Sectional type drainage combined pile and consolidation calculation method

Abstract

The invention discloses a sectional type drainage combined pile and a consolidation calculation method, and relates to the technical field of soft soil foundation treatment.The sectional type drainage combined pile comprises a lower pile body, a pile core, a permeable shell and a plurality of pore water pressure monitoring components, the lower portion of the pile core is fixedly arranged in the lower pile body in a sleeved mode, and the permeable shell is fixedly arranged outside the upper portion of the pile core in a sleeved mode; the pile core and the lower pile body are both of a rigid structure and are waterproof, a plurality of pore water pressure monitoring components are sequentially embedded in one side of the water-permeable shell from top to bottom, and a plurality of pore water pressure monitoring components are sequentially embedded in one side of the lower pile body from top to bottom. According to the sectional type drainage combined pile, the foundation bearing capacity and the consolidation rate are improved. Meanwhile, a consolidation calculation method considering radial and vertical seepage of the sectional type drainage composite pile is established, the consolidation calculation method is suitable for consolidation analysis of the sectional type drainage composite pile, and an accurate theoretical basis is provided for engineering design.

Description

Technical Field

[0001] This invention relates to the field of soft soil foundation treatment technology, and in particular to a segmented drainage combined pile and a consolidation calculation method. Background Technology

[0002] Soft soil foundations are characterized by high water content, large void ratio, high compressibility, low shear strength, and poor permeability, which can easily lead to problems such as building settlement, liquefaction, and instability. With population growth and expanding urban construction demands, effectively utilizing soft soil foundations and ensuring they meet bearing capacity and stability requirements has become an important engineering challenge.

[0003] Currently, the main methods for treating soft soil foundations include composite foundation methods and drainage consolidation methods: 1) Composite foundation methods involve setting piles (flexible piles, semi-rigid piles, and rigid piles) in the foundation to change the physical properties of the soil, thereby improving its bearing capacity and resistance to settlement. Flexible piles include lime piles and cement-fly ash-gravel piles; semi-rigid piles include cement-soil compaction piles and jet grouting piles; and rigid piles include reinforced concrete piles and plain concrete piles. Its advantages include improved foundation bearing capacity, reduced costs and construction time, and reduced settlement, but a single pile cannot simultaneously meet drainage and bearing requirements. 2) Drainage consolidation methods involve adding seepage paths (such as sand piles, gravel piles, and plastic drainage boards) and combining this with preloading to accelerate the drainage of pore water, thereby increasing the effective stress and strength of the soil. This method is suitable for treating saturated soft soil layers, but it has limitations such as a limited consolidation rate and poor effectiveness on foundations with high water content.

[0004] While permeable concrete piles combine the advantages of composite foundation methods and drainage consolidation methods, accelerating the dissipation of excess pore water pressure and mitigating foundation liquefaction, their lack of or minimal presence of fine aggregates makes them prone to breakage, and their limited bearing capacity restricts their engineering applications. It is evident that traditional drainage piles (such as permeable concrete piles), while accelerating pore pressure dissipation, are prone to breakage and have insufficient bearing capacity; traditional undrained rigid piles (such as steel pipe piles and plain concrete piles), while possessing high bearing capacity, cannot accelerate foundation consolidation, resulting in poor foundation settlement control and prolonged stabilization time.

[0005] Meanwhile, existing consolidation analytical solutions are mostly for single pile types, failing to consider the segmented structure of composite piles and the radial and vertical seepage coupling effects, resulting in large deviations between the calculation results and actual engineering, and thus failing to accurately guide design. Existing numerical simulations are mostly based on ideal conditions and do not fully incorporate indoor model test parameters, resulting in insufficient accuracy in simulating the stress distribution and pore pressure dissipation laws of composite pile foundations. Summary of the Invention

[0006] To address the above technical problems, this invention provides a segmented drainage combined pile and a consolidation calculation method, which improves the foundation bearing capacity and consolidation rate. It is applicable to the consolidation analysis of segmented drainage combined piles and provides an accurate theoretical basis for engineering design.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a segmented drainage composite pile, comprising a lower pile body, a pile core, a permeable outer shell, and multiple pore water pressure monitoring components. The lower part of the pile core is fixedly sleeved in the lower pile body, and the permeable outer shell is fixedly sleeved on the upper part of the pile core. Both the pile core and the lower pile body are rigid structures and impermeable. Multiple pore water pressure monitoring components are sequentially embedded from top to bottom on one side of the permeable outer shell, and multiple pore water pressure monitoring components are sequentially embedded from top to bottom on one side of the lower pile body.

[0008] Preferably, the central axis of the pile core is collinear with the central axis of the lower pile body, the bottom of the permeable shell is fixedly connected to the top of the lower pile body, and the top of the permeable shell is flush with the top of the pile core.

[0009] Preferably, the pile core and the lower pile body are cylindrical structures, the permeable outer shell is a cylindrical structure, and the outer diameter of the lower pile body and the outer diameter of the permeable outer shell are the same.

[0010] Preferably, the lower pile body is a lower reinforced concrete column, and a plurality of pore water pressure monitoring components are sequentially embedded in one side of the lower reinforced concrete column from top to bottom. The pile core is a central reinforced concrete column, and the lower part of the central reinforced concrete column is fixedly sleeved in the upper part of the lower reinforced concrete column.

[0011] Preferably, the lower pile body includes a lower pipe body and a first reinforced concrete column cast in the lower pipe body. A plurality of pore water pressure monitoring components are sequentially embedded from top to bottom on one side of the lower pipe body. The pile core includes a central pipe body and a second reinforced concrete column cast in the central pipe body. The lower part of the central pipe body is fixedly sleeved on the upper part of the first reinforced concrete column.

[0012] Preferably, the lower pipe body is a steel pipe or a PHC pipe pile, and the central pipe body is a steel pipe or an FRP pipe.

[0013] Preferably, the permeable outer shell is made of permeable concrete, foamed concrete, or porous ceramic.

[0014] Preferably, the system also includes a data acquisition device, and each of the pore water pressure monitoring components is connected to the data acquisition device.

[0015] Preferably, the pore water pressure monitoring component is a fiber optic pore water pressure gauge.

[0016] This invention also provides a method for consolidation calculation of segmented drainage composite piles, comprising the following steps: Step 1: Construct a consolidation calculation model. For the composite foundation, a square pile layout is used. A single segmented drainage composite pile and its influence range pile-soil unit are taken as the research object. Based on the function of the segmented drainage composite pile, it is divided into an upper reinforcement zone and a lower reinforcement zone. The upper reinforcement zone includes the permeable outer shell, the upper part of the pile core corresponding to the position of the permeable outer shell, and the upper inter-pile soil. The thickness of the upper reinforcement zone is... h 1 The coupling effect of radial and vertical seepage needs to be considered; the lower reinforcement zone includes the lower pile body, the lower part of the pile core corresponding to the position of the lower pile body, and the soil between the lower piles, and the thickness of the lower reinforcement zone is... h 2 Only vertical seepage is considered; the total thickness of the composite foundation H = h 1 + h 2 The radius of the pile core is r p The radius of the segmented drainage composite pile is r c The smearing effect radius of the segmented drainage composite pile is r s The radius of influence zone of a single segmented drainage composite pile is r e The pile spacing is s ; Determining the basic assumptions and deriving the consolidation governing equations requires five core assumptions to ensure theoretical solvability and practical engineering relevance: 1) The soil between the piles is fully saturated, the pore water flow obeys Darcy's law, and the soil particles and water are incompressible; 2) The foundation of the composite foundation is a rigid foundation, satisfying the equal strain assumption: at any depth, the vertical deformation of the segmented drainage composite piles and the soil between the piles is consistent. e z = e v , e z For vertical strain, e v (for volumetric strain). 3) The pile core and the permeable outer shell do not slide relative to each other at the interface and deform together; 4) External additional stress under large-area loading s Uniformly distributed along the depth; 5) During the consolidation process, the elastic modulus of the permeable shell and the pile core, the compression modulus of the upper pile-interval soil and the lower pile-interval soil are constant, and the permeability coefficients of the permeable shell, the upper pile-interval soil and the lower pile-interval soil are constant. Step 2: Establish the consolidation control equations, first clarifying the key physical quantities in the equations: the elastic modulus of the permeable shell is... E c The elastic modulus of the pile core is E p The radial permeability coefficient of the permeable shell is k hw The vertical permeability coefficient of the permeable shell is k vw The radial permeability coefficient of the soil between the upper piles is k h The vertical permeability coefficient of the soil between the upper piles is k v1 The vertical permeability coefficient of the soil between the lower piles is k v2 The compression modulus of the soil between the upper piles is E e1 The compression modulus of the soil between the lower piles is E e2 The density of water is r w The ultrastatic pore water pressure of the permeable shell is u c The excess pore water pressure in the soil between the upper piles is u e1 The excess pore water pressure in the soil between the lower piles is u e2 ; Establish the consolidation equation for the corresponding region of the soil between the upper piles, including the following derivation steps: Step A1, External Additional Stress The vertical force is borne jointly by the pile core, the permeable outer shell, and the upper soil between the piles, and the force balance satisfies the force balance equation: ; in, The average total vertical stress of the pile core. The average total vertical stress of the permeable outer shell, The average total vertical stress of the soil between the upper piles; Step A2: Since the vertical deformation of the segmented drainage composite pile and the soil between the piles is consistent at any depth, the stress and strain satisfy Hooke's law, and the deformation compatibility equation is derived. ; in, The average excess pore water pressure of the permeable shell, The average excess pore water pressure in the soil between the upper piles; Step A3, Average excess pore water pressure of the permeable shell Average excess pore water pressure in the soil between the upper piles The upper composite compression modulus is , ; Step A4: Based on Darcy's law and the law of conservation of volume, the consolidation governing equations between the upper pile-fill soil and the permeable outer shell are derived: The consolidation control equation for the soil between the upper piles is: ,in, The radial permeability coefficient of the soil between piles. Considering the smearing effect, , t is the consolidation time; The consolidation governing equation for the permeable shell is: ,in, k hw The radial permeability coefficient of the permeable shell is... k vw The vertical permeability coefficient of the permeable outer shell; Establish the consolidation equation for the corresponding region of soil between the lower piles, including the following derivation steps: Step B1, the force balance equation is: The deformation compatibility equation is: The lower pile body and the portion of the pile core corresponding to the position of the lower pile body constitute the lower rigid pile segment. This represents the total stress in the lower rigid pile segment; The average total vertical stress in the soil between the lower piles is denoted as . The average excess pore water pressure in the soil between the lower piles; Step B2: Based on Darcy's law and the law of conservation of volume, the consolidation governing equations for the soil between the lower piles are derived: ,in, The vertical consolidation coefficient is the lower part. , ; Step 3: Solving the consolidation governing equations requires clearly defining the spatial boundaries and initial time conditions, which are set as follows according to the actual engineering situation: 1) Determine the spatial boundary conditions, at the top surface of the vertical boundary. z =0, complete drainage, pore pressure is 0. u e1 =0, u c =0; at the bottom of the vertical boundary No vertical seepage. ; at the interface between upper and lower layers Continuous pore pressure Continuous seepage The radius of influence of the radial boundary at the boundary. ; at the boundary of the pile core At the pile-soil interface 2) Determine the time boundary conditions, under staged loading, the first... j At the initial moment of application of the first load, , , For the first j Final value of level load, This represents the final value of the previous load level. Step 4: Solve the consolidation control equations using the separation of variables method and Fourier series expansion, divided into two scenarios: single-stage instantaneous loading and multi-stage instantaneous loading. 1) Solve for single-stage instantaneous loading, σ(t)=σ0, t≥0; First, make formal assumptions about the solution, and then press the upper hole. Set in the form of a space function × a time function: ; ; in, These are the Fourier coefficients. For eigenvalues; The upper pore pressure space characteristic function, ); The lower pore pressure space characteristic function, ); These are spatial eigenvalues ​​derived from boundary conditions; Then determine the Fourier coefficients : Using the initial condition t=0 Combining the orthogonality of the characteristic functions, we can solve for: ; in, ; , ; ; 2) Solving for multi-stage instantaneous loading: In actual engineering, loading is applied in stages. The pore pressure solution for the j-th stage load is the superposition of the load increments at each stage. ; ; Step 5: Perform consolidation degree calculation, define two indicators: consolidation degree based on settlement and consolidation degree based on pore pressure, and evaluate the consolidation effect from the perspectives of deformation completion degree and pore pressure dissipation degree, respectively. 1) According to the definition of settlement, the degree of consolidation is , representing the settlement at a certain moment With final settlement The ratio: ; ; Calculated The deviation from the finite element solution is ≤3.5%, which verifies that the above calculation method is reasonable; 2) The degree of consolidation as defined by pore pressure is , is the ratio of the total remaining excess porosity at a certain moment to the total initial excess porosity. .

[0017] The present invention achieves the following technical effects compared to the prior art: The segmented drainage combined pile of this invention includes a lower pile body, a pile core, a permeable outer shell, and multiple pore water pressure monitoring components. The lower part of the pile core is fixedly fitted inside the lower pile body, and the permeable outer shell is fixedly fitted outside the upper part of the pile core. Both the pile core and the lower pile body are rigid structures and impermeable. Multiple pore water pressure monitoring components are sequentially embedded from top to bottom on one side of the permeable outer shell, and multiple pore water pressure monitoring components are sequentially embedded from top to bottom on one side of the lower pile body. In this invention, the lower pile body, pile core, and permeable outer shell work together to bear the load, which improves the bearing capacity of the segmented drainage combined pile compared to pure permeable concrete piles and solves the problem of easy pile breakage. The upper permeable outer shell forms radial drainage channels through a porous structure, allowing pore water to permeate vertically along the pile body and simultaneously discharge radially through the interface between the pile body and the soil, accelerating the dissipation of excess pore water pressure. This dual-path drainage significantly shortens the consolidation time. Therefore, the segmented drainage combined pile of this invention improves the bearing capacity and consolidation rate of the foundation. Meanwhile, this invention establishes a consolidation calculation method that considers radial and vertical seepage in segmented drainage composite piles, which is applicable to the consolidation analysis of segmented drainage composite piles and provides an accurate theoretical basis for engineering design. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only 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 A schematic diagram of the cable leading out from the top of the pore water pressure monitoring component of the segmented drainage combined pile provided by the present invention; Figure 2 A cross-sectional view of the cable extending from the top of the pore water pressure monitoring component of the segmented drainage combined pile provided by the present invention. Figure 3 A schematic diagram of the cable leading out from the side wall of the pore water pressure monitoring component of the segmented drainage combined pile provided by the present invention; Figure 4 This is a schematic diagram of a composite foundation using the segmented drainage combined piles provided by the present invention.

[0020] Explanation of reference numerals in the attached diagram: 1. Lower pile body; 2. Pile core; 3. Permeable outer shell; 4. Pore water pressure monitoring component; 5. Data acquisition equipment; 6. Protective pipe; 7. Upper soil between piles; 8. Lower soil between piles; 9. Smearing area. 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 embodiments of the present invention, and not all embodiments. 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] The purpose of this invention is to provide a segmented drainage combined pile and a consolidation calculation method, which improves the foundation bearing capacity and consolidation rate, is applicable to the consolidation analysis of segmented drainage combined piles, and provides an accurate theoretical basis for engineering design.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1-Figure 4 As shown, this embodiment provides a segmented drainage composite pile, including a lower pile body 1, a pile core 2, a permeable outer shell 3, and multiple pore water pressure monitoring components 4. The lower part of the pile core 2 is fixedly sleeved in the lower pile body 1, and the permeable outer shell 3 is fixedly sleeved on the upper part of the pile core 2. Both the pile core 2 and the lower pile body 1 are rigid structures and impermeable. Multiple pore water pressure monitoring components 4 are sequentially embedded from top to bottom on one side of the permeable outer shell 3, and multiple pore water pressure monitoring components 4 are sequentially embedded from top to bottom on one side of the lower pile body 1.

[0025] In this embodiment, the lower pile body 1, pile core 2, and permeable shell 3 work together to increase the bearing capacity of the segmented drainage composite pile compared to pure permeable concrete piles, thus solving the problem of easily broken piles. Specifically, the pile core 2 shares most of the axial force through the bonding interface, reducing the stress level of the permeable shell 3 and making its working stress lower than the splitting strength (2.5MPa). The upper permeable shell 3 forms radial drainage channels through a porous structure, allowing pore water to seep vertically along the pile body and simultaneously discharge radially through the pile-soil interface, accelerating the dissipation of excess pore water pressure. This dual-path drainage significantly shortens the consolidation time, as the radial seepage path length is only 1 / 3 of that of a traditional sand well, and the vertical permeability coefficient is increased by three orders of magnitude. According to Darcy's law, the seepage velocity is proportional to the hydraulic gradient and the permeability coefficient. The equivalent permeability coefficient of the segmented drainage composite pile is 1.2 × 10⁻⁶ for the natural foundation. 4 The segmented drainage combined pile in this embodiment improves the foundation bearing capacity and consolidation rate. Therefore, the segmented drainage combined pile in this embodiment can simultaneously meet the requirements of rapid drainage consolidation and high bearing capacity.

[0026] Specifically, the test showed that the pore pressure dissipation rate under the ninth level load was 20% faster than that of traditional undrained rigid piles. During the staged loading process, the drainage channel improved the compaction of the foundation soil and reduced the later settlement. Under the 50kPa load, the final settlement was reduced by 18.5% compared with traditional undrained rigid piles.

[0027] The pile core 2 bears the main load, and the axial force it bears is 2.53 to 3.47 times that of the permeable shell 3, coordinating pile deformation and preventing the permeable shell 3 from breaking. The porous structure of the permeable shell 3 increases the frictional force at the pile-soil interface, improves the pile-soil stress ratio, and enhances the overall bearing capacity of the foundation. Specifically, the pile-soil stress ratio of the segmented drainage combined pile is 13.68, while that of the traditional undrained rigid pile is 11.24. The lower rigid section provides end bearing capacity, while the upper section transfers the load through side friction; both work together to improve the overall bearing capacity contribution.

[0028] The central axis of the pile core 2 is collinear with the central axis of the lower pile body 1. The bottom of the permeable shell 3 is fixedly connected to the top of the lower pile body 1, and the top of the permeable shell 3 is flush with the top of the pile core 2.

[0029] The pile core 2 and the lower pile body 1 are cylindrical structures, and the permeable outer shell 3 is a cylindrical structure. The outer diameter of the pile core 2 is smaller than the outer diameter of the lower pile body 1, and the outer diameter of the lower pile body 1 is the same as the outer diameter of the permeable outer shell 3.

[0030] Specifically, the lower part of the pile core 2 is fixedly sleeved in the upper part of the lower pile body 1. In this embodiment, the height at which the pile core 2 is fixedly sleeved in the lower pile body 1 is 2 to 3 times the outer diameter of the pile core 2.

[0031] In this specific embodiment, the lower pile body 1 is a lower reinforced concrete column, and multiple pore water pressure monitoring components 4 are embedded in one side of the lower reinforced concrete column from top to bottom. The pile core 2 is a central reinforced concrete column, and the lower part of the central reinforced concrete column is fixedly sleeved on the upper part of the lower reinforced concrete column.

[0032] Specifically, both the lower reinforced concrete column and the central reinforced concrete column are cast in one pour. The upper part of the lower reinforced concrete column has a first groove, the size of which is larger than that of the central reinforced concrete column. The lower part of the central reinforced concrete column is located in the first groove, so that the central axis of the central reinforced concrete column and the lower reinforced concrete column are collinear. Concrete is poured into the first groove to fix the central reinforced concrete column and the lower reinforced concrete column together.

[0033] To install the pore water pressure monitoring component 4, multiple first mounting grooves are pre-reserved from top to bottom on one side during the pouring and manufacturing of the permeable outer shell 3. This ensures that the surface of the pore water pressure monitoring component 4 is basically flush with the surface of the permeable outer shell 3 after being fixed in the first mounting groove, preventing it from protruding and being damaged during construction. During the pouring and manufacturing of the lower reinforced concrete column, multiple second mounting grooves are sequentially pre-reserved from top to bottom on one side. This ensures that the surface of the pore water pressure monitoring component 4 is basically flush with the surface of the lower reinforced concrete column after being fixed in the second mounting groove, preventing it from protruding and being damaged during construction.

[0034] Specifically, after placing the pore water pressure monitoring component 4 into the first or second mounting groove, an epoxy resin adhesive is used to fill the gap between the pore water pressure monitoring component 4 and the groove wall to achieve fixation. The epoxy resin can tightly bond the metal or engineering plastic shell of the pore water pressure monitoring component 4 to the concrete, while ensuring that water pressure can be effectively transmitted to the sensing surface of the pore water pressure monitoring component 4 through the adhesive layer. It should be noted that the adhesive should not cover the pressure sensing membrane of the pore water pressure monitoring component 4.

[0035] The cable leading out from pore water pressure monitoring component 4 should be arranged close to the pile reinforcement cage to avoid being suspended or having an excessive span, so as to prevent it from being displaced or broken by impact during concrete pouring. If the pile is long (e.g., more than 10 meters), the cable needs to be fixed in sections (fixed every 50~100cm) to ensure that it is closely attached to the reinforcement, with a smooth path and no sharp bends or entanglements.

[0036] Specifically, the cables are secured by binding with stainless steel cable ties that prevent corrosion or high-strength nylon cable ties that are resistant to aging. The binding force should be moderate, secure but not so tight as to crush the cable sheath, especially for fiber optic cables, which should be protected from excessive compression. Conduit protection is then implemented. Protective conduits (6) are installed at locations prone to cable abrasion (such as rebar intersections and sections extending from the top of piles). These conduits are made of rigid PVC or corrugated metal and have a diameter 2-3 mm larger than the cable diameter. Both ends of the conduit are sealed with sealant to prevent concrete slurry from seeping into the conduit and damaging the cable.

[0037] The cable must be led from the top of the pile to the monitoring terminal. The lead-out point should avoid the stress zone at the top of the pile, such as areas with dense reinforcement at the pile head. A hole with a diameter of 10-20mm should be pre-drilled on the top surface or the upper side of the segmented drainage combined pile. After the cable passes through the hole, the hole should be sealed with waterproof sealant (such as silicone sealant) to prevent rainwater or groundwater backflow. Sufficient redundant length should be reserved at the pile top lead-out section, typically 1-3 meters, which can be adjusted according to site conditions to avoid cable breakage due to subsequent equipment relocation or pile settlement. The redundant portion can be coiled and secured with cable ties to the top surface, the upper side of the segmented drainage combined pile, or a nearby support to prevent dragging and wear.

[0038] For waterproofing and sealing, the connectors of the pore water pressure monitoring component 4 and the cable are usually sealed at the factory. On-site inspection is required to check for integrity. If there is any damage, double sealing should be performed using special waterproof tape (such as butyl tape) and heat shrink tubing. The heat shrink tubing should be fully adhered after heating, without any air bubbles.

[0039] In another specific embodiment, the lower pile body 1 includes a lower pipe body and a first reinforced concrete column cast in the lower pipe body. Multiple pore water pressure monitoring components 4 are sequentially embedded on one side of the lower pipe body from top to bottom. The pile core 2 includes a central pipe body and a second reinforced concrete column cast in the central pipe body. The lower part of the central pipe body is fixedly sleeved on the upper part of the first reinforced concrete column.

[0040] Specifically, the lower pipe body is a steel pipe or PHC pipe pile, and the central pipe body is a steel pipe or FRP pipe.

[0041] To install the pore water pressure monitoring component 4, multiple third mounting slots are pre-drilled from top to bottom on one side of the lower pipe body. This ensures that the surface of the pore water pressure monitoring component 4 is basically flush with the lower pipe body after being fixed in the third mounting slot, preventing it from protruding and being damaged during construction. Specifically, after placing the pore water pressure monitoring component 4 into the third mounting slot, epoxy resin adhesive is used to fill the gap between the pore water pressure monitoring component 4 and the slot wall to achieve fixation.

[0042] Specifically, the permeable outer shell 3 is made of permeable concrete, foamed concrete, or porous ceramic. In this embodiment, the permeable outer shell 3 is made of permeable concrete with coarse aggregate of 3-5mm particle size, a porosity of 28.6%, and a permeability coefficient of 0.997×10⁻⁶. -3 m / s. Permeable concrete is designed using the volumetric method for mix proportioning; specifically, cement 245 kg / m³. 3 76 kg / m³ of water 3 Coarse aggregate 1530kg / m 3 This forms a continuous drainage channel, accelerating the dissipation of pore water.

[0043] This embodiment also includes a data acquisition device 5, and each pore water pressure monitoring component 4 is connected to the data acquisition device 5.

[0044] Existing technologies for monitoring pore water pressure around piles and soil are mostly vibrating wire pore water pressure gauges or resistance pore water pressure gauges, which are susceptible to electromagnetic interference (such as construction machinery and surrounding power grids), resulting in poor data stability. Distributed monitoring is difficult (requiring multiple lines, which are prone to breakage due to soil deformation); long-term durability is insufficient (in soft soil corrosion environments, the service life is usually <5 years); and accuracy is limited (the resolution is mostly 0.1 kPa, making it difficult to capture subtle pressure changes in soft foundation consolidation). In other words, they have defects such as weak anti-interference ability, limited distributed monitoring, insufficient durability, and limited monitoring accuracy.

[0045] Therefore, in this embodiment, the pore water pressure monitoring component 4 is a fiber optic pore water pressure gauge. Fiber optic pore water pressure gauges have the following advantages: based on fiber Bragg grating (FBG) or distributed fiber optic sensing (DOFS) technology, they possess characteristics such as anti-electromagnetic interference, corrosion resistance, distributed continuous monitoring, high precision (pressure resolution up to 0.01 kPa), and long lifespan (over 15 years). They can accurately and continuously capture the dynamic changes in pore water pressure around and inside the pile, which is highly compatible with the requirements of efficient consolidation and long-term service of segmented drainage combined piles.

[0046] As can be seen, the fiber optic pore water pressure gauge measures pressure by changing the optical signal due to the deformation of the fiber optic grating under pressure. It is resistant to electromagnetic interference, corrosion, and has high accuracy. It is suitable for extreme environments (such as deep sea and high temperature) and can monitor for 10 to 20 years, and up to 15 years or more in special environments.

[0047] This embodiment also provides a consolidation calculation method based on segmented drainage composite piles, including the following steps: Step 1: Construct a consolidation calculation model. For composite foundations, square piles are used. A single segmented drainage combined pile and the pile-soil unit within its influence range are taken as the research object and are equivalent to an axisymmetric model for mechanical and consolidation characteristic analysis. The segmented drainage combined pile is divided into an upper reinforcement zone and a lower reinforcement zone according to its function.

[0048] The upper reinforcement zone includes the permeable outer shell 3, the upper part of the pile core 2 corresponding to the position of the permeable outer shell 3, and the upper inter-pile soil 7. The thickness of the upper reinforcement zone is... h 1 The coupling effect of radial and vertical seepage needs to be considered. Vertical seepage is controlled by the vertical permeability of the soil, while radial seepage is controlled by the horizontal permeability of the soil. Both types of seepage affect the rate of change of excess pore water pressure over time. Among them, the vertical permeability coefficient is higher than that of natural soil due to the drainage effect of the pile, while the radial permeability coefficient reflects the ability of pore water to converge towards the pile.

[0049] The lower reinforcement zone includes the lower pile body 1, the lower part of the pile core 2 corresponding to the position of the lower pile body 1, and the lower pile inter-soil 8. The thickness of the lower reinforcement zone is... h 2 Considering only vertical seepage, the permeability coefficient is adopted from the vertical permeability performance parameters of natural soil. Since there are no radial drainage channels in this area, pore water can only be discharged vertically upwards.

[0050] Total thickness of composite foundation H = h 1 + h 2 The radius of pile core 2 is r p The radius of the segmented drainage composite pile is r c The radius of the smearing effect of the segmented drainage composite pile is r s Radius of the smearing effect r s The key geometric parameter defining the boundary of the smeared area 9 is the radius of the influence zone of a single segmented drainage composite pile. r e The pile spacing is s , .

[0051] In this specific embodiment, the height of the segmented drainage composite pile is h 1 + h 2 The height of the segmented drainage combined pile is 1m. This is the model test size of the segmented drainage combined pile. The actual project will be scaled down proportionally. h 1 and h 2 All are 0.5m in diameter; the radius of the segmented drainage composite piles is... r c The radius of pile core 2 is 0.08m. r p The pile spacing is 0.04m.s It is 0.32m. .

[0052] Determining the basic assumptions and deriving the consolidation governing equations requires five core assumptions to ensure theoretical solvability and practical engineering relevance: 1) The soil between the piles is fully saturated, the pore water flow obeys Darcy's law, and the soil particles and water are incompressible; 2) The foundation of the composite foundation is a rigid foundation, satisfying the equal strain assumption: at any depth, the vertical deformation of the segmented drainage composite piles and the soil between the piles is consistent. e z = e v , e z For vertical strain, e v (for volumetric strain). 3) There is no relative sliding at the interface between the pile core 2 and the permeable outer shell 3; they deform together. 4) External additional stress under large-area loading s Uniformly distributed along the depth; 5) During the consolidation process, the elastic modulus of the permeable shell 3 and the pile core 2, the compression modulus of the upper pile inter-soil 7 and the lower pile inter-soil 8 are constant, and the permeability coefficients of the permeable shell 3, the upper pile inter-soil 7 and the lower pile inter-soil 8 are constant. The deformation of the pile material is linear elastic, and the compressibility of the pile itself is not considered; the load is applied in stages, and the duration of each load stage is determined according to the construction progress.

[0053] Step 2: Establish the consolidation control equations, first clarifying the key physical quantities in the equations: the elastic modulus of the permeable outer shell 3 is... E c The elastic modulus of pile core 2 is E p The radial permeability coefficient of the permeable outer shell 3 is k hw The vertical permeability coefficient of the permeable outer shell 3 is k vw The radial permeability coefficient of the soil between the upper piles is 7. k h The vertical permeability coefficient of the soil between the upper piles is 7. k v1 The vertical permeability coefficient of the soil between the lower piles is 8. k v2 The compression modulus of the soil between the upper piles is 7. E e1 The compression modulus of the soil between the lower piles is E e2 The density of water is r wThe ultrastatic pore water pressure of the permeable shell 3 is u c The excess pore water pressure in the soil between the upper piles is u e1 The excess pore water pressure in the soil between the lower piles is u e2 .

[0054] During the consolidation process, the elastic modulus of the permeable shell 3 and the pile core 2, the radial and vertical permeability coefficients of the permeable shell 3, the compression modulus of the upper pile-interval soil 7 and the lower pile-interval soil 8, the radial and vertical permeability coefficients of the upper pile-interval soil 7, and the vertical permeability coefficient of the lower pile-interval soil 8 are constant, as measured by experiments.

[0055] In this specific embodiment, the elastic modulus of the permeable outer shell 3 is... E c =20.7GPa, elastic modulus of pile core 2 E p =203.8 GPa, radial permeability coefficient of permeable shell 3 k hw =0.997×10 -3 m / s, vertical permeability coefficient of the permeable outer shell 3 k vw =0.997×10 -3 m / s, radial permeability coefficient of soil 7 between upper piles k h =3.2×10 -6 m / s, vertical permeability coefficient of soil 7 between upper piles k v1 =1.6×10 -6 m / s, vertical permeability coefficient of soil between lower piles 8 k v2 =3.2×10 -6 m / s, the compression modulus of the soil between the upper piles 7 E e1 =600kPa, the compression modulus of the soil between the lower piles 8 E e2 =600kPa, the specific gravity of water r w =9.8kN / m 3 .

[0056] Establish the consolidation equation for the soil zone corresponding to the upper piles (7), including the following derivation steps: Step A1, External Additional Stress The vertical force is borne jointly by the pile core 2, the permeable outer shell 3, and the upper soil between the piles 7, and the force balance satisfies the force balance equation: ; in, The average total vertical stress of pile core 2 is... The average total vertical stress of the permeable outer shell 3, The average total vertical stress of the soil between the upper piles is 7.

[0057] The equation means that at any depth, the stress of the pile core 2, the permeable outer shell 3, and the upper soil between the piles 7 multiplied by their respective areas is equal to the total additional stress at that depth multiplied by the area of ​​the affected zone.

[0058] Step A2: Since the vertical deformation of the segmented drainage composite pile and the soil between the piles is consistent at any depth, the stress and strain satisfy Hooke's Law, and the deformation compatibility equation is derived. ; in, The average excess pore water pressure of the permeable shell 3, The average excess pore water pressure in the soil between the upper piles is 7.

[0059] Step A3, Average excess pore water pressure of the permeable shell 3 The average excess pore water pressure in the soil between the upper piles (7) The upper composite compression modulus is , The formula means that the overall stiffness of the superstructure is determined by the sum of the stiffnesses of its constituent parts.

[0060] Step A4: Based on Darcy's law and the law of conservation of volume, the pore water discharge = soil compression, thus deriving the consolidation control equation between the upper pile-interface soil 7 and the permeable outer shell 3: The consolidation control equation for the soil between the upper piles is: ,in, The radial permeability coefficient of the soil between piles. Considering the smearing effect, , t is the consolidation time, which is the time elapsed from the application of the load to the calculation time. The left side of the formula is the pore water discharge rate of radial seepage + vertical seepage; the right side of the formula is the soil volumetric strain rate (compression rate).

[0061] The consolidation governing equation for the permeable shell 3 is: ,in, k hw The radial permeability coefficient of the permeable outer shell 3 is... k vw The vertical permeability coefficient of the permeable shell 3 is given. Because permeable concrete is a porous structure, the radial and vertical permeability coefficients of the permeable shell 3 are much greater than the permeability coefficient of the soil between the piles.

[0062] Establish the consolidation equation for the soil zone corresponding to the lower piles (8), including the following derivation steps: Step B1, the force balance equation is: The deformation compatibility equation is: Among them, the lower part of the pile body 1 and the lower part of the pile core 2, corresponding to the position of the lower pile body 1, constitute the lower rigid pile segment. This represents the total stress in the lower rigid pile segment; The vertical average total stress is denoted as 8, which represents the soil between the lower piles. The average excess pore water pressure of the soil between the lower piles 8 is given; since there is no radial seepage, the soil between the lower piles 8 is consolidated only through vertical drainage.

[0063] Step B2: Based on Darcy's law and the law of conservation of volume, the consolidation governing equations for the soil between the lower piles are derived: ,in, The vertical consolidation coefficient is the lower part. , ;Specifically, , The vertical permeability coefficient of soil 8 between the lower piles k v2 =3.2×10 -6 m / s.

[0064] Step 3: Solving the consolidation governing equations requires clearly defining the spatial boundaries and initial time conditions, which are set as follows according to the actual engineering situation: 1) Determine the spatial boundary conditions, at the top surface of the vertical boundary. z =0, complete drainage, pore pressure is 0. u e1 =0, u c =0; at the bottom of the vertical boundary No vertical seepage. ; at the interface between upper and lower layers Continuous pore pressure Continuous seepage , specifically, The radius of influence of the radial boundary at the boundary. ; Boundary of pile core 2 At the pile-soil interface 2) Determine the time boundary conditions, under staged loading, the first... j At the initial moment of application of the first load, , , For the first j Final value of level load, This represents the final value of the previous load level; here it means that at the initial loading stage, all additional stress is borne by the pore water, the effective stress is 0, therefore the excess pore pressure is equal to the load increment.

[0065] Step 4: Solve the consolidation control equations using the separation of variables method and Fourier series expansion, divided into two scenarios: single-stage instantaneous loading and multi-stage instantaneous loading; the core is to decompose the two-dimensional equation (rzt) into a one-dimensional function product form.

[0066] 1) Solve for single-stage instantaneous loading, σ(t)=σ0, t≥0; First, make formal assumptions about the solution, and then press the upper hole. Set in the form of a space function × a time function: ; ; in, These are the Fourier coefficients, determined by the initial conditions; This is an eigenvalue, related to the consolidation rate. The larger the size, the faster the solidification. The upper pore pressure space characteristic function, ); The lower pore pressure space characteristic function, ); These are spatial eigenvalues ​​derived from the boundary conditions, satisfying orthogonality, and used for coefficient calculation. Then determine the Fourier coefficients : Using the initial condition t=0 Combining the orthogonality of characteristic functions (the product of the integrals of functions corresponding to different eigenvalues ​​is 0), we obtain: ; Among them, the upper weight coefficient ; Upper characteristic function integral Integral of the lower characteristic function ; The square integral of the characteristic function is used for orthogonality normalization. ; 2) Solving for multi-stage instantaneous loading; in actual engineering, loading is applied in stages, with the j-th stage load ( The pore pressure solution is the superposition of load increments at each stage: ; ; The core logic is as follows: using the principle of linear superposition, the multi-level load is regarded as the sequential action of multiple single-level load increments. The pore pressure solution of each increment is calculated according to the single-level loading, and finally the total pore pressure is obtained by superposition.

[0067] Step 5: Perform consolidation degree calculation, define two indicators: consolidation degree based on settlement and consolidation degree based on pore pressure, and evaluate the consolidation effect from the perspectives of deformation completion degree and pore pressure dissipation degree, respectively. 1) According to the definition of settlement, the degree of consolidation is , representing the settlement at a certain moment With final settlement The ratio: ; This contributes weight to the compression of the upper and lower parts; The calculation results were compared and verified with the results of indoor model tests and finite element simulations to ensure that the calculation error was controlled within the allowable range of the project (not exceeding 5%).

[0068] In one example, under a single-stage loading of 30 kPa, the calculated results are... The deviation from the finite element solution is ≤3.5%, which verifies that the above calculation method is reasonable.

[0069] 2) The degree of consolidation as defined by pore pressure is , is the ratio of the total remaining excess porosity at a certain moment to the total initial excess porosity. .

[0070] The physical meaning is: reflecting the overall degree of pore water pressure dissipation, and it is often used in engineering to determine the timing of loading (such as U). p Apply the next load level when ≥80%.

[0071] It should be noted that the pile layout can be adjusted: using a triangular pile layout instead of a square pile layout can reduce the pile spacing under the same replacement rate, further optimizing the consolidation effect. The calculation scheme can be simplified: for projects with pile lengths ≤10m, the depth variation of radial seepage can be ignored, and the average permeability coefficient can be used for calculation, with the consolidation degree error controlled within 8%, meeting the engineering design accuracy requirements.

[0072] This embodiment establishes a consolidation calculation method considering radial and vertical seepage in segmented drainage composite piles. This method is applicable to the consolidation analysis of segmented drainage composite piles under graded loading, providing an accurate theoretical basis for engineering design and enabling accurate prediction of composite foundation deformation patterns. Indoor model tests and finite element numerical simulations verify the rationality of the composite pile structure and calculation method, promoting its engineering application in soft soil foundation treatment. The upgrade from static design to dynamic sensing makes the working mechanism of segmented drainage composite piles more transparent, providing a foundation for subsequent expansion technologies such as intelligent loading control based on monitoring data and self-cleaning early warning of drainage channels, further broadening the application scope.

[0073] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A segmented drainage composite pile, characterized in that, The device includes a lower pile body, a pile core, a permeable outer shell, and multiple pore water pressure monitoring components. The lower part of the pile core is fixedly fitted inside the lower pile body, and the permeable outer shell is fixedly fitted outside the upper part of the pile core. Both the pile core and the lower pile body are rigid structures and are impermeable. Multiple pore water pressure monitoring components are sequentially embedded from top to bottom on one side of the permeable outer shell, and multiple pore water pressure monitoring components are sequentially embedded from top to bottom on one side of the lower pile body.

2. The segmented drainage composite pile according to claim 1, characterized in that, The central axis of the pile core is collinear with the central axis of the lower pile body, the bottom of the permeable shell is fixedly connected to the top of the lower pile body, and the top of the permeable shell is flush with the top of the pile core.

3. The segmented drainage composite pile according to claim 2, characterized in that, The pile core and the lower pile body are cylindrical structures, and the permeable outer shell is a cylindrical structure. The outer diameter of the lower pile body and the outer diameter of the permeable outer shell are the same.

4. The segmented drainage combined pile according to claim 3, characterized in that, The lower pile body is a lower reinforced concrete column. Multiple pore water pressure monitoring components are embedded in one side of the lower reinforced concrete column from top to bottom. The pile core is a central reinforced concrete column. The lower part of the central reinforced concrete column is fixedly sleeved on the upper part of the lower reinforced concrete column.

5. The segmented drainage composite pile according to claim 3, characterized in that, The lower pile body includes a lower pipe body and a first reinforced concrete column cast in the lower pipe body. A plurality of pore water pressure monitoring components are embedded in one side of the lower pipe body from top to bottom. The pile core includes a central pipe body and a second reinforced concrete column cast in the central pipe body. The lower part of the central pipe body is fixedly sleeved on the upper part of the first reinforced concrete column.

6. The segmented drainage composite pile according to claim 5, characterized in that, The lower pipe body is a steel pipe or a PHC pipe pile, and the central pipe body is a steel pipe or an FRP pipe.

7. The segmented drainage composite pile according to claim 3, characterized in that, The permeable outer shell is made of permeable concrete, foamed concrete or porous ceramic.

8. The segmented drainage composite pile according to claim 3, characterized in that, It also includes a data acquisition device, and each of the pore water pressure monitoring components is connected to the data acquisition device.

9. The segmented drainage composite pile according to claim 3, characterized in that, The pore water pressure monitoring component is a fiber optic pore water pressure gauge.

10. A consolidation calculation method based on segmented drainage composite piles as described in any one of claims 3-9, characterized in that, Includes the following steps: Step 1: Construct a consolidation calculation model. For the composite foundation, a square pile layout is used. A single segmented drainage composite pile and its influence range pile-soil unit are taken as the research object. Based on the function of the segmented drainage composite pile, it is divided into an upper reinforcement zone and a lower reinforcement zone. The upper reinforcement zone includes the permeable outer shell, the upper part of the pile core corresponding to the position of the permeable outer shell, and the upper inter-pile soil. The thickness of the upper reinforcement zone is... h 1 The coupling effect of radial and vertical seepage needs to be considered; the lower reinforcement zone includes the lower pile body, the lower part of the pile core corresponding to the position of the lower pile body, and the soil between the lower piles, and the thickness of the lower reinforcement zone is... h 2 Only vertical seepage is considered; the total thickness of the composite foundation H = h 1 + h 2 The radius of the pile core is r p The radius of the segmented drainage composite pile is r c The smearing effect radius of the segmented drainage composite pile is r s The radius of influence zone of a single segmented drainage composite pile is r e The pile spacing is s ; Determining the basic assumptions and deriving the consolidation governing equations requires five core assumptions to ensure theoretical solvability and practical engineering relevance: 1) The soil between the piles is fully saturated, the pore water flow obeys Darcy's law, and the soil particles and water are incompressible; 2) The foundation of the composite foundation is a rigid foundation, satisfying the equal strain assumption: at any depth, the vertical deformation of the segmented drainage composite piles and the soil between the piles is consistent. ε z = ε v , ε z For vertical strain, ε v (for volumetric strain). 3) The pile core and the permeable outer shell do not slide relative to each other at the interface and deform together; 4) External additional stress under large-area loading σ Uniformly distributed along the depth; 5) During the consolidation process, the elastic modulus of the permeable shell and the pile core, the compression modulus of the upper pile-interval soil and the lower pile-interval soil are constant, and the permeability coefficients of the permeable shell, the upper pile-interval soil and the lower pile-interval soil are constant. Step 2: Establish the consolidation control equations, first clarifying the key physical quantities in the equations: the elastic modulus of the permeable shell is... E c The elastic modulus of the pile core is E p The radial permeability coefficient of the permeable shell is k hw The vertical permeability coefficient of the permeable shell is k vw The radial permeability coefficient of the soil between the upper piles is k h The vertical permeability coefficient of the soil between the upper piles is k v1 The vertical permeability coefficient of the soil between the lower piles is k v2 The compression modulus of the soil between the upper piles is E e1 The compression modulus of the soil between the lower piles is E e2 The density of water is r w The ultrastatic pore water pressure of the permeable shell is u c The excess pore water pressure in the soil between the upper piles is u e1 The excess pore water pressure in the soil between the lower piles is u e2 ; Establish the consolidation equation for the corresponding region of the soil between the upper piles, including the following derivation steps: Step A1, External Additional Stress The vertical force is borne jointly by the pile core, the permeable outer shell, and the upper soil between the piles, and the force balance satisfies the force balance equation: ； in, The average total vertical stress of the pile core. The average total vertical stress of the permeable outer shell, The average total vertical stress of the soil between the upper piles; Step A2: Since the vertical deformation of the segmented drainage composite pile and the soil between the piles is consistent at any depth, the stress and strain satisfy Hooke's law, and the deformation compatibility equation is derived. ； in, The average excess pore water pressure of the permeable shell, The average excess pore water pressure in the soil between the upper piles; Step A3, Average excess pore water pressure of the permeable shell Average excess pore water pressure in the soil between the upper piles The upper composite compression modulus is , ; Step A4: Based on Darcy's law and the law of conservation of volume, the consolidation governing equations between the upper pile-fill soil and the permeable outer shell are derived: The consolidation governing equation for the soil between the upper piles is: ,in, The radial permeability coefficient of the soil between piles. Considering the smearing effect, , t is the consolidation time; The consolidation governing equation for the permeable shell is: ,in, k hw The radial permeability coefficient of the permeable shell is... k vw The vertical permeability coefficient of the permeable outer shell; Establish the consolidation equation for the corresponding region of soil between the lower piles, including the following derivation steps: Step B1, the force balance equation is: The deformation compatibility equation is: The lower pile body and the portion of the pile core corresponding to the position of the lower pile body constitute the lower rigid pile segment. This represents the total stress in the lower rigid pile segment; The vertical average total stress is denoted as . The average excess pore water pressure in the soil between the lower piles; Step B2: Based on Darcy's law and the law of conservation of volume, the consolidation governing equations for the soil between the lower piles are derived: ,in, The vertical consolidation coefficient is the lower part. , ; Step 3: Solving the consolidation governing equations requires clearly defining the spatial boundaries and initial time conditions, which are set as follows according to the actual engineering situation: 1) Determine the spatial boundary conditions, at the top surface of the vertical boundary. z =0, complete drainage, pore pressure is 0. u e1 =0, u c =0; at the bottom of the vertical boundary No vertical seepage. ; at the interface between upper and lower layers Continuous pore pressure Continuous seepage The radius of influence of the radial boundary at the boundary. ; at the boundary of the pile core At the pile-soil interface 2) Determine the time boundary conditions, under staged loading, the first... j At the initial moment of application of the first load, , , For the first j Final value of level load, This represents the final value of the previous load level; Step 4: Solve the consolidation control equations using the separation of variables method and Fourier series expansion, divided into two scenarios: single-stage instantaneous loading and multi-stage instantaneous loading. 1) Solve for single-stage instantaneous loading, σ(t)=σ0, t≥0; First, make formal assumptions about the solution, and then press the upper hole. Set in the form of a space function × a time function: ； ； in, These are the Fourier coefficients. For eigenvalues; The upper pore pressure space characteristic function, ); The lower pore pressure space characteristic function, ); These are spatial eigenvalues ​​derived from boundary conditions; Then determine the Fourier coefficients : Using the initial condition t=0 Combining the orthogonality of the characteristic functions, we can solve for: ； in, ; ， ； ； 2) Solving for multi-stage instantaneous loading: In actual engineering, loading is applied in stages. The pore pressure solution for the j-th stage load is the superposition of the load increments at each stage. ； ； Step 5: Perform consolidation degree calculation, define two indicators: consolidation degree based on settlement and consolidation degree based on pore pressure, and evaluate the consolidation effect from the perspectives of deformation completion degree and pore pressure dissipation degree, respectively. 1) According to the definition of settlement, the degree of consolidation is , representing the settlement at a certain moment With final settlement The ratio: ； ； Calculated The deviation from the finite element solution is ≤3.5%, which verifies that the above calculation method is reasonable; 2) The degree of consolidation as defined by pore pressure is , is the ratio of the total remaining excess porosity at a certain moment to the total initial excess porosity. 。

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