A construction method of up-and-down stacked interchange tunnel based on advanced pre-reinforcement

Abstract

The application discloses a construction method of up-and-down stacked interchange tunnel based on advanced pre-reinforcement, which comprises the following steps: S1, constructing a lower section tunnel of the stacked interchange section and simultaneously carrying out grouting reinforcement on the lower section tunnel; S2, carrying out secondary deep hole grouting reinforcement on the soil at the top of the lower section tunnel to form a secondary deep hole grouting reinforced area; S3, carrying out advanced pre-grouting reinforcement on the soil at the bottom of the upper section tunnel of the stacked interchange section in a shield machine to form an advanced pre-reinforced area of the shield machine; S4, erecting a telescopic support assembly in the lower section tunnel to reinforce the lower section tunnel; and S5, constructing the upper section tunnel of the stacked interchange section and simultaneously carrying out synchronous grouting reinforcement and secondary grouting reinforcement on the upper section tunnel. The reinforcement structure of the stacked interchange tunnel can effectively control the deformation of the upper and lower section tunnels and the ground surface settlement through the secondary deep hole grouting reinforcement of the lower section tunnel and the advanced pre-reinforcement of the upper section tunnel in the shield machine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shield construction, in particular to a construction method of up-down stacked intersection tunnel based on advanced pre-reinforcement. BACKGROUND

[0002] With the development of modern urban rail transit, China has entered an era of large-scale development of underground space. In recent years, due to the increase in the depth and density of underground space development, and the shortage of urban land resources, the situation of up-down stacked intersection construction between two or more shield tunnels has gradually emerged, and has a tendency to become more and more serious. Under this engineering background, many new problems need to be solved.

[0003] Most of the problems of shield tunnel stacking are double-line parallel stacking or multi-line cross stacking. In the stacked tunnel, according to the principle of optimizing the construction sequence under the most unfavorable engineering conditions, the construction site finally selects the construction sequence of first downhole and then uphole in the overlapping tunnel section. The stacked tunnel belongs to a small near-distance self-approaching project. When the up-down line is stacked and constructed, it will have a significant impact on each other, and there is a great construction risk. Therefore, how to effectively control the mutual influence of the up-down tunnel construction is the key and difficulty of the stacked tunnel construction.

[0004] In order to reduce the impact on the surrounding buildings, shield tunnel construction often uses the method of ground pre-reinforcement for soil pre-reinforcement. When the stacked tunnel is constructed, the methods of synchronous grouting and secondary grouting are often used to reinforce the soil. The advanced pre-grouting reinforcement in the shield machine uses the grouting hole of the shield machine itself to reinforce the soil in front of the cutter head, which can effectively control the mutual influence caused by the construction of the up-down tunnel. Due to the possible existence of buildings or lakes, wetlands and other environmental conditions above the stacked tunnel, ground pre-reinforcement is not possible, so advanced pre-reinforcement in the shield machine is necessary. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art, and to provide a construction method of up-down stacked intersection tunnel based on advanced pre-reinforcement.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] A construction method of up-down stacked intersection tunnel based on advanced pre-reinforcement, the construction method comprising the following steps:

[0008] S1: constructing the lower section tunnel of the stacked section, and performing synchronous grouting reinforcement on the lower section tunnel;

[0009] S2: performing secondary deep hole grouting reinforcement on the soil at the top of the lower section tunnel to form a secondary deep hole grouting reinforcement area;

[0010] S3: Tunnel bottom soil of upper section of the overlapping section is reinforced by advanced pre-grouting inside the shield machine to form advanced pre-reinforced area of the shield machine;

[0011] S4: A telescopic support assembly is erected in the lower section tunnel for reinforcement;

[0012] S5: The upper section tunnel of the overlapping section is constructed, and the upper section tunnel is simultaneously grouted and secondarily grouted.

[0013] Preferably, the secondary deep hole grouting in S2 adopts in-hole deep hole grouting, the reinforcement range is 180° at the top, and the reinforcement depth is 3m; the advanced pre-grouting inside the shield machine in S3 adopts advanced pre-grouting inside the shield machine, the reinforcement range is 180° at the bottom, and the reinforcement depth is 2m.

[0014] Preferably, the secondary deep hole grouting in S2 is performed by grouting through the grouting pipe matched with the hoisting hole reserved on the segment of the lower section tunnel, the grouting slurry adopts cement-silicate double slurry, the silicate is diluted with water at a ratio of 1:3, the cement:water = 1:1, the silicate:cement slurry = 1:1, and the grouting amount is ≥25m 3 / ring.

[0015] Preferably, the advanced pre-grouting inside the shield machine in S3 is performed by grouting through the drilling machine matched with the advanced pre-grouting hole reserved inside the shield machine, the hole diameter is 100mm, the shield machine includes a front shield, a cutter head, a middle shield, a shield tail and a grouting platform, the soil layer below the front end of the cutter head is reinforced by the advanced grouting hole, the grouting is performed by the segmented retreat type, the grouting slurry adopts ultra-fine cement-silicate double slurry, the volume ratio is 1:1, the ultra-fine cement adopts the type MC-800, the water-cement ratio of the ultra-fine cement slurry is 1:1, the Baume degree of the silicate is 38°Bé, the retarder adopts sodium dihydrogen phosphate, the dosage is 1% of the mass of the ultra-fine cement, the phosphoric acid mixed solution is used to stop water during the drilling process, the volume ratio of the phosphoric acid solution to the silicate solution is 1:1, the silicate solution is diluted with water at a ratio of 1:1 to form a silicate solution, the phosphoric acid solution is mixed with water at a ratio of 1:10 to form a phosphoric acid solution.

[0016] Preferably, the drilling and grouting equipment of the segmented retreat type grouting adopts a drill rod with a diameter of 42mm, a ball-tooth shaped drill bit is installed in front of the drill rod, the single joint drill rod is 2m long, the drill rods are connected by threads, the rotation direction of the threads is opposite to the rotation direction of the drilling, the drill rod has a grouting channel, a flange is used to connect and fix the hole orifice of the shield machine, and the grouting process uses a grouting plug and a blowout preventer to prevent slurry leakage.

[0017] Preferably, the segmented back-off grouting adopts the principle of hole drilling, the annular spacing between the holes is 1.2m, a total of 8 grouting holes, the grout diffusion radius is 0.8m, the same reserved hole is grouted at different angles, the first grouting angle is 13°, the second grouting angle is 6°, the drill pipe node is recorded in detail to ensure that the drill hole reaches the specified depth, and the grouting range is 6m (about 4 annular segments) at the front end of the cutter head each time, the reinforcement is carried out once every 4 annular segments, and the single-hole grouting amount is 4.6m 3 ;

[0018] After the drilling is completed, the hole is first sealed, an appropriate amount of phosphoric acid mixed solution is injected to stop water, and then ultra-fine cement-silicate double liquid slurry is injected, when the grouting pressure reaches, the drill pipe is retracted, the drill pipe is retracted by 0.5m each time, the next section grouting is carried out, and the cycle is repeated until the hole grouting is completed.

[0019] Preferably, the telescopic support assembly supports the lower section tunnel and extends forward with the upper section tunnel 1.

[0020] Preferably, the telescopic support assembly comprises vertically arranged and horizontally arranged hydraulic oil cylinders, one end of the hydraulic oil cylinder is connected with one end of the telescopic hydraulic rod, the other end of the vertically arranged telescopic hydraulic rod is connected with a vertical circular steel pipe, the other end of the transversely arranged telescopic hydraulic rod is connected with a transverse circular steel pipe, the side wall of the vertical circular steel pipe is connected with a detachable square steel pipe, the transverse circular steel pipe penetrates the detachable square steel pipe, the end portions of the hydraulic oil cylinder, the vertical circular steel pipe and the transverse circular steel pipe are connected with arc-shaped steel plates, and the arc-shaped steel plates have the same curvature as the inner diameter of the tunnel segment.

[0021] Preferably, the two arc-shaped steel plates are connected through a channel steel along the tunnel excavation direction, the channel steel is connected with the arc-shaped steel plates through bolts, and the length of the arc-shaped steel plate in the vertical direction is greater than the length of the arc-shaped steel plate in the horizontal direction.

[0022] Preferably, the arc-shaped steel plates are welded with stiffening ribs at the connection positions with the vertical circular steel pipe and the transverse circular steel pipe, and the stiffening ribs are distributed at equal angles among the plurality of stiffening ribs.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The reinforcement structure of the superimposed tunnel can effectively control the deformation and ground settlement of the upper and lower section tunnels through the secondary deep hole grouting reinforcement of the lower section tunnel, the advanced pre-reinforcement in the shield tunneling machine, and the measures of setting temporary arc-shaped steel plates + telescopic pre-axial force steel pipe supports in the lower section tunnel, which plays a good reinforcement role and reduces the excavation risk.

[0025] (2) The invention adopts the advance pre-reinforcement in the shield machine, aiming at the soft stratum with buildings on the ground or poor geological conditions, the superimposed tunnel which cannot be pre-reinforced on the ground or reinforced outside the tunnel, uses the ultra-fine cement-sodium silicate double slurry for grouting, compared with the traditional cement slurry with 0.5-0.6 m diffusion radius, the injectability is better, the diffusion radius can reach 0.8-1.0 m, the full hydration reaction of ultra-fine cement enhances the strength of the reinforced body, compared with the ordinary cement slurry, the strength is enhanced by nearly one time, and the influence on the lower tunnel during the upper tunnel excavation can be well controlled;

[0026] (3) The invention adopts the temporary arc-shaped steel plate + telescopic pre-axial force steel pipe support, which is convenient to stretch and retract, can synchronously support the lower interval tunnel during the upper interval tunnel excavation, can be retracted in the excavation direction and then erected and stretched forward, the hydraulic cylinder is used to pre-axially force the steel pipe, the bearing capacity is increased, the mutual influence during the tunnel excavation is reduced, and the tunnel deformation is effectively controlled. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more specifically and intuitively illustrate the technical solutions in the embodiments of the application or the prior art, a brief introduction will be given to the drawings needed to be used in the embodiments or the prior art description.

[0028] Figure 1 It is a construction process schematic diagram of the invention;

[0029] Figure 2 It is a reinforcement cross-sectional view of the superimposed section of the invention;

[0030] Figure 3 It is a pre-grouting reinforcement process diagram in the shield machine of the invention;

[0031] Figure 4 It is a pre-grouting reinforcement schematic diagram in the shield machine of the invention;

[0032] Figure 5 It is a temporary arc-shaped steel plate + telescopic pre-axial force steel pipe support schematic diagram of the invention.

[0033] In the drawings: the upper interval tunnel 1, the lower interval tunnel 2, the shield machine advance pre-reinforcement area 3, the secondary deep hole grouting reinforcement area 4, the front shield 5, the cutter head 6, the middle shield 7, the shield tail 8, the grouting platform 9, the drill rod 10, the unexcavated reinforcement area 11, the excavated reinforcement area 12, the stiffening rib 13, the arc-shaped steel plate 14, the vertical circular steel pipe 15, the telescopic hydraulic rod 16, the hydraulic cylinder 17, the channel steel 18, the detachable square steel pipe 19, and the horizontal circular steel pipe 20. DETAILED DESCRIPTION

[0034] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application.

[0035] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Figures 1-5 A tunnel construction method based on advanced pre-reinforcement, the construction method comprising the following steps:

[0036] S1: constructing the lower section tunnel 2 of the overlap section and simultaneously grouting and reinforcing the lower section tunnel 2;

[0037] S2: performing secondary deep hole grouting and reinforcing on the soil at the top of the lower section tunnel 2 to form a secondary deep hole grouting and reinforcing area 4;

[0038] S3: performing advanced pre-grouting and reinforcing in the shield machine on the soil at the bottom of the upper section tunnel 1 of the overlap section to form a shield machine advanced pre-reinforcement area 3;

[0039] S4: erecting a telescopic support assembly in the lower section tunnel 2 for reinforcement;

[0040] S5: constructing the upper section tunnel 1 of the overlap section and simultaneously grouting and reinforcing and performing secondary grouting and reinforcing on the upper section tunnel 1.

[0041] In the present embodiment, the secondary deep hole grouting and reinforcing in S2 adopts in-hole deep hole grouting and reinforcing, the reinforcing range is 180° at the top, and the reinforcing depth is 3m. The advanced pre-grouting and reinforcing in the shield machine in S3 adopts advanced pre-grouting and reinforcing in the shield machine, the reinforcing range is 180° at the bottom, and the reinforcing depth is 2m.

[0042] Secondary deep hole grouting and reinforcing:

[0043] 1. Requirements for grouting slurry

[0044] The grouting slurry adopts a cement-silicate mixture, the silicate is diluted with water at a ratio of 1:3, the cement:water ratio is 1:1, and the silicate:cement slurry ratio is 1:1.

[0045] The grouting amount is calculated according to the following formula:

[0046] Q=Anα(1+β)

[0047] Q is the deep hole grouting amount of one ring;

[0048] A is the volume of the soil in the grouting range;

[0049] n is the soil porosity, which is 0.4;

[0050] α is the grouting filling coefficient, which is 0.8;

[0051] β—Slurry loss coefficient, taken as 0.2.

[0052] The calculated grouting volume is ≥25m. 3 / ring.

[0053] 2. Grouting range

[0054] like Figure 2 As shown, the secondary deep hole grouting reinforcement range is within 180° of the top of the lower section entrance tunnel, and the reinforcement depth is 3m.

[0055] 3. Grouting Management

[0056] (1) Before grouting, the outer protective layer of the segment hoisting hole is pierced, the pipeline is connected, and grouting is carried out;

[0057] (2) Start injecting cement-water glass double liquid grouting 5 rings after the segment detaches from the shield tail, and complete the injection within 7 rings after the segment detaches from the shield tail.

[0058] (3) The grouting pressure shall be strictly controlled between 0.3 and 0.5 MPa;

[0059] (4) When injecting double grout, first inject pure cement grout for 1 minute, then open the water glass valve to mix and inject. When the hole is closed, the concentration of water glass should be increased.

[0060] (5) After grouting is completed, flush the mixing valve and connecting valve in time so that the next grouting can be carried out smoothly. After the second grouting is completed, seal each grouting hole to prevent water seepage.

[0061] In this implementation plan, the secondary deep-hole grouting reinforcement in S2 is carried out by grouting through the pre-reserved hoisting holes on the tunnel segments in the lower section 1, in conjunction with the grouting pipes. The grouting slurry is a cement-water glass dual-slurry, with water glass diluted with water at a ratio of 1:3, cement:water = 1:1, and water glass:cement slurry = 1:1. The grouting volume is ≥25m³. 3 / ring.

[0062] In this embodiment, the advance pre-grouting reinforcement in the shield machine in S3 utilizes the advance pre-grouting hole reserved in the shield machine to cooperate with the drilling machine to perform grouting reinforcement, the hole diameter is 100 mm, the shield machine comprises a front shield 5, a cutter head 6, a middle shield 7, a shield tail 8 and a grouting platform 9, the advance grouting hole is utilized to reinforce the soil layer below the front end of the cutter head 6, the sectional retreat type grouting is adopted, the super-fine cement-sodium silicate double grout is adopted as the grouting slurry, the volume ratio is 1:1, the super-fine cement of type MC-800 is adopted as the super-fine cement, the water-cement ratio of the super-fine cement slurry is 1:1, the Baume degree of the sodium silicate is 38°Bé, the sodium dihydrogen phosphate is adopted as the retarder, the mixing amount is 1% of the mass of the super-fine cement, the phosphoric acid mixed solution is adopted as the water stop during the drilling process, the volume ratio of the phosphoric acid solution to the sodium silicate solution is 1:1, the sodium silicate of 40°Bé is diluted with water in a volume ratio of 1:1 to form the sodium silicate solution, the phosphoric acid is mixed with water in a ratio of 1:10 to form the phosphoric acid solution.

[0063] Advance pre-grouting reinforcement in the shield machine:

[0064] 1. Requirements for the grouting slurry

[0065] The super-fine cement-sodium silicate double grout is adopted as the grouting slurry, the volume ratio is 1:1, the super-fine cement of type MC-800 is adopted as the super-fine cement, the water-cement ratio of the super-fine cement slurry is 1:1, the Baume degree of the sodium silicate is 38°Bé, the sodium dihydrogen phosphate is adopted as the retarder, the mixing amount is 1% of the mass of the super-fine cement, the phosphoric acid mixed solution is adopted as the water stop during the drilling process, the volume ratio of the phosphoric acid solution to the sodium silicate solution is 1:1, the sodium silicate of 40°Bé is diluted with water in a volume ratio of 1:1 to form the sodium silicate solution, the phosphoric acid is mixed with water in a ratio of 1:10 to form the phosphoric acid solution.

[0066] In order to obtain better grouting effect in the silt layer, the super-fine cement-sodium silicate double grout is adopted for grouting reinforcement, compared with the ordinary cement grout, the grouting effect is better, and the strength of the reinforced body is greater, and the following table shows the advantages and disadvantages of the super-fine cement-sodium silicate double grout and the ordinary cement-sodium silicate double grout.

[0067]

[0068] The single-hole grouting amount is calculated according to the following formula:

[0069] Q = πR 2 Hnα(1+β)

[0070] Q - single-hole grouting amount;

[0071] R - grouting slurry diffusion radius;

[0072] H - reinforcement depth;

[0073] n - porosity, 0.4 for this soil layer;

[0074] α - grouting filling coefficient, 0.8.

[0075] β - slurry loss rate, take 0.2.

[0076] The single-hole pre-grouting amount is 4.6m 3 .

[0077] 2, drilling and grouting

[0078] As Figure 4 shown, the flowchart of the pre-reinforcement.

[0079] Drilling and grouting operation is carried out on the scaffold platform inside the shield shell, using the advanced grouting hole on the bottom and middle of the shield machine to grout. Before grouting, open the gate valve at the reserved hole position, then install the drilling machine to drill and grout. The reinforcement range is 180° at the bottom of the tunnel, and the depth is 2m.

[0080] The drilling and grouting equipment of the segmented retreat grouting adopts a drill rod 10 with a diameter of 42mm. A ball tooth drill bit is installed at the front of the drill rod 10. The single-section drill rod 10 is 2m long. The drill rods 10 are connected by threads. The rotation direction of the threads is opposite to the rotation direction of the drilling. The drill rod 10 has a grouting channel inside. At the orifice of the shield machine reserved hole, a flange is used for connection and fixation. During the drilling and grouting process, the grout leakage is prevented by using a grout stopper and a blowout preventer.

[0081] The segmented retreat grouting adopts the principle of hole separation drilling and grouting. The circumferential distance between the drillings is 1.2m, and there are a total of 8 grouting holes. The grout diffusion radius is 0.8m. The same reserved hole is grouted at different angles. The first grouting angle is 13°, and the second grouting angle is 6°. The drill rod section number is recorded in detail to ensure that the drilling reaches the specified depth. The grouting range of each time is 6m (about 4 ring segments) from the front end of the cutter head. The reinforcement is carried out once every 4 ring segments. The single-hole grouting amount is 4.6m 3 .

[0082] After the drilling is completed, the hole is first sealed, and an appropriate amount of phosphoric acid mixed solution is injected to stop water. Then, superfine cement-silicate double liquid grout is injected. When the grouting pressure is reached, the drill rod is retreated by 0.5m each time, and the next section grouting is carried out. The cycle is repeated until the grouting of the hole is completed.

[0083] 3, advanced pre-reinforcement grouting management

[0084] (1) Grouting is carried out using the advanced grouting hole inside the shield machine;

[0085] (2) During the grouting process, the drill rod is lifted while grouting, and the lifting amplitude is strictly controlled;

[0086] (3) The grouting pressure is strictly controlled during the grouting process;

[0087] (4) During the grouting process, the cutter head should be rotated frequently to prevent the slurry from wrapping around the cutter head or shield.

[0088] In the embodiment, the telescopic support assembly supports the lower section tunnel 2 and extends forward synchronously with the excavation of the upper section tunnel 1.

[0089] In the embodiment, the telescopic support assembly comprises vertically and horizontally arranged hydraulic oil cylinders 17, one end of each of the hydraulic oil cylinders 17 being connected with one end of a telescopic hydraulic rod 16, the other end of the vertically arranged telescopic hydraulic rod 16 being connected with a vertical circular steel pipe 15, the other end of the horizontally arranged telescopic hydraulic rod 16 being connected with a horizontal circular steel pipe 20, the side wall of the vertical circular steel pipe 15 being connected with a detachable square steel pipe 19, the horizontal circular steel pipe 20 penetrating the detachable square steel pipe 19, the end of each of the hydraulic oil cylinders 17, the vertical circular steel pipe 15 and the horizontal circular steel pipe 20 being connected with an arc-shaped steel plate 14, the arc-shaped steel plate 14 having the same curvature as the inner diameter of the tunnel segment, two arc-shaped steel plates 14 being connected through a channel steel 18 along the tunnel excavation direction, the channel steel 18 being connected with the arc-shaped steel plate 14 through bolts, the length of the arc-shaped steel plate 14 in the vertical direction being greater than the length of the arc-shaped steel plate 14 in the horizontal direction, a reinforcing rib 13 being welded at the connection between the arc-shaped steel plate 14 and the vertical circular steel pipe 15 and the horizontal circular steel pipe 20, and a plurality of reinforcing ribs 13 being distributed at equal angles.

[0090] As shown in Figure 5 When the upper section tunnel 1 is excavated, the telescopic support assembly is arranged in the lower section tunnel 2 to support the lower section tunnel 2 and extend forward synchronously with the excavation of the upper section tunnel 1.

[0091] The telescopic support assembly is adopted to support each ring, which is composed of four arc-shaped steel plates 14 and four steel pipes, the arc-shaped steel plate 14 having the same curvature as the inner diameter of the segment, and the four steel pipes being telescopic hydraulic rods and circular steel pipes, which can be retracted to move forward and then be stretched out when the upper tunnel is excavated, the arc-shaped steel plate having a thickness of 25 mm and a width of 1000 mm, the upper and lower arc-shaped steel plates having a length of 4000 mm, and the left and right arc-shaped steel plates having a length of 2000 mm.

[0092] The telescopic pre-axial force steel pipe is a hydraulic rod plus a circular steel pipe, and adopts a telescopic hydraulic rod 16 and a hydraulic oil cylinder 17 to pre-axial force. The hydraulic oil cylinder 17 is welded on the arc-shaped steel plate 14 at one end, and the telescopic hydraulic rod 16 at the other end is welded on the vertical circular steel pipe 15 or the horizontal circular steel pipe 20. The other end of the vertical circular steel pipe 15 and the horizontal circular steel pipe 20 is welded with the arc-shaped steel plate 14. The diameter of the vertical circular steel pipe 15 and the horizontal circular steel pipe 20 is 60 mm, which is 10 mm smaller than the diameter of the telescopic hydraulic rod 16 connected by welding, facilitating welding. The wall thickness of the vertical circular steel pipe 15 and the horizontal circular steel pipe 20 is 20 mm, and the length is 300 mm. The bolt is used on the vertical circular steel pipe 15 to fix the detachable square steel pipe 19, which is used to bear the horizontal support rising. When the vertical telescopic hydraulic rod 16 rises to a certain height, the horizontal hydraulic device is operated to make the two ends of the arc-shaped steel plate 14 top to the pipe piece, and the detachable square steel pipe 19 is removed. The telescopic hydraulic rod 16 is continuously raised to make the upper arc-shaped steel plate 14 top to the pipe piece. When it is retracted, the operation is reversed.

[0093] The arc-shaped steel plate 14 is connected two by two along the tunneling direction by the channel steel 18, which is connected to the arc-shaped steel plate 14 by bolts. The channel steel 18 adopts a 10# channel steel with a height of 100 mm, a width of 48 mm, and a thickness of 5.3 mm.

[0094] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for constructing an up-and-down stacked interchange tunnel based on advanced pre-reinforcement, characterized in that, The construction method comprises the following steps: S1: constructing a lower interval tunnel (2) of an overlapping section and simultaneously grouting and reinforcing the lower interval tunnel (2); S2: performing secondary deep hole grouting and reinforcing on the soil at the top of the lower interval tunnel (2) to form a secondary deep hole grouting and reinforcing area (4); the secondary deep hole grouting and reinforcing in S2 is performed by in-hole deep hole grouting and reinforcing, the reinforcing range is 180° at the top, and the reinforcing depth is 3 m; the secondary deep hole grouting and reinforcing in S2 is performed by grouting through a grouting pipe in a hoisting hole reserved on the segment of the lower interval tunnel (2), the grouting slurry is cement-silicate double slurry, the water glass is diluted with water at a ratio of 1:3, the cement:water ratio is 1:1, the water glass:cement slurry ratio is 1:1, and the grouting amount is greater than or equal to 25 m³ per ring; S3: performing advanced pre-grouting and reinforcing in a shield machine on the soil at the bottom of an upper interval tunnel (1) of the overlapping section to form a shield machine advanced pre-reinforcing area (3); the advanced pre-grouting and reinforcing in S3 is performed by in-shield machine advanced pre-grouting and reinforcing, the reinforcing range is 180° at the bottom, and the reinforcing depth is 2 m; the advanced pre-grouting and reinforcing in S3 is performed by grouting and reinforcing through a drill machine in an advanced pre-grouting hole reserved in the shield machine, the hole diameter is 100 mm, the shield machine comprises a front shield (5), a cutter head (6), a middle shield (7), a shield tail (8) and a grouting platform (9), the soil layer below the front end of the cutter head (6) is reinforced by the advanced pre-grouting hole, the grouting is performed in a segmented and backward manner, the grouting slurry is superfine cement-silicate double slurry, the volume ratio is 1:1, the superfine cement is superfine cement of type MC-800, the water-cement ratio of the superfine cement slurry is 1:1, the Baume degree of the water glass is 38°Bé, the retarder is sodium dihydrogen phosphate, the dosage is 1% of the mass of the superfine cement, a phosphoric acid mixed solution is used to stop water during the drilling process, the volume ratio of the phosphoric acid solution to the water glass solution is 1:1, the water glass solution is prepared by diluting 40°Bé water glass with water at a ratio of 1:1, the phosphoric acid solution is prepared by mixing phosphoric acid with water at a ratio of 1:10; S4: erecting a telescopic support assembly in the lower interval tunnel (2) for reinforcement; the telescopic support assembly supports the lower interval tunnel (2) and is erected and extended forward synchronously with the excavation of the upper interval tunnel (1); the telescopic support assembly comprises vertically and horizontally arranged hydraulic cylinders (17), one end of each hydraulic cylinder (17) is connected to one end of a telescopic hydraulic rod (16), the other end of the vertically arranged telescopic hydraulic rod (16) is connected to a vertically arranged circular steel pipe (15), the other end of the horizontally arranged telescopic hydraulic rod (16) is connected to a horizontally arranged circular steel pipe (20), the side wall of the vertically arranged circular steel pipe (15) is connected to a detachable square steel pipe (19), the horizontally arranged circular steel pipe (20) penetrates the detachable square steel pipe (19), the end of each of the hydraulic cylinders (17), the vertically arranged circular steel pipe (15) and the horizontally arranged circular steel pipe (20) is connected to an arc-shaped steel plate (14), and the arc-shaped steel plate (14) has the same curvature as the inner diameter of the tunnel segment. S5: Constructing the upper section tunnel (1) of the overlapping section and performing synchronous grouting reinforcement and secondary grouting reinforcement on the upper section tunnel (1).

2. The method according to claim 1, wherein, The drilling and grouting equipment adopts a drill rod (10) with a diameter of 42 mm, a ball-toothed drill bit is installed at the front end of the drill rod (10), the single-section drill rod (10) is 2 m long, the drill rods (10) are connected through threads, the rotation direction of the threads is opposite to the rotation direction of the drilling, the drill rod (10) is provided with a grouting channel, a flange plate is used for connecting and fixing at the hole opening of the shield machine reserved hole, and a grout stopper and a blowout preventer are used to prevent grout leakage during drilling and grouting.

3. The method according to claim 2, wherein, The segmented back-off grouting adopts the principle of hole spacing drilling and grouting, the annular spacing between the drill holes is 1.2 m, a total of 8 grouting holes, the grout diffusion radius is 0.8 m, different angles are used for grouting for the same reserved hole, the first grouting angle is 13°, the second grouting angle is 6°, the drill rod section is recorded in detail to ensure that the drill hole reaches the specified depth, the grouting range is 6 m in front of the cutter head each time, the reinforcement is performed once every 4 ring segments, and the single-hole grouting amount is 4.6 m³; After the drilling is completed, the hole is first sealed, an appropriate amount of phosphoric acid mixed solution is injected to stop water, and then ultra-fine cement-sodium silicate double-liquid slurry is injected, the drill rod is retracted when the grouting pressure reaches, the drill rod is retracted by 0.5 m each time, the next section grouting is performed, and the cycle is repeated until the hole grouting is completed.

4. The method according to claim 2, wherein, The two arc-shaped steel plates (14) are connected through the channel steel (18) along the tunnel excavation direction, the channel steel (18) is connected with the arc-shaped steel plate (14) through bolts, and the length of the arc-shaped steel plate (14) in the vertical direction is greater than the length of the arc-shaped steel plate (14) in the horizontal direction.

5. The method according to claim 4, wherein, The arc-shaped steel plate (14) is connected with the vertical circular steel pipe (15) and the horizontal circular steel pipe (20), and the connecting positions are all welded with stiffening ribs (13), and the stiffening ribs (13) are distributed at equal angles.

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