Construction method and formwork structure of underground continuous wall based on CFRP-ECC

Abstract

The application discloses a CFRP-ECC-based underground continuous wall construction method and a formwork structure, and belongs to the technical field of underground engineering construction. The method adopts a CFRP-ECC formwork structure, obtains the rock stratum and the lateral pressure of concrete pouring, and takes the greater value as the most unfavorable load, and according to the most unfavorable load, the maximum bending moment and the bending bearing capacity of the stress section of the formwork structure are calculated, and the size parameters of the formwork structure are determined by taking the bearing capacity being not less than the maximum bending moment as a constraint; the CFRP grid is laid into a mold and fixed connectors, ECC material is poured, and the formwork structure is obtained after curing and demolding; the formwork structure is hoisted and placed into a groove section as an outer side permanent formwork, a reinforcement cage is hoisted and placed and fixed through the connectors and the CFRP grid, and finally, concrete is poured and cured to complete the construction. The CFRP-ECC-based underground continuous wall construction method and the formwork structure provided by the application do not need to be dismantled, and the construction efficiency and the crack resistance and corrosion resistance of the continuous wall are improved.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering construction technology, and in particular relates to a construction method and formwork structure for underground continuous walls based on CFRP-ECC. Background Technology

[0002] As the core support and load-bearing structure of basement projects, the construction efficiency and long-term structural performance of diaphragm walls directly affect the safety and construction benefits of the project. Traditional diaphragm wall construction often uses steel or wooden formwork, which has significant drawbacks: after construction, additional dismantling procedures are required, which are cumbersome, time-consuming, and labor-intensive, significantly reducing overall construction efficiency. Furthermore, the diaphragm wall itself is constantly exposed to a humid or water-pressure environment, making it prone to cracking due to concrete shrinkage and load stress. Moisture seeping into these cracks accelerates concrete carbonation and steel corrosion, further weakening the structure's long-term load-bearing capacity.

[0003] In recent years, ECC (engineering cement-based composite material) has gradually gained attention in the construction engineering field due to its excellent crack resistance and toughness. However, its application as the outer formwork of diaphragm walls is unprecedented and remains a technological gap. On the one hand, it is impossible to accurately predict the actual effects of complex loads such as the lateral pressure of soil and rock and the lateral pressure of newly poured concrete that the ECC formwork will have to withstand throughout the construction process. On the other hand, there is a lack of mature calculation systems to integrate these loads and determine the most unfavorable stress conditions. The ambiguity of load parameters directly leads to the inability to scientifically design key structural parameters such as the thickness of the ECC formwork and the strip width, thickness, and spacing of the matching CFRP (carbon fiber reinforced composite) grid. Therefore, insufficient load-bearing capacity may lead to safety risks, while over-design may result in material waste and increased costs. Both of these limitations restrict the synergistic effect of ECC's crack resistance and CFRP's high strength characteristics, hindering the upgrading and optimization of diaphragm wall construction technology. Summary of the Invention

[0004] In view of the shortcomings of the related technologies, the purpose of this invention is to provide a construction method and formwork structure for underground continuous walls based on CFRP-ECC, so as to solve the problems mentioned in the background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for constructing diaphragm walls based on CFRP-ECC is disclosed, employing a CFRP-ECC formwork structure. The CFRP-ECC formwork structure includes ECC precast panels, CFRP grids, and connectors. The diaphragm wall construction method includes the following steps:

[0007] S1. Obtain the lateral pressure of the rock stratum and the lateral pressure of the concrete pouring, and take the larger value of the lateral pressure of the rock stratum and the lateral pressure of the concrete pouring as the most unfavorable load.

[0008] S2. Calculate the maximum bending moment of the stressed section of the CFRP-ECC template structure based on the most unfavorable load;

[0009] S3. Calculate the bending capacity of the stressed section of the CFRP-ECC template structure. With the bending capacity of the stressed section not being less than the maximum bending moment of the stressed section as a constraint, determine the thickness of the ECC precast slab, the strip width, thickness and spacing of the CFRP grid.

[0010] S4. Lay the CFRP grid into the mold, fix the connectors at the nodes of the CFRP grid, pour ECC material to embed the CFRP grid and connectors, cure until the preset strength is reached to form the ECC precast panel, and then demold to obtain the CFRP-ECC template structure.

[0011] S5. After constructing the guide wall, excavate the trench section and hoist the CFRP-ECC formwork structure into the trench section to serve as the outer permanent formwork.

[0012] S6. Hoist the steel cage to the concrete pouring side of the CFRP-ECC formwork structure and fix the steel cage to the CFRP grid with connectors to form a force transmission path.

[0013] S7. Pour concrete into the trench section and cure it to complete the construction of the underground continuous wall.

[0014] In some embodiments, the constraint relationship that the bending capacity of the stressed section is not less than the maximum bending moment of the stressed section in step S3 is verified by the following formula:

[0015]

[0016]

[0017] in, The maximum bending moment of the stressed section of the CFRP-ECC template structure. The bending capacity of the stressed section. This is the equivalent compression zone height coefficient of the stressed section. The effective height of the stressed section. The height of the pressure zone. For the tensile stress of the CFRP grid, The cross-sectional area of ​​the tension zone of the CFRP grid is... This is the design value for the axial tensile crack strength of the ECC. Width of the stressed section This refers to the thickness of the ECC precast panel.

[0018] In some embodiments, in step S3, the thickness of the ECC precast panel, the strip width, thickness, and spacing of the CFRP grid are determined by the following formula:

[0019]

[0020]

[0021] in, For the thickness of the CFRP grid strip, The width of the CFRP grid strip. The strip spacing of the CFRP grid. The coefficients are the equivalent rectangular stress curves of the compression zone. This is the design value for the axial compressive strength of the ECC shaft.

[0022] Preset ECC precast panel thickness CFRP grid strip thickness CFRP grid strip width Spacing between CFRP grid strips The thickness of the ECC precast panel, the strip width, thickness, and spacing of the CFRP grid are determined according to the formula.

[0023] In some embodiments, the specific steps for determining the thickness of the ECC precast panel, the strip width, thickness, and spacing of the CFRP grid are as follows:

[0024] Preset ECC precast panel thickness The cross-sectional area of ​​the tension zone of the CFRP grid is determined according to the formula. ;

[0025] If no solution is found, adjust the thickness of the ECC precast slab. And recalculate;

[0026] If a solution exists, then preset the strip width, thickness, and spacing of the CFRP grid, and calculate the flexural bearing capacity of the stressed section. ,like Then adjust the strip width, thickness, and spacing of the CFRP grid until... Finally, the thickness of the ECC precast panel, the strip width, thickness, and spacing of the CFRP grid were determined.

[0027] In some embodiments, in step S4, a preset distance is reserved between the CFRP grid and the concrete pouring side surface of the ECC precast slab, so that the CFRP grid is located near the edge of the tension zone to fully utilize its tensile properties; and the connector is partially exposed on the concrete pouring side surface of the ECC precast slab for subsequent connection with the reinforcing cage to form a force transmission path.

[0028] In some embodiments, in step S1, the lateral pressure of the rock strata includes the earth pressure and water pressure exerted by the rock strata on the CFRP-ECC template structure; wherein the earth pressure is the maximum active earth pressure or the maximum passive earth pressure determined according to the characteristics of the rock strata.

[0029] A CFRP-ECC-based formwork structure is applied to the CFRP-ECC-based diaphragm wall construction method described above. The CFRP-ECC formwork structure includes:

[0030] ECC precast panels;

[0031] CFRP grating is embedded in ECC precast slabs with a pre-set distance between it and the concrete pouring side surface of the ECC precast slabs, so that the CFRP grating is located near the edge of the tension zone to fully exert its tensile properties.

[0032] The connector is fixed at the node of the CFRP grid and partially exposed on the concrete pouring side surface of the ECC precast slab to form a force transmission path for subsequent connection with the reinforcing cage.

[0033] In some embodiments, the connector includes:

[0034] The first connecting part includes a vertical anti-pull base and a flipping member; the flipping member is rotatably connected to the vertical anti-pull base, the vertical anti-pull base is provided with a snap-fit ​​hole, and the flipping member is provided with a snap-fit ​​protrusion adapted to the snap-fit ​​hole; a clamping space for accommodating the nodes of the CFRP grid is formed between the vertical anti-pull base and the flipping member, and the two are clamped and fixed by the snap-fit ​​engagement of the snap-fit ​​protrusion and the snap-fit ​​hole;

[0035] The second connecting part is connected to the vertical anti-pull base of the first connecting part through a connecting rod; the second connecting part includes a U-shaped structure with a connecting hole, a bolt and a nut adapted to the connecting hole; the mating structure of the bolt and nut is used to clamp and fix the reinforcing bars of the reinforcing cage in the clamping space of the U-shaped structure.

[0036] In some embodiments, the connector further includes a first reinforcing member disposed at the connection between the second connecting portion and the connecting rod.

[0037] In some embodiments, the connector further includes a plurality of second reinforcing members, which are evenly spaced along the circumferential direction of the connecting rod. Each second reinforcing member is fixedly connected at one end to a first reinforcing member and at the other end to a vertical anti-pull-out base.

[0038] In some embodiments, the connecting hole is an elongated connecting hole, the length direction of which is consistent with the opening direction of the U-shaped structure, and the length dimension of the elongated connecting hole is greater than the diameter of the bolt, so that the mating structure of the bolt and nut can move within the elongated connecting hole to accommodate and clamp the reinforcing bars of different diameter steel cages.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. The CFRP-ECC-based diaphragm wall construction method provided by this invention determines the ECC precast slab thickness and key parameters of the CFRP grid by accurately calculating the most unfavorable load, maximum bending moment and flexural bearing capacity, ensuring that the template size is adapted to the stress requirements; the customized CFRP-ECC template structure is used as the outer permanent template, which does not need to be removed and forms an integral part with the wall, thus saving the demolition process, shortening the construction period, and improving the long-term stability of the wall by leveraging material properties and precise design, thereby achieving a dual optimization of construction economy and structural reliability.

[0041] 2. The CFRP-ECC-based diaphragm wall construction method provided by this invention fully utilizes the tensile strength advantage of CFRP material by pre-embedding CFRP grids at the edge of the tension zone of ECC precast slabs, thereby significantly improving the load-bearing capacity and durability of the diaphragm wall support structure. The prefabricated construction method with pre-embedded connectors simplifies on-site assembly procedures, shortens the construction cycle, and ensures a stable and reliable force transmission path, effectively reducing the safety risks and cost of underground construction.

[0042] 3. In the CFRP-ECC-based template structure provided by this invention, the connector adopts a snap-fit ​​design of vertical anti-pull base and flip-over component, which can firmly clamp the CFRP grid node, and strengthen the connection rigidity with circumferential and vertical reinforcement components; the elongated connecting hole of the second connection part allows for fine adjustment of bolt position, adapting to different diameter steel cages, and the CFRP-ECC template structure as a whole can be precisely matched with the underground continuous wall construction method, which is convenient to install, has a high reusability, and significantly improves the adaptability and reliability of underground continuous wall construction. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0044] Figure 1 This is a flowchart illustrating an embodiment of the underground continuous wall construction method and formwork structure based on CFRP-ECC of the present invention.

[0045] Figure 2This is a schematic diagram of a CFRP-ECC template structure, representing an embodiment of the CFRP-ECC-based underground continuous wall construction method and template structure of the present invention.

[0046] Figure 3 This is a schematic diagram of the connector structure of an embodiment of the underground continuous wall construction method and formwork structure based on CFRP-ECC of the present invention;

[0047] Figure 4 This is a schematic diagram showing the connection between the connector, CFRP grid, and reinforcing bars in one embodiment of the underground continuous wall construction method and formwork structure based on CFRP-ECC of the present invention.

[0048] Figure 5 This is a schematic diagram of an excavation section of an embodiment of the CFRP-ECC-based underground continuous wall construction method and formwork structure of the present invention;

[0049] Figure 6 This is a schematic diagram of a CFRP-ECC formwork structure for hoisting a CFRP-ECC formwork structure, representing an embodiment of the CFRP-ECC-based underground continuous wall construction method and formwork structure of the present invention.

[0050] Figure 7 This is a schematic diagram of the hoisting of a steel reinforcement cage, representing an embodiment of the CFRP-ECC-based underground continuous wall construction method and formwork structure of the present invention.

[0051] Figure 8 This is a schematic diagram of concrete pouring in an embodiment of the underground continuous wall construction method and formwork structure based on CFRP-ECC of the present invention.

[0052] Figure 9 This is a schematic diagram illustrating the completion of a diaphragm wall construction method and formwork structure based on CFRP-ECC, according to an embodiment of the present invention.

[0053] In the picture:

[0054] 1. CFRP-ECC formwork structure; 11. ECC precast slab; 12. CFRP grid; 13. Connectors;

[0055] 131. First connecting part; 132. Second connecting part; 133. Connecting rod; 134. First reinforcing member; 135. Second reinforcing member;

[0056] 1311. Vertical anti-pull-out base; 1312. Snap-fit ​​hole; 1313. Flip-over part; 1314. Snap-fit ​​protrusion;

[0057] 1321. U-shaped structure; 1322. Connecting hole; 1323. Bolt; 1324. Nut;

[0058] 2. Trench section; 3. Reinforcing cage; 31. Reinforcing bar; 4. Rock strata; 5. Concrete. Detailed Implementation

[0059] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0060] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0061] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] Example 1:

[0063] See appendix Figures 1 to 9 This paper presents an illustrative embodiment of the CFRP-ECC-based diaphragm wall construction method proposed in this invention. The method employs a CFRP-ECC template structure 1, which includes an ECC precast panel 11, a CFRP grid 12, and connectors 13. The CFRP-ECC-based diaphragm wall construction method includes the following steps:

[0064] S1. Obtain the lateral pressure of the rock stratum and the lateral pressure of the concrete pouring, and take the larger value of the lateral pressure of the rock stratum and the lateral pressure of the concrete pouring as the most unfavorable load.

[0065] S2. Calculate the maximum bending moment of the stressed section of CFRP-ECC formwork structure 1 based on the most unfavorable load.

[0066] S3. Calculate the bending capacity of the CFRP-ECC template structure 1. With the bending capacity of the CFRP-ECC template structure 1 not being less than the maximum bending moment of the CFRP-ECC template structure 1 as a constraint, determine the thickness of the ECC precast slab 11 and the strip width, thickness and spacing of the CFRP grid 12.

[0067] S4. Lay the CFRP grid 12 into the mold, fix the connector 13 at the node of the CFRP grid 12, pour ECC material to embed the CFRP grid 12 and connector 13, cure to the preset strength to form the ECC precast panel 11 and then demold to obtain the CFRP-ECC template structure 1.

[0068] S5. After constructing the guide wall, excavate trench section 2 and hoist CFRP-ECC template structure 1 into trench section 2 to serve as the outer permanent template.

[0069] S6. Hoist the steel cage 3 to the concrete pouring side of the CFRP-ECC formwork structure 1, and fix the steel cage 3 to the CFRP grid 12 through the connector 13 to form a force transmission path.

[0070] S7. Pour concrete 5 into section 2 of the trench and cure it to complete the construction of the underground continuous wall.

[0071] In step S1, the concrete pouring side refers to the side of the CFRP-ECC formwork structure 1 facing the interior of the trench section 2 (i.e., the back soil surface), which bears the lateral pressure of the newly poured concrete 5 during the construction phase; the rock stratum side refers to the side of the CFRP-ECC formwork structure 1 facing the rock stratum 4 outside the foundation pit (i.e., the soil-facing surface), which bears the soil and water pressure of the rock stratum. Specifically, the rock stratum lateral pressure includes the soil pressure and water pressure exerted by the rock stratum 4 on the CFRP-ECC formwork structure 1; the soil pressure is the maximum active earth pressure or the maximum passive earth pressure determined based on the characteristics of the rock stratum 4. The calculation of the rock stratum lateral pressure is based on the superposition of soil pressure and water pressure. The type of soil pressure is determined as the maximum active earth pressure or the maximum passive earth pressure according to the geological survey report of the rock stratum 4 where the project is located. If other environmental lateral loads exist, such as local collapse impact forces, they can be added according to relevant engineering specifications. Finally, the larger value of the rock stratum lateral pressure and the concrete pouring lateral pressure is taken as the most unfavorable load.

[0072] When using an internal vibrator for concrete pouring, the lateral pressure of the concrete is calculated using the following formula, and the smaller value of the two formulas is taken:

[0073]

[0074]

[0075] in, The maximum lateral pressure of newly poured concrete on the formwork ; The density of concrete ; For the speed of concrete pouring ; Initial setting time of freshly poured concrete It can be determined by experimentation; when experimental data is lacking, alternative methods can be used. calculate( The temperature of concrete ); The correction factor for the effect of admixtures is 1.0 (1.0 when no admixtures are added, and 1.2 when admixtures with retarding effect are added). The correction factor for the effect of concrete slump is (0.85 when the slump is less than 30 mm, 1.00 when the slump is 50-90 mm, and 1.15 when the slump is 110-150 mm). The total height from the location where the lateral pressure of the concrete is calculated to the top surface of the newly poured concrete. Effective pressure head height .

[0076] In step S3, the constraint relationship that the flexural bearing capacity of the stressed section is not less than the maximum bending moment of the stressed section is verified by the following formula:

[0077]

[0078]

[0079] in, The maximum bending moment of the stressed section of CFRP-ECC template structure 1 , Bending capacity of the stressed section , This is the equivalent compression zone height coefficient of the stressed section. Effective height of the stressed section , Height of the pressure zone , Tensile stress of CFRP grid 12 , The cross-sectional area of ​​the tension zone of CFRP grid 12 , Design value of ECC axial tensile crack strength , Width of the stressed section , ECC precast panel thickness 11 According to the "Technical Specification for Strain-Hardening Cement-Based Composite Structures" (T / CECS 1212-2022), in this embodiment, The value is 0.8095.

[0080] In addition, the following formulas should be used to complete the parameter verification and determination:

[0081]

[0082]

[0083]

[0084]

[0085] in, This is the limit reinforcement ratio; This refers to the relative height of the limit pressure zone; The elastic modulus of the CFRP grid; For the tensile strain of the CFRP grid; (Tensile stress of CFRP grid,) ); The ultimate compressive strain of ECC under non-uniform compression; The design value of CFRP tensile strength ( ); Design value of ECC axial compressive strength ( ); This represents the actual reinforcement ratio; the definitions of other parameters are the same as before.

[0086] In this embodiment, the thickness of the ECC precast panel 11 is the same as the thickness of the CFRP-ECC template structure 1. Since the CFRP grid 12 is a mesh structure, its thickness is much smaller than the designed thickness of the ECC precast panel 11. Furthermore, during the prefabrication of the CFRP-ECC template structure 1, the CFRP grid 12 is completely embedded inside the ECC precast panel 11 and tightly bonded to the ECC substrate, without adding any extra to the overall thickness of the CFRP-ECC template structure 1. Therefore, the thickness of the CFRP-ECC template structure 1 is solely determined by the thickness of the ECC precast panel 11, and the CFRP grid 12 is merely a reinforcement embedded within it, without changing the overall thickness of the CFRP-ECC template structure 1.

[0087] In step S3, the thickness of the ECC precast panel 11, the strip width, thickness, and spacing of the CFRP grid 12 are determined by the following formula:

[0088]

[0089]

[0090] in, For CFRP grid with 12 strips of thickness , CFRP grid with 12 strips of width , The strip spacing of CFRP grid 12 , The coefficients are the equivalent rectangular stress curves of the compression zone. Design value of ECC axial compressive strength ( According to the "Technical Specification for Strain-Hardening Cement-Based Composite Material Structures" (T / CECS 1212-2022), in this embodiment, The value is 0.9608.

[0091] Preset ECC precast panel thickness 11 CFRP grid with 12 strips of thickness CFRP grid with 12 strips of width The strip spacing of CFRP grille 12 The thickness of the ECC precast panel 11, the strip width, thickness, and spacing of the CFRP grid 12 are determined according to the formula. The specific determination steps are as follows:

[0092] Preset ECC precast panel thickness 11 According to the formula Determine the cross-sectional area of ​​the tension zone of CFRP grid 12 ;

[0093] If there is no solution, it indicates that the thickness of the ECC precast panel is 11. If the insufficient thickness leads to an imbalance of forces, then the thickness of the ECC precast slab should be adjusted. And recalculate;

[0094] If a solution exists, then combine it with the formula. The strip width, thickness, and spacing of the CFRP grid 12 are preset, and the bending bearing capacity of the stressed section is calculated. ,like Then adjust the strip width, thickness, and spacing of the CFRP grid 12 (maintaining...) (meeting requirements), until Finally, the thickness of the ECC precast panel 11, the strip width, thickness and spacing of the CFRP grid 12 were determined.

[0095] Here, the thickness of the ECC precast panel 11 is preset and adjusted first. The reason is that: ECC precast slab 11 is the load-bearing matrix of CFRP-ECC template structure 1, and its thickness... This directly determines the effective height and compression zone range of the cross-section, forming the basis for the establishment of a cross-sectional force balance system. If the ECC precast slab has a thickness of 11... If the value is too small, even if the strip width, thickness, and other parameters of the CFRP grid 12 are set to be extremely high (i.e., the cross-sectional area of ​​the tension zone of the CFRP grid 12), it will still be insufficient. Even with extremely high reinforcement (e.g., the ECC matrix's compression zone height is insufficient, leading to an unsolvable force balance equation), the CFRP grid 12 lacks the structural support of the ECC matrix and cannot form an effective bending load-bearing system. Therefore, it is necessary to first ensure the thickness of the ECC precast slab 11. The requirement that the equation has a solution is met, and then the parameters of the CFRP grid 12 are adjusted to match the bending bearing capacity requirements.

[0096] In this embodiment, if The specific parameter adjustment is to increase the thickness of the ECC precast slab 11. Increase the thickness of 12 strips of CFRP grid Or CFRP grid with 12 strips width Or reduce the strip spacing of the CFRP grid 12. .

[0097] In step S4, the prefabrication process of CFRP-ECC template structure 1 is completed in the factory, specifically including: mold preparation → cutting CFRP grid 12 according to the design and laying it into the mold → fixing connector 13 at the nodes of CFRP grid 12 (circumferential reinforcement and vertical pull-out treatment are performed at the connection between connector 13 and CFRP grid 12 to prevent shear and tensile forces at the interface from causing connection failure) → ECC material mixing and pouring → curing to the preset strength → finished product inspection → demolding to obtain qualified CFRP-ECC template structure 1. In this embodiment, a preset distance is reserved between the CFRP grid 12 and the concrete pouring side surface of the ECC precast slab 11, so that the CFRP grid 12 is located near the edge of the tension zone to fully exert its tensile performance. In this embodiment, the preset distance is 10mm to ensure that it can effectively play a connecting and reinforcing role and facilitate subsequent welding or connection operations. The connector 13 is partially exposed on the concrete pouring side surface of the ECC precast slab 11 for subsequent connection with the reinforcing cage 3 to form a force transmission path, so as to realize the ECC precast slab 11 and the reinforcing cage 3 to share the force together.

[0098] In step S5, after excavating trench section 2, bottom cleaning and trench inspection are required to ensure that the sediment at the bottom of the trench section is cleaned up and to ensure the quality and load-bearing capacity of the wall. When hoisting and placing the CFRP-ECC formwork structure 1, it is necessary to ensure the installation accuracy of it as the outer permanent formwork and to ensure that it fits tightly against the side wall of trench section 2.

[0099] In step S7, a tremie pipe must be installed before pouring concrete 5. The pouring operation is completed by using the tremie pipe method. After pouring, the concrete is cured to the design strength according to the specifications. After the underground continuous wall is formed, the subsequent excavation of the basement main structure can be carried out. The CFRP-ECC formwork structure 1 serves as a permanent outer formwork and works together with the wall to bear the load.

[0100] In the above illustrative embodiments, the CFRP-ECC-based diaphragm wall construction method determines the ECC precast slab thickness and key parameters of the CFRP grid by accurately calculating the most unfavorable load, maximum bending moment, and flexural bearing capacity, ensuring that the template size is adapted to the stress requirements. This customized CFRP-ECC template structure is used as the outer permanent template, which does not need to be removed and forms an integral part with the wall. This not only saves the demolition process and shortens the construction period, but also improves the long-term stability of the wall by leveraging material properties and precise design, achieving a dual optimization of construction economy and structural reliability.

[0101] Example 2:

[0102] See appendix Figures 1 to 9 This paper presents an illustrative embodiment of the CFRP-ECC-based template structure proposed in this invention, which is applied to the CFRP-ECC-based diaphragm wall construction method as described in Embodiment 1. The CFRP-ECC template structure 1 includes an ECC precast panel 11, a CFRP grid 12, and a connector 13.

[0103] The CFRP grid 12 is embedded within the ECC precast slab 11, with a predetermined distance maintained between it and the concrete pouring side surface of the ECC precast slab 11. This ensures that the CFRP grid 12 is located near the edge of the tension zone to fully utilize its tensile strength. In this embodiment, the predetermined distance is 10mm to ensure that it can effectively perform its connection and reinforcement functions, and to facilitate subsequent welding or connection operations.

[0104] The connector 13 is fixed at the node of the CFRP grid 12 and partially exposed on the concrete pouring side surface of the ECC precast slab 11 to form a force transmission path for subsequent connection with the reinforcing cage 3. Due to the hydrostatic pressure and thermal shrinkage of the large volume concrete during underground construction, additional shear and tensile forces will be generated at the interface between the ECC and the concrete. Therefore, the connector 13 needs to be reinforced with special structural design to enhance the connection reliability.

[0105] The connector 13 includes a first connecting portion 131 and a second connecting portion 132. The first connecting portion 131 includes a vertical pull-out resistant base 1311 and a flipping member 1313. The vertical pull-out resistant base 1311 is in the form of a circular base, which itself constitutes vertical pull-out resistant treatment at the connection between the connector 13 and the node of the CFRP grid 12. The flipping member 1313 is rotatably connected to the vertical pull-out resistant base 1311. The vertical pull-out resistant base 1311 is provided with a snap-fit ​​hole 1312, and the flipping member 1313 is provided with a snap-fit ​​protrusion 1314 adapted to the snap-fit ​​hole 1312. A clamping space for accommodating the node of the CFRP grid 12 is formed between the vertical pull-out resistant base 1311 and the flipping member 1313, and the two are clamped and fixed by the snap-fit ​​engagement of the snap-fit ​​protrusion 1314 and the snap-fit ​​hole 1312.

[0106] The second connecting part 132 is connected to the vertical anti-pull base 1311 of the first connecting part 131 via a connecting rod 133; the second connecting part 132 includes a U-shaped structure 1321 with a connecting hole 1322, a bolt 1323 and a nut 1324 adapted to the connecting hole 1322; the mating structure of the bolt 1323 and the nut 1324 is used to clamp and fix the reinforcing bars 31 of the reinforcing cage 3 in the clamping space of the U-shaped structure 1321.

[0107] The connector 13 also includes a first reinforcement 134, which is an annular anti-pull base. It adopts a similar circular base form to the vertical anti-pull base 1311 and is fixed at the connection between the second connecting part 132 and the connecting rod 133. It itself constitutes the vertical anti-pull treatment at the connection between the connector 13 and the steel bar 31 of the steel cage 3. At the same time, the first reinforcement 134 can enhance the shear and bending resistance of the connection, prevent deformation or breakage under stress, and thus cope with the additional shear and tensile forces generated at the interface between concrete and ECC during underground construction.

[0108] The connector 13 also includes a plurality of second reinforcement members 135, which are evenly spaced along the circumferential interval of the connecting rod 133 to form a circumferential reinforcement treatment at the node connection between the connector 13 and the CFRP grid 12. One end of each second reinforcement member 135 is fixedly connected to the first reinforcement member 134, and the other end is fixedly connected to the vertical anti-pull base 1311 to form a support system, thereby strengthening the overall connection strength between the connecting rod 133, the vertical anti-pull base 1311, and the second connecting part 132 to cope with the shear and tensile forces at the interface.

[0109] The connecting hole 1322 is an elongated connecting hole 1322. The length direction of the elongated connecting hole 1322 is consistent with the opening direction of the U-shaped structure 1321, and the length dimension of the elongated connecting hole 1322 is greater than the diameter dimension of the bolt 1323, so that the mating structure of the bolt 1323 and the nut 1324 can move within the elongated connecting hole 1322, which can be adapted to clamp and fix the steel bars 31 of the steel cage 3 with different diameters.

[0110] In the above illustrative embodiments, the connectors of the CFRP-ECC template structure adopt a snap-fit ​​design of vertical anti-pull base and flip-over component, which can firmly clamp the CFRP grid nodes and enhance the connection rigidity with circumferential and vertical reinforcement components; the elongated connecting holes of the second connection part allow for fine adjustment of bolt positions to adapt to different diameter steel cages, and the CFRP-ECC template structure as a whole can be precisely matched with the diaphragm wall construction method, which is convenient to install, has a high reusability, and significantly improves the adaptability and reliability of diaphragm wall construction.

[0111] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0112] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A construction method for diaphragm walls based on CFRP-ECC, characterized in that, The CFRP-ECC template structure (1) is adopted, which includes ECC precast panels (11), CFRP grids (12) and connectors (13). The construction method of the diaphragm wall includes the following steps: S1. Obtain the lateral pressure of the rock layer (4) and the lateral pressure of the concrete (5) being poured, and take the larger value of the lateral pressure of the rock layer (4) and the lateral pressure of the concrete (5) being poured as the most unfavorable load. S2. Calculate the maximum bending moment of the stressed section of the CFRP-ECC template structure (1) based on the most unfavorable load. S3. Calculate the bending bearing capacity of the CFRP-ECC template structure (1) and determine the thickness of the ECC precast plate (11), the strip width, thickness and spacing of the CFRP grid (12) with the bending bearing capacity of the CFRP-ECC template structure (1) not less than the maximum bending moment of the CFRP grid structure (12) as a constraint. S4. Lay the CFRP grid (12) into the mold, fix the connector (13) at the node of the CFRP grid (12), pour ECC material to pre-embed the CFRP grid (12) and connector (13), cure until the preset strength is formed to form the ECC precast panel (11), and then demold to obtain the CFRP-ECC template structure (1). S5. After constructing the guide wall, excavate the trench section (2) and hoist the CFRP-ECC template structure (1) into the trench section (2) as the outer permanent template; S6. Hoist the steel cage (3) to the concrete (5) pouring side of the CFRP-ECC template structure (1), and fix the steel cage (3) to the CFRP grid (12) through the connector (13) to form a force transmission path. S7. Pour concrete (5) into the trench section (2) and cure it to complete the construction of the underground continuous wall.

2. The diaphragm wall construction method based on CFRP-ECC according to claim 1, characterized in that, In step S3, the constraint relationship that the bending bearing capacity of the stressed section is not less than the maximum bending moment of the stressed section is verified by the following formula: in, The maximum bending moment of the stressed section of the CFRP-ECC template structure (1) is given by: The bending capacity of the stressed section. This is the equivalent compression zone height coefficient of the stressed section. The effective height of the stressed section. The height of the pressure zone. For the tensile stress of the CFRP grid (12), The cross-sectional area of ​​the tension zone of the CFRP grid (12) is... This is the design value for the axial tensile crack strength of the ECC. Width of the stressed section The thickness of the ECC precast panel (11) is given.

3. The CFRP-ECC-based diaphragm wall construction method according to claim 2, characterized in that, In step S3, the thickness of the ECC precast panel (11), the strip width, thickness, and spacing of the CFRP grid (12) are determined by the following formula: in, For the thickness of the CFRP grid (12) strip, The width of the CFRP grid (12) strip is... The strip spacing of the CFRP grid (12) is... The coefficients are the equivalent rectangular stress curves of the compression zone. This is the design value for the axial compressive strength of the ECC shaft. Preset ECC precast panel (11) thickness CFRP grid (12) strip thickness CFRP grid (12) strip width The strip spacing of the CFRP grid (12) The thickness of the ECC precast panel (11), the strip width, thickness and spacing of the CFRP grid (12) are determined according to the formula.

4. The diaphragm wall construction method based on CFRP-ECC according to claim 3, characterized in that, The specific steps for determining the thickness of the ECC precast slab (11), the strip width, thickness, and spacing of the CFRP grid (12) are as follows: Preset ECC precast panel (11) thickness The cross-sectional area of ​​the tension zone of the CFRP grid (12) is determined according to the formula. ; If there is no solution, adjust the thickness of the ECC precast slab (11). And recalculate; If a solution exists, the strip width, thickness, and spacing of the CFRP grid (12) are preset, and the bending capacity of the stressed section is calculated. ,like Then adjust the strip width, thickness, and spacing of the CFRP grid (12) until... Finally, the thickness of the ECC precast panel (11), the strip width, thickness and spacing of the CFRP grid (12) were determined.

5. The diaphragm wall construction method based on CFRP-ECC according to claim 1, characterized in that, In step S4, a preset distance is reserved between the CFRP grid (12) and the concrete (5) pouring side surface of the ECC precast slab (11), so that the CFRP grid (12) is located near the edge of the tension zone to fully exert its tensile properties; and the connector (13) is partially exposed on the concrete (5) pouring side surface of the ECC precast slab (11) for subsequent connection with the reinforcing cage (3) to form a force transmission path.

6. A template structure based on CFRP-ECC, characterized in that, The CFRP-ECC formwork structure (1) applied to the diaphragm wall construction method based on CFRP-ECC as described in any one of claims 1-5 includes: ECC precast slab (11); CFRP grid (12), the CFRP grid (12) is embedded in the ECC precast slab (11), and a preset distance is reserved between it and the concrete (5) pouring side surface of the ECC precast slab (11), so that the CFRP grid (12) is located near the edge of the tension zone to give full play to its tensile properties; The connector (13) is fixed at the node of the CFRP grid (12) and partially exposes the concrete (5) pouring side surface of the ECC precast slab (11) for subsequent connection with the steel cage (3) to form a force transmission path.

7. The template structure based on CFRP-ECC according to claim 6, characterized in that, The connector (13) includes: The first connecting part (131) includes a vertical anti-pull base (1311) and a flipping part (1313); the flipping part (1313) is rotatably connected to the vertical anti-pull base (1311), the vertical anti-pull base (1311) is provided with a snap-fit ​​hole (1312), and the flipping part (1313) is provided with a snap-fit ​​protrusion (1314) adapted to the snap-fit ​​hole (1312); a clamping space for accommodating the nodes of the CFRP grid (12) is formed between the vertical anti-pull base (1311) and the flipping part (1313), and the two are clamped and fixed by the snap-fit ​​engagement of the snap-fit ​​protrusion (1314) and the snap-fit ​​hole (1312); The second connecting part (132) is connected to the vertical anti-pull base (1311) of the first connecting part (131) via a connecting rod (133); the second connecting part (132) includes a U-shaped structure (1321) with a connecting hole (1322), a bolt (1323) adapted to the connecting hole (1322), and a nut (1324); the mating structure of the bolt (1323) and the nut (1324) is used to clamp and fix the steel bars (31) of the steel cage (3) in the clamping space of the U-shaped structure (1321).

8. The template structure based on CFRP-ECC according to claim 7, characterized in that, The connector (13) further includes a first reinforcing member (134), which is located at the connection between the second connecting part (132) and the connecting rod (133).

9. The template structure based on CFRP-ECC according to claim 8, characterized in that, The connector (13) further includes a plurality of second reinforcement members (135), which are evenly spaced along the circumferential spacing of the connecting rod (133). One end of each second reinforcement member (135) is fixedly connected to the first reinforcement member (134), and the other end is fixedly connected to the vertical anti-pull-out base (1311).

10. The template structure based on CFRP-ECC according to claim 7, characterized in that, The connecting hole (1322) is an elongated connecting hole (1322). The length direction of the elongated connecting hole (1322) is consistent with the opening direction of the U-shaped structure (1321). The length dimension of the elongated connecting hole (1322) is greater than the diameter dimension of the bolt (1323), so that the mating structure of the bolt (1323) and the nut (1324) can move within the elongated connecting hole (1322) to adapt to clamp and fix the reinforcing bars (31) of the reinforcing cage (3) of different diameters.

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