Large-span multi-free-face inclined shaft-to-main-tunnel top-brushing construction method

Abstract

The invention discloses a large-span multi-free-face inclined shaft turning-to-main-hole top-lifting construction method, and relates to the technical field of highway tunnel engineering construction, and the method comprises the following steps: step 1, inclined shaft lifting section construction: when an inclined shaft is constructed to a preset lifting starting point pile number, the slope is adjusted to + 12.67%, uphill excavation is performed to a cross pile number, an arch frame is lifted by 12.67 cm every 1 m footage, and the slope is adjusted to + 12.67%; the top elevation of the inclined shaft is 50cm higher than the designed top elevation of the main hole; and 2, reinforcing support at the intersection: additionally arranging a special-shaped arch frame temporary support at the intersection section of the inclined shaft and the main hole, connecting with the vertical steel frames on the two sides through connecting steel plate bolts and double-sided welding, and constructing unilateral foot-lock bolts at the haunches and the arch feet. The problems that in the prior art, due to the fact that elevation and drilling positioning accuracy are insufficient, overexcavation and under-excavation are caused, the stability of a multi-free face supporting structure is poor, the construction conversion process is complex, consumed time is long, and an effective stress monitoring and early warning system is lacked are solved.

Description

Technical Field

[0001] This invention relates to the field of highway tunnel engineering construction technology, specifically a method for constructing a large-span, multi-faceted inclined shaft to a main tunnel with roof support. Background Technology

[0002] The term "top-out" in the context of tunnel construction refers to the construction method at the junction of an inclined shaft and the main tunnel. When the inclined shaft reaches the junction with the main tunnel, a series of construction steps are needed to gradually expand the cross-section of the inclined shaft to the designed cross-section of the main tunnel. This process is called "top-out".

[0003] Announcement No.: CN215860227U, titled: A cantilever structure for an inclined shaft excavating into the main tunnel via a pilot tunnel, comprising several rows of inclined shaft initial support single-row steel frames, inclined shaft initial support double-row steel frames, portal-shaped arch frames, portal-shaped double-row steel frames, portal-shaped single-row steel frames, and main tunnel initial support arch frames arranged sequentially from the inclined shaft to the main tunnel for support. The inclined shaft initial support single-row steel frames, inclined shaft initial support double-row steel frames, and portal-shaped arch frames are connected by connecting steel bars and are used to support the inclined shaft and the pilot tunnel inclined shaft section of the inclined shaft entering the main tunnel in sequence. The portal-shaped double-row steel frames and portal-shaped single-row steel frames are connected by the main tunnel initial support arch frames and are used to support the pilot tunnel main tunnel.

[0004] Announcement No.: CN112302687A, entitled: Construction Method for Support Replacement and Roof Cancellation in the Inclined Shaft Entry into the Main Tunnel, includes the following steps: Step 1: Excavate the inclined shaft pilot tunnel, and when it reaches a certain distance from the main tunnel sidewall I, begin uphill excavation until it reaches the main tunnel sidewall I; Step 2: Continue excavating along the rectangular pilot tunnel along the main tunnel sidewall I until it reaches the main tunnel sidewall II; Step 3: Remove the initial support of the pilot tunnel within the main tunnel area in the reverse direction, excavate the free face towards the top, and then raise the rectangular gantry and extend its legs; Step 4: Erect an arc-shaped arch frame, with its top abutting against the top crossbeam of the rectangular gantry; Step 5: Remove the rectangular gantry legs; Step 6: Excavate the bottom part of the main tunnel and extend the arc-shaped arch frame legs. This invention uses a support replacement method, raising and extending the short-leg gantry to become a long-leg gantry as support, which can effectively utilize temporary supports, reduce waste, ensure reasonable tunnel load distribution during support replacement, reduce surrounding rock convergence deformation, and improve the safety factor.

[0005] The existing technologies mentioned above suffer from over-excavation and under-excavation problems due to insufficient elevation and drilling positioning accuracy. Furthermore, the support structures on multiple free faces have poor stability, the construction conversion process is complex and time-consuming, and there is a lack of effective stress monitoring and early warning systems.

[0006] These problems not only increase construction difficulty and cost, but also pose a serious threat to construction safety and quality. Therefore, a method for constructing a large-span, multi-open-face inclined shaft to main tunnel with a cantilevered roof is provided. Summary of the Invention

[0007] The purpose of this invention is to provide a method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with a jacking structure, in order to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking, comprising the following steps: Step 1: Construction of the raised section of the inclined shaft: When the inclined shaft is constructed to the preset raised starting point station, the slope is adjusted to +12.67% and excavated uphill to the intersection station. For every 1m advance, the arch frame is raised by 12.67cm until the top elevation of the inclined shaft is 50cm higher than the designed top elevation of the main tunnel. Step 2: Strengthen the support at the intersection: Add temporary support for the intersection of the inclined shaft and the main tunnel with special-shaped arch frames, and connect them to the vertical steel frames on both sides by connecting steel plate bolts and double-sided welding. Install single-sided locking foot anchors at the arch waist and arch foot. Step 3: Construction of the gantry system: A gantry is erected at the intersection of the inclined shaft, the main tunnel, and the vehicle passage. The gantry consists of steel vertical beams and horizontal beams. The horizontal beams support 11 steel arch frames of the main tunnel. At the same time, 2 arch frames are constructed at the inclined shaft opening and the vehicle passage opening, and the locking joints are reinforced. Step 4: Main tunnel support system conversion: cut off the temporary irregular arch frame, erect 11 designed steel arch frames at the main tunnel intersection section, extend 2 arch frames in both the large and small mileage directions of the main tunnel, increase the length of the anchor bolts from 3m to 4.5m, and spray concrete to form a one-time combined support system covering the four free faces. Step 5: Main tunnel extension excavation: excavate the vehicle passage up the steps towards the smaller station number, then excavate the vehicle passage up the steps towards the larger mileage, and finally excavate to the end station number of the main tunnel, with the pilot tunnel being excavated simultaneously.

[0009] Preferably, a monitoring location is selected in the stress superposition zone at the intersection of the inclined shaft and the main tunnel. An intelligent sensing structure is installed at the end of the anchor bolt in the stress superposition zone at the intersection to collect real-time data on surrounding rock deformation, stress and seepage, and transmit it to the cloud-based early warning platform.

[0010] Preferably, in step one: a high-precision total station combined with a laser positioning device is used for borehole positioning, the borehole process is controlled by short advances, and the borehole angle and depth are adjusted in real time, with over-excavation ≤100mm.

[0011] Preferably, in step two: the irregular arch frame is made of No. 14 I-beams, arranged at 1.2m intervals, with a clearance adjustment value of ≥670cm for the steel frames on both sides, and the anchor rods are steel bars with a diameter of 22mm and a length of 3m.

[0012] Preferably, in step three: the crossbeam of the gantry system is 10m long, made of 25b steel, and the vertical beam is directly welded to the crossbeam and reinforced by anchor bolts with a diameter of 22mm.

[0013] Preferably, in step two: the top of the irregular arch frame adopts an arc with R=20.01m and an arc length of 9.22m.

[0014] Preferably, in step four: the main tunnel steel arch frame of the combined support system is made of 14-type steel, the shotcrete is of grade C25 and densely covers the arch frame, and the length of the anchor bolt is 4.5m with a spacing error of ≤±10mm.

[0015] Preferably, the intelligent sensing structure uses an integrated osmotic pressure sensor with a range of 40T and a sampling frequency of 30Hz, and transmits data through a digital display module with the 485 communication protocol.

[0016] Preferably, the elevation error between the inclined shaft and the main tunnel cross-section is ≤30mm after the inclined shaft is raised, and the accuracy of the main tunnel excavation outline is monitored by setting out with a total station.

[0017] Preferably, the method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with a jacking is characterized by further including a construction preparation stage: S1. Geological forecasting is carried out using ground-penetrating radar and advanced horizontal drilling. S2. Record the development of surrounding rock fissures, seepage volume, and lithological data; S3. Determine the advance support method based on the forecast results.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention first employs high-precision total stations and laser positioning technology to achieve high-precision elevation layout and borehole positioning at the intersection of the inclined shaft and the main tunnel, ensuring accurate blasting results, reducing over-excavation and under-excavation, and protecting the integrity of the surrounding rock. Secondly, addressing the complex stress conditions of multiple free faces, temporary arch support and one-time support with designed arches are used to quickly form an integrated load-bearing structure, enhancing stability and reducing the risk of deformation and damage to the support structure. Thirdly, through precise measurement and design optimization, the cross-section of the raised inclined shaft is perfectly aligned with the cross-section of the main tunnel, achieving continuity and stability in the construction process and saving construction time. Finally, in the area of ​​superimposed disturbance stress at the intersection of the inclined shaft and the main tunnel, an intelligent sensing and networked early warning monitoring system is established to collect data on surrounding rock deformation and stress in real time, analyze changes in surrounding rock stress, and ensure construction safety. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] One embodiment of the present invention provides a method for constructing a large-span inclined shaft with multiple open faces into a main tunnel by lifting the roof, comprising the following steps: Step 1: Construction of the raised section of the inclined shaft: When the inclined shaft is constructed to the preset raised starting point station, the slope is adjusted to +12.67% and excavated uphill to the intersection station. For every 1m advance, the arch frame is raised by 12.67cm until the top elevation of the inclined shaft is 50cm higher than the designed top elevation of the main tunnel. Step 2: Strengthen the support at the intersection: Add temporary support for the intersection of the inclined shaft and the main tunnel with special-shaped arch frames, and connect them to the vertical steel frames on both sides by connecting steel plate bolts and double-sided welding. Install single-sided locking foot anchors at the arch waist and arch foot. Step 3: Construction of the gantry system: The gantry is erected at the intersection of the inclined shaft, the main tunnel, and the vehicle passage. The gantry is composed of steel vertical beams and horizontal beams. The horizontal beams support 11 steel arch frames of the main tunnel. At the same time, 2 arch frames are constructed at the entrance of the inclined shaft and 2 at the entrance of the vehicle passage, and the locking joints are reinforced. Step 4: Main tunnel support system conversion: cut off the temporary irregular arch frame, erect 11 designed steel arch frames at the main tunnel intersection section, extend 2 arch frames in both the large and small mileage directions of the main tunnel, increase the length of the anchor bolts from 3m to 4.5m, and spray concrete to form a one-time combined support system covering the four free faces. Step 5: Main tunnel extension excavation: excavate the vehicle passage up the steps towards the smaller station number, then excavate the vehicle passage up the steps towards the larger mileage, and finally excavate to the end station number of the main tunnel, with the pilot tunnel being excavated simultaneously.

[0021] Furthermore, monitoring locations are selected in the stress superposition zone at the intersection of the inclined shaft and the main tunnel. Intelligent sensing structures are installed at the ends of the anchor bolts in the stress superposition zone at the intersection to collect real-time data on surrounding rock deformation, stress, and seepage, and transmit the data to the cloud-based early warning platform.

[0022] Furthermore, in step one, a high-precision total station combined with a laser positioning device is used for borehole positioning. The drilling process is controlled by short advances, and the drilling angle and depth are adjusted in real time. The over-excavation is ≤100mm. Through precise slope adjustment and elevation control, a smooth transition between the inclined shaft section and the main tunnel section is ensured, reducing the amount of subsequent finishing work. Laser positioning and short advance blasting technology significantly reduce over-excavation, protect the integrity of the surrounding rock, and improve structural stability.

[0023] Furthermore, in step two: the irregular arch frame uses No. 14 I-beams, spaced 1.2m apart, with a clearance adjustment value of ≥670cm on both sides of the steel frame, and the anchor rods are 22mm diameter steel bars with a length of 3m. The top of the irregular arch frame adopts an arc with R=20.01m and an arc length of 9.22m. The irregular arch frame is used to provide temporary support, disperse the stress of multiple open surfaces at the intersection, prevent the surrounding rock from becoming unstable, and improve stability. The irregular arch frame adapts to complex cross-sectional shapes, effectively controls deformation risks before support conversion, and adapts to changes in the excavation contour through adjustable steel frames, avoiding gaps between the support structure and the surrounding rock.

[0024] Furthermore, in step three: the crossbeam of the gantry system is 10m long and uses 25b steel. The vertical beam and the crossbeam are directly welded and fixed, and reinforced by locking foot anchors with a diameter of 22mm. The gantry, as a permanent load-bearing structure, bears the load of the main tunnel arch frame, ensuring the overall rigidity of the intersection. The gantry integrates the support of multiple intersections to avoid stress concentration caused by step-by-step construction, and simultaneously completes the locking of the inclined shaft and the vehicle passage, shortening the support conversion time.

[0025] Furthermore, in step four: the main tunnel steel arch frame of the combined support system is made of 14-type steel, and the shotcrete is of grade C25, which densely covers the arch frame. The length of the anchor bolts is 4.5m, and the spacing error is ≤±10mm. The extended anchor bolts enhance the anti-slip ability of the arch foot, and the dense concrete filling ensures the integrity of the support. One-time support avoids the stability risk of phased construction. The extended anchor bolts and dense concrete can effectively improve the deformation resistance and play a synergistic role in controlling deformation, reducing the need for later reinforcement.

[0026] Furthermore, in step five, precise measurement and layout achieve zero-error transition between the inclined shaft and the main tunnel, avoid cross-sectional misalignment, optimize resource allocation through step-by-step excavation, and shorten the critical path construction period.

[0027] Furthermore, the intelligent sensing structure adopts an integrated osmotic pressure sensor with a range of 40T and a sampling frequency of 30Hz. Data is transmitted through a digital display module using the 485 communication protocol. Typical locations are selected in the stress superposition zone at the intersection of the inclined shaft and the main tunnel. The intelligent sensing structure is installed at the end of the anchor bolt in the original design system, with an osmotic pressure sensing system installed inside. Through the anchor bolt extending into the rock mass, the deformation feedback of the mechanical sensing structure at the end of the anchor bolt reflects the gradual failure process of the engineering soil and rock mass. This realizes the Internet of Things functions of front-end monitoring, mid-term information transmission analysis, and cloud-based visual disaster early warning for the engineering anchoring system, greatly improving the reliability of construction safety.

[0028] Furthermore, after the inclined shaft is raised, the elevation error between it and the main tunnel cross-section is ≤30mm. A total station is used to set out and monitor the accuracy of the main tunnel excavation outline.

[0029] Furthermore, this also includes the construction preparation phase: S1. Geological forecasting is carried out using ground-penetrating radar and advanced horizontal drilling. S2. Record the development of surrounding rock fissures, seepage volume, and lithological data; S3. Determine the advance support method based on the forecast results.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for constructing a large-span, multi-open-face inclined shaft to a main tunnel with roof support, characterized in that: Includes the following steps: Step 1: Construction of the raised section of the inclined shaft: When the inclined shaft is constructed to the preset raised starting point station, the slope is adjusted to +12.67% and excavated uphill to the intersection station. For every 1m advance, the arch frame is raised by 12.67cm until the top elevation of the inclined shaft is 50cm higher than the designed top elevation of the main tunnel. Step 2: Strengthen the support at the intersection: Add temporary support for the intersection of the inclined shaft and the main tunnel with special-shaped arch frames, and connect them to the vertical steel frames on both sides by connecting steel plate bolts and double-sided welding. Install single-sided locking foot anchors at the arch waist and arch foot. Step 3: Construction of the gantry system: A gantry is erected at the intersection of the inclined shaft, the main tunnel, and the vehicle passage. The gantry consists of steel vertical beams and horizontal beams. The horizontal beams support 11 steel arch frames of the main tunnel. At the same time, 2 arch frames are constructed at the inclined shaft opening and the vehicle passage opening, and the locking joints are reinforced. Step 4: Main tunnel support system conversion: cut off the temporary irregular arch frame, erect 11 designed steel arch frames at the main tunnel intersection section, extend 2 arch frames in both the large and small mileage directions of the main tunnel, increase the length of the anchor bolts from 3m to 4.5m, and spray concrete to form a one-time combined support system covering the four free faces. Step 5: Main tunnel extension excavation: excavate the vehicle passage up the steps towards the smaller station number, then excavate the vehicle passage up the steps towards the larger mileage, and finally excavate to the end station number of the main tunnel, with the pilot tunnel being excavated simultaneously.

2. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 1, characterized in that: Monitoring locations were selected in the stress superposition zone at the intersection of the inclined shaft and the main tunnel. Intelligent sensing structures were installed at the ends of the anchor bolts in the stress superposition zone at the intersection to collect real-time data on surrounding rock deformation, stress, and seepage, and transmit the data to the cloud-based early warning platform.

3. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 1, characterized in that, In step one: a high-precision total station combined with a laser positioning device is used for drilling positioning. The drilling process is controlled by short advances, and the drilling angle and depth are adjusted in real time, with over-excavation ≤100mm.

4. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 1, characterized in that, In step two: the irregular arch frame is made of No. 14 I-beams, spaced 1.2m apart, with a clearance adjustment value of ≥670cm on both sides of the steel frame, and the anchor rods are steel bars with a diameter of 22mm and a length of 3m.

5. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 1, characterized in that, In step three: the crossbeam of the gantry system is 10m long and is made of 25b steel. The vertical beam and the crossbeam are directly welded and fixed, and reinforced by locking foot anchors with a diameter of 22mm.

6. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 1, characterized in that, In step two: the top of the irregular arch frame adopts an arc with R=20.01m and an arc length of 9.22m.

7. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 1, characterized in that, In step four: the main tunnel steel arch frame of the combined support system is made of 14-type steel, the shotcrete is of grade C25 and densely covers the arch frame, the length of the anchor bolt is 4.5m and the spacing error is ≤±10mm.

8. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 2, characterized in that: The intelligent sensing structure uses an integrated osmotic pressure sensor with a range of 40T and a sampling frequency of 30Hz, and transmits data through a digital display module with the 485 communication protocol.

9. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 8, characterized in that: After the inclined shaft is raised, the elevation error between it and the main tunnel section is ≤30mm. A total station is used to set out and monitor the accuracy of the main tunnel excavation outline.

10. The method for constructing a large-span, multi-free-face inclined shaft to a main tunnel with jacking as described in claim 1, characterized in that, It also includes the construction preparation stage: S1. Geological forecasting is carried out using ground-penetrating radar and advanced horizontal drilling. S2. Record the development of surrounding rock fissures, seepage volume, and lithological data; S3. Determine the advance support method based on the forecast results.