A prefabricated temporary invert, tunnel lining structure and its construction method

Abstract

A precast temporary inverted arch, a tunnel lining structure and a construction method thereof. The cross-section of the precast temporary inverted arch is arc-shaped. The precast unit plate includes a structural pile construction hole penetrating the plate body. A connecting end is provided on the front end face of the plate body, and a receiving end is provided on the rear end face. The receiving end cooperates with the connecting end, and inverted arch connecting pieces are respectively embedded in the middle of the left and right end faces of the plate body. The tunnel lining structure includes a primary support structure, a waterproof layer and a secondary lining structure. The primary support structure is formed by enclosing the precast temporary inverted arch and other primary support structures. The tunnel lining structure also includes a rock-socketed structural pile in the tunnel made of reinforced concrete. The present invention can effectively control the deformation of the stratum and the surrounding environment caused by the construction of a soft soil stratum tunnel by the drill and blast method, and has the advantages of quick installation, convenient structural pile construction, improved construction efficiency, etc., and can effectively improve the construction quality of the primary support of the soft soil stratum tunnel.

Description

Technical Field

[0001] The invention belongs to the field of tunnels, in particular to a prefabricated temporary invert for structural pile construction in a soft soil area and a construction method thereof. Background Art

[0002] With the development of underground space in my country, the deformation of the strata and surrounding buildings or structures caused by tunnel construction in soft soil areas has attracted attention. During the construction of the drill-and-blast tunnel, in order to avoid deformation in the tunnel and the impact on the surrounding environment, a temporary invert needs to be set up. The temporary invert and the initial support of the side wall are closed into a ring, which can effectively reduce the deformation of the tunnel and the strata and protect the safety of surrounding buildings or structures. The temporary invert generally adopts the same shotcrete and steel frame structure as the initial support of the side wall. In addition, due to the insufficient bearing capacity of the foundation of the soft soil stratum, structural piles need to be set up to ensure the safety and stability of the tunnel after it is put into operation.

[0003] However, the construction of tunnel structural piles by drilling and blasting in soft soil areas still has the following problems: a. The positioning of structural piles is prone to deviation, which affects the construction of the secondary lining and waterproof layer; b. The sprayed concrete at the temporary invert is not easy to be compacted, has insufficient strength, and has uneven thickness. When the construction machinery acts on the temporary invert in the later stage, cracks are likely to occur; c. During the construction of structural piles, holes need to be drilled in the temporary invert. The deviation of the invert steel frame causes the integrity and bearing capacity of the invert to be destroyed during the construction of structural piles. Summary of the invention

[0004] The purpose of the present invention is to provide a prefabricated temporary invert, a tunnel lining structure and a construction method thereof, which aims to solve the technical problem that the positioning of structural piles is prone to deviation, affecting the construction of secondary lining and waterproof layer, and the technical problem that the quality control of shotcrete at the temporary invert is difficult; and the technical problem that holes need to be drilled in the temporary invert during the construction of structural piles, and the deviation of the invert steel frame causes the integrity and bearing capacity of the invert to be destroyed during the construction of structural piles.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A prefabricated temporary inverted arch comprises an arch body of reinforced concrete, wherein the arch body is formed by longitudinally connecting prefabricated unit plates, wherein the cross section of the prefabricated unit plates is arc-shaped, and wherein the prefabricated unit plates comprise structural pile construction holes penetrating the plate body, wherein the structural pile construction holes are arranged in a row along the longitudinal direction of the plate body, wherein the front end face of the plate body is provided with a connecting end arranged along the longitudinal length of the plate body, wherein the rear end face of the plate body is provided with a receiving end arranged along the longitudinal length of the plate body and adapted to the connecting end, wherein the receiving end cooperates with the connecting end, and wherein the left and right end faces of the plate body are respectively centrally embedded with inverted arch connecting pieces.

[0007] Each prefabricated unit plate is provided with 1-2 rows of structural pile construction holes, and each row is provided with 2-4 structural pile construction holes.

[0008] Two adjacent prefabricated unit boards are connected longitudinally by a receiving end and a connecting end. The connecting end is provided with a through-length rib in the center, and the receiving end is provided with a through-length groove in the center. The rib and the groove cooperate with each other.

[0009] A tunnel lining structure comprises a primary support structure, a waterproof layer and a secondary lining structure, wherein the primary support structure is formed by enclosing a prefabricated temporary invert and other primary support structures, wherein the other primary support structures are primary support side walls and primary support vaults, and comprise primary support steel frames, primary support concrete and steel frame connectors.

[0010] The bottom end of the primary support steel frame is pre-buried with a steel frame connector, and the left and right end faces of the prefabricated temporary invert are fixedly connected to the steel frame connector through the invert connector respectively. The primary support concrete spraying covers the primary support steel frame, and also covers the invert connector and the steel frame connector. The prefabricated temporary invert and other primary support structures are enclosed to form a primary support structure. The waterproof layer is integrally laid on the inner wall surface of the primary support structure, and the secondary lining structure is integrally constructed on the inner wall surface of the waterproof layer.

[0011] The tunnel lining structure also includes reinforced concrete rock-embedded structural piles in the hole, the diameter of the rock-embedded structural piles in the hole is smaller than the diameter of the structural pile construction hole, the number of the rock-embedded structural piles in the hole is adapted to the number of the structural pile construction holes, the rock-embedded structural piles in the hole vertically penetrate the structural pile construction holes from bottom to top, the top of the rock-embedded structural piles in the hole is fixedly connected to the secondary lining structure, and the bottom of the rock-embedded structural piles in the hole is embedded in the tunnel surrounding rock.

[0012] The secondary lining structure is formed by enclosing a secondary lining invert, a secondary lining side wall and a secondary lining arch top. The top of the longitudinal reinforcement of the in-hole rock-embedded structural pile is fixedly connected to the main reinforcement of the secondary lining invert, and there is no connection between the in-hole rock-embedded structural pile and the prefabricated temporary invert.

[0013] The arc-shaped inner contour of the cross section of the prefabricated temporary inverted arch is adapted to the outer contour of the cross section of the secondary lining inverted arch; the primary support side wall is an arc-shaped structure, and its inner and outer contours of the cross section are adapted to the outer contour of the secondary lining side wall; the primary support arch is an arc-shaped structure, and its inner and outer contours of the cross section are adapted to the outer contour of the secondary lining arch.

[0014] The inverted arch connecting member is a rectangular steel plate, and the steel frame connecting member is a rectangular steel plate with the same size as the inverted arch connecting member. A first bolt connecting hole is opened on the inverted arch connecting member, and a second bolt connecting hole corresponding to the first bolt connecting hole is opened on the steel frame connecting member. The first bolt connecting hole is aligned with the second bolt connecting hole and is fixedly connected by connecting bolts.

[0015] The surface of the inverted arch connector is flush with the left and right end surfaces of the plate body, and the steel frame connector is fixedly connected to the outer surface of the primary support steel frame.

[0016] The connecting bolt includes a screw rod and nuts at both ends. The screw rod sequentially passes through the first bolt connection hole and the second bolt connection hole. The double nuts include a first nut embedded inside the precast temporary inverted arch and closely attached to the back side of the inverted arch connecting member, and also include a second nut fastened to the outside of the steel frame connecting member.

[0017] A construction method for a tunnel lining structure is as follows:

[0018] Step 1, design and precast of the precast temporary inverted arch: Make a template according to the tunnel primary support design drawing, then make a group of precast unit plates, embed the inverted arch connecting member into the precast unit plates, and precast according to the position, size and arrangement of the structural pile construction holes determined by the drawing;

[0019] Step 2, excavation of the upper soil body in the soft soil stratum tunnel: Excavate a section of the tunnel with the excavation footage being the same as the width of the precast unit plate, and use machinery to excavate in parts. First, excavate the upper soil body;

[0020] Step 3, erection of the primary support steel frame: Immediately after the excavation is completed, erect the primary support steel frame in the tunnel, and preset steel frame connecting members at the positions corresponding to the inverted arch connecting members on the primary support steel frame;

[0021] Step 4, excavation of the lower soil body and construction of the precast temporary inverted arch: When excavating to the inverted arch, ensure that the precast temporary inverted arch is in full contact with the soft soil stratum, then level the inverted arch site, place the precast temporary inverted arch at the designed position of the excavation section by mechanical hoisting, and then fixedly connect and close the loop between the inverted arch connecting member and the steel frame connecting member;

[0022] Step 5, closure of the primary support structure: Spray primary support concrete to cover the primary support steel frame, inverted arch connecting member and steel frame connecting member to form an operation cycle of the primary support structure;

[0023] Step 6, construction of the in - tunnel rock - socketed structural piles: Place the construction machinery for the in - tunnel rock - socketed structural piles on the precast temporary inverted arch, construct the in - tunnel rock - socketed structural piles on the surrounding rock. The top of the in - tunnel rock - socketed structural piles penetrates through the structural pile construction holes. The in - tunnel rock - socketed structural piles are completed one by one, and the in - tunnel rock - socketed structural piles and the precast temporary inverted arch are of a separated structure;

[0024] Step 7, construction of the waterproof layer: Construct the waterproof layer on the inner contour of the primary support structure; the waterproof layer between the in - tunnel rock - socketed structural piles and the secondary lining structure is constructed during the construction of the secondary lining;

[0025] Step 8, construction of the secondary lining structure: During the construction of the secondary lining structure, fixedly connect the top of the longitudinal bars of the in - tunnel rock - socketed structural piles with the main bars of the secondary lining inverted arch to form a permanent stress - bearing structure;

[0026] Step 9, construct the next operation cycle, and repeat Steps 2 to 3;

[0027] Step Ten: Level the invert site, place the precast unit slab at the excavation section, align the connection end of the next precast unit slab with the receiving end of the previous one, then connect them with mortise and tenon joints, and then fixedly connect the invert connecting piece and the steel frame connecting piece to form a closed loop;

[0028] Step Eleven: Repeat Steps Five to Eight to complete this operation cycle;

[0029] Step Twelve: Repeat Steps Nine to Eleven until the construction of the tunnel lining structure is completed.

[0030] In Step One, the width of the precast temporary invert is calculated and determined according to the formation conditions, formation parameters, burial depth, and deformation control standards of the surrounding environment to determine the form of the precast temporary invert. The form of the precast temporary invert includes thickness, width, concrete strength, and reinforcement. The width is 0.5m - 1.5m, which is determined according to the tunnel span, the width of the precast temporary invert, and the formation parameters. The length of the rock-socketed structure pile in the tunnel is determined according to the bedrock depth, and the rock-socketed depth is greater than 3m.

[0031] Compared with the prior art, the present invention has the following characteristics and beneficial effects:

[0032] The precast temporary invert of the present invention is a precast structure, which ensures the construction quality and stiffness of the temporary invert structure; it can be constructed immediately after excavation to control the formation deformation, and after being connected to the upper sidewall initial support structure through the reserved steel plate, it can accelerate the formation of a closed loop of the initial support, better and faster control the formation deformation, and ensure the construction safety.

[0033] Joints are provided between the precast unit slabs of the present invention, and the temporary invert forms a "beam" with great stiffness in the longitudinal direction of the tunnel, which can ensure the effective transfer of longitudinal loads, control the uneven settlement in the longitudinal direction of the tunnel, and also better control the stability of the tunnel face.

[0034] In the tunnel lining structure of the present invention, the inner contour of the precast temporary invert is consistent with the arc of the outer contour of the secondary lining invert, which can prevent stress concentration and the phenomenon of voids under the secondary lining invert while ensuring the construction quality of the secondary lining.

[0035] In the tunnel lining structure of the present invention, an in-tunnel rock-socketed structural pile for construction is further included. The in-tunnel rock-socketed structural pile can directly transfer the upper load to the bedrock, preventing uneven settlement of the stratum and structural deformation caused by subsequent stratum settlement. The precast temporary invert has a construction hole for the structural pile. While the precast temporary invert quickly closes into a ring with the shotcrete initial support of the side walls, it can also provide conditions such as positioning and site for the construction of the in-tunnel rock-socketed structural pile. The construction machinery for the structural pile will have higher stability when placed on this structure, ensuring the construction quality of the structural pile. Moreover, after the construction of the rock-socketed structural pile, it is completely separated from the precast temporary invert and integrated with the subsequent secondary lining, enabling the upper load to be smoothly transferred to the bedrock and ensuring that there is no uneven settlement of the stratum and structural deformation due to soil deformation during the operation period of the tunnel structure.

[0036] The present invention effectively controls the deformation of the stratum and the surrounding environment caused by the construction of a soft soil stratum tunnel by the drill and blast method, and has advantages such as quick installation, facilitating the construction of the structural pile, and improving construction efficiency, and can effectively improve the construction quality of the initial support of the soft soil stratum tunnel. Brief Description of the Drawings

[0037] The present invention will be further described in detail below with reference to the drawings.

[0038] Figure 1 It is a schematic structural diagram of the precast temporary invert.

[0039] Figure 2 is Figure 1 The schematic structural diagram of the A-A cross-section in

[0040] Figure 3 It is a schematic cross-sectional diagram of the tunnel lining structure of the present invention.

[0041] Figure 4 It is a partial enlarged schematic diagram of the tunnel lining structure.

[0042] Figure 5 It is a schematic structural diagram of the invert connecting piece.

[0043] Figure 6 It is a schematic structural diagram of the steel frame connecting piece.

[0044] Reference Signs: 1 - precast unit plate, 11 - construction hole for the structural pile, 12 - connecting end, 13 - receiving end, 14 - invert connecting piece, 2 - other structures of the initial support, 21 - initial support steel frame, 22 - steel frame connecting piece, 23 - initial support concrete, 3 - waterproof layer, 4 - secondary lining structure, 5 - in-tunnel rock-socketed structural pile, 6 - connecting bolt, 61 - screw rod, 62 - first nut, 63 - second nut, 7 - first bolt connection hole, 8 - second bolt connection hole. Detailed Description of the Embodiment

[0045] See the embodiment in Figure 1-2As shown in the figure, a precast temporary inverted arch includes an arch body made of reinforced concrete. The arch body is longitudinally connected by precast unit plates 1. The cross-section of the precast unit plate 1 is arc-shaped. The precast unit plate 1 includes a structural pile construction hole 11 penetrating through the plate body. The structural pile construction holes 11 are arranged in rows along the longitudinal direction of the plate body. A connecting end 12 extending longitudinally throughout the plate body is provided on the front end face of the plate body. A receiving end 13 extending longitudinally throughout the plate body and adapted to the connecting end 12 is provided on the rear end face of the plate body. The receiving end 13 cooperates with the connecting end 12. At the center of the left and right end faces of the plate body, inverted arch connecting pieces 14 are respectively embedded.

[0046] Each precast unit plate 1 is provided with 1 - 2 rows of structural pile construction holes 11, and 2 - 4 structural pile construction holes 11 are arranged in each row. In this embodiment, each precast unit plate 1 is provided with 2 rows of structural pile construction holes 11, and 2 structural pile construction holes 11 are arranged in each row. Adjacent two precast unit plates 1 are longitudinally connected by the cooperation of the receiving end 13 and the connecting end 12. A through-long convex rib is provided at the center of the connecting end 12, and a through-long groove is provided at the center of the receiving end 13. The convex rib and the groove are connected by tenon and mortise.

[0047] See Figures 3-6 As shown in the figure, a tunnel lining structure includes a primary support structure, a waterproof layer 3, and a secondary lining structure 4. The primary support structure is formed by enclosing a precast temporary inverted arch and other primary support structures. The other primary support structures 2 are primary support side walls and primary support arch crowns, including primary support steel frames 21, primary support concrete 23, and steel frame connecting pieces 22.

[0048] Steel frame connecting pieces 22 are embedded at the bottom ends of the primary support steel frames 21. The left and right end faces of the precast temporary inverted arch are respectively fixedly connected to the steel frame connecting pieces 22 through the inverted arch connecting pieces 14. The primary support concrete 23 is sprayed to cover the primary support steel frames 21, and also covers the inverted arch connecting pieces 14 and the steel frame connecting pieces 22. The precast temporary inverted arch and other primary support structures enclose to form the primary support structure. The waterproof layer 3 is integrally laid on the inner wall surface of the primary support structure. The secondary lining structure 4 is integrally constructed on the inner wall surface of the waterproof layer 3.

[0049] The tunnel lining structure further includes reinforced concrete in-tunnel rock-embedded structural piles 5. The diameter of the in-tunnel rock-embedded structural piles 5 is smaller than the diameter of the structural pile construction holes 11. The number of the in-tunnel rock-embedded structural piles 5 is adapted to the number of the structural pile construction holes 11. The in-tunnel rock-embedded structural piles 5 vertically penetrate through the structural pile construction holes 11 from bottom to top. The top of the in-tunnel rock-embedded structural piles 5 is fixedly connected to the secondary lining structure 4, and the bottom of the in-tunnel rock-embedded structural piles 5 is embedded in the tunnel surrounding rock.

[0050] The secondary lining structure 4 is formed by enclosing a secondary lining inverted arch, secondary lining side walls, and a secondary lining arch crown. The top of the longitudinal bars of the in - tunnel rock - socketed structural pile 5 is fixedly connected to the main bars of the secondary lining inverted arch, and there is no connection between the in - tunnel rock - socketed structural pile 5 and the precast temporary inverted arch.

[0051] The inner arc contour of the cross - section of the precast temporary inverted arch is adapted to the outer contour of the cross - section of the secondary lining inverted arch. The primary support side walls are arc - shaped structures, and both the inner and outer contours of their cross - sections are adapted to the outer contour of the secondary lining side walls. The primary support arch crown is an arc - shaped structure, and both the inner and outer contours of its cross - section are adapted to the outer contour of the secondary lining arch crown.

[0052] The surface of the inverted arch connecting piece 14 is flush with the left and right end faces of the plate body. The steel frame connecting piece 22 is fixedly connected to the outer side of the surface of the primary support steel frame 21. The inverted arch connecting piece 14 is a rectangular steel plate, and the steel frame connecting piece 22 is a rectangular steel plate with the same size as the inverted arch connecting piece 14. The first bolt connection holes 7 are opened on the inverted arch connecting piece 14, and the second bolt connection holes 8 corresponding to the first bolt connection holes 7 are opened on the steel frame connecting piece 22. The first bolt connection holes 7 and the second bolt connection holes 8 are aligned and fixedly connected by connection bolts 6. In this embodiment, four first bolt connection holes 7 and four second bolt connection holes 8 are provided at the four corners of each steel plate. The connection bolt 6 includes a screw rod 61 and nuts at both ends. The screw rod 61 sequentially passes through the first bolt connection hole 7 and the second bolt connection hole 8. The double - nut includes a first nut 62 embedded inside the precast temporary inverted arch and closely attached to the back side of the inverted arch connecting piece 14, and also includes a second nut 63 fastened to the outer side of the steel frame connecting piece 22.

[0053] A construction method for a tunnel lining structure is as follows:

[0054] Step 1, design and precast of the precast temporary inverted arch: Make a template according to the primary support design drawings of the tunnel, then make a group of precast unit plates 1, embed the inverted arch connecting piece 14 into the precast unit plates 1, and precast according to the position, size, and arrangement method of the structural pile construction holes 11 determined by the drawings. All precast temporary inverted arches of the same tunnel can be made with a set of templates.

[0055] In step 1, the width of the precast temporary inverted arch is calculated and determined according to the formation conditions, formation parameters, buried depth, and deformation control standards of the surrounding environment to determine the form of the precast temporary inverted arch. The form of the precast temporary inverted arch includes thickness, width, concrete strength, and reinforcement. The width is 0.5m - 1.5m, which is determined according to the tunnel span, the width of the precast temporary inverted arch, and the formation parameters.

[0056] Step 2, excavation of the upper soil body of the soft soil tunnel: Excavate a section of the tunnel, and the excavation footage is the same as the width of the precast unit plate 1. Use machinery to excavate in parts, and first excavate the upper soil body.

[0057] Step 3, erection of the primary support steel frame 21: Immediately after excavation, erect the primary support steel frame 21 in the tunnel. At the position of the invert connector 14 on the primary support steel frame 21, a steel frame connector 22 is preset.

[0058] Step 4, excavation of the lower soil mass and construction of the precast temporary invert: When excavating to the invert, ensure that the precast temporary invert is in full contact with the soft soil stratum. Then, level the invert site, and place the precast temporary invert at the designed position in the excavation section by mechanical hoisting. Then, fixedly connect and close the loop between the invert connector 14 and the steel frame connector 22.

[0059] Step 5, closure of the primary support structure: Spray the primary support concrete 23 to cover the primary support steel frame 21, the invert connector 14, and the steel frame connector 22, forming an operation cycle of the primary support structure. Quickly achieving the closure of the primary support into a loop can better control the formation deformation.

[0060] Step 6, construction of the in - tunnel rock - socketed structural pile 5: The length of the in - tunnel rock - socketed structural pile 5 is determined according to the depth of the bedrock, and the rock - socketed depth is greater than 3m. The construction machinery of the in - tunnel rock - socketed structural pile 5 is placed on the precast temporary invert, and the in - tunnel rock - socketed structural pile 5 is constructed on the surrounding rock. The top of the in - tunnel rock - socketed structural pile 5 penetrates through the structural pile construction hole 11. The in - tunnel rock - socketed structural piles 5 are completed one by one, and the in - tunnel rock - socketed structural pile 5 and the precast temporary invert are of a separated structure.

[0061] Step 7, construction of the waterproof layer 3: Construct the waterproof layer 3 on the inner contour of the primary support structure; the waterproof layer 3 between the in - tunnel rock - socketed structural pile 5 and the secondary lining structure 4 is constructed during the construction of the secondary lining.

[0062] Step 8, construction of the secondary lining structure 4: During the construction of the secondary lining structure 4, fixedly connect the top of the longitudinal reinforcement of the in - tunnel rock - socketed structural pile 5 with the main reinforcement of the secondary lining invert, forming a permanent stress - bearing structure.

[0063] Step 9, construct the next operation cycle, repeating Steps 2 to 3.

[0064] Step 10, level the invert site, place the precast unit plate 1 at the excavation section position, align the connection end 12 of the next precast unit plate 1 with the receiving end 13 of the previous precast unit plate 1, then connect them by mortise - and - tenon joints, and then fixedly connect and close the loop between the invert connector 14 and the steel frame connector 22; achieving longitudinal positioning through mortise - and - tenon joints can ensure the longitudinal stability of the tunnel, connect longitudinally into a whole, and better control the formation deformation.

[0065] Step 11, repeat Steps 5 to 8 to complete this operation cycle.

[0066] Step 12, repeat Steps 9 to 11 until the construction of the tunnel lining structure is completed.

Claims

1. A construction method for a tunnel lining structure, characterized in that: The tunnel lining structure comprises a primary support structure, a waterproof layer (3) and a secondary lining structure (4), wherein the primary support structure is formed by enclosing a prefabricated temporary inverted arch and other primary support structures, wherein the prefabricated temporary inverted arch comprises a reinforced concrete arch body, wherein the arch body is formed by longitudinally connecting prefabricated unit plates (1), wherein the cross section of the prefabricated unit plates (1) is arc-shaped, wherein the prefabricated unit plates (1) comprise structural pile construction holes (11) penetrating the plate body, wherein the structural pile construction holes (11) are arranged in a row along the longitudinal direction of the plate body, wherein the front end surface of the plate body is provided with a connecting end (12) arranged along the longitudinal direction of the plate body, wherein the rear end surface of the plate body is provided with a receiving end (13) arranged along the longitudinal direction of the plate body and adapted to the connecting end (12), wherein the receiving end (13) cooperates with the connecting end (12), and wherein the left and right end surfaces of the plate body are respectively centrally embedded with an inverted arch connecting piece (14); The primary support other structures (2) are primary support side walls and primary support vaults, including primary support steel frames (21), primary support concrete (23) and steel frame connectors (22). A steel frame connector (22) is pre-buried at the bottom end of the primary support steel frame (21); the left and right end faces of the prefabricated temporary invert are fixedly connected to the steel frame connector (22) via the invert connector (14), respectively; the primary support concrete (23) is sprayed to cover the primary support steel frame (21), and also covers the invert connector (14) and the steel frame connector (22); the prefabricated temporary invert and other primary support structures are enclosed to form a primary support structure; the waterproof layer (3) is integrally laid on the inner wall surface of the primary support structure; the secondary lining structure (4) is integrally constructed on the inner wall surface of the waterproof layer (3); The tunnel lining structure further comprises a reinforced concrete in-hole rock-embedded structural pile (5), the diameter of the in-hole rock-embedded structural pile (5) being smaller than the diameter of the structural pile construction hole (11), the number of the in-hole rock-embedded structural pile (5) being adapted to the number of the structural pile construction holes (11), the in-hole rock-embedded structural pile (5) vertically penetrating the structural pile construction hole (11) from bottom to top, the top of the in-hole rock-embedded structural pile (5) being fixedly connected to the secondary lining structure (4), and the bottom of the in-hole rock-embedded structural pile (5) being embedded in the tunnel surrounding rock; The secondary lining structure (4) is formed by enclosing a secondary lining inverted arch, a secondary lining side wall and a secondary lining arch top, the top of the longitudinal reinforcement of the in-hole rock-embedded structural pile (5) is fixedly connected to the main reinforcement of the secondary lining inverted arch, and there is no connection between the in-hole rock-embedded structural pile (5) and the prefabricated temporary inverted arch; The construction steps are as follows: Step 1, design and prefabrication of a prefabricated temporary invert: a template is made according to the tunnel initial support design drawing, and then a set of prefabricated unit plates (1) are made, the invert connector (14) is embedded in the prefabricated unit plates (1), and the position, size and arrangement of the structural pile construction holes (11) are determined according to the drawings for prefabrication; Step 2: excavation of the upper soil of the soft soil layer tunnel: excavation of a section of the tunnel, the excavation footage is consistent with the width of the prefabricated unit plate (1), and mechanical excavation is carried out in sections, first excavating the upper soil; Step 3, erection of the primary support steel frame (21): Immediately after excavation, erect the primary support steel frame (21) in the tunnel, and preset steel frame connectors (22) at the positions corresponding to the invert connectors (14) on the primary support steel frame (21); Step 4, excavation of the lower soil mass and construction of the precast temporary invert: When excavating to the invert, ensure that the precast temporary invert is in full contact with the soft soil stratum, then level the invert site, and place the precast temporary invert at the designed position in the excavation section by mechanical hoisting. Then, fixedly connect and close the loop between the invert connectors (14) and the steel frame connectors (22); Step 5, closure of the primary support structure: Spray the primary support concrete (23) to cover the primary support steel frame (21), the invert connectors (14), and the steel frame connectors (22) to form an operation cycle of the primary support structure; Step 6, construction of the in-tunnel rock-socketed structural piles (5): Place the construction machinery of the in-tunnel rock-socketed structural piles (5) on the precast temporary invert, and construct the in-tunnel rock-socketed structural piles (5) on the surrounding rock. The top of the in-tunnel rock-socketed structural piles (5) penetrates through the structural pile construction holes (11). The in-tunnel rock-socketed structural piles (5) are completed one by one, and the in-tunnel rock-socketed structural piles (5) and the precast temporary invert are of a separated structure; Step 7, construction of the waterproof layer (3): Construct the waterproof layer (3) on the inner contour of the primary support structure; the waterproof layer (3) between the in-tunnel rock-socketed structural piles (5) and the secondary lining structure (4) is constructed during the construction of the secondary lining; Step 8, construction of the secondary lining structure (4): During the construction of the secondary lining structure (4), fixedly connect the top of the longitudinal bars of the in-tunnel rock-socketed structural piles (5) with the main bars of the secondary lining invert to form a permanent stress-bearing structure; Step 9, construct the next operation cycle, and repeat Steps 2 to 3; Step 10, level the invert site, place the precast unit slab (1) at the excavation section position, align the connecting end (12) of the next precast unit slab (1) with the receiving end (13) of the previous precast unit slab (1), then connect them by mortise and tenon, and then fixedly connect and close the loop between the invert connectors (14) and the steel frame connectors (22); Step 11, repeat Steps 5 to 8 to complete this operation cycle; Step 12, repeat Steps 9 to 11 until the construction of the tunnel lining structure is completed.

2. The construction method of the tunnel lining structure according to claim 1, characterized in that: There are 1 - 2 rows of structural pile construction holes (11) on each precast unit slab (1), and 2 - 4 structural pile construction holes (11) are arranged in each row.

3. The construction method of the tunnel lining structure according to claim 1 or 2, characterized in that: Adjacent two precast unit slabs (1) are longitudinally connected by the cooperation of the receiving end (13) and the connecting end (12). A through-long convex rib is provided in the middle of the connecting end (12), and a through-long groove is provided in the middle of the receiving end (13). The convex rib and the groove are matched with each other.

4. The construction method of the tunnel lining structure according to claim 1, characterized in that: The cross-sectional arc-shaped inner contour of the precast temporary invert is adapted to the cross-sectional outer contour of the secondary lining invert. The primary support side wall is an arc-shaped structure, and both its cross-sectional inner and outer contours are adapted to the outer contour of the secondary lining side wall. The primary support arch top is an arc-shaped structure, and both its cross-sectional inner and outer contours are adapted to the outer contour of the secondary lining arch top.

5. The construction method of the tunnel lining structure according to claim 1 or 4, characterized in that: The invert connector (14) is a rectangular steel plate, and the steel frame connector (22) is a rectangular steel plate with the same size as the invert connector (14). A first bolt connection hole (7) is formed in the invert connector (14), and a second bolt connection hole (8) corresponding to the first bolt connection hole (7) is formed in the steel frame connector (22). The first bolt connection hole (7) and the second bolt connection hole (8) are aligned and fixedly connected by a connection bolt (6).

6. The construction method of the tunnel lining structure according to claim 5, characterized in that: The surface of the invert connector (14) is flush with the left and right end faces of the plate body, and the steel frame connector (22) is fixedly connected to the outer side of the surface of the primary support steel frame (21). The connection bolt (6) includes a screw rod (61) and nuts at both ends. The screw rod (61) sequentially passes through the first bolt connection hole (7) and the second bolt connection hole (8). The nuts at both ends include a first nut (62) embedded inside the precast temporary invert and closely attached to the back side of the invert connector (14), and also include a second nut (63) fastened to the outer side of the steel frame connector (22).

7. The construction method of the tunnel lining structure according to claim 1, characterized in that: In the first step, the width of the precast temporary invert is calculated and determined according to the formation conditions, formation parameters, burial depth, and surrounding environment deformation control standards to determine the form of the precast temporary invert. The form of the precast temporary invert includes thickness, width, concrete strength, and reinforcement. The width is 0.5 m to 1.5 m, which is determined according to the tunnel span, the width of the precast temporary invert, and the formation parameters. The length of the in - tunnel rock - socketed structural pile (5) is determined according to the bedrock depth, and the rock - socketed depth is greater than 3 m.

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