Shield well end reinforcement method

Abstract

The invention discloses a shield well end reinforcing method, and relates to the technical field of shield well construction.The shield well end reinforcing method comprises the steps that a shield well enclosure structure is arranged on the inner wall of a shield well in the circumferential direction of the shield well end; a plurality of outer covering plain walls are arranged at the large mileage end and the small mileage end of the shield well in the circumferential direction of the end of the shield well and on the outer side of the shield well; a three-shaft stirring pile is arranged between the outer wrapping plain wall and the shield well; connecting the three-axis stirring pile with the shield well enclosure structure, and performing joint reinforcement on the joint of the three-axis stirring pile and the shield well enclosure structure; and a reinforcing body is obtained, and the end of the shield well is reinforced. By means of the combined reinforcement measure that the enclosure structure, the outer plain wall and the three-axis stirring piles are arranged around the shield well end, the overall stability and bearing capacity of the shield well end can be effectively improved, and stratum loss and deformation are effectively limited through connector reinforcement.

Description

Technical Field

[0001] The present invention relates to the technical field of shield well construction, and particularly relates to a method for reinforcing the end of a shield well. Background Art

[0002] With the development and utilization of urban underground space, the shield tunneling construction technology has been widely applied. As one of the key links in shield tunnel construction, the construction quality of the end of the shield well directly affects the safety and service life of the tunnel project. At present, the end of the shield well is mainly reinforced by a reinforced concrete structure. By setting a steel mesh around the end and pouring high-strength concrete, a solid whole is formed. However, the end of the shield well is prone to deformation due to uneven settlement after reinforcement. Summary of the Invention

[0003] The main object of the present invention is to propose a method for reinforcing the end of a shield well, aiming to improve the anti-deformation ability of the end of the shield well after reinforcement.

[0004] To achieve the above object, the method for reinforcing the end of a shield well proposed by the present invention includes:

[0005] Arranging a shield well enclosure structure on the inner wall of the shield well along the circumferential direction of the end of the shield well;

[0006] Arranging a plurality of outer envelope plain walls on the outside of the shield well along the circumferential direction of the end of the shield well at the large mileage end and the small mileage end of the shield well respectively; wherein, each of the outer envelope plain walls penetrates the sand layer at the bottom of the shield well from top to bottom and extends into the strongly weathered layer below the sand layer, and the length of each of the outer envelope plain walls extending into the strongly weathered layer is at least 1 m;

[0007] Arranging triaxial mixing piles between the outer envelope plain walls and the shield well;

[0008] Connecting the triaxial mixing piles to the shield well enclosure structure and performing interface reinforcement on the connection between the triaxial mixing piles and the shield well enclosure structure;

[0009] Obtaining a reinforced body and completing the reinforcement of the end of the shield well.

[0010] In an embodiment, the step of arranging triaxial mixing piles between the outer envelope plain walls and the shield well includes:

[0011] Using a three-tube jet grouting rig to drill holes from the ground downward between the outer envelope plain walls and the shield well to penetrate the sand layer and the strongly weathered layer and extend to the bottom of the consolidated silt clay layer below the strongly weathered layer to form pile holes;

[0012] Pouring the pile holes to form the triaxial mixing piles.

[0013] In one embodiment, the steps of pouring the pile hole to form the triaxial mixing pile include:

[0014] Start the mixing head on the triple-tube jet grouting rig and lift it upward from the bottom of the hole while continuing to grout and mix until the mixing head is lifted to the ground.

[0015] In one embodiment, the steps of connecting the triaxial mixing pile to the shield shaft retaining structure and strengthening the interface at the connection between the triaxial mixing pile and the shield shaft retaining structure include:

[0016] Connect the triaxial mixing pile to the shield shaft retaining structure;

[0017] Arrange triple-tube jet grouting piles at the connection between the triaxial mixing pile and the shield shaft retaining structure to strengthen the interface at the connection between the triaxial mixing pile and the shield shaft retaining structure.

[0018] In one embodiment, the steps of arranging triple-tube jet grouting piles at the connection between the triaxial mixing pile and the shield shaft retaining structure to strengthen the interface at the connection between the triaxial mixing pile and the shield shaft retaining structure include:

[0019] Use a triple-tube jet grouting rig to drill a hole downward from the ground at the connection between the triaxial mixing pile and the shield shaft retaining structure;

[0020] During the drilling process of the triple-tube jet grouting rig, inject cement slurry into the bottom of the hole through the outer pipe of the drill rod of the triple-tube jet grouting rig at a grouting pressure of 20 MPa to 30 MPa, inject compressed air into the bottom of the hole through the middle pipe of the drill rod of the triple-tube jet grouting rig at an air pressure of 0.8 MPa to 1.2 MPa, and inject water into the bottom of the hole through the inner pipe of the drill rod of the triple-tube jet grouting rig at a water pressure of 30 MPa to 50 MPa to form a column of cement soil;

[0021] Repeat the above steps to arrange three columns of cement soil with a diameter of 800 mm and a spacing of 600 mm at the connection of the shield shaft retaining structure to form the triple-tube jet grouting pile to strengthen the interface at the connection between the triaxial mixing pile and the shield shaft retaining structure.

[0022] In one embodiment, after the steps of obtaining the reinforced body and completing the reinforcement of the shield shaft end, the shield shaft end reinforcement method further includes:

[0023] Drill a core sample from the reinforced body;

[0024] Test the core sample to obtain a test result;

[0025] Judge whether the test result meets the preset conditions;

[0026] If not, reinforce or re - reinforce the end of the shield shaft.

[0027] In one embodiment, the step of drilling core samples from the reinforced body includes:

[0028] Drill core samples of the reinforced body within 28 days after construction completion; the number of the core samples is not less than 3, the diameter of the core samples is greater than or equal to 100 mm, and the length of the core samples is greater than or equal to 1000 mm.

[0029] In one embodiment, the step of testing the core samples to obtain the test results includes:

[0030] Under the condition of no lateral restraint, squeeze each of the core samples respectively to obtain the maximum axial compressive stress that each core sample can withstand.

[0031] Obtain the overall strength evaluation value of the reinforced body according to the maximum axial compressive stress, and take the overall strength evaluation value as the test result.

[0032] In one embodiment, the step of judging whether the test result meets the preset conditions includes:

[0033] Judge whether the overall strength evaluation value is greater than or equal to 1.0 MPa.

[0034] If not, it does not meet the preset conditions; if so, it meets the preset conditions.

[0035] In one embodiment, if not, the step of reinforcing or re - reinforcing the end of the shield shaft includes:

[0036] If the test result does not meet the preset conditions, reinforce or re - reinforce the end of the shield shaft by means of grouting and / or jet grouting.

[0037] The technical solution of the present invention can effectively improve the overall stability and bearing capacity of the end of the shield shaft through the combined reinforcement measures of setting a retaining structure, an outer - wrapped plain wall and a triple - axis mixing pile around the end of the shield shaft, and integrate each reinforced part into a solid whole through interface reinforcement, so as to effectively limit the ground loss and deformation, and control the ground settlement and building deformation within the allowable range. It not only solves the problem of deformation of the end of the shield shaft caused by uneven settlement, but also has the advantages of simple construction technology, high mechanization degree, fast construction progress and relatively low cost. It is applicable to various soil conditions, especially the soft silt layer, and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0039] Figure 1 It is a schematic flow chart of an embodiment of the shield well end reinforcement method provided by the present invention.

[0040] The realization of the purpose of the present invention, functional features and advantages will be further described with reference to the embodiments and the drawings. Specific embodiments

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0042] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0043] In addition, if there are descriptions such as "first", "second", etc. involved in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0044] With the development and utilization of urban underground space, the shield tunneling construction technology has been widely applied. As one of the key links in shield tunnel construction, the construction quality of the shield well end directly affects the safety and service life of the tunnel project. At present, the reinforcement of the shield well end mainly adopts a reinforced concrete structure. By setting up a steel mesh around the end and pouring high-strength concrete, a solid whole is formed. However, the shield well end is prone to deformation due to uneven settlement after reinforcement.

[0045] To solve this technical problem, the present invention proposes a method for reinforcing the shield well end.

[0046] Please refer to Figure 1 , in an embodiment of the present invention, the method for reinforcing the shield well end includes:

[0047] Step S10, arranging a shield well enclosure structure on the inner wall of the shield well along the circumferential direction of the shield well end;

[0048] Step S20, arranging a plurality of outer wrapped plain walls on the outside of the shield well along the circumferential direction of the shield well end at the large mileage end and the small mileage end of the shield well respectively; wherein, each of the outer wrapped plain walls penetrates the sand layer at the bottom of the shield well from top to bottom and extends into the strongly weathered layer below the sand layer, and the length of each outer wrapped plain wall extending into the strongly weathered layer is at least 1 m;

[0049] Step S30, arranging a triaxial mixing pile between the outer wrapped plain wall and the shield well;

[0050] Step S40, connecting the triaxial mixing pile with the shield well enclosure structure and strengthening the interface at the connection between the triaxial mixing pile and the shield well enclosure structure;

[0051] Step S50, obtaining a reinforced body and completing the reinforcement of the shield well end.

[0052] Specifically, in step S10, the enclosure structure is mainly composed of a reinforced concrete structure, such as a reinforced concrete retaining wall or a reinforced concrete segment, etc. The layout range of the enclosure structure generally needs to cover the entire reinforcement area of the shield well end and extend appropriately to both sides to ensure good connection with the surrounding soil mass. Such a setting can effectively improve the overall stability and bearing capacity of the structure and ensure the structural safety of the shield well end during construction and operation.

[0053] In step S20, the outer wrapped plain wall is cast with C20 concrete and has a thickness of 800 mm, which is sufficient to ensure the strength and stiffness of the wall. The bottom burial depth of the outer wrapped plain wall is required to penetrate the sand layer around the shield well and enter the strongly weathered layer below by at least 1 m to ensure the stability of the wall. It can effectively prevent the soil mass at the shield well end from generating excessive displacement and deformation under stress and improve the overall anti-deformation ability.

[0054] In step S30, the triple-axis mixing pile is an in-situ soil improvement technique. By drilling holes, grouting, and mixing in the soil, the soil is mixed with cement slurry to form a high-strength cement-soil pile, which plays a role in strengthening the foundation. It can significantly improve the bearing capacity and stability of the soil, reduce the settlement and deformation of the end of the shield shaft, thereby enhancing the overall safety of the project.

[0055] In step S40, the overall stability and deformation resistance of the structure are further improved. It ensures the tight combination between the reinforced structures and effectively integrates each reinforced part into a solid whole.

[0056] In step S50, through the above steps, the soil strength and stiffness of the reinforced shield shaft end are significantly improved, which can effectively limit the ground loss and deformation, reduce the stress release and displacement transfer of the surrounding soil, thereby controlling the surface settlement and building deformation within the allowable range and avoiding the damage to existing buildings and municipal facilities during construction.

[0057] In the technical solution provided by the present invention, through the combined reinforcement measures of arranging a retaining structure, an outer plain wall, and triple-axis mixing piles around the shield shaft end, the overall stability and bearing capacity of the shield shaft end can be effectively improved, and each reinforced part is integrated into a solid whole through interface reinforcement, thereby effectively limiting the ground loss and deformation and controlling the surface settlement and building deformation within the allowable range. It not only solves the problem of deformation caused by uneven settlement of the shield shaft end, but also has the advantages of simple construction technology, high mechanization degree, fast construction progress, relatively low cost, etc. It is applicable to various soil conditions, especially the silty soft soil layer, and has wide applicability.

[0058] In the embodiment of the present invention, the steps of arranging triple-axis mixing piles between the outer plain wall and the shield shaft include:

[0059] Step S31, using a triple-tube jet grouting rig to drill holes vertically downward from the ground between the outer plain wall and the shield shaft to penetrate the sand layer and the strongly weathered layer and extend to the bottom of the consolidated silty clay layer below the strongly weathered layer to form pile holes;

[0060] Step S32, pouring the pile holes to form the triple-axis mixing piles.

[0061] Specifically, in step S31, a triple-tube jet grouting rig is first used to drill holes downward from the ground between the outside of the shield well end and the outer plain wall. The purpose of drilling is to form pile holes for subsequent pouring of the three-axis mixing piles. The diameter of the pile holes is 850 mm, and the pile spacing is 600 mm. The drilling depth needs to reach about 5.1 m below the bottom of the tunnel and ensure penetration of the sand layer under the tunnel body and enter the consolidated silt clay layer in the underlying layer until the bottom of this layer. This is to ensure that the three-axis mixing piles can effectively reinforce the soil layer at the shield well end and below it, improving the stability and bearing capacity of the soil mass.

[0062] In step S32, the pouring operation of the pile holes is carried out to form the three-axis mixing piles. The three-axis mixing piles are formed by mixing cement slurry with the in-situ soil mass to form high-strength cement-soil piles, thereby enhancing the overall stability of the soil mass. The longitudinal span of the three-axis mixing piles in the shield tunnel is 12 m, and transversely, it is required to extend 3 m beyond the tunnel side line to ensure full coverage of the reinforcement range, which helps to provide a wider support and reinforcement effect.

[0063] In the embodiment of the present invention, the step of pouring the pile holes to form the three-axis mixing piles includes:

[0064] Step S321, start the mixing head on the triple-tube jet grouting rig, lift it upward from the bottom of the hole, and continue grouting and mixing simultaneously until the mixing head is lifted to the ground.

[0065] It should be noted that the triple-tube jet grouting rig is a prior art.

[0066] Specifically, several mixing paddles are provided on the mixing head, which can repeatedly mix the cement slurry and the soil mass during rotation to form a uniform cement-soil column. The lifting speed should be matched with the grouting volume and the mixing speed to ensure the continuity and uniformity of the cement-soil column. Then, move the rig to the next pile position and repeat the above processes of drilling, grouting, and mixing until the construction of all the mixing piles is completed. The three-axis mixing piles formed by this step can effectively enhance the stability of the soil mass at the shield well end and the surrounding area, reduce the deformation caused by uneven settlement, and thus improve the safety and reliability of the overall structure.

[0067] In the embodiment of the present invention, the step of connecting the three-axis mixing piles to the shield well retaining structure and strengthening the interface at the connection between the three-axis mixing piles and the shield well retaining structure includes:

[0068] Step S41, connect the three-axis mixing piles to the shield well retaining structure;

[0069] Step S42, arrange triple-tube jet grouting piles at the connection between the three-axis mixing piles and the shield well retaining structure to strengthen the interface at the connection between the three-axis mixing piles and the shield well retaining structure.

[0070] Specifically, in step S41, the connection between the triple-axis mixing pile and the shield well retaining structure is first carried out. In this step, the bottom of the triple-axis mixing pile contacts the bottom of the shield well retaining structure to ensure the butt joint of the mixing pile and the retaining structure to ensure the structural integrity between the two, thereby maximizing its structural support effect.

[0071] In step S42, the triple-tube jet grouting rig not only cuts and stirs the soil mass by high-pressure jetting of cement slurry, but also forms a cement-soil pile, effectively filling the gap between the pile and the wall. The integrity of the structure is enhanced, and its anti-deformation and compressive resistance are improved.

[0072] In the embodiment of the present invention, the steps of arranging triple-tube jet grouting piles at the connection between the triple-axis mixing pile and the shield well retaining structure to reinforce the interface between the triple-axis mixing pile and the shield well retaining structure include:

[0073] Step S421: Use a triple-tube jet grouting rig to drill holes downward from the ground at the connection between the triple-axis mixing pile and the shield well retaining structure;

[0074] Step S422: During the drilling process of the triple-tube jet grouting rig, inject cement slurry into the bottom of the hole through the outer pipe of the drill rod of the triple-tube jet grouting rig at a grouting pressure of 20 MPa to 30 MPa, inject compressed air into the bottom of the hole through the middle pipe of the drill rod of the triple-tube jet grouting rig at an air pressure of 0.8 MPa to 1.2 MPa, and inject water into the bottom of the hole through the inner pipe of the drill rod of the triple-tube jet grouting rig at a water pressure of 30 MPa to 50 MPa to form a cement-soil column;

[0075] Step S423: Repeat the above steps to arrange three cement-soil columns with a diameter of 800 mm and a spacing of 600 mm at the connection of the shield well retaining structure to form the triple-tube jet grouting pile to reinforce the interface between the triple-axis mixing pile and the shield well retaining structure.

[0076] Specifically, in step S421, a triple-tube jet grouting rig is used to drill holes downward from the ground at the connection between the triple-axis mixing pile and the shield well retaining structure. The triple-tube jet grouting rig transports high-pressure cement slurry, high-pressure water, and high-pressure gas through three concentric pipes respectively to form a high-speed rotating grouting jet in the soil mass. This jet can effectively cut and stir the soil mass, providing a construction basis for subsequent grouting operations.

[0077] In step S422, during the drilling process, cement slurry is injected into the bottom of the hole through the outer pipe of the triple-tube jet grouting rig at a grouting pressure of 20 MPa to 30 MPa. At the same time, compressed air is injected into the bottom of the hole through the middle pipe at an air pressure of 0.8 MPa to 1.2 MPa, and water is injected into the bottom of the hole through the inner pipe at a water pressure of 30 MPa to 50 MPa. Such high-pressure injection can form a solid cement-soil column, effectively filling and strengthening the joint.

[0078] In step S423, the above steps are repeated to arrange three cement-soil columns with a diameter of 800 mm and a spacing of 600 mm to form triple-tube jet grouting piles. These piles not only provide physical support but also enhance the interface strength between the three-axis mixing pile and the shield well retaining structure through the filling of cement slurry therebetween, thus greatly improving the stability and deformation resistance of the overall structure.

[0079] It should be understood that in this embodiment, by arranging triple-tube jet grouting piles at the joint between the three-axis mixing pile and the shield well retaining structure, the structural stability and durability of the shield well end are effectively improved. It not only ensures the sealing and strength of the interface but also improves the construction efficiency and safety.

[0080] In the embodiment of the present invention, after the step of obtaining the reinforced body and completing the reinforcement of the shield well end, the shield well end reinforcement method further includes:

[0081] Step S60, drilling core samples from the reinforced body;

[0082] Step S70, testing the core samples to obtain test results;

[0083] Step S80, judging whether the test results meet the preset conditions;

[0084] Step S90, if not, then reinforce or re-reinforce the shield well end.

[0085] Specifically, in step S60, within 28 days after the hardening of the reinforced body, a core drill is used to drill core samples on the reinforced body. The core-taking positions should be evenly distributed to cover the entire reinforcement range, and at least 3 core samples should be drilled for each reinforced body. Ensure that representative samples are obtained from different positions and depths for a comprehensive quality assessment.

[0086] In step S70, the obtained core samples are tested to obtain test results. The test contents include but are not limited to compressive strength, density, and material uniformity.

[0087] In step S80, ensure the stability and durability of the reinforced structure according to the test results.

[0088] In step S90, if the test result does not meet the preset conditions, reinforcement or re - reinforcement is carried out. The reinforcement measures may include adding reinforcement materials, adjusting the reinforcement structure or adopting new reinforcement technologies. Ensure that all non - compliant areas can be repaired to meet the requirements of the overall project quality.

[0089] In an embodiment of the present invention, the step of drilling core samples from the solidified body includes:

[0090] Step S61, drilling core samples of the solidified body within 28 days after construction is completed; the number of the core samples is not less than 3, the diameter of the core samples is greater than or equal to 100 mm, and the length of the core samples is greater than or equal to 1000 mm.

[0091] Specifically, within 28 days after the solidified body is hardened, existing double - tube core - drilling equipment is used to drill core samples of the solidified body. The double - tube core - drilling equipment uses both an inner tube and an outer tube during drilling. The inner tube is used to store the core, and the outer tube is used to protect the hole wall to prevent cave - in. This effectively protects the obtained core samples and avoids damaging or contaminating the samples during the sampling process.

[0092] The number of core samples is not less than 3 to ensure the representativeness and statistical significance of the sampling. The diameter of each core sample is greater than or equal to 100 mm, and the length is greater than or equal to 1000 mm to reflect the overall quality and uniformity of the solidified body.

[0093] In an embodiment of the present invention, the step of testing the core samples to obtain the test result includes:

[0094] Step S71, under the condition of no lateral constraint, squeezing each of the core samples respectively to obtain the maximum axial compressive stress that each of the core samples can withstand;

[0095] Step S72, obtaining the overall strength evaluation value of the solidified body according to the maximum axial compressive stress, and taking the overall strength evaluation value as the test result.

[0096] Specifically, in step S71, the drilled core samples will be subjected to a squeezing test under the condition of no lateral constraint to obtain the maximum axial compressive stress that each of the core samples can withstand. This simulates the most extreme pressure conditions that may be encountered in the actual project to ensure that the measured data can truly reflect the compressive capacity of the solidified body.

[0097] In step S72, according to the maximum axial compressive stress obtained from step S71, calculate the overall strength evaluation value of the solidified body. The overall strength evaluation value is the arithmetic mean of the maximum axial compressive stresses of all core samples. This can more accurately evaluate the compressive performance of the solidified body and ensure the safety and reliability of the solidified body at the end of the shield shaft.

[0098] In an embodiment of the present invention, the step of determining whether the detection result meets a preset condition includes:

[0099] Step S81, determining whether the overall strength evaluation value is greater than or equal to 1.0 MPa;

[0100] Step S82, if not, then it does not meet the preset condition; if so, then it meets the preset condition.

[0101] Specifically, in step S81, after completing the strength test of the core sample of the reinforced body, the obtained overall strength evaluation value is compared with 1.0 MPa to ensure that the reinforced body can withstand the maximum load that may be encountered.

[0102] In step S82, if the overall strength evaluation value is less than 1.0 MPa, it is determined that the preset condition is not met, and reinforcement measures or re-reinforcement are required. If the overall strength evaluation value is greater than or equal to 1.0 MPa, it is determined that the preset condition is met, and the reinforcement construction is successful, and subsequent construction steps can be carried out.

[0103] In an embodiment of the present invention, if not, the steps of reinforcing or re-reinforcing the end of the shield shaft include:

[0104] Step S91, if the detection result does not meet the preset condition, the end of the shield shaft is reinforced or re-reinforced by means of grouting and / or jet grouting.

[0105] Specifically, in step S91, after completing the strength test of the core sample of the reinforced body, if the detection result does not meet the preset condition (for example, the overall strength evaluation value does not reach 1.0 MPa), reinforcement or re-reinforcement measures are taken. The reinforcement methods include but are not limited to grouting and jet grouting techniques to improve the structural strength and stability of the reinforced body.

[0106] More specifically, the grouting method refers to injecting cement slurry into the voids or cracks in the reinforced body to fill the voids and increase the density of the structure. The jet grouting method is to mix the soil and cement slurry by high-pressure rotary jetting of cement slurry to form a stronger reinforced body.

[0107] The above is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for reinforcing the end of a shield shaft, characterized in that Including: A shield well retaining structure is arranged on the inner wall of the shield well along the circumferential direction of the end of the shield well; A plurality of outer wrapped plain walls are arranged on the outer side of the shield well along the circumferential direction of the end of the shield well at the large mileage end and the small mileage end of the shield well respectively; wherein, each of the outer wrapped plain walls penetrates the sand layer at the bottom of the shield well from top to bottom and extends into the strongly weathered layer below the sand layer, and the length of each of the outer wrapped plain walls extending into the strongly weathered layer is at least 1 m; Three-axis mixing piles are arranged between the outer wrapped plain walls and the shield well; Connect the three-axis mixing piles with the shield well retaining structure, and reinforce the interface at the connection between the three-axis mixing piles and the shield well retaining structure; Obtain a reinforced body and complete the reinforcement of the end of the shield well.

2. The shield well end reinforcement method according to claim 1, wherein The step of arranging three-axis mixing piles between the outer wrapped plain walls and the shield well includes: Using a triple-tube jet grouting rig, drill holes downward from the ground between the outer wrapped plain walls and the shield well to penetrate the sand layer and the strongly weathered layer, and extend to the bottom of the consolidated silt clay layer below the strongly weathered layer to form pile holes; Pour the pile holes to form the three-axis mixing piles.

3. The shield well end reinforcement method according to claim 2, characterized in that, The step of pouring the pile holes to form the three-axis mixing piles includes: Start the mixing head on the triple-tube jet grouting rig, lift it upward from the bottom of the hole, and continue grouting and mixing at the same time until the mixing head is lifted to the ground.

4. The shield well end reinforcement method according to claim 3, wherein, The step of connecting the three-axis mixing piles with the shield well retaining structure and reinforcing the interface at the connection between the three-axis mixing piles and the shield well retaining structure includes: Connect the three-axis mixing piles with the shield well retaining structure; Arrange triple-tube jet grouting piles at the connection between the three-axis mixing piles and the shield well retaining structure to reinforce the interface at the connection between the three-axis mixing piles and the shield well retaining structure.

5. The shield well end reinforcement method according to claim 4, characterized in that, The step of arranging triple-tube jet grouting piles at the connection between the three-axis mixing piles and the shield well retaining structure to reinforce the interface at the connection between the three-axis mixing piles and the shield well retaining structure includes: Using a triple-tube jet grouting rig, drill holes downward from the ground at the connection between the three-axis mixing piles and the shield well retaining structure; During the drilling process of the triple-tube jet grouting rig, inject cement slurry into the bottom of the hole at a grouting pressure of 20 MPa to 30 MPa through the outer pipe of the drill rod of the triple-tube jet grouting rig, inject compressed air into the bottom of the hole at an air pressure of 0.8 MPa to 1.2 MPa through the middle pipe of the drill rod of the triple-tube jet grouting rig, and inject water into the bottom of the hole at a water pressure of 30 MPa to 50 MPa through the inner pipe of the drill rod of the triple-tube jet grouting rig to form a cement-soil column; Repeat the above steps, arrange three cement-soil columns with a diameter of 800 mm and a spacing of 600 mm at the connection of the shield well retaining structure to form the triple-tube jet grouting piles to reinforce the interface at the connection between the three-axis mixing piles and the shield well retaining structure.

6. The shield well end reinforcement method according to any one of claims 1 to 5, characterized in that, After the step of obtaining a reinforced body and completing the reinforcement of the end of the shield well, the shield well end reinforcement method further includes: Drill core samples from the reinforced body; Test the core samples to obtain test results; Judge whether the test results meet the preset conditions; If not, reinforce or re - reinforce the end of the shield shaft.

7. The shield well end reinforcement method according to claim 6, wherein, The steps of drilling core samples from the solidified body include: Drilling core samples of the solidified body within 28 days after construction completion; the number of the core samples is not less than 3, the diameter of the core samples is greater than or equal to 100 mm, and the length of the core samples is greater than or equal to 1000 mm.

8. The shield well end reinforcement method according to claim 7, characterized in that The steps of testing the core samples to obtain test results include: Under the condition of no lateral restraint, squeezing each of the core samples respectively to obtain the maximum axial compressive stress that each core sample can withstand; Obtaining the overall strength evaluation value of the solidified body according to the maximum axial compressive stress, and taking the overall strength evaluation value as the test result.

9. The method for strengthening the end of a shield well according to claim 8, wherein The steps of judging whether the test result meets the preset conditions include: Judging whether the overall strength evaluation value is greater than or equal to 1.0 MPa; If not, it does not meet the preset conditions; if so, it meets the preset conditions.

10. The method for strengthening the end of a shield shaft according to claim 9, characterized in that, If not, the steps of reinforcing or re - reinforcing the end of the shield shaft include: If the test result does not meet the preset conditions, reinforce or re - reinforce the end of the shield shaft by means of grouting and / or jet grouting.

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