Shield launching reinforcement construction process rich in weathered sand and silty clay layer

Abstract

The invention relates to the technical field of shield tunnel construction, in particular to a shield launching reinforcement construction process rich in weathered sand and silty clay layers. The construction technology comprises the steps of construction preparation, tunnel portal steel ring pre-burying and grouting channel arrangement, first tunnel portal sealing device installation, second tunnel portal sealing device installation, shield launching and sealing grouting, the first tunnel portal sealing device and the second tunnel portal sealing device are fixed through the pre-buried tunnel portal steel ring, and then two sealing protections are formed. And in addition, sealing grouting is conducted on the tunnel portal steel ring after shield launching, and then third sealing protection is formed. Therefore, the shield launching reinforcement construction process rich in the weathered sand and silty clay layer can ensure that the safety risk of the whole launching process is controllable, has the advantages of reasonable and efficient construction organization and good sealing effect on a tunnel portal, and avoids a steel sleeve construction mode in the prior art, so that the construction period of a launching section can be greatly shortened, and the construction efficiency is improved. The construction cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of shield tunnel construction, and in particular to a shield initial reinforcement construction process for a layer rich in weathered sand and silty clay. Background Art

[0002] With the continuous development of my country's water conservancy engineering industry, shield construction, which has a higher safety factor, less impact on ground traffic, less interference from climate change, and more efficient construction, has become an important means of hydraulic tunnel construction in water conservancy projects. The start of shield construction is one of the most risky links in shield tunneling. If the stratum reinforcement effect is not good and the reinforcement measures are not in place, it is very easy to cause water and soil instability when the tunnel portal is broken, resulting in safety accidents such as tunnel portal collapse, ground collapse, pipeline rupture, and building (structure) tilt. Therefore, how to ensure the stability of the starting end when the tunnel portal is broken is the key point to ensure the smooth start of the shield.

[0003] At present, in shield tunnel construction, the strata that require shields are often rich in weathered sand and silty clay. For example, the starting mileage of the L3-L2 shield section of the first section of the raw water pipeline project (main section) of the Lianhuashan-Luhuakeng Water Plant section is LK1+801.031~LK4+011.071. The section adopts the earth pressure balance shield method, starting from the L3 working shaft, with an inner diameter of 14m, a well depth of 21.33m, and a tunnel burial depth of 12.1m~16.9m. The strata passed through are mainly fully weathered sand, residual slope soil, and plastic~hard plastic sandy clay. The starting mileage of the L4-L3 shield section of the second bid section of the raw water pipeline project (main section) of the Lianhuashan-Luhuakeng Water Plant Section is LK1+011.071~LK5+520.836. The section adopts the earth pressure balance shield method, starting from the L4 working shaft, with an inner diameter of 14m, a well depth of 22.54m, and a tunnel burial depth of 11.2~32.7m. The strata passed through are mainly weak to slightly weathered granite gneiss, weakly weathered granite gneiss, and local soft upper and hard lower strata. This type of strata has the following technical problems: complex geology, poor pile effect of sandy geology with high pressure water, and it is difficult to effectively reinforce the end.

[0004] In the prior art, the invention patent application with publication number CN111411970A discloses a shield construction method under water-rich sand geological conditions. This method uses three-axis mixing piles to construct a water-stop curtain and high-pressure jet grouting piles to make interlayer reinforcement. Although the reinforcement range is wide, the construction cost is high, and when there are important pipelines or buildings at the end, it is impossible to achieve full-range reinforcement.

[0005] In addition, in the prior art, in order to improve the initial sealing of the shield, a steel casing is often used for initial construction, and an inert slurry is filled in it to ensure its water tightness. However, it has the disadvantages of high investment in the steel casing and grouting, and a long installation period. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a shield starting reinforcement construction process for a layer rich in weathered sand and silty clay. The shield starting reinforcement construction process for a layer rich in weathered sand and silty clay can ensure that the safety risks of the entire starting process are controllable, the construction organization is reasonable and efficient, the sealing effect of the tunnel door is good, the steel sleeve construction is avoided, the starting section construction period is greatly shortened, and the construction cost is reduced.

[0007] In order to achieve the purpose of the above invention, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a shield initial reinforcement construction process for a layer rich in weathered sand and silty clay, comprising the following steps:

[0009] S1. Construction preparation: Carry out engineering positioning measurement (including axis control and elevation control), and make tunnel gate steel ring, curtain pressure plate and tunnel gate brush;

[0010] Among them, engineering positioning measurement includes measurement operations such as axis control and elevation control.

[0011] S2. Pre-embed the tunnel gate steel ring and set up a grouting channel: pre-embed the tunnel gate steel ring into the tunnel gate lining wall, and connect the grouting channel with the grouting hole of the tunnel gate steel ring;

[0012] S3, installing the first tunnel door sealing device: the first tunnel door sealing device is composed of a tunnel door rubber curtain cloth, a circular ring plate and a plurality of curtain cloth pressure plates, and the first tunnel door sealing device is fixed to the end of the tunnel door steel ring close to the starting point;

[0013] S4, installing a second tunnel door sealing device: fixing a second tunnel door sealing device on the inner wall surface of the tunnel door steel ring, wherein the second tunnel door sealing device is a tunnel door brush;

[0014] S5, shield machine starts: first, the cutter head of the shield machine passes through the curtain pressure plate of the first tunnel door sealing device, and after the shield machine continues to move forward and reaches the tunnel door brush, the curtain pressure plate, the tunnel door rubber curtain and the tunnel door brush are closely attached to the shield body of the shield machine, and then the cutter head is started to break the ground-connected wall;

[0015] S5. Sealing grouting: When the ground connection wall is broken and the shield body of the shield machine passes through the second tunnel portal sealing device, the phosphoric acid reinforcement liquid is injected into the internal gap of the tunnel portal steel ring through the grouting channel and the grouting holes of the tunnel portal steel ring. When the tail of the shield machine passes through the ground connection wall, the double liquid slurry is used to seal the tunnel portal again, thereby completing the initial stage of the shield machine.

[0016] Furthermore, in the step S2, the portal steel ring is provided with a plurality of grouting holes, and the plurality of grouting holes are evenly arranged along the portal steel ring; and the plurality of grouting holes are all connected to the grouting channel.

[0017] Furthermore, the circumferential spacing between the multiple grouting holes is 60°.

[0018] Furthermore, in the step S3, an annular mounting portion is provided at the end of the tunnel gate steel ring close to the starting point, the tunnel gate rubber curtain and the circular ring plate are successively installed on the annular mounting portion of the tunnel gate steel ring through stud bolts, and the several curtain pressure plates are installed on the circular ring plate.

[0019] Further, a plurality of fixing plates are arranged on the outer peripheral edge of the circular plate, and the plurality of curtain cloth pressing plates are respectively mounted on the circular plate through the plurality of fixing plates; and / or

[0020] The curtain cloth pressing plate is movably connected to the fixing plate through a pin.

[0021] Furthermore, an outer flange is provided at the end of the tunnel door rubber curtain; and / or

[0022] The outer flange faces the originating direction.

[0023] Furthermore, in the step S3, the process step of installing the first tunnel door sealing device includes the following steps:

[0024] 1) Installing stud bolts: inserting a plurality of stud bolts into the installation holes of the tunnel gate steel ring respectively;

[0025] 2) Installing the tunnel door rubber curtain: installing the tunnel door rubber curtain on the stud bolt;

[0026] 3) Installing the annular plate: installing the annular plate on the stud bolts;

[0027] 4) Installing washers and nuts: Installing washers and nuts on the stud bolts to fix the tunnel door rubber curtain and the circular ring plate on the tunnel door steel ring;

[0028] 5) Installing the curtain cloth pressure plate: installing a plurality of the curtain cloth pressure plates on the outer peripheral edge of the annular plate through fixing plates and pins respectively.

[0029] Furthermore, in step S4, the tunnel gate brush is a tunnel gate brush made of steel wire, and the length of the tunnel gate brush is 280mm-320mm.

[0030] Furthermore, in the step S5, the phosphoric acid strengthening liquid is prepared from water, water glass and phosphoric acid, and the mass ratio of the water, water glass and phosphoric acid is 1:1:0.05.

[0031] Furthermore, in the step S5, the double liquid slurry is prepared by cement slurry and water glass in a volume ratio of 1:1, and the cement slurry is made of water and cement in a mass ratio of 1:1;

[0032] The setting time of the double liquid slurry is 20s to 48s, and the grouting pressure of the double liquid slurry is controlled within 2bar to 3bar;

[0033] In the step S5, when the tail of the shield machine passes through the ground-connected wall and the shield tail has assembled 5 to 10 rings of segments, the double-liquid slurry is used to seal the tunnel door again, thereby completing the initial stage of the shield machine.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention provides a shield starting reinforcement construction process for a layer rich in weathered sand and silty clay, including construction preparation, pre-embedded portal steel rings and setting up grouting channels, installation of a first portal sealing device, installation of a second portal sealing device, shield starting and sealing grouting steps. The first portal sealing device and the second portal sealing device are fixed by pre-embedded portal steel rings to form two sealing protections. In addition, sealing grouting of the portal steel ring is performed after the shield starts, thereby forming a third sealing protection. Therefore, the shield starting reinforcement construction process for a layer rich in weathered sand and silty clay can ensure that the safety risks of the entire starting process are controllable, and has the advantages of reasonable and efficient construction organization and good sealing effect on the portal.

[0036] (2) The shield tunneling starting reinforcement construction process of the present invention, which is rich in weathered sand and silty clay layers, avoids the steel sleeve construction method of the prior art by adopting a tunnel portal steel ring in coordination with three sealing protections. Therefore, the present application can significantly shorten the construction period of the starting section and reduce construction costs.

[0037] (3) The shield tunneling reinforcement construction process of the present invention, which is rich in weathered sand and silty clay layers, has the advantage of fast construction. By relying on the portal steel ring built into the circular working shaft portal wall, there is no need to extend the efficient construction process of the portal steel ring, thereby ensuring the fast and efficient construction process.

[0038] (4) The shield tunneling reinforcement construction process of the present invention, which is rich in weathered sand and silty clay layers, has the advantages of safe and controllable construction. By implementing three sealing measures, the tunnel door is sealed in real time and tightly, and a multi-layer protection system is constructed, thereby ensuring the safety and controllability of the entire shield tunneling process.

[0039] (5) The shield starting reinforcement construction process of the present invention, which is rich in weathered sand and silty clay layers, has the advantage of a wide range of applications. It can be used as an effective reinforcement method for the problems encountered in water conservancy, subway and other engineering fields in terms of end reinforcement, such as great difficulty in implementation, unsatisfactory results, and insufficient reinforcement length. It is suitable for the starting process of mud water and earth pressure balance shield tunneling, and exhibits strong applicability and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 It is a structural schematic diagram of three-layer sealing protection of a shield initial reinforcement construction process rich in weathered sand and silty clay layers of the present invention.

[0042] Figure 2 The present invention is a schematic structural diagram of a tunnel portal steel ring for a shield tunneling initial reinforcement construction process for a layer rich in weathered sand and silty clay.

[0043] Figure 3 The invention discloses a schematic diagram of the installation of a curtain pressure plate for a shield starting reinforcement construction process for a layer rich in weathered sand and silty clay.

[0044] Figure 4 The present invention is a schematic diagram of the tunnel opening structure before starting a shield tunneling initial reinforcement construction process for a layer rich in weathered sand and silty clay.

[0045] Figure 5 It is a structural schematic diagram of a shield initial reinforcement construction process rich in weathered sand and silty clay layers in the initial preparation stage of the present invention.

[0046] Figure 6 It is a structural schematic diagram of a shield initial reinforcement construction process of the present invention for a layer rich in weathered sand and silty clay at the stage where the cutter head reaches the tunnel face.

[0047] Figure 7 It is a structural schematic diagram of a shield machine's tail shield passing through a tunnel portal steel ring in a shield starting reinforcement construction process rich in weathered sand and silty clay layers of the present invention.

[0048] Figure 8 It is a structural schematic diagram of a shield initial reinforcement construction process of the present invention for a layer rich in weathered sand and silty clay at the stage of using double liquid slurry for plugging.

[0049] Reference numerals:

[0050] Tunnel gate steel ring 1, grouting hole 101, annular mounting portion 102, mounting hole 103, curtain pressure plate 2, tunnel gate brush 3, tunnel gate lining wall 4, grouting channel 5, tunnel gate rubber curtain 6, outer flange 601, circular ring plate 7, stud bolts 8, fixing plate 9, pin 10, shield tail brush 11, cutter head 12, shield body 13, ground connection wall 14, anchor bar 15, bolt hole 16. DETAILED DESCRIPTION

[0051] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. In the present invention, the singular forms "a", "said" and "the" used in the embodiments and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0053] The following describes the invention in conjunction with specific embodiments.

[0054] Example 1

[0055] A shield initial reinforcement construction process of a layer rich in weathered sand and silty clay in this embodiment, such as Figures 1 to 8 As shown, the following steps are included:

[0056] S1. Construction preparation: Carry out engineering positioning measurement, and make the tunnel gate steel ring 1, curtain pressure plate 2 and tunnel gate brush 3; in this embodiment, engineering positioning measurement includes measurement operations such as axis control and elevation control of the tunnel gate. In addition, it is necessary to conduct preliminary review and re-measurement of the design axis, and determine the availability of water, electricity, roads and information on the site, determine the plan for mud preparation, transportation, recovery and external transportation and implement it in detail, and assemble and debug the construction equipment to meet the use requirements.

[0057] S2, pre-embed the portal steel ring and set the grouting channel: pre-embed the portal steel ring 1 into the portal inner lining wall 4, and connect the grouting channel 5 with the grouting hole 101 of the portal steel ring 1. The portal steel ring 1 is fixed to the portal inner lining wall 4 by anchor bars 15.

[0058] In this embodiment, in step S2, the portal steel ring 1 is provided with a plurality of grouting holes 101, and the plurality of grouting holes 101 are evenly arranged along the portal steel ring 1; the plurality of grouting holes 101 are all connected to the grouting channel 5. In this embodiment, the circumferential spacing between the plurality of grouting holes 101 is 60°.

[0059] Among them, in order to prevent the loss of soil, groundwater, etc. from the gap between the shield shell and the portal when the shield starts to excavate, as well as the loss of grouting slurry from the shield tail through the back lining of the portal, and to achieve an immediate sealing effect when the shield starts, during the construction of the portal lining wall 4, a grouting channel is pre-buried and connected to the portal steel ring 1, so that the subsequent sealing grouting step can be achieved to form a third layer of sealing protection.

[0060] S3, installing the first tunnel door sealing device: the first tunnel door sealing device is composed of a tunnel door rubber curtain cloth 6, a circular ring plate 7 and a plurality of curtain cloth pressure plates 2, and the first tunnel door sealing device is fixed to the end of the tunnel door steel ring 1 close to the starting point;

[0061] In this embodiment, in step S3, an annular mounting portion 102 is provided at the end of the tunnel gate steel ring 1 near the starting point, the tunnel gate rubber curtain 6 and the circular ring plate 7 are sequentially mounted on the annular mounting portion 102 of the tunnel gate steel ring 1 through stud bolts 8, and a plurality of curtain pressure plates 2 are mounted on the circular ring plate 7. Bolt holes 16 are provided on both the tunnel gate rubber curtain 6 and the circular ring plate 7.

[0062] In this embodiment, a plurality of fixing plates 9 are provided on the outer peripheral edge of the circular plate 7, and a plurality of curtain pressure plates 2 are respectively installed on the circular plate 7 through the plurality of fixing plates 9; wherein the curtain pressure plates 2 are movably connected to the fixing plates 9 through pins 10, thereby facilitating the curtain pressure plates 2 to press the shield body when the shield machine passes by.

[0063] In this embodiment, an outer flange 601 is provided at the end of the tunnel door rubber curtain 6; wherein the outer flange 601 faces the starting direction. wherein the outer flange 601 faces the starting direction to ensure the sealing effect of the tunnel door. in addition, to ensure smooth entry into the tunnel, the outer diameter of the shield cutterhead is set to 4350mm, the inner diameter of the tunnel door steel ring 1 is set to 4600mm, and after the shield body of the shield machine enters the tunnel door wall, a gap of 250mm will be formed between the inner lining wall 4 of the tunnel door and the front body casing of the shield machine.

[0064] In this embodiment, in step S3, the process step of installing the first tunnel door sealing device includes the following steps:

[0065] 1) Installing stud bolts: inserting a plurality of stud bolts 8 into the mounting holes 103 of the tunnel steel ring 1 respectively;

[0066] 2) Install the tunnel door rubber curtain: install the tunnel door rubber curtain 6 on the stud bolt 8;

[0067] 3) Install the annular plate: Install the annular plate 7 on the stud bolt 8;

[0068] 4) Installing washers and nuts: Install washers and nuts on stud bolts 8 to fix the tunnel rubber curtain 6 and circular ring plate 7 on the tunnel steel ring 1;

[0069] 5) Install the curtain pressure plate: install several curtain pressure plates 2 on the outer peripheral edge of the annular plate 7 through the fixing plate 9 and the pin 10 respectively.

[0070] S4, installing the second tunnel door sealing device: the second tunnel door sealing device is fixedly installed on the inner wall surface of the tunnel door steel ring 1, and the second tunnel door sealing device is a tunnel door brush 3. The tunnel door brush 3 and the tunnel door steel ring 1 are fixed by welding.

[0071] In this embodiment, in step S4, the tunnel gate brush 3 is a tunnel gate brush 3 made of steel wire. The length of the tunnel gate brush 3 is 280 mm-320 mm. In this embodiment, the length of the tunnel gate brush 3 is 300 mm, which can well prevent the external slurry from flowing out when the shield starts, causing accidents such as surface collapse.

[0072] S5, shield machine starts: first, the shield machine cutter head 12 is used to pass through the curtain pressure plate 2 of the first tunnel door sealing device. After the shield machine continues to move forward and reaches the location of the second tunnel door sealing device, the curtain pressure plate 2, the tunnel door rubber curtain 6 and the tunnel door brush 3 are closely attached to the shield body 13 of the shield machine, and then the cutter head 12 is started to break the ground connection wall 14. In addition, the shield body 13 of the shield machine is also equipped with a shield tail brush 11 for its own protection.

[0073] When the cutter head 12 breaks the ground-connected wall 14, the screw machine gate is closed to keep the slag of the ground-connected wall 14 in the cutter head 12 of the shield machine. At the same time, according to the torque and thrust of the cutter head 12, the sealing condition of the reaction frame and the rubber curtain 6 of the tunnel door is monitored, the foam system is turned on, and the soil pressure begins to build up in the soil bin.

[0074] S5, sealing grouting: when the ground connection wall 14 is broken and the shield body 13 of the shield machine passes through the second tunnel portal sealing device, the phosphoric acid reinforcement liquid is injected into the internal gap of the tunnel portal steel ring 1 through the grouting channel 5 and the grouting hole 101 of the tunnel portal steel ring 1. When the tail of the shield machine passes through the ground connection wall and the shield tail completes the assembly of 5 to 10 rings of segments, the double liquid slurry is used to seal the tunnel portal again, thereby completing the initial stage of the shield machine.

[0075] Among them, by injecting the phosphoric acid reinforcing liquid into the internal gap of the tunnel portal steel ring 1 through the grouting channel 5 and the grouting hole 101 of the tunnel portal steel ring 1, the gap caused by the inability of the tunnel portal brush 3 and the assembled pipe segments to fit tightly after the shield body 13 of the shield machine completely passes through the tunnel portal brush 3 can be reduced, and at the same time, the shield tail can be prevented from being locked.

[0076] Among them, since the strength of the phosphoric acid reinforcement liquid is relatively low, it cannot withstand the high pressure generated in the subsequent synchronous grouting process and cannot be used as the final sealing material. Therefore, double liquid slurry needs to be injected subsequently.

[0077] In this embodiment, in step S5, the phosphoric acid strengthening liquid is prepared from water, water glass and phosphoric acid, wherein the mass ratio of water, water glass and phosphoric acid is 1:1:0.05.

[0078] In this embodiment, in step S5, the double liquid slurry is prepared by cement slurry and water glass in a volume ratio of 1:1, and the cement slurry is made of water and cement in a mass ratio of 1:1; wherein, the coagulation time of the double liquid slurry is 20s to 48s, and the grouting pressure of the double liquid slurry is controlled within 2bar-3bar.

[0079] Among them, after the cutter head 12 of the shield machine enters the tunnel portal, close attention should be paid to the first tunnel portal sealing device and the second tunnel portal sealing device. If the tunnel portal rubber curtain cloth 6 is found to be damaged, timely measures should be taken to ensure that the curtain pressure plate 2 presses the tunnel portal rubber curtain cloth 6 well, thereby ensuring a good sealing effect.

[0080] In the process of negative ring excavation by the shield machine, the cutter head 12 of the shield machine passes through the curtain pressure plate 2 arranged in front. When the cutter head 12 contacts the curtain pressure plate 2, the rubber curtain 6 of the tunnel door will be deformed due to the pressure applied by the cutter head 12 and then fit with the cutter head 12 and the front shield of the shield machine, thus forming the first sealing protection.

[0081] After the second tunnel door sealing device is installed, in order to prevent debris from falling into the tunnel door brush 3 during the advancement of the shield machine, thereby affecting the sealing of the tunnel door, it is necessary to do a good job of cleaning before starting the shield machine.

[0082] After the cutter head 12 of the shield machine passes through the curtain pressure plate 2, it continues to move forward and presses the tunnel gate brush 3. The tunnel gate brush 3 is deformed by the force and fits tightly against the cutter head 12 to form a second sealing protection. After the cutter head 12 contacts the tunnel face, the tunnel gate brush 3 and the tunnel gate rubber curtain 6 fit tightly against the front shield of the shield machine, and the cutter head 12 begins to destroy the inner edge of the ground-connected wall 14.

[0083] The shield starting reinforcement construction process of the present invention, which is rich in weathered sand and silty clay layers, includes construction preparation, pre-embedded tunnel portal steel rings and setting grouting channels, installation of the first tunnel portal sealing device, installation of the second tunnel portal sealing device, shield starting and sealing grouting steps, wherein the first tunnel portal sealing device and the second tunnel portal sealing device are fixed by the pre-embedded tunnel portal steel ring 1, thereby forming two sealing protections, and further, the third sealing protection is formed by sealing grouting the tunnel portal steel ring 1 after the shield starts. Therefore, the shield starting reinforcement construction process, which is rich in weathered sand and silty clay layers, can ensure that the safety risks of the entire starting process are controllable, and has the advantages of reasonable and efficient construction organization and good sealing effect on the tunnel portal.

[0084] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay, characterized in that: The following steps are involved: S1. Construction preparation: Carry out engineering positioning measurement, and make tunnel door steel ring, curtain pressure plate and tunnel door brush; S2. Pre-embed the tunnel gate steel ring and set up a grouting channel: pre-embed the tunnel gate steel ring into the tunnel gate lining wall, and connect the grouting channel with the grouting hole of the tunnel gate steel ring; S3, installing the first tunnel door sealing device: the first tunnel door sealing device is composed of a tunnel door rubber curtain cloth, a circular ring plate and a plurality of curtain cloth pressure plates, and the first tunnel door sealing device is fixed to the end of the tunnel door steel ring close to the starting point; S4, installing a second tunnel door sealing device: fixing a second tunnel door sealing device on the inner wall surface of the tunnel door steel ring, wherein the second tunnel door sealing device is a tunnel door brush; S5, shield machine starts: first, the cutter head of the shield machine passes through the curtain pressure plate of the first tunnel door sealing device, and after the shield machine continues to move forward and reaches the tunnel door brush, the curtain pressure plate, the tunnel door rubber curtain and the tunnel door brush are closely attached to the shield body of the shield machine, and then the cutter head is started to break the ground-connected wall; S5. Sealing grouting: When the ground connection wall is broken and the shield body of the shield machine passes through the second tunnel portal sealing device, the phosphoric acid reinforcement liquid is injected into the internal gap of the tunnel portal steel ring through the grouting channel and the grouting holes of the tunnel portal steel ring. When the tail of the shield machine passes through the ground connection wall, the double liquid slurry is used to seal the tunnel portal again, thereby completing the initial stage of the shield machine.

2. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 1, characterized in that: In the step S2, the tunnel gate steel ring is provided with a plurality of grouting holes, and the plurality of grouting holes are evenly arranged along the tunnel gate steel ring; and the plurality of grouting holes are all connected to the grouting channel.

3. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 2, characterized in that: The circumferential spacing between the multiple grouting holes is 60°.

4. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 1, characterized in that: In the step S3, an annular mounting portion is provided at the end of the tunnel gate steel ring close to the starting point, the tunnel gate rubber curtain and the circular ring plate are successively mounted on the annular mounting portion of the tunnel gate steel ring through stud bolts, and the plurality of curtain pressure plates are mounted on the circular ring plate.

5. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 4, characterized in that: A plurality of fixing plates are arranged on the outer peripheral edge of the circular plate, and the plurality of curtain cloth pressing plates are respectively mounted on the circular plate through the plurality of fixing plates; and / or The curtain cloth pressing plate is movably connected to the fixing plate through a pin.

6. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 4, characterized in that: The end of the tunnel door rubber curtain is provided with an outer flange; and / or The outer flange faces the originating direction.

7. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 1, characterized in that: In the step S3, the process of installing the first tunnel door sealing device includes the following steps: 1) Installing stud bolts: inserting a plurality of stud bolts into the installation holes of the tunnel gate steel ring respectively; 2) Installing the tunnel door rubber curtain: installing the tunnel door rubber curtain on the stud bolt; 3) Installing the annular plate: installing the annular plate on the stud bolts; 4) Installing nuts: Installing nuts on the stud bolts to fix the tunnel door rubber curtain and the circular ring plate on the tunnel door steel ring; 5) Installing the curtain cloth pressure plate: installing a plurality of the curtain cloth pressure plates on the outer peripheral edge of the annular plate through fixing plates and pins respectively.

8. The shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 1, characterized in that: In the step S4, the tunnel door brush is a tunnel door brush made of steel wire, and the length of the tunnel door brush is 280mm-320mm.

9. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 1, characterized in that: In the step S5, the phosphoric acid strengthening liquid is prepared from water, water glass and phosphoric acid, and the mass ratio of the water, water glass and phosphoric acid is 1:1:0.

05.

10. A shield initial reinforcement construction process for a layer rich in weathered sand and silty clay as claimed in claim 1, characterized in that: In the step S5, the double liquid slurry is prepared by cement slurry and water glass in a volume ratio of 1:1, and the cement slurry is made of water and cement in a mass ratio of 1:1; The coagulation time of the double liquid slurry is 20s to 48s, and the grouting pressure of the double liquid slurry is controlled within 2bar to 3bar; In the step S5, when the tail of the shield machine passes through the ground-connected wall and the shield tail has assembled 5 to 10 rings of segments, the double-liquid slurry is used to seal the tunnel door again, thereby completing the initial stage of the shield machine.

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