A tunnel structure and construction method

Abstract

The present invention discloses a tunnel structure and a construction method. The tunnel structure includes an excavated tunnel section and a pipe-jacking tunnel section. The excavated tunnel section includes a pipe-jacking tunnel section, a first cast-in-situ tunnel section, and a second cast-in-situ tunnel section connected in sequence. The pipe-jacking tunnel section includes a first shotcrete primary lining and a precast segment secondary lining. The first cast-in-situ tunnel section includes a second shotcrete primary lining and a first cast-in-situ reinforced concrete secondary lining. The first shotcrete primary lining and the second shotcrete primary lining are an integral structure. The precast segment secondary lining and the first cast-in-situ reinforced concrete secondary lining are connected. The second cast-in-situ tunnel section includes a primary lining support structure and a second cast-in-situ reinforced concrete secondary lining. The proximal end of the second cast-in-situ reinforced concrete secondary lining is connected to the pipe-jacking tunnel section, and the distal end is connected to the first cast-in-situ reinforced concrete secondary lining. The distal end of the primary lining support structure is connected to the second shotcrete primary lining. This tunnel structure solves the construction problems in the curved section.

Description

Technical Field

[0001] The present invention is used in the technical field of underground engineering, and particularly relates to a tunnel structure and a construction method. Background Art

[0002] In the construction of non-excavation underground engineering curved pipe jacking in cities, technical problems often occur that the smaller the jacking curvature radius of the pipe jacking and the larger the pipe diameter, the larger the opening width between pipe joints and the easier it is for the pipes to become disconnected. Moreover, the curved pipe jacking section is located underground in urban traffic arteries. In the case of the open cut method, traffic diversion is required, which easily causes traffic congestion. And due to the small construction site on-site, the on-site construction management difficulty increases, and there are great safety hazards. The shallow tunneling method is developed on the basis of the New Austrian Tunneling Method, using a composite lining to jointly bear the load. Its structural form is flexible and changeable, the tunnel alignment control is relatively easy to control, the demolition and land occupation are less, and the disturbance to residents is less, etc. However, its construction labor intensity is large and the work efficiency is low. Summary of the Invention

[0003] An object of the present invention is to solve at least one of the technical problems existing in the prior art, and provide a tunnel structure and a construction method, which can reduce the construction land occupation and improve the construction efficiency.

[0004] The technical solution adopted by the present invention to solve its technical problems is:

[0005] A tunnel structure includes a mined tunnel section and a pipe jacking tunnel section. The mined tunnel section includes a pipe jacking tunnel section, a first cast-in-place tunnel section, and a second cast-in-place tunnel section connected in sequence. The pipe jacking tunnel section includes a first shotcrete primary lining and a precast pipe joint secondary lining. The first cast-in-place tunnel section includes a second shotcrete primary lining and a first cast-in-place reinforced concrete secondary lining. The first shotcrete primary lining and the second shotcrete primary lining are an integral structure. The precast pipe joint secondary lining and the first cast-in-place reinforced concrete secondary lining are connected. The second cast-in-place tunnel section includes a primary lining support structure and a second cast-in-place reinforced concrete secondary lining. The proximal end of the second cast-in-place reinforced concrete secondary lining is connected to the pipe jacking tunnel section, and the distal end is connected to the first cast-in-place reinforced concrete secondary lining. The distal end of the primary lining support structure is connected to the second shotcrete primary lining.

[0006] Preferably, the cross-sectional structure of the pipe jacking tunnel section from outside to inside is sequentially first advanced small duct pre-grouting, first advanced large pipe shed support, the first shotcrete primary lining, backfill mortar, and the precast pipe joint secondary lining.

[0007] Preferably, the cross-sectional structure of the first cast-in-place tunnel section from outside to inside is sequentially second advanced small duct pre-grouting, second advanced large pipe shed support, the second shotcrete primary lining, waterproof layer, and the first cast-in-place reinforced concrete secondary lining.

[0008] Preferably, the second shotcrete primary lining is in a curved structure, the first cast-in-place reinforced concrete secondary lining is in a curved structure, and the first cast-in-place reinforced concrete secondary lining is a cast-in-place structure.

[0009] Preferably, the precast segment secondary lining is constructed by jacking, and the proximal end of the precast segment secondary lining and the distal end of the first cast-in-place reinforced concrete secondary lining are provided with mutually matching L-shaped interfaces. A steel bar coupler is provided in the construction joint between the precast segment secondary lining and the first cast-in-place reinforced concrete secondary lining, and the two ends of the steel bar coupler are respectively welded to the reserved steel bars in the precast segment secondary lining and the steel bars in the first cast-in-place reinforced concrete secondary lining.

[0010] Preferably, the overlapping length of the first cast-in-place reinforced concrete secondary lining and the second cast-in-place tunnel section is not less than 500 mm.

[0011] Preferably, the pipe-jacking method tunnel section is constructed by a pipe-jacking machine, and the primary lining support structure is formed by discarding the shell of the pipe-jacking machine in the mined tunnel section.

[0012] Preferably, a working shaft is provided at the distal end of the pipe-jacking tunnel section.

[0013] Preferably, the proximal end of the first cast-in-place reinforced concrete secondary lining is provided with an L-shaped interface, the distal end of the second cast-in-place reinforced concrete secondary lining is matched with the L-shaped interface, and a first construction joint along the radial direction of the tunnel and a second construction joint along the length direction of the tunnel are provided between the first cast-in-place reinforced concrete secondary lining and the second cast-in-place reinforced concrete secondary lining. The first construction joint is filled with a polyurethane foam board, the second construction joint is filled with a stainless steel ring, and polyurethane foam is provided in the stainless steel ring. A waterstop is provided between the first cast-in-place reinforced concrete secondary lining and the second cast-in-place reinforced concrete secondary lining, and the waterstop is located inside the second construction joint.

[0014] The present invention also provides a construction method using this tunnel structure, including the following steps:

[0015] Step 1: Using a pipe-jacking machine, jacking construction to form the pipe-jacking method tunnel section;

[0016] Step 2: Excavating the mined tunnel section, and constructing the first shotcrete primary lining and the second shotcrete primary lining;

[0017] Step 3: Disassembling the pipe-jacking machine, using the shell of the pipe-jacking machine as the primary lining support structure, and cast-in-place construction to form the second cast-in-place reinforced concrete secondary lining;

[0018] Step 4: Constructing the precast segment secondary lining by the pipe-jacking method;

[0019] Step Five: Fill the space between the precast segment secondary lining and the first shotcrete primary lining;

[0020] Step Six: Pour in-situ concrete between the precast segment secondary lining and the second cast-in-place reinforced concrete secondary lining to form the first cast-in-place reinforced concrete secondary lining.

[0021] One of the technical solutions in the above technical solutions has at least the following advantages or beneficial effects: By setting the first cast-in-place tunnel section and the second cast-in-place tunnel section, the pipe-jacking tunnel section and the pipe-pushing tunnel section are connected. The second shotcrete primary lining and the first cast-in-place reinforced concrete secondary lining are designed as curved structures during construction. This can not only solve the technical problems of curved pipe-jacking under traffic arteries and achieve connection through the cast-in-place curved section, but also avoid excavation affecting road traffic. The construction method of this tunnel structure is simple, ensuring the safety of the construction process and efficiently completing the tunnel construction work content.

[0022] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0024] Figure 1 is one of the schematic structural diagrams of an embodiment of the tunnel structure of the present invention;

[0025] Figure 2 is another schematic structural diagram of an embodiment of the tunnel structure of the present invention;

[0026] Figure 3 is the cross-sectional structural diagram of the first cast-in-place tunnel section of the present invention;

[0027] Figure 4 is the connection structural diagram of the pipe-pushing tunnel section and the first cast-in-place tunnel section of the present invention;

[0028] Figure 5 is the cross-sectional structural diagram of the pipe-pushing tunnel section of the present invention;

[0029] Figure 6 The connection structural diagram of the first cast-in-place tunnel section and the second cast-in-place tunnel section of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The function of the drawings is to supplement the description in the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention. However, it should not be construed as a limitation on the protection scope of the present invention.

[0031] In the present invention, when directions (up, down, left, right, front, and back) are described, it is only for the convenience of describing the technical solution of the present invention, rather than indicating or implying that the technical features referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present invention.

[0032] In the present invention, the meaning of "several" is one or more, the meaning of "multiple" is two or more, and "greater than", "less than", "exceeding", etc. are understood as not including the recited number; "above", "below", "within", etc. are understood as including the recited number. In the description of the present invention, if "first" and "second" are described, they are only used for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or the sequence relationship of the indicated technical features.

[0033] In the present invention, unless otherwise clearly defined, terms such as "set", "installed", "connected", etc. should be understood in a broad sense. For example, they can be directly connected, or indirectly connected through an intermediate medium; they can be fixedly connected, or detachably connected, or integrally formed; they can be mechanically connected, or electrically connected or capable of communicating with each other; they can be the communication inside two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meaning of the above terms in the present invention in combination with the specific content of the technical solution.

[0034] Among them, Figure 1 、 Figure 2 、 Figure 4 and Figure 6 give the reference direction coordinate system of the embodiments of the present invention. The following will describe the embodiments of the present invention in combination with the directions shown in Figure 1 、 Figure 2 、 Figure 4 and Figure 6 shown.

[0035] The embodiments of the present invention provide a tunnel structure. Refer to Figure 1, including a mined tunnel section and a pipe-jacking tunnel section 400. The mined tunnel section includes a pipe-jacking tunnel section 100, a first cast-in-situ tunnel section 200, and a second cast-in-situ tunnel section 300 that are connected in sequence. The pipe-jacking tunnel section 100 includes a first shotcrete primary lining 110 and a precast segment secondary lining 120. The first cast-in-situ tunnel section 200 includes a second shotcrete primary lining 210 and a first cast-in-situ reinforced concrete secondary lining 220. The first shotcrete primary lining 110 and the second shotcrete primary lining 210 are an integral structure. The precast segment secondary lining 120 and the first cast-in-situ reinforced concrete secondary lining 220 are connected. The second cast-in-situ tunnel section 300 includes a primary lining support structure 310 and a second cast-in-situ reinforced concrete secondary lining 320. The proximal end of the second cast-in-situ reinforced concrete secondary lining 320 is connected to the pipe-jacking tunnel section 400, and the distal end is connected to the first cast-in-situ reinforced concrete secondary lining 220. The distal end of the primary lining support structure 310 is connected to the second shotcrete primary lining 210. By setting the first cast-in-situ tunnel section 200 and the second cast-in-situ tunnel section 300, this tunnel structure connects the pipe-jacking tunnel section 100 and the pipe-jacking tunnel section 400. The second shotcrete primary lining 210 and the first cast-in-situ reinforced concrete secondary lining 220 are designed as curved structures during construction, which can not only solve the technical problems of curved pipe-jacking under traffic arteries and achieve connection through the cast-in-situ curved section, but also avoid excavation affecting road traffic and ensure the safety of the construction process, and efficiently complete the tunnel construction work content.

[0036] See Figure 5 , the cross-sectional structure of the pipe-jacking tunnel section 100 from outside to inside is successively a first advanced small pipe pre-grouting 130, a first advanced large pipe shed support 140, a first shotcrete primary lining 110, a backfill mortar 150, and a precast segment secondary lining 120.

[0037] See Figure 3 , the cross-sectional structure of the first cast-in-situ tunnel section 200 from outside to inside is successively a second advanced small pipe pre-grouting 230, a second advanced large pipe shed support 240, a second shotcrete primary lining 210, a waterproof layer 250, and a first cast-in-situ reinforced concrete secondary lining 220.

[0038] See Figure 1 , the second shotcrete primary lining 210 is a curved structure, the first cast-in-situ reinforced concrete secondary lining 220 is a curved structure, and the first cast-in-situ reinforced concrete secondary lining 220 is a cast-in-situ structure.

[0039] In some embodiments, see Figure 4, the precast segment secondary lining 120 is constructed by jacking. The proximal end of the precast segment secondary lining 120 and the distal end of the first cast-in-place reinforced concrete secondary lining 220 are provided with mutually matching L-shaped interfaces. A steel bar coupler is provided in the construction joint between the precast segment secondary lining 120 and the first cast-in-place reinforced concrete secondary lining 220. The two ends of the steel bar coupler are respectively welded and connected to the reserved steel bars in the precast segment secondary lining 120 and the steel bars in the first cast-in-place reinforced concrete secondary lining 220.

[0040] Preferably, referring to Figure 6 , the overlapping length of the first cast-in-place reinforced concrete secondary lining 220 and the second cast-in-place tunnel segment 300 is not less than 500 mm.

[0041] As a preferred embodiment of the present invention, referring to Figure 6 , the pipe jacking method tunnel segment 400 is constructed using a pipe jacking machine, and the primary lining support structure 310 is formed by discarding the shell and disassembling it inside the mined tunnel segment by the pipe jacking machine.

[0042] Referring to Figure 1 、 Figure 2 , a working shaft 500 is provided at the distal end of the pipe jacking tunnel segment 100 to facilitate jacking construction.

[0043] Referring to Figure 6 , the proximal end of the first cast-in-place reinforced concrete secondary lining 220 is provided with an L-shaped interface, the distal end of the second cast-in-place reinforced concrete secondary lining 320 is matched with the L-shaped interface, and a first construction joint along the radial direction of the tunnel and a second construction joint along the length direction of the tunnel are provided between the first cast-in-place reinforced concrete secondary lining 220 and the second cast-in-place reinforced concrete secondary lining 320. The first construction joint is filled with a polyurethane foam board 330, the second construction joint is filled with a stainless steel ring 340, polyurethane foam is provided inside the stainless steel ring 340, and a waterstop 350 is provided between the first cast-in-place reinforced concrete secondary lining 220 and the second cast-in-place reinforced concrete secondary lining 320. The waterstop 350 is located inside the second construction joint. Preferably, a PVC back-mounted waterstop.

[0044] The present invention also provides a construction method using the tunnel structure, including the following steps:

[0045] Step 1: Use a pipe jacking machine to jack and construct to form a pipe jacking method tunnel segment 400, which specifically includes the following steps:

[0046] (1) After completing all preparatory work before pipe jacking construction, start jacking construction. During the jacking process, thixotropic mud is injected outside the pipe wall to reduce the frictional resistance. To reduce the loss of mud, high-density mud is used for resistance reduction. Stop the machine when reaching the designed position of the pipe jacking section;

[0047] (2) Before the pipe jacking machine stops, it is necessary to fully demonstrate various risk factors after shutdown, and control the slurry inflow and outflow in the last 30 cm of jacking, that is, gradually reduce the slurry inflow and outflow. The earth pressure is controlled at 0.12 MPa (normally 0.08 MPa), stop injecting water into the excavation face, leave the soil blocks under the cutter head chips in the mud chamber, and fill the mud chamber to form a dry soil state. After stopping jacking, continue to extend the deviation correction jack by 5 cm, press the front soil body into the mud chamber, and form a stable soil body with the soil body in front of the cutter head, so that the soil body above the pipe jacking machine head remains stable and does not settle during the driving process. To ensure the stability of the soil body in the mud chamber, grout the soil body in the mud chamber in a timely manner according to the pressure maintenance situation of the machine head in the next step;

[0048] (3) After the pipe jacking machine stops, strengthen the inspection in the tunnel, pay attention to observing the changes of the pipe segments and the water seepage at the pipe joints, strengthen the monitoring on the ground, pay attention to observing the post-construction settlement. In case of emergencies, deal with them in a timely manner. Conduct on-site tests on the backfilling grouting of the pipeline to determine the test mix ratio and make technical preparations for grouting. After removing various equipment in the tunnel, immediately carry out slurry replacement at the back of the pipe and joint water stop sealing treatment to reduce the post-construction settlement of the tunnel. Install measurement control points at the position where the machine head is parked, and it is advisable to measure them every day, paying attention to observing the settlement change trend. The frequency of measuring the post-construction settlement of the tunnel can be appropriately reduced. According to the layout of the measurement points during the construction process, it is advisable to measure at an interval of 50 m;

[0049] Step 2: Excavate the section of the mined tunnel, and construct the first shotcrete primary lining 110 and the second shotcrete primary lining 210. Specifically, it includes the following steps;

[0050] (1) The first advanced large pipe shed support 140 and the second advanced large pipe shed support 240 adopt the follow-up pipe shed construction technology, which uses the pipe shed as the drill pipe, is guided by the drill pipe, and is equipped with a guidance instrument at the same time. The signal from the sensor located in the drill bit is directly transmitted to the remote display through the cable in the drill pipe to monitor the drilling direction of the drill bit in real time. According to the driving length, design the drilling trajectory of the line (preset drilling angle), and drill under the monitoring of the guidance system. During drilling, high-pressure liquid passes through the drill pipe and the pipe shed steel pipe and shoots out from the front section of the drill bit to scour the front soil body. At the same time, the drill pipe rotates and advances forward. The deviation correction of the pipe shed is mainly achieved by using a special guiding drilling duck (oblique) plate bit. After completing the follow-up drilling depth, withdraw the internal guiding device, then seal the pipe orifice, and inject cement slurry or cement mortar into the inside to increase the stiffness of the pipe shed;

[0051] (2) The construction of the first advanced small duct pre-grouting 130 and the second advanced small duct pre-grouting 230 is planned to use an electric drill for drilling. When inserting the pipe, an electric hammer is started to vibrate it into place. The grouting is carried out using a grouting pump. The small duct is made of a steel pipe with a diameter of Φ42mm and is set outside the arch primary support steel frame. The elevation angle and the outward inclination angle are 8° - 10°. The front end is processed into a tapered shape, and Φ8 - 10mm slurry overflow holes are drilled in the middle part, arranged in a plum blossom pattern, with a circumferential spacing of 300mm. No holes are drilled within 1.0m at the tail to prevent slurry leakage. The grouting slurry for the small duct is selected and prepared according to the geological conditions of this project and the design requirements. The slurry ratio is determined according to the maintenance of the test equipment. The setting time is determined according to the actual situation, generally 8 - 10min. The initial grouting pressure is planned to be 0.3MPa, and the final pressure is 1.0Mpa. After the grouting pipe is connected, before grouting, a water pressure test is first carried out to check whether the pipeline is unobstructed, and then the grouting pump is started to inject the slurry into the formation for reinforcement. After the large-scale excavation, there is no ground heave, the working face does not collapse, and there is basically no water seepage. The main construction methods of the advanced pre-grouting in front of the tunnel are as follows:

[0052] 1) Grouting cycle length: One cycle for every 10m, and a 2m range is reserved as the grouting stopping slurry layer for the next cycle; The curtain grouting is constructed in two sequences, and the second sequence serves as the inspection hole and supplementary grouting hole for the first sequence construction;

[0053] 2) Spacing of grouting hole arrangement: The general circumferential spacing is 1.5m, the outward inclination angle of the first sequence holes is 8°, and that of the second sequence holes is 6°;

[0054] 3) Grouting method: Adopt the advancing type of sectional grouting;

[0055] 4) The grouting slurry uses single-component cement slurry, and the grouting pressure is 0.5 - 1.5MPa (hole mouth pressure), which can be modified according to the actual construction situation on site;

[0056] 5) Before grouting, a temporary plugging wall with a thickness of 30cm needs to be constructed on the heading face using double-layer shotcrete with wire mesh. The wire mesh uses Φ14@×150×150 wire mesh sheets, and at the same time, the edges of the mesh sheets need to be connected to the tunnel grid. The temporary plugging wall needs to be constructed by spraying concrete in layers to ensure the sealing effect of the plugging wall;

[0057] 6) Advanced drilling is carried out on the heading face after the curtain grouting construction is completed and before the tunnel excavation. When the leakage water volume is large and the surrounding rock stability is poor, supplementary pressure grouting is carried out again;

[0058] The excavation method is the bench method, which is divided into the upper and lower benches. The two benches are excavated with a 2m difference. The longitudinal spacing of the grids is 500mm. The main reinforcement cover thickness on the side close to the surrounding rock is 50mm, and the main reinforcement cover thickness on the free side is 30mm. Two locking foot bolts are installed for each set of steel frames. The grids are connected by HRB400 Φ22@1000. The connecting steel bars are welded to the main reinforcement of the grid steel frame. The steel mesh is Ф6@150×150mm, and it is arranged in double layers inside and outside the steel frame. The shotcrete uses C25 early-strength concrete with an impermeability grade of P6 and a thickness of 300mm. The grid steel frame is fabricated in sections by cold bending in the steel bar processing yard, and the sections are connected by angle steels and bolts. After passing the trial assembly inspection, it can be installed. The fabricated grid steel frame is smooth; its allowable deviations are: the rise and arc length of the grid +20mm, the length of the frame ±20mm; after the grid steel frames are assembled, they should be in the same plane, and the allowable deviation of the cross-sectional dimension is ±20mm, and the distortion is 20mm. The steel mesh is welded with grade I Ф6 steel bars, and the spacing of the steel mesh is 150×150mm. When the excavation of the mined tunnel reaches 5m in front of the cutter head of the pipe jacking machine, holes need to be drilled in the upper, middle, and lower parts of the tunnel to detect whether the soil layer in front is softened due to the disturbance of the pipe jacking cutter head, or whether there are holes between the cutter head surface and the soil mass resulting in a water leakage incident. When constructing the advanced pipe shed, the overlapping length of the pipe shed steel pipe and the outer shell of the pipe jacking machine is not less than 1.0m. The soil is excavated to 0.5m from the outer shell of the pipe jacking machine, and the "steel grid + concrete" primary lining is adopted. The gap between the primary lining and the shell is filled with concrete.

[0059] Step 3: Dismantle the pipe jacking machine. The outer shell of the pipe jacking machine is used as the primary lining support structure, and the second cast-in-place reinforced concrete secondary lining 320 is formed by in-situ construction. Specifically:

[0060] (1) In this project, a slurry shield pipe jacking machine is used, and its main structures mainly include a chip breaking system, a power system, a deviation correction and hydraulic system, an outer shell, an in-machine mud inlet and outlet system, a measurement and display system, an electrical operation system, etc.;

[0061] (2) The disassembly process of the pipe jacking machine head: The soil in front of the cutter head and in the slurry chamber is consolidated → Stop the machine and seal all passages → Dismantle the measurement system → Dismantle the electrical control and monitoring system → Dismantle the hydraulic system → Dismantle the cutter head power and transmission system → The mined tunnel is excavated to the cutter head position by the mined method → Dismantle the cutting system → Dismantle the sealing and lubrication system;

[0062] (3) After the abandoned shell of the pipe jacking machine is disassembled and disintegrated, the abandoned shell primary lining is stable, and the second cast-in-place reinforced concrete secondary lining 320 is constructed in a timely manner. The thickness of the abandoned shell tunnel is the same as that of the precast pipe section of the pipe jacking, and the joint surface is smooth;

[0063] Step 4: The precast segment secondary lining 120 is constructed by the pipe jacking method. Specifically: The pipe jacking tunnel section 100 and the first cast-in-place tunnel section 200 are connected by an arc. The propulsion principle of the pipe jacking method is similar to that of the pipe jacking method. Both apply a jacking force behind the pipe segment to make the pipe segment enter the tunnel. Since the thrust is not large, four jacks are used for jacking construction. The jacks are evenly arranged along the cross-section of the pipe segment. To reduce the friction between the pipe segment and the primary lining, a guiding platform needs to be constructed at the bottom of the tunnel. The guiding platform supports the precast concrete pipe segment and guides its advancement. The longitudinal guide rails are two parallel I30a steel beams with an included angle of 60°. The transverse guide rails are I15a, which are welded to the longitudinal guide rails to fix the position of the longitudinal guide rails. The bottom of the guiding platform is fixed to the tunnel with expansion bolts. The guiding platform extends 5 m at the tunnel entrance so that the pipe segment can be smoothly jacked into the tunnel;

[0064] Step 5: Fill the space between the precast segment secondary lining 120 and the first shotcrete primary lining 110. After the I-beam guide rails are installed at the bottom of the precast segment secondary lining 120 and the first shotcrete primary lining 110, plastic plain concrete is backfilled, and the contact surface is shaped into a circle consistent with the outer diameter of the pipe segment. The upper void is filled with high-fluidity premixed mortar. Φ100 grouting pipes are reserved in the middle and upper parts of the tunnel. The specific grouting process is as follows:

[0065] (1) Seal the lower void at the tunnel entrance;

[0066] (2) Fill the lower void through the reserved middle grouting pipe. The mortar flows from the inside of the void to the tunnel entrance for filling. When the mortar fills to the position of the middle grouting pipe, the middle grouting pipe is withdrawn and left to harden statically;

[0067] (3) After the lower mortar hardens, seal the upper void at the tunnel entrance;

[0068] (4) Fill the upper void through the reserved top grouting pipe. The mortar flows from the inside of the void to the tunnel entrance for filling. When it fills to the top position, the grouting pipe is withdrawn while grouting. When all the grouting pipes are withdrawn, the tunnel entrance is completely sealed;

[0069] (5) After the mortar in the void hardens, secondary grouting is carried out using the grouting holes of the precast pipe segment to ensure that the void is filled densely;

[0070] Step 6: Cast-in-place construction is carried out between the precast segment secondary lining 120 and the second cast-in-place reinforced concrete secondary lining 320 to form the first cast-in-place reinforced concrete secondary lining 220;

[0071] Step 7: Waterproof treatment of the interface construction joint. The construction joint between the first cast-in-place reinforced concrete secondary lining 220 and the second cast-in-place reinforced concrete secondary lining 320 is filled with a polyurethane foam board 330 and a stainless steel ring 340. The stainless steel ring 340 is provided with polyurethane foam. A waterstop 350 is provided between the first cast-in-place reinforced concrete secondary lining 220 and the second cast-in-place reinforced concrete secondary lining 320, and the waterstop 350 is located inside the second construction joint.

[0072] In the description of this specification, the description with reference to terms such as "example", "embodiment" or "some embodiments" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0073] Certainly, the present invention is not limited to the above embodiments. Those skilled in the art can make equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A tunnel structure, characterized in that: It includes a mined tunnel section and a pipe-jacking tunnel section. The mined tunnel section includes a pipe-jacking tunnel section, a first cast-in-place tunnel section, and a second cast-in-place tunnel section connected in sequence. The pipe-jacking tunnel section includes a first shotcrete primary lining and a precast segment secondary lining. The first cast-in-place tunnel section includes a second shotcrete primary lining and a first cast-in-place reinforced concrete secondary lining. The first shotcrete primary lining and the second shotcrete primary lining are an integral structure. The precast segment secondary lining is connected to the first cast-in-place reinforced concrete secondary lining. The second cast-in-place tunnel section includes a primary lining support structure and a second cast-in-place reinforced concrete secondary lining. The proximal end of the second cast-in-place reinforced concrete secondary lining is connected to the pipe-jacking tunnel section, and the distal end is connected to the first cast-in-place reinforced concrete secondary lining. The distal end of the primary lining support structure is connected to the second shotcrete primary lining. The cross-sectional structure of the pipe-jacking tunnel section from outside to inside is successively first advanced small duct pre-grouting, first advanced large pipe-shed support, the first shotcrete primary lining, backfill mortar, and the precast segment secondary lining. The cross-sectional structure of the first cast-in-place tunnel section from outside to inside is successively second advanced small duct pre-grouting, second advanced large pipe-shed support, the second shotcrete primary lining, waterproof layer, and the first cast-in-place reinforced concrete secondary lining. The second shotcrete primary lining is in a curved structure, the first cast-in-place reinforced concrete secondary lining is in a curved structure, and the first cast-in-place reinforced concrete secondary lining is a cast-in-place structure.

2. The tunnel structure according to claim 1, wherein: The precast segment secondary lining is constructed by jacking. The proximal end of the precast segment secondary lining and the distal end of the first cast-in-place reinforced concrete secondary lining are provided with mutually matching L-shaped interfaces. A steel bar coupler is provided in the construction joint between the precast segment secondary lining and the first cast-in-place reinforced concrete secondary lining. The two ends of the steel bar coupler are respectively welded to the reserved steel bars in the precast segment secondary lining and the steel bars in the first cast-in-place reinforced concrete secondary lining.

3. The tunnel structure according to claim 1, characterized in that: The overlapping length of the first cast-in-place reinforced concrete secondary lining and the second cast-in-place tunnel section is not less than 500 mm.

4. The tunnel structure according to claim 1, characterized in that: The pipe-jacking tunnel section is constructed using a pipe-jacking machine. The primary lining support structure is formed by the pipe-jacking machine discarding its shell and disassembling inside the mined tunnel section.

5. The tunnel structure according to claim 1, wherein: A working shaft is provided at the distal end of the pipe-jacking tunnel section.

6. The tunnel structure according to claim 1, wherein: The proximal end of the first cast-in-place reinforced concrete secondary lining is provided with an L-shaped interface. The distal end of the second cast-in-place reinforced concrete secondary lining is matched with the L-shaped interface. A first construction joint along the tunnel radial direction and a second construction joint along the tunnel length direction are provided between the first cast-in-place reinforced concrete secondary lining and the second cast-in-place reinforced concrete secondary lining. The first construction joint is filled with a polyurethane foam board. The second construction joint is filled with a stainless steel ring. The stainless steel ring is provided with polyurethane foam. A waterstop is provided between the first cast-in-place reinforced concrete secondary lining and the second cast-in-place reinforced concrete secondary lining. The waterstop is located inside the second construction joint.

7. A construction method using the tunnel structure according to any one of claims 1 to 6, characterized in that, It includes the following steps: Step 1: Use a pipe-jacking machine to jack and construct to form the pipe-jacking tunnel section; Step 2: Excavate the mined tunnel section, and construct the first shotcrete primary lining and the second shotcrete primary lining; Step 3: Dismantle the pipe jacking machine. The shell of the pipe jacking machine serves as the primary lining support structure, and the second cast-in-place reinforced concrete secondary lining is formed by in-situ construction; Step 4: Construct the precast pipe segment secondary lining by the pipe pushing method; Step 5: Fill the space between the precast pipe segment secondary lining and the first shotcrete primary lining; Step 6: Conduct in-situ construction between the precast pipe segment secondary lining and the second cast-in-place reinforced concrete secondary lining to form the first cast-in-place reinforced concrete secondary lining.

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