safety redundancy or overly conservative approaches caused by one-size-fits-all blasting, thus achieving precise protection of the lateral rock pillars. After the completion of steps 1 and 2, the construction of the upper ventilation structure was initiated. During construction, the settlement and horizontal convergence of the arch of the central rock pillar were re-measured after each excavation cycle. If the re-measured deformation rate met the preset stability criteria, the next excavation cycle could proceed. If the re-measured deformation rate exceeded the preset value, construction was suspended and temporary reinforcement measures were taken. Work resumed after the stability criteria were met again. The deformation data of the central rock pillar was obtained through monitoring and measurement. When the deformation data met the preset stability criteria, the deformation of the central rock pillar was determined to be stable. This construction method first avoids mutual interference between the two tunnels through staggered excavation, then protects the lateral rock pillars through graded judgment and precise controlled blasting, and finally re-measures the deformation of the central rock pillar during the construction of the upper ventilation structure. If the deformation exceeds the limit, reinforcement is suspended; it continues only when the conditions are met, ensuring that deformation is controlled throughout the process. This effectively solves the technical problem of repeated disturbance of the surrounding rock and difficulty in ensuring the stability of the central rock pillar during the construction of overlapping tunnels. Engineering verification shows that this method effectively shortens the construction period and saves costs while ensuring that the central rock pillar does not crack or become unstable.

[0024] 2. This invention provides a tunnel overlapping chamber construction system for implementing the above method, including a monitoring unit, a data processing unit, and a control unit. The monitoring unit uses a total station, convergence meter, and blasting vibration meter deployed at the central rock column and adjacent chambers to collect real-time data on the arch subsidence of the central rock column, horizontal convergence data, and blasting vibration velocity data at the lateral rock columns, providing raw data support for subsequent judgments. The data processing unit is connected to the monitoring unit, receives and processes the monitoring data, calculates the deformation rate of the central rock column and compares it with the threshold in the preset stability judgment conditions (≤0.2mm / d for 7 consecutive days), and simultaneously compares the measured blasting vibration velocity with the preset threshold (Level III 8-12cm). The system compares the measured blasting vibration velocity (5-8 cm / s for Class IV) with that of Class IV, converting the raw monitoring data into quantifiable results. The control unit connects to the data processing unit and automatically outputs process conversion commands or blasting parameter adjustment commands based on the comparison results. When the deformation data of the central rock column meets the stability criteria, a command is issued permitting secondary lining construction, upgrading the decision-making process for secondary lining construction from manual experience to automatic system determination. When the measured blasting vibration velocity exceeds a preset threshold, a blasting parameter adjustment command is issued to reduce the single-stage charge and / or adjust the cut position and / or increase the micro-delay. If necessary, a blocking signal to suspend blasting operations is issued, achieving closed-loop control of real-time monitoring and immediate adjustment of blasting vibration. This makes safety risk control during construction more timely, accurate, and reliable. Attached Figure Description

[0025] Figure 1 The process flow diagram of the tunnel overlapping chamber construction method provided by the present invention.

[0026] Figure 2 This is a schematic diagram of the overlapping chambers in a tunnel.

[0027] Figure 3 This is a schematic diagram showing the layout of smoke exhaust ducts and vertical shafts.

[0028] Figure 4 This is a schematic diagram showing the layout of the air supply duct and air supply shaft.

[0029] Markings in the diagram: 1-Main tunnel; 2-First side guide; 3-Second side guide; 4-Horizontal passage; 5-Transportation and maintenance passage; 6-Fan installation passage; 7-Air supply duct; 8-Air supply shaft; 9-Longitudinal smoke exhaust passage; 10-Horizontal smoke exhaust passage; 11-Smoke exhaust shaft; 12-Inclined shaft. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0031] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0032] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0033] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0034] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.

[0035] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0036] Example 1 like Figure 1 As shown, the tunnel overlapping chamber construction method provided by this invention mainly includes three construction stages: first, constructing the inclined shaft, the first side pilot tunnel, and the main tunnel; second, constructing the second side pilot tunnel and the auxiliary chamber for the rescue station; and finally, constructing the upper ventilation structure. The method will be described in detail below with reference to specific embodiments.

[0037] This embodiment takes the construction of the overlapping cavern of the disaster prevention and rescue station at the exit section of the QG tunnel on the newly built XN to CD railway as an example to describe the technical solution of the present invention in detail. The QG tunnel is designed as a double-track tunnel, and the rescue station is 1680m long. An evacuation pilot tunnel is set up on each side of the tunnel at 45m. The main structure adopts the arrangement of overlapping air supply and exhaust ducts and evacuation spaces.

[0038] like Figure 2 As shown, the overlapping tunnel chambers involved in this embodiment include: main tunnel 1 (train tunnel), first side guide 2 (left side guide), second side guide 3 (right side guide), construction cross passage 4, transportation and maintenance passage 5, fan installation passage 6, air supply duct 7, air supply shaft 8, longitudinal smoke exhaust passage 9, transverse smoke exhaust passage 10 and smoke exhaust shaft 11.

[0039] The centerline distance between the main tunnel 1 and the first side guide 2 is 45m. The centerline distance between the main tunnel 1 and the second side guide 3 is generally 45m, but narrows in sections traversing geological structural zones, causing the width of the lateral rock pillars to fall within a small clearance range (12m-18m in this embodiment). The bottoms of all three are basically flush. A longitudinal smoke exhaust channel 9 (585.32m long, 6.0m x 5.0m cross-section) overlaps above the main tunnel 1. The rock mass between the main tunnel 1 and the longitudinal smoke exhaust channel 9 forms the central rock pillar, with a thickness of 3-5m, which is a key area requiring protection during construction. The rock mass between the second side guide 3 and the main tunnel 1 forms the lateral rock pillar.

[0040] It should be clarified that in this embodiment, the distance between the centerline of the second side pilot tunnel 3 and the main tunnel 1 in a general section is 45m. Under this distance, the width of the lateral rock pillars is greater than the upper limit of the minimum clearance range. In such sections, the controlled blasting procedure described in step 2 is not performed; instead, conventional methods for separated tunnels are used. The controlled blasting method and its parameters described in step 2 are adopted for specific sections where the distance between the centerline of the second side pilot tunnel 3 and the main tunnel 1 narrows due to the tunnel traversing a local geological structure zone, causing the width of the lateral rock pillars to fall within the minimum clearance range. Construction in this local section is strictly carried out according to the controlled blasting parameters in step 2; other conventional sections are still constructed using conventional methods for separated tunnels.

[0041] Before construction, the design drawings were carefully reviewed, and a three-dimensional handover was conducted using a BIM model to clarify the spatial relationships and construction sequence of each chamber. A specialized construction plan and blasting design were prepared and reviewed by experts. Surveying and setting out were completed to accurately locate the openings of each chamber.

[0042] (I) Step 1: Construction of inclined shaft 12, first side horizontal guide 2 and main tunnel 1 First, inclined shaft 12 was constructed. Inclined shaft 12 was excavated in its entirety, following the principle of excavation and support as it was excavated. Immediately after excavation, initial shotcrete was applied, steel frames and anchor bolts were installed, and the shaft was promptly sealed into a ring. Lining was carried out simultaneously with excavation, with the invert arch advanced ahead of the excavation. The secondary lining step distance did not exceed the standard. A mobile trestle was used for assistance, and the invert arch trolley and hydraulic lining trolley were used to integrally cast the arch wall.

[0043] After the inclined shaft 12 is constructed to the position of the first side guide 2, a large-scale excavation face for the first side guide 2 is reserved, and construction begins on the left transverse passage. The left transverse passage connects the main tunnel 1 and the first side guide 2. After construction on the left transverse passage to the edge of the main tunnel 1, a pilot tunnel is used to enter the main tunnel 1.

[0044] The first side pilot tunnel 2 and the main tunnel 1 are constructed simultaneously, with the tunnel faces maintained at a staggered distance of no less than 30m. This staggered distance is determined by numerical simulation using FLAC³D finite element software. When the tunnel face distance is 30m, the tensile stress of the initial support is 0.3638MPa and the compressive stress is 23.45MPa, both within the safe allowable range. Class III surrounding rock is excavated using the full-face method, while Class IV and V surrounding rock are excavated using the bench method. Following the principle of excavating and supporting simultaneously, initial support is promptly applied after excavation to ensure a closed ring.

[0045] (II) Step 2: Construct the second side guide 3 After the excavation of the first side guide tunnel 2 is completed, the construction of the second side guide tunnel 3 will commence. Simultaneously, the main auxiliary caverns of the rescue station, including the rescue station cross passage 4, the transportation and maintenance passage 5, and the fan installation passage 6, will be constructed sequentially. The construction sequence for each auxiliary cavern is as follows: first construct the transportation and maintenance passage 5 and the fan installation passage 6, then construct the second side guide tunnel 3, and finally construct each construction cross passage 4, in order to reduce the number of simultaneous work surfaces and avoid cross-interference.

[0046] Minimum clearance determination: When the width of the lateral rock pillar between the second side guide tunnel 3 and the main tunnel 1 falls within the minimum clearance range, controlled blasting is used for excavation. The minimum clearance range is determined according to the surrounding rock grade: in Grade III surrounding rock, the width of the lateral rock pillar is 1.0 to 1.5 times the excavation span of the main tunnel 1; in Grade IV surrounding rock, it is 1.5 to 2.0 times the excavation span of the main tunnel 1. In this embodiment, the excavation span of the main tunnel 1 is approximately 12m. A minimum clearance is determined when the width of the lateral rock pillar is 12 to 18m in Grade III surrounding rock and 18 to 24m in Grade IV surrounding rock. When the width of the lateral rock pillar is greater than the above range, conventional separated tunnel construction is used, and controlled blasting is not required.

[0047] Blasting parameters were controlled as follows: the preset threshold for blasting vibration velocity was 8–12 cm / s for Class III surrounding rock and 5–8 cm / s for Class IV surrounding rock. The blasting vibration wave was transmitted from the second lateral guide through the lateral rock column to the central diaphragm rock column. The central diaphragm rock column, only 3–5 m thick and under thin-plate stress, is the most sensitive part of the overlapping cavern system to blasting vibration. Based on the dynamic tensile strength of C25 shotcrete (approximately 2.0–2.5 MPa) and the thin-plate stress model of the central diaphragm rock column, the critical peak particle vibration velocity for the central diaphragm rock column to avoid tensile failure was calculated to be 15.7 cm / s. The greater the thickness of the lateral rock column, the longer the attenuation distance of the blasting vibration wave from the second lateral guide to the central diaphragm rock column. The vibration response at the central diaphragm rock column will be lower than the measured value at the lateral rock column. Therefore, controlling the vibration velocity at the lateral rock column below 15.7 cm / s ensures that the vibration response of the central diaphragm rock column is below its critical value. For Class III surrounding rock, a vibration velocity of 8–12 cm / s is considered safe; for Class IV surrounding rock, which has lower strength and is more sensitive to vibration, a velocity of 5–8 cm / s is more stringent. The maximum charge per section is controlled between 5 and 15 kg, and the cut location is far from the lateral rock column, with a micro-delay ≥100 ms. Hollow straight-hole cuts are used to increase the number of empty holes and reduce clamping effects. Peripheral holes are blasted using pre-splitting blasting or smooth blasting to block the propagation of vibration waves to the lateral rock column.

[0048] Blasting vibration monitoring: After each blasting cycle, blasting vibration monitoring points are set up at the lateral rock pillars and key locations in adjacent caverns. If the measured peak particle vibration velocity exceeds the above-mentioned threshold, the blasting parameters are adjusted in a timely manner (reducing the single-stage charge, adjusting the cut position, or increasing the micro-delay) until the requirements are met. If the measured vibration velocity still exceeds the threshold after two consecutive adjustments, a blocking signal to suspend blasting operations is issued.

[0049] Excavation methods for various tunnels and caverns: The full-section method is used for Class III surrounding rock, and the bench method is used for Class IV surrounding rock. The excavation advance is controlled at 0.5 to 1.0 m / cycle.

[0050] (III) Step 3: Construct the upper ventilation structure Before commencing construction of the upper ventilation structure, it must be confirmed that steps 1 and 2 have been completed and that the deformation rate of the central diaphragm column is ≤0.2mm / d for 7 consecutive days. During construction, short-foot cyclic excavation is adopted. After each cycle, the settlement and horizontal convergence of the central diaphragm column arch are promptly re-measured. If the re-measured deformation rate is still ≤0.2mm / d, the next cycle can proceed; if the re-measured rate exceeds the limit, construction must be immediately suspended and temporary reinforcement measures implemented. Work can resume only after the stability criteria are met again. The upper ventilation structure includes air supply duct 7, air supply shaft 8, and smoke exhaust duct. Figure 3 As shown, the smoke exhaust duct includes a longitudinal smoke exhaust duct 9 and a transverse smoke exhaust duct 10, and a smoke exhaust shaft 11 is used to connect the transverse smoke exhaust duct 10 and the main opening 1. Figure 4As shown, the air supply duct 7 is connected to the air supply shaft 8. Fresh air enters the air supply shaft 8 through the air supply duct 7 and is then delivered to the first side guide 2 and the second side guide 3 respectively.

[0051] Deformation stability assessment: Deformation data of the central diaphragm rock column is obtained through monitoring and measurement. Monitoring points are set up at the arch crown and both sides of the tunnel wall in the main tunnel 1. Total station and convergence meter are used to monitor the arch crown settlement and horizontal convergence. When the arch crown settlement rate and horizontal convergence rate are ≤0.2mm / d for 7 consecutive days, the deformation of the central diaphragm rock column is determined to be stable. When the deformation rate is <0.2mm / d, monitoring is carried out at the normal frequency (once a day). When the deformation rate is ≥0.2mm / d, the monitoring frequency is increased (2-3 times a day). When the deformation rate is ≥0.2mm / d, the upper ventilation structure and all subsequent excavation operations are immediately suspended, and temporary supports are added at the corresponding locations in the main tunnel for reinforcement. After reinforcement is completed, continuous monitoring is resumed until the deformation rate recovers to ≤0.2mm / d for 7 consecutive days before subsequent construction can resume. If the deformation rate continues to rise after reinforcement and no convergence trend is observed, the emergency plan for deep grouting of the surrounding rock or modification of the support scheme should be activated immediately.

[0052] Shaft Construction: Both the smoke exhaust shaft 11 and the ventilation shaft 8 were constructed using the pilot tunnel method. The specific steps were as follows: First, the shaft's locking joint was poured, and stainless steel pipe railings were installed according to the design. A central pilot tunnel with a diameter of φ1.0–1.2m was excavated at the center of the shaft as a slag chute. Manual excavation was used, primarily with pneumatic drills, supplemented by pneumatic picks, and shallow-hole drilling and blasting were employed when necessary. The excavation advance was controlled at 0.5m / cycle, and the wall protection work had to keep pace with the excavation. After the central pilot tunnel was completed, the shaft was blasted to enlarge it to the designed dimensions. Slag fell through the central pilot tunnel to the lower passage, and was transported from the bottom of the shaft using a loader and dump trucks. During construction, a dedicated safety officer was stationed at the top of the shaft to monitor the entire process. No more than three personnel were allowed inside the shaft, and all workers inside the shaft were required to wear safety ropes and helmets at all times.

[0053] Intersection Construction: The intersection construction adopts the step excavation method, with each excavation advance controlled at a spacing of 1-2 steel frames. The requirements for initial support and secondary lining construction are the same as those for the rescue station cross passage, and the formwork can only be removed after the secondary lining concrete strength reaches 100% of the design strength.

[0054] This embodiment employs a tunnel overlapping chamber construction system, which includes a monitoring unit, a data processing unit, and a control unit.

[0055] The monitoring unit includes a total station, convergence meter, and blasting vibration meter deployed at the central diaphragm rock column and adjacent chambers. These are used to collect real-time data on the crown settlement, horizontal convergence, and blasting vibration velocity at the lateral rock columns of the central diaphragm rock column. In addition, multiple displacement gauges and stress gauges are deployed at the central diaphragm rock column to obtain data on its deep deformation and stress state.

[0056] Data processing unit: Connected to the monitoring unit, it uses an industrial computer to receive and process monitoring data, calculate the deformation rate of the central rock column and compare it with the threshold in the preset stability judgment condition (≤0.2mm / d for 7 consecutive days), and compare the measured blasting vibration velocity with the preset threshold (8-12cm / s for Class III surrounding rock and 5-8cm / s for Class IV surrounding rock).

[0057] Control Unit: A programmable logic controller (PLC) is used, which is connected to the data processing unit. The control unit has a preset control logic program corresponding to the steps of the method of this invention. The control unit is connected to the data processing unit through a signal line. When the comparison result output by the data processing unit meets the preset conditions, the control unit outputs instructions in the following manner: (1) When the deformation data of the middle diaphragm rock column after the completion of steps 1 and 2 meets the stability judgment conditions, the control unit sends an audible and visual prompt instruction to the site monitoring room to allow the start of the upper ventilation structure construction; (2) When the upper ventilation structure is fully constructed and the deformation data of the middle diaphragm rock column meets the stability judgment conditions again, the control unit sends an audible and visual prompt instruction to the site monitoring room to allow the construction of the secondary lining; (3) When the measured blasting vibration velocity exceeds the preset threshold, the control unit sends adjustment instructions to the blasting operator terminal to reduce the single-stage charge and / or adjust the slotting position and / or increase the micro-delay. When the measured vibration velocity still exceeds the threshold after two consecutive adjustments, a blocking signal to suspend the blasting operation is issued.

[0058] The control unit and the data processing unit are connected via RS-485 or Ethernet signal lines. The data acquisition frequency is no less than once per day, and is increased to 2-3 times per day when the deformation rate approaches the threshold. The control unit has preset timing control logic corresponding to steps 1 to 3. When the deformation rate of the diaphragm rock column meets the stability judgment condition for 7 consecutive days after the completion of steps 1 and 2, the control unit automatically sends an audible and visual prompt signal to the site monitoring room to allow the start of the upper ventilation structure construction. When the upper ventilation structure is fully constructed and the deformation rate of the diaphragm rock column meets the stability judgment condition for 7 consecutive days again, the control unit automatically sends an audible and visual prompt signal to the site monitoring room to allow the construction of the secondary lining. When the peak vibration velocity measured by the blasting vibrator exceeds the preset threshold, the control unit sends a blasting parameter adjustment command to the blasting operator terminal before the next blasting cycle. If the parameter still exceeds the limit after adjustment for two consecutive blasting cycles, a lockout signal to suspend the blasting operation is output.

[0059] Those skilled in the art should understand that the control unit can also be implemented using a microcontroller, a digital signal processor, or an embedded system. The specific selection depends on the project scale and cost requirements, as long as the above comparison judgment and instruction output functions can be achieved.

[0060] This embodiment avoids repeated disturbance to the surrounding rock through a three-step progressive construction method. Engineering verification showed that no obvious cracking or instability occurred in the rock pillars, and no safety accidents occurred. Through scientific phased construction and process connection, the construction period of the overlapping caverns of the rescue station was shortened by 5 months. By reducing idle time and rework and optimizing resource allocation, construction costs were saved by approximately RMB 1.15 million, or approximately RMB 682 per linear meter. By using quantitative parameters such as offset distance, blasting vibration threshold, and deformation stability standard, quality control was transformed from qualitative description to quantitative control, and the support structure formed an integral stress system without weak links.

[0061] Example 2 This embodiment is basically the same as Embodiment 1, except for the surrounding rock conditions. When the overlapping caverns are located in Class V weak surrounding rock, the peak particle vibration velocity of the controlled blasting is controlled below 5 cm / s, and mechanical excavation is used instead of blasting excavation if necessary. The excavation advance is controlled below 0.5 m / cycle, and the support parameters are appropriately strengthened (such as increasing the spacing of the steel frame and increasing the thickness of the shotcrete). The criterion for judging deformation stability is also the same: a deformation rate of less than 0.2 mm / d for 7 consecutive days. Other steps are the same as in Embodiment 1.

[0062] Example 3 This embodiment is basically the same as Embodiment 1, except for the shaft construction method. When the shaft depth is large (over 30m), a raise boring machine can be used to construct a pilot shaft first, followed by manual enlargement. The specific steps are as follows: a raise boring machine is used to drill a pilot hole from top to bottom, and then the hole is enlarged from bottom to top to form a φ1.2~1.5m pilot shaft as a chuting channel; then, manual enlargement is carried out from top to bottom to the design cross-section, and the slag falls from the pilot shaft to the lower channel and is then mechanically transported. The excavation advance is controlled at 0.6~0.8m / cycle. Other steps are the same as in Embodiment 1.

[0063] The tunnel overlapping chamber construction method and system provided by this invention can be widely applied to underground projects with overlapping chamber structures, such as railway tunnel rescue stations, subway transfer stations, and underground integrated pipe corridors. This invention has been successfully applied in the disaster prevention and rescue station project at the exit section of the Gansu-Qinghai Tunnel on the newly built Xining-Chengdu Railway, achieving good technical and economic results and demonstrating clear industrial applicability.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing overlapping tunnel chambers, characterized in that, Includes the following steps: Step 1: Construct the inclined shaft, and then construct the first side pilot tunnel and the main tunnel through the inclined shaft; wherein, the working faces of the first side pilot tunnel and the main tunnel are staggered during excavation; Step 2: After the first side pilot tunnel is excavated, the second side pilot tunnel is constructed. When the width of the lateral rock pillar between the second side pilot tunnel and the main tunnel is within the small clearance range, controlled blasting is used for excavation, and the blasting parameters are adjusted in real time through blasting vibration monitoring to control the blasting vibration velocity at the lateral rock pillar below the preset threshold. After steps 3, 1, and 2 are completed, construction of the upper ventilation structure will commence. During construction, the settlement and horizontal convergence of the arch of the central diaphragm column will be re-measured after each excavation cycle. If the re-measured deformation rate meets the preset stability criteria, the next excavation cycle can proceed. If the re-measured deformation rate exceeds the preset value, construction will be suspended and temporary reinforcement measures will be taken. Work will resume once the stability criteria are met again. Deformation data of the central diaphragm column will be obtained through monitoring and measurement. When the deformation data meets the preset stability criteria, the deformation of the central diaphragm column will be determined to be stable.

2. The method according to claim 1, characterized in that, In step 1, the misalignment between the working faces of the main tunnel and the first side tunnel is ≥30m.

3. The method according to claim 1, characterized in that, The minimum clearance range is determined according to the surrounding rock grade: in Grade III surrounding rock, the width of the lateral rock pillar between the main tunnel and the pilot tunnel is 1.0 to 1.5 times the excavation span of the main tunnel; in Grade IV surrounding rock, it is 1.5 to 2.0 times the excavation span of the main tunnel.

4. The method according to claim 1, characterized in that, The preset threshold for blasting vibration velocity in step 2 is: 8-12 cm / s for Class III surrounding rock and 5-8 cm / s for Class IV surrounding rock.

5. The method according to claim 4, characterized in that, In step 2, when using controlled blasting for excavation, the maximum charge per section is controlled between 5 and 15 kg, the cut location is far from the lateral rock pillar, and the micro-delay is ≥100 ms.

6. The method according to claim 1, characterized in that, The preset stability criteria are: the arch subsidence rate and the horizontal convergence rate are both ≤0.2mm / d for 7 consecutive days.

7. The method according to claim 1, characterized in that, The upper ventilation structure mentioned in step 3 includes air supply ducts, air supply shafts, and smoke exhaust ducts.

8. A tunnel overlapping chamber construction system for implementing the method according to any one of claims 1-7, characterized in that, include: The monitoring unit includes a total station, convergence meter, and blasting vibration meter deployed in the central diaphragm rock column and adjacent caverns, used to collect real-time data on the arch subsidence of the central diaphragm rock column, horizontal convergence data, and blasting vibration velocity data at the lateral rock columns. The data processing unit, connected to the monitoring unit, is used to receive and process monitoring data, calculate the deformation rate of the central rock column and compare it with the threshold in the preset stability judgment condition, and compare the measured blasting vibration velocity with the preset threshold. The control unit, connected to the data processing unit, is used to output process conversion instructions or blasting parameter adjustment instructions based on the comparison results.

9. The system according to claim 8, characterized in that, The monitoring unit also includes multi-point displacement gauges and / or stress gauges deployed at the central rock column to acquire deep deformation and / or stress state data of the central rock column.

10. The system according to claim 8, characterized in that, The process conversion instructions output by the control unit include: when the deformation data of the diaphragm rock column meets the preset stability judgment conditions, an instruction to allow the construction of secondary lining is issued; when the measured blasting vibration velocity exceeds the preset threshold, an instruction to reduce the single-stage charge and / or adjust the slotting position and / or increase the micro-delay blasting parameter adjustment is issued.

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