Combined pile supporting system with built-in grouting anti-seepage and construction method thereof

Abstract

The application discloses a combined pile supporting system with built-in grouting anti-seepage and a construction method thereof, and relates to the technical field of foundation pit supporting. The system comprises alternatingly arranged steel piles and steel sheet piles, and inner and outer layer lock buckles are arranged on the two sides of each steel sheet pile. A lock buckle piece is fixedly connected to the two ends of the first flange of each steel pile. The inner and outer layer lock buckles are respectively buckled with the first and second buckle parts of the lock buckle piece, and a grouting cavity is formed by the buckling. The steel pile is provided with a transverse flow guide channel crossing the web, and the two ends of the channel are respectively connected with the grouting cavities at the two ends of the first flange. The double-layer buckling is beneficial to limiting the relative separation of adjacent components and keeping the shape of the grouting cavity stable. During construction, grouting is performed on the connected cavities to fill and block the lock part. The application is beneficial to improving the lock water stop reliability, reducing the operation demand of independent grouting, reducing the construction burden of subsequent leakage remediation and additional disturbance to the surrounding soil.

Description

Technical Field

[0001] This invention relates to the field of foundation pit support technology, and in particular to a combined pile support system with built-in grouting anti-seepage and its construction method. Background Technology

[0002] In underground engineering construction, it is usually necessary to set up a retaining structure around the foundation pit to withstand lateral water and soil pressure and restrict groundwater infiltration into the pit. For sites with high groundwater levels, confined water, or sand layers, the retaining structure must not only meet the requirements for bearing capacity and deformation control, but also meet the corresponding water-stopping requirements to ensure the safety of the foundation pit construction and the surrounding environment.

[0003] A support system combining steel sections and sheet piles is a type of foundation pit retaining structure. In this system, steel sections and sheet piles are alternately arranged along the outline of the foundation pit, with adjacent components connected by interlocking joints to form a continuous retaining wall. The steel sections and sheet piles jointly provide soil retention and support, while the sheet piles and their connections achieve water stoppage. To improve the water stoppage effect, sealing material can be embedded into the interlocking joints before pile driving, or a cement-soil water-stop curtain can be installed depending on the project conditions.

[0004] However, under conditions such as confined water or thick sand layers, leakage may still occur at the interlocking points of some existing composite pile support systems. The water-stopping effect may not meet the usage requirements under these conditions, and in severe cases, it may be accompanied by sand inrush, affecting the safety of foundation pit construction. Remedial measures such as external grouting after leakage occur may increase construction steps, extend the construction period, and increase construction costs, while also causing additional disturbance to the surrounding soil. For foundation pits adjacent to existing buildings or underground facilities, related remedial operations are also limited by construction space and surrounding deformation control requirements.

[0005] Therefore, how to improve the water-stopping reliability of the interlocking joint of the composite pile support system and reduce the construction burden and environmental impact of leakage repair work is a technical problem that needs to be solved in this field. Summary of the Invention

[0006] The present invention aims to provide a combined pile support system with built-in grouting anti-seepage and its construction method to solve the above-mentioned technical problems.

[0007] In a first aspect, the present invention provides a combined pile support system with built-in grouting and seepage prevention, comprising steel piles and sheet piles arranged alternately along the contour of the foundation pit. The steel piles have a web and a first flange and a second flange respectively connected to both sides of the web. Each side of the sheet pile is provided with an inner locking and an outer locking that are fixedly connected to each other. Each end of the first flange is fixedly connected with a locking member, which has a first engaging part and a second engaging part. The inner locking is engaged with the first engaging part, and the outer locking is engaged with the second engaging part. The inner locking and the first engaging part enclose a grouting cavity, and the outer locking and the second engaging part enclose another grouting cavity. Both grouting cavities are closed circumferentially and extend along the length of the pile. The steel piles are provided with a transverse flow channel that spans the web, and the two ends of the transverse flow channel are respectively connected to the grouting cavities at both ends of the first flange.

[0008] In one possible implementation of the first aspect, the engagement opening of the inner locking buckle faces the same direction as the engagement opening of the outer locking buckle, and the two grouting cavities are respectively located on both sides of the fixed connection portion of the inner locking buckle and the outer locking buckle.

[0009] In one possible implementation of the first aspect, both grouting cavities are provided with water-swellable sealing strips that run along the length of the pile.

[0010] In one possible implementation of the first aspect, each of the two grouting cavities has a grouting interface at its top that communicates with its interior.

[0011] In one possible implementation of the first aspect, the transverse flow channel includes a flow hole penetrating the web along the thickness direction and two drainage pipes, the two drainage pipes respectively connecting the two ends of the flow hole to the grouting cavities at both ends of the first flange.

[0012] In one possible implementation of the first aspect, the inner locking buckle and the first fastening part are provided with elastic clamping members at intervals along the pile length direction. The elastic clamping members are clamped between the first fastening part and the inner locking buckle to restrict the steel sheet pile and the steel pile from moving relative to each other in the lateral direction.

[0013] In one possible implementation of the first aspect, a split-type friction-reducing isolation sleeve is fitted around the outer periphery of the steel pile, and a lubricating grout channel extending along the length of the pile is formed between the friction-reducing isolation sleeve and the outer surface of the steel pile. A one-way grouting valve is provided at the bottom end of the steel pile, and the one-way grouting valve is connected upward to the lubricating grout channel.

[0014] In one possible implementation of the first aspect, the steel piles include long steel piles and short steel piles, the long steel piles and the short steel piles are arranged alternately along the outline of the foundation pit and have the same top elevation, the bottom of the long steel piles is lower than the bottom of the short steel piles, and the sheet piles adopt a uniform pile length.

[0015] Secondly, the present invention provides a construction method for a combined pile support system with built-in grouting anti-seepage, comprising: S1. Press the steel pile into the design elevation, wherein the steel pile has a web and a first flange and a second flange respectively connected to both sides of the web, and a locking member is fixed to each end of the first flange. The locking member has a first fastening part and a second fastening part. A transverse guide channel is provided on the steel pile across the web. S2. Press the sheet pile into the design elevation. Each side of the sheet pile is provided with an inner locking and an outer locking that are fixed to each other. The inner locking is engaged with the first locking part, and the outer locking is engaged with the second locking part. The inner locking and the first locking part form a grouting cavity, and the outer locking and the second locking part form another grouting cavity. Both grouting cavities are closed circumferentially and extend along the length of the pile. The two ends of the transverse guide channel are respectively connected to the grouting cavities at both ends of the first flange. S3. Grout is injected into one of the grouting cavities connected by the transverse guide channel from the top of the grouting cavity, so that the grout flows through the transverse guide channel into the other grouting cavity connected by the transverse guide channel; S4. Use the return grout from the top of the other grouting cavity as the criterion for determining whether the grouting is in place, and stop grouting.

[0016] In one possible implementation of the second aspect, the grouting from the top of one of the grouting cavities connected by the transverse guide channel into the grouting cavity includes: grouting into the grouting cavity at a first pressure; after grouting at the first pressure is completed, grouting into the grouting cavity at a second pressure greater than the first pressure; and after grouting at the second pressure is completed, grouting into the grouting cavity at a third pressure greater than the second pressure.

[0017] Beneficial technical effects of the present invention: This invention utilizes the inner and outer locking mechanisms of the sheet pile to engage with the first and second engaging parts of the locking components on the steel pile, respectively. This creates two connection constraints at the locking joint, which helps limit the relative separation of adjacent components and maintain the stability of the grouting cavity. The two engagements enclose a circumferentially closed grouting cavity that extends along the pile length, providing space for grout to be transported and filled along the pile length at the locking joint. This allows for the formation of two sealing areas after grouting, improving the continuity and reliability of the locking joint sealing. Simultaneously, a transverse flow channel connects the grouting cavities at both ends of the first flange of the steel pile, enabling grout to be transported from one cavity to the connected cavity at the other, reducing the need for separate grout supply and simplifying the grouting operation. The combined structure provides conditions for seepage prevention treatment at the locking joint, reducing the need for subsequent external remediation due to leakage at the locking joint, alleviating related construction burdens, and minimizing additional disturbance to the surrounding soil. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below show some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a combined pile support system provided in an embodiment of the present invention; Figure 2a This is a schematic diagram of steel piles and sheet piles arranged alternately along the contour of the foundation pit in the combined pile support system provided in an embodiment of the present invention. Figure 2b for Figure 2a Schematic diagram of the connection between medium-sized steel piles and steel sheet piles; Figure 2c for Figure 2b A schematic diagram of steel sheet piles; Figure 3 This is a schematic cross-sectional view of the foundation pit support provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the transverse flow guiding channel structure provided in an embodiment of the present invention; Figure 5 A partial longitudinal section schematic diagram of the arrangement of the elastic clamping members provided in an embodiment of the present invention; Figure 6 This is a schematic diagram showing the distribution of the friction-reducing isolation sleeve and the one-way grouting valve provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the construction method of the combined pile support system provided in an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: In the diagram: 10-Steel pile; 11-Web plate; 12-First flange; 13-Second flange; 14-Locking element; 15-First locking part; 16-Second locking part; 20-Sheet pile; 21-Inner locking; 22-Outer locking; 23-Fixing part; 31-First grouting cavity; 32-Second grouting cavity; 33-Water-swellable sealing strip; 34-Grouting interface; 40-Transverse guide Flow channel; 41-Guide hole; 42-Drainage pipe; 50-Elastic clamping component; 60-Friction-reducing isolation sleeve; 61-Lubricating slurry channel; 62-One-way grouting valve; 63-Relief groove; 70-Long steel pile; 71-Short steel pile; 72-Jet jet grouting expansion section; 80-Cement-soil water-stop curtain; 81-High dosage section; 82-Low dosage section; 90-Precast pressure top beam; 100-Foundation pit. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0023] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0024] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0025] This invention provides a combined pile support system with built-in grouting for seepage prevention. The combined pile support system includes steel piles 10 and sheet piles 20 arranged alternately along the contour of the foundation pit 100. Specifically, along the contour of the foundation pit 100, the piles are arranged in sequence as steel piles 10, sheet piles 20, steel piles 10, sheet piles 20… Each sheet pile 20 is connected to one steel pile 10 on each side, and each steel pile 10 is connected to one sheet pile 20 on each side, thus forming a continuous wall extending along the contour of the foundation pit 100.

[0026] For ease of explanation of orientation, the pile length direction referred to in this embodiment refers to the direction in which each component extends along the depth, the transverse direction refers to the horizontal direction perpendicular to the pile length direction, the locking joint refers to the gap between the sheet pile 20 and the steel pile 10 at the part where they interlock, and the interlocking pair refers to the whole formed by the sheet pile 20 and the steel pile 10 interlocking at one end of the first flange 12.

[0027] The steel pile 10 has a web 11 and a first flange 12 and a second flange 13 respectively connected to both sides of the web 11. The steel pile 10 can be, for example, an H-beam, an I-beam, or a composite section steel section welded from steel plates; any type with a web and two flanges connected to both sides of the web is acceptable. The sheet pile 20 can be, for example, a U-shaped sheet pile, a Z-shaped sheet pile, or a straight-web sheet pile; any type with interlocking joints on both sides is acceptable.

[0028] The sheet pile 20 has an inner locking buckle 21 and an outer locking buckle 22 fixedly connected to each other on both sides. In this embodiment, the inner locking buckle 21 is the original locking opening integrally rolled during the hot rolling process of the sheet pile 20, located at the end of this side of the sheet pile 20; in other implementations, the inner locking buckle 21 can also be a locking profile manufactured independently and fixedly connected to the end of the side of the sheet pile 20. The outer locking buckle 22 is located on the side of the inner locking buckle 21 away from the body of the sheet pile 20, that is, after assembly, it is located on the side of the inner locking buckle 21 facing the web plate 11, and is fixedly connected to the inner locking buckle 21 at the fixed connection part 23; in this embodiment, the outer locking buckle 22 is an independently manufactured locking profile, welded to the inner locking buckle 21 along the entire length of the pile; in other implementations, the outer locking buckle 22 can also be integrally rolled with the inner locking buckle 21, in which case the integral transition section between the two constitutes the fixed connection part 23. In this embodiment, the inner and outer layers refer to the body of the sheet pile 20: the inner layer lock 21 is closer to the body of the sheet pile 20 than the outer layer lock 22, while the outer layer lock 22 is closer to the web 11 of the steel pile 10 than the inner layer lock 21.

[0029] The term "fixed connection" in this embodiment refers to a connection that prevents relative displacement between the connected components, including but not limited to continuous fillet welds along the entire length of the pile and integral rolling. All fixed connections mentioned below can be implemented using any of the methods described above.

[0030] Each end of the first flange 12 is fixedly connected to a locking member 14, which has a first engaging portion 15 and a second engaging portion 16. In this embodiment, the second flange 13 is a straight flange without locking members. Since the steel pile 10 itself is a straight flange and does not have a factory-installed locking lug, the locking member 14 is fixedly connected to the end of the first flange 12; and the first engaging portion 15 and the second engaging portion 16 are formed on the same locking member 14, so two connections can be established simultaneously with one insertion action.

[0031] The inner locking buckle 21 engages with the first engaging part 15, and the outer locking buckle 22 engages with the second engaging part 16. In this embodiment, the grouting cavity formed between the inner locking buckle 21 and the first engaging part 15 is called the first grouting cavity 31, and the grouting cavity formed between the outer locking buckle 22 and the second engaging part 16 is called the second grouting cavity 32. Both the first grouting cavity 31 and the second grouting cavity 32 are circumferentially closed and extend along the length of the pile. The term "circumferentially closed" means that the cross-sectional outline of the grouting cavity is formed by the wall surfaces of the inner locking 21 and the first interlocking part 15, or by the wall surfaces of the outer locking 22 and the second interlocking part 16, which are connected end to end. There are no lateral openings on the cross-section, so the grout in the cavity will not leak outward from the side seams under normal pressure, and the cavity can establish and maintain grouting pressure. The term "through-the-pile-length" means that the grouting cavity is not interrupted from its top to its bottom, so the grout injected from a single point at the top can fill the entire depth along the pile length.

[0032] The steel pile 10 is also provided with a transverse flow channel 40 spanning the web 11. The two ends of the transverse flow channel 40 are respectively connected to the second grouting cavities 32 at both ends of the first flange 12. Since the two locking members 14 are located at both ends of the first flange 12, the two interlocking pairs are located on both sides of the web 11, and the web 11 is located between the two interlocking pairs. The transverse flow channel 40 spanning the web 11 can change the second grouting cavities 32 on both sides of the web 11 from being isolated to being interconnected.

[0033] The coordination relationships of the above-mentioned combined pile support system under service conditions are as follows.

[0034] During the process of inserting the sheet pile 20 from top to bottom along the length of the pile and pressing it to the design elevation, the inner locking 21 and the first locking part 15, and the outer locking 22 and the second locking part 16 respectively engage in place, and the first grouting cavity 31 and the second grouting cavity 32 are formed on the spot at the locking joint.

[0035] While forming the cavity, a lateral constraint is also established at the interlocking point. Under the influence of grouting pressure, pile driving deviation, and the difference in water and soil pressure inside and outside the pit, there is a tendency for the sheet pile 20 and the steel pile 10 to separate laterally. The interlocking of the inner locking 21 with the first interlocking part 15 constrains this relative separation from the side away from the web plate 11, and the interlocking of the outer locking 22 with the second interlocking part 16 constrains this relative separation from the side closer to the web plate 11. The two interlocking points together restrict the sheet pile 20 from opening relative to the steel pile 10. Because the interlocking joint does not open, the cross-sections of the first grouting cavity 31 and the second grouting cavity 32 remain closed and do not lose pressure under the action of grouting pressure.

[0036] After the cavity is formed and kept closed under interlocking constraints, the grouting operation can begin. Grout is injected from the top of the second grouting cavity 32 at one end of the first flange 12, filling downwards along the cavity and flowing through the transverse guide channel 40 across the web 11 into the second grouting cavity 32 at the other end of the first flange 12, before returning upwards from that cavity. Therefore, a single injection can sequentially fill the injection end cavity, the transverse guide channel 40, and the other end cavity, eliminating the need for separate grouting at each interlock.

[0037] Regarding the seepage prevention interface of the same interlocking pair, the first grouting cavity 31 and the second grouting cavity 32 are independent of each other and not connected. If the seepage is to penetrate from outside the pit to inside the pit, it must pass through two cavities that are filled tightly in sequence. Even if the sealing of one cavity is partially damaged, the other cavity remains intact.

[0038] Based on the above structure and coordination, it can be deduced that the main effect of this embodiment is to transform the originally open and unpressure-bearing interlock gaps into pressure-bearing closed cavities, allowing the seepage prevention and reinforcement of the interlock to be completed on-site at the interlock, eliminating the need for a separate water-cutting curtain outside the foundation pit or high-pressure grouting outside the pit to plug leaks after leakage, thereby avoiding secondary disturbance to the surrounding soil. Furthermore, the cavities at both ends of the same steel pile are interconnected via the transverse diversion channel 40, allowing for continuous filling of the entire span of interlock gaps with a single-point injection, reducing the need for grouting through individual interlocks.

[0039] It should be noted that the cross-sectional shape of the above-mentioned components and the specific matching form between the locking member 14 and the steel sheet pile 20 can be adjusted according to the engineering conditions, and the embodiments of the present invention do not limit this.

[0040] Based on the above specific implementation, the relative posture of the inner locking buckle 21 and the outer locking buckle 22, as well as the relative position of the two grouting cavities, can be set as follows.

[0041] See Figures 2a to 2cThe inner locking buckle 21 and the outer locking buckle 22 have the same opening orientation. The first grouting cavity 31 and the second grouting cavity 32 are located on both sides of the fixed connection portion 23 of the inner locking buckle 21 and the outer locking buckle 22, respectively. Correspondingly, the first locking portion 15 and the second locking portion 16 on the locking member 14 also have the same opening orientation, and are opposite to the opening orientation of the inner locking buckle 21 and the outer locking buckle 22, so that they hook and fasten in pairs.

[0042] The openings of the fasteners face the same direction, which has an effect on both assembly and cavity formation.

[0043] In terms of assembly, since the inner locking buckle 21 and the outer locking buckle 22 have the same opening orientation, their alignment with the first locking part 15 and the second locking part 16 is consistent. The sheet pile 20 only needs to be inserted downwards along the pile length direction, and the two connections are completed simultaneously in the same insertion action, without the need for separate alignment of the two connections.

[0044] In the cavity formation, the two interlocking points 23 are located on opposite sides of each other, independent of each other, rather than connected end-to-end to form a longer interlocking path. Therefore, each interlocking point encloses a separate grouting cavity. The interlocking point 23 acts as a common partition between the two cavities, ensuring that each cavity is circumferentially closed and unconnected, allowing for separate filling and pressure bearing, forming two independent sealing interfaces. The cross-sectional shape of both the inner interlocking point 21 and the outer interlocking point 22 is, for example, C-shaped.

[0045] After the aforementioned interlocking pairs define two grouting cavities, the internal configuration of the cavities and their end interfaces can be configured as follows. Since both directions revolve around the grouting cavities, they will be described together.

[0046] See Figures 2a to 2c Both the first grouting cavity 31 and the second grouting cavity 32 are provided with water-swellable sealing strips 33 extending along the length of the pile. The water-swellable sealing strips 33 are, for example, water-swellable rubber strips with a rectangular cross-section, for example, 18mm × 20mm. They are pre-installed along the entire length of the interlocking surfaces of the inner locking strip 21 and the outer locking strip 22 before the locking member 14 is assembled with the sheet pile 20. Correspondingly, the equivalent inner diameter of the cross-section of each grouting cavity is, for example, 25mm to 35mm. The equivalent inner diameter is calculated as the diameter of a circle with a cross-sectional area equal to the clear area of ​​the cavity, and the value is preferably chosen to accommodate the water-swellable sealing strip 33 while leaving a grout flow section around it. The above dimensions are examples and can be adjusted according to the locking specifications of the selected sheet pile 20 and the profile specifications of the locking member 14, and do not constitute a limitation of the present invention.

[0047] The closed contour of the cavity accommodates the water-swellable sealing strip 33 within it. The sealing strip is separated from the surrounding sand by the cavity wall, so it does not come into contact with the sand during pile driving and is thus preserved intact until grouting. After groundwater seeps into the cavity, the water-swellable sealing strip 33 absorbs water and expands, squeezing out the remaining voids in the cavity and sealing the tiny leakage channels. One strip is installed in each of the two cavities, thus forming two independent expansion sealing interfaces along the seepage path.

[0048] The top of each of the first grouting cavity 31 and the second grouting cavity 32 is provided with a grouting interface 34 that communicates with the grouting cavity. Since each grouting cavity extends along the length of the pile, its top is itself an open opening. The grouting interface 34 is, for example, this open opening. It can also be a short pipe joint welded to the top of the steel pile 10 or the top of the sheet pile 20 and communicating with the interior of the corresponding cavity. The short pipe joint can also be equipped with a valve or quick connector for connection to the grouting pipeline. Since there is an interlocking pair at each end of the first flange 12, and each interlocking pair encloses two cavities, a total of four grouting interfaces 34 are provided around the perimeter of a single steel pile 10.

[0049] After setting the grouting interface 34, the grouting operation and grout return observation are both carried out at the pile top position on the ground: grout is injected from one of the grouting interfaces 34, and grout return is observed from the other grouting interface 34, without having to go down to the buried part to judge the filling status.

[0050] The above implementation methods illustrate how a single interlocking pair can enclose two grouting cavities. As for how the cavities at both ends of the first flange 12 are connected, there are various possible configurations; one is described below. This direction is crucial for achieving continuous filling of the entire span through single-point injection in this embodiment, and therefore will be explained in detail below.

[0051] See Figure 4 The transverse flow channel 40 includes a flow hole 41 that penetrates the web 11 along the thickness direction and two drainage pipes 42. The two drainage pipes 42 are respectively connected to the two ends of the flow hole 41 and the two ends of the first flange 12, and the second grouting cavity 32.

[0052] The guide hole 41 penetrates the web 11 along the thickness direction, thereby connecting the two spaces enclosed by the first flange 12 and the web 11 on both sides of the web 11. The diameter of the guide hole 41 is, for example, 15mm to 30mm, or 20mm. Only one guide hole 41 can be provided along the pile length, or multiple guide holes 41 can be provided at intervals, with a spacing of, for example, 1.5m to 3.0m, or 2.0m. The guide hole 41 is located, for example, near the intersection of the first flange 12 and the web 11, thus shortening the length of the drainage pipe 42. The diameter of the guide hole 41 is much smaller than the height of the web 11, and its interval arrangement along the pile length limits the weakening of the shear section of the web 11; the arrangement height of the guide hole 41 can also avoid the depth section with large pile shear force, or a reinforcing ring plate can be welded around the hole to compensate for the weakened section.

[0053] The reason why the web plate 11 is chosen as the object to be crossed in this embodiment is that the two drainage pipes 42 are laid along the surface of the first flange 12 toward the second flange 13. This surface is located in the groove between the two flanges of the steel pile 10. The drainage pipes 42 are arranged in this position to reduce the portion protruding outside the steel pile 10. When combined with the friction-reducing isolation sleeve 60 described later, the sleeve provides corresponding isolation protection. The web plate 11 is right across the middle of this path, so a guide hole 41 must be opened on the web plate 11 to allow it to pass through.

[0054] In this embodiment, the drainage pipe 42 is a closed steel pipe, laid and welded along the surface of the first flange 12 toward the second flange 13. One end of the drainage pipe 42 is welded to the orifice of the guide hole 41, and the other end is welded to the pre-made grout guide hole on the locking member 14. The grout guide hole passes through the wall of the second fastening part 16 and enters the second grouting cavity 32, thereby connecting the internal space of the second grouting cavity 32 with the second grouting cavity 32 at the other end of the first flange 12 via the drainage pipe 42, the guide hole 41, and another drainage pipe 42. The drainage pipe 42 only enters the second grouting cavity 32 from one side of the locking member 14 without touching the outer locking 22 because the sheet pile 20 is inserted into the position from top to bottom along the locking member 14, and the drainage pipe 42 pre-installed on the steel pile 10 cannot pass through the wall of the outer locking 22 inserted together with the sheet pile 20. The reason for setting the drainage pipe 42 between the guide hole 41 and the second grouting cavity 32 is that the second grouting cavity 32 is located at the end of the first flange 12 and the guide hole 41 is located at the web 11. The distance between the two is about half the flange width. Simply opening a through hole on the web 11 cannot lead the grout from the orifice to the cavity.

[0055] It should be noted that although a partial opening is formed where the grout guide orifice enters the second grouting cavity 32, this opening connects to the inner cavity of the equally closed drainage pipe 42. The second grouting cavity 32 and the drainage pipe 42 together constitute a closed pressure-bearing system. Therefore, the state of the second grouting cavity 32 being closed circumferentially and capable of withstanding grouting pressure is not changed.

[0056] The inner cavity of the drainage pipe 42 is isolated from the lubricating slurry channel 61 between the friction-reducing isolation sleeve 60 and the steel pile 10. The friction-reducing isolation sleeve 60 is a split sleeve fitted around the outer periphery of the steel pile 10. The gap between its inner wall and the outer surface of the steel pile 10 forms the lubricating slurry channel 61, the detailed structure of which is described later. In this embodiment, the drainage pipe 42 is a closed pipe, and the slurry flows in its inner cavity without entering the space outside the pipe. The inner wall of the friction-reducing isolation sleeve 60 is provided with a clearance groove 63 at a position corresponding to the drainage pipe 42. The lubricating slurry channel 61 passes around the outside of the drainage pipe 42, and the two are not connected. The clearance groove 63 is used to accommodate the drainage pipe 42. When using the sleeve retention and steel pile extraction recovery method, the clearance range of the sleeve should also be adapted to the range of the drainage pipe 42 moving upward with the pile to avoid forming a limiting part that obstructs the extraction. Figure 4 This shows the cross-sectional fit relationship of the corresponding pipeline locations.

[0057] The drainage pipe 42 can also be replaced by other closed grout guiding structures. For example, a groove extending laterally can be formed on the surface of the first flange 12 facing the second flange 13, and the groove opening can be welded closed by a cover plate to form a closed channel to replace the closed steel pipe. Another feasible approach is to replace the drainage hole 41 with a cross-connector welded to the root of the web 11 and spanning the web 11. Both ends of the cross-connector are still connected to the second grouting cavities 32 at both ends of the first flange 12 via a drainage pipe 42. Alternatively, the drainage hole 41 can be omitted from the web 11, and a grout guiding pipe extending from one end to the other can be laid on the surface of the first flange 12 away from the web 11. This grout guiding pipe crosses the web 11 and directly connects to the second grouting cavities 32 at both ends of the first flange 12. In this case, the grout guiding pipe constitutes a transverse drainage channel 40, which is also separated from the lubricating grout channel 61 in the same way as described above.

[0058] Regarding the cavity connected by the transverse guide channel 40, in this embodiment, the two drainage pipes 42 connect the second grouting cavity 32 between the outer locking buckle 22 and the second fastening part 16. There are two reasons for selecting the second grouting cavity 32: firstly, the second grouting cavity 32 is located on the side close to the web plate 11, resulting in the shortest laying path for the drainage pipes 42; secondly, the wall surface of the second grouting cavity 32 on the side of the steel pile 10 is the second fastening part 16, which is directly connected to the top of the locking member 14. The grout guide hole from the top of the locking member 14 through the second fastening part 16 into the second grouting cavity 32 is short and straight. The first grouting cavity 31 is grouted separately from its own grouting interface 34 at its top. This is because the first grouting cavity 31 is located on one side of the steel pile 10, where the wall is only the first fastening part 15 extending into the inner layer of the locking buckle 21. If the drainage pipe 42 is to be inserted into the first grouting cavity 31 at a deeper level, it is necessary to prefabricate the inclined grouting channel through the first fastening part 15 in the body of the locking member 14 and avoid the fastening gap between the inner layer of the locking buckle 21 and the first fastening part 15, which is a relatively complex structure. The first grouting cavity 31 runs through the pile length and its top is open at the top of the pile, so it can be filled to the full depth by grouting directly from the top, without the need to be connected through the transverse guide channel 40.

[0059] Under the above connection method, the first grouting cavity 31 and the second grouting cavity 32 in the same interlocking pair are never connected to each other, and each is closed in the circumferential direction and bears pressure on its own.

[0060] After the transverse flow channel 40 is set up, the grout injected from the top of the second grouting cavity 32 at one end of the first flange 12 can cross the steel pile 10 and flow to the second grouting cavity 32 at the other end of the first flange 12, so that the lock joints on both sides of a steel pile can be continuously filled in one grouting operation, and the return grout at the top of the cavity at the other end can be used as a direct criterion for filling in place.

[0061] Considering the need to prevent the locking mechanism from disengaging during support and to release the biting force during recovery, the biting point can also be implemented in the following ways.

[0062] See Figure 5 The inner locking buckle 21 and the first engaging part 15 are provided with elastic clamping members 50 at intervals along the pile length direction. The elastic clamping members 50 are clamped between the first engaging part 15 and the inner locking buckle 21 to restrict the relative movement of the sheet pile 20 and the steel pile 10 in the lateral direction. The spacing of the elastic clamping members 50 along the pile length direction is, for example, 1.0m to 3.0m, or for example, 1.5m to 2.0m.

[0063] The elastic clamping element 50 is, for example, a spring steel sheet. One end is fixed to the hook end of the first fastening part 15, for example, by spot welding or riveting. The other end is a free end, which slopes downward and extends towards the hook root wall of the inner locking buckle 21. Here, "extending" means that its arc-shaped surface faces the hook root wall of the inner locking buckle 21, so that it can provide abutment without hindering the upward extraction of the steel pile 10 later. The gap where the elastic clamping element 50 is located is the fastening gap between the hook end of the first fastening part 15 and the hook root of the inner locking buckle 21. This fastening gap is a corner of the cross-section of the first grouting cavity 31 and is connected to the rest of the cross-section of the first grouting cavity 31. During the insertion of the sheet pile 20 from top to bottom along its length, the hook root wall of the inner locking buckle 21 sweeps over the elastic clamping member 50 from top to bottom. The free end of the elastic clamping member 50 is pressed against the first fastening part 15 due to its downward inclination, without obstructing the insertion. After the sheet pile 20 is pressed into the design elevation, the elastic clamping member 50 continues to press against the hook root wall of the inner locking buckle 21 with its own elasticity, eliminating the lateral movement within the fastening gap. Although the fastening between the inner locking buckle 21 and the first fastening part 15 itself restricts their complete disengagement, a small relative movement can still occur within the fastening gap. After the elastic clamping member 50 is tightened, this small relative movement is also restricted, thereby reducing the risk of misalignment and disengagement of the locking joints during the pile driving and soil squeezing process of adjacent components.

[0064] The elastic clamping member 50 is a thin sheet-like component, arranged at intervals along the pile length, occupying only a local corner at its designated location. During grouting, the grout flows around it. The elastic clamping member 50 is located inside the first grouting cavity 31 without penetrating the cavity wall, thus not affecting the circumferentially closed and longitudinally continuous state of the first grouting cavity 31. After grouting is completed, the elastic clamping member 50 is encased by the grout within the first grouting cavity 31, and thereafter, the lateral constraint at the interlock is mainly borne by the hardened grout. During the component recovery stage, the elastic clamping member 50 does not need to be removed. When the sheet pile 20 is pulled out, the inner locking buckle 21 disengages from the elastic clamping member 50 along the pile length, and the elastic clamping member 50 remains on one side of the steel pile 10 along with the first fastening part 15.

[0065] The above-mentioned structures revolve around the interlocking grouting method for seepage prevention. Regarding the ability to recycle the entire component, the contact surface between the steel pile 10 and the surrounding cement-soil can be designed as follows: The friction-reducing isolation structure is used to improve the contact state between the steel pile 10 and the surrounding cement-soil. When combined with the aforementioned interlocking grouting structure, the grout channels of the two are isolated from each other, and they respectively meet the coordination requirements during installation and recycling.

[0066] See Figure 6A split-type friction-reducing isolation sleeve 60 is fitted around the outer periphery of the steel pile 10. A lubricating slurry channel 61 that runs along the length of the pile is formed between the friction-reducing isolation sleeve 60 and the outer surface of the steel pile 10. A one-way grouting valve 62 is provided at the bottom end of the steel pile 10. The one-way grouting valve 62 is connected upward to the lubricating slurry channel 61.

[0067] The friction-reducing isolation sleeve 60 is, for example, composed of two pieces joined together, connected by snaps or clamps, so it can be installed on the ground before the steel pile 10 is lifted; alternatively, it can be made of three or more pieces joined together, or installed in sections along the pile length. The split type means the sleeve can be assembled in sections on the ground and does not require re-opening after being buried in the soil. Snaps or clamps are used to maintain the alignment of each section, preventing the inner wall of the sleeve from being pressed tightly against the steel pile 10, thus preserving the lubricating slurry channel 61. The friction-reducing isolation sleeve 60 covers all exposed surfaces of the steel pile 10 except for the locking element 14 and its engagement with the sheet pile 20, including the inner and outer surfaces of the first flange 12 and the second flange 13, as well as the surfaces on both sides of the web 11, separating the steel pile 10 from the cement-soil between the piles within the sleeve's coverage area; the friction-reducing isolation sleeve 60 leaves space at the locking element 14 to avoid obstructing the fastening and cavity formation. The locking element 14 and the interlocking part are not in the area directly isolated by the sleeve. Their contact, grouting, and recycling functions are as described in the aforementioned lock structure description. The material of the friction-reducing isolation sleeve 60 is, for example, ultra-high performance concrete, which has a thin wall thickness and high rigidity.

[0068] The lubricating slurry channel 61 is formed by the gap between the inner wall of the friction-reducing isolation sleeve 60 and the outer surface of the steel pile 10, and is arranged along the length of the steel pile 10. The isolation relationship between the clearance groove 63 on the inner wall of the friction-reducing isolation sleeve 60 and the drainage pipe 42 can be found in the previous description of the transverse guide channel 40, and will not be repeated here.

[0069] A one-way grouting valve 62 is located at the bottom end of the steel pile 10 and connects upwards to the lubricating grout channel 61. The steel pile 10 is also equipped with a vertical grouting guide pipe extending from the pile top to the one-way grouting valve 62. This vertical grouting guide pipe, for example, is laid along the web 11, with its upper end forming a grouting inlet at the pile top and its lower end connecting to the grout inlet side of the one-way grouting valve 62. The friction-reducing lubricating grout flows from the pile top down through the vertical grouting guide pipe to the one-way grouting valve 62, and then enters the lubricating grout channel 61 through the one-way grouting valve 62. The one-way grouting valve 62 can be, for example, a duckbill valve or a ball check valve; any valve that allows grout to flow unidirectionally from the vertical grouting guide pipe to the lubricating grout channel 61 is acceptable. In this way, the one-way grouting valve 62 reduces the risk of mud backflow from the pile bottom into the vertical grouting guide pipe by restricting reverse flow. The vertical grout guide pipe is responsible for delivering grout to the bottom of the pile, while the lubricating grout channel 61 is responsible for distributing grout from the bottom of the pile upwards. The flow directions of the two are downwards and upwards, respectively. The pipelines, valves, and their connections that are pulled out together with the steel pile 10 should be located within the allowable pulling range of the sleeve and should not obstruct the placement of the sleeve.

[0070] The above structure operates as follows in the recovery state: Before extraction, friction-reducing and lubricating grout is injected from the top of the pile through the vertical grouting pipe into the one-way grouting valve 62. The grout enters the lubricating grout channel 61 through the one-way grouting valve 62 and fills from bottom to top, forming a continuous lubricating isolation layer around the steel pile 10 until the top of the steel pile 10 returns grout, indicating that the filling is in place. Since the anti-friction isolation sleeve 60 isolates the steel pile 10 from direct contact with the cement-soil between the piles from the time of pile planting, the surface of the steel pile 10 covered by the sleeve is not directly bonded to the cement-soil between the piles. With the added effect of the lubrication isolation layer, when there is no structural limit between the steel pile 10 and its accompanying accessories and the sleeve to prevent extraction, the steel pile 10 can be pulled out from the anti-friction isolation sleeve 60. The anti-friction isolation sleeve 60 is not pulled out with the steel pile 10 but remains in the soil. The resistance to be overcome during extraction is significantly reduced compared to the case where the steel pile parent material is directly bonded to the cement-soil. The above isolation and lubrication help reduce the bonding and friction resistance during the extraction of the steel pile 10, providing conditions for the recycling and reuse of components. The actual extraction resistance is also affected by the grout bonding at the locking part, the contact at the pile bottom, and the soil constraint.

[0071] As another layer parallel to the aforementioned single-component structure, the overall arrangement along the outline of the foundation pit can also be arranged as follows.

[0072] See Figure 3 The steel piles 10 include long steel piles 70 and short steel piles 71. The long steel piles 70 and short steel piles 71 are arranged alternately along the outline of the foundation pit 100 and have the same top elevation. The bottom of the long steel piles 70 is lower than the bottom of the short steel piles 71. The sheet piles 20 use a uniform pile length. That is, along the outline of the foundation pit 100, the sequence is: long steel piles 70, sheet piles 20, short steel piles 71, sheet piles 20, long steel piles 70… It should be noted that the long steel pile 70 and the short steel pile 71 are variable-length forms of the same component: their locking fasteners 14 have the same structure, their fastening method is the same as that of the sheet pile 20, and their transverse guide channels 40 have the same configuration. In embodiments with the same cross-section, the only differences between the two are the pile length and the pile bottom elevation. Since their structures at the interlocking points are completely identical, their staggered arrangement does not change the structure of the interlocking pair.

[0073] The top elevations of the long steel pile 70 and the short steel pile 71 are the same, so they can share the same precast top beam 90 without the need for separate connection structures for components of different pile lengths. For example, the bottom of the long steel pile 70 penetrates the confined aquifer and enters a relatively impermeable layer, while the bottom of the short steel pile 71 extends, for example, to the vicinity of the inflection point of the soil pressure moment in the foundation pit. A jet grouting expansion section 72 can also be formed around the bottom of the long steel pile 70 using high-pressure jet grouting. The bottom end of the long steel pile 70 is embedded in the jet grouting expansion section 72, which has a diameter of, for example, 1200 mm and is embedded in a relatively impermeable layer. The jet grouting expansion section 72 expands the cement-soil mass around the pile bottom, not the cross-section of the long steel pile 70 itself. Furthermore, the anti-friction isolation sleeve 60 has isolated the parent material of the long steel pile 70 from the cement-soil mass; therefore, the jet grouting expansion section 72 is not an enlarged pile head that is pulled out along with the long steel pile 70.

[0074] The sheet piles 20 adopt a uniform pile length, meaning all sheet piles 20 have the same length and bottom elevation. Thus, within the depth range where the steel piles 10 are installed, the connection between the sheet piles 20 and the steel piles 10 is continuous and uninterrupted from the top of the pit to that depth. The first grouting cavity 31 and the second grouting cavity 32 are also continuously connected within this depth range, forming an uninterrupted seepage-proof interface after grouting. Below the bottom of the short steel piles 71, the seepage-proof interface is continuously maintained by the pile body of the sheet piles 20 and the cement-soil water-stop curtain between the piles. If the sheet piles 20 also vary in length with the steel piles 10, then the pile body of the sheet piles below the short pile section will no longer be continuous, and a gap will appear in the seepage-proof interface at that depth.

[0075] From the above arrangement, it can be deduced that: the long steel piles 70 bear the anti-slip and anti-overturning capacity required for the lower embedment, and the short steel piles 71 bear the bending stiffness required for the middle and upper parts. The staggered arrangement of the two makes the bending stiffness of the wall distributed in a stepped manner along the depth, which is compatible with the distribution of the soil pressure of the foundation pit along the depth and avoids the stiffness redundancy caused by the uniform use of long piles in the lower part; at the same time, the steel sheet piles 20 maintain a uniform pile length, and together with the cement-soil water-stop curtain below the pile bottom of the short steel piles 71, they maintain the continuity of the water-stopping interface; this continuity does not mean that there is still an interlocking engagement between the steel sheet piles 20 and the short steel piles 71 below the pile bottom of the short steel piles 71.

[0076] Corresponding to the aforementioned combined pile support system with built-in grouting for seepage prevention, this embodiment of the invention also provides a construction method for such a system. This method is implemented on-site by the construction party of the foundation pit support project to construct the aforementioned support system and complete the grouting filling of the interlocking joints. The structure of each component involved in the method can be found in the preceding description. Figures 1 to 6 The explanation provided.

[0077] See Figure 7 The construction method includes: Step S1: Drive the steel piles into the design elevation.

[0078] The steel pile 10 is manufactured in the factory before it enters the site. The steel pile has a web and a first flange and a second flange connected to both sides of the web. Each end of the first flange is fixed with a locking member. The locking member has a first fastening part and a second fastening part. The steel pile is provided with a transverse guide channel that spans the web.

[0079] After the construction team positions each steel pile 10 along the design axis of the foundation pit 100, they use a pile-planting device to apply pressure from the top of the pile to press it into the soil until the top of the pile reaches the design elevation. The pile-planting device can be, for example, a static pressure pile-planting machine, or a vibratory hammer; when using a static pressure pile-planting machine, a gantry guide frame can be used to control the verticality of the pile. At this point, the steel pile 10 is in place, and the locking members 14 at both ends of its first flange 12 form two vertical insertion guide grooves along the pile length, for the subsequent insertion of the sheet pile 20 along its lower edge in step S2.

[0080] Step S2: Drive the sheet piles into the design elevation.

[0081] The sheet pile 20 is also a pre-formed component, meaning that each side of the sheet pile has an inner locking ring and an outer locking ring that are fixed to each other. The construction team hoists the sheet pile 20 to one side of the pre-positioned steel pile 10, aligns the inner locking ring 21 and the outer locking ring 22 with the first engaging part 15 and the second engaging part 16, respectively, and then applies pressure from the top of the pile to insert the sheet pile 20 downward along the pile length and press it to the design elevation, thereby engaging the inner locking ring with the first engaging part and the outer locking ring with the second engaging part, forming a grouting cavity between the inner locking ring and the first engaging part, and forming another grouting cavity between the outer locking ring and the second engaging part. Both grouting cavities are circumferentially closed and extend along the pile length. The two ends of the transverse guide channel are respectively connected to the grouting cavities at both ends of the first flange.

[0082] Since the first locking part 15 and the second locking part 16 are formed on the same locking member 14, and the locking openings of the inner locking 21 and the outer locking 22 face the same direction, the sheet pile 20 can complete the two locking points simultaneously with one insertion, without the need for separate alignment of the two locking points. After the sheet pile 20 is pressed to the design elevation, the first grouting cavity 31 and the second grouting cavity 32 are formed on-site at the locking joint, with their tops protruding above the ground, and the grouting operation can then be carried out on the top of the pile.

[0083] By alternately driving steel piles 10 and sheet piles 20 along the outline of the foundation pit 100 in the manner described above, a continuous wall extending along the outline is formed. The driving order of the steel piles 10 and the driving order of the sheet piles 20 on both sides of the same steel pile 10 are not limited in this embodiment of the invention.

[0084] Step S3: Grout is injected into one of the grouting cavities connected by the transverse guide channel from the top of the grouting cavity, so that the grout flows through the transverse guide channel into the other grouting cavity connected by the transverse guide channel.

[0085] This step is performed after the sheet piles 20 on both sides of the same steel pile 10 have been driven into place. The construction party connects the grouting pipe to the top of the grouting cavity at one end of the first flange 12 and pumps grout into the cavity. The grout is a cement-based grout without coarse aggregate, such as cement grout, or a two-component grout made of cement and water glass, or ultrafine cement grout; because the grout does not contain coarse aggregate, it can pass smoothly through the flow section of the drainage pipe 42 and the guide hole 41. After being injected from the top, the grout fills downward along the cavity. When it fills to the height where the transverse guide channel 40 is provided, it enters the guide hole 41 through the drainage pipe 42, crosses the web 11, and then enters the grouting cavity at the other end of the first flange 12 through another drainage pipe 42, and then rises upward from the cavity. When multiple guide holes 41 are provided along the length of the pile, the grout flows through the web 11 from the highest point that has been filled with grout, and the remaining guide holes 41 flow down with the filling surface to participate in the grout transfer in sequence.

[0086] The grout crosses the web 11 and rises upwards within the cavity at the other end, driven by the grouting pump rather than the grout's own weight. Both grouting cavities are circumferentially closed, and the drainage pipe 42 and guide hole 41 are also closed flow sections. When connected, they form a communicating vessel: the grouting pump establishes a pressure difference to drive the grout flow; after overcoming the flow resistance of the cavity, drainage pipe 42, and guide hole 41, the grout flows to the other end. The specific pressure difference is also affected by the liquid levels on both sides, the grout properties, and friction and local resistance. Therefore, the horizontally extending section in the transverse guide channel 40 does not obstruct flow due to the lack of elevation difference, nor does it require additional transport power.

[0087] Therefore, it can be seen that the grouting cavities at both ends of the steel pile 10 can be filled by injection from one point, provided that the grouting cavities at both ends are closed circumferentially and can establish and maintain grouting pressure. The transverse guide channel 40 connects the two into a continuous path. If the lock is still an open gap, the grout will leak from both sides of the gap and pressure cannot be established. The connecting device cannot be established, and even if the pipe is laid down one gap at a time, it will be difficult to fill the lock tightly.

[0088] It should be noted that both ends of the first flange 12 can be used as injection ends, and the injection from which end is used does not affect the implementation of the embodiment of the present invention.

[0089] Step S4: Use the return grout from the top of the other grouting cavity as the criterion for determining whether the grouting is in place, and stop grouting.

[0090] During the grouting process, the construction team continuously observed the top of another grouting cavity. Once grout returned from the top of this cavity, it indicated that the grout had filled the injection end cavity, the transverse guide channel 40, and the entire space of the cavity, and the joint filling was in place. The construction team then shut down the grouting pump and sealed the injection end. The reason why grout return at this point can be used as a criterion is that the top of the grouting cavity is located at the top of the pile on the ground, and whether or not grout has returned can be directly confirmed visually; on the other hand, the grout discharge status of the guide hole 41, which is buried below the ground, cannot be observed from the ground.

[0091] Compared to existing technologies where the interlocking joints only create open gaps, the sealing medium cannot be retained, and grouting cannot build up pressure, often necessitating high-pressure grouting outside the foundation pit to plug leaks after they occur, the above construction method creates two pressurized closed cavities at the interlocking joints simultaneously with pile driving. This allows for on-site seepage prevention and reinforcement at the interlocking joints, eliminating secondary disturbance to the surrounding soil caused by external plugging. Furthermore, the cavities at both ends of the same steel pile are interconnected via transverse diversion channels, allowing for filling of both interlocking joints with a single injection, reducing the number of steps compared to grouting each joint separately. Additionally, the grout return criterion is based on the pile top at ground level, and the filling status can be directly visually confirmed without relying on underground locations for judgment.

[0092] In step S3 above, when grouting into the grouting cavity, the pressure can be given all at once or increased in stages. When increasing in stages, step S3 can specifically include steps S31 to S33.

[0093] Step S31: Inject grout into the grouting cavity at a first pressure.

[0094] The first pressure is the lowest of the three pressures, for example, 0.3 MPa to 0.5 MPa. At this pressure, the grout flow rate is relatively slow, allowing the grout to fill the gaps inside the joint section by section from top to bottom along the cavity, which helps to reduce uneven local filling caused by rapid grouting.

[0095] Step S32: After grouting is completed at the first pressure, grout is injected into the grouting cavity at a second pressure greater than the first pressure.

[0096] The second pressure is, for example, 0.5 MPa to 0.8 MPa. After the pressure is increased, the grout that has been filled in the cavity is squeezed and fills the residual voids in the cavity. The water-swellable sealing strip 33 that is pre-installed throughout the cavity is also pressed by the grout towards the interlocking surface and adheres to it.

[0097] Step S33: After grouting is completed at the second pressure, grout is injected into the grouting cavity at a third pressure greater than the second pressure.

[0098] The third pressure is, for example, 0.8 MPa to 1.2 MPa. The third stage further increases the pressure based on the filling in the first two stages to promote the grout's entry into unfilled local voids. The grouting pressure is limited to maintaining the stability of the interlock structure and surrounding soil; the grout's seepage into the surrounding soil or the formation of a ring-shaped compaction zone is not considered a necessary outcome for this stage. The pressure values ​​mentioned above are examples and can be adjusted according to geological conditions and grout mix ratios.

[0099] The segmented, incremental grouting method is used to first fill the gaps in the interlocking joints, and then increase the pressure to promote the filling of local voids. If a high pressure is applied from the beginning, the grout will preferentially precipitate out from the path of least resistance, leaving unfilled voids in the cavity; if the pressure is too low, it may not be enough to overcome the flow resistance and complete the intended filling. Therefore, the pressure at each stage should be selected according to the actual grouting conditions.

[0100] Steps S1 to S4 constitute the construction and grouting process of the combined pile support system. To form a cement-soil water-stop curtain between the steel piles 10 and the sheet piles 20, a preparatory step can be added before step S1. This preparatory step is not related to... Figure 7 The grouting process shown is incorporated into the same sequence, which is denoted as step S0 here.

[0101] Step S0: Construct a cement-soil waterstop curtain along the outline of the foundation pit.

[0102] After the construction team lays out and positions the foundation pit along its 100mm outline, they use a mixing pile machine, such as a three-axis mixing pile machine, to mix and form piles in situ, creating a continuous cement-soil water-stop curtain 80 along the foundation pit's outline. The cement content can be configured in layers along depth: the shallow layer with a high content 81, for example, uses 18% to 20% by mass, forming a high-strength, low-permeability seepage-proof core; the deeper layer with a low content 82, for example, uses 12% to 14% by mass, meeting the water-stopping requirements while reducing the resistance that the steel piles must overcome when pulled out 10 days later. When a jet grouting expansion section 72 is provided, the jet grouting expansion section 72 can be constructed in situ using high-pressure jet grouting after the curtain piles are formed and before pile driving.

[0103] Both steps S1 and S2 must be performed before the initial setting of the cement-soil waterstop curtain 80. When the cement-soil has not yet set, it is in a plastic state, allowing the steel piles 10 and sheet piles 20 to be directly driven into it, and then encased by the cement-soil as it sets. If the piles are driven after the cement-soil has set and hardened, the soil squeezing action of the piles will cause the already formed cement-soil body to crack, thereby compromising the continuity of the waterstop curtain.

[0104] Because the pile driving is completed before the initial setting of the cement soil, the two processes of curtain forming and pile planting can be continuously overlapped; and because the cement soil only sets after the pile driving, it can fit and wrap with the friction-reducing isolation sleeve 60 around the steel pile 10 and the pile body of the steel sheet pile 20, making the water-stopping interface between piles more continuous than the method of hardening first and then inserting the pile.

[0105] All of the above procedures occur during the construction and use of the support system. As another stage that connects to this stage, the steel piles 10 and sheet piles 20 can be pulled out and retrieved after the foundation pit is used. For this purpose, the following three procedures can be added after step S4, which are recorded as steps S5 to S7 according to the actual time sequence.

[0106] Step S5: Through the one-way grouting valve located at the bottom of the steel pile, anti-friction lubricating grout is injected into the lubricating grout channel between the steel pile and the anti-friction isolation sleeve sleeved around the outer periphery of the steel pile.

[0107] After the foundation pit is completed, the construction team first removes the connecting bolts between the precast capping beam 90 and the top of each vertical component, and then lifts the precast capping beam 90 away. Next, the grouting pipe is connected to the vertical guide grouting pipe at the top of the steel pile 10. Anti-friction lubricating grout is then injected into the lubricating grout channel 61 through the vertical guide grouting pipe and the one-way grouting valve 62 at the bottom of the steel pile 10. The injection pressure is, for example, 0.5 MPa to 1.0 MPa, and the grout is, for example, a composite grout prepared from bentonite and polymer materials. The grout fills the lubricating grout channel 61 from bottom to top until grout returns to the top of the steel pile 10, at which point the injection is stopped. The pile is then left to stand for, for example, 12 to 24 hours to allow the grout to fully impregnate the surface.

[0108] In this embodiment, lubrication grouting is completed before the sheet pile 20 is extracted, followed by the sequential extraction of the sheet pile 20 and the steel pile 10. Backfilling after the sheet pile 20 is extracted should be coordinated with the recovery of the steel pile 10 to prevent backfill material from entering the lubricating grout channel 61 through the locking clearance area or sleeve joint, thus increasing subsequent extraction resistance. Pre-lubrication does not replace protection of the aforementioned areas and the backfilling process.

[0109] Step S6: Pull out the sheet pile and backfill the formed pile hole with solidified soil.

[0110] The construction team used pile extraction equipment, such as a static pressure pile extractor, to vertically extract each of the 20 sheet piles one by one. Each sheet pile 20 was extracted independently, without the need for coordinated extraction across the entire span. After the sheet pile 20 was extracted, it was immediately backfilled with solidified soil. The solidified soil was prepared, for example, by mixing cement, fly ash, and undisturbed soil in a mass ratio of 1:2:7.

[0111] Step S7: After the sheet pile is pulled out, the steel pile is pulled out and the solidified soil is backfilled into the pile hole formed after the steel pile is pulled out.

[0112] After all the sheet piles 20 have been extracted, the construction team extracts the steel piles 10 one by one in the same manner. At this time, the steel piles 10 are pulled out from the friction-reducing isolation sleeves 60, which remain in the soil and are filled and wrapped by the solidified soil that is backfilled as the piles are extracted. Because the friction-reducing isolation sleeves 60 are not extracted with the piles, the extraction resistance of the sleeve-covered parts mainly comes from the contact friction after lubrication, and does not directly bear the bonding effect between the outer surface of the sleeve and the cement soil between the piles. The resistance of the not completely isolated parts such as the locking and the bottom of the pile still needs to be considered during the extraction process.

[0113] The sequence of the above three processes enables the friction reduction measures to take effect: the lubricating slurry is filled into the steel pile before the steel sheet pile is pulled out and the pile hole is backfilled, thus reducing the frictional resistance that the steel pile must overcome when it is pulled out, and the steel pile is less likely to be twisted and deformed due to excessive pulling resistance.

[0114] The above construction method will be further explained below using a deep foundation pit project in a confined water-sand layer as an example.

[0115] In this scenario, the excavation depth of the foundation pit 100 is approximately 8m. From top to bottom, the site consists of fill, silty clay, and a confined water-bearing sand layer, with a relatively impermeable layer below the sand layer.

[0116] See Figure 1 and Figure 3 The values ​​for each item in this scenario are as follows: Steel pile 10 uses H-beams, and sheet pile 20 uses U-shaped sheet piles. The center-to-center distance between adjacent steel piles 10 is 1060mm. Sheet piles 20 use a uniform pile length of 18m, with their bottoms penetrating the confined sand layer and extending at least 2m into the relatively impermeable layer. Steel piles 10 are arranged in a staggered pattern of long and short piles: the bottom of the long steel pile 70 has a 1200mm diameter jet grouting expansion section 72 embedded at least 1m into the relatively impermeable layer; the bottom of the short steel pile 71 extends to near the inflection point of the soil pressure moment in the foundation pit. Both have the same top elevation and share a precast pressure top beam 90. Both the locking fastener 14 and the outer locking fastener 22 are welded together with a continuous fillet weld along the entire length of the pile. The cross-sections of both the inner locking fastener 21 and the outer locking fastener 22 are C-shaped. Both grouting cavities are pre-installed with water-swellable sealing strips 33 with a cross-section of 18mm × 20mm. The grouting interface 34 is a short pipe joint welded to the top of the pile. The friction-reducing isolation sleeve 60 is made of ultra-high performance concrete and is in a two-piece mating form. The thickness of the lubricating slurry channel 61 between it and the steel pile 10 is 3mm. The one-way grouting valve 62 is a ball check valve. The transverse guide channel 40 is the second grouting cavity 32 connecting both ends. A guide hole 41 with a diameter of 20mm is provided on the web plate 11 every 2.0m along the pile length. The drainage pipe 42 is a closed steel pipe laid along the inner side of the first flange 12. The first grouting cavity 31 is grouted separately from the grouting interface 34 at its top. The elastic clamping element 50 uses spring steel sheets, and one is installed every 2.0m along the length of the pile.

[0117] The construction team will proceed according to the following sequence: First, execute step S0, using a three-axis mixing pile machine to construct an 80mm cement-soil water-stop curtain along the outline of the foundation pit. The cement content will be 18% for the 0-8m depth section and 12% for the 8m depth to the pile bottom section. Before the curtain initially sets, proceed with steps S1 and S2, using a static pressure pile driver equipped with a gantry guide frame to sequentially drive in steel piles 10 and sheet piles 20. After pile driving is completed, proceed with steps S31 to S33, using cement grout. The first pressure will be 0.4MPa, the second pressure 0.6MPa, and the third pressure 1.0MPa. After the top of the other grouting cavity returns grout, proceed with step S4 to stop grouting. The foundation pit will be excavated in layers, and steel walers and steel supports will be erected as the excavation progresses until the main structure is completed. After the foundation pit is used, step S5 is executed. From the top of the pile, through the vertical grouting pipe, a one-way grouting valve 62 is injected with a friction-reducing and lubricating grout made of bentonite and polymer material at a pressure of 0.8 MPa. The mixture is then left to stand for 18 hours. Then, steps S6 and S7 are executed to pull out the sheet piles 20 and steel piles 10 one by one and backfill with solidified soil prepared in a ratio of 1:2:7.

[0118] In this scenario, the entity implementing the above construction method is the construction party undertaking the foundation pit support project, and what it performs are steps S0 to S7. The implementation of steps S3 and S4 can be directly observed on the ground: the grouting pipe is connected to the top of one grouting cavity, and grouting stops after grout returns to the top of another grouting cavity. This is the identifiable form of this method on the construction site.

[0119] In this scenario, four grouting cavities are formed at both ends of the first flange of a steel pile. The second grouting cavities 32 at both ends are interconnected via the transverse guide channel 40. Both cavities can be filled together by grouting from one end. The first grouting cavities 31 at both ends are grouted from the grouting interface 34 at the top of the pile. The on-site pipe laying and connection process is reduced compared to grouting each of the four cavities one by one.

[0120] The values ​​in the above scenarios are all example values ​​for this project, and can be selected separately according to the geological conditions, foundation pit depth and surrounding environmental protection requirements, and do not constitute a limitation of the present invention.

[0121] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A combined pile support system with built-in grouting for seepage prevention, comprising steel piles and sheet piles arranged alternately along the contour of a foundation pit, wherein the steel piles have a web and a first flange and a second flange respectively connected to both sides of the web, characterized in that, The sheet pile has an inner locking ring and an outer locking ring fixedly connected to each other on both sides; a locking member is fixedly connected to each end of the first flange, the locking member having a first engaging part and a second engaging part, the inner locking ring engaging with the first engaging part, the outer locking ring engaging with the second engaging part, the inner locking ring and the first engaging part forming a grouting cavity, the outer locking ring and the second engaging part forming another grouting cavity, both grouting cavities being circumferentially closed and extending along the length of the pile; the steel pile has a transverse guide channel spanning the web, the two ends of the transverse guide channel being respectively connected to the grouting cavities at both ends of the first flange.

2. The combined pile support system with built-in grouting and seepage prevention according to claim 1, characterized in that, The inner locking opening faces the same direction as the outer locking opening, and the two grouting cavities are located on both sides of the fixed connection between the inner and outer locking parts.

3. The combined pile support system with built-in grouting and seepage prevention according to claim 1, characterized in that, Both of the aforementioned grouting cavities are equipped with water-swellable sealing strips that run along the length of the pile.

4. The combined pile support system with built-in grouting seepage prevention according to claim 1, characterized in that, Each of the two grouting cavities has a grouting interface at its top that communicates with its interior.

5. The combined pile support system with built-in grouting seepage prevention according to claim 1, characterized in that, The transverse flow channel includes a flow hole penetrating the web along the thickness direction and two drainage pipes, the two drainage pipes respectively connecting the two ends of the flow hole to the grouting cavities at both ends of the first flange.

6. The combined pile support system with built-in grouting seepage prevention according to claim 1, characterized in that, The inner locking part and the first fastening part are provided with elastic tightening members at intervals along the length of the pile. The elastic tightening members are tightened between the first fastening part and the inner locking part to restrict the relative movement of the sheet pile and the steel pile in the lateral direction.

7. The combined pile support system with built-in grouting seepage prevention according to claim 1, characterized in that, The outer periphery of the steel pile is fitted with a split friction-reducing isolation sleeve, and a lubricating grout channel running along the length of the pile is formed between the friction-reducing isolation sleeve and the outer surface of the steel pile. A one-way grouting valve is provided at the bottom end of the steel pile, and the one-way grouting valve is connected upward to the lubricating grout channel.

8. The combined pile support system with built-in grouting seepage prevention according to claim 1, characterized in that, The steel piles include long steel piles and short steel piles. The long steel piles and the short steel piles are arranged alternately along the outline of the foundation pit and have the same top elevation. The bottom of the long steel piles is lower than the bottom of the short steel piles. The steel sheet piles adopt a uniform pile length.

9. A construction method for a combined pile support system with built-in grouting anti-seepage, characterized in that, include: S1. Press the steel pile into the design elevation, wherein the steel pile has a web and a first flange and a second flange respectively connected to both sides of the web, and a locking member is fixed to each end of the first flange. The locking member has a first fastening part and a second fastening part. A transverse guide channel is provided on the steel pile across the web. S2. Press the sheet pile into the design elevation. Each side of the sheet pile is provided with an inner locking and an outer locking that are fixed to each other. The inner locking is engaged with the first locking part, and the outer locking is engaged with the second locking part. The inner locking and the first locking part form a grouting cavity, and the outer locking and the second locking part form another grouting cavity. Both grouting cavities are closed circumferentially and extend along the length of the pile. The two ends of the transverse guide channel are respectively connected to the grouting cavities at both ends of the first flange. S3. Grout is injected into one of the grouting cavities connected by the transverse guide channel from the top of the grouting cavity, so that the grout flows through the transverse guide channel into the other grouting cavity connected by the transverse guide channel; S4. Use the return grout from the top of the other grouting cavity as the criterion for determining whether the grouting is in place, and stop grouting.

10. The construction method of the combined pile support system with built-in grouting seepage prevention according to claim 9, characterized in that, The grouting from the top of one of the grouting cavities connected by the transverse guide channel into the grouting cavity includes: grouting into the grouting cavity at a first pressure; after grouting at the first pressure is completed, grouting into the grouting cavity at a second pressure greater than the first pressure; and after grouting at the second pressure is completed, grouting into the grouting cavity at a third pressure greater than the second pressure.

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