A waterproof reinforcing system for bored cast-in-place piles and a construction method thereof

Abstract

The application provides a waterproof reinforcing system for existing bored piles and a construction method, and relates to the field of waterproof reinforcing of existing support structures. In view of the problem that the strength of existing bored piles decreases after long-term service and the existing bored piles cannot be directly utilized, the existing bored piles are positioned according to the principle of first non-destructive and then slightly destructive, and the defects are positioned by combining low-strain method or acoustic wave transmission method with core drilling, and targeted cement grouting reinforcement is performed. The circular arc sections of the steel sheet piles are coaxially distributed with the existing bored piles, and adjacent steel sheet piles are spliced by buckles, so that the existing pile body does not need to be removed and the existing pile body does not need to be avoided. The grouting pipe is arranged between adjacent existing bored piles, cement slurry is injected therefrom, and a continuous cement grouting layer is formed after the slurry solidifies. The grouting layer can fill various joints and block the water seepage path, and can also form an integral anti-seepage system together with the steel sheet piles to replace the original water stop curtain, thereby effectively preventing the risk of pressure water leakage and piping, and solving the problem of failure of the existing waterproof system.

Description

Technical Field

[0001] This invention relates to the field of waterproofing and reinforcement of existing support structures, specifically to a waterproofing and reinforcement system and construction method for existing bored piles. Background Technology

[0002] With the deepening development of urban underground space, the close proximity construction between new projects and existing underground structures is increasingly common. In such projects, existing support structures (especially widely used bored piles) often occupy key spatial positions in new foundation pits. Completely demolishing existing piles not only presents challenges of high technical difficulty and construction risks but also generates a large amount of construction waste, violating the concept of green and sustainable development. Conversely, leaving abandoned piles buried long-term results in a permanent waste of underground space resources. Therefore, scientifically waterproofing and reinforcing existing bored piles and incorporating them into the support system of new foundation pits offers significant economic and environmental benefits. However, after long-term service or construction impacts, the existing support structure often fails to meet the requirements of new foundation pit support. Its seepage prevention function relies on the outer water-stop curtain, but during the excavation of new foundation pits, this water-stop curtain is often extensively damaged during earthwork operations, leading to the formation of a through-flow seepage channel at the pile-soil interface, causing the risk of pressurized water leakage or even piping.

[0003] Currently, there are some shortcomings in the treatment of existing support structures. If existing piles are avoided, the economic efficiency of development will be sacrificed. Existing piles will affect the scope of new foundation pits. If they are forcibly removed, vibration and disturbance will easily have an adverse effect on existing buildings. In addition, there are problems of high energy consumption and waste pollution. If they are used directly, the waterproofing system will fail after long-term service and will not meet the requirements of engineering reliability. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a waterproof reinforcement system and construction method for existing bored piles. The arc segment of the sheet pile is coaxially distributed with the existing bored pile, and adjacent sheet piles are spliced ​​together by snap-fit. An auxiliary support structure can be built on the outside of the existing pile without dismantling it, thus avoiding the construction risks, construction waste, and resource waste caused by dismantling.

[0005] The primary objective of this invention is to provide a waterproofing and reinforcement system for existing bored piles, employing the following approach: include: Steel sheet piles are provided with arc sections, and the two sides of the arc sections extend to form snap fasteners. Adjacent steel sheet piles are spliced ​​together in sequence through snap fasteners. The arc sections are coaxially distributed with the corresponding existing bored piles. Steel mesh is hung on the side of the steel sheet pile away from the existing bored piles and covered with shotcrete layer. Grouting pipes are arranged between adjacent existing bored piles, and the grout outputs grout to form a cement grouting layer between adjacent existing bored piles and between existing bored piles and sheet piles. The connecting key is a tubular structure distributed radially along the existing bored pile. One end is located outside the sheet pile, and the other end passes through the sheet pile and is embedded in the existing bored pile.

[0006] Furthermore, the sheet piles are distributed in a one-to-one correspondence with the existing bored piles, and multiple sheet piles are arranged sequentially along the distribution direction parallel to the existing bored piles, and are connected together by a waist beam.

[0007] Furthermore, the sheet pile is provided with multiple sets of reserved holes as connecting keys to pass through the holes. Each set of reserved holes includes multiple channels and a pre-set rubber sealing ring. Some connecting keys are located at one end outside the sheet pile to cooperate with the waist beam.

[0008] Furthermore, multiple grouting holes are provided on the circumferential sidewall of the connecting key to introduce epoxy resin and form an epoxy resin grouting layer. The grouting holes are connected to the opening at one end of the connecting key located outside the sheet pile. A waterproof rubber gasket is fitted to the other end of the connecting key located outside the sheet pile to seal it after grouting is completed.

[0009] Furthermore, one side of the arc segment is a first buckle, and the other side is a second buckle, which are inserted and locked together for sealing.

[0010] Furthermore, the horizontal cross-section of the sheet pile is Ω-shaped, and the same sheet pile is connected to an existing bored pile through multiple connecting keys.

[0011] The second objective of this invention is to provide a construction method for an existing waterproofing and reinforcement system for bored piles, wherein the construction of the existing waterproofing and reinforcement system for bored piles provided in the first objective includes: Clear surface obstacles and excavate the location of existing bored piles, remove existing capping beams and inspect existing bored piles, and repair them; Steel sheet piles are inserted sequentially into the existing bored piles on the side closest to the new foundation pit, and adjacent steel sheet piles are spliced ​​together. Grouting pipes are inserted between adjacent existing bored piles to output grout to form a cement grouting layer. A new crown beam is constructed on top of the existing bored piles, and a new foundation pit is excavated. The connecting key is constructed from one side of the steel pipe pile. After passing through the steel sheet pile and the cement grouting layer, the connecting key is implanted into the existing bored pile and grouting is performed through the connecting key. A steel mesh is installed on the side of the sheet pile away from the existing bored pile and shotcrete is sprayed to form a shotcrete layer.

[0012] Furthermore, during the excavation before removing the existing capping beam, excavation is carried out on one side along the axis of the existing bored piles to fully expose the existing capping beam, and then the existing capping beam and the pile top connection area are removed.

[0013] Furthermore, the detection of existing bored piles includes a combination of low-strain reflected wave method or sonic transmission method with core drilling, and the use of in-hole photography to determine the size and distribution characteristics of the defect interface of the existing bored piles, and repair accordingly.

[0014] Furthermore, cement grout is output through the grouting pipe to form a cement grouting layer, and epoxy resin grout is output through the connecting key to form an epoxy resin grouting layer.

[0015] Compared with the prior art, the advantages and positive effects of this invention are: To address the issue of weakened strength and inconvenience for direct use of existing bored piles after long-term service, a "no-damage first, then minimal-damage" approach is adopted. This involves combining low-strain reflected wave or sonic logging methods with core drilling, and using cement grout to specifically reinforce the defective areas. The arc segments of the sheet piles are coaxially distributed with the existing bored piles, and adjacent sheet piles are spliced ​​together using snap-fit ​​connections. This allows for the construction of a waterproof structure on the outside of the existing piles without dismantling them, avoiding the construction risks, construction waste, and resource waste associated with demolition. It also eliminates the need to avoid existing piles, making full use of underground space. Grouting pipes are placed between adjacent existing bored piles. Grout is injected into the gaps between existing bored piles and between existing bored piles and sheet piles through these pipes. After solidification, the grout forms a continuous cement grout layer. This cement grouting layer serves two purposes: firstly, it fills the gaps between the pile and the sheet pile, and between adjacent piles, blocking seepage channels; secondly, the cement grouting layer and the sheet pile form an integrated anti-seepage structure, replacing the damaged original water-stop curtain, effectively preventing the leakage of pressurized water, avoiding the risk of piping, and solving the problem of existing pile waterproofing system failure. Furthermore, tubular connecting keys are arranged radially along the existing bored piles, with one end embedded in the existing pile and the other end extending to the outside of the sheet pile, forming a rigid connection between the sheet pile and the existing pile, ensuring that both are subjected to stress in tandem. Simultaneously, multiple grouting holes are opened on the circumferential sidewalls of the tubular connecting keys for injecting epoxy resin and forming an epoxy resin grouting layer. This design can provide secondary grouting anti-seepage measures when cement grouting waterproofing using grouting pipes is not ideal (e.g., due to process defects or unexpected situations), further enhancing the overall anti-seepage performance.

[0016] By using the curvature adaptability design of Ω-shaped steel sheet piles and the three-dimensional synergistic force system of grouting reinforcement, the space utilization rate can be improved and the anti-seepage system can be reconstructed simultaneously without removing the existing piles. This not only significantly reduces the risk of disturbance during close-fitting construction by using modular assembly technology, but also transforms the existing piles into an organic component of the permanent support structure, achieving the green construction goal of minimizing resource consumption and reducing construction waste.

[0017] The unique arc design of the Ω-shaped steel sheet piles forms a natural geometric interlocking interface with the existing pile body, creating a closed seepage channel for high-pressure grouting and achieving deep healing and permanent sealing of micro-cracks between the new and old structures. Through the three-dimensional synergistic force system of grouting reinforcement, the new structure and the original pile body are transformed into a composite support body with significantly improved overall seepage resistance, fundamentally suppressing the structural deformation risk induced by leakage and providing a reliable guarantee for the green recycling of existing piles in close-construction environments. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a schematic diagram of a newly constructed foundation pit as described in the background section; Figure 2 This is a schematic diagram of the steel sheet pile assembly and the wainscoting in one or more embodiments of the present invention; Figure 3 This is a schematic diagram of the splicing of adjacent sheet piles in one or more embodiments of the present invention; Figure 4 This is a schematic diagram of a connection key in one or more embodiments of the present invention; Figure 5 This is a schematic diagram of the arrangement of bored piles and sheet piles in one or more embodiments of the present invention.

[0020] Figure 6 This is a schematic diagram showing the relative positions of existing bored piles and sheet piles in one or more embodiments of the present invention; Figure 7 This is a flowchart of one or more existing bored pile reinforcement construction methods of the present invention.

[0021] Among them, 1. Existing bored piles; 2. Existing capping beams; 3. Waist beams; 4. Steel sheet piles; 5. First connecting key; 6. Second connecting key; 7. First clip; 8. Second clip; 9. Connecting key; 10. First hole; 11. Second hole; 12. Existing subway station; 13. Soil layer; 14. Water-stop curtain; 15. Grouting pipe; 16. Auxiliary waist beam; 17. Waterproof rubber pad; 18. Cement grouting layer; 19. Shotcrete layer; 20. Steel mesh; 21. Epoxy resin grouting layer. Detailed Implementation

[0022] Example 1 In a typical embodiment of the present invention, such as Figures 1-7 As shown, a waterproofing and reinforcement system for existing bored piles is presented.

[0023] The reuse of existing bored piles during close-proximity construction presents difficulties, such as... Figure 1 As shown, when constructing a new foundation pit near the existing subway station 12, demolishing the existing piles presents challenges such as high technical difficulty, significant construction risks, and the generation of large amounts of construction waste. Retaining and burying them would waste underground space resources, making it difficult to balance economic efficiency and environmental protection. The existing piles are in poor condition after long-term service and cannot meet the bearing requirements for the support of the new foundation pit if used directly. The seepage prevention function of the existing piles relies on the outer water-stop curtain 14. When the new foundation pit is excavated, the water-stop curtain 14 is broken, and a through-seepage channel is formed at the pile-soil interface, which may lead to the risk of pressurized water leakage or even piping. Traditional solutions either avoid the project at the expense of economic efficiency, remove the piles to avoid vibration and pollution, or use the piles directly because the waterproofing fails and reliability cannot be guaranteed. Based on this, this embodiment provides a waterproof reinforcement system for existing bored piles, which is equipped with steel pipe piles and connecting keys 9. The arc segment of the steel sheet pile 4 is coaxially distributed with the existing bored pile 1, and adjacent steel sheet piles 4 are spliced ​​by snap-fit. A waterproof structure can be built on the outside of the existing pile without removing the existing pile body. The tubular connecting keys 9 are distributed radially along the existing bored pile 1, with one end embedded in the existing pile body and the other end located outside the steel sheet pile 4, forming a rigid connection between the steel sheet pile 4 and the existing pile body. The grouting pipe 15 is arranged between adjacent existing bored piles 1, and a cement grouting layer 18 is formed by grouting. The cement grouting layer 18 and the steel sheet pile 4 form an integrated anti-seepage structure, replacing the original water-stop curtain 14 that was destroyed, effectively preventing the leakage of pressurized water, avoiding the risk of piping, and solving the problem of failure of the existing pile waterproofing system.

[0024] like Figure 1 As shown in the figure, in this embodiment, the existing bored pile waterproofing and reinforcement system mainly includes sheet piles 4, grouting pipes 15 and connecting keys 9, with the sheet piles 4 and the existing bored piles 1 distributed at intervals.

[0025] The main body of the sheet pile 4 is an arc segment, with clips extending on both sides. Adjacent sheet piles 4 can be spliced ​​together sequentially through the clips to achieve continuous installation. The arc segment is coaxially distributed with the corresponding existing bored pile 1 to ensure a uniform gap between them. A steel mesh 20 is hung on the side of the sheet pile 4 away from the existing bored pile 1, and the steel mesh 20 is covered with a shotcrete layer 19. The shotcrete layer 19 and the steel mesh 20 together enhance the structural strength and impermeability of the sheet pile 4.

[0026] Grouting pipe 15 is arranged between adjacent existing bored piles 1. Its core function is to transport grout, so that the grout flows and solidifies between adjacent existing bored piles 1 and between existing bored piles 1 and sheet piles 4, and finally forms cement grouting layer 18, filling gaps and constructing a seepage prevention and load-bearing synergy system.

[0027] The connecting key 9 adopts a tubular structure and is radially distributed along the existing bored pile 1. One end is located outside the sheet pile 4, and the other end passes through the sheet pile 4 and is embedded inside the existing bored pile 1, serving to connect the sheet pile 4 and the existing bored pile 1 and realize the force transmission between them. At the same time, multiple grouting holes, such as the first hole 10 and the second hole 11, are opened on the circumferential sidewall of the connecting key 9 for injecting epoxy resin and forming an epoxy resin grouting layer 21. This design can provide secondary grouting seepage prevention measures when the waterproofing effect of the cement grouting layer 18 formed by cement grouting through grouting pipes is not ideal (such as due to process defects or unexpected situations), further enhancing the overall seepage prevention performance.

[0028] The arc segment of the sheet pile 4 is coaxially distributed with the existing bored pile 1, and adjacent sheet piles 4 are spliced ​​together by snap-fit. A waterproof structure can be constructed on the outside of the existing piles without dismantling them, avoiding the construction risks, construction waste, and resource waste associated with demolition. It also eliminates the need to avoid the existing piles, making full use of underground space and ensuring the economic viability of the new foundation pit development. The spliced ​​sheet piles 4 form a continuous vertical waterproof structure, initially improving the insufficient seepage prevention capacity caused by the damage to the water-stop curtain 14.

[0029] Tubular connecting keys 9 are radially distributed along the existing bored piles 1, with one end embedded in the existing pile body and the other end located outside the sheet piles 4, forming a rigid connection between the sheet piles 4 and the existing pile body. Multiple grouting holes, such as the first hole 10 and the second hole 11, are opened on its circumferential sidewalls to inject epoxy resin and form an epoxy resin grouting layer 21. This design provides a channel for secondary grouting for seepage prevention, effectively enhancing the overall seepage prevention performance.

[0030] Meanwhile, the steel mesh 20 hanging on the outside of the sheet pile 4 and the sprayed concrete layer 19 covering it enhance the structural strength of the sheet pile 4 itself, further improving the load-bearing reliability and waterproofing reliability of the entire waterproofing reinforcement system.

[0031] Grouting pipes 15 are arranged between adjacent existing bored piles 1. Grout is injected through the grouting pipes 15 into the gaps between the existing bored piles 1 and between the existing bored piles 1 and the sheet piles 4. After the grout solidifies, it forms a continuous cement grouting layer 18. This cement grouting layer 18 can fill the gaps between the piles and the sheet piles 4 and between adjacent piles, blocking the seepage channels. On the other hand, the cement grouting layer 18, together with the existing piles and sheet piles 4, forms an integrated anti-seepage structure, replacing the original water-stop curtain 14 that has been broken, effectively preventing the leakage of pressurized water, avoiding the risk of piping, and solving the problem of failure of the existing pile waterproofing system. At the same time, the cement grouting layer 18 can also enhance the bonding force between the existing piles and the sheet piles 4, helping to improve the stability of the overall structure.

[0032] The existing bored piles 1 do not need to be demolished, reducing demolition costs and construction time, avoiding the generation of large amounts of construction waste, and conforming to the concept of green and sustainable development. At the same time, there is no need to avoid the existing piles, making full use of underground space, improving the economic efficiency of new foundation pit development, and avoiding waste of space resources. Following the principle of "no damage first, then minimal damage", the defects are located by combining low strain method or sonic logging method with core drilling, and targeted cement grouting reinforcement is carried out, which significantly improves the problem of the decline in bearing capacity of bored piles due to long-term service. The existing pile and sheet pile 4 are coordinated in bearing through the connecting key 9. Multiple grouting holes, such as the first hole 10 and the second hole 11, are opened on the circumferential sidewall to provide a reliable channel for secondary grouting and seepage prevention. Combined with the reinforcement of the sheet pile 4 by the shotcrete layer 19, it effectively makes up for the lack of bearing capacity of the overall structure, improves the seepage prevention capacity of the overall structure, and the overall reinforcement system can meet the bearing and seepage prevention requirements of the new foundation pit support, ensuring the safety of the engineering structure. The grouting pipe 15 delivers grout to form a cement grouting layer 18, constructing a continuous and complete seepage prevention system. This replaces the original, damaged water-stop curtain 14, completely blocking the through-seepage channels at the pile-soil interface, effectively preventing the risk of pressurized water leakage and piping, and ensuring the reliability of the waterproofing system. The entire waterproofing and reinforcement system construction process does not require large-scale excavation and demolition work, avoiding vibration and disturbance to surrounding existing buildings, reducing the impact of construction on the surrounding environment, and improving the safety and controllability of close-fitting engineering construction.

[0033] Sheet piles 4 are distributed one-to-one with existing bored piles 1. Multiple sheet piles 4 are arranged sequentially along the pile body distribution direction and are connected to the lintel 3. Sheet piles 4 have multiple sets of pre-reserved holes for connecting keys 9 to pass through. Simultaneously, rubber sealing rings should be pre-installed in the pre-reserved holes of the sheet piles 4 to prevent grout from clogging the holes during grouting through the grouting pipe 15. Some connecting keys 9 are located at one end outside the sheet pile 4 to cooperate with the lintel 3. For example... Figure 2 and Figure 3 As shown, the connecting key 9 is divided into two types: one is used to connect the sheet pile 4 and the existing bored pile 1, which is the shorter first connecting key 5; the other is used to connect the waist beam 3, the sheet pile 4 and the existing bored pile 1, which is the longer second connecting key 6. Both the first connecting key 5 and the second connecting key 6 are tubular structures.

[0034] Existing waterproofing reinforcement structures are prone to insufficient overall stability due to the independent stress of a single pile. In this embodiment, the sheet piles 4 are distributed one-to-one with the existing bored piles 1 and connected by the lintel beam 3. This allows multiple existing bored piles 1 to form a unified support system through the sheet piles 4 and the lintel beam 3, preventing overload on a single pile. Specifically, the lintel beam 3 connects the dispersed sheet piles 4 in series with the existing piles, forming a transversely integrated load-bearing structure. When lateral earth pressure is generated during excavation, the force can be transferred through the lintel beam 3 to multiple piles and sheet piles 4, achieving uniform load distribution and further compensating for the bearing defects of existing piles after long-term service. Simultaneously, some connecting keys 9, in conjunction with the lintel beam 3, form a rigid force transmission path between the lintel beam 3, the sheet piles 4, and the existing piles, preventing force transmission gaps between the lintel beam 3 and the support structure, and improving overall bearing reliability. Multiple lintel beams 3 can be provided, such as... Figure 6 As shown, the auxiliary waist beam 16 can cooperate with the second connecting key 6.

[0035] like Figure 4 As shown, multiple first holes 10 are opened on the circumferential sidewall of the connecting key 9 as grouting holes, and a second hole 11 is set in the center as a grouting channel, which is connected to the opening at the outer end of the connecting key 9, so that epoxy resin can be introduced to form an epoxy resin grouting layer 21; a waterproof rubber gasket 17 is fitted at the outer end of the connecting key 9 to seal the opening after grouting.

[0036] It should be noted that in this embodiment, the connecting key 9 is radially distributed along the existing bored pile 1, which can pass through the sheet pile 4 and be implanted into the existing bored pile 1 with the shortest length, thus shortening the length of the connecting key 9 and ensuring the connection strength.

[0037] In this embodiment, epoxy resin grouting is performed through the grouting holes on the connecting key 9 to achieve secondary reinforcement. The grouting holes allow the epoxy resin to penetrate into the contact gaps between the connecting key 9 and the existing pile body and sheet pile 4. After curing, an epoxy resin grouting layer 21 is formed. On the one hand, it fills the tiny gaps to prevent the residue of seepage channels; on the other hand, it enhances the interface bonding force between the connecting key 9 and the pile body and sheet pile 4, improves the force transmission efficiency, and compensates for the interface defects after drilling and rebar installation in the existing pile body. At the same time, the waterproof rubber gasket 17 seals the outer opening of the connecting key 9 after grouting, which not only prevents epoxy resin loss but also prevents external water from seeping in through the opening of the connecting key 9. This forms a dual guarantee of grouting reinforcement combined with sealing and seepage prevention, solving the problem of seepage failure caused by the traditional connecting key 9 relying solely on mechanical cooperation.

[0038] The horizontal cross-section of the sheet pile 4 is Ω-shaped, such as... Figure 5 , Figure 6 As shown, one side of the arc segment has a first buckle 7 and the other side has a second buckle 8, which are inserted and locked together; the same steel sheet pile 4 is connected to the existing pile body through multiple connecting keys 9.

[0039] The Ω-shaped cross-section design allows the arc segment of the sheet pile 4 to better match the curvature of the existing pile body. Compared with ordinary arc structures, the gap is more uniform, providing a geometric basis for the continuous formation of the subsequent cement grouting layer 18 and avoiding the formation of weak points in the seepage prevention due to uneven gaps. The plug-in and sealing of the first clip 7 and the second clip 8 allows for gap sealing without additional sealing components when adjacent sheet piles 4 are spliced, preventing grout leakage from the splice. In addition, the same sheet pile 4 is connected to the existing pile body through multiple connecting keys 9, forming a multi-point force transmission, avoiding stress concentration caused by single-point connection, and further enhancing the cooperative stress stability of the sheet pile 4 and the existing pile body. It is especially suitable for local defect areas that may exist on the surface of the existing pile body, and disperses the stress risk through multi-point connection.

[0040] The snap-fit ​​splicing eliminates the need for complex fixing procedures, simplifying the installation process of the sheet piles 4. Pre-drilled holes provide precise access for the connecting key 9, avoiding delays and secondary damage to the piles caused by on-site drilling. The overall construction cycle is shortened by more than 30% compared to traditional reinforcement methods. The epoxy resin grouting layer 21 and the cement grouting layer 18 form a dual anti-seepage system. The former seals the interface gaps of the connecting key 9, while the latter fills the gaps between the pile and the sheet pile, and between piles themselves. Combined with the sealing effect of the waterproof rubber gasket 17, it effectively resists long-term groundwater erosion. The anti-seepage lifespan matches the service life of the foundation pit support, avoiding increased maintenance costs in the later stages.

[0041] The Ω-shaped cross-section and multiple connecting keys 9 design can adapt to existing bored piles 1 of different diameters. Furthermore, the multiple connecting keys 9 can flexibly avoid defective areas of existing piles, improving the system's adaptability to existing piles in different service conditions and expanding its application range. The waterproof rubber gasket 17 at the outer end of the connecting key 9 is detachable. If inspection or additional grouting is required later, the rubber gasket can be removed for operation without damaging the overall support structure, reducing maintenance difficulty and cost.

[0042] Example 2 In another typical embodiment of the present invention, such as Figures 1-7 As shown, a construction method for an existing waterproofing and reinforcement system for bored piles is presented, utilizing the existing waterproofing and reinforcement system for bored piles as described in Example 1.

[0043] A construction method for an existing bored pile reinforcement system includes: Clear the surface obstacles at the location of the existing bored pile 1 and excavate, remove the existing cap beam 2 and inspect the existing bored pile 1, and repair it; Steel sheet piles 4 are inserted sequentially on the side of the existing bored pile 1 closest to the new foundation pit, and adjacent steel sheet piles 4 are spliced ​​together. A grouting pipe 15 is inserted between adjacent existing bored piles 1 to output grout to form a cement grouting layer 18, and a new crown beam is constructed on top of the existing bored piles 1 and a new foundation pit is excavated. The connecting key 9 is constructed from one side of the sheet pile 4. After passing through the sheet pile 4 and the cement grouting layer 18, the connecting key 9 is inserted into the existing bored pile 1 and grouting is performed through the connecting key 9. A steel mesh 20 is installed on the side of the sheet pile 4 away from the existing bored pile 1 and shotcrete is sprayed to form a shotcrete layer 19.

[0044] Specifically, in combination Figures 1-7 Example 1 provides a detailed description of the construction method for the existing bored pile waterproofing and reinforcement system.

[0045] In urban construction scenarios involving close proximity, the existing support system faces severe challenges when a new foundation pit is excavated adjacent to an existing subway station 12. On the one hand, the excavation damages the existing cutoff wall 14 outside the existing support piles, creating seepage channels that threaten the safety of the new foundation pit. On the other hand, the existing bored piles 1 suffer from concrete deterioration and steel corrosion due to long-term service, resulting in significant degradation of structural performance. Under this high-risk environment, it is urgent to achieve the safe reuse of existing piles through collaborative reinforcement and seepage prevention technologies.

[0046] Step 1: Construction Preparation The following core tasks need to be prioritized during the project preparation phase: systematically assess the impact of surrounding projects and adjacent buildings; establish a multi-party drawing review group to verify design documents and complete technical briefings; scientifically develop construction organization plans and specialized technical solutions based on project characteristics and working conditions, and simultaneously obtain project positioning and elevation benchmarks; advance temporary water and power supply, road hardening, and production functional area layout; standardize the installation and commissioning of large machinery and implement three-level acceptance; strictly implement the "inspect before use" system for materials, verify quality assurance documents and conduct random sampling re-inspections, and establish a traceability mechanism. Before construction, a professional surveying team will conduct total station surveying and closure verification, establish a stable measurement benchmark network (prioritizing closed traverses) containing plane coordinates and elevation systems at different levels, and establish a mechanism for regular re-surveying (including after extreme weather) and pile point protection; the outward extension of the existing bored pile 1 edge line must be verified based on the inversion analysis of stratum parameters and deformation prediction models, and the design parameters will be dynamically adjusted in conjunction with survey data such as bearing strata and groundwater level.

[0047] The above steps can be performed using existing technology, and will not be described in detail here.

[0048] Step 2: Site preparation like Figure 1 As shown, after the construction site was leveled according to standard procedures, the top area of ​​the existing bored pile 1 was excavated according to the predetermined plan.

[0049] First, surface obstacles and loose soil (≥300mm) are removed. Depressions are backfilled with crushed stone and compacted in layers to a compaction degree ≥95%. A laser level is used to control the elevation difference within any 3m×3m area to ≤10mm. A total station is used to establish a reference network to ensure the horizontal deviation of the installation reference surface is ≤3% (areas exceeding this deviation are leveled with M10 mortar). This process eliminates terrain stress concentration (slope ≤0.5°), providing a foundation with ≤2mm alignment accuracy for the Ω-shaped sheet pile 4-connecting key 9 system and the existing bored pile 1, ensuring the test error of the support structure's collaborative load-bearing performance is ≤5%, fundamentally meeting the stringent requirements of the patented technology for foundation accuracy.

[0050] Secondly, excavation was carried out on one side along the axis of the existing bored pile 1 to fully expose the existing capping beam 2. Considering the geological characteristics, a construction process of zoned operation, layered excavation (each layer's depth within the effective range of the machinery), and staggered advancement was adopted, with simultaneous slope trimming to maintain the design slope. Excavation continued until the bottom of the trench reached 200mm below the baseline of the capping beam. This over-excavation accommodated subsequent construction needs and adjustment space for measurement errors; the actual final excavation elevation could be dynamically adjusted within a range of 200mm ± 50mm below the baseline based on geological conditions and structural requirements.

[0051] The entire excavation operation adopts a composite construction method, mainly using long-arm excavators and supplemented by manual slope trimming. By combining mechanized assembly line operations with precise manual operation, the excavation depth can be determined by those skilled in the art based on actual needs.

[0052] Step 3: Inspect and reinforce the existing bored pile 1. In this embodiment, the principle of "non-destructive testing first, followed by minimal-destructive testing" is strictly followed. The low-strain reflected wave method and the acoustic transmission method are used to jointly detect each existing bored pile 1. For the abnormal areas found, the core drilling method is used for location verification. Detection: The low-strain reflected wave method and acoustic transmission method can be implemented using existing technologies, and will not be elaborated further here. After confirming the structural anomaly of the existing bored pile 1, the defective section was first precisely located based on the detection data, and then core drilling was carried out on the top surface of the pile in the corresponding area. By controlling the drilling depth to reach the abnormal stratum, core samples were extracted simultaneously for physical verification. At the same time, a high-precision in-hole camera detection system was used to perform 360° panoramic scanning imaging along the drilling trajectory to conduct three-dimensional spatial positioning and quantitative analysis of hidden defects such as honeycomb, segregation zones, and through cracks in the concrete structure, accurately measuring the size and distribution characteristics of the defect interface, providing key decision-making basis for the structural safety rating and repair and reinforcement parameter design of the existing bored pile 1.

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

[0054] Reinforcement: After accurately locating the structural defects, high-pressure grouting repair technology is carried out based on the existing holes, cracks or in-situ core sampling channels on the top surface of the existing bored pile 1.

[0055] Specifically, grouting operations should prioritize utilizing existing core sampling holes as grouting channels. When there is spatial misalignment between existing holes and the defect area, a new hole must be drilled directly above the defect area. A dynamic inclinometer should be used to ensure the borehole axis accurately penetrates the defect before high-pressure grouting repair. For newly drilled grouting holes, a strict "drill-inspect-clean" triple control process should be implemented: after drilling, an in-hole imaging instrument is used to inspect the borehole wall integrity and target area reach; a gas-water mixed jet cleaning process is used to remove rock cuttings and mud; after cleaning, an interface modifier (such as a silane coupling agent) is injected to enhance the bonding strength between the new and old interfaces.

[0056] The specific method for grouting reinforcement is as follows: After precisely positioning the grouting conduit to the newly drilled or existing borehole, it is connected to a standardized high-pressure grouting unit to carry out the grouting operation. A pressure-flow dual-control management mechanism is used to precisely regulate the grouting parameters (pressure fluctuation ≤ ±5%, grout volume error < 3%), ensuring that the cement grout fully penetrates and completely fills the fracture network, ultimately forming a solidified cementitious body with high interfacial bonding strength. This systematically improves the overall load-bearing capacity and deformation coordination of the retaining structure. The high-pressure grouting equipment used is mature engineering equipment, which will not be elaborated upon here.

[0057] After grouting is completed, micro-expansion cement-based materials (or ordinary silicate cement mortar) should be used as the preferred material for sealing the grouting holes. Immediately after implementation, standardized curing processes should be carried out on the treated area in strict accordance with engineering technical standards to ensure the formation of a high-density, corrosion-resistant sealing body. Finally, the reinforcement effect was evaluated by "low strain reflection wave method + sonic transmission method re-inspection". For the still existing abnormal areas, a closed-loop treatment of "targeted core drilling verification → high pressure grouting repair" was carried out to form a four-in-one quality control system of "sealing-maintenance-verification-repair".

[0058] Step 4: Construction of Ω-shaped steel sheet piles like Figure 1 As shown, to ensure precise geometric alignment between the Ω-shaped sheet piles 4 and the existing bored piles 1, existing pile data is acquired using 3D laser scanning, and customized curvature steel plates (8-16mm thick) are generated through reverse modeling. Adjacent Ω-shaped sheet piles 4 form a continuous seepage-proof interface through a mechanical interlocking structure of "first clip 7 + second clip 8" (the connection effect of the Ω-shaped sheet piles 4 is shown in the figure). Figure 2 As shown in the figure, its self-locking angle and interference fit are optimized to withstand 0.4MPa water pressure without leakage. Those skilled in the art can adjust the dimensions of the sheet pile 4 according to engineering requirements to achieve adaptability to all working conditions.

[0059] During construction, positioning control was achieved using an adjustable hydraulic guide frame, which features multi-directional degree of freedom adjustment to dynamically adapt to spatial deviations in the existing pile positions. The positioning process strictly adhered to gap control standards, utilizing a laser positioning system to monitor the arc-shaped gap distribution in real time. This ensured a uniform and sealed assembly interface was formed between the Ω-shaped sheet pile 4 and the existing bored pile 1, laying the geometric foundation for subsequent coordinated stress and waterproofing systems.

[0060] The implantation operation employs a low-disturbance hydraulic jacking system for segmented pressing, with force-displacement dual-parameter linkage control ensuring construction safety. During pressing, drag-reducing grout is injected simultaneously to lower the skin friction at the pile-soil interface, and the pile's attitude is dynamically fed back through a real-time monitoring system. When monitoring data indicates a tendency for pile misalignment, the guide frame correction mechanism is immediately activated to adjust the pile's attitude, ensuring that the verticality deviation remains within a controllable threshold. This process, through dynamic optimization of mechanical parameters and integration of information-based construction, achieves efficient implantation while minimizing the risk of disturbance to the existing support structure and surrounding soil.

[0061] Step 5: Installation and construction of grouting pipe 15 Grouting holes were drilled vertically at intervals of 1.5 times the pile diameter in the joint area between the Ω-shaped steel sheet pile 4 and the existing bored pile 1. A sleeve valve grouting pipe 15 with a one-way valve was inserted, and bentonite was filled on the outside of the pipe wall to form a sealing ring. Segmented retreat grouting was implemented: in the initial stage, the main gap was filled with a pressure of 0.3~0.5MPa, and then the micro-density was strengthened by stabilizing the pressure at 0.8~1.2MPa for 10 minutes. The grouting process was monitored by dual parameters of flow rate and pressure until the grout overflowed from the adjacent hole, and finally a continuous cement grouting layer 18 anti-seepage body was formed.

[0062] It is understandable that the installation, construction, and grouting process of the grouting pipe 15 in this step can be carried out using existing processes, and will not be elaborated here.

[0063] Step 6: Construction of the cap beam A continuous cap beam with a cross-section of ≥600mm×800mm is installed on top of the composite support structure. HRB400 grade steel reinforcement is used as the skeleton, with the main reinforcement diameter ≥25mm and Ω-shaped steel sheet piles 4 running through it. The lap length of the new and old steel reinforcement is ≥40d and closed stirrups are welded. The steel template is precisely shaped by laser calibration (flatness deviation ≤2mm / 2m). C35 micro-expansion concrete (expansion agent dosage 8%-12%, restricted expansion rate ≥0.03%) is poured and vibrated in layers (thickness ≤500mm). It is covered and moisturized for ≥7 days, with a temperature gradient ≤15℃ / d. The demolding strength is ≥80% of the design value.

[0064] Step 7: Excavation of the foundation pit The foundation pit was excavated in layers and sections according to the pre-set plan, and completed layer by layer, which will not be described in detail here.

[0065] Step 8: Connect key 9 for installation like Figure 3 As shown, the main body of the connecting key 9 and the circumferentially distributed auxiliary grouting holes work together to construct a secondary grouting channel system. The connecting key 9 is configured in two specifications: the first connecting key 5 enables the Ω-shaped steel sheet pile 4 to be directly connected to the existing bored pile 1, and the second connecting key 6 penetrates the integrated waist beam 3 component to form a differentiated force transmission path.

[0066] The existing pile body is drilled with rebar anchoring channels through the pre-reserved holes of the Ω-shaped steel sheet pile 4, and two types of connecting keys 9 are implanted in different types: The first connecting key 5 directly fixes the Ω-shaped steel sheet pile 4 to the existing bored pile 1; the second connecting key 6 is used to anchor the Ω-shaped steel sheet pile 4, the waist beam 3 and the existing bored pile 1 at the location of the waist beam 3; all reserved holes are pre-installed with detachable steel cards with rubber ring seals to block grout backflow and ensure the smooth flow of the duct, thus constructing a three-level collaborative force transmission system.

[0067] After the installation of the 9-connector system, phased differentiated grouting is implemented: First connecting key 5 grouting: Immediately assess the quality of the cement grout layer formed by the first grouting - if there are defects, inject sufficient epoxy resin under high pressure through the first hole 10 and the second hole 11 to reinforce and form an epoxy resin grout layer 21; if the density meets the standard, inject a small amount of epoxy resin to seal the channel; Second connecting key 6 grouting: After the completion of the waist beam 3 structure, perform the same standard grouting process. All connecting keys 9 are fitted with waterproof rubber pads 17 on the outside, which couple with the grouting body to form an adaptive seepage prevention system during service life, ensuring the sealing performance of the composite support throughout its entire lifespan.

[0068] Step 9: Construction of sprayed concrete, wainscoting 3, and internal supports. A two-way Φ8, 150mm steel mesh 20 is hung on the outside of the Ω-shaped steel sheet pile 4. C25 fine stone concrete (single layer thickness ≤ 80mm, total thickness ≥ 100mm) is sprayed in layers using an air compressor jetting machine to form a sprayed concrete layer 19. At the design elevation of the waist beam 3, the Ω-shaped steel sheet pile 4 and the existing bored pile 1 are penetrated through the second connecting key 6 (anchorage depth ≥30d). An adjustable template (flatness ≤3mm / 2m) is erected using the second connecting key 6 to pour C35 micro-expansion concrete (expansion agent dosage 10%±2%) to construct a closed rigid force transmission ring waist beam 3; and grouting is carried out according to the grouting requirements of the first connecting key 5. Repeat the above procedures until the designed elevation of the pit bottom is reached.

[0069] Step 10: Main Structure Construction The main structure construction will proceed according to the pre-designed plan, which will not be elaborated upon here.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waterproofing and reinforcement system for existing bored piles, characterized in that, include: Steel sheet piles are provided with arc sections, and the two sides of the arc sections extend to form snap fasteners. Adjacent steel sheet piles are spliced ​​together in sequence through snap fasteners. The arc sections are coaxially distributed with the corresponding existing bored piles. Steel mesh is hung on the side of the steel sheet pile away from the existing bored piles and covered with shotcrete layer. Grouting pipes are arranged between adjacent existing bored piles, and the grout outputs grout to form a cement grouting layer between adjacent existing bored piles and between existing bored piles and sheet piles. The connecting key is a tubular structure that is radially distributed along the existing bored pile. One end is located outside the sheet pile, and the other end passes through the sheet pile and is embedded in the existing bored pile. Multiple grouting holes are provided on the circumferential sidewall of the connecting key to introduce epoxy resin and form an epoxy resin grouting layer. The grouting holes are connected to the opening at one end of the connecting key located outside the sheet pile. A waterproof rubber gasket is fitted to the other end of the connecting key located outside the sheet pile to seal it after grouting is completed.

2. The existing bored pile waterproofing and reinforcement system as described in claim 1, characterized in that, The sheet piles are distributed in a one-to-one correspondence with the existing bored piles. Multiple sheet piles are arranged sequentially along the distribution direction parallel to the existing bored piles and are connected together by a waist beam.

3. The existing waterproofing and reinforcement system for bored piles as described in claim 2, characterized in that, The sheet pile has multiple sets of reserved holes as connecting keys to pass through. Each set of reserved holes includes multiple channels and a pre-set rubber sealing ring. Some connecting keys are located at one end outside the sheet pile to cooperate with the waist beam.

4. The existing waterproofing and reinforcement system for bored piles as described in claim 1, characterized in that, One side of the arc segment has a first buckle, and the other side has a second buckle. The first buckle and the second buckle are inserted and locked together for sealing.

5. The existing waterproofing and reinforcement system for bored piles as described in claim 4, characterized in that, The horizontal cross-section of the sheet pile is Ω-shaped, and the same sheet pile is connected to the existing bored pile through multiple connecting keys.

6. A construction method for an existing waterproofing and reinforcement system for bored piles as described in any one of claims 1-5, characterized in that, include: Clear surface obstacles and excavate the location of existing bored piles, remove existing capping beams and inspect existing bored piles, and repair them; Steel sheet piles are inserted sequentially into the existing bored piles on the side closest to the new foundation pit, and adjacent steel sheet piles are spliced ​​together. Grouting pipes are inserted between adjacent existing bored piles to output grout to form a cement grouting layer. A new crown beam is constructed on top of the existing bored piles, and a new foundation pit is excavated. The connecting key is constructed from one side of the steel pipe pile. After passing through the steel sheet pile and the cement grouting layer, the connecting key is implanted into the existing bored pile and grouting is performed through the connecting key. A steel mesh is installed on the side of the sheet pile away from the existing bored pile and shotcrete is sprayed to form a shotcrete layer.

7. The construction method of the existing bored pile waterproofing and reinforcement system as described in claim 6, characterized in that, When excavating before removing the existing capping beam, excavate on one side along the axis of the existing bored piles to fully expose the existing capping beam, and then remove the existing capping beam and the area connecting the pile top.

8. The construction method of the existing bored pile waterproofing and reinforcement system as described in claim 6, characterized in that, The detection of existing bored piles includes a combination of low-strain reflected wave method or sonic transmission method and core drilling, and the use of in-hole photography to determine the size and distribution characteristics of the defect interface of the existing bored piles, and repair accordingly.

9. The construction method of the existing bored pile waterproofing and reinforcement system as described in claim 6, characterized in that, Cement grout is delivered through grouting pipes to form a cement grouting layer, and epoxy resin grout is delivered through connecting keys to form an epoxy resin grouting layer.

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