Structure for improving lateral rigidity of existing underground diaphragm wall and construction method

Abstract

The invention discloses a structure for improving the lateral rigidity of an existing underground diaphragm wall and a construction method, solves the problems of single performance improvement and obvious space occupation in the utilization process of the existing underground diaphragm wall, and has the beneficial effect that the lateral rigidity of the underground diaphragm wall is multiplied on the premise of keeping the integrity of the existing structure. According to the specific scheme, the construction method for improving the lateral rigidity of the existing underground diaphragm wall comprises precast piles arranged on one side of the existing underground diaphragm wall, the precast piles are connected with the existing underground diaphragm wall, multiple columns of precast piles are arranged in the length direction of the existing underground diaphragm wall, and every two adjacent precast piles are connected through multiple rows of connecting components; the connecting component is connected with the existing underground diaphragm wall, multiple rows of waist beams are connected to the sides, away from the existing underground diaphragm wall, of the precast piles, embedded steel bars are reserved on the top sides of the precast piles and connected with main steel bars of the existing underground diaphragm wall, and concrete is poured on the tops of the existing underground diaphragm wall and the precast piles to form a top beam.

Description

Technical Field

[0001] The present invention relates to the field of underground space development and utilization, and in particular to a structure and construction method for improving the lateral stiffness of an existing underground continuous wall. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] With the development of urban underground space, the reuse of existing underground continuous walls has become an important topic in the field of underground engineering. As a temporary support structure, traditional underground continuous walls are often abandoned due to functional failure after the completion of the main structure. However, the frequent demand for close construction in new underground projects has made their reuse value increasingly prominent. Current engineering practice faces a double dilemma: if they are demolished and rebuilt, there will be problems such as high engineering costs, long cycles, and construction waste pollution; if they are directly reused, there will be technical bottlenecks such as insufficient rigidity and waterproof failure caused by structural aging. Existing reinforcement technologies mostly use a single reinforcement measure: grouting reinforcement is prone to stress concentration, external concrete encroachment on the cross-section will increase the space, and the addition of an internal support system will affect the use function.

[0004] The main methods and shortcomings of the existing underground continuous wall reuse are: (1) Direct reinforcement method: By spraying concrete or pasting carbon fiber cloth on the surface of the existing underground continuous wall for reinforcement, it has the advantages of fast construction and low cost. However, it has significant defects: the interface bonding reliability between the reinforcement layer and the original wall is insufficient, and it is easy to peel off after long-term use; the waterproof performance is not substantially improved, and the problem of leakage in the existing joints cannot be solved; the stiffness improvement is limited, which makes it difficult to meet the needs of secondary development of deep foundation pits.

[0005] (2) Internal support reinforcement method: Adding a steel support or concrete support system to the inner side of the continuous wall can provide greater lateral stiffness. Its advantages are clear force and mature calculation model. However, there are obvious disadvantages: the support components encroach on the underground space, seriously restricting the use function; the node connection is complex, and the subsequent removal is prone to secondary damage; the waterproof system needs to be set up separately, which increases the overall cost.

[0006] (3) Replacement reinforcement method: This method uses a process of demolishing the structure in sections and then inserting new pile walls, which can achieve a comprehensive update of the structural performance. The main advantage is that it can completely solve the aging problem and significantly improve the bearing capacity. However, it has serious limitations: a temporary support system must be set up during construction, which increases the project cost; the demolition process generates a large amount of construction waste, which is costly to the environment; and the construction period is extended, which affects the progress of the project.

[0007] In summary, existing technologies generally have the triple contradictions of "single performance improvement, significant space encroachment, and large environmental disturbance", which makes it difficult to meet the needs of modern urban underground space transformation and utilization. Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a structure for improving the lateral stiffness of existing underground continuous walls. Through the dual design of component synergy and space optimization, it can reduce the occupation of underground space while ensuring performance improvement, and avoid demolition of existing structures during the entire construction process, which is a significant technological breakthrough.

[0009] In order to achieve the above object, the present invention is implemented through the following technical solutions: A structure for improving the lateral stiffness of an existing underground continuous wall includes a steel sheet pile component arranged on one side of the existing underground continuous wall to form an anti-seepage interface, and also includes a precast pile arranged on the other side of the existing underground continuous wall. The precast piles are connected to the existing underground continuous wall. Multiple rows of precast piles are arranged along the length direction of the existing underground continuous wall. Adjacent precast piles are connected by multiple rows of connecting components. The connecting components are connected to the existing underground continuous wall. A waist beam is connected to the side of the precast pile away from the existing underground continuous wall. The waist beam is arranged in multiple rows. An embedded steel bar is reserved on the top side of the precast pile. The embedded steel bar is connected to the main steel bar of the existing underground continuous wall, and concrete is poured on the top of the existing underground continuous wall and the precast piles to form a crown beam.

[0010] In the structure for improving the lateral stiffness of an existing underground continuous wall as described above, the number of rows of the connecting members is greater than the number of rows of the waist beams, and the waist beams are arranged between two adjacent rows of connecting members.

[0011] As described above, a structure for improving the lateral stiffness of an existing underground continuous wall is provided, wherein the connecting member is structural steel, and both ends of the structural steel in the length direction are connected to the precast piles via T-shaped connecting plates, and one side of the structural steel in the width direction is connected to the existing underground continuous wall via a support plate.

[0012] A structure for improving the lateral stiffness of an existing underground continuous wall, wherein the precast piles are connected to the existing underground continuous wall via a first connecting pipe. The first connecting pipe passes through the precast piles and is inserted into the existing underground continuous wall, and the first connecting pipe is bonded to the existing underground continuous wall. A second connecting pipe is provided on the side of the precast pile facing the waist beam. The second connecting pipe passes through the waist beam and is inserted into the precast pile. The second connecting pipe is welded to the main reinforcement of the waist beam. After welding, concrete is poured to form the waist beam.

[0013] A structure for improving the lateral stiffness of an existing underground continuous wall as described above, wherein a wedge-shaped block is provided between the inner side of the precast pile and the existing underground continuous wall; The precast pile is provided with grouting holes longitudinally from the pile head to the pile tail. The grouting holes are located on the side of the precast pile close to the existing underground continuous wall. The grouting holes are opened at appropriate intervals along the length of the precast pile so that the slurry can be injected into the soil between the existing underground continuous wall and the precast pile.

[0014] In a second aspect, the present invention further provides a construction method for improving the lateral stiffness of an existing underground continuous wall, comprising the following contents: Excavate the foundation trench to expose the crown beam, inspect the existing underground continuous wall to determine the location of the underground continuous wall defects, and perform grouting reinforcement on the locations of the existing underground continuous wall defects; Construct steel sheet pile components on one side of the existing underground continuous wall to form an anti-seepage interface; Precast piles are constructed on the other side of the existing underground continuous wall, and multiple rows of precast piles are arranged along the length of the existing underground continuous wall; Adjacent precast piles are connected by multiple rows of connecting components, and the connecting components are connected to the existing underground continuous wall; Construct waist beams on the side of the precast piles away from the existing underground continuous wall, with multiple rows of waist beams; Continue excavating downwards and repeat the construction of connecting components and waist beams until the designed bottom elevation of the foundation pit is reached; Anchor bars are reserved on the top side of the precast piles, which are connected to the main bars of the existing underground continuous wall. Concrete is poured on the top of the existing underground continuous wall and precast piles to form a crown beam.

[0015] As described above, a construction method for improving the lateral stiffness of an existing underground continuous wall is provided, wherein the steel sheet pile component is formed by overlapping a plurality of Larsen steel sheet piles in sequence, and a distance is set between the inner side of the Larsen steel sheet pile and the existing underground continuous wall.

[0016] The above-mentioned construction method for improving the lateral stiffness of an existing underground diaphragm wall uses a co-location tracer method combined with a core drilling method to detect the existing underground diaphragm wall, including the following: Vertical drilling is performed in the soil on both sides of the existing underground diaphragm wall to form an isotope injection well on the outside of the existing underground diaphragm wall and an isotope monitoring well on the inside of the existing underground diaphragm wall; Isotopes are injected into the inner isotope injection well, and a gamma spectrometer is placed in the outer isotope monitoring well; Use gamma spectrometer to scan the existing underground diaphragm wall to find the leakage point location and determine the abnormal part of the existing underground diaphragm wall; After confirming the existence of abnormal parts in the existing underground continuous wall, the defective section is accurately located based on the detection data, and then core drilling is carried out on the top surface of the underground continuous wall in the corresponding area. By controlling the drilling and coring depth, the abnormal part is directly reached, and core samples are simultaneously extracted for physical verification.

[0017] A construction method for improving the lateral stiffness of an existing underground continuous wall, as described above, comprises: after the construction of the connecting member, drilling the existing underground continuous wall through the first reserved hole of the precast pile, inserting the first connecting pipe into the drilled hole of the existing underground continuous wall through the first reserved hole, and pouring epoxy resin; A second connecting pipe is implanted in the second reserved hole of the precast pile. The second connecting pipe is arranged beyond the side of the precast pile. The main reinforcement of the waist beam is laid through the second connecting pipes at multiple precast piles. The second connecting pipe and the main reinforcement of the waist beam are overlapped and welded, and then concrete is poured to form the waist beam.

[0018] In the construction method for improving the lateral stiffness of an existing underground continuous wall, after the precast piles are sunk, grouting is performed through the grouting holes of the precast piles, so that the grout effectively penetrates and completely fills the soil between the existing underground continuous wall and the precast piles, thereby solidifying the cementitious body. If local areas are found where the contact surface density between the precast piles and the existing underground continuous wall is insufficient, wedge blocks shall be used to implement bidirectional tightening reinforcement between the precast piles and the existing underground continuous wall.

[0019] The beneficial effects of the present invention are as follows: 1) In the present invention, steel sheet pile components are arranged on one side of the existing underground continuous wall to form a waterproof interface, and precast piles are arranged on the other side. The precast piles are connected by connecting components, and the precast piles are connected to the existing underground continuous wall. Waist beams and connecting components are connected between the precast piles, and crown beams are arranged between the precast piles and the underground continuous wall. In this way, the existing underground continuous wall and the precast piles form an integrated structure. The precast piles and the connecting components are combined to form a spatial truss effect, and the stiffness is doubled by cooperating with the waist beam. The multi-point connection structure of the crown beam realizes the overall coordination of each reinforcement component, breaking through the single defect of the traditional reinforcement method, not only ensuring the structural stiffness of the overall structure, but also ensuring the overall waterproof effect, without occupying too much space, and without demolishing the underground continuous wall. The environmental disturbance is small, providing an innovative path for the functional upgrade of the existing underground continuous wall.

[0020] 2) The present invention rationally arranges the connecting member structure, which not only ensures the connection between two adjacent precast piles, but also ensures the connection between the connecting member and the existing underground continuous wall. The precast pile is connected to the existing underground continuous wall through the first connecting pipe, and the second connecting pipe is welded to the main reinforcement of the waist beam to ensure the connection strength between the waist beam and the precast pile.

[0021] 3) In the present invention, grouting is performed on the precast piles through the precast pile grouting holes so that the slurry can be injected into the soil between the existing underground continuous wall and the precast piles, thereby forming a solidified cementitious body with excellent interface bonding performance. By enhancing the mechanical transmission efficiency between the substrates, after the grouting of the precast piles is completed, if a local area where the density of the contact surface between the precast piles and the existing underground continuous wall is insufficient is found, a wedge block is embedded to tighten it. The innovatively designed wedge block works synergistically with the grouting to ensure that the new and old structures are subjected to coordinated force.

[0022] 4) In the construction method of the present invention, a continuous anti-seepage interface is formed between Larsen steel sheet piles and the existing wall, effectively solving the problem of interface leakage. A systematic detection, evaluation and coordinated reinforcement technology system for existing underground continuous walls is established. Based on the structural performance diagnosis results, targeted reinforcement measures are implemented, i.e., reinforcement is carried out. The lateral stiffness and bearing safety factor of the wall are improved through structural reinforcement. The anti-seepage system is reconstructed to achieve gradient blocking of the groundwater infiltration path, thereby improving the strength of the existing underground continuous wall, thus forming an overall comprehensive solution of waterproofing, reinforcement and connection. While extending the service performance of the underground continuous wall throughout its life cycle, it also provides reliable underground space enclosure protection for adjacent new construction projects, effectively controlling the risk of structural deformation caused by deep foundation pit construction.

[0023] 6) The present invention sets an isotope injection well on the outside of the existing underground continuous wall along the extension direction of the existing underground continuous wall, and arranges a monitoring well at the corresponding position on the inside of the wall. By injecting a radioactive isotope tracer into the periphery of the underground continuous wall, a gamma spectrometer is used to monitor the migration pattern of the tracer inside and outside the wall, accurately locating the leakage point and quantifying the seepage rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is a front view of a structure for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0026] Figure 2 It is a schematic diagram of the side of a structure for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0027] Figure 3 It is a schematic diagram of the connection between an I-beam, a T-shaped connecting plate, and a support plate in a structure for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0028] Figure 4It is a flow chart of a construction method for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0029] Figure 5 It is a schematic diagram of foundation pit excavation in a construction method for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0030] Figure 6 It is a schematic diagram of detecting an existing underground continuous wall in a construction method for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0031] Figure 7 It is a top view of a structure for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0032] Figure 8 It is a side view of a structure for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0033] Figure 9 It is a schematic diagram of foundation pit backfilling in a construction method for improving the lateral stiffness of an existing underground continuous wall according to one or more embodiments of the present invention.

[0034] In the figure: the distances or sizes between parts are exaggerated to show the positions of various parts, and the schematic diagram is for reference only.

[0035] Among them: 1. Existing underground continuous wall, 2. Existing cap beam, 3. Soil layer, 4. Isotope injection well, 5. Isotope, 6. Isotope monitoring well, 7. Gamma spectrometer, 8. Larsen steel sheet pile, 9. Existing underground continuous wall reinforcement, 10. Wedge-shaped steel block, 11. Precast square pile, 12. First connecting pipe, 13. First epoxy resin, 14. I-beam, 15. First high-strength bolt group, 16. T-type connecting plate, 17. Support plate, 18. Grouting hole, 19. Waist beam, 20. Grout, 21. Cap beam, 22. Bar soil, 23. Second high-strength bolt group, 24. Planted rebar, 25. Second connecting pipe, 26. Third high-strength bolt group, 27. First pipe hole, 28. Side reserved hole, 29. Second pipe hole, 30. Second epoxy resin, 31. First reserved hole, 32. Second reserved hole. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise clearly indicated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprising" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations; As introduced in the background technology, in the prior art, there are three contradictory problems in the process of utilizing existing underground continuous walls: single performance improvement, significant space encroachment, and large environmental disturbance. In order to solve the above technical problems, the present invention proposes a structure for improving the lateral stiffness of existing underground continuous walls.

[0038] Example 1 In a typical embodiment of the present invention, this embodiment provides a structure for improving the lateral stiffness of an existing underground continuous wall. Figure 1 As shown, it includes precast piles arranged on one side of the existing underground continuous wall 1, the precast piles are connected to the existing underground continuous wall 1, and multiple rows of precast piles are arranged along the length direction of the existing underground continuous wall 1. The adjacent precast piles are connected by multiple rows of connecting components, and the connecting components are connected to the existing underground continuous wall 1. A waist beam 19 is connected to the side of the precast pile away from the existing underground continuous wall. The waist beam 19 is provided with multiple rows, and embedded steel bars 24 are reserved on the top side of the precast piles. The embedded steel bars 24 are connected to the main bars of the existing underground continuous wall 1, and concrete is poured on the top of the existing underground continuous wall 1 and the precast piles to form a crown beam 21.

[0039] Because the excavation is gradually carried out downward along the height direction of the foundation pit, in order to ensure the overall stability, the connecting components and the waist beam 19 are gradually set. The number of rows of connecting components is more than the number of rows of waist beams 19, and the waist beam is set between two adjacent rows of connecting components.

[0040] In this embodiment, reference Figure 3As shown, the connecting member is structural steel, and an I-beam 14 can be selected. To ensure the stability and reliability of the connection, the two ends of the structural steel in the length direction are connected to the precast piles through T-shaped connecting plates 16. One side of the T-shaped connecting plate 16 is overlapped on the upper side of the web of the I-beam 14 and is connected by a first high-strength bolt group 15 composed of multiple high-strength bolts. The other side of the T-shaped connecting plate 16 is connected to the side of the precast pile by a second high-strength bolt group 23 formed by multiple high-strength bolts. The side of the precast pile is provided with a side reserved hole 28, and the high-strength bolts are set through the side reserved hole 28. One side of the structural steel in the width direction is connected to the existing underground continuous wall 1 through a support plate 17. The support plate 17 is specifically a square support plate. The support plate 17 is arranged on the inner side of the I-beam. The third high-strength bolt group 26 passes through the support plate 17 and the side wall of the I-beam 14 and enters the first pipe hole 27 of the existing underground continuous wall 1, and fills the opening of the existing underground continuous wall with epoxy resin, forming a second epoxy resin 30 at the opening of the existing underground continuous wall 1.

[0041] Among them, the precast piles adopt precast square piles 11, and the precast piles are longitudinally provided with grouting holes 18 from the pile head to the pile tail. The grouting holes 18 are located on the side of the precast pile close to the existing underground continuous wall 1. The grouting holes 18 are opened at appropriate intervals along the length direction of the precast piles so that the slurry can be injected into the soil between the existing underground continuous wall 1 and the precast piles, thereby forming a solidified cementing body with excellent interface bonding performance, and ultimately achieving a systematic improvement in the overall bearing capacity and deformation coordination performance of the building envelope system by enhancing the mechanical transmission efficiency between the substrates.

[0042] In addition, the precast pile and the existing underground continuous wall 1 are connected through a first connecting pipe 12 such as a first steel pipe. The first connecting pipe 12 passes through the precast pile and is inserted into the second pipe hole 29 of the existing underground continuous wall 1. The second pipe hole 29 and the first pipe hole 27 are both formed by drilling. The second pipe hole 29 is drilled through the first reserved hole 31 of the precast pile. The length of the second pipe hole 29 is greater than the length of the first pipe hole 27. The inner diameter of the second pipe hole 29 is greater than the inner diameter of the first pipe hole 27. The first connecting pipe 12 is bonded to the existing underground continuous wall 1 by epoxy resin, and a first epoxy resin 13 is formed in the second pipe hole 29 of the existing underground continuous wall 1. A second connecting pipe 25 is provided on the side of the precast pile facing the waist beam. The second connecting pipe 25 passes through the waist beam 19 and is inserted into the second reserved hole 32 of the precast pile. The second connecting pipe 25 is welded to the main reinforcement of the waist beam. After welding, concrete is poured to form the waist beam 19.

[0043] It should be noted that after the grouting of the precast piles is completed, "ultrasonic detection technology" is used to detect the integrity of the concrete. If a local area is found where the contact surface density between the precast square pile 11 and the existing underground continuous wall 1 is insufficient, a wedge block such as a wedge-shaped steel block 10 is used to implement bidirectional tightening reinforcement. A wedge block is set between the inner side of the precast pile and the existing underground continuous wall to facilitate construction and better optimize the force transmission path.

[0044] The structure provided in this embodiment comprises over 75% prefabricated components (including square piles, I-beam connectors, and wedge blocks). Compared to cast-in-place structures, the construction period is shortened by 30%-40%, on-site wet work is reduced by 60%, and dust pollution is effectively controlled. Prefabricated nodes are connected using high-strength bolts, ensuring structural integrity while enabling reversible construction, facilitating subsequent maintenance. By retaining the existing underground continuous wall, zero demolition construction is achieved, reducing the workload of the temporary support system, lowering the amount of construction waste generated, and achieving a steel recycling rate. This expands the application boundaries of underground continuous walls in complex scenarios such as urban renewal and rail transit, reduces overall renovation costs, and decreases carbon emission intensity, forming a "test-and-reinforce" full-cycle green construction technology system.

[0045] Example 2 refer to Figure 4 As shown, this embodiment provides a construction method for improving the lateral stiffness of an existing underground continuous wall, including the following contents: Step 1: Construction Preparation During the project launch and preparatory phases, the following core tasks must be prioritized: First, a systematic assessment of the potential impacts of surrounding ongoing projects and adjacent buildings on the project will be conducted. A multi-stakeholder joint construction drawing review team will be established to thoroughly review the design documents, while simultaneously completing technical briefings from the design firm. Based on the project's characteristics and on-site working conditions, a scientifically tailored construction organization plan and scheme will be developed, while verified project positioning baselines and elevation control point data will be obtained. Simultaneously, infrastructure support facilities such as temporary water and power supply and on-site road paving will be constructed, and the layout of production areas such as the rebar processing area and slurry circulation pool will be strategically planned. Large-scale construction machinery and lifting equipment entering the site must undergo standardized installation and commissioning procedures and a three-level acceptance system to ensure safe and reliable operation. All incoming construction materials will be strictly inspected before use. After verifying the integrity of factory quality certification documents, random sampling and re-inspection will be conducted in accordance with regulatory requirements, establishing a comprehensive material traceability mechanism.

[0046] Before construction, a professional surveying team should be organized to implement total station surveying and closure review operations, and form a positioning and setting-out review record file. According to the site's topographical characteristics and engineering accuracy requirements, the existing hierarchical layout method should be used to establish a surveying benchmark network that includes a plane coordinate control system and an elevation transfer system. The closed conductor form should be used to enhance network stability. A monitoring mechanism should be established that includes quarterly re-surveys and special inspections after extreme weather. Protective measures such as concrete protective pier covering and regular three-dimensional coordinate verification should be taken for control pile points. The determination of the outward release of the construction boundary of the underground continuous wall must be based on the inversion analysis of the stratum parameters. Through the existing foundation pit deformation prediction model and numerical simulation verification, the design parameters should be dynamically adjusted in combination with survey data such as the depth of the bearing layer and groundwater level fluctuations.

[0047] Step 2: Excavation of foundation trench refer to Figure 5 As shown in the figure, after site dewatering was completed, excavation work began on the top of the existing diaphragm wall according to the pre-determined construction plan. First, symmetrical excavation was carried out along the axis of the existing diaphragm wall 1. A 1:1 slope was used to form a V-shaped trench, fully exposing the crown beam 2 at the top of the existing structure. Based on the characteristics of the stratum, a phased construction process was adopted: the excavation area was divided into several work units, and earthwork was unloaded according to the principle of "layered excavation and staggered advancement." The excavation depth of each layer was controlled within the effective operating range of the machinery, and slope finishing was carried out simultaneously to maintain the designed slope.

[0048] Excavation continues until the trench bottom elevation reaches 300mm below the crown beam bottom baseline. This overexcavation setting not only meets subsequent construction requirements but also allows for adjustment for measurement errors. During actual construction, the final excavation elevation can be dynamically adjusted within a ±100mm range based on changing geological conditions and structural design requirements. It is understood that those skilled in the art can select the excavation depth of the foundation trench based on actual needs.

[0049] It should be noted that the entire construction process adopts a composite construction method with long-arm excavators as the main equipment and manual slope repair. By combining mechanized flow operations with manual refined operations, a balance between construction efficiency and quality control is achieved.

[0050] Step 3: Detect the existing underground continuous wall 1 In this embodiment, the isotope tracing method is combined with the core drilling method to detect whether there are defects in the existing underground continuous wall 1. Specifically, the abnormal part of the existing underground continuous wall 1 is narrowed and determined by the isotope tracing method, and the specific location of the defects in the abnormal part area is detected by the core drilling method.

[0051] refer to Figure 6As shown, the isotope tracer method uses isotopes 5 and gamma spectrometer 7. Existing equipment can be used for the isotopes 5 and the gamma spectrometer 7, which will not be described in detail here. First, vertical holes are drilled in the soil on both sides of the existing underground continuous wall 1, and an isotope injection well 4 is formed on the outside of the existing underground continuous wall, and an isotope monitoring well 6 is formed on the inside of the existing underground continuous wall. In this embodiment, vertical holes are formed at each set distance (such as 10m) on both sides of the existing underground continuous wall 1 along the inner and outer contour lines of the existing underground continuous wall 1. It can be understood that those skilled in the art can set the spacing between adjacent vertical holes according to actual needs, and then inject isotopes 5 into the inner isotope injection well 4 and place the gamma spectrometer 7 in the outer isotope monitoring well 6. During the lowering process, the gamma spectrometer 7 should be placed first and then the isotope 5 should be injected. The existing underground continuous wall is detected by a flat measurement method.

[0052] The gamma spectrometer 7 is used to scan the existing underground continuous wall 1 to find the leakage point, so as to determine the abnormal part of the existing underground continuous wall 1. The isotope injection well 4 and the isotope monitoring well 6 are arranged in the abnormal area found by monitoring, and multiple isotope tracing operations are carried out to accurately locate the coordinates of the leakage point. After confirming the presence of a structural anomaly in the existing diaphragm wall 1, the defective section was precisely located based on test data. Core drilling was then conducted on the top surface of the wall in the corresponding area. The depth of the core was controlled to reach the anomaly, and core samples were simultaneously extracted for physical verification. Simultaneously, a high-precision in-hole camera system was used to perform 360° panoramic scanning along the drilling trajectory. This enabled the three-dimensional location and quantitative analysis of hidden defects in the concrete structure, such as honeycombs, segregation zones, and through-cracks. The size and distribution of the defect interfaces were precisely determined, providing critical decision-making support for the structural safety rating of the existing diaphragm wall and the design of repair and reinforcement parameters.

[0053] The in-hole camera technology can adopt existing technologies such as drilling endoscopes, and will not be described in detail here.

[0054] Step 4: Reinforce the existing underground continuous wall 1 After accurately locating the structural defects using step 3, a high-pressure grouting repair process is implemented based on the in-situ coring channel on the top surface of the existing underground continuous wall 1 or a newly constructed grouting hole.

[0055] Specifically, grouting should give priority to using existing inspection core holes as grouting channels; when there is a spatial deviation between the existing hole position and the defect area, a new hole should be drilled above the defect area and the drilling axis should be ensured to be accurately extended to the defect area before implementing the high-pressure grouting repair process.

[0056] For newly drilled grouting holes, a standardized "drill-inspect-clean" process is implemented: the hole quality should be inspected immediately after drilling, and then debris should be removed through a gas-water composite hole cleaning process to ensure the cleanliness of the grouting channel.

[0057] The specific method of grouting reinforcement is to precisely place the grouting conduit into a newly drilled or existing channel, connect it to a standardized high-pressure grouting unit, and use the high-pressure grouting unit to inject cement slurry into the newly drilled or existing channel. The pressure parameters and slurry injection volume during the grouting operation must be precisely controlled. By optimizing the process parameters, the grouting effectively penetrates and completely fills the fracture network, thereby forming a solidified bond with excellent interfacial bonding properties. By enhancing the mechanical transmission efficiency between the substrates, the overall load-bearing capacity and deformation coordination performance of the building envelope system can be systematically improved. Existing high-pressure grouting equipment can be used and will not be described in detail here.

[0058] After the grouting process is complete, ordinary Portland cement-based mortar or slightly expansive cement-based materials should be used for sealing. After the sealing construction is completed, standardized maintenance procedures should be implemented in the treated area in strict accordance with engineering technical standards to effectively ensure the density and durability of the sealing interface structure and achieve the control indicators of the project structure integrity.

[0059] In this embodiment, the defects of the existing underground continuous wall are accurately located by the isotope tracing method, and combined with targeted repair and reinforcement technology, the wall strength, anti-seepage ability and stability of the underground continuous wall are improved, the service life is extended, and safe and efficient reinforcement is achieved.

[0060] Step 5: Construction of Larsen Steel Sheet Pile 8 In this embodiment, a steel sheet pile assembly is installed on the other side of the existing diaphragm wall from the precast piles. The steel sheet pile assembly comprises multiple Larsen steel sheet piles 8 connected in sequence, with adjacent Larsen steel sheet piles 8 overlapping and interlocking. The Larsen steel sheet piles 8 are constructed using the outer contour of the existing diaphragm wall as a reference. A total station (with a distance measurement accuracy of ±2 mm) is used to precisely deflect the pile axis outward to ensure continuity of the anti-seepage interface. A static pile driver equipped with a laser guidance system is used to drive the piles. The interlocking of adjacent piles is strictly controlled, and the driving depth is maintained at the same elevation as the existing diaphragm wall, with a verticality deviation of ≤1 / 200. The width of the working surface between the inner side of the Larsen steel sheet piles 8 and the existing diaphragm wall 1 is ensured to meet the operational requirements for anti-seepage treatment of the interface between the newly cast crown beam 21 and the existing diaphragm wall 1. Existing static pile driver equipment can be used and will not be described in detail here.

[0061] Step 6: Increase the lateral rigidity of the existing underground continuous wall by constructing precast piles, i.e., precast square piles. Multiple rows of precast piles are arranged along the length of the existing underground continuous wall. Adjacent precast piles are connected by multiple rows of connecting members, such as I-beams 14, which are connected to the existing underground continuous wall 1. The specific steps include: Step 6.1: Reference Figure 7 As shown, in this embodiment, the construction of prefabricated square piles 11 is based on the inner contour line of the existing underground continuous wall. A total station (planar positioning error ≤ 5mm) is used to accurately locate the pile positions at intervals of 1.2m. It is understood that those skilled in the art can select the pile spacing according to actual needs. A static pile driver is used to sink the piles. The static pile driver equipment can be used with existing equipment and is not described in detail here. In addition, a laser guidance system is configured to carry out the pile sinking operation. The pile sinking depth is controlled to be at the same elevation as the existing underground continuous wall, with a verticality deviation of ≤1 / 150. The final spacing between the inner side of the pile and the inner contour line of the existing underground continuous wall is 150mm. It is understood that those skilled in the art can select the spacing between the inner side of the pile and the inner contour line of the existing underground continuous wall according to actual needs.

[0062] Step 6.2: After the prefabricated square pile 11 is sunk, the grouting conduit is accurately placed into the grouting hole 18 reserved for the prefabricated square pile. Figure 8 As shown, the grouting holes 18 are longitudinally opened from the pile head to the pile tail in the prefabricated square pile 11 near the existing underground continuous wall 1. The grouting holes 18 are opened at appropriate intervals along the length of the pile. After the grouting conduit is connected to the standardized high-pressure grouting unit, the high-pressure grouting unit is used to inject ordinary Portland cement-based mortar; the high-pressure grouting equipment can use existing equipment and will not be described in detail here.

[0063] In addition, the pressure parameters and slurry injection volume in the grouting operation must be precisely controlled. By optimizing the process parameters, it is ensured that the slurry 20 effectively penetrates and completely fills the soil between the existing underground continuous wall 1 and the prefabricated square piles 11, thereby forming a solidified cementitious body with excellent interface bonding properties. By enhancing the mechanical transmission efficiency between the substrates, the overall bearing capacity and deformation coordination performance of the building envelope system can be systematically improved.

[0064] Step 6.3: In this embodiment, "ultrasonic detection technology" is used to detect the integrity of the concrete. If a local area is found where the contact surface density between the prefabricated square pile 11 and the existing underground continuous wall 1 is insufficient, wedge blocks such as wedge-shaped steel blocks 10 are used to implement bidirectional tightening reinforcement. Multiple wedge-shaped steel blocks can be provided along the height direction of the prefabricated square pile 11.

[0065] The specific construction method for the wedge-shaped steel blocks 10 is as follows: The wedge-shaped steel blocks 10 are made of Q355B steel, have a taper of 1:5, and measure 300×150×50mm. They are symmetrically arranged within the gap between the prefabricated square piles and the existing wall. A double-acting hydraulic jacking system is used for staged pressurization, with a jacking speed of ≤3mm / s. It is understood that those skilled in the art can select the material, taper, and dimensions of the wedge-shaped steel blocks 10 based on actual needs.

[0066] Step 6.4: Carry out layered and segmented excavation along the inner side of the existing underground continuous wall (single-layer height ≤ 2.5m) and complete the construction of the structural system layer by layer. It is understandable that those skilled in the art can select the single-layer excavation height according to actual needs: Step 6.4.1 (I-beam installation): Use a drill to drill holes in the existing diaphragm wall 1 at the designed location. The first pipe hole 27 has a diameter of 32 mm and a depth of 400 mm. The drilling location should avoid the existing diaphragm wall reinforcement 9. The ends of the I-beam web are connected to the pre-welded T-shaped connecting plate 16 (plate thickness 20mm) using the M24 first high-strength bolt group 15. The I-beam 14 and T-shaped connecting plate 16 are made of Q355B steel. The ends of the connected components are butted against the reserved holes 28 on the sides of the prefabricated square piles. The connected components are fixed to the prefabricated square piles 11 using the M24 second high-strength bolt group 23. Place the flange of the I-beam close to the inner side of the existing underground continuous wall 1 and anchor it to the ground continuous wall 1 through a 200×200×16mm support plate 17 and a third M24 high-strength bolt group 26. The support plate 17 is made of Q355B steel, but other steel materials can also be used. In addition, the first pipe hole 27 formed at the connection between the third high-strength bolt group 26 and the existing underground continuous wall 1 is filled with epoxy resin; it can be understood that those skilled in the art can change the hole diameter, hole depth, T-shaped connecting plate 16, support plate 17 and the specifications of the first high-strength bolt group 15, the second high-strength bolt group 23 and the third high-strength bolt group 26 according to actual needs; the drilling equipment and high-strength bolt construction process can use existing technology and will not be described in detail here.

[0067] Step 6.4.2 (Anchoring the First Connecting Pipe): At the elevation of the I-beam axis, drill a hole (depth ≥ 300 mm) into the existing wall using a drilling rig. Insert a Φ48 × 3.5 mm steel pipe into the second pipe hole 29 as the first connecting pipe and fill it with epoxy resin (grouting pressure 0.6–1.2 MPa). It will be appreciated that those skilled in the art may modify the diameter, depth, and dimensions of the second pipe hole 29 as needed. Existing drilling equipment and grouting techniques may be used and are not described in detail here.

[0068] Step 6.4.3 (Casting the Waist Beam): Insert a Φ60×4mm steel pipe as the second connecting pipe 25 (250mm exposed) into the second reserved hole 32 of the prefabricated square pile below the I-beam 14. This pipe is double-sided lap welded to the main reinforcement of the waist beam (weld height ≥ 8mm), and then poured with concrete. It will be understood that those skilled in the art can change the diameter and depth of the second reserved hole 32 and the specifications of the second connecting pipe 25 according to actual needs. The waist beam casting process can be based on existing technology and is not described in detail here.

[0069] Step 6.4.4 (Cyclic construction control): Repeat steps 6.4.1 to 6.4.3 according to the process of "I-beam installation → second connecting pipe anchoring → waist beam casting", and excavate cyclically. The verticality deviation is controlled to ≤1 / 200 throughout the process until the designed bottom elevation of the foundation pit is reached.

[0070] It is worth noting that during the production stage, all reserved pipe holes in the prefabricated square piles 11 should be pre-buried with PVC sleeves (wall thickness ≥ 3 mm) in the reserved holes, and the sleeve length should exceed the hole opening by 50 mm to form a physical isolation barrier to prevent the reserved pipe holes from being blocked by slurry during the grouting operation in step 6.2.

[0071] Step 6.4.5 (Crown beam construction): Pre-reinforced concrete 24 is reserved on the top of the prefabricated square pile 11. The reinforced concrete 24 and the main reinforcement of the existing underground continuous wall 1 are welded and then cast along the entire length to form the crown beam 21. The construction process of the crown beam 21 and the reinforced concrete 24 can be constructed using existing technology and will not be described in detail here.

[0072] Step 7: Backfill the foundation trench In this embodiment, reference Figure 9 As shown, plain soil 22 is used to backfill to the ground level, and at this time, the construction of increasing the lateral stiffness of the existing underground continuous wall is completed.

[0073] The construction method of this embodiment successfully achieves a significant improvement in the lateral stiffness performance of the existing underground continuous wall, effectively meeting the structural load requirements of the new construction project. During the construction process, an in-situ retention technology strategy is adopted to avoid the demolition of the existing underground continuous wall 1, and simultaneously reduce the construction of temporary support structures and the reconstruction process of the foundation system, thereby optimizing the efficiency of construction resource allocation and effectively enhancing the utilization rate of building materials throughout the life cycle, in line with modern green construction concepts and sustainable development strategy requirements. Based on the innovative application of structural stiffening technology, it breaks through the structural limitations of the traditional underground continuous wall's lateral waterproofing and bearing system, enabling it to have the technical capabilities to cope with complex engineering conditions such as ultra-deep foundation pit support and comprehensive development of underground space. While significantly expanding the applicable boundaries of the project, it simultaneously enhances the structural safety reserve and environmental adaptability.

[0074] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A structure for improving the lateral stiffness of an existing underground continuous wall, characterized in that: It includes a steel sheet pile component arranged on one side of the existing underground continuous wall to form an anti-seepage interface, and also includes a precast pile arranged on the other side of the existing underground continuous wall. The precast piles are connected to the existing underground continuous wall. There are multiple rows of precast piles along the length direction of the existing underground continuous wall. Adjacent precast piles are connected by multiple rows of connecting components. The connecting components are connected to the existing underground continuous wall. A waist beam is connected to the side of the precast pile away from the existing underground continuous wall. There are multiple rows of waist beams. An embedded steel bar is reserved on the top side of the precast pile. The embedded steel bar is connected to the main steel bar of the existing underground continuous wall, and concrete is poured on the top of the existing underground continuous wall and the precast piles to form a crown beam.

2. The structure for improving the lateral stiffness of an existing underground continuous wall according to claim 1, characterized in that: The number of rows of the connecting members is greater than the number of rows of the waist beams, and the waist beams are arranged between two adjacent rows of connecting members.

3. The structure for improving the lateral stiffness of an existing underground continuous wall according to claim 1, characterized in that: The connecting member is structural steel, and both ends of the structural steel in the length direction are connected to the prefabricated piles through T-shaped connecting plates, and one side of the structural steel in the width direction is connected to the existing underground continuous wall through a support plate.

4. The structure for improving the lateral stiffness of an existing underground continuous wall according to claim 1, characterized in that: The precast piles are connected to the existing underground continuous wall via a first connecting pipe. The first connecting pipe passes through the precast piles and is inserted into the existing underground continuous wall. The first connecting pipe is bonded to the existing underground continuous wall. A second connecting pipe is provided on the side of the precast pile facing the waist beam. The second connecting pipe passes through the waist beam and is inserted into the precast pile. The second connecting pipe is welded to the main reinforcement of the waist beam. After welding, concrete is poured to form the waist beam.

5. The structure for improving the lateral stiffness of an existing underground continuous wall according to claim 1, characterized in that: A wedge-shaped block is provided between the inner side of the precast pile and the existing underground continuous wall; The precast pile is provided with grouting holes longitudinally from the pile head to the pile tail. The grouting holes are located on the side of the precast pile close to the existing underground continuous wall. The grouting holes are opened at appropriate intervals along the length of the precast pile so that the slurry can be injected into the soil between the existing underground continuous wall and the precast pile.

6. A construction method for improving the lateral stiffness of an existing underground continuous wall, characterized in that: Includes the following: Excavate the foundation trench to expose the crown beam, inspect the existing underground continuous wall to determine the location of the underground continuous wall defects, and perform grouting reinforcement on the locations of the existing underground continuous wall defects; Construct steel sheet pile components on one side of the existing underground continuous wall to form an anti-seepage interface; Precast piles are constructed on the other side of the existing underground continuous wall, and multiple rows of precast piles are arranged along the length of the existing underground continuous wall; Adjacent precast piles are connected by multiple rows of connecting components, and the connecting components are connected to the existing underground continuous wall; Construct waist beams on the side of the precast piles away from the existing underground continuous wall, with multiple rows of waist beams; Continue excavating downwards and repeat the construction of connecting components and waist beams until the designed bottom elevation of the foundation pit is reached; Anchor bars are reserved on the top side of the precast piles, which are connected to the main bars of the existing underground continuous wall. Concrete is poured on the top of the existing underground continuous wall and precast piles to form a crown beam.

7. A construction method for improving the lateral stiffness of an existing underground continuous wall according to claim 6, characterized in that: The steel sheet pile components are formed by overlapping a plurality of Larsen steel sheet piles in sequence, and a distance is set between the inner side of the Larsen steel sheet pile and the existing underground continuous wall.

8. A construction method for improving the lateral stiffness of an existing underground continuous wall according to claim 6, characterized in that: The existing underground ground-connected wall was inspected using the isotope tracer method combined with the core drilling method, including the following: Vertical drilling is performed in the soil on both sides of the existing underground diaphragm wall to form an isotope injection well on the outside of the existing underground diaphragm wall and an isotope monitoring well on the inside of the existing underground diaphragm wall; Isotopes are injected into the inner isotope injection well, and a gamma spectrometer is placed in the outer isotope monitoring well; Use gamma spectrometer to scan the existing underground diaphragm wall to find the leakage point location and determine the abnormal part of the existing underground diaphragm wall; After confirming the existence of abnormal parts in the existing underground continuous wall, the defective section is accurately located based on the detection data, and then core drilling is carried out on the top surface of the underground continuous wall in the corresponding area. By controlling the drilling and coring depth, the abnormal part is directly reached, and core samples are simultaneously extracted for physical verification.

9. A construction method for improving the lateral stiffness of an existing underground continuous wall according to claim 6, characterized in that: After the construction of the connecting member, the existing underground continuous wall is drilled through the first reserved hole of the precast pile, the first connecting pipe is inserted into the first reserved hole into the drilled hole of the existing underground continuous wall, and epoxy resin is poured; A second connecting pipe is implanted in the second reserved hole of the precast pile. The second connecting pipe is arranged beyond the side of the precast pile. The main reinforcement of the waist beam is laid through the second connecting pipes at multiple precast piles. The second connecting pipe and the main reinforcement of the waist beam are overlapped and welded, and then concrete is poured to form the waist beam.

10. A construction method for improving the lateral stiffness of an existing underground continuous wall according to claim 7, characterized in that: After the precast piles are sunk, grouting is performed through the grouting holes of the precast piles, so that the grout effectively penetrates and completely fills the soil between the existing underground continuous wall and the precast piles, thereby solidifying the cementitious body; If local areas are found where the contact surface density between the precast piles and the existing underground continuous wall is insufficient, wedge blocks shall be used to implement bidirectional tightening reinforcement between the precast piles and the existing underground continuous wall.

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