Partition asynchronous construction method for new tunnel crossing existing tunnel in plane

Abstract

The application discloses a kind of new tunnel and existing tunnel plane intersection partition asynchronous construction method, it is related to tunnel construction technical field.The method includes that the construction area of crossing section is sequentially divided into far end isolated excavation phase, small interval pre-reinforcement system construction phase, intersection section structure underpinning phase and system conversion closed loop phase along longitudinal direction;Isolated construction channel is formed in far end isolated excavation phase, and disturbance convergence of existing tunnel is monitored;In small interval pre-reinforcement system construction phase, composite pre-reinforcement system is formed by reinforcing anchor rod and concrete support, and stability is determined;In intersection section structure underpinning phase, vertical temporary steel support and concrete pier column are set by excavation, temporary traffic area is separated, and structure underpinning is completed;In system conversion closed loop phase, after determining independent keeping open condition, temporary support is removed, bottom primary support steel frame is fallen, and stratified backfilling is completed, and system conversion is completed.The application ensures that existing tunnel operation safety and traffic are not interrupted by partition asynchronous construction.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a method for asynchronous construction of newly built tunnels and existing tunnels at horizontal intersections. Background Technology

[0002] With the continuous construction of transportation infrastructure, the demand for three-dimensional intersections between new and existing tunnels is increasing, especially in projects such as urban subways and mountain railways, where new lines need to pass under or alongside existing operational tunnels. Such close-proximity construction faces enormous challenges in controlling surrounding rock disturbance, protecting existing structures, and ensuring traffic flow.

[0003] Currently, for the construction of at-grade intersections, segmented excavation, advanced support, or pipe jacking methods are commonly used. During construction, new tunnels are often excavated using the full-face or bench excavation method, while initial support is implemented and existing tunnels are temporarily reinforced. Some projects employ single-sidewall pilot tunnel methods or reserved core soil to control deformation and install temporary support systems to maintain traffic flow.

[0004] However, existing methods lack effective asynchronous isolation mechanisms between different work areas during construction. Disturbances such as blasting, demolition, and excavation can easily create cumulative effects in overlapping areas, making it difficult to control the vibration and deformation of existing tunnel structures. At the same time, temporary traffic conversion and structural stress system switching often occur simultaneously, resulting in significant interference between work processes. This not only increases construction risks but also leads to prolonged traffic interruptions in existing tunnels, making it difficult to meet the requirements of operational safety and traffic efficiency. Summary of the Invention

[0005] The main objective of this invention is to propose a zoned asynchronous construction method for new tunnels and existing tunnels that intersect at the same level, aiming to solve the problem in the prior art where it is difficult to balance the structural safety of existing tunnels and the maintenance of traffic flow due to overlapping procedures and superimposed disturbances.

[0006] To achieve the above objectives, the present invention proposes a zoned asynchronous construction method for new tunnels intersecting with existing tunnels at the same level. This zoned asynchronous construction method includes: The construction area of ​​the level crossing section is divided longitudinally into the far-end isolation tunneling phase, the small-clearance pre-reinforcement system construction phase, the intersection section structure replacement phase, and the system conversion closed-loop phase. A disturbance buffer zone is reserved between two adjacent construction phases, and disturbance operations are prohibited on both sides of the disturbance buffer zone at the same time. In the remote isolation tunneling phase, tunneling is carried out from the existing tunnel side toward the direction of the new tunnel and the initial support closure is completed to form a construction channel isolated from the existing tunnel. The structural response of the existing tunnel is monitored. When it is determined that the disturbance of the existing tunnel has converged, the construction phase of the small clearance pre-reinforcement system is entered. In the construction phase of the small clearance pre-reinforcement system, excavation and initial support are carried out on the side of the new tunnel adjacent to the existing tunnel, and reinforcement anchors and concrete supports are applied to the rock pillars in the middle to form a composite pre-reinforcement system. The stability of the composite pre-reinforcement system is monitored. When it is determined that the composite pre-reinforcement system meets the stability requirements, the cross section structure replacement phase is entered. During the structural replacement phase at the intersection, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the status of the temporary passage area are monitored. When the structural replacement is determined to be stable, the system transitions to the closed loop phase. During the closed-loop transition phase of the system, after determining that the newly built tunnel has the conditions for independent traffic maintenance, the vertical temporary steel support is removed and the initial support steel frame is lowered to the permanent foundation. The cavity behind the initial support is backfilled, and the closed-loop transition of the old and new tunnel systems is completed after stability verification.

[0007] In one embodiment, the remote isolation tunneling phase corresponds to the construction area where the excavation of the remote section of the new tunnel is carried out using construction adits; the small clearance pre-reinforcement system construction phase corresponds to the small clearance section between the new tunnel and the existing tunnel and the adjacent area; the intersection section structure replacement phase corresponds to the core area of ​​the plane intersection section; and the system conversion closed loop corresponds to the system conversion and finishing construction area.

[0008] In one embodiment, the width of the disturbance buffer zone is not less than 0.8m; the original surrounding rock or the sealed support is retained within the disturbance buffer zone, and no excavation or demolition work is carried out; when blasting, demolition or excavation work is being carried out on one side of the disturbance buffer zone, the same type of disturbance work is prohibited from being carried out on the other side of the disturbance buffer zone at the same time; the construction work time on both sides of the disturbance buffer zone is staggered by not less than one complete construction cycle.

[0009] In one embodiment, in the remote isolated tunneling phase, tunneling is carried out from the existing tunnel side towards the new tunnel and initial support closure is completed to form a construction passage isolated from the existing tunnel. The response of the existing tunnel structure is monitored, and when it is determined that the disturbance of the existing tunnel has converged, the step of entering the small clearance pre-reinforcement system construction phase includes: Vibration monitoring points were set up in the interlocking rock pillars and existing tunnel lining to monitor the blasting vibration velocity; Displacement monitoring points were set up at the existing tunnel arch, arch waist and sidewalls to monitor the displacement rate; When the continuous monitoring value of blasting vibration velocity is less than or equal to 15 cm / s and the displacement rate is less than 1 mm / d for 7 consecutive days, the existing tunnel disturbance is considered to have converged.

[0010] In one embodiment, during the construction phase of the small clearance pre-reinforcement system, excavation and initial support are carried out on the side of the new tunnel adjacent to the existing tunnel, and reinforcing anchors and concrete supports are applied to the interlocking rock pillars to form a composite pre-reinforcement system. The stability of the composite pre-reinforcement system is monitored, and when it is determined that the composite pre-reinforcement system meets the stability requirements, the step of proceeding to the cross-section structure replacement phase includes: The C20 concrete support was poured using a continuous, layered construction method, with each layer being 1.5m high. 1.2m formwork was used. 1.5m standardized steel formwork; After each layer of concrete reaches a strength of 15MPa, horizontal through holes with a diameter of 52-55mm are drilled within the layer thickness range. M20 early-strength cement mortar is injected into the horizontal through holes and Φ25 through anchor rods are inserted. After the grouting strength reaches 20MPa, install an Ω-shaped enlarged head pad at the end of the through anchor rod and apply a pre-tension force of 90kN. Stabilize the pressure for 2 minutes and lock it after the pressure drop is less than 5%. After locking for 24 hours, monitor the prestress loss rate. When the prestress loss rate exceeds 10%, perform compensatory tensioning. The concrete supports are stacked layer by layer, and the through-bolts are inserted layer by layer to form the composite pre-reinforcement system that interlocks and locks layer by layer.

[0011] In one embodiment, during the structural replacement phase at the intersection section, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. Once the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion includes: Two rows of lock anchor bolts are installed within 50cm of the outer edge of the demolition outline. The lock anchor bolts are Φ25 mortar anchor bolts, 4.5m long, with a row spacing of 1.0m, and arranged in a quincunx pattern. The lining of the retained section is reinforced with Φ22 mortar anchor bolts, the length of which is 4.5m and the spacing between them is 1.5m. Demolition shall be carried out using a hydraulic breaker or pneumatic drill for cold demolition. Blasting is strictly prohibited, and the length of a single demolition shall not exceed 5m. After demolition, the exposed initial support or rock surface of the existing tunnel should be immediately sealed with C20 concrete sprayed to a thickness of not less than 5cm.

[0012] In one embodiment, during the structural replacement phase at the intersection section, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. Once the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion further includes: I-beams or H-beams are selected as the columns for the vertical temporary steel supports, and the support spacing is matched with the spacing between the columns of the initial support steel frame. A C20 concrete pier column is poured at the bottom of the vertical temporary steel support, and the cross-sectional dimension of the concrete pier column is not less than 60cm. 60cm, the height is determined according to the clearance requirements of the temporary passage area; The clear width of the temporary passage area shall not be less than 3m; A steel pad and a limiting slot are provided on the top of the vertical temporary steel support. The bottom end of the initial support steel frame rests on the steel pad and is positioned by the limiting slot.

[0013] In one embodiment, during the structural replacement phase at the intersection section, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. Once the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion further includes: Strain gauges are attached to the columns of the vertical temporary steel support or axial force gauges are installed to monitor the axial stress of the vertical temporary steel support in real time. Record stress values ​​daily and calculate the daily stress variation rate. When the daily stress variation rate is greater than or equal to 5%, suspend the phase replacement construction of the cross section structure and carry out support reinforcement or unloading treatment. Fixed measuring points are set at both sides of the temporary passage area to measure the net width of the temporary passage area daily; When the clear width of the temporary passage area is less than 3m or when the road surface shows subsidence cracks, passage shall be suspended and the road surface shall be repaired. The structure is deemed stable when the daily stress variation rate of the vertical temporary steel support is less than 5% and the net width of the temporary passage area is greater than or equal to 3m for 7 consecutive days.

[0014] In one embodiment, during the closed-loop transition phase of the system, after determining that the newly constructed tunnel meets the conditions for independent passage, the steps of removing the vertical temporary steel support and lowering the initial support steel frame to the permanent foundation, backfilling the cavity behind the initial support, and completing the closed-loop transition between the old and new tunnel systems after stability verification include: The temporary passage area has a net width of 3m or more; The temporary passageway road surface is hardened with C20 concrete or paved with steel plates, and the road surface bearing capacity meets the 10t axial pressure of the rear axle of emergency vehicles. The temporary passage area is provided with an emergency escape space with a width of not less than 1.5m on one side; If the monitoring indicators of the initial support of the newly constructed tunnel and the aforementioned vertical temporary steel support remain stable for 7 consecutive days, and the displacement rate of the newly constructed tunnel is less than 0.5 mm / d, and the daily stress variation rate of the aforementioned vertical temporary steel support is less than 5%, then the newly constructed tunnel is qualified to maintain independent traffic flow.

[0015] In one embodiment, during the closed-loop transition phase of the system, after determining that the newly constructed tunnel meets the conditions for independent passage, the vertical temporary steel supports are removed and the initial support steel frame is lowered to the permanent foundation. The cavity behind the initial support is backfilled, and the process of completing the closed-loop transition between the old and new tunnel systems after stability verification further includes: Backfilling should be done using C20 concrete or excavated waste. Each backfill layer should not exceed 50cm in thickness, and should be compacted in layers by tamping or vibrating. The backfill compaction degree shall not be less than 90%; Backfilling work will be carried out after the newly built tunnel has the conditions for independent traffic control, and the backfilling operation will not occupy the space of the temporary passage area, thus completing the closed loop of the conversion between the old and new tunnel systems.

[0016] The technical solution of this invention divides the construction area of ​​the at-grade intersection section longitudinally into four sequential construction phases, and reserves a disturbance buffer zone between adjacent construction phases while prohibiting simultaneous disturbance operations. This allows for asynchronous implementation of remote isolation excavation, pre-reinforcement of the inter-rock pillar, replacement of existing structures, and system conversion. This effectively isolates the impact range of strong disturbance processes such as blasting and demolition, avoiding cumulative damage to the existing tunnel structure caused by superimposed disturbances. Simultaneously, by constructing a composite pre-reinforcement system of concrete supports, anchor bolts, and rock pillars in the small clearance section, the rigidity of the inter-rock pillar is enhanced, limiting the deformation of the surrounding rock during the subsequent demolition stage. Vertical temporary steel supports are set up at the intersection section to form a temporary passage area, enabling continuous passage of the existing tunnel during construction. After confirming that the new tunnel has the conditions for independent traffic maintenance, the temporary supports are removed and the permanent structure is lowered, ensuring a smooth transition of stress during the structural conversion process. This significantly improves the safety and traffic guarantee capabilities of at-grade intersection tunnel construction. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating an embodiment of the asynchronous construction method for the intersection of a newly constructed tunnel and an existing tunnel, provided by the present invention.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] Existing methods lack effective asynchronous isolation mechanisms between different work areas during construction. Disturbances such as blasting, demolition, and excavation can easily create cumulative effects in overlapping areas, making it difficult to control the vibration and deformation of existing tunnel structures. At the same time, temporary traffic conversion and structural stress system switching often occur simultaneously, resulting in significant interference between work processes. This not only increases construction risks but also leads to prolonged traffic interruptions in existing tunnels, making it difficult to meet the requirements of operational safety and traffic efficiency.

[0024] To address this technical problem, this invention proposes a zoned asynchronous construction method for new tunnels that intersect with existing tunnels at different planes.

[0025] Please see Figure 1 In one embodiment of the present invention, the method for asynchronous construction of a newly built tunnel intersecting with an existing tunnel at different planes includes: Step S10: The construction area of ​​the level crossing section is divided longitudinally into the far-end isolation tunneling phase, the small-clearance pre-reinforcement system construction phase, the cross section structure replacement phase, and the system conversion closed-loop phase. A disturbance buffer zone is reserved between two adjacent construction phases, and disturbance operations are prohibited on both sides of the disturbance buffer zone at the same time. Step S20: In the remote isolation tunneling phase, tunneling is carried out from the existing tunnel side toward the direction of the new tunnel and the initial support closure is completed to form a construction channel isolated from the existing tunnel. The structural response of the existing tunnel is monitored. When it is determined that the disturbance of the existing tunnel has converged, the construction phase of the small clearance pre-reinforcement system is entered. Step S30: In the construction phase of the small clearance pre-reinforcement system, excavation and initial support are carried out on the side of the new tunnel adjacent to the existing tunnel, and reinforcement anchors and concrete supports are applied to the rock pillars in the middle to form a composite pre-reinforcement system. The stability of the composite pre-reinforcement system is monitored. When it is determined that the composite pre-reinforcement system meets the stability requirements, the cross section structure replacement phase is entered. Step S40: In the structural replacement phase of the intersection section, the existing lining is dismantled in sections and a new tunnel is excavated in a non-blasting manner. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on the top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the status of the temporary passage area are monitored. When it is determined that the structural replacement is stable, the system transitions to the closed loop phase. Step S50: In the closed-loop phase of the system conversion, after determining that the newly built tunnel has the conditions for independent traffic maintenance, the vertical temporary steel support is removed and the initial support steel frame is lowered to the permanent foundation. The cavity behind the initial support is backfilled, and the closed-loop conversion of the old and new tunnel systems is completed after stability verification.

[0026] It should be noted that in this embodiment, the "at-grade intersection construction area" refers to the construction impact section where the newly built tunnel and the existing tunnel intersect and run parallel at close range in the plane. The "far-end isolation tunneling phase" is the preliminary construction area that is far from the existing tunnel and has relatively independent disturbance; the "small clearance pre-reinforcement system construction phase" is the area where the newly built tunnel is adjacent to the existing tunnel and has a relatively thin rock pillar in between; the "intersection structural replacement phase" is the core area where the two tunnels intersect spatially, involving the removal of the existing lining and load transfer; the "system conversion closed-loop phase" is the final section where the load-bearing system is converted from temporary support to permanent structure. The "disturbance buffer zone" is the reserved original surrounding rock or supported area, serving as an isolation zone between adjacent construction phases. "Initial support" refers to the initial support; "intermediate rock pillar" refers to the rock mass between the two tunnels.

[0027] Specifically, by dividing the tunnel longitudinally into zones and reserving buffer zones, "asynchronous" construction was achieved. During long-distance excavation, the presence of isolation channels limited disturbances, preventing them from being directly transmitted to the existing tunnel. After monitoring and confirmation of convergence, the tunnel transitioned to a smaller clearance section. At this point, the interlocking rock pillars were reinforced to form a pre-strengthened system, enhancing the load-bearing capacity and providing a safety reserve for the subsequent removal of the existing lining. The structural replacement at the intersection section involved non-blasting excavation and the creation of temporary passageways using temporary supports, ensuring uninterrupted traffic flow in the existing tunnel. The initial steel frame load was temporarily applied to the temporary supports, forming a stable closed loop. Finally, during the closed-loop system transition phase, once the newly constructed tunnel possessed independent load-bearing and passage conditions, the temporary supports were gradually removed and the bottom steel frame was lowered, completing the load system transition. This entire process asynchronousized high-risk cross-operations, avoiding the superposition of disturbances and ensuring the structural and operational safety of the existing tunnel.

[0028] More specifically: During implementation, the construction area is first divided into four sequential construction phases based on the geological conditions of the level crossing and the tunnel clearance. A buffer zone with a width not less than the spacing of one steel frame (e.g., not less than 0.8m) is demarcated between two phases, and simultaneous blasting, demolition, or other disturbance operations on both sides of the buffer zone are strictly prohibited. At the far end of the isolated excavation phase, a working face is opened using the existing tunnel's lateral construction adits. The far end section of the new tunnel is excavated using conventional drill-and-blast methods, and initial support with shotcrete mesh is promptly applied to seal the surrounding rock, forming an independent construction passage. Vibration and displacement sensors placed in the interlocking rock pillars and existing lining are used to monitor the existing tunnel response in real time. Only after the vibration velocity and displacement rate convergence criteria are met can the next phase be initiated. After entering the small-clearance pre-reinforcement system construction phase, bench excavation was carried out on the side adjacent to the existing tunnel to complete the initial support. Simultaneously, mortar anchors were installed on the sidewall system of the interlocking rock pillar, alternating with the initial support shotcrete work. For locally weak sections of the interlocking rock pillar, concrete support walls were poured in layers, and prestressed anchors were drilled through the perforations to ensure that the concrete support, anchors, and rock pillar shared the load. Concrete strength, anchor prestress, and existing tunnel displacement were monitored. When the strength of the concrete support test blocks cured under the same conditions reached more than 80% of the design strength, the 24-hour prestress loss rate of the through-hole prestressed anchors was less than 10% and tended to stabilize, and the existing tunnel displacement rate was less than 1 mm / d for 7 consecutive days, the composite pre-reinforcement system was deemed to meet the stability requirements, and the system entered the cross-section structural replacement phase. During construction at the intersection section, anchor bolts were first installed around the existing lining. The existing lining was then cold-removed in sections, each no more than 5 meters long. Immediately after removal, the exposed surfaces were sealed with shotcrete. Subsequently, the new tunnel cross-section was enlarged using cold excavation methods such as hydraulic breakers, with strict control over the advance per cycle. After enlargement, temporary vertical steel supports were promptly erected and piers were poured to create a temporary passageway with a net width of at least 3 meters. When erecting the initial steel frame, its bottom end was temporarily supported on the steel pad and locating groove at the top of the steel support, forming a closed loop to prevent the steel frame from directly falling to the bottom and causing disturbance. The stress of the steel supports and the dimensions of the passageway were monitored in real time to ensure that the daily variation in support stress was less than 5% and that the net width of the passageway met the requirements. The tunnel was considered stable after 7 days of stabilization. Subsequently, the system conversion closed-loop phase was entered. First, the bearing capacity of the temporary passage area, emergency avoidance space, and monitoring data of the initial support and bracing were checked to confirm that the new tunnel had the conditions for independent traffic maintenance. Then, the vertical temporary steel supports were cut off in sections from top to bottom, and the bottom of the steel frame was simultaneously sectioned and connected to the invert arch foundation. After monitoring that the displacement rate of the new tunnel was less than 0.5 mm / d for 7 consecutive days, the cavity behind the initial support was backfilled in layers with C20 concrete or waste slag. Each layer was no more than 50 cm thick and the compaction degree was no less than 90%. The backfilling did not occupy the temporary passage area. Finally, the conversion of the old and new tunnel systems was completed through verification of displacement, compaction, and traffic maintenance indicators.

[0029] In embodiments of the present invention, the remote isolation tunneling phase corresponds to the construction area where the excavation of the remote section of the new tunnel is carried out using construction adits; the small clearance pre-reinforcement system construction phase corresponds to the small clearance section between the new tunnel and the existing tunnel and the adjacent area; the intersection structure replacement phase corresponds to the core area of ​​the plane intersection section; and the system conversion closed loop corresponds to the system conversion and finishing construction area.

[0030] It should be noted that the physical scope of each construction phase needs to be defined to facilitate on-site construction zoning management.

[0031] Specifically: After clarifying the corresponding relationships between each phase area, construction personnel can organize operations independently by area, and use buffer zones to achieve spatial isolation. The excavation of the far section is not directly constrained by the adjacent existing tunnels, and can quickly form a passage; the small clearance section is pre-reinforced to improve the stability of the rock pillar; the core area of ​​the intersection section undergoes structural transformation; the finishing area completes the closed loop of the system, with clear functions for each area, reducing mutual interference.

[0032] More specifically: The distal isolation excavation phase includes the section of the newly constructed tunnel after entering from the construction adit, up to the section approaching the small clearance area, where the existing tunnel experiences minimal disturbance during construction. The small clearance pre-reinforcement system construction phase covers the section where the rock column thickness between the two tunnels is less than one tunnel diameter, where grouting anchors and concrete supports are constructed. The intersection section structural replacement phase is the area where the newly constructed tunnel intersects with the existing tunnel in the plane, and where the existing lining needs to be removed. The system conversion closed-loop phase covers the section where temporary supports are removed, steel frames are permanently lowered, and backfilling occurs; typically, this is the intersection section and its surrounding areas.

[0033] In embodiments of the present invention, the width of the disturbance buffer zone is not less than 0.8m; the original surrounding rock or the sealed support is retained within the disturbance buffer zone, and no excavation or demolition work is carried out; when blasting, demolition or excavation work is being carried out on one side of the disturbance buffer zone, the same type of disturbance work is prohibited from being carried out on the other side of the disturbance buffer zone at the same time; the construction work time on both sides of the disturbance buffer zone is staggered by not less than one complete construction cycle.

[0034] It should be noted that "complete construction cycle" refers to the work cycle from excavation to the completion of one advance of the initial support, such as the time for one cycle of drilling and blasting, muck removal, and support.

[0035] Specifically: by setting up a buffer zone of sufficient width and retaining its original state, the propagation of disturbances from adjacent construction phases is physically isolated; supplemented by staggered control in time, the superposition of vibrations and stress wave interference caused by simultaneous disturbances from different work faces can be completely eliminated, ensuring the stability of existing tunnels and supported areas.

[0036] More specifically: The boundary of the buffer zone must be marked on-site, with a width of no less than 0.8m, and excavation is strictly prohibited within the zone. When blasting is carried out in the far-end tunneling phase, all excavation and demolition work in the small-clearance pre-reinforcement phase must be stopped. Work in the small-clearance phase can only begin after blasting is completed, smoke extraction and safety inspections are finished, and a complete cycle has been completed. This ensures sufficient energy release and stable displacement before proceeding to the next phase.

[0037] In an embodiment of the present invention, in the remote isolated tunneling phase, tunneling is carried out from the existing tunnel side toward the direction of the newly built tunnel and the initial support closure is completed to form a construction passage isolated from the existing tunnel. The response of the existing tunnel structure is monitored, and when it is determined that the disturbance of the existing tunnel has converged, the step of entering the small clearance pre-reinforcement system construction phase includes: Step S201: Vibration monitoring points are set up in the interlocking rock pillars and existing tunnel lining to monitor the blasting vibration velocity; Step S202: Install displacement monitoring points at the existing tunnel arch, arch waist and sidewalls to monitor the displacement rate; Step S203: When the continuous monitoring value of blasting vibration velocity is less than or equal to 15 cm / s and the displacement rate is less than 1 mm / d for 7 consecutive days, the existing tunnel disturbance is determined to converge.

[0038] It should be noted that blasting vibration velocity monitoring typically uses velocity sensors or seismographs, while displacement rate monitoring uses convergence meters, total stations, etc. The stated 15 cm / s is a general reference value for safety control standards in existing tunnels and can be adjusted based on the tunnel structural condition assessment.

[0039] Specifically: by quantifying the two indicators of vibration and deformation and setting the convergence period, we can scientifically determine whether the disturbance of the far-end tunneling has been sufficiently attenuated, and ensure that the existing tunnel is restored to stability before the construction of the adjacent section, so as to avoid the superposition of residual stress or deformation into subsequent sensitive operations.

[0040] More specifically: monitoring points are set up on the existing tunnel lining section closest to the blast source, as well as on the surface of the intercalated rock pillars. Peak vibration velocity is recorded after each blast and monitored continuously; displacement monitoring points are set up on the existing tunnel arch, the two side arch waists, and the sidewalls, with daily readings. When the continuously observed vibration velocity does not exceed 15 cm / s, and the displacement rate has dropped to below 1 mm / d and remained below 1 mm / d for 7 days, the disturbance convergence is confirmed, the warning for that phase can be lifted, and the pre-reinforcement phase construction can be initiated.

[0041] In an embodiment of the present invention, during the construction phase of the small clearance pre-reinforcement system, excavation and initial support are carried out on the side of the new tunnel adjacent to the existing tunnel, and reinforcing anchors and concrete supports are applied to the interlocking rock pillars to form a composite pre-reinforcement system. The stability of the composite pre-reinforcement system is monitored, and when it is determined that the composite pre-reinforcement system meets the stability requirements, the step of proceeding to the cross-section structure replacement phase includes: Step S301: C20 concrete supports are poured using a continuous layered construction method, with each layer having a pouring height of 1.5m. 1.2m formwork is used. 1.5m standardized steel formwork; Step S302: After the concrete strength of each layer reaches 15MPa, horizontal through holes with a diameter of 52-55mm are drilled within the layer thickness range. M20 early-strength cement mortar is injected into the horizontal through holes and Φ25 through anchor rods are inserted. Step S303: After the grouting strength reaches 20MPa, install an Ω-shaped enlarged head pad at the end of the through anchor rod and apply a pre-tension force of 90kN. Stabilize the pressure for 2 minutes and lock it after the pressure drop is less than 5%. Step S304: After locking for 24 hours, monitor the prestress loss rate. When the prestress loss rate exceeds 10%, perform compensatory tensioning. Step S305: The concrete supports are stacked layer by layer and the through anchors are inserted layer by layer to form the composite pre-reinforcement system that is layered, interlocked, and locked layer by layer.

[0042] It should be noted that: "C20 concrete" refers to concrete with a strength grade of 20MPa; "M20 early-strength cement mortar" refers to quick-hardening mortar with a compressive strength of 20MPa; "Ω-shaped enlarged head pad" refers to an anchor pad with enlarged ends to increase the bearing area; "layered interlocking" refers to the spatially staggered connection of each layer of concrete support and anchor rod to form an integral load-bearing structure.

[0043] Specifically, by constructing the concrete support wall in layers and applying prestress in a timely manner at each layer, the intercalated rock pillars are actively constrained, forming high load-bearing stiffness in advance. This effectively limits the deformation of the rock pillars during the subsequent removal of the existing lining, preventing damage to the existing tunnel structure. Layer-by-layer locking and compensating tension control the loss of prestress, ensuring the long-term effectiveness of the reinforcement system.

[0044] More specifically: After cleaning the weak sections of the interlocking rock column, formwork is erected, and C20 concrete is poured layer by layer from the bottom, each layer being 1.5m high, and compacted by vibrator. When the strength of the test blocks cured under the same conditions reaches 15MPa, horizontal holes with a diameter of 52-55mm are drilled at the designed angle in the wall thickness direction. After cleaning the holes, M20 mortar is injected, and then Φ25 fine-rolled threaded steel bars are inserted as through anchors. After the mortar has finally set and reached a strength of 20MPa, a pad is installed, and a preload of 90kN is applied using a through-hole jack. The load is held for 2 minutes, and the nuts are tightened to lock the structure after the oil pressure drop does not exceed 5%. The preload is tested after 24 hours. If the loss exceeds 10%, the preload is replenished to the design value. This process is repeated until the top of the wall, ultimately forming a composite structure of multiple prestressed anchors and concrete walls.

[0045] In an embodiment of the present invention, during the structural replacement phase at the intersection section, the existing lining is dismantled in sections and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. Once the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion includes: Step S401: Install two rows of lock anchor bolts within a 50cm radius outside the demolition outline. The lock anchor bolts are Φ25 mortar anchor bolts, 4.5m long, with a row spacing of 1.0m, arranged in a quincunx pattern. Step S402: Reinforce the lining of the retained section with Φ22 mortar anchor bolts. The length of the Φ22 mortar anchor bolts is 4.5m and the spacing between them is 1.5m. Step S403: Demolition shall be carried out by cold demolition using a hydraulic breaker or pneumatic drill. Explosive demolition is strictly prohibited, and the length of a single demolition shall not exceed 5m. Step S404: Immediately after demolition, spray C20 concrete to seal the exposed initial support or rock surface of the existing tunnel, with a spray thickness of not less than 5cm.

[0046] It should be noted that: "locking anchor bolts" refers to reinforcing anchor bolts arranged around the demolition opening to prevent the surrounding rock from becoming unstable at the opening; "cold demolition" refers to a mechanical demolition method that does not use explosives.

[0047] Specifically: by installing anchor bolts at the edge of the demolition area and reinforcing the retained section, a reliable self-supporting arch of the rock mass was constructed, limiting the relaxation range caused by demolition; the cold demolition method avoided vibration, the single demolition length was limited to prevent excessive unloading at one time, and the instant sealing with shotcrete prevented weathering and further loosening of the surrounding rock, ensuring the safety of the remaining structure of the existing tunnel.

[0048] More specifically: Following the demolition outline, lay out two rows of Φ25 anchor bolts 50cm outwards, spaced 1.0m apart in a staggered pattern, 4.5m long, and fully grouted. Behind the demolition area, install Φ22 reinforcing anchor bolts on the remaining lining, spaced 1.5m apart. Use a hydraulic breaker for layered removal, with each removal step not exceeding 5m longitudinally. Immediately after demolition, spray the exposed surface with 5cm thick C20 concrete to form a protective layer.

[0049] In an embodiment of the present invention, during the structural replacement phase at the intersection section, the existing lining is dismantled in sections and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. When the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion further includes: Step S410: Select I-beams or H-beams as the columns of the vertical temporary steel supports, and match the spacing between the supports with the spacing between the initial support steel frames. Step S420: Cast C20 concrete piers at the bottom of the vertical temporary steel supports. The cross-sectional dimensions of the concrete piers shall not be less than 60 cm². 60cm, the height is determined according to the clearance requirements of the temporary passage area; Step S430: The net width of the temporary passage area shall not be less than 3m; Step S440: A steel pad and a limiting slot are installed on the top of the vertical temporary steel support. The bottom end of the initial support steel frame rests on the steel pad and is positioned by the limiting slot.

[0050] It should be noted that "frame spacing" refers to the distance between two adjacent steel frames; temporary steel supports serve as temporary supports for the initial steel frames, transferring the load to the pier foundation.

[0051] Specifically: the use of vertical supports that match the spacing of the initial steel frame ensures that each steel frame has a reliable support point, forming a continuous closed loop; the piers provide a stable foundation, and the positioning of steel pads and slots ensures the installation accuracy of the steel frame and the uniformity of load transfer, making the temporary passage area structurally stable and able to safely maintain traffic.

[0052] More specifically: H-beam steel columns with the same spacing as the initial steel frame design (e.g., 0.8m) are selected, and the bottom of the columns are connected to the pre-cast C20 concrete pier column embedded parts. The pier column cross-section is 60cm. The top elevation is 60cm, and the clearance height is determined according to the clearance requirements for passage. A 20mm thick steel plate is welded to the top of the column, and a limiting groove is welded on it. When installing the initial support steel frame, the bottom feet of the steel frame are inserted into the groove and placed on the plate, and then welded to fix it, forming a stable temporary support.

[0053] In an embodiment of the present invention, during the structural replacement phase at the intersection section, the existing lining is dismantled in sections and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. When the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion further includes: Step S41: Attach strain gauges or install axial force gauges on the columns of the vertical temporary steel support to monitor the axial stress of the vertical temporary steel support in real time. Step S42: Record the stress value daily and calculate the daily stress variation rate. When the daily stress variation rate is greater than or equal to 5%, suspend the phase replacement construction of the cross section structure and carry out support reinforcement or unloading treatment. Step S43: Set fixed measuring points on both sides of the temporary passage area and measure the net width of the temporary passage area daily; Step S44: When the net width of the temporary passage area is less than 3m or the road surface shows subsidence cracks, traffic shall be suspended and the road surface shall be repaired. Step S45: When the daily stress variation rate of the vertical temporary steel support is less than 5% and the net width of the temporary passage area is greater than or equal to 3m for 7 consecutive days, the structural support is determined to be stable.

[0054] It should be noted that: the daily stress variation rate refers to the percentage change in stress on a given day relative to the previous day; structural support stability refers to the state in which the stress and deformation of the support system tend to be stable.

[0055] Specifically: Real-time stress monitoring and spatial dimension detection allow for dynamic monitoring of the support system's operational status. Exceeding the daily stress variation rate indicates a sudden change in loading or a risk of support instability, requiring timely intervention; monitoring of the passageway dimensions ensures traffic safety. Seven consecutive days of stability serve as the criterion for determining the completion of the replacement, providing ample safety margin.

[0056] More specifically: Attach resistance strain gauges to the middle surface of each steel support and connect them to a data acquisition device. Record stress values ​​daily and calculate the daily stress variation rate. If the daily variation rate is found to be ≥5%, immediately stop excavation and demolition work, inspect the support connection nodes, and add diagonal bracing or jacks for unloading if necessary. Simultaneously, fix reflective plates at the waistline positions on both sides of the passageway and use a distance measuring instrument to measure the net width daily, ensuring it is not less than 3m; if compression deformation occurs, quickly repair the road surface, and proceed to the next phase only after confirming stability for 7 days.

[0057] In an embodiment of the present invention, during the closed-loop transition phase of the system, after determining that the newly constructed tunnel possesses independent traffic maintenance conditions, the steps of dismantling the vertical temporary steel support and lowering the initial support steel frame to the permanent foundation, backfilling the cavity behind the initial support, and completing the closed-loop transition between the old and new tunnel systems after stability verification include: Step S501, the net width of the temporary passage area is greater than or equal to 3m; Step S502: The temporary passageway road surface is hardened with C20 concrete or paved with steel plates, and the road surface bearing capacity meets the 10t axial pressure of the rear axle of the emergency vehicle. Step S503: The temporary passage area is provided with an emergency escape space with a width of not less than 1.5m on one side; Step S504: If the monitoring indicators of the initial support of the newly built tunnel and the vertical temporary steel support are stable for 7 consecutive days, and the displacement rate of the newly built tunnel is less than 0.5 mm / d, and the daily stress variation rate of the vertical temporary steel support is less than 5%, then the newly built tunnel has the conditions for independent passage.

[0058] It should be noted that "independent traffic maintenance conditions" refers to the requirement that a newly constructed tunnel structure can independently bear the load and ensure the safety of traffic function without relying on temporary supports.

[0059] Specifically, the confirmed conditions ensured that when the temporary supports were removed, the initial tunnel support and surrounding rock had formed a stable load-bearing arch, and that the passage space and emergency functions were complete and could withstand the expected traffic load, preventing sudden instability after the supports were removed.

[0060] More specifically: Before entering the system transition phase, a comprehensive inspection of the temporary passage area must be conducted. The road surface must be a C20 concrete surface layer or a hardened structure with steel plates, and its ability to withstand 10t axial pressure must be verified through loading tests. The width of the passage area must be no less than 3m, with a buffer zone of no less than 1.5m wide reserved on one side. Simultaneously, monitoring data for 7 consecutive days must be exported to confirm that the initial support displacement rate is less than 0.5mm / d and the daily stress variation rate of the steel supports is less than 5%. Once all conditions are met, the area is deemed suitable for independent passage maintenance.

[0061] In an embodiment of the present invention, after determining that the newly built tunnel has the conditions for independent passage during the system conversion closed-loop phase, the vertical temporary steel support is removed and the initial support steel frame is lowered to the permanent foundation. The cavity behind the initial support is backfilled. After stability verification, the steps of completing the conversion closed-loop of the old and new tunnel systems further include: Step S510: Backfill with C20 concrete or excavated waste. Step S520: Each backfill thickness shall not exceed 50cm, and shall be compacted in layers by tamping or vibrating. Step S530: The backfill compaction degree shall not be less than 90%; Step S540: Backfilling is carried out after the newly built tunnel has the conditions for independent passage, and the backfilling operation does not occupy the space of the temporary passage area, thus completing the closed loop of the conversion between the old and new tunnel systems.

[0062] It should be noted that "density" refers to the ratio of the dry density of the backfill material after compaction to its maximum dry density.

[0063] Specifically: layered backfilling ensures a dense compaction effect, preventing cavities from causing loosening of the surrounding rock or creating channels for groundwater seepage. Backfilling is carried out only after conditions for independent traffic control are met, without disrupting traffic. Furthermore, the backfilling operation is confined to the space behind the support structure, ensuring uninterrupted traffic throughout the entire system conversion process.

[0064] More specifically: C20 concrete or screened waste is delivered to the cavity behind the steel frame using an excavator or loader. Each layer is loosely laid with a thickness of 40cm, and compacted with a small vibratory tamper or immersion vibrator. The next layer is laid only after the compaction degree reaches 90%, until the cavity is filled. The backfill area is controlled between the outer edge of the initial support and the surrounding rock, and must not encroach on the temporary passage zone boundary. Finally, the tunnel clearance, initial support deformation, and density are comprehensively checked. Once the design standards are confirmed, the system is considered closed-loop.

[0065] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A method for asynchronous construction in zones where a newly constructed tunnel intersects with an existing tunnel at the same level, characterized in that, The method for asynchronous construction of newly built tunnels intersecting with existing tunnels at the same level includes: The construction area of ​​the level crossing section is divided longitudinally into the far-end isolation tunneling phase, the small-clearance pre-reinforcement system construction phase, the intersection section structure replacement phase, and the system conversion closed-loop phase. A disturbance buffer zone is reserved between two adjacent construction phases, and disturbance operations are prohibited on both sides of the disturbance buffer zone at the same time. In the remote isolation tunneling phase, tunneling is carried out from the existing tunnel side toward the direction of the new tunnel and the initial support closure is completed to form a construction channel isolated from the existing tunnel. The structural response of the existing tunnel is monitored. When it is determined that the disturbance of the existing tunnel has converged, the construction phase of the small clearance pre-reinforcement system is entered. In the construction phase of the small clearance pre-reinforcement system, excavation and initial support are carried out on the side of the new tunnel adjacent to the existing tunnel, and reinforcement anchors and concrete supports are applied to the rock pillars in the middle to form a composite pre-reinforcement system. The stability of the composite pre-reinforcement system is monitored. When it is determined that the composite pre-reinforcement system meets the stability requirements, the cross section structure replacement phase is entered. During the structural replacement phase at the intersection, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the engineering area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the status of the temporary passage area are monitored. When the structural replacement is determined to be stable, the system transitions to the closed loop phase. During the closed-loop transition phase of the system, after determining that the newly built tunnel has the conditions for independent traffic maintenance, the vertical temporary steel support is removed and the initial support steel frame is lowered to the permanent foundation. The cavity behind the initial support is backfilled, and the closed-loop transition of the old and new tunnel systems is completed after stability verification.

2. The method for asynchronous construction of newly built tunnels intersecting with existing tunnels at the same level, as described in claim 1, is characterized in that... The term "far-end isolation excavation phase" corresponds to the construction area where the far-end section of a new tunnel is excavated using construction adits; the term "small clearance pre-reinforcement system construction phase" corresponds to the small clearance section between the new tunnel and the existing tunnel and the adjacent area; the term "intersection structure replacement phase" corresponds to the core area of ​​the plane intersection section; and the term "system conversion closed loop" corresponds to the system conversion and finishing construction area.

3. The method for asynchronous construction of newly built tunnels and existing tunnels at horizontal intersections as described in claim 1, characterized in that, The width of the disturbance buffer zone shall not be less than 0.8m; the original surrounding rock or the sealed support shall be retained within the disturbance buffer zone, and no excavation or demolition work shall be carried out; when blasting, demolition or excavation work is being carried out on one side of the disturbance buffer zone, the same type of disturbance work shall not be carried out on the other side of the disturbance buffer zone at the same time; the construction work time on both sides of the disturbance buffer zone shall be staggered by no less than one complete construction cycle.

4. The method for asynchronous construction of newly built tunnels and existing tunnels at horizontal intersections as described in claim 1, characterized in that, In the remote isolation tunneling phase, tunneling is carried out from the existing tunnel side towards the new tunnel direction, and initial support closure is completed to form a construction passage isolated from the existing tunnel. The response of the existing tunnel structure is monitored. When it is determined that the disturbance of the existing tunnel has converged, the steps to enter the small clearance pre-reinforcement system construction phase include: Vibration monitoring points were set up in the interlocking rock pillars and existing tunnel lining to monitor the blasting vibration velocity; Displacement monitoring points were set up at the existing tunnel arch, arch waist and sidewalls to monitor the displacement rate; When the continuous monitoring value of blasting vibration velocity is less than or equal to 15 cm / s and the displacement rate is less than 1 mm / d for 7 consecutive days, the existing tunnel disturbance is considered to have converged.

5. The method for asynchronous construction of newly built tunnels intersecting with existing tunnels at the same level, as described in claim 1, is characterized in that... In the construction phase of the small clearance pre-reinforcement system, excavation and initial support are carried out on the side of the new tunnel adjacent to the existing tunnel, and reinforcing anchors and concrete supports are applied to the interlocking rock pillars to form a composite pre-reinforcement system. The stability of the composite pre-reinforcement system is monitored. When it is determined that the composite pre-reinforcement system meets the stability requirements, the steps of proceeding to the cross-section structure replacement phase include: The C20 concrete support was poured using a continuous, layered construction method, with each layer being 1.5m high. 1.2m formwork was used. 1.5m standardized steel formwork; After each layer of concrete reaches a strength of 15MPa, horizontal through holes with a diameter of 52-55mm are drilled within the layer thickness range. M20 early-strength cement mortar is injected into the horizontal through holes and Φ25 through anchor rods are inserted. After the grouting strength reaches 20MPa, install an Ω-shaped enlarged head pad at the end of the through anchor rod and apply a pre-tension force of 90kN. Stabilize the pressure for 2 minutes and lock it after the pressure drop is less than 5%. After locking for 24 hours, monitor the prestress loss rate. When the prestress loss rate exceeds 10%, perform compensatory tensioning. The concrete supports are stacked layer by layer, and the through-bolts are inserted layer by layer to form the composite pre-reinforcement system that interlocks and locks layer by layer.

6. The method for asynchronous construction of newly built tunnels intersecting with existing tunnels at the same level, as described in claim 1, is characterized in that... In the structural replacement phase at the intersection, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the project area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. Once the structural replacement is determined to be stable, the steps for entering the closed-loop phase of the system conversion include: Two rows of lock anchor bolts are installed within 50cm of the outer edge of the demolition outline. The lock anchor bolts are Φ25 mortar anchor bolts, 4.5m long, with a row spacing of 1.0m, and arranged in a quincunx pattern. The lining of the retained section is reinforced with Φ22 mortar anchor bolts, the length of which is 4.5m and the spacing between them is 1.5m. Demolition shall be carried out using a hydraulic breaker or pneumatic drill for cold demolition. Blasting is strictly prohibited, and the length of a single demolition shall not exceed 5m. After demolition, the exposed initial support or rock surface of the existing tunnel should be immediately sealed with C20 concrete sprayed to a thickness of not less than 5cm.

7. The method for asynchronous construction of newly built tunnels and existing tunnels at horizontal intersections as described in claim 6, characterized in that, In the structural replacement phase at the intersection, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the project area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. Once the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion further includes: I-beams or H-beams are selected as the columns for the vertical temporary steel supports, and the support spacing is matched with the spacing between the columns of the initial support steel frame. A C20 concrete pier column is poured at the bottom of the vertical temporary steel support, and the cross-sectional dimension of the concrete pier column is not less than 60cm. The height is 60cm, determined according to the clearance requirements of the temporary passage area. The clear width of the temporary passage area shall not be less than 3m; A steel pad and a limiting slot are provided on the top of the vertical temporary steel support. The bottom end of the initial support steel frame rests on the steel pad and is positioned by the limiting slot.

8. The method for asynchronous construction of newly built tunnels and existing tunnels at horizontal intersections as described in claim 7, characterized in that, In the structural replacement phase at the intersection, the existing lining is dismantled in sections, and a new tunnel is excavated using a non-blasting method. Vertical temporary steel supports and concrete piers are installed to divide the project area into a temporary passage area and a construction work area. The initial support steel frame is temporarily supported on top of the vertical temporary steel supports to form a closed loop. The stress on the vertical temporary steel supports and the state of the temporary passage area are monitored. Once the structural replacement is determined to be stable, the step of entering the closed-loop phase of the system conversion further includes: Strain gauges are attached to the columns of the vertical temporary steel support or axial force gauges are installed to monitor the axial stress of the vertical temporary steel support in real time. Record stress values ​​daily and calculate the daily stress variation rate. When the daily stress variation rate is greater than or equal to 5%, suspend the phase replacement construction of the cross section structure and carry out support reinforcement or unloading treatment. Fixed measuring points are set at both sides of the temporary passage area to measure the net width of the temporary passage area daily; When the clear width of the temporary passage area is less than 3m or when the road surface shows subsidence cracks, passage shall be suspended and the road surface shall be repaired. The structure is deemed stable when the daily stress variation rate of the vertical temporary steel support is less than 5% and the net width of the temporary passage area is greater than or equal to 3m for 7 consecutive days.

9. The method for asynchronous construction of newly built tunnels intersecting with existing tunnels at the same level, as described in claim 1, is characterized in that... In the closed-loop phase of the system conversion, after determining that the newly built tunnel has the conditions for independent traffic maintenance, the vertical temporary steel supports are removed and the initial support steel frame is lowered to the permanent foundation. The cavity behind the initial support is backfilled. After stability verification, the steps to complete the closed-loop conversion of the old and new tunnel systems include: The temporary passage area has a net width of 3m or more; The temporary passageway road surface is hardened with C20 concrete or paved with steel plates, and the road surface bearing capacity meets the 10t axial pressure of the rear axle of emergency vehicles. The temporary passage area is provided with an emergency escape space with a width of not less than 1.5m on one side; If the monitoring indicators of the initial support of the newly constructed tunnel and the aforementioned vertical temporary steel support remain stable for 7 consecutive days, and the displacement rate of the newly constructed tunnel is less than 0.5 mm / d, and the daily stress variation rate of the aforementioned vertical temporary steel support is less than 5%, then the newly constructed tunnel is qualified to maintain independent traffic flow.

10. The method for asynchronous construction of newly built tunnels intersecting with existing tunnels at the same level as described in claim 1, characterized in that, In the closed-loop phase of the system conversion, after determining that the newly built tunnel has the conditions for independent traffic maintenance, the vertical temporary steel support is removed and the initial support steel frame is lowered to the permanent foundation. The cavity behind the initial support is backfilled. After stability verification, the steps to complete the closed-loop conversion of the old and new tunnel systems also include: Backfilling should be done using C20 concrete or excavated waste. Each backfill layer should not exceed 50cm in thickness, and should be compacted in layers by tamping or vibrating. The backfill compaction degree shall not be less than 90%; Backfilling work will be carried out after the newly built tunnel has the conditions for independent traffic control, and the backfilling operation will not occupy the space of the temporary passage area, thus completing the closed loop of the conversion between the old and new tunnel systems.

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