A construction method for a pipe sheet pile composite wharf suitable for foundation pit slope topography

Abstract

This invention belongs to the field of waterway engineering construction technology, specifically relating to a construction method for a pipe-sheet composite pile wharf suitable for foundation pit slope terrain. Based on the cofferdam foundation pit slope terrain, this invention employs an optimized construction process of "slope piling – layered backfilling – tensioning – full-area backfilling." Through the deep synergy between the pipe-sheet composite piles and the anchorage system, this invention cleverly adapts to the complex and varied terrain conditions of the foundation pit slope, significantly improving the stability of the wharf structure in complex environments, greatly optimizing the construction process, and increasing construction efficiency. It provides an innovative solution for wharf construction under foundation pit slope terrain, with broad application prospects and significant economic and social benefits.

Description

Technical Field

[0001] This invention belongs to the field of waterway engineering construction technology, specifically relating to a construction method for a pipe sheet composite pile wharf suitable for the topography of foundation pit slope. Background Technology

[0002] With the acceleration of global economic integration and the continuous growth of international trade, the demand for port construction, as a key hub connecting land and water transportation, is increasingly strong. Especially in inland river and lake areas, and estuaries affected by tides, to meet the berthing requirements of modern ships becoming larger and deeper, wharf construction often needs to extend into the water, inevitably encountering various complex geological and topographical conditions. Among these, pit-like slope topography is a common and extremely difficult construction condition. Its typical characteristic is that the original ground elevation of the proposed wharf area is lower than the design wharf surface elevation and water level, forming a "pit-like" landform adjacent to the water. Under such terrain, traditional high-pile beam-slab wharf or gravity wharf schemes face severe challenges: the former suffers from insufficient stability due to the excessive free length of the pile foundations and cannot effectively form a rear land area; the latter requires the construction of large cofferdams and deep underwater foundation construction, resulting in high project costs, long construction periods, and significant safety risks. Therefore, developing a wharf structure and supporting construction methods that can take into account structural safety, convenient construction, economic rationality, and are particularly suitable for the topography of foundation pit slopes has become an important issue that urgently needs to be addressed in the field of port engineering.

[0003] Sheet pile wharves, as a traditional wharf structure, are widely used due to their advantages such as lightweight structure, low material consumption, and strong adaptability to foundation deformation. However, conventional sheet pile wharf construction usually adopts the process of "building the wall first, then anchoring", that is, first constructing a continuous sheet pile wall on the water or land, then excavating behind the wall to build the anchoring structure (such as anchoring wall, anchoring sheet piles, etc.), and finally installing tie rods. This process reveals significant limitations in the topography of the foundation pit slope: First, the installation of sheet piles in the low-lying foundation pit restricts equipment placement and working space, resulting in low construction efficiency; second, large-scale excavation behind the already formed sheet pile wall to construct the anchorage structure not only involves a large amount of earthwork but also severely disturbs the initial stability of the installed sheet piles, making it highly susceptible to displacement, overturning, or even instability of the sheet pile wall due to the imbalance of soil pressure in front of and behind the wall, posing extremely high safety risks; third, the entire construction process is significantly affected by the water level, and improper drainage of the foundation pit will further exacerbate the construction difficulty and safety uncertainties.

[0004] Chinese invention patent CN 205530114 U discloses a tensioned steel pipe sheet pile wharf structure. While this structure boasts advantages such as simple structure, rapid construction, and low investment, and is suitable for the renovation or construction of large wharf projects under complex conditions, it exhibits significant shortcomings when dealing with the terrain conditions of foundation pit slopes. Foundation pit slopes possess unique geological and hydrological characteristics, such as large slope variations, uneven soil texture, and potential groundwater seepage. The tensioned steel pipe sheet pile wharf structure fails to effectively address the construction and structural stability challenges posed by these special terrain features, making it difficult to guarantee the long-term safe operation and normal functioning of the wharf under foundation pit slope conditions.

[0005] To overcome these challenges, the engineering community has explored various improvement solutions, such as using heavier and longer steel sheet piles or combining them with diaphragm walls. However, these solutions often come with a sharp increase in costs and fail to fundamentally optimize the construction process sequence, which is unfavorable to the foundation pit terrain. On the other hand, steel pipe piles, due to their high strength, good bending resistance, and fast construction speed, are widely used in high-pile wharves in wharf engineering. Combining steel pipe piles with sheet piles to form a pipe-sheet composite pile wall can theoretically fully leverage the respective advantages of steel pipe piles as strong "supports" and sheet piles as continuous "baffles," significantly enhancing the overall wall's rigidity and stability. However, the key to achieving a technological breakthrough lies in how to innovatively apply this composite structure to the special terrain of foundation pit slopes and design a construction process that perfectly fits it and can turn disadvantages into advantages. The core issue is how to re-plan the logical relationship between key processes such as piling, backfilling, and anchoring to avoid unfavorable working conditions and ensure structural stability and operational feasibility throughout the construction process. Summary of the Invention

[0006] To address the aforementioned issues, this invention discloses a construction method for a pipe-sheet composite pile wharf suitable for the topography of foundation pit slopes. Addressing the characteristics of significant slope gradients and poor soil stability in cofferdam foundation pits, this method optimizes the construction process and key technologies to achieve precise adaptation between the structure and the terrain, thereby improving construction quality and safety. The technical solution adopted by this invention to achieve the above objectives is: a construction method for a pipe-sheet composite pile wharf suitable for the topography of a foundation pit slope. The method is implemented based on the topography of the cofferdam foundation pit slope and adopts an optimized process of slope piling → layered backfilling → tensioning → full-area backfilling. Specifically, it includes the following steps: S1. Site preparation; S2. Steel pipe pile driving; S3. Sheet pile installation; S4. Pile core concrete construction; S5. Backfilling in layers at the rear; S6. Anchorage wall construction; S7. Tie rod installation; S8. Construction of the breast wall; S9. Construction of the remaining backfill and reverse filter layer; S10. Water injection into the foundation pit; S11. Construction of ancillary facilities and surface layer; S12. Dredging of the wharf front. Step S1 specifically includes: clearing, compacting, and adjusting the slope of the cofferdam foundation pit slope operation area to form an operation surface that meets the stability requirements of the piling equipment. Step S2 specifically includes: setting up a guide frame on the prepared slope operation surface to control the position and verticality of the pile axis; using a composite process of pre-sinking with a vibratory hammer and re-driving with an impact hammer to drive the steel pipe piles one by one to a predetermined depth; during the piling process, the guide frame corrects the plane distortion and verticality deviation of the pile in real time; the guide frame consists of a longitudinal main beam, a transverse connecting beam, and an adjustable guide clamp; the gap between the guide clamp and the side wall of the steel pipe pile is controlled at 20-30mm; during the piling process, the verticality of the pile is checked every 1-2m of driving, and the verticality deviation does not exceed 0.5%.

[0007] Step S3 specifically includes: using the already driven steel pipe piles as a reference, using a vibratory hammer to drive sheet piles into the soil along the interlocking structure on the side of the steel pipe piles, ensuring that the interlocking connection between the sheet piles and the steel pipe piles is tight, forming a continuous pipe-sheet composite pile wall.

[0008] Step S4 specifically includes: sequentially completing the cleaning of debris inside the steel pipe pile core, hoisting and positioning the reinforcing cage, fixing the tie rod end assembly at the preset position of the reinforcing cage, and then pouring the pile core concrete using the tremie method to ensure the compactness of the concrete pouring; the pile core is cleaned manually by setting up a temporary operating platform inside the pile core and using tools such as shovels and steel bars to clean the debris and loose soil inside the pile core; after cleaning, the inner wall of the pile core is cleaned with a brush, and the thickness of the sediment at the bottom of the pile core does not exceed 50mm; when the reinforcing cage is placed, a protective layer distance of 50-100mm is maintained between it and the pile core wall; the tie rod end assembly is fixed to the reinforcing cage by welding, and the welding length is not less than 10 times the diameter of the tie rod.

[0009] Step S5 specifically includes: performing layered backfilling behind the sheet pile composite wall, with each layer of backfill thickness controlled at 0.3-0.5m, and compacting each layer using a small tamping machine. During the backfilling process, the height difference between the inner and outer sides of the composite pile wall is strictly controlled to not exceed 3m, so that the inner side of the sheet pile has the conditions for anchor wall construction. The layered backfilling uses cohesive soil or sandy soil as filler, with the moisture content of the filler controlled within the range of optimum moisture content ±2%, and the compaction degree not less than 93%.

[0010] Step S6 specifically includes: after the backfill soil layer reaches the preset elevation of the anchor wall foundation, the anchor wall is constructed transversely along the bank slope. When the anchor wall is poured, tie rod holes corresponding to the tie rod ends are reserved, and the hole position deviation does not exceed ±50mm. Step S7 specifically includes: connecting one end of the tie rod to the pre-set tie rod end of the pile core, and passing the other end through the reserved hole in the anchor wall for graded tensioning construction, applying tension in stages to 100-200kN, and locking the tie rod end after tensioning is completed; the tie rod is tensioned in stages, in 3-4 stages, with the initial tensioning force being 30% of the design tension, and each subsequent stage increasing by 20%-30%, and resting for 10-15 minutes after each stage of tensioning before proceeding to the next stage of tensioning, and finally controlling the tension deviation within ±5kN. In step S8, the breast wall formwork erection is carried out using scaffolding or steel pipe pile welding bracket method. Reinforcing bars are tied at the top of the pipe-slab composite pile wall, formwork is erected, and breast wall concrete is poured to achieve an overall connection at the top of the composite pile wall. Before constructing the inverted filter layer in step S9, drainage holes with a diameter of 4cm are opened in the sheet piles, and the inner side is sealed and filtered with geotextile wrapped with graded crushed stone. After the breast wall concrete reaches the design strength, the backfilling work of the remaining area behind the anchor wall is completed, and the inverted filter layer is laid between the pipe-sheet composite pile wall and the backfill soil. The inverted filter layer adopts a geotextile + graded sand and gravel composite structure.

[0011] In step S10, water is slowly injected into the foundation pit through the pre-set water injection port of the cofferdam, with the injection rate controlled within 25m / d, until the water level reaches the design elevation; in step S11, after the breast wall reaches the design strength, the mooring bollards, fenders and other auxiliary facilities are installed, and then the top surface layer is constructed; in step S12, a dredger is used to dredge the waters in front of the wharf, dredging to the design bottom elevation of the harbor basin, thus completing the wharf construction.

[0012] A pipe-sheet pile composite wharf construction structure suitable for foundation pit slope terrain includes an anchor wall located in the first backfill area and pipe-sheet piles located in the site preparation area. The anchor wall is connected to the first backfill area via an anchor wall foundation, and the anchor wall and the pipe-sheet piles are connected by tie rods. The pipe-sheet piles include multiple steel pipe piles driven in the site preparation area and steel sheet piles located between adjacent steel pipe piles. The steel sheet piles have evenly spaced permeable holes to ensure communication between the water bodies inside and outside the wharf. A filter layer composed of graded sand and gravel is laid between the pipe-sheet piles and the backfill area behind them. The backfill material is tightly fitted to the tube sheet piles to prevent the loss of the backfill soil. The backfill material, following the tube sheet piles and inverted filter layer, is layered and compacted, and connected to the tube sheet piles via the inverted filter layer, providing rear support for the wharf. The breast wall, constructed of reinforced concrete, is located on top of the tube sheet piles and is fixed to the pile top with reinforcing bars or embedded parts to increase overall rigidity. Mooring bollards are installed on the breast wall, arranged according to the design scale, and firmly connected to the breast wall with embedded bolts, providing mooring points for ships. Fenders are installed on the outer edge of the breast wall to absorb impact energy from ships, forming a collision protection system with the breast wall. The tie rods include tie rod tensioners and tie rod connecting hinges, with the tensioners having both connecting and tensioning functions. The tie rod connecting hinges are used to connect the various tie rod sections.

[0013] The core innovation of this invention lies in completely overturning the traditional construction logic of sheet pile wharves, proposing an optimized process of "bank slope piling → layered backfilling → tensioning → full-area backfilling". This method first efficiently and accurately completes the construction of the sheet pile composite wall on the prepared bank slope, making full use of the existing foundation to provide initial support. Subsequently, innovatively, before installing the anchoring system, layered, symmetrical, and controllable backfilling is carried out behind the wall. This approach has multiple benefits: firstly, the backfill soil itself provides a certain degree of support to the sheet pile wall; secondly, it quickly creates a solid anchoring wall construction platform above the water surface, transforming complex underwater or muddy operations into simple onshore operations; and thirdly, by strictly controlling backfill parameters (such as layer thickness, compaction degree, and height difference between the inside and outside of the wall), it effectively manages changes in soil pressure during construction, ensuring that the deformation of the composite pile wall remains within a controllable range. After the anchorage wall is built and the tie rods are tensioned, the entire support system is formed. Then, the remaining backfilling and inverted filter layer construction continue. Finally, the design water depth is achieved through water injection into the foundation pit and dredging of the front edge. This method transforms the originally unfavorable "foundation pit" terrain into a controlled "dry construction" environment, realizing a fundamental shift from "passive response" to "active utilization" of the terrain.

[0014] In summary, the method described in this invention systematically solves several technical challenges in constructing wharves under the topography of foundation pit slopes through structural innovation and construction process reengineering. It has significant advantages such as high safety, short construction period, controllable cost, and strong adaptability, and is of great significance to promoting the advancement of port engineering construction technology. The beneficial effects of this invention are reflected in the following aspects: Slope-adaptive piling technology: Adjustable guide frame adapts to slope and pile diameter, composite piling process penetrates hard interlayer, verticality deviation ≤0.5%, accuracy improved by 40%. Refined construction of pile cores: manual cleaning is suitable for multiple pile diameters, and the ends of tie rods are welded and fixed, improving the stability of the support by 35%. Backfill support coordination technology: Clarify backfill parameters and graded tensioning process, and ensure that the lateral displacement of the composite pile wall is ≤15mm.

[0015] Optimized construction procedures: Eliminating the "construction platform backfilling" step: Traditional methods require large-scale backfilling and leveling of the entire work surface to form a temporary construction platform, typically accounting for 40%-60% of the total backfill volume, in order to meet the needs of the bank slope piling equipment. This invention, through "stepped site preparation + local reinforcement of the equipment parking area" technology, only requires laying steel plates or gravel cushions at the equipment parking points (reinforcement volume is only 1 / 10 of traditional platform backfilling), directly eliminating the need for large-scale platform backfilling and reducing foundation backfill volume by more than 50%. Attached Figure Description

[0016] Figure 1 This is a cross-sectional schematic diagram of the construction effect of the present invention.

[0017] Figure 2 This is a schematic diagram of the tube sheet composite pile connection of the present invention.

[0018] In the diagram: 1. Steel pipe pile, 2. Steel sheet pile, 3. Water-permeable hole, 4. Anchor wall, 401. Anchor wall foundation, 5. Tie rod, 501. Tie rod tensioner, 502. Tie rod connecting hinge, 6. First backfill area, 7. Site preparation area, 8. Filter layer, 9. Rear backfill area, 10. Breast wall, 11. Mooring bollard, 12. Fender, 13. Wharf surface layer, 14. Front edge of revetment, 15. Edge of cofferdam pit. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited to the specific embodiments.

[0020] Example 1

[0021] A pipe-sheet pile composite wharf construction structure suitable for foundation pit slope topography includes an anchor wall 4 located on the first backfill area 6 and pipe-sheet piles located on the site preparation area 7. The anchor wall 4 is connected to the first backfill area 6 via an anchor wall foundation 401. The anchor wall 4 and the pipe-sheet piles are connected by tie rods 5. The pipe-sheet piles include multiple steel pipe piles 1 driven in the site preparation area 7 and steel sheet piles 2 located between adjacent steel pipe piles 1. The steel sheet piles 2 have evenly spaced permeable holes 3 to ensure communication between the water bodies inside and outside the wharf. A filter layer 8, composed of graded sand and gravel, is laid between the pipe-sheet piles and the backfill area 9 behind them. The backfill area 9, located behind the tube sheet piles and the inverted filter layer 8, is where materials meeting the requirements are backfilled and compacted in layers. The inverted filter layer 8 connects to the tube sheet piles, providing rear support for the wharf. The breast wall 10, constructed of reinforced concrete and located at the top of the tube sheet piles, is fixed to the pile top with reinforcing bars or embedded parts to increase overall rigidity. Mooring bollards 11 are installed on the breast wall 10, arranged according to the design scale, and firmly connected to the breast wall with embedded bolts, providing mooring points for ships. Fenders 12 are installed on the outer edge of the breast wall 10 to absorb ship impact energy, forming a collision protection system with the breast wall 10. The tie rod 5 includes a tie rod tensioner 501 and a tie rod connecting hinge 502. The tie rod tensioner 501 has both connecting and tensioning functions. The tie rod connecting hinge 502 connects the various sections of the tie rod 5.

[0022] Example 2

[0023] like Figures 1-2 This invention presents a construction method for a pipe-sheet composite pile wharf suitable for foundation pit slope terrain, which has wide applications in the field of waterway engineering construction technology. The following are specific embodiments of the invention: S1. Site preparation The slope gradient of the bank is 1:1.5-1:3, the soil layer distribution, and the bearing capacity of the foundation are investigated to provide a basis for the remediation. Steep slopes are remediated using a stepped method, with each step ≤2m high and ≥4m wide, and the compaction degree of the working surface ≥90%. Areas with insufficient bearing capacity are replaced with a 0.5-1.0m layer of crushed stone. The equipment parking area is reinforced with 20mm steel plates or 500mm graded sand and gravel. S2. Steel pipe pile driving The guide frame consists of an I40 I-beam main beam, an I32 I-beam connecting beam, and adjustable clamping plates. A 20-30mm gap is left for pile diameters of 600-1200mm, and the angle is adjusted according to the slope. The bearing capacity is ≥500kN. Total station positioning is used, with a deviation of ±30mm. A 120t crane lifts the pile into the guide frame, with the pile top 0.5m above the top of the frame. A DZ120 vibratory hammer is used for pre-driving 5-8m at a frequency of 20-25Hz, followed by a YC25 impact hammer with an energy of 200-300kJ. Verticality is checked every 1-2m of driving, with a deviation ≤0.5%. The pile top elevation and penetration depth are controlled, with the last three passes ≤5cm / pass, employing a double depth control system. S3. Sheet pile driving Clean and oil the steel pipe pile interlocks, and repair any damaged interlocks. Lay out the lines using the steel pipe piles as a reference, with a deviation of ±20mm. Use a 50t crane to lift Larssen IV type sheet piles, align the interlocks, and drive them in using a DZ90 vibratory hammer at a frequency of 18-22Hz. Control the interlock gap to ≤5mm, and the flatness deviation of the combined pile wall to ±30mm. S4. Pile Core Concrete Construction The pile core is manually cleaned, with sediment ≤50mm. Then, the reinforcing cage is hoisted and lowered. A 20mm anchor plate is welded to the end of the tie rod on both sides of the cage, with a weld length ≥10 times the tie rod diameter and a height ≥8mm. C30 concrete is poured using the tremie pipe method, with a slump of 180-220mm and a tremie pipe embedment depth of 2-6m. S5. Backfilling in layers behind Select cohesive or sandy soil with a particle size ≤50mm and a mud content ≤15%, and control the moisture content within ±2% of the optimum value. Backfill in layers of 0.3-0.5m, compact 4 times with an HW60 compactor, control the height difference between the inside and outside of the pile wall to ≤3m, and achieve a compaction degree ≥93%. S6. Anchorage Wall Construction Excavate the foundation trench, 0.5m wider than the wall and 1.0-1.5m deeper, and pour a 100mm thick C15 foundation layer with a flatness of ±10mm. Then tie the reinforcing bars and erect the steel formwork. Reserve a φ150mm tie rod hole with a deviation of ±50mm, pour C30 concrete and vibrate it, and cure for ≥14 days until the strength reaches 80%. S7. Tie rod construction After processing and cleaning, the Φ98 special steel tie rod is connected to the pile core end at one end and passes through the pre-reserved hole in the anchor wall at the other end. YCW250 jacks are used for graded tensioning in 3-4 stages: 30%→60%→90%→100%, 100-200kN, with each stage held for 10-15 minutes, and an elongation deviation of ±6%.

[0024] S8. Construction of breast wall Clean the pile tops, tie the reinforcing bars, erect the formwork, and install the embedded parts. Pour C40 concrete in two layers and cure for ≥14 days. S9. Remaining backfill and reverse filter layer construction After the breast wall reaches its strength, backfill the remaining area, following the same standard as layered backfilling. Lay a geotextile with a strength of 300g / ㎡ or higher, with an overlap of ≥500mm, followed by a 300-500mm thick layer of 2-5mm graded sand and gravel. S10. Water injection into the foundation pit Inspect the cofferdam, then begin water injection. The injection rate is 2 m / d, and the slope displacement is monitored to be ≤5 mm / d and settlement to be ≤3 mm / d. The design water level will be maintained for 7 days.

[0025] S11. Construction of ancillary facilities and surface layer After the breast wall reaches the design strength, the mooring bollards, fenders and other auxiliary facilities are installed, and then the top surface layer is constructed.

[0026] S12. Dredging of the wharf front Echo sounders were used to measure depth and plan the dredging route. Grab bucket dredgers were used for segmented dredging, with depth measurements taken every 5 meters. The elevation deviation was controlled within ±200mm, and construction was completed upon successful acceptance.

[0027] Compared with traditional processes, the specific implementation values ​​of this invention are as follows: Table 1 Comparison of Backfill Volume and Cost

[0028] Although the above embodiments have described the concept and embodiments of the present invention in detail with reference to the accompanying drawings, those skilled in the art will recognize that various improvements and modifications can still be made to the present invention without departing from the scope of the claims, and therefore will not be elaborated here.

Claims

1. A construction method for a pipe-sheet composite pile wharf suitable for foundation pit slope terrain, characterized in that, The method is implemented based on the topography of the cofferdam foundation pit slope, and adopts an optimized process of slope piling → layered backfilling → tensioning → full-area backfilling, specifically including the following steps: S1. Site preparation; S2. Steel pipe pile driving; a guide frame is set up on the prepared bank slope working surface to control the axial position and verticality of the pile body. During the pile driving process, the guide frame is used to correct the plane twist and verticality deviation of the pile body in real time. S3. Sheet pile installation; S4. Pile core concrete construction; After fixing the tie rod end assembly at the preset position of the reinforcing cage, the pile core concrete is poured using the tremie method; S5. Layered backfilling: Layered backfilling is carried out behind the pipe-slab composite pile wall, controlling the thickness of each backfill layer and the height difference between the inner and outer sides of the composite pile wall; cohesive soil or sandy soil is used as fill material for layered backfilling. S6. Anchor wall construction: After the backfill soil layer reaches the preset elevation of the anchor wall foundation, the anchor wall is constructed transversely along the bank slope. When the anchor wall is poured, tie rod holes corresponding to the ends of the tie rods are reserved. S7. Tie rod construction: Connect one end of the tie rod to the pre-set tie rod end of the pile core, and pass the other end through the reserved hole of the anchor wall for staged tensioning. After tensioning is completed, lock the end of the tie rod. S8. Construction of the breast wall; S9. Remaining backfill and reverse filter layer construction: Before constructing the reverse filter layer, open drainage holes in the sheet piles. After the breast wall concrete reaches the design strength, complete the backfilling work in the remaining area behind the anchor wall. Simultaneously, lay the reverse filter layer between the pipe-sheet composite pile wall and the backfill soil. S10. Water injection into the foundation pit: Water is slowly injected into the foundation pit through the pre-set water injection port of the cofferdam until the water level reaches the design elevation; S11. Construction of ancillary facilities and surface layer; S12. Dredging of the wharf front.

2. The construction method for a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, Step S1 specifically includes: clearing, compacting, and adjusting the slope of the cofferdam foundation pit slope operation area to form an operation surface that meets the stability requirements of the pile driving equipment; Step S2 adopts a composite process of pre-sinking with a vibratory hammer and re-driving with an impact hammer to drive the steel pipe piles one by one into the predetermined depth. The guide frame consists of a longitudinal main beam, a transverse connecting beam, and an adjustable guide clamp. The gap between the guide clamp and the side wall of the steel pipe pile is controlled at 20-30mm. During the pile driving process, the verticality of the pile is checked every 1-2m of pile driving, and the verticality deviation does not exceed 0.5%.

3. The construction method for a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, Step S3 specifically includes: using the already driven steel pipe piles as a reference, using a vibratory hammer to drive sheet piles into the soil along the interlocking structure on the side of the steel pipe piles, ensuring that the interlocking connection between the sheet piles and the steel pipe piles is tight, forming a continuous pipe-sheet composite pile wall.

4. The construction method of a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, Step S4 specifically includes: sequentially completing the cleaning of debris inside the steel pipe pile core, hoisting and positioning the reinforcing cage, fixing the tie rod end assembly at the preset position of the reinforcing cage, and then pouring the pile core concrete using the tremie method to ensure the compactness of the concrete pouring; the pile core is cleaned manually by setting up a temporary operating platform inside the pile core and using tools such as shovels and steel bars to clean the debris and loose soil inside the pile core; after cleaning, the inner wall of the pile core is cleaned with a brush, and the thickness of the sediment at the bottom of the pile core does not exceed 50mm; when the reinforcing cage is placed, a protective layer distance of 50-100mm is maintained between it and the pile core wall; the tie rod end assembly is fixed to the reinforcing cage by welding, and the welding length is not less than 10 times the diameter of the tie rod.

5. The construction method for a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, Step S5 specifically includes: performing layered backfilling behind the sheet pile composite wall, with each layer of backfill thickness controlled at 0.3-0.5m, and compacting each layer using a small tamping machine. During the backfilling process, the height difference between the inner and outer sides of the composite pile wall is strictly controlled to not exceed 3m, so that the inner side of the sheet pile has the conditions for anchor wall construction. The layered backfilling uses cohesive soil or sandy soil as filler, with the moisture content of the filler controlled within the range of optimum moisture content ±2%, and the compaction degree not less than 93%.

6. The construction method of a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, The deviation of the tie rod hole position in step S6 shall not exceed ±50mm.

7. The construction method for a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, In step S7, the tension is applied in stages to 100-200kN. The tension rod is tensioned in stages, in 3-4 stages. The initial tension is 30% of the design tension, and each subsequent stage increases by 20%-30%. After each stage of tensioning, the rod is left to stand for 10-15 minutes before the next stage of tensioning is performed. The final tension deviation is controlled within ±5kN.

8. The construction method of a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, In step S8, the breast wall formwork erection is carried out using scaffolding or steel pipe pile welding bracket method. Reinforcing bars are tied at the top of the pipe-slab composite pile wall, formwork is erected, and breast wall concrete is poured to achieve an overall connection at the top of the composite pile wall.

9. A construction method for a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, In step S9, the diameter of the drainage hole is 4cm, and the inverted filter layer adopts a composite structure of geotextile + graded sand and gravel.

10. A construction method for a pipe sheet pile composite wharf suitable for foundation pit slope topography according to claim 1, characterized in that, In step S10, the water injection rate is controlled within 25m / d; in step S11, after the breast wall reaches the design strength, the mooring bollards, fenders and other auxiliary facilities are installed, and then the top surface layer is constructed; in step S12, a dredger is used to dredge the waters in front of the wharf to the design bottom elevation of the harbor basin, and the wharf construction is completed.

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