Auxiliary support device and construction method for tunnel invert construction

Abstract

The invention relates to the technical field of tunnel engineering, and in particular to an auxiliary support device and a construction method for tunnel invert construction; wherein the auxiliary support device comprises a first support structure, a second support structure of an inverted triangle structure and a third support structure, which work together to form an effective temporary reinforcement support system for the initial support structure of the tunnel and its surrounding rock, strengthen the pressure on the front end of the soft surrounding rock structure invert excavation area of ​​the soft surrounding rock structure to prevent the front and lateral soil body of the tunnel from sliding, and can effectively improve the support capacity of the initial support of the soft surrounding rock tunnel; combined with a three-step excavation method, the second step retains core soil to stabilize the heading, accelerates the settlement of the tunnel, and converges to a stable rate, can effectively solve the construction safety problem, achieve the purpose of rapid construction, and greatly reduce the construction cost.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to an auxiliary supporting device and a construction method for tunnel invert construction. Background Art

[0002] The commonly used construction method for highway tunnels is the New Austrian Tunneling Method (NATM), and its main operation sequence is: surrounding rock excavation, initial support, invert construction, secondary lining concrete injection, ancillary works, etc. Among them, "invert construction" is the key process of tunnel construction. Invert construction, in fact, the lower part of the annular steel arch frame of the initial support is connected to realize the overall closed loop of the steel arch frame, and then the concrete structure layer is poured on the closed steel arch frame to provide safety for the subsequent excavation of the tunnel.

[0003] During construction, after the cave is excavated for a certain distance (generally about 1m), an annular I-beam arch frame is immediately set on the exposed surface of the rock stratum in the cave, and cement concrete is sprayed to seal the exposed surface of the rock stratum to form an initial support structure to prevent the soil from falling off, lateral squeezing, and arch sinking and collapse on the exposed surface of the rock stratum (or the air-facing surface). At this time, the initial support structure is completed, indicating that only the upper half of the sphere on the cross-section of the tunnel structure has been constructed, and the lower half can only be continued after the surrounding rock is stable after the initial support structure is completed. During this period, the settlement (sinking amount of arch) and convergence (the rate at which the arch waists on the left and right sides move toward the air-facing surface) of the tunnel chamber must be continuously observed to determine the time node for the construction of the tunnel invert. Normally, after the initial support structure of the tunnel is completed, the settlement and convergence will gradually become stable over time until the design requirements are met before the invert construction can be carried out. However, when the geological conditions of the soft surrounding rock of the tunnel are very unstable, the settlement and convergence values ​​will fail to meet the design requirements, resulting in the excavation of the lower part and the invert construction being unable to proceed as planned, and the contradiction between construction safety and progress is prominent, which seriously affects the subsequent construction of the tunnel.

[0004] The initial support reinforcement measures commonly used in existing technologies are mainly the following two:

[0005] The first is the double-layer steel arch reinforcement measure: install a temporary steel arch under the existing steel arch to form a double-layer steel arch structural support system, and remove the lower temporary steel arch after the construction is completed; its disadvantages are that the construction is difficult and the construction period is long, and the construction of the lower temporary steel arch is carried out under the original steel arch, which will infringe on the tunnel clearance height, restrict the working surface, and make the subsequent construction operations difficult, and the construction operation is difficult and the construction period is long.

[0006] The second is the large pipe shed reinforcement measure: install a steel sleeve arch under the existing steel arch frame, and then drive a φ108mm seamless steel pipe along the circumference of the steel sleeve arch to obliquely pass through the initial support steel arch frame and inject cement mortar to form the initial support of the temporary large pipe shed reinforcement. After the back arch construction is completed, the large pipe shed sleeve arch will be removed; its disadvantage is that although it has a limiting effect on the sinking of the arch crown, the horizontal force effect is not good, and the tunnel convergence is difficult to meet the safety construction requirements. Summary of the invention

[0007] In order to solve the above problems, the present invention provides an auxiliary support device for tunnel invert construction which can effectively improve the supporting capacity of the initial support of a soft surrounding rock tunnel and has a simple structure.

[0008] The auxiliary support device of claim 1, wherein a plurality of structural steel arch frames are pre-arranged on the inner wall of the tunnel and an arch steel arch frame is connected to both ends of each of the structural steel arch frames. The auxiliary support device comprises a plurality of first support structures respectively connected to both ends of each of the structural steel arch frames and a plurality of second support structures respectively connected between the structural steel arch frames and the first support structure. The second support structure comprises a first support rod, a second support rod and a third support rod, wherein one end of the first support rod is fixedly connected to the top of the structural steel arch frame, one end of the second support rod and one end of the third support rod are respectively located on both sides of one end of the first support rod, the other end of the first support rod, the other end of the second support rod and the other end of the third support rod are all fixedly connected to the middle part of the first support structure, the second support rod and the third support rod are symmetrically distributed about the first support rod, and the auxiliary support device also comprises a plurality of third support structures fixedly connected between two adjacent first support structures.

[0009] The advantages and beneficial effects of the present invention are as follows: after the first supporting structure is connected to the structural steel arch frame of the initial support, the inverted arch steel arch frame erected in the later inverted arch construction can make the lower support of the structural steel arch frame used for the initial support more solid, preventing the two sides of the tunnel inner wall from sinking toward the middle, and an inverted triangle supporting structure formed by the first supporting rod, the second supporting rod and the third supporting rod enables the auxiliary supporting device to effectively support the upper part of the structural steel arch frame. At the same time, because the third supporting structure fixes and connects the adjacent first supporting structures together, the auxiliary supporting devices are connected to each other into a lattice structure, thereby improving the horizontal rigidity and overall stability of the auxiliary supporting device.

[0010] Preferably, the second support structure further comprises a plurality of transversely arranged fourth support rods, wherein the fourth support rods are respectively fixedly connected to the first support rod, the second support rod and the third support rod. In this way, the fourth support rods can make the inverted triangle structure formed by the first support rod, the second support rod and the third support rod more stable, thereby improving the overall stability of the entire auxiliary support device.

[0011] Preferably, the auxiliary support device further comprises a plurality of connecting rods fixedly connected between two adjacent fourth support rods, and the connecting rods are parallel and equidistant from each other. In this way, the connecting rods connected between two adjacent fourth support rods can increase the horizontal rigidity of the inverted triangle structure and improve the overall stability of the auxiliary support device.

[0012] Preferably, the first supporting structure is an arc-shaped I-beam frame, the opening direction of which is opposite to the opening direction of the structural steel arch frame, and the two ends of the I-beam frame are connected to the two ends of the structural steel arch frame by flange bolts. In this way, the arc-shaped I-beam frame can reduce the shear force applied to it by the structural steel arch frame, making the support more stable, and at the same time, the two ends of the arc are more compatible with the structural steel arch frame, so that the I-beam frame can be detachably connected to the structural steel arch frame by flange bolts, which facilitates the disassembly and installation of the entire I-beam frame and improves the efficiency of tunnel excavation.

[0013] A tunnel construction method, applied to the above device, comprises the following steps:

[0014] S1, a step excavation construction, erecting the structural steel arch frame on the inner wall of the tunnel and then spraying concrete;

[0015] S2, construction of the second step, leaving core soil on the second step, and spraying initial concrete support on the inner wall of the tunnel; S3, building the auxiliary support device on the second step;

[0016] S4, three-step construction, after completion, excavate the soil in the invert construction area and carry out invert construction;

[0017] S5. After removing the auxiliary supporting device, advance one working cycle forward.

[0018] The advantages and beneficial effects of the method of the present invention are as follows: in step S1, a structural steel arch frame is erected on the inner wall of the tunnel to support the entire tunnel, and concrete is sprayed on its side, which can achieve the effect of sealing the soil layer as soon as possible; in step S2, the reserved core soil can be used as a construction platform to stabilize the unexcavated face, and in case of landslide, the amount of landslide can be reduced; in step S3, an auxiliary support device is built to provide better support for the initial structural steel arch frame and improve the overall stability of the tunnel; in step S4, the inverted arch can solve the problem of insufficient foundation bearing capacity and prevent the uplift and deformation of the tunnel ground. At the same time, the inverted arch can seal the surrounding rock to prevent excessive deformation of the surrounding rock, improve the overall bearing capacity, increase the support resistance of the bottom and lateral soil bodies, and prevent shear failure caused by internal squeezing; In step S5, after completion, the auxiliary support device is removed, and the tunnel is advanced into the depth, and then the process from step S1 to step S4 is repeated until the tunnel construction is completed; the auxiliary support device can form a structural steel arch frame to effectively support the initial support of the tunnel, and at the same time, it can effectively temporarily reinforce the surrounding rock of the tunnel, and combined with the method of graded retention of core soil to stabilize the lower part of the geology of step S1 to step S4, strengthen the bearing pressure of the soft geology at the front end of the arch excavation area of ​​the soft surrounding rock structure to prevent the sliding of the unexcavated part of the tunnel and the lateral soil, which can effectively improve the supporting capacity of the initial support of the soft surrounding rock tunnel, and at the same time accelerate the rate of settlement and convergence to stability, which can effectively solve the construction safety problem and achieve the purpose of rapid construction.

[0019] Preferably, the invert construction area includes a first construction area and a second construction area, so that when the invert construction is being carried out in the first construction area, the second construction area is used for the ingress and egress of construction vehicles or mechanical equipment; or when the first construction area is used for the ingress and egress of construction vehicles or mechanical equipment, the second construction area is used for the invert construction. In this way, when the construction of one construction area is completed, the other construction area is excavated to carry out the invert construction at the lower part of the other construction area, thereby realizing the overall closed loop of the initial support steel arch frame.

[0020] Preferably, the second construction area excavates the tunnel interior at a small advance of every 2 meters, and after the excavation is in place, the inverted arch steel frame is erected in the second construction area, the inverted arch steel frame in the second construction area is connected to the inverted arch steel frame in the first construction area by flange bolts, and steel bars are arranged on both sides of the width direction of the inverted arch steel frame on the inner wall of the tunnel, and the steel bars arranged on both sides of the width direction of the inverted arch steel frame in the second construction area are welded to the steel bars arranged on both sides of the width direction of the inverted arch steel frame in the first construction area by electric welding, and concrete is poured after completion, and the process goes to step S5. In this way, when the first construction area is carrying out the inverted arch construction, the second construction area can carry out the ingress and egress of construction vehicles or mechanical equipment, and the equipment is parked in the second construction area to support the operation of the first construction area, which can make the working efficiency of the inverted arch construction more efficient than the inverted arch construction without partitions, and greatly shorten the construction period.

[0021] Preferably, before executing step S4, the I-beam frame is buried in a bottom-mounted manner, a groove is opened at the lower end of the I-beam frame, and concrete is poured in the groove. In this way, the lower end of the I-beam frame can improve the support firmness through the groove poured with concrete, thereby improving the support firmness of the entire auxiliary support structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a partial axonometric schematic diagram of the auxiliary support structure of the present invention;

[0023] Figure 2 A longitudinal cross-sectional view of a tunnel during construction using the construction method of the present invention;

[0024] Figure 3 is a flow chart of the construction method of the present invention;

[0025] Figure 4 It is a detailed flow chart of step S4 in the construction method of the present invention.

[0026] 1. Structural steel arch frame; 2. First supporting structure; 3. Second supporting structure; 4. Third supporting structure; 5. Locking foot anchor pipe; 6. First step; 7. Second step; 8. Third step; 9. Core soil; 10. Inverted arch construction area; 11. Trough; 301. First supporting rod; 302. Second supporting rod; 303. Third supporting rod; 304. Fourth supporting rod; 4A. Connecting rod; 1A. Inverted arch steel arch frame. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0028] In a preferred embodiment of the present invention, Figure 1 and attached Figure 2As shown, an auxiliary support device for tunnel invert construction, a plurality of structural steel arch frames 1 are pre-arranged on the inner wall of the tunnel and an invert steel arch frame 1A is connected to both ends of each structural steel arch frame 1, the connection method can be flange bolt connection, welding or riveting, and the preferred embodiment is flange bolt connection, the auxiliary support device includes a plurality of first support structures 2 respectively connected to both ends of each structural steel arch frame 1 and a plurality of second support structures 3 respectively connected between the structural steel arch frame 1 and the first support structure 2, the second support structure 3 includes a first support rod 301, a second support rod 302 and a third support rod 303, one end of the first support rod 301 is fixedly connected to the top of the structural steel arch frame 1, the fixed connection method can be welding, flange bolt connection or riveting, and the preferred embodiment is welding, one end of the second support rod 302 is fixedly connected to the top of the structural steel arch frame 1, the fixed connection method can be welding, flange bolt connection or riveting, and the preferred embodiment is welding, The second support rod 302 and the third support rod 303 are respectively located on both sides of one end of the first support rod 301, and the other end of the first support rod 301, the other end of the second support rod 302 and the other end of the third support rod 303 are all fixedly connected to the middle of the first support structure 2, and the fixed connection method can be welding, flange bolt connection or riveting. Welding is preferred in this embodiment. The second support rod 302 and the third support rod 303 are symmetrically distributed about the first support rod 301. The auxiliary support device also includes a plurality of third support structures 4 fixedly connected between two adjacent first support structures 2. The fixed connection method can be welding, flange bolt connection or riveting. Welding is preferred in this embodiment. The number of second support structures 3 is 6 groups, the number of first support structures 2 is 6, and the spacing between each first support structure 2 is 500mm.

[0029] A number of structural steel arch frames 1 are evenly spaced along the length direction of the tunnel inner wall. The structural steel arch frames 1 are close to the tunnel inner wall so that the axis formed by each structural steel arch frame coincides with the tunnel axis. An inverted arch steel arch frame 1A is connected to the lower end of each structural steel arch frame 1. The connection method is mostly fixed by flange bolt connection. After the first supporting structure 2 is connected to the structural steel arch frame 1 of the initial support, the inverted arch steel arch frame 1A erected in the later inverted arch construction can make the lower support of the structural steel arch frame 1 used for the initial support more firm. Combined with the inverted triangle support structure formed by the first support rod 301, the second support rod 302 and the third support rod 303, the auxiliary support device can effectively support the upper part of the structural steel arch frame 1. At the same time, because the third supporting structure 4 fixes the adjacent auxiliary support devices together, the auxiliary support devices are connected to each other into a lattice structure, which improves the horizontal stiffness and overall stability of the auxiliary support device.

[0030] In a preferred embodiment of the present invention, the second support structure 3 also includes a plurality of transversely arranged fourth support rods 304, and the fourth support rods 304 are respectively fixedly connected to the first support rod 301, the second support rod 302 and the third support rod 303. The fourth support rods 304 can make the inverted triangle structure formed by the first support rod 301, the second support rod 302 and the third support rod 303 more stable, thereby improving the overall stability of the entire auxiliary support device.

[0031] To further optimize the above scheme, the auxiliary support structure also includes a plurality of connecting rods 4A fixedly connected between two adjacent fourth support rods 304, and the connecting rods 4A are parallel and equidistant between each two adjacent fourth support rods 304. The connecting rods 4A connected between each two adjacent fourth support rods 304 can increase the horizontal stiffness of the inverted triangle structure and improve the overall stability of the auxiliary support device.

[0032] The first support rod 301, the second support rod 302 and the third support rod 303 are made of I20 I-beams, while the fourth support rod 304 and the connecting rod 4A are both made of 14 channel steel, wherein the preferred number of the fourth support rods 304 is 6, and the preferred number of the connecting rods 4A is 5 groups with 3 in each group; the third support structure 4 is made of I-beams.

[0033] In a preferred embodiment of the present invention, at least one locking foot anchor pipe 5 is provided on the inner wall of the tunnel near the end of each structural steel arch frame 1. The locking foot anchor pipe 5 extends into the side wall of the tunnel at an angle of 45°. The locking foot anchor pipe 5 can limit the displacement of the structural steel arch frame 1 and its soil, so that it can bear the pressure caused by the deformation of the surrounding rock earlier. The locking foot anchor pipe 5 is set at a downward angle of 45°. The locking foot anchor pipe 5 in this embodiment adopts a φ80mm seamless steel pipe. In this embodiment, a locking foot anchor pipe 5 is provided on both sides of the inner wall of the tunnel near the end of each structural steel arch frame 1, so that the best force effect can be achieved.

[0034] The connecting steel plates on both sides of the lower part of the initial support structural steel arch frame 1 are pierced and the locking foot anchor pipe 5 is inserted into the deep of the surrounding rock to prevent lateral soil displacement and vertical sliding of the initial support structural steel arch frame 11.

[0035] To further optimize the above solution, the locking foot anchor pipe 5 is poured with cement mortar, which is a mixture of cement and water glass. The cement mortar mixed with cement and water glass has quick-setting and anti-seepage effects. In this embodiment, the ratio of cement to water glass is 1:1.

[0036] In a preferred embodiment of the present invention, the first supporting structure 2 is an arc-shaped I-beam frame, the opening direction of which is opposite to the opening direction of the structural steel arch frame 1, and the two ends of the I-beam frame are connected to the two ends of the lower part of the structural steel arch frame 1 by flange bolts; specifically, the arc-shaped I-beam frame can reduce the shear force applied to it by the structural steel arch frame 1, making the support more stable, and at the same time, the two ends of the arc are more adapted to the structural steel arch frame 1, so that the I-beam frame can be detachably connected to the structural steel arch frame 1 by flange bolts, which facilitates the disassembly and installation of the entire I-beam frame and improves the efficiency of tunnel excavation. The I-beam frame is an I18 I-beam.

[0037] Specifically, the preferred second support structure 3 of this embodiment is connected to the first support structure 2 through the third support structure 4, which can facilitate the installation of the first support rod 301, the second support rod 302 and the third support rod 303. At the same time, the side of the I-beam has strong hardness, so its bending resistance is particularly strong and it is not easy to bend. It also has smaller residual stress and higher precision. The I-beams are evenly spaced and installed on the first support structure 2, which can improve the horizontal stiffness between the first support structures 2.

[0038] Specifically, the auxiliary support device is a support structure system for temporary reinforcement of the initial support structure of the tunnel. Combined with the three-step 8 excavation method in the longitudinal direction of the tunnel, the core soil 9 is retained in stages to stabilize the geology of the lower part, which accelerates the rate of settlement and convergence to stability, can effectively solve the construction safety problem and achieve the purpose of rapid construction.

[0039] The support structure system consists of an arc-shaped I-beam arch frame, a second support structure 3 of a vertical inverted triangle structure, and locking foot anchor pipes 5 that are symmetrically inserted into the rock layer on both sides of the arch waist. The three work together to form an effective temporary reinforcement support system for the structural steel arch frame 1 and surrounding rock for initial support of the tunnel. Combined with the three-step 8 excavation method, the pressure on the soft geology at the front end of the arch excavation area of ​​the soft surrounding rock structure is strengthened to prevent the front and lateral soil of the tunnel from sliding. This method has a simple structure, is easy to operate, reduces costs, and can effectively improve the supporting capacity of the initial support of the soft surrounding rock tunnel.

[0040] Compared with the double-layer steel arch frame reinforcement measures in the prior art, the support structure system of this application is simpler to operate and has less difficulty in construction work, so the construction period is short and the cost is reduced by more than 30%; compared with the large pipe shed reinforcement measures, the support structure system of this application not only limits the sinking of the arch, but also has good horizontal force effect, which is easy to meet the safety construction requirements and reduces the cost by more than 50%.

[0041] In order to shorten the construction period and speed up the progress of tunnel excavation, liftable support columns are respectively provided at the lower ends of both sides of each I-beam frame. The auxiliary support device also includes a moving device arranged at the lower end of the support column. The moving device can make rollers. A guide rail arranged along the length direction of the tunnel is provided on the ground below the support column. The support column makes the entire auxiliary support device movable through the cooperation of the rollers and the guide rails. A flippable fixing device is also provided on both sides of the support column along the length direction of the tunnel. When the support column needs to stop moving, the fixing device is driven to flip and fall to the ground, so that the roller is off the ground, so that the entire auxiliary support device is fixed, and the support column is driven to rise at the same time, so that the second support structure 3 touches the structural steel arch frame 1, and the second support structure 3 is welded to the structural steel arch frame 1. If the auxiliary support device needs to be moved, just cut the second support structure 3 to separate the structural steel arch frame 1 from the second support structure 3, and remove the flange bolts on both sides of the I-beam frame at the same time. Drive the support column to descend at the same time, and the entire auxiliary support device can be driven to move.

[0042] Combined with Figure 3 and attached Figure 4 As shown, a tunnel construction method, applied to the above device, comprises the following steps:

[0043] S1, excavation of the first step 6, erection of structural steel arch frame 1 on the inner wall of the tunnel and initial spraying of concrete;

[0044] S2, construction of the second step 7, leaving core soil 9 on the second step 7, and spraying concrete initial support on the inner wall of the tunnel;

[0045] S3, building an auxiliary support device on the second step 7;

[0046] S4, the third step 8 is constructed, after which soil is excavated in the invert construction area 10 to carry out invert construction;

[0047] S5. After removing the auxiliary support device, advance one working cycle forward.

[0048] In step S1, a structural steel arch frame 1 is erected on the inner wall of the tunnel to support the entire tunnel, and concrete is sprayed on its side to achieve the effect of sealing the soil layer as soon as possible; in step S2, the reserved core soil 9 can be used as a construction platform to stabilize the unexcavated face, and in case of landslide, the amount of landslide can be reduced; in step S3, an auxiliary support device is built to provide better support for the initial structural steel arch frame 1 and improve the overall stability of the tunnel; in step S4, the inverted arch can solve the problem of insufficient foundation bearing capacity and prevent the uplift and deformation of the tunnel ground. At the same time, the inverted arch can seal the surrounding rock to prevent excessive deformation of the surrounding rock, improve the overall bearing capacity, increase the support resistance of the bottom and lateral soil bodies, and prevent shear failure caused by internal squeezing; in step S5, the end After completion, the auxiliary support device is removed, and the tunnel is advanced into the depth, and then the process from step S1 to step S4 is repeated until the tunnel construction is completed; the auxiliary support device can form an effective support for the structural steel arch frame 1 of the initial support of the tunnel, and at the same time, it can effectively temporarily reinforce the surrounding rock of the tunnel, and combined with the method of grading the core soil 9 to stabilize the lower part of the geology of step S1 to step S4, strengthen the bearing pressure of the soft geology at the front end of the arch excavation area of ​​the soft surrounding rock structure to prevent the sliding of the unexcavated part of the tunnel and the lateral soil body, which can effectively improve the supporting capacity of the initial support of the soft surrounding rock tunnel, and at the same time accelerate the rate of settlement and convergence to stability, which can effectively solve the construction safety problem and achieve the purpose of rapid construction.

[0049] To further optimize the above scheme, the invert construction area 10 includes a first construction area and a second construction area, so that when the invert construction is being carried out in the first construction area, the second construction area is used for the entry and exit of construction vehicles or mechanical equipment; or when the first construction area is used for the entry and exit of construction vehicles or mechanical equipment, the second construction area is used for the invert construction. After the construction of one of the construction areas is completed, the other construction area is excavated to carry out the invert construction at the lower part of the other construction area, thereby realizing the overall closed loop of the initial support steel arch frame.

[0050] To further optimize the above scheme, the second construction area excavates the tunnel interior at a small advance of every 2 meters. After the excavation is in place, the inverted arch steel arch frame 1A is erected in the second construction area. The inverted arch steel arch frame 1A in the second construction area is connected to the inverted arch steel arch frame 1A in the first construction area by flange bolts, and steel bars are arranged on both sides of the width direction of the inverted arch steel arch frame 1A on the inner wall of the tunnel. The steel bars arranged on both sides of the width direction of the inverted arch steel arch frame 1A in the second construction area are welded to the steel bars arranged on both sides of the width direction of the inverted arch steel arch frame 1A in the first construction area by electric welding. After completion, concrete is poured and the process goes to step S5. When the first construction area is carrying out the inverted arch construction, the second construction area can carry out the entry and exit of construction vehicles or mechanical equipment, and the equipment is parked in the second construction area to support the operation of the first construction area, which can make the working efficiency of the inverted arch construction more efficient than the inverted arch construction without partitions, and greatly shorten the construction period.

[0051] The preferred step S4 may also be: A41, three steps 8 are constructed, after which the second construction area excavates the tunnel interior at a small advance of every 2 meters, after which the inverted arch steel frame 1A is erected in the second construction area, the inverted arch steel frame 1A in the second construction area is connected to the inverted arch steel frame 1A in the first construction area by flange bolts, and steel bars are arranged on both sides of the width direction of the inverted arch steel frame 1A on the inner wall of the tunnel, the steel bars arranged on both sides of the width direction of the inverted arch steel frame 1A in the second construction area are welded to the steel bars arranged on both sides of the width direction of the inverted arch steel frame 1A in the first construction area by electric welding, and after completion, pouring Concrete; A42, the first construction area excavates the tunnel interior at a small advance of every 2 meters. After the excavation is in place, an inverted arch steel arch frame 1A is erected in the first construction area, and steel bars are arranged on both sides of the tunnel inner wall along the width direction of the inverted arch steel arch frame 1A. After completion, concrete is poured and the process goes to step S5. When the second construction area is carrying out the inverted arch construction, the first construction area can allow construction vehicles or mechanical equipment to enter and exit, and the equipment is parked in the first construction area to support the operation of the second construction area, which can make the work efficiency of the inverted arch construction more efficient than the non-zoned inverted arch construction, and greatly shorten the construction period.

[0052] Preferably, before executing step S4, the I-beam frame is buried downwardly, a groove is opened at the lower end of the I-beam frame, and concrete is poured in the groove. The lower end of the I-beam frame can improve the support firmness by pouring concrete in the groove, thereby improving the support firmness of the entire auxiliary support structure.

[0053] Specifically, the embodiment adopts a three-step construction method and reserves core soil 9 on the second step 7. First, the first step 6 is excavated and constructed, a steel arch frame is erected, and initial concrete is sprayed. Then, the second step 7 is constructed, and the core soil 9 is reserved. Since the depth of a single tunnel excavation is only 2 to 4 meters, the support of the face can be completed by relying on the core soil 9 of the second step 7. Moreover, since the core soil 9 is only reserved on the second step 7, the construction period can be greatly shortened compared to the practice of reserving core soil 9 on all three steps, and the progress of tunnel excavation can be accelerated. After the construction of the second step 7 is completed, an auxiliary support device needs to be installed at the second step 7. After completion, a groove 11 needs to be dug at the lower end of the I-beam frame, and the groove 11 is dug 25 to 30 cm below the ground, and a 40 cm wide × 20 cm thick C30 plain concrete cushion layer is poured, even if the entire I-beam frame is buried in a bottom-mounted manner, so as to improve the support strength of the I-beam frame and the support strength of the overall auxiliary support device. During construction, it is also necessary to strengthen monitoring and measurement, and timely observe the changes in the surrounding rock. That is, the construction of the longitudinal excavation retaining core soil 9 and the construction of the structural steel arch frame 1 for initial support and the auxiliary support device for the invert arch are carried out in sequence. Each excavation section is supported at the same time, and the construction of the auxiliary support device for the invert arch follows closely.

[0054] When the surrounding rock convergence and the tunnel vault sinking meet the construction requirements, the invert construction can be carried out; the invert construction is located in the lower half of the tunnel cave. First, the auxiliary support device is removed on the outer side of the lower half of the tunnel cave to carry out the surrounding rock excavation; in order to facilitate the passage of construction vehicles and mechanical equipment, the soil excavation is divided into two construction areas on the left and right in the cross section, namely the first construction area and the second construction area. First, the lower half of the soil in the first construction area is excavated until the invert position, and a small advance is made every 2 meters in the longitudinal direction. After the excavation is in place, the invert steel arch frame 1A is erected in time, the steel bars are laid and the concrete is poured; when the construction of the first construction area is completed, the second construction area is excavated, and the invert construction of the lower half of the other half is carried out, so as to realize the overall closed loop of the structural steel arch frame 1 of the initial support, and then the next cycle of invert construction is carried out.

[0055] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A tunnel construction method, using an auxiliary support device, pre-arranging a plurality of structural steel arch frames (1) on the inner wall of the tunnel and connecting an inverted arch steel arch frame (1A) at both ends of each structural steel arch frame (1), characterized in that: The auxiliary support device comprises a plurality of first support structures (2) respectively connected to both ends of each of the structural steel arch frames (1) and a plurality of second support structures (3) respectively connected between the structural steel arch frames (1) and the first support structures (2), the second support structures (3) comprising a first support rod (301), a second support rod (302) and a third support rod (303), one end of the first support rod (301) being fixedly connected to the top of the structural steel arch frame (1), one end of the second support rod (302) and one end of the third support rod (303) being respectively connected to the structural steel arch frame (1) and being located on both sides of one end of the first support rod (301), 01), the other end of the second support rod (302) and the other end of the third support rod (303) are all fixedly connected to the middle part of the first support structure (2), the second support rod (302) and the third support rod (303) are symmetrically distributed with respect to the first support rod (301), the auxiliary support device also includes a plurality of third support structures (4) fixedly connected between two adjacent first support structures (2), the second support structure (3) also includes a plurality of transversely arranged fourth support rods (304), the fourth support rods (304) are respectively fixedly connected to the first support rod (301), the second support rod (302) and the third support rod (303); The following construction steps are also included: S1, excavation of a step (6), erecting the structural steel arch frame (1) on the inner wall of the tunnel and then spraying concrete; S2, construction of the second step (7), leaving core soil (9) on the second step (7), and spraying initial concrete support on the inner wall of the tunnel; S3, constructing the auxiliary support device on the second step (7); S4, the three steps (8) are constructed, and after completion, the soil is excavated in the invert construction area (10) to carry out invert construction; S5. After removing the auxiliary supporting device, advance one working cycle forward.

2. The tunnel construction method according to claim 1, characterized in that: The invert construction area (10) comprises a first construction area and a second construction area, so that when the invert construction is being carried out in the first construction area, the second construction area is used for the entry and exit of mechanical equipment; or when the first construction area is used for the entry and exit of mechanical equipment, the second construction area is used for the invert construction.

3. The tunnel construction method according to claim 2, characterized in that: The step S4 comprises: S41, three steps (8) are constructed. After completion, the first construction area is excavated into the tunnel at a small advance of every 2 meters. After the excavation is completed, the inverted arch steel frame (1A) is erected in the first construction area, and steel bars are laid on both sides of the inverted arch steel frame (1A) along the width direction of the tunnel inner wall. After completion, concrete is poured; S42, excavating the tunnel interior at a small advance of every 2 meters in the second construction area, and after the excavation is in place, erecting the inverted arch steel frame (1A) in the second construction area, connecting the inverted arch steel frame (1A) in the second construction area with the inverted arch steel frame (1A) in the first construction area by flange bolts, and laying steel bars on both sides of the width direction of the inverted arch steel frame (1A) on the inner wall of the tunnel, welding the steel bars laid on both sides of the width direction of the inverted arch steel frame (1A) in the second construction area with the steel bars laid on both sides of the width direction of the inverted arch steel frame (1A) in the first construction area by electric welding, and after completion, pouring concrete, and entering step S5.

4. The tunnel construction method according to claim 1, characterized in that: Before executing step S4, the I-beam frame is buried in a bottom-up manner, a groove (11) is opened at the lower end of the I-beam frame, and concrete is poured in the groove (11).

5. The tunnel construction method according to claim 1, characterized in that: The auxiliary support device also includes a plurality of connecting rods (4A) fixedly connected between two adjacent fourth support rods (304), and two adjacent connecting rods (4A) are parallel and equidistant from each other.

6. The tunnel construction method according to claim 1, characterized in that: The first supporting structure (2) is an arc-shaped I-beam frame, the opening direction of which is opposite to the opening direction of the structural steel arch frame (1), and the two ends of the I-beam frame are connected to the two ends of the structural steel arch frame (1) by flange bolts.

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