River network area spliced pile foundation and design method and construction method thereof

Abstract

The application discloses a spliced pile foundation in a river network area and a design method and a construction method thereof, and belongs to the technical field of pile foundation design. The design method comprises the following steps: determining the cohesion, internal friction angle, effective vertical stress, liquidity index and pore ratio of the soil body of the installation foundation pit of the spliced pile foundation, and calculating a comprehensive state index of the soil body; classifying the soil body according to the comprehensive state index of the soil body and evaluating the bearing capacity of the soil body; and according to the evaluation result of the bearing capacity of the soil body, adjusting the rotation angle, extension length and enlarged area of the pile bottom of the anchoring rod to change the total bearing capacity of the spliced pile foundation, so that the design requirement is met. The design method can classify the soil body and accurately quantify the bearing capacity of the soil body by introducing a comprehensive state index system of the soil body, so that the rotation angle, extension length and enlarged area of the pile bottom of the anchoring rod can be dynamically adjusted according to the bearing capacity, and the complex geological conditions in the soft soil area can be effectively adapted.

Description

Technical Field

[0001] This invention relates to the field of pile foundation technology, and in particular to a spliced ​​pile foundation for river network areas, its design method, and its construction method. Background Technology

[0002] Pile foundations are a type of foundation with high bearing capacity, wide applicability, and a long history. They transfer the load of a building to a deeper, more durable soil layer to meet the requirements of bearing capacity and settlement. For example, Chinese patent CN113684852A discloses a construction method and a composite pile foundation, which uses steel-concrete composite columns, bored piles, and steel-concrete inclined piles to form a composite pile foundation, thereby providing vertical bearing capacity, horizontal bearing capacity, and shear resistance.

[0003] However, in river network areas, the complex topography and hydrological conditions present the following challenges to the construction of traditional pile foundations:

[0004] Due to the diverse soil types in river network areas, mainly composed of river alluvium and lake silt, the soil is loose and mostly soft soil with low bearing capacity. This necessitates special consideration of foundation stability and pull-out resistance in pile foundation design, making the design quite challenging. Furthermore, the geographical division of rivers and the limitations imposed by bridges result in poor road conditions, making it difficult for large machinery to reach construction sites, and the construction cost of temporary roads is high. Suitable pile foundation types, such as cast-in-place piles and open-cut foundations, are difficult to implement effectively in areas with inconvenient transportation and harsh geological conditions, especially in areas with thick layers of silt and quicksand, where the risk of foundation pit collapse is high. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and problems of existing pile foundations, such as high design difficulty and inconvenient construction, and to provide a spliced ​​pile foundation for river network areas with lower design difficulty and convenient construction, as well as its design and construction methods.

[0006] To achieve the above objectives, the technical solution of the present invention is: a design method for spliced ​​pile foundations in river network areas, the design method comprising the following steps:

[0007] First, determine the cohesion, internal friction angle, effective vertical stress, fluidity index, and void ratio of the soil in the installation pit of the spliced ​​pile foundation. Then, calculate the comprehensive soil state index based on the cohesion, internal friction angle, effective vertical stress, fluidity index, and void ratio.

[0008] Soil is classified and its bearing capacity is evaluated based on the comprehensive soil state index.

[0009] Based on the soil bearing capacity evaluation results, the total bearing capacity of the spliced ​​pile foundation is changed by adjusting the rotation angle and extension length of the anchor rods and the enlarged area of ​​the pile bottom, so as to meet the design requirements.

[0010] The method of classifying soil and evaluating its bearing capacity based on the comprehensive soil state index is as follows:

[0011] If the soil comprehensive state index is less than 5, the soil is extremely soft and mobile soil with extremely low bearing capacity.

[0012] If the soil comprehensive state index is greater than or equal to 5 and less than 20, the soil is low-strength, high-compressibility soil with low bearing capacity.

[0013] If the soil comprehensive state index is greater than or equal to 20 and less than 50, the soil is medium-strength plastic soil with medium bearing capacity.

[0014] If the soil comprehensive state index is greater than or equal to 50, the soil is high-strength, low-compressibility soil with high bearing capacity.

[0015] The total bearing capacity of the spliced ​​pile foundation The calculation formula is:

[0016] ;

[0017] ;

[0018] ;

[0019] ;

[0020] ;

[0021] in, For the bearing capacity of the pile foundation itself, For the pile bottom resistance, For the side friction of the pile body, To add load-bearing capacity to the anchor rod, The ultimate end resistance of the soil at the pile tip. This represents the original area of ​​the pile base. This refers to the enlarged area at the bottom of the pile. To expand the effect coefficient, The unit side friction resistance at the pile-soil interface. For the first Segment length of pile body This is the extension length of the anchor rod. The angle of rotation of the anchor rod. For the pile diameter, This refers to the number of anchor rods in a single layer. For the cohesion of the soil, This refers to the contact area between the anchor rod and the soil. For effective vertical stress, The internal friction angle of the soil. The width of the anchor rod;

[0022] The uplift bearing capacity of the spliced ​​pile foundation The calculation formula is:

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] in, For the pull-out resistance of the pile foundation; For the pull-out resistance of the anchor rod, This is the self-weight of the soil at the bottom of the pile after the pile foundation is enlarged. The buoyant unit weight of the soil. This refers to the height of the enlarged portion of the pile foundation.

[0028] A spliced ​​pile foundation for river network areas includes: multiple pile bodies connected sequentially from top to bottom and a central column; internal reinforcing steel plates connecting adjacent pile bodies; the central column coaxially disposed inside the pile bodies and connected to the multiple internal reinforcing steel plates; a vertical rod sleeved on the inner side of the central column; the lower end of the vertical rod passing through the central column and connected to a base plate; the base plate being connected to the bottom end of the lowest pile body; multiple annular high-strength steel blocks spaced axially on the outer circumference of the central column; an angle adjustment component connected to the outer side of the annular high-strength steel blocks; multiple anchor piles connected to the angle adjustment component; and one end of each anchor pile passing through the pile body and located within the soil.

[0029] The pile body comprises multiple pile body pieces sequentially spliced ​​along the circumference. One side of each pile body piece is connected to a tenon, and the other side of each pile body piece is provided with a mortise that mates with the tenon. The upper end face of each pile body piece is connected to a protruding end. The inner side wall of each pile body piece is provided with an anchoring rod hole for the anchoring rod to pass through. The lower end face of each pile body piece is provided with a mortise that mates with the protruding end. Two pile body pieces located in adjacent upper and lower layers are connected to each other by arc bolts. The upper side of the base plate is connected to the protruding end.

[0030] The central column includes multiple variable cross-section columns arranged at intervals along the vertical direction. The diameter of the multiple variable cross-section columns increases from top to bottom. Multiple annular high-strength steel blocks are respectively sleeved on the outside of the multiple variable cross-section columns, and the lower end face of the annular high-strength steel block is attached to the upper end face of the adjacent variable cross-section column.

[0031] The angle adjustment component has multiple angle holes with different angles. The anchor rod includes an angle rod, a first connecting rod, and a second connecting rod. One end of the angle rod is connected to the angle adjustment component by a high-strength bolt, and the other end of the angle rod is connected to one of the angle holes by an angle bolt. One end of the first connecting rod is connected to the other end of the angle rod by the angle bolt. The second connecting rod is slidably connected to the other end of the first connecting rod. The first connecting rod has a mortar groove, a mortar channel, and multiple sliding grooves. The multiple sliding grooves and mortar channels are all connected to the mortar groove. The mortar groove is filled with expanding mortar. Each of the multiple sliding grooves has a sliding rod slidably connected to one end of the second connecting rod. The other end of the first connecting rod and one end of the second connecting rod are interlocked by a snap-fit ​​component.

[0032] The upper end of the vertical rod is connected to a high-strength nut, and the lower end of the vertical rod is connected to a spiral connector. The outer circumferential surface of the spiral connector is provided with multiple sliding hinge supports. The outer sides of each of the multiple sliding hinge supports are hinged to a first connecting rod. The first connecting rod has a mortar groove, a mortar channel, and multiple sliding grooves. The multiple sliding grooves and mortar channels are all connected to the mortar groove. The mortar groove is filled with expanding mortar. Each of the multiple sliding grooves is slidably connected to a sliding rod. One end of each of the multiple sliding rods is connected to a second connecting rod. The base plate includes a central pile plate and multiple extended pile plates. The central pile plate is sleeved on the outer circumferential surface of the vertical rod. The multiple extended pile plates are attached to the lower side of the central pile plate in the circumferential direction. The inner sides of the multiple extended pile plates are connected to one end of each of the multiple second connecting rods.

[0033] The reinforcing steel sheet includes a steel ring and a plurality of crossbars arranged along the circumference. One end of the plurality of crossbars is connected to the outer circumferential surface of the central column, and the other end of the plurality of crossbars is connected to the inner side of the steel ring. A plurality of first protrusions are arranged at intervals along the circumference on the inner side of the steel ring. One end of the steel ring is provided with a one-way limiting groove. A plurality of second protrusions are arranged at intervals on the inner side of the one-way limiting groove. The plurality of second protrusions are engaged and connected with the plurality of first protrusions at the other end of the steel ring.

[0034] A construction method for spliced ​​pile foundations in river network areas, the construction method comprising the following steps:

[0035] Excavate an installation pit in the soil and then level the ground of the installation pit.

[0036] On the ground, use mechanical clamps to hold the upper end of the vertical rod and put the vertical rod into the installation pit until the base plate contacts the inner bottom wall of the installation pit;

[0037] After laying a layer of piles, a ring-shaped high-strength steel block is placed on the central column. Multiple anchor rods are connected to the ring-shaped high-strength steel block. The elongation length and anchoring angle of the anchor rods are adjusted by the angle adjustment component so that the anchor rods pass through the pile and are located in the soil.

[0038] On top of the laid pile body, lay another layer of pile body. The two layers of pile body are connected by reinforcing steel plates. Then install anchor rods. Repeat the above operation until all pile bodies and anchor rods are installed. After completion, pour concrete into the pile body.

[0039] The installation pit is backfilled and the soil in the installation pit is compacted. At this point, the installation of the device is complete.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. This invention discloses a spliced ​​pile foundation for river network areas, along with its design and construction methods. By introducing a comprehensive soil state index system, the soil can be classified and its bearing capacity accurately quantified. This allows for dynamic adjustments to the rotation angle and elongation of the anchor rods, as well as the enlarged area of ​​the pile foundation bottom, based on the bearing capacity. This effectively adapts to complex geological conditions in soft soil areas. Simultaneously, the combination of modular prefabricated components and high-strength steel reduces on-site work, facilitating construction and shortening the construction cycle. The rapid splicing of multiple prefabricated piles significantly improves overall construction efficiency. Therefore, this invention has relatively low design difficulty and is convenient to construct.

[0042] 2. In this invention, a spliced ​​pile foundation for river network areas, along with its design and construction methods, the pile segments are rapidly assembled using a mortise and tenon structure. The longitudinal splice joints are staggered and secured with arc bolts, significantly improving the shear strength of the pile. This method is particularly suitable for flexible construction in narrow, muddy terrain of soft soil areas within river networks, thus increasing construction efficiency. The central column employs a variable cross-section design, incorporating multiple high-strength annular steel blocks to expand the cross-section, thereby optimizing stress distribution, reducing local stress concentration, and significantly extending the foundation's service life. A mechanical expansion mechanism drives the expansion of the outward-extending pile segments, increasing the pile foundation's expansion area and significantly enhancing the foundation's bearing capacity. Simultaneously, it reduces concrete usage, balancing efficient construction with environmental protection requirements. Therefore, this invention offers convenient construction, high construction efficiency, and high structural stability.

[0043] 3. In this invention, a spliced ​​pile foundation for river network areas, along with its design and construction methods, multi-angle adaptation is achieved through angle adjustment components. The anchor rods utilize a sliding connection between a first connecting rod and a second connecting rod. After the second connecting rod slides, the expanding mortar in the mortar groove flows out through the chute and mortar channel, filling the pores and the gaps between the two connecting rods, thereby increasing the anchoring force of the anchor rods and significantly enhancing the synergy between the soil and the structure. The sliding of the second connecting rod at the bottom causes the outward-extending pile segments to expand outward, thus increasing the pile base area. This method is simple to operate and requires no large machinery, saving manpower and equipment costs. Furthermore, the internally reinforcing steel plate at the central column connection joint expands unidirectionally against the inner wall of the pile body by applying torque to the crossbar, forming a circumferential "stirrup effect," which also improves crack resistance, effectively preventing water seepage and misalignment of the splice joint, further strengthening structural stability. Therefore, this invention is convenient to use and has high structural stability.

[0044] 4. In this invention, a spliced ​​pile foundation for river network areas, along with its design and construction methods, the use of prefabricated components and modular assembly processes reduces earthwork excavation, significantly minimizing disturbance to sensitive ecosystems in soft soil areas and avoiding soil erosion problems caused by traditional construction methods. The components are prefabricated using concrete and high-strength steel, supporting reuse and reducing construction waste, thus meeting green construction standards. Simultaneously, dynamic design optimization reduces material waste, and mechanical widening of the base reduces concrete usage, resulting in efficient and low-consumption construction. Combined with staggered joints, widened base design, and multiple shear-resistant mechanisms including internal reinforcing steel plates, the displacement of the pile foundation under flood erosion or seismic loads is reduced, significantly improving overturning resistance and disaster resistance. This achieves a balance between lightweight structure and economy, with dynamic design and significantly improved overall cost-effectiveness. Therefore, this invention offers lower cost, lighter structure, and higher structural stability. Attached Figure Description

[0045] Figure 1 This is a flowchart of a design method for spliced ​​pile foundations in river network areas according to the present invention.

[0046] Figure 2 This is a schematic diagram of a spliced ​​pile foundation in a river network area according to the present invention.

[0047] Figure 3 This is a schematic diagram of the structure of two adjacent pile bodies in this invention.

[0048] Figure 4 This is a schematic diagram of the pile body in this invention.

[0049] Figure 5 This is a structural schematic diagram of the central column, vertical rod, and base plate in this invention.

[0050] Figure 6This is a schematic diagram of the structure of the annular high-strength steel block, the angle adjustment component, and the anchor rod in this invention.

[0051] Figure 7 This is a partial cross-sectional schematic diagram of the anchor rod in this invention.

[0052] Figure 8 This is a schematic diagram of the reinforcing steel sheet in this invention.

[0053] Figure 9 This is a partially enlarged schematic diagram of the unidirectional limiting groove, steel ring, first protrusion, and second protrusion in this invention.

[0054] Figure 10 This is a schematic diagram of the structure of the expanded bottom plate, vertical rod, spiral connector, torque lock, outer rod, and inner rod in this invention.

[0055] Figure 11 yes Figure 10 Enlarged diagram of point A in the middle.

[0056] Figure 12 This is a schematic diagram of the structure of the base plate, vertical rod, spiral connector, torque lock, outer rod, and inner rod in this invention.

[0057] Figure 13 yes Figure 12 Enlarged diagram of point A in the middle.

[0058] Figure 14 This is a partial cross-sectional schematic diagram of the base plate, vertical rod, spiral connector, torque lock, outer rod, and inner rod in this invention.

[0059] In the diagram: 1. Pile body 11. Pile body piece 12. Tenon 13. Mortise 14. Concave end 15. Anchor rod opening 16. Arc bolt 17. Central column 2. Variable cross-section column 21. Anchor rod 3. First connecting rod 31. Second connecting rod 32. Mortar groove 33. Angle rod 34. Mortar channel 35. Slide groove 36. Slide rod 37. Clip 38. Base plate 4. Central pile piece 41. Outward pile piece 42. Slot 43. Spring 44. Electromagnet 45. Buckle 46. Lock 47. Installation groove 48. Metal block 49. Ring high-strength steel block 5. Angle adjustment piece 6. High-strength bolt 61. Angle bolt 62. Angle hole 63. Internal reinforcing steel plate 7. Horizontal bar 71. One-way limiting groove 72. Steel ring 73. First protrusion 74. Second protrusion 75. Vertical bar 8. High-strength nut 81. Spiral connector 9. Sliding hinge support 10. Detailed Implementation

[0060] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0061] Example 1:

[0062] See Figure 1 A design method for spliced ​​pile foundations in river network areas, the design method comprising the following steps:

[0063] Step 1: First, determine the cohesion, internal friction angle, effective vertical stress, liquidity index, and void ratio of the soil in the installation pit of the spliced ​​pile foundation. Then, calculate the comprehensive state index of the soil based on the cohesion, internal friction angle, effective vertical stress, liquidity index, and void ratio.

[0064] Step 2: Classify the soil according to the comprehensive soil state index and evaluate the soil bearing capacity;

[0065] Step 3: Based on the soil bearing capacity evaluation results, the total bearing capacity of the spliced ​​pile foundation is changed by adjusting the rotation angle and extension length of anchor rod 3 and the enlarged area of ​​the pile bottom to meet the design requirements.

[0066] In this embodiment, the enlarged area refers to the total area of ​​the pile foundation after the pile bottom is enlarged minus the total area before the pile bottom is enlarged. The soil comprehensive state index... The calculation method is as follows:

[0067] ;

[0068] in, For the cohesion of the soil, For effective vertical stress, It is the internal friction angle. Liquidity index, Porosity;

[0069] In the calculation formula, the numerator represents the shear strength of the soil, and the larger the value, the higher the bearing capacity. The denominator represents the softness and compressibility of the soil, and the larger the value, the lower the bearing capacity.

[0070] Example 2:

[0071] The basic content is the same as in Example 1, except that:

[0072] The method of classifying soil and evaluating its bearing capacity based on the comprehensive soil state index is as follows:

[0073] If the soil comprehensive state index is less than 5, the soil is extremely soft and mobile soil with extremely low bearing capacity.

[0074] If the soil comprehensive state index is greater than or equal to 5 and less than 20, the soil is low-strength, high-compressibility soil with low bearing capacity.

[0075] If the soil comprehensive state index is greater than or equal to 20 and less than 50, the soil is medium-strength plastic soil with medium bearing capacity.

[0076] If the soil comprehensive state index is greater than or equal to 50, the soil is high-strength, low-compressibility soil with high bearing capacity.

[0077] In this embodiment, when the soil bearing capacity is extremely low, deep reinforcement is required; when the soil bearing capacity is low and the bearing risk is high, moderate reinforcement is required; when the soil bearing capacity is moderate and the bearing risk is moderate, local reinforcement is required; when the bearing capacity is high and the bearing risk is low, no reinforcement is required, and the natural foundation bearing capacity can be directly utilized, which can avoid excessive disturbance to the stable soil and reduce construction costs.

[0078] Reinforcement is achieved by dynamically adjusting the rotation angle and extension length of the anchor rod 3, as well as the enlarged area of ​​the pile bottom.

[0079] Example 3:

[0080] The basic content is the same as in Example 1, except that:

[0081] The total bearing capacity of the spliced ​​pile foundation The calculation formula is:

[0082] ;

[0083] ;

[0084] ;

[0085] ;

[0086] ;

[0087] in, For the bearing capacity of the pile foundation itself, For the pile bottom resistance, For the side friction of the pile body, Add bearing capacity to anchor rod 3 The ultimate end resistance of the soil at the pile tip. This represents the original area of ​​the pile base. This refers to the enlarged area at the bottom of the pile. To expand the effect coefficient, The unit side friction resistance at the pile-soil interface. For the first Segment length of pile body This is the extension length of anchor rod 3. The rotation angle of anchor rod 3. For the pile diameter, This refers to the number of single-layer anchor rods 3. For the cohesion of the soil, This represents the contact area between anchor rod 3 and the soil. For effective vertical stress, The internal friction angle of the soil. The width of anchor rod 3;

[0088] The uplift bearing capacity of the spliced ​​pile foundation The calculation formula is:

[0089] ;

[0090] ;

[0091] ;

[0092] ;

[0093] in, For the pull-out resistance of the pile foundation; For the pull-out resistance of anchor rod 3, This is the self-weight of the soil at the bottom of the pile after the pile foundation is enlarged. The buoyant unit weight of the soil. This refers to the height of the enlarged portion of the pile foundation.

[0094] In this embodiment, A value of 0.6-0.8 is used in soft soil and 1.0 is used in hard soil to prevent local shear failure of the soil. The Pa values ​​were taken as 5-15 kPa in silty clay. The angle between anchor rod 3 and the horizontal plane;

[0095] Extremely soft and fluid soil requires over-expanded pile foundations ( =2.0-2.5) combined with multi-layer large elongation anchor rods ( =1.5-2.0m =15°-25°) to penetrate the weak layer and activate the soil's pull-out resistance;

[0096] Low-strength, high-compressibility soils require significant base enlargement ( =1.5-2.0) with medium elongation anchor rod ( =1.0-1.5m =20°-30°), so that the anchor rod 3 is tilted downward to provide pull-out resistance, and the widened base reduces the risk of pile tip penetration;

[0097] Medium-strength plastic soil adopts moderately enlarged base ( =1.2-1.5) combined with short anchor rods ( =0.5-1.0m、 =30°-45°), the compaction of the sand is enhanced by the lateral compression of the anchor rod 3, and the resistance at the bottom of the pile is increased;

[0098] High-strength, low-compressibility soils do not require the use of anchor rods 3 ( =0), no need to enlarge the pile bottom ( =1.0), directly utilizing the bearing capacity of the natural foundation can avoid excessive disturbance to the stable soil and reduce construction costs.

[0099] Example 4:

[0100] See Figure 2 A spliced ​​pile foundation for river network areas, applied in the design method of spliced ​​pile foundation in river network areas according to Embodiment 1, includes: multiple pile bodies 1 connected sequentially from top to bottom and a central column 2. An inner reinforcing steel plate 7 is connected between two adjacent pile bodies 1. The central column 2 is coaxially arranged on the inner side of the pile body 1 and connected to the multiple inner reinforcing steel plates 7. A vertical rod 8 is sleeved on the inner side of the central column 2. The lower end of the vertical rod 8 passes through the central column 2 and is connected to a base plate 4. The base plate 4 is connected to the bottom end of the lowest pile body 1. Multiple annular high-strength steel blocks 5 are axially spaced on the outer circumference of the central column 2. An angle adjustment component 6 is connected to the outer side of the annular high-strength steel block 5. Multiple anchor rods 3 are connected to the angle adjustment component 6. One end of the multiple anchor rods 3 passes through the pile body 1 and is located in the soil.

[0101] In this embodiment, the pile body 1, hollow central column 2, and base plate 4 are prefabricated using concrete blocks, while the remaining components are prefabricated using high-strength steel. The concrete and steel are connected by pouring to form a whole. In application, given that the soil in river network areas is relatively soft and the foundation is mostly soft soil, the traditional foundations of the structures, such as power transmission towers, which are often constructed on river networks, may present difficulties in transportation and installation. For such soft soil areas, the pile foundation in this embodiment can be used as the foundation of the structure.

[0102] Example 5:

[0103] The basic content is the same as Example 4, except that:

[0104] See Figure 3 and Figure 4 The pile body 1 includes multiple pile body pieces 11 that are sequentially spliced ​​along the circumference. One side of each pile body piece 11 is connected to a tenon 12, and the other side of each pile body piece 11 is provided with a mortise 13 that mortise and tenon with the tenon 12. The upper end face of each pile body piece 11 is connected to a protrusion 15. The inner side wall of each pile body piece 11 is provided with an anchor rod hole 16 for the anchor rod 3 to pass through. The lower end face of each pile body piece 11 is provided with a mortise and tenon with the protrusion 15. Two pile body pieces 11 located in adjacent upper and lower layers are connected to each other by arc bolts 17. The upper side of the base plate 4 is connected to the protrusion 15.

[0105] In this embodiment, the connection method is to first place the pile body piece 11 in the designated position, and then connect its protruding tenon 12 with the concave tenon 13 of another pile body piece 11 to form a complete pile body 1. After each pile body 1 is spliced, the concave end 14 of the upper pile body 1 is aligned with the protruding end 15 of the lower pile body 1 and inserted to ensure that the longitudinal splicing seams of the pile body 1 are in an interlaced arrangement to ensure its shear resistance.

[0106] Example 6:

[0107] The basic content is the same as Example 4, except that:

[0108] See Figure 5 The central column 2 includes a plurality of variable cross-section columns 21 arranged at intervals along the vertical direction. The diameter of the plurality of variable cross-section columns 21 increases from top to bottom. A plurality of annular high-strength steel blocks 5 are respectively sleeved on the outside of the plurality of variable cross-section columns 21, and the lower end face of the annular high-strength steel block 5 is attached to the upper end face of the adjacent variable cross-section column 21.

[0109] In this embodiment, the central column 2 is hollow, and the larger section of the variable cross-section column 21 is enlarged by an arc to better connect the lower part of the annular high-strength steel block 5 and reduce stress concentration.

[0110] Example 7:

[0111] The basic content is the same as Example 4, except that:

[0112] See Figure 6 and Figure 7 The angle adjustment component 6 has multiple angle holes 63 with different angles. The anchor rod 3 includes an angle rod 34, a first connecting rod 31, and a second connecting rod 32. One end of the angle rod 34 is connected to the angle adjustment component 6 by a high-strength bolt 61, and the other end of the angle rod 34 is connected to one of the angle holes 63 by an angle bolt 62. One end of the first connecting rod 31 is connected to the other end of the angle rod 34 by the angle bolt 62. The second connecting rod 32 is slidably connected to the other end of the first connecting rod 31. The first connecting rod 31 has a mortar groove 33, a mortar channel 35, and multiple sliding grooves 36. The multiple sliding grooves 36 and the mortar channel 35 are all connected to the mortar groove 33. The mortar groove 33 is filled with expanding mortar. Each of the multiple sliding grooves 36 is slidably connected to a sliding rod 37. The multiple sliding rods 37 are connected to one end of the second connecting rod 32. The other end of the first connecting rod 31 and one end of the second connecting rod 32 are interlocked by a snap-fit ​​component 38.

[0113] In this embodiment, the angle adjustment component 6 has angle holes 63 corresponding to different angles, which are used to connect with the anchor rod 3 and adjust the angle. The outside of the first connecting rod 31 can be provided with multiple small holes. An expansion agent is placed in the small holes to make the expansion mortar expand. At the same time, the second connecting rod 32 can slide by hydraulic drive. When sliding, the expansion mortar flows out from the mortar channel 35 and multiple grooves 36. When the second connecting rod 32 slides to the point where the two snap-fit ​​pieces 38 snap-fit ​​each other, the anchor rod 3 is completed to extend. The snap-fit ​​pieces 38 are coated with a rubber adhesive substance. After the two snap-fit ​​pieces 38 come into contact with each other, they are bonded by the rubber adhesive substance.

[0114] Example 8:

[0115] The basic content is the same as Example 4, except that:

[0116] See Figures 10 to 14 The upper end of the vertical rod 8 is connected to a high-strength nut 81, and the lower end of the vertical rod 8 is connected to a spiral connector 9. Multiple sliding hinge supports 10 are arranged circumferentially on the outer periphery of the spiral connector 9. A first connecting rod 31 is hinged to the outer side of each of the multiple sliding hinge supports 10. The first connecting rod 31 has a mortar groove 33, a mortar channel 35, and multiple sliding grooves 36. The multiple sliding grooves 36 and mortar channels 35 are all connected to the mortar groove 33. The interior is filled with expanding mortar, and each of the multiple sliding grooves 36 is slidably connected with a sliding rod 37. One end of each sliding rod 37 is connected to a second connecting rod 32. The base plate 4 includes a central pile plate 41 and multiple extended pile plates 42. The central pile plate 41 is sleeved on the outer circumferential surface of the vertical rod 8. The multiple extended pile plates 42 are attached to the lower side of the central pile plate 41 in the circumferential direction. The inner side of each extended pile plate 42 is connected to one end of each of the multiple second connecting rods 32.

[0117] In this embodiment, a slot 43 is provided on the outer side of the central pile piece 41, and an installation slot 48 is provided on the inner side of the extended pile piece 42. An electromagnet 45 is connected in the installation slot 48, and a spring 44 is sleeved on the outside of the electromagnet 45. The spring 44 is initially in a compressed state. A metal block 49 is connected to one end of the spring 44. The metal block 49 and the electromagnet 45 are attracted by opposite poles. A locking 47 that matches the slot 43 is connected to one end of the metal block 49. Buckles 46 are connected to the inner wall of the installation slot 48 and the outer wall of the locking 47.

[0118] During the expansion process, the second connecting rod 42 can be extended by hydraulic drive, or multiple small holes can be opened on the first connecting rod 41, and an expanding agent can be injected into the holes. After the expanding agent comes into contact with the expanding mortar, the expanding mortar expands rapidly, thereby driving the second connecting rod 42 to extend outward and the extended pile piece 42 to expand outward until the second connecting rod 42 extends to the designated position. At this time, the electromagnet 45 on the extended pile piece 42 is de-energized, the spring 44 is stretched and reset, and the metal block 49 and the locking 47 extend outward into the locking groove 43 until the buckles 46 coated with rubber adhesive overlap each other, so that the extended pile piece 42 and the central pile piece 41 are connected to form a whole, providing pull-out resistance for the pile body.

[0119] Example 9:

[0120] The basic content is the same as Example 4, except that:

[0121] See Figure 8 and Figure 9 The inner reinforcing steel plate 7 includes a steel ring 73 and a plurality of crossbars 71 arranged along the circumferential direction. One end of the plurality of crossbars 71 is connected to the outer circumferential surface of the central column 2, and the other end of the plurality of crossbars 71 is connected to the inner side of the steel ring 73. A plurality of first protrusions 74 are arranged at intervals along the circumferential direction on the inner side of the steel ring 73. One end of the steel ring 73 is provided with a one-way limiting groove 72. A plurality of second protrusions 75 are arranged at intervals along the inner side of the one-way limiting groove 72. The plurality of second protrusions 75 are engaged and connected with the plurality of first protrusions 74 at the other end of the steel ring 73.

[0122] In this embodiment, by rotating the vertical rod 8, the inner reinforcing steel plate 7 rotates within the pile body 1, causing one end of the steel ring 73 to move in the one-way limiting groove 72, causing the steel ring 73 to expand and fit tightly against the gap in the inner wall of the pile body. After expansion, the first protrusion 74 and the second protrusion 75 are engaged together to achieve connection and fixation.

[0123] Example 10:

[0124] A construction method for a spliced ​​pile foundation in a river network area, wherein the construction method is applied to a spliced ​​pile foundation in a river network area as described in Example 4, and the construction method includes the following steps:

[0125] According to the survey and design, and based on the design drawings, a total station was used to mark the center point and outline of the installation pit, and ash lines were sprinkled to mark the location. Before excavating the installation pit, a positioning template for the anchor rod opening was pre-embedded to ensure the accurate installation position of the subsequent anchor rod 3. Mechanical excavation was carried out to the design elevation, and the base was manually cleaned down to a solid soil layer. A 300mm graded crushed stone cushion layer was laid, compacted, and leveled. The pre-embedded position of the pile body piece 11 was checked to ensure it matched the dimensions of the pit, and the adjustment error was ≤10mm.

[0126] The vertical rod 8 connecting the base plate 4 is hoisted into the designated position in the installation pit and its verticality is adjusted to ensure that the deviation is less than or equal to 1‰. The top is positioned and fixed by mechanically clamping the high-strength nut 81, and then the variable cross-section center column 21 is placed in. Epoxy resin is applied to the tenons 12, mortises 13, concave ends 14, and convex ends 15 of all components. After completion, the bottom pile body 1 is spliced ​​first. The bottom groove 14 of a pile body piece 11 is aligned with the groove 15 of the base plate 4 and fixed to the base plate 4. Then, the remaining two pile body pieces 11 are spliced ​​in sequence through the tenons 12 and mortises 13 on the side ends of the pile body piece 11. 1. After the splicing is completed, the annular high-strength steel block 5 is embedded into the arc-shaped enlarged surface of the variable cross-section column 21. Through the angle hole 63 on the angle adjustment piece 6 and the angle bolt 62, the angle rod 34 and the anchor rod 3 are rotated and form a certain angle with the pile body. After the angle is adjusted, the anchor rod 3 is inserted into the soil through the anchor rod opening 16. The second connecting rod 32 is subjected to tension, so that the second connecting rod 32 is extended. When the snap-fit ​​pieces 38 come into contact with each other, the designed anchor length and anchor angle are achieved. The expansion mortar in the mortar groove 33 flows out through the mortar channel 35 and the slide 36 until the mortar overflows from the hole, thus achieving the effect of strengthening the stability of the pile body.

[0127] Then, the vertical seams of the two adjacent pile bodies 1 are staggered, and the next pile body 1 is spliced ​​according to the steps of the bottom pile body. After the two adjacent pile bodies are spliced, an inner reinforcing steel plate 7 connected by several surrounding horizontal bars 71 is inserted into the outside of the central column 21. The high-strength nut 81 at the top of the vertical bar 8 is rotated using external machinery, and torque is applied to the horizontal bar 71 to expand the inner reinforcing steel plate 7, which drives the end of the steel ring 73 to penetrate into the one-way limiting groove 72 and fit tightly against the gap of the inner wall of the pile body to ensure circumferential reinforcement. Then, the upper and lower adjacent pile body plates 11 are internally bolted together with arc bolts 17 so that the inner and outer sides of the pile body are reinforced at the same time to ensure the stability of the pile body.

[0128] Following the steps above, the pile body 1, anchor rod 3, upper layer pile body 1, inner reinforcing steel plate 7, and connecting bolt 17 are sequentially spliced ​​upwards until the pile structure is completed. After the splicing is completed, the second connecting rod 32 at the bottom is driven to drive the outward extension pile plate 42 to expand outwards, and the error of the expanded bottom diameter is monitored to be less than or equal to 5%, so as to achieve the purpose of expanding the pile bottom. After the expansion is completed, micro-expansion concrete is injected in layers in the hollow part inside the pile body. After each layer is stirred evenly, the next layer of concrete is injected. After it sets, it is cured for seven days to form a spliced ​​pile foundation.

[0129] Backfill and inspect the foundation pit. Remove stones with a particle size greater than 50 mm from the backfill soil. The loose laying thickness for each layer is 300 mm, and it is compacted 6 times with a rammer. The compaction degree is ≥ 95%. Embed the grounding electrode (galvanized flat steel 50×5 mm) and weld it to the vertical rod 8. The final acceptance is carried out by a static load test with the load increased to 1.5 times the design value. The settlement less than or equal to 10 mm / 2h is qualified. Sort out the construction records and submit the quality inspection reports of components such as the pile body slice 11 and the anchor rod 3.

[0130] Example 11:

[0131] During the construction process, a real-time monitoring and feedback system can be set up to monitor during pile sinking, and the pile pressing force and depth are recorded in real time. When the pile pressing force is lower than 80% of the design value, the anchor rod 3 is triggered to extend in stages;

[0132] When the soil layer resistance is insufficient every 2 m, it increases by 0.3 m (the maximum does not exceed the design value);

[0133] Dynamically adjust according to the soil layer , 20° - 30° downward for soft clay, 45° - 60° horizontally for sandy soil;

[0134] When the pile bottom expands to reach the design area after that, inject cement mortar to solidify the pile end soil;

[0135] When the resistance is insufficient, the anchor rod 3 is automatically triggered to extend by hydraulic drive, and it cooperates with the expansive mortar in the mortar groove 33 to strengthen and form a synergistic bearing mechanism. Finally, the bearing capacity improvement effect is verified through static load tests and numerical simulations, and the pile body parameter design is adjusted according to the actual situation on site, forming an integrated reinforcement system of "soil quality diagnosis - parametric design - dynamic construction - effect closed-loop", realizing the comprehensive improvement of the safety, economy and adaptability of pile foundation projects in soft soil areas.

[0136] Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method of designing a patchwork pile foundation in a river network area, characterized by, The design method includes the following steps: First, determine the cohesion, internal friction angle, effective vertical stress, liquidity index, and void ratio of the soil in the installation pit for the spliced ​​pile foundation. Then, calculate the comprehensive soil state index based on the cohesion, internal friction angle, effective vertical stress, liquidity index, and void ratio. : ； in, For the cohesion of the soil, For effective vertical stress, It is the internal friction angle. The liquidity index, Porosity; Soil is classified and its bearing capacity is evaluated based on the comprehensive soil state index. Based on the soil bearing capacity evaluation results, the total bearing capacity and pull-out bearing capacity of the spliced ​​pile foundation are changed by adjusting the rotation angle and extension length of the anchor rod (3) and the enlarged area of ​​the pile bottom, so as to meet the design requirements.

2. The design method of the spliced pile foundation of the river network area according to claim 1, characterized in that: The method of classifying soil and evaluating its bearing capacity based on the comprehensive soil state index is as follows: If the soil comprehensive state index is less than 5, the soil is extremely soft and mobile soil with extremely low bearing capacity. If the soil comprehensive state index is greater than or equal to 5 and less than 20, the soil is low-strength, high-compressibility soil with low bearing capacity. If the soil comprehensive state index is greater than or equal to 20 and less than 50, the soil is medium-strength plastic soil with medium bearing capacity. If the soil comprehensive state index is greater than or equal to 50, the soil is high-strength, low-compressibility soil with high bearing capacity.

3. The design method for spliced ​​pile foundations in river network areas according to claim 2, characterized in that: The total bearing capacity of the spliced pile foundation The calculation formula is: ； ； ； ； ； in, For the bearing capacity of the pile foundation itself, For the pile bottom resistance, For the side friction of the pile body, To add bearing capacity to the anchor rod (3), The ultimate end resistance of the soil at the pile tip. This represents the original area of ​​the pile base. This refers to the enlarged area at the bottom of the pile. To expand the effect coefficient, The unit side friction resistance at the pile-soil interface. For the first Segment length of pile body The extension length of the anchor rod (3) is given. The rotation angle of the anchor rod (3) For the pile diameter, The number of single-layer anchor rods (3), For the cohesion of the soil, The contact area between the anchor rod (3) and the soil. For effective vertical stress, The internal friction angle of the soil. The width of the anchor rod (3); The uplift bearing capacity of the spliced ​​pile foundation The calculation formula is: ； ； ； ； wherein, is the uplift resistance of the pile foundation; is the uplift resistance of the anchoring rod (3), is the self-weight of the soil at the bottom of the enlarged pile, is the buoyant density of the soil, is the height of the enlarged part of the pile foundation.

4. A hybrid pile foundation for a river network region, characterized by, The spliced ​​pile foundation is applied to the design method of spliced ​​pile foundation in river network areas as described in any one of claims 1 to 3. The spliced ​​pile foundation includes: multiple pile bodies (1) connected sequentially from top to bottom and a central column (2). An inner reinforcing steel plate (7) is connected between two adjacent pile bodies (1). The central column (2) is coaxially arranged on the inner side of the pile body (1) and connected to the multiple inner reinforcing steel plates (7). A vertical rod (8) is sleeved on the inner side of the central column (2). The lower end of the vertical rod (8) passes through the central column (2) and is connected to the base plate (4). The base plate (4) is connected to the bottom end of the pile body (1) located at the bottom. Multiple annular high-strength steel blocks (5) are arranged at axial intervals on the outer circumference of the central column (2). An angle adjustment component (6) is connected to the outer side of the annular high-strength steel block (5). Multiple anchor rods (3) are connected to the angle adjustment component (6). One end of the multiple anchor rods (3) passes through the pile body (1) and is located in the soil.

5. A hybrid pile foundation for a river network region according to claim 4, characterized in that: The pile body (1) includes multiple pile body pieces (11) that are sequentially spliced ​​along the circumferential direction. One side of the pile body piece (11) is connected to a tenon (12), and the other side of the pile body piece (11) is provided with a mortise (13) that mortise and tenon with the tenon (12). The upper end face of the pile body piece (11) is connected to a protrusion (15). The inner side wall of the pile body piece (11) is provided with an anchor rod hole (16) for the anchor rod (3) to pass through. The lower end face of the pile body piece (11) is provided with a mortise and tenon with the protrusion (15). Two pile body pieces (11) located in adjacent upper and lower layers are connected to each other by arc bolts (17). The upper side of the base plate (4) is connected to the protrusion (15).

6. A spliced ​​pile foundation for river network areas according to claim 4, characterized in that: The central column (2) includes multiple variable cross-section columns (21) arranged sequentially and at intervals along the vertical direction. The diameter of the multiple variable cross-section columns (21) increases sequentially from top to bottom. Multiple annular high-strength steel blocks (5) are respectively sleeved on the outside of the multiple variable cross-section columns (21). The lower end face of the annular high-strength steel block (5) is attached to the upper end face of the adjacent variable cross-section column (21).

7. A hybrid pile foundation for a river network region according to claim 4, characterized in that: The angle adjusting member (6) has multiple angle holes (63) with different angles. The anchor rod (3) includes an angle rod (34), a first connecting rod (31), and a second connecting rod (32). One end of the angle rod (34) is connected to the angle adjusting member (6) by a high-strength bolt (61), and the other end of the angle rod (34) is connected to one of the angle holes (63) by an angle bolt (62). One end of the first connecting rod (31) is connected to the other end of the angle rod (34) by the angle bolt (62), and the second connecting rod (32) is slidably connected. The first connecting rod (31) is connected to the other end of the first connecting rod (31). The first connecting rod (31) is provided with a mortar groove (33), a mortar channel (35) and a plurality of sliding grooves (36). The plurality of sliding grooves (36) and the mortar channel (35) are all connected to the mortar groove (33). The mortar groove (33) is filled with expanding mortar. The plurality of sliding grooves (36) are slidably connected with sliding rods (37). The plurality of sliding rods (37) are connected to one end of the second connecting rod (32). The other end of the first connecting rod (31) and one end of the second connecting rod (32) are interlocked by a snap-fit ​​member (38).

8. A spliced ​​pile foundation for river network areas according to claim 4, characterized in that: The upper end of the vertical rod (8) is connected to a high-strength nut (81), and the lower end of the vertical rod (8) is connected to a spiral connector (9). Multiple sliding hinge supports (10) are arranged circumferentially on the outer periphery of the spiral connector (9). A first connecting rod (31) is hinged to the outer side of each of the multiple sliding hinge supports (10). A mortar groove (33), a mortar channel (35), and multiple sliding grooves (36) are provided inside the first connecting rod (31). The multiple sliding grooves (36) and mortar channels (35) are all connected to the mortar groove (33). 3) The interior is filled with expanding mortar, and each of the multiple sliding grooves (36) is slidably connected with a sliding rod (37). One end of each sliding rod (37) is connected to a second connecting rod (32). The base plate (4) includes a central pile piece (41) and multiple extended pile pieces (42). The central pile piece (41) is sleeved on the outer circumferential surface of the vertical rod (8). The multiple extended pile pieces (42) are attached to the lower side of the central pile piece (41) along the circumferential direction. The inner side of each extended pile piece (42) is connected to one end of each of the multiple second connecting rods (32).

9. A hybrid pile foundation for a river network region according to claim 4, characterized in that: The inner reinforcing steel sheet (7) includes a steel ring (73) and a plurality of crossbars (71) arranged along the circumferential direction. One end of the plurality of crossbars (71) is connected to the outer circumferential surface of the central column (2), and the other end of the plurality of crossbars (71) is connected to the inner side of the steel ring (73). A plurality of first protrusions (74) are arranged at intervals along the circumferential direction on the inner side of the steel ring (73). One end of the steel ring (73) is provided with a one-way limiting groove (72). A plurality of second protrusions (75) are arranged at intervals along the inner side of the one-way limiting groove (72). The plurality of second protrusions (75) are connected to the plurality of first protrusions (74) at the other end of the steel ring (73).

10. The method for constructing the spliced pile foundation in the river network region according to claim 4, characterized in that: The construction method includes the following steps: Excavate an installation pit in the soil and then level the ground of the installation pit. On the ground, use a mechanical clamp to hold the upper end of the vertical rod (8) and put the vertical rod (8) into the installation pit until the bottom plate (4) contacts the inner bottom wall of the installation pit; Lay a layer of pile body (1). After the laying is completed, place a ring-shaped high-strength steel block (5) on the central column (2). Multiple anchor rods (3) are connected to the ring-shaped high-strength steel block (5). Adjust the elongation length and anchoring angle of the anchor rod (3) by the angle adjustment piece (6) so that the anchor rod (3) passes through the pile body (1) and is located in the soil. On the top of the laid pile body (1), lay another layer of pile body (1). The two layers of pile body (1) are connected by reinforcing steel plates (7). Then install anchor rods (3). Repeat the above operation until all pile bodies (1) and anchor rods (3) are installed. After completion, pour concrete into the pile body (1). The installation pit is backfilled and the soil in the installation pit is compacted. At this point, the installation of the device is complete.

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