A method for roof picking construction of a large-section tunnel inclined shaft into a main tunnel in a weak water-rich stratum

Abstract

The application discloses a large-section tunnel inclined shaft into main tunnel roof picking construction method in soft and water-rich stratum. The method comprises the following steps: inclined shaft curved wall type lining support, inclined shaft straight wall type lining support, portal upper arch support, roof picking pilot tunnel excavation support, portal reinforcement ring support, roof picking pilot tunnel section main tunnel support, main tunnel upper step excavation support, main tunnel upper middle step excavation support, main tunnel upper middle and lower step excavation support, and main tunnel upper middle and lower step and inverted arch excavation support. The application proposes a new structure of combined support of portal upper arch and portal reinforcement ring for the intersection section in the roof picking construction of large-section tunnel in soft and water-rich stratum, optimizes the support strength of the portal reinforcement ring and the roof picking construction process, effectively reduces the over-excavation area and deformation of the surrounding rock of the excavation surface, strengthens the support strength of the stress concentration position, and speeds up the construction progress of the intersection section of the main tunnel from the inclined shaft through reasonable process organization.

Description

Technical Field

[0001] This application relates to the technical field of tunnel construction, and in particular to a method for constructing a large-section tunnel with inclined shafts in soft, water-rich strata, involving the roof lifting process. Background Technology

[0002] The rapid and sustained development of the national economy has spurred the prosperity of transportation and tunnel engineering construction, leading to the emergence of a large number of extra-long and long tunnels. my country has become the country with the largest tunnel construction scale, the fastest development speed, and the highest construction difficulty in the world. To accelerate the excavation speed and assist in ventilation and drainage, long tunnels usually have inclined shafts as auxiliary tunnels to increase the working face. Due to the complex spatial structure and frequent stress transformation at the intersection of the inclined shaft and the main tunnel, especially when inevitably crossing complex geological conditions such as weak, water-rich, and fault fracture zones, the risk of collapse is high. Therefore, researching a fast and safe roof-lifting construction scheme has strong practical significance.

[0003] Currently, numerous scholars both domestically and internationally have conducted extensive research and summaries on tunnel roof-lifting technology, achieving a series of results. Commonly used methods for inclined shaft-to-main-tunnel construction include the following five: the large-package method, the small-package method, the scaffolding arch-supported roof-lifting method, the pilot tunnel roof-lifting method, and the inclined shaft cantilever beam construction method. Research on roof-lifting technology under different geological or construction conditions still largely focuses on the intersection of the inclined shaft and the main tunnel, employing methods such as early gradual transition, secondary lining construction at the transition point, and abrupt change at the design cross-section transition point. However, for large-section tunnel projects under complex geological conditions such as weak, water-rich, and fault fracture zones, the complex procedures, insufficient initial support strength to suppress surrounding rock deformation, and the need for support structure replacement and the intersection of multiple stress structures still exist, failing to completely improve the complex stress state of the surrounding rock at the intersection.

[0004] Chinese patent CN201910519993.6 discloses a method for constructing a large-section soft rock deformation tunnel by tilting the roof of the inclined shaft into the main tunnel. This invention uses a roof-tiling arch support beam, a small pilot tunnel excavation and support, a main tunnel support section in the small pilot tunnel, an upper bench excavation and support section in the main tunnel, an upper and middle bench excavation and support section in the main tunnel, and an upper, middle and lower bench excavation and support section in the main tunnel to decompose the large main tunnel into small chambers for segmented excavation. Using the auxiliary tunnel structure and portal frame as the base point, the small chamber unit structure is supported to form a stable structure, thus completing the conversion of the main tunnel to the bench method construction. However, this invention has the following shortcomings: First, the structure at the intersection of the inclined shaft and the main tunnel is subject to complex stress and frequent stress transformation. Using only the cantilever arch support beam to support the main tunnel arch support is too weak, which may lead to large deformation of the lining structure and collapse of the surrounding rock. Measures should be taken to strengthen the support at the intersection. Second, the one-time, full-section excavation and support of the cantilever arch at the intersection of the inclined shaft is not conducive to the stability of the surrounding rock. The over-excavation area and the expansion time are large, which may easily cause tunnel deformation or collapse. Third, the cantilever arch is installed after the construction of the bottom of the inclined shaft. For large-section inclined shafts excavated by the bench method, since the cantilever arch is installed in one go, it is necessary to wait until the lower bench is excavated and supported to the inclined shaft side of the main tunnel excavation outline before construction can begin. This will significantly prolong the construction period and reduce construction efficiency.

[0005] In summary, the aforementioned technologies are insufficient to solve the problem of roof-lifting construction under complex geological conditions, such as weak support strength, large over-excavation of surrounding rock, and long construction period at intersections. Therefore, it is urgent to study a roof-lifting construction method suitable for large-section tunnels under complex geological conditions such as soft and water-rich conditions. Summary of the Invention

[0006] In view of this, this application provides a method for constructing the roof of a large-section tunnel with an inclined shaft leading to the main tunnel in soft, water-rich strata, which solves the problem of roof construction at the intersection of the inclined shaft and the main tunnel under complex geological conditions.

[0007] This application provides a method for constructing a large-section tunnel with inclined shafts in soft, water-rich strata, including the following steps:

[0008] S1. Inclined shaft curved wall lining support:

[0009] S1-1. Excavation and support for the upper bench of the inclined shaft:

[0010] For the upper section of the inclined shaft, the upper step is excavated and the curved wall lining is installed. The initial support adopts a combination of steel arch frame, system anchor bolts, steel mesh and concrete support.

[0011] S1-2. Excavation and support of the lower bench of the inclined shaft:

[0012] The lower section of the inclined shaft lower step is excavated and the curved wall lining is installed. The lower step of the inclined shaft is excavated in an alternating manner on the left and right sides. The initial support adopts a combination of steel arch frame, system anchor bolt, steel mesh and concrete support.

[0013] S2. Inclined shaft straight-wall lining support:

[0014] At a first predetermined distance inside the outline of the main tunnel excavation, the inclined shaft is excavated using the step method after the bottom surface is lowered and straight wall lining support is provided, and anchor mesh spraying combined support is applied.

[0015] S3. Upper arch support of the gantry frame:

[0016] At the second predetermined distance inside the main tunnel excavation outline, the upper section of the inclined shaft is supported by the upper arch frame of the gantry and anchor mesh spraying combined support is applied. After the lower step of the inclined shaft is excavated, the lower section of the upper arch frame of the gantry is supported.

[0017] S4. Excavation and support of the top-mounted pilot tunnel:

[0018] In the direction perpendicular to the axis of the main tunnel, along the excavation outline of the main tunnel and with allowance for deformation, the inclined shaft is excavated and supported by the top-lifting guide tunnel;

[0019] S5. Gantry reinforcement ring support:

[0020] When the excavation and support of the top guide tunnel extends to the bottom surface of the upper step outside the main tunnel excavation outline, and the lower section of the upper arch of the portal frame is supported to the inner side of the main tunnel excavation outline, the portal frame reinforcement ring support is carried out at the intersection section.

[0021] S6. Support for the main tunnel section with the top overhang:

[0022] After the gantry reinforcement ring support is stabilized, the irregular arch frame of the main tunnel is constructed and the anchor mesh and spraying combined support is implemented in a timely manner.

[0023] S7. Excavation and support of the upper bench of the main tunnel:

[0024] After the special-shaped arch support of the main tunnel is completed, the column on one side of the cantilevered guide tunnel is removed and the upper step of the main tunnel is excavated and supported in that direction. When the predetermined construction space is met, each working face of the upper step of the main tunnel is excavated and supported simultaneously.

[0025] S8. Excavation and support of the upper and middle steps of the main tunnel:

[0026] After the working face of the upper step of the main tunnel has been constructed for a sufficient distance, the excavation and support of the middle step of the main tunnel within the width of the top guide tunnel will be carried out. After the middle step of the main tunnel is constructed in one direction, the excavation and support of each working face of the upper step and the middle step of the main tunnel will be carried out simultaneously.

[0027] S9. Excavation and support for the upper, middle, and lower steps of the main tunnel:

[0028] After the upper and middle steps of the main tunnel are constructed to a sufficient distance, the lower steps of the main tunnel within the width of the top guide tunnel are excavated and supported. After the lower steps of the main tunnel are constructed to a sufficient distance in one direction, each working face of the upper, middle and lower steps of the main tunnel is excavated and supported simultaneously until three steps are formed.

[0029] S10. Excavation and support of the main tunnel upper bench, middle bench, lower bench, and invert arch:

[0030] Once the three steps are formed and there is sufficient space for construction, the invert arch is excavated and supported. Then, the upper, middle, and lower steps of the main tunnel and each working face of the invert arch are constructed simultaneously, and secondary lining is applied in one direction to form a normal work sequence, thus completing the roof lifting construction of the inclined shaft into the main tunnel.

[0031] Optionally, in step S1, if the surrounding rock is relatively good, the inclined shaft is excavated by manual pneumatic picks in conjunction with an excavator; if the surrounding rock is relatively poor, the inclined shaft is excavated by controlled blasting.

[0032] Optionally, in step S2, the first predetermined distance is 1m to 5m, the height of the bottom surface of the inclined shaft after being lowered is 50cm to 100cm, the height of the straight wall lining arch is the same as the height of the curved wall lining arch, and the installation width of the gantry reinforcing ring is reserved within the width range of the straight wall lining.

[0033] Optionally, in step S3, the second predetermined distance is the thickness of the gantry reinforcing ring, the arch height of the upper arch frame (4) of the gantry is the arch height of the cantilever guide hole (5), and the arch curvature of the upper arch frame (4) of the gantry should ensure that the inner side of the irregular arch frame (7) of the main hole is placed on the gantry reinforcing ring (6).

[0034] Optionally, in step S4, the arch height of the top-mounted guide tunnel is the height of the tunnel's excavation outline relative to the horizontal level, the width of the top-mounted guide tunnel is 1 / 3 to 1 / 2 of the width of the upper arch frame of the portal frame, the cross-sectional shape of the top-mounted guide tunnel is trapezoidal or arched, and the top-mounted guide tunnel is supported by a combination of steel arch frame, system anchor bolts, steel mesh, and concrete, with plain concrete sprayed on both side walls to seal the surrounding rock.

[0035] Optionally, in step S5, the portal frame reinforcing ring is an integral structure formed by several cantilevered portal frames, arch frames, lining arch frames, and concrete pouring. The height of the support beam of the portal frame reinforcing ring is the same as the height of the arch foot of the upper arch frame of the portal frame, and the width of the portal frame reinforcing ring is the width of the vertical side wall of the upper arch frame of the portal frame, so as to ensure that the two are closely fitted and erected.

[0036] Optionally, during the construction of the gantry reinforcement ring, the cantilever gantry, arch support and steel reinforcement are carried out sequentially from the inside to the outside, and then the lining arch is hung and concrete is poured to form an integral structure.

[0037] Optionally, in step S6, the support range of the main tunnel irregular arch frame is the width of the top guide tunnel, the inner side of the main tunnel irregular arch frame is placed on the support beam of the portal frame reinforcing ring, and the outer side is placed on the bottom rock layer outside the main tunnel excavation outline.

[0038] Optionally, the inclined shaft curved wall lining, straight wall lining, and upper arch frame of the portal frame are connected in the longitudinal and radial directions by longitudinal connecting bars and connecting plates, respectively.

[0039] As used in this article, the term "inner side" refers to the side where the main tunnel and the inclined shaft intersect.

[0040] As used in this text, the term "outer side" refers to the side of the main tunnel away from the inclined shaft.

[0041] It should be noted that the spatial stress at the intersection of the inclined shaft and the main tunnel is complex. During construction, monitoring and measurement should be strengthened, and the excavation method and support parameters should be adjusted in a timely manner based on the monitoring and measurement results to ensure construction safety.

[0042] The present invention has the following beneficial effects:

[0043] 1. This invention provides a method for constructing a large-section tunnel with inclined shafts in soft, water-rich strata, which solves the problem of constructing inclined shafts in soft, water-rich strata, which involves roof lifting. The inclined shaft adopts a step-by-step excavation and support method, with staggered excavation on the left and right sides of the lower step. It has the following significant advantages: step-by-step excavation of small sections ensures uniform stress on the structure and stability of the surrounding rock; it can be carried out in conjunction with subsequent roof lifting construction procedures to accelerate the construction progress; and workers can install arch frames on the rock surface of the steps to improve construction efficiency.

[0044] 2. This invention provides a method for constructing a large-section tunnel with inclined shaft and top-lifting support at the main tunnel entrance in soft, water-rich strata. The inclined shaft intersection section adopts a novel combined support structure consisting of an upper arch frame and a reinforcing ring. The reinforcing ring is an integral structure formed by several top-lifting portal frames, a sleeve arch, a lining arch, and concrete pouring. Compared with the top-lifting portal frame support in existing technologies, this method reduces the area and time of exposed surrounding rock at the excavation face, strengthens the support strength at stress-concentrated intersections, and ensures the safety of top-lifting construction of large-section tunnels in soft, water-rich strata.

[0045] 3. This invention provides a method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata, involving roof support at the intersection. The method involves temporarily supporting the intersection section with the upper arch of the gantry frame. After the inclined shaft construction is completed, the gantry frame reinforcement ring is then installed. This allows construction workers to operate under the support of the upper arch and reinforcement ring of the gantry frame, significantly reducing over-excavation and convergence deformation of the surrounding rock. It avoids the construction risks associated with traditional roof support methods that involve unsupported, one-time installation of the roof support gantry frame, and quickly and efficiently solves the problem of roof support at intersections under complex geological conditions.

[0046] 4. This invention provides a method for constructing a large-section tunnel with an inclined shaft leading to the main tunnel in soft, water-rich strata by lifting the roof over the tunnel. The method involves temporarily supporting the intersection section with the upper arch frame of the gantry, and simultaneously constructing the lifting guide tunnel and the various working faces of the inclined shaft. After the lifting gantry is constructed to the other side of the upper step of the main tunnel and the lower step of the inclined shaft is completed, the gantry reinforcement ring of the intersection section is constructed, saving the support time of the intersection section, realizing parallel construction of the inclined shaft and the lifting guide tunnel, and accelerating the construction progress of the intersection section from the inclined shaft to the main tunnel. Attached Figure Description

[0047] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0048] Figure 1 These are schematic diagrams of straight-wall lining and curved-wall lining support in embodiments of the present invention;

[0049] Figure 2 This is a schematic diagram of the upper arch support of the portal frame according to an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the top-supported guide tunnel according to an embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram of the gantry reinforcement ring support according to an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the cross-section of the main tunnel support in the top-supported guide tunnel section according to an embodiment of the present invention;

[0053] Figure 6 A schematic diagram of the cross-section of the intersection section of the present invention;

[0054] Figure 7 This is a schematic diagram of the excavation and support of the upper step of the main tunnel according to an embodiment of the present invention;

[0055] Figure 8 This is a schematic diagram of the excavation and support of the upper and middle steps of the main tunnel according to an embodiment of the present invention;

[0056] Figure 9 This is a schematic diagram of the excavation and support of the upper step, middle step, and lower step of the main tunnel according to an embodiment of the present invention;

[0057] Figure 10 This is a schematic diagram of the upper step, middle step, lower step of the main tunnel, and invert arch excavation and support of an embodiment of the present invention;

[0058] Figure 11 This is a diagram showing the data analysis of intersection segment deformation monitoring in an embodiment of the present invention.

[0059] The components in the diagram are labeled as follows:

[0060] 1- Inclined shaft; 2- Curved wall lining; 3- Straight wall lining; 4- Upper arch frame of portal frame; 5- Top-mounted pilot tunnel; 6- Portal frame reinforcing ring; 61- Top-mounted portal frame; 62- Arch sleeve; 63- Lining formwork arch; 7- Irregular arch frame of main tunnel; 8- Main tunnel; 81- Upper step of main tunnel; 82- Middle step of main tunnel; 83- Lower step of main tunnel; 84- Inverted arch; 85- Excavation outline of main tunnel; 86- Initial support of main tunnel; 91- Large mileage direction; 92- Small mileage direction. Detailed Implementation

[0061] The technical solutions of the embodiments of this application 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 this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0062] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0063] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0064] This application example uses the roof-lifting construction of the inclined shaft leading to the main tunnel section of the Xishanying Tunnel on the Sanqing Expressway in Yunnan Province as an example. The Xishanying Tunnel is located in Yiliang County, Kunming City, with a total length of approximately 6.8 km. The left line runs from Z3K89+899 to Z3K96+728, with a maximum burial depth of 310 m, while the right line runs from K89+910 to K96+697, with a maximum burial depth of approximately 340 m. It is one of the major control projects of the Qujing Sanbao to Kunming Qingshui Expressway. The surrounding rock of the tunnel is mainly composed of dolomite from the Upper Sinian System of the Proterozoic, specifically the Dengying Formation and Doushantuo Formation. Fissures, structures, and karst are well-developed, resulting in a fractured rock mass with poor stability. Class V surrounding rock accounts for 51.76%, and Class IV surrounding rock accounts for 48.24%. Geophysical interpretation results indicate the presence of a geological fault (FW7) near the inclined shaft. FW7 is a reverse fault dipping towards the greater mileage direction, with alternating layers of siltstone, shale, and sandstone on both the hanging wall and footwall, and underlying limestone interbedded with dolomite. It intersects the railway line at an 81° angle between K94+880 and K95+000, with a fault dip of 268°∠81° and an affected width of approximately 118m. The basic seismic intensity of the tunnel site area is VII–IX, classifying it as a strong seismic zone. Groundwater primarily consists of Quaternary loose pore water, bedrock fissure water, and fault fracture zone fissure water, found in colluvial deposits, bedrock strata, and fault fracture zones, respectively. The water level varies seasonally, and the water volume is significantly affected by recharge. The water volume is influenced by the degree of bedrock fissure development, and localized enrichment is possible. During construction, the water appears as streams or gushing flows, with localized mudslides and water inrushes. The predicted normal inflow of the inclined shaft is 1140.58 m³. 3 / d, maximum inflow 1368.69m³ 3 / d, water inrush is a prominent problem.

[0065] Conventional top-lifting methods typically involve installing a top-lifting gantry beam support at the intersection. This means that at the intersection, the auxiliary tunnel structure and the gantry serve as base points to support the small cavern unit structure, forming a stable support structure for rapid conversion to the main tunnel bench method. However, when the geological conditions are complex, traditional top-lifting methods may pose construction risks. The intersection section may not be sufficient to support the initial support of the main tunnel. The external forces borne by the main tunnel arch in the pilot tunnel section are transferred to the top-lifting gantry in the inclined shaft, leading to increased deformation of the surrounding rock in weak, water-rich sections and exacerbating safety risks. Furthermore, installing a top-lifting gantry across the entire cross-section of the intersection section requires a large amount of excavation of the surrounding rock, which is detrimental to the stability of the support structure, posing a risk of large deformation and collapse. The unsupported operation of construction personnel also increases safety hazards. Sequential excavation of the inclined shaft intersection section and the pilot tunnel leads to extended construction time. Since the inclined shaft is located on the critical path of the tunnel project, it is highly likely to delay the overall construction period. This invention, through comprehensive analysis of the characteristics and deformation features of the weak and water-rich strata in the constructed inclined shaft section, selects to install a combined support of the upper arch frame and the reinforcing ring of the gantry at the intersection of the inclined shaft and the main tunnel. After installing the upper arch frame of the gantry at the intersection, the pilot tunnel is excavated. During the construction period of the pilot tunnel, the lower bench of the inclined shaft is also supported to the intersection. Then, the gantry reinforcing ring is installed, and the main tunnel of the pilot tunnel section is supported by an irregular arch frame to complete the top-lifting construction, thereby strengthening the support strength of the intersection section at the bottom of the inclined shaft and ensuring the stability of the intersection area under stress.

[0066] Please refer to Figure 1-11 The method for constructing the inclined shaft of a large-section tunnel in soft, water-rich strata with roof support for tunneling, provided in this application embodiment, includes the following steps:

[0067] S1. Inclined shaft curved wall lining with 2 supports:

[0068] The working faces of the upper and lower steps of the inclined shaft 1 are excavated and supported simultaneously. The lower step adopts staggered excavation of the left and right sections. The excavation length and step height are adjusted according to the construction machinery and personnel. The excavation cycle advance meets the specifications. The excavation method is reasonably selected according to the surrounding rock conditions. If the surrounding rock is good, manual pneumatic picks are used in conjunction with excavators. If the surrounding rock is poor, controlled blasting (pre-splitting, micro-vibration blasting) is used for excavation. Trackless transportation is used for tunnel muck removal. The steel frame, steel mesh and anchor rods are uniformly processed by the steel component factory. The steel frame is installed manually and the steel mesh is hung. Pneumatic rock drills are used to install the system anchor rods. The mixing plant mixes the concrete, and the concrete is transported by concrete trucks. Wet spraying robot arm sprays the concrete.

[0069] S1-1. Excavation and support of the upper bench of inclined shaft 1:

[0070] The upper step of the inclined shaft 1 is excavated and supported. The advance of the upper step is controlled at 3-5m per cycle, and the height of the upper step is 3.9m. The initial support adopts a combination of steel arch frame, system anchor bolts, steel mesh and concrete support. The curved wall lining 2 of the inclined shaft adopts I18 I-beams, the arch frame height is 7.36m, the arch frame spacing is 1m / frame, and the arch foot is set with locking steel pipes and grouting is performed on the locking steel pipes to ensure the stability of the foundation. Longitudinal connecting bars are promptly installed between the upper sections of the curved wall lining 2 and connected firmly. The connecting bars adopt Φ22 connecting bars, arranged in a figure-eight shape, with a circumferential spacing of 1m. Advanced geological forecasting is carried out before excavation, and advanced support is implemented.

[0071] S1-2. Excavation and support of the lower bench of inclined shaft 1:

[0072] The lower step of the inclined shaft 1 was excavated and supported. The left and right sections of the lower step of the inclined shaft 1 were excavated in an alternating manner with an alternation length of 3m. The initial support adopted a combination of steel arch frame, system anchor bolts, steel mesh, and concrete support. The curved wall lining 2 of the inclined shaft adopted I18 I-beams with an arch frame height of 7.36m and an arch frame spacing of 1m / frame. The arch feet were equipped with locking steel pipes and the locking steel pipes were grouted. Longitudinal connecting bars were promptly installed and firmly connected between the lower sections of the curved wall lining 2. The connecting bars adopted Φ22 connecting bars, arranged in a figure-eight shape with a circumferential spacing of 1m. The upper and lower sections of the curved wall lining 2 were connected by connecting plates with a thickness of 16mm. Advanced geological forecasting was carried out before excavation, and advanced support was implemented.

[0073] S2. Inclined shaft straight wall lining with 3 supports:

[0074] Considering the installation width of the gantry reinforcing ring 6 and the slag removal requirements of the main tunnel invert arch, which is beneficial for controlling structural convergence deformation, reducing construction control difficulty, and facilitating vehicle movement, the bottom surface of the inclined shaft 1 is lowered by 50cm at a distance of 5m to 1m inside the main tunnel excavation outline 85 to allow slag removal from the main tunnel 8 along the slope. Then, the curved wall lining 2 is replaced with a straight wall lining 3. The straight wall lining 3 uses I18 I-beams, the arch height is adjusted to 7.86m, and the arch spacing is adjusted to 0.8m / frame. The upper and lower sections of the straight wall lining 3 are connected by connecting plates with a thickness of 16mm. The advanced support uses Φ42 small guide pipes, each 3.5m long, with a circumferential spacing of 40cm and a longitudinal spacing of 2.5m.

[0075] Specifically, the inner side is the side where the main tunnel intersects with the inclined shaft, and the outer side is the side of the main tunnel away from the inclined shaft.

[0076] S3. Four supports for the upper arch of the gantry frame:

[0077] To reduce over-excavation of the surrounding rock and improve operational efficiency, 1m inside the 85m inner side of the main tunnel excavation outline, i.e., the width of the pre-reserved gantry reinforcement ring 6, the upper arch frame 4 of the gantry is used and anchor mesh spraying combined support is applied in a timely manner. First, the upper step of the inclined shaft 1 is excavated and supported. When the lower step of the inclined shaft 1 is excavated to this location, the lower section 4 of the upper arch frame of the gantry is installed. The arch frame is made of I18 I-beams, the height of the arch frame is adjusted to 8.47m, and the arch frame spacing is 0.8m / frame. The upper and lower sections of the upper arch frame 4 of the gantry are connected by connecting plates with a thickness of 16mm.

[0078] S4. Excavation and support of the top-mounted pilot tunnel 5:

[0079] In the direction perpendicular to the axis of the main tunnel 8, along the excavation outline 85 of the main tunnel, considering the reserved deformation of 40cm for the main tunnel 8, the arch frame of the top-mounted pilot tunnel 5 is installed and anchor-mesh-shotcrete combined support is implemented; the excavation advance of the top-mounted pilot tunnel 5 is controlled at 0.8m, and the slag can be dug out by a small excavator and then transported out of the tunnel by a loader; the arch frame of the top-mounted pilot tunnel 5 uses 4.5m×5m I18 I-beams, with an arch frame spacing of 0.8m / frame, and the arch and sidewall are connected by connecting plates with a thickness of 16mm; the arch anchors use 4m long Φ25 hollow grouting anchors with a circumferential and longitudinal spacing of 0.8m×0.6m; double-layer Φ8 steel mesh is laid with a mesh spacing of 20cm×20cm, and C25 plain concrete with a thickness of 25cm is sprayed to seal the surrounding rock; the advance support uses Φ42 guide pipes, each 3.5m long, with a circumferential spacing of 30cm and a longitudinal spacing of 2.5m.

[0080] S5. Gantry Reinforcing Ring 6 Support:

[0081] To ensure that the bottom of the steel frame is not suspended after the main tunnel 8 is cantilevered and that the initial support 86 of the main tunnel is evenly stressed, when the arch frame of the cantilevered guide tunnel 5 is supported to the upper step outside the excavation outline 85 of the main tunnel, and the lower section of the upper arch frame 4 of the portal frame is also supported to the inner side of the excavation outline 85 of the main tunnel, the portal frame reinforcement ring 6 is installed. The portal frame reinforcement ring 6 is an integral structure formed by three I40 type cantilevered portal frames 61, three I18 type sleeve arches 62, three I18 type lining formwork arches 63, and concrete pouring. During construction, the cantilevered portal frames 61, sleeve arches 62, and steel bars are installed sequentially from the inside to the outside, and then the lining formwork arches 63 are hung and concrete is poured to form an integral structure. To ensure that the portal frame reinforcement ring 6 is firm and stable, 10 4m long Φ42 locking foot anchors and 4m long Φ22 mortar anchors are added to each side of the steel frame, and then C25 concrete is sprayed to fix the crossbeams and support columns.

[0082] S6. Support for the main tunnel in 5 sections of the top-supported pilot tunnel:

[0083] After the gantry reinforcement ring 6 is stabilized, the I22b I-beam main tunnel special-shaped arch frame 7 is installed and anchor mesh and shotcrete combined support is applied in a timely manner. The steel frame spacing is 0.6m. The inner side of the main tunnel special-shaped arch frame 7 is placed on the support beam of the gantry reinforcement ring 6. The two are connected by bolts and welded firmly. The outer side is placed on the bottom rock layer outside the main tunnel excavation outline 85. 40 channel steel is used as pads to increase the stress area and reduce the deformation of the arch frame. After the main tunnel special-shaped arch frame 7 is installed, Φ8 double-layer steel mesh is laid immediately with a mesh spacing of 15×15cm. 30cm thick C25 concrete is sprayed to seal the surrounding rock.

[0084] S7. Excavation and support of the upper step of the main tunnel at point 81:

[0085] After the support of the irregular arch frame 7 of the main tunnel section is completed, the side wall of the cantilevered guide tunnel 5 is removed by gas cutting. After the removal, the bottom of the cantilevered guide tunnel 5 is lowered to form the upper bench 81 of the main tunnel. The upper bench 81 of the main tunnel is constructed a certain distance in the direction of the greater mileage 91 to meet the construction space requirements. Then, the upper bench 81 of the main tunnel is excavated and initially supported at the same time along the direction of the greater mileage 91 and the direction of the lesser mileage 92 of the tunnel.

[0086] S8. Excavation and support of the upper bench 81 and the middle bench 82 of the main tunnel:

[0087] After the two working faces of the upper step 81 of the main tunnel exceed the side wall of the inclined shaft 1 by 10m, the lowering excavation of the middle step 82 of the main tunnel within the width of the top guide tunnel 5 is carried out simultaneously. The initial support follows closely. The middle step 82 of the main tunnel is constructed a certain distance in the direction of the greater mileage 91 and meets the construction space requirements. Then, each working face of the upper step 81 and the middle step 82 of the main tunnel is constructed simultaneously in the direction of the greater mileage 91 and the direction of the lesser mileage 92.

[0088] S9. Excavation and support of the upper bench of the main tunnel (81), the middle bench of the main tunnel (82), and the lower bench of the main tunnel (83):

[0089] After the upper step 81 and the middle step 82 of the main tunnel have been constructed to a sufficient distance, the lower step 83 of the main tunnel within the width of the top guide tunnel 5 will be excavated simultaneously. The initial support will follow closely. After the lower step 83 of the main tunnel is constructed to a certain distance in the direction of the greater mileage 91 and the construction space requirements are met, each working face of the upper step 81, the middle step 82 and the lower step 83 of the main tunnel will be constructed simultaneously in the direction of the greater mileage 91 and the direction of the lesser mileage 92.

[0090] S10. Excavation and support of the upper step of the main tunnel (81), the middle step of the main tunnel (82), the lower step of the main tunnel (83), and the invert arch (84):

[0091] After the conventional three-step structure is formed, construction will proceed on each work face. Excavation and support of the invert arch 84 of the main tunnel will begin. Once sufficient working space is available, construction will proceed simultaneously on each work face of the upper step 81, middle step 82, lower step 83, and invert arch 84 of the main tunnel, gradually forming a normal work sequence. After the excavation and support are completed, invert arch 84 will be poured and filled with concrete in a timely manner to close the support structure into a ring as soon as possible, improve stability, and ensure construction safety. In the direction of the greater mileage 91, a 50m long invert arch 84 and its filling will be poured. After the concrete filling of invert arch 84 reaches 100% strength, the secondary lining trolley track will be laid on the filling surface, and the secondary lining trolley formwork will be assembled. Starting from the direction of the greater mileage 91, the secondary lining will be poured towards the direction of the lesser mileage 92, completing the cantilever construction of the inclined shaft 1 leading to the main tunnel 8.

[0092] The intersection section of inclined shaft 1 is supported by a combination of the upper arch frame 4 and the reinforcing ring 6 of the gantry. The reinforcing ring 6 of the gantry adopts an integral structure formed by three cantilevered gantry frames 61, a sleeve arch 62, a lining formwork arch 63, and concrete pouring, which significantly improves the support strength of the intersection section and ensures the safety of cantilevered construction of large-section tunnels in soft and water-rich strata.

[0093] See Figure 10 The settlement of the arch and the convergence rate and cumulative deformation of the surrounding area are all within the allowable range. The support structure of the intersection section is stable. On-site deformation monitoring results show that the deformation of the main tunnel can be controlled under the combined support of the upper arch frame 4 and the reinforcing ring 6. By temporarily supporting the intersection section with the upper arch frame 4, the reinforcing ring 6 of the gantry can be installed after the completion of the tunnel 5. This allows the construction personnel to work under the combined support of the upper arch frame 4 and the reinforcing ring 6, which greatly reduces the over-excavation and convergence deformation of the surrounding rock. It avoids the construction risks caused by the lack of support and one-time construction of the gantry in the traditional gantry method, and quickly and effectively solves the technical problem of gantry construction at intersections under complex geological conditions.

[0094] Furthermore, this embodiment optimizes the construction schedule by rationally arranging the construction sequence, reducing the construction time from the cross passage section to the cantilevered guide tunnel section by more than 20 days, saving nearly half the construction time compared to traditional methods. Its advantages are specifically manifested in the following ways: By temporarily supporting the intersection section with the upper arch frame 4 of the gantry, the cantilevered guide tunnel 5 and the inclined shaft are constructed simultaneously on each working face. After the cantilevered gantry 61 is constructed to the outside of the upper step 81 of the main tunnel and the lower step of the inclined shaft is completed, the reinforcing ring 6 of the gantry at the intersection section is constructed, saving support time at the intersection section. This allows for parallel construction of the cantilevered guide tunnel 5 and the inclined shaft 1, accelerating the construction progress of the intersection section from the inclined shaft 1 into the main tunnel 8.

[0095] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata, characterized in that: Includes the following steps: S1. Inclined shaft curved wall lining (2) support: S1-1. Excavation and support of the upper bench of the inclined shaft (1): The upper section of the inclined shaft (1) is excavated and the curved wall lining (2) is installed. The initial support adopts a combination of steel arch frame, system anchor rod, steel mesh and concrete support. S1-2. Inclined Shaft (1) Lower Bench Excavation and Support: The lower section of the inclined shaft (1) is excavated and the curved wall lining (2) is installed. The lower section of the inclined shaft (1) is excavated by alternating left and right sides. The initial support adopts a combination of steel arch frame, system anchor rod, steel mesh and concrete support. S2. Inclined shaft straight wall lining (3) support: At a first predetermined distance inside the main tunnel excavation outline (85), the inclined shaft (1) is excavated using the step method after the bottom surface is lowered and supported by straight wall lining (3), and anchor mesh spraying combined support is applied. S3. Upper arch support (4) of the portal frame: At the second predetermined distance inside the main tunnel excavation outline (85), the upper section of the inclined shaft (1) is supported by the upper arch frame (4) of the gantry and the anchor mesh spraying combined support is applied. After the lower step of the inclined shaft (1) is excavated, the lower section of the upper arch frame (4) of the gantry is supported. S4. Excavation and support of the top guide tunnel (5): In the direction perpendicular to the tunnel axis of the main tunnel (8), along the excavation outline (85) of the main tunnel and with reserved deformation, the inclined shaft (1) is excavated and supported by the top-lifting guide tunnel (5); S5. Gantry reinforcement ring (6) support: When the top guide tunnel (5) is excavated and supported until the bottom of the upper step outside the main tunnel excavation outline (85), and the lower section of the upper arch frame (4) of the portal frame is supported to the inner side of the main tunnel excavation outline (85), the portal frame reinforcing ring (6) of the intersection section is supported. The portal frame reinforcing ring (6) is an integral structure formed by several top portal frames (61), sleeve arch (62), lining formwork arch (63) and concrete pouring. S6. Support for the main tunnel section of the pilot tunnel with top support: After the gantry reinforcement ring (6) is stabilized, the main tunnel irregular arch frame (7) is constructed and anchor mesh spraying combined support is implemented; S7. Excavation and support of the upper step of the main tunnel (81): After the support of the main tunnel irregular arch frame (7) is completed, the column on one side of the cantilever guide tunnel (5) is removed and the upper step (81) of the main tunnel is excavated and supported along this direction. When the predetermined construction space is met, each working face of the upper step (81) of the main tunnel is excavated and supported simultaneously. S8. Excavation and support of the upper bench (81) and middle bench (82) of the main tunnel: After the working face of the upper step (81) of the main tunnel has been constructed for a sufficient distance, the excavation and support of the middle step (82) of the main tunnel within the width of the top guide tunnel (5) will be carried out. After the middle step (82) of the main tunnel is constructed in one direction, the working face of each working face of the upper step (81) and the middle step (82) of the main tunnel will be excavated and supported simultaneously. S9. Excavation and support of the upper bench (81), middle bench (82), and lower bench (83) of the main tunnel: After the upper step (81) and middle step (82) of the main tunnel are constructed to a sufficient distance, the lower step (83) of the main tunnel within the width of the top guide tunnel (5) is excavated and supported. After the lower step (83) of the main tunnel is constructed to a sufficient distance in one direction, each working face of the upper step (81), middle step (82) and lower step (83) of the main tunnel is excavated and supported simultaneously until three steps are formed. S10. Excavation and support of the upper step (81), middle step (82), lower step (83), and invert arch (84) of the main tunnel: Once the three steps are formed and there is sufficient space for construction, the invert arch (84) is excavated and supported. Then, the upper step (81), middle step (82), lower step (83) and invert arch (84) of the main tunnel are constructed simultaneously, and secondary lining is carried out in one direction to form a normal work procedure, thus completing the top construction of the inclined shaft (1) into the main tunnel (8).

2. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 1, characterized in that: In step S1, if the surrounding rock is good, the excavation method of the inclined shaft (1) is to use a manual pneumatic pick in conjunction with an excavator; if the surrounding rock is poor, the excavation method of the inclined shaft (1) is to use controlled blasting.

3. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 1, characterized in that... In step S2, the first predetermined distance is 1m to 5m, the height of the bottom surface of the inclined shaft (1) after being lowered is 50cm to 100cm, the arch height of the straight wall lining (3) is the same as the arch height of the curved wall lining (2), and the installation width of the portal frame reinforcing ring (6) is reserved within the width range of the straight wall lining (3).

4. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 1, characterized in that: In step S3, the second predetermined distance is the thickness of the gantry reinforcing ring (6), the arch height of the upper arch frame (4) of the gantry is the arch height of the cantilever guide hole (5), and the arch curvature of the upper arch frame (4) of the gantry should ensure that the inner side of the irregular arch frame (7) of the main hole is placed on the gantry reinforcing ring (6).

5. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 1, characterized in that: In step S4, the arch height of the top guide tunnel (5) is the height of the relatively horizontal entry into the main tunnel excavation outline (85), the width of the top guide tunnel (5) is 1 / 3 to 1 / 2 of the width of the upper arch frame (4) of the portal frame, the cross-sectional shape of the top guide tunnel (5) is trapezoidal or arched, and the top guide tunnel (5) adopts a combination of steel arch frame, system anchor rod, steel mesh and concrete support, and the surrounding rock is sealed by sprayed plain concrete on both sides of the side walls.

6. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 1, characterized in that: In step S5, the height of the support beam of the gantry reinforcing ring (6) is the same as the height of the arch foot of the upper arch frame (4) of the gantry, and the width of the gantry reinforcing ring (6) is the width of the vertical side wall of the upper arch frame (4) of the gantry, so as to ensure that the two are closely fitted and erected.

7. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 6, characterized in that... During the construction of the portal frame reinforcing ring (6), the cantilevered portal frame (61) and the arch (62) are supported and the steel bars are tied from the inside to the outside. Then the lining arch (63) is hung and concrete is poured to form an integral structure.

8. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 1, characterized in that: In step S6, the support range of the main tunnel irregular arch frame (7) is the width of the top guide tunnel (5). The inner side of the main tunnel irregular arch frame (7) is placed on the support beam of the portal frame reinforcing ring (6), and the outer side is placed on the bottom rock layer outside the main tunnel excavation outline (85).

9. The method for constructing a large-section tunnel with inclined shaft in soft, water-rich strata using the method described in claim 1, characterized in that: The inclined shaft curved wall lining (2), straight wall lining (3), and upper arch frame (4) are connected in the longitudinal and radial directions by longitudinal connecting bars and connecting plates, respectively.

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