Single-side opening and closing type temporary casing design based on finite element analysis and cast-in-place pile construction method

Abstract

This invention relates to the field of finite element analysis technology, and provides a method for designing and constructing cast-in-place piles using a single-sided open-closed temporary casing based on finite element analysis. The method includes importing constitutive parameters of soft rheological silt into computer-aided engineering nonlinear finite element software to establish a spatial mesh model of the single-sided open-closed temporary casing with upper and lower reinforcing cylinder ends and a central standard cylinder; applying high-order friction penalty function contact constraints to the sliding pin, tension rod flange, and positive and negative labyrinth joints; sequentially loading three dynamic simulation conditions: pressing, holding, and large deformation during pull-out; outputting a solid manufacturing data table based on the simulation results of the three dynamic simulation conditions; constructing a closed-loop mud circulation system to maintain head balance; and achieving low-damage pull-out and demolding. This invention combines simulation-driven design, structural optimization, and refined construction control, significantly improving the reliability, efficiency, and pile quality of cast-in-place pile construction in soft rheological strata.

Description

Technical Field

[0001] This invention relates to the field of finite element analysis technology, and in particular to a design and construction method for a single-sided open and closed temporary casing based on finite element analysis. Background Technology

[0002] In the construction of cast-in-place piles in water-related or soft soil areas, such as the Lian-Shen Waterway Improvement Project, a common approach is to use a single-sided opening and closing temporary casing as a key device to assist in hole formation and concrete pouring. This type of casing, by setting a longitudinal slit on one side of the casing and a matching locking mechanism, achieves the function of closing during driving and opening during extraction, thereby effectively reducing extraction resistance and solving the engineering problem of conventional integral casings being difficult to extract in deep soft soil or mud environments. However, actual construction shows that the behavior of the single-sided opening and closing temporary casing in complex underground mechanical environments exhibits extremely strong nonlinear characteristics, specifically manifested in the following three stages: the pile driving stage; the load-bearing operation stage; and the extraction and opening stage.

[0003] To address the aforementioned issues, current engineering practices primarily rely on two traditional solutions: first, increasing the thickness of the casing wall, which not only significantly increases the burden on hoisting, transportation, and extraction equipment but also results in substantial material waste; second, setting the inclination angle of the inclined groove and the parameters of the locking teeth based on experience, lacking quantitative calculation basis for key mechanical parameters such as soil shear stress, mud pressure difference, and stress jump, leading to buckling instability of the casing underground, fatigue or brittle fracture of the locking teeth, and mud leakage at the openings causing hole collapse, ultimately resulting in large-scale over-cubic-meter concrete, seriously affecting the quality, construction period, and cost of pile formation.

[0004] Current construction techniques lack a digital twin method that integrates CAE (Computer-Aided Engineering) calculations with on-site rotary drilling, mud circulation parameters, and concrete initial setting time measurement. This results in a failure to establish a closed-loop feedback between finite element simulation results during the casing structure design phase and real-time on-site monitoring data. Key construction parameters such as rotary drilling depth, mud level and density adjustment, concrete pouring and initial setting progress lack a linkage mechanism with the casing opening and closing timing and locking tooth release strategy. Consequently, it is impossible to dynamically predict the casing stress state and failure risk during construction, leaving only post-construction remediation based on experience. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis, comprising the following steps: Constitutive parameters of soft rheological silt were imported into computer-aided engineering nonlinear finite element software to establish a single-sided open and closed temporary casing spatial mesh model of the upper and lower reinforcing cylinder ends and the middle standard cylinder; high-order friction penalty function contact constraints were applied to the sliding pin, tension rod flange and positive and negative labyrinth joint; three dynamic simulation conditions were applied in sequence: pressing condition, holding condition and large deformation pulling condition. Based on the simulation results of three dynamic simulation conditions, extreme values ​​are automatically extracted through iterative calculations to obtain the optimal thickness of the standard section in the middle of the casing, the optimal thickening ratio of the upper and lower reinforcing cylinder ends, and the optimal inclination angle parameters of the inclined groove that prevents the sliding pin from jamming and minimizes the tension. The resulting physical manufacturing data table is then output.

[0006] Optionally, the pressing condition involves high-frequency vibration and lateral pressure, analyzing the tangential shear stress concentration in the labyrinth groove; the holding condition involves internal asymmetric water pressure and external creep soil extrusion pressure, using fluid-structure interaction to calculate the diameter reduction distortion and buckling critical point; and the pull-out large deformation condition involves simulating the displacement of the tension rod and the sliding of the inclined groove, calculating the optimal tension curve required for opening.

[0007] Optionally, the process of establishing a single-sided open / closed temporary casing space mesh model for the upper and lower reinforcing cylinder ends and the middle standard cylinder includes the following steps: In computer-aided engineering nonlinear finite element software, the creep coefficient and rheological index in the constitutive parameters are used as time hardening parameters and assigned to the soil element integration points in the contact area of ​​the outer wall of a single-sided open and closed temporary casing, respectively, to generate a nonlinear rheological field that varies with the loading time. The nonlinear rheological field is coupled with the external normal node displacement of the spatial mesh model of the single-sided open and closed temporary casing to obtain the lateral compressive stress distribution under the indentation condition, the creep soil pressure growth curve under the holding condition, and the spatial node force vector of viscous adsorption under the pull-out condition. Based on the spatial node force vector, a spatial mesh model of a single-sided open and closed temporary casing is established for the upper and lower reinforcing cylinder ends and the middle standard cylinder. The sliding pin surface and the inner wall of the inverted V-shaped groove form a contact pair. The tooth surface interlocking depth of the positive and negative labyrinth slot is converted into the initial value of the penalty function contact stiffness, and the axial force transmission path of the tension rod flange end face is superimposed. On the radial degree of freedom of the middle standard cylinder of the single-sided open and closed temporary casing spatial mesh model, the buckling mode wavenumber under the load condition is locked. The peak stress region of vibration and impact under the indentation condition is associated with the axial degrees of freedom at the upper and lower reinforcing cylinder ends; a single-sided open and closed temporary casing space mesh model containing nodal force vectors, contact pair stiffness and degree of freedom constraints is output for loading calculation of three dynamic simulation conditions.

[0008] Optionally, the process of outputting the entity manufacturing data table includes the following steps: The maximum stress value of the tangential shear stress concentration region of the labyrinth groove output from the simulation of the pressing condition, and the maximum axial tensile stress value of the tension rod flange region output from the simulation of the pull-out large deformation condition are read into the data buffer of the example iteration; the example iteration performs constraint judgment on each combination of parameter matrix in turn; the combination that meets the constraint judgment is retained, the rest are discarded, and the feasible parameter matrix is ​​output. For each set of wall thickness values ​​in the feasible parameter matrix, input them sequentially into the simulation results under the load condition. Extract the two extreme values ​​corresponding to each set of wall thicknesses. The two extreme values ​​are the maximum diameter reduction indentation of the central standard cylinder and the overall buckling critical load factor. Filter out all wall thickness values ​​where the diameter reduction indentation is less than the allowable deviation and the load factor is greater than the safety threshold. Select the minimum value from these as the optimal thickness of the central standard section. The example iterative program returns the optimal thickness to the feasible parameter matrix, determines the corresponding wall thickness values ​​of the upper and lower reinforcing cylinder ends, and outputs the optimal thickening ratio. The optimal thickness and best thickening ratio of the central standard section are written into the parameter locking area. The example iterative program sets the inclination angle of the inverted V-shaped groove relative to the axis of the casing as the only iteration variable, generating a discrete angle sequence from the lower limit angle to the upper limit angle. The example iterative program compares the maximum contact pressure value of the discrete angle sequence with the allowable compressive stress of the sliding pin material and eliminates all angles where the contact pressure exceeds the allowable value. Among the remaining inclination angles, the example iterative program extracts the angle corresponding to the minimum value of the tensile peak and outputs it as the optimal inclination angle parameter of the groove.

[0009] Optionally, the example iteration sets the wall thickness of the central standard cylinder as the first iteration variable and the ratio of the wall thickness of the upper and lower reinforcing cylinder ends to the wall thickness of the central standard cylinder as the second iteration variable, generating a parameter matrix containing multiple combinations of wall thickness and ratio; the constraint judgment condition is that the maximum tangential shear stress does not exceed the material yield limit and the maximum axial tensile stress of the flange does not exceed the tensile strength limit.

[0010] Optionally, the simulation iteration compares the maximum diameter reduction indentation with the preset allowable deviation value of the inner diameter of the casing; at the same time, it compares the overall buckling critical load factor with the design safety threshold; and substitutes each tilt angle into the simulation results of the large deformation condition during pull-out, and reads two output values ​​under the tilt angle: the maximum contact pressure value of the contact surface between the sliding pin and the inclined groove, and the peak value of the output tension of the jack.

[0011] Optionally, the process of outputting the feasible parameter matrix includes the following steps: The simulation iteration writes the maximum stress value of the labyrinth groove tangential shear stress concentration area output from the indentation working condition simulation and the maximum axial tensile stress value of the tension rod flange area output from the pull-out large deformation working condition simulation into the first and second storage units of the data buffer, respectively; sets the wall thickness of the middle standard cylinder as the first iteration variable and the ratio of the wall thickness of the upper and lower reinforcing cylinder ends to the wall thickness of the middle standard cylinder as the second iteration variable, generating a parameter matrix containing multiple sets of wall thickness values ​​and ratio values, which is stored in the third storage unit of the data buffer; Read the wall thickness and ratio values ​​of each combination sequentially from the third storage unit of the data cache, and substitute the combination into the material yield strength and tensile strength values ​​for dual judgment; Traverse all combinations in the third storage unit of the data buffer, and sequentially read the corresponding reservation flags in the fourth storage unit; copy the combinations with the reservation flags being true from the third storage unit to the fifth storage unit. After the copying is complete, the set of combinations in the fifth storage unit is the feasible parameter matrix.

[0012] Optionally, the dual judgment includes: sending the maximum tangential shear stress value and the material yield strength value into the first comparison unit and outputting the first comparison flag; sending the maximum axial tensile stress value and the tensile strength limit value of the flange into the second comparison unit and outputting the second comparison flag; sending the first comparison flag and the second comparison flag into the logic AND operation unit at the same time to generate a combined retention flag, and storing the retention flag and the combination in the fourth storage unit of the data cache.

[0013] Optionally, the process of determining the corresponding upper and lower reinforcing cylinder end wall thickness values ​​includes the following steps: The numerical example iteratively compares the maximum diameter reduction indentation value with the pre-written allowable deviation value of the casing inner diameter; at the same time, it compares the overall buckling critical load factor value with the pre-written design safety threshold value. Retain all wall thickness values ​​where the diameter reduction indentation is less than the allowable deviation and the buckling load factor is greater than the safety threshold, discard the remaining wall thicknesses, and generate an intermediate value sequence consisting of wall thicknesses that meet the two conditions; extract the smallest value from the intermediate value sequence and output it as the optimal thickness of the central standard section. Search the feasible parameter matrix for wall thickness entries that match the optimal thickness value, and determine the wall thickness values ​​of the upper and lower reinforcing cylinder ends corresponding to the wall thickness entries; based on the locked upper and lower reinforcing cylinder end wall thickness values ​​and the optimal thickness value of the middle standard section, determine the magnification factor of the upper and lower reinforcing cylinder end wall thickness relative to the optimal thickness of the middle standard section, and output the magnification factor as the optimal thickness increase ratio.

[0014] Optionally, the casing segments are manufactured according to the optimized data in the physical manufacturing data sheet and spliced ​​with high-strength bolts. The tension rod is pulled by jacks to force the sliding pin of the opening and closing plate to retract inward. After the casing is rigidly locked and closed, it is pressed into the soil by high-frequency vibration. The optimized rotary drilling bit is lowered to advance the footage, and a closed-loop mud circulation system is constructed to maintain the water head balance. After the concrete is poured, the golden initial setting time point is determined according to the setting performance test of the cementitious material. The tension rod is released in the reverse direction to make the sliding pin rise to the wide distance area of ​​the inclined groove. The casing is slightly expanded along the opening to decouple the ultimate frictional resistance and achieve low-damage pull-out and demolding.

[0015] This invention uses nonlinear finite element simulation and dynamic working condition simulation to accurately predict the mechanical behavior of the casing during the pressing, holding, and extraction processes, optimizing structural parameters to ensure sufficient shear, buckling, and distortion resistance in soft rheological geological conditions. The physical manufacturing process is based on optimized data, improving the overall stiffness and local strength of the casing and reducing stress concentration. During construction, the casing is forced into the soil through forced closure and high-frequency vibration, effectively reducing insertion resistance. A closed-loop mud circulation system maintains borehole stability, preventing diameter reduction or borehole collapse. After concrete pouring, the initial setting time is precisely controlled based on the properties of the cementitious materials. By releasing the tension rod in the reverse direction, the casing slightly expands along the opening, decoupling the ultimate frictional resistance between the casing and the concrete, achieving smooth extraction of the casing and avoiding structural damage and borehole wall disturbance.

[0016] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of the design of a single-sided open and closed temporary casing and the construction method of cast-in-place piles based on finite element analysis in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the design and construction method of a single-sided open and closed temporary casing based on finite element analysis in Embodiment 1 of the present invention. Figure 3 This is a process diagram of establishing a single-sided open and closed temporary protective casing spatial grid model for the upper and lower reinforcing cylinder ends and the middle standard cylinder in Embodiment 2 of the present invention; Figure 4 This is a process diagram of outputting the entity manufacturing data table in Embodiment 6 of the present invention. Detailed Implementation

[0019] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms "a," "say," and "this" used in the embodiments of this application are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms used herein refer to and / or include any or all possible combinations of one or more associated listed items.

[0021] In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application. In the description of this application, it should be understood that the terms first, second, third, etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0022] Example 1: As Figure 1 As shown, this embodiment of the invention provides a design method for a single-sided open-closed temporary casing and a method for constructing cast-in-place piles based on finite element analysis, comprising the following steps: S100: The constitutive parameters of the soft rheological silt were imported into the computer-aided engineering nonlinear finite element software to establish a single-sided open and closed temporary casing space mesh model of the upper and lower reinforcing cylinder ends and the middle standard cylinder; high-order friction penalty function contact constraints were applied to the sliding pin, tension rod flange and positive and negative labyrinth joint; three dynamic simulation conditions were applied in sequence: pressing condition, holding condition and large deformation pulling condition. Among them, the pressing condition is high-frequency vibration and lateral pressure, and the tangential shear stress concentration of the labyrinth groove is analyzed; the holding condition is internal asymmetric water pressure and external creep soil extrusion pressure, and fluid-structure interaction is used to calculate the diameter reduction distortion and buckling critical point; the pull-out large deformation condition is to simulate the displacement of the tension rod and the sliding of the inclined groove, and calculate the optimal tension curve required for opening. S200: Based on the simulation calculation results of three dynamic simulation conditions, the extreme values ​​are automatically extracted through case iteration to obtain the optimal thickness of the standard section in the middle of the casing, the optimal thickening ratio of the upper and lower reinforcing cylinder ends, and the optimal inclination angle parameters of the inclined groove with no jamming of the sliding pin and the minimum tension, and output the solid manufacturing data table. S300: The casing segments are manufactured according to the optimized data in the physical manufacturing data sheet and spliced ​​with high-strength bolts. The tension rod is pulled by jacks to force the sliding pin of the opening and closing plate to retract inward. After the casing is rigidly locked and closed, it is pressed into the soil by high-frequency vibration. The optimized rotary drilling bit is lowered to advance the footage and a closed-loop mud circulation system is constructed to maintain the water head balance. After the concrete is poured, the golden initial setting time point is determined according to the setting performance test of the cementitious material. The tension rod is released in the reverse direction to make the sliding pin rise to the wide distance area of ​​the inclined groove. The casing is slightly expanded along the opening to decouple the ultimate frictional resistance and achieve low-damage pull-out demolding.

[0023] Among them, the constitutive parameters of soft rheological silt describe the mathematical model parameters of the silt's deformation and flow characteristics under stress, including creep coefficient and rheological index. Relationship with casing / construction: Soft rheological silt geology has high water content, low strength, thixotropy, and creep. Accurate input of constitutive parameters in finite element analysis can simulate lateral compression during injection, creep soil pressure growth during holding load, and the viscous adsorption of the soil on the casing during extraction, optimizing the casing structure to avoid diameter reduction, cracking, or seizing. The casing is divided into three sections along the axial direction: the upper and lower reinforcing cylinder ends and the middle standard cylinder. The reinforcing cylinder ends are located at the top and bottom, and the middle standard cylinder is located in the middle section. The connection with the casing or construction is as follows: when pressed in, the ends are subjected to hammer or vibration impact force, and when pulled out, the ends are subjected to tension concentrated force, so they need to be reinforced. The middle section mainly bears the radial force of soil and water pressure. Optimizing its thickness can reduce the self-weight while ensuring buckling resistance. The single-sided opening and closing structure requires that each section can elastically open after the joint is opened. The segmented differential thickness can control the opening deformation position and facilitate demolding. The sliding pin is a cylindrical metal pin installed on the opening and closing plate, which can slide relative to the inverted V-shaped groove on the side wall of the casing. Its connection with the casing or construction is as follows: as the core opening and closing actuator, when the tension rod is pulled up, the sliding pin moves down along the groove, forcing the casing to retract radially inward, achieving rigid deadlock closure; when released in the reverse direction, the sliding pin rises to the wide gap area, and the casing springs open along the opening to slightly expand its diameter, decoupling the friction with the pile body / soil. Its fit clearance and inclination angle with the groove directly affect the magnitude of the opening tension and the reliability of anti-jamming. The tension rod flange and the positive and negative labyrinth joint are annular flange components that connect the tension rod and the opening and closing plate, transmitting the axial tensile force of the jack. The positive and negative labyrinth joints are a pair of interlocking, tortuous sealing structures designed at the edge of the casing opening, with alternating positive and negative labyrinths to prevent mud or concrete slurry from seeping into the casing. Regarding their connection to the casing and construction: the flange area bears high tensile stress under load conditions, and its strength is verified through CAE; the labyrinth joints form a long-path seal when the casing is closed, preventing drilling mud or poured concrete from leaking out of the opening, ensuring stable water head in the borehole and pile quality; simultaneously, its special frictional contact behavior needs to be accurately simulated using penalty function constraints. Higher-order friction penalty function contact constraints are used in finite element analysis to calculate the normal pressure and tangential frictional force between contact surfaces, such as the sliding pin and the groove, and the tooth surface of the labyrinth joint. Higher-order friction models employ nonlinear friction models, such as friction coefficients dependent on velocity or pressure. Penalty functions transform contact constraints into force balance equations by introducing penalty stiffness, allowing for minor penetrations but imposing significant penalty forces. Relevance to casing or construction: the contact state changes drastically when the sliding pin slides in the inclined groove or when the labyrinth seal opens and closes. Accurate simulation of friction forces can calculate the inclined groove angle with the minimum tension and avoid calculation non-convergence due to excessive penalty stiffness. Constraints are also a key numerical means of evaluating whether the casing can open smoothly without jamming during pull-out operations.In the simulation results of the three working conditions, the CAE software automatically searches for and extracts the maximum response quantities, such as the maximum Mises stress, maximum radial deformation, maximum buckling load factor, and minimum tensile force curve value. Its correlation with the casing or construction: the design objective is to minimize the tensile force required to open the casing while satisfying strength, stiffness, and stability constraints, facilitating on-site jack operation; extreme value extraction is the objective function of iterative optimization: for example, the maximum diameter reduction under the sustained load condition must not lead to permanent casing indentation; under the pull-out condition, the minimum peak value of the optimal tensile force curve corresponds to the optimal inclination angle of the inclined groove. The optimal thickness of the standard cylinder is determined after multiple finite element iterations. It is a wall thickness value that can resist the extreme diameter reduction and overall buckling caused by fluid-structure interaction under load conditions, without making the casing too heavy or difficult to open. For example, 16mm is shown in the original text. Its relationship with casing / construction: if it is too thin, buckling instability will occur under load, and the casing will be crushed and unable to be pulled out; if it is too thick, the casing will be too rigid when pulled out, and it will not be able to expand the diameter slightly along the opening, resulting in a surge in demolding force or even jamming. The optimal thickness is the structural basis for realizing the unilateral opening and closing function. The optimal thickening ratio is the magnification factor of the wall thickness of the upper and lower reinforcing cylinder ends relative to the central standard cylinder. For example, if the central thickness is 16mm and the reinforcing end thickness is 24mm, the ratio is 1.5. Its relation to the casing or construction: if the ratio is too low, the ends will crack under vibration pressing or pulling forces; if the ratio is too high, the overall weight of the casing will increase, manufacturing will be difficult, and the sudden change in stiffness at the transition between the reinforcing end and the standard cylinder will easily cause stress concentration. The optimal ratio is determined by the tangential shear stress distribution of the reinforcing end under pressing conditions and the stress extreme value of the tie rod flange area under pulling conditions. The optimal inclination angle parameter of the inclined groove refers to the inclination angle of the inverted V-shaped groove on the side wall of the casing, which is larger at the top and smaller at the bottom, relative to the axial direction. It is usually expressed as the angle or slope with respect to the axial direction. Its relationship with the casing or construction is as follows: This angle directly determines the mechanical amplification relationship when the sliding pin slides - the smaller the inclination angle, the smaller the pulling force required to open the casing, but the longer the sliding stroke and the easier it is to self-lock; the larger the inclination angle, the higher the pulling force required, but the shorter the stroke. The optimal inclination angle is the value calculated by simulation of the large deformation working condition of the pull-out, which can ensure that the sliding pin does not get stuck, the contact pressure does not exceed the limit, and the jack output pulling force is minimized. It is the key geometric parameter for achieving zero-damage pull-out.

[0024] Specific operating procedures for the setting performance test of cementitious materials: Sample preparation: Use a 5mm sieve to sieve a representative concrete mixture to obtain mortar. Fill the metal sample tube in three batches, and select a vibrating table or tamping rod to compact it according to the slump, ensuring that the mortar is slightly below the tube opening and immediately cover it; Simulated curing: Place the sample tube in a standard curing room at 20℃±2℃ and relative humidity ≥90%, or cure it under the same conditions at the construction site; Timed testing: Start timing from the time the concrete is mixed with water. Test once every 0.5 hours in the early stage, and increase the interval as the setting time approaches. Before testing, tilt the sample tube to absorb surface water; Penetration measurement: Place the sample tube on the penetration resistance meter, and make the probe penetrate the mortar to a depth of 25mm±2mm at a uniform speed within 10s±2s, and record the maximum resistance value at this time; As the resistance increases, change the probe in sequence from large to small, with the bearing area from 100mm²→50mm²→20mm²; Curve plotting: Continue testing, calculate the penetration resistance (MPa) for each test, and plot the penetration resistance-time curve.

[0025] The golden initial setting time is defined by two key thresholds: the initial threshold, approximately 3.5 MPa: when the penetration resistance value on the curve first reaches or exceeds 3.5 MPa, the corresponding time is the initial setting time; it marks the beginning of the concrete losing its plasticity and is the ideal window for pulling out the casing; the final threshold, approximately 28.0 MPa: when the penetration resistance value reaches 28.0 MPa, the corresponding time is the final setting time; it marks the complete hardening of the concrete, at which point pulling out the casing becomes extremely difficult.

[0026] The working principle and beneficial effects of the above technical solution are as follows: The specific principle is as follows: Figure 2 As shown, this embodiment uses nonlinear finite element simulation and dynamic working condition simulation to accurately predict the mechanical behavior of the casing during the pressing, holding, and extraction processes, optimizing structural parameters to ensure that the casing has sufficient shear, buckling, and distortion resistance in soft rheological strata. The physical manufacturing process is based on optimized data to improve the overall stiffness and local strength of the casing and reduce stress concentration. During construction, the casing is forced into the soil through forced closure and high-frequency vibration, effectively reducing insertion resistance. A closed-loop mud circulation system maintains borehole stability, preventing diameter reduction or borehole collapse. After concrete pouring, the initial setting time is precisely controlled based on the properties of the cementitious materials. By releasing the tension rod in the reverse direction, the casing slightly expands along the opening, decoupling the ultimate frictional resistance between the casing and the concrete, achieving smooth extraction of the casing and avoiding structural damage and borehole disturbance. This embodiment combines simulation-driven design, structural optimization, and refined construction control, significantly improving the reliability, efficiency, and pile quality of cast-in-place pile construction in soft rheological strata.

[0027] This embodiment quantifies the nonlinear mechanical response of the casing at each stage, rationally determining wall thickness, slot angle, locking tooth form, and material selection. It also utilizes a digital twin platform to achieve real-time adjustment and early warning of construction parameters, significantly reducing material consumption and construction risks while ensuring the structural safety of the casing. This embodiment constructs a high-fidelity fluid-structure interaction model in CAE software, accurately calculating the safe geometric dimensions of the upper and lower reinforcing ends, the standard casing, and the optimal opening and closing parameters of the inclined groove. These optimal opening and closing parameters guide equipment manufacturing, and in conjunction with optimized rotary drilling, closed-circuit mud circulation, and gel characteristic determination on-site, it achieves cost reduction, weight reduction, zero hole collapse, and low filling coefficient construction. The CAE digital optimization in this embodiment abandons the extensive design that excessively consumes steel, reducing hoisting weight and cost. Optimized rotary drilling with anti-disturbance drilling and closed-circuit mud circulation combined with pressure stabilization achieve truly environmentally friendly, collapse-free construction. Physical mechanical unloading and extraction, combined with scientific test block time anchoring, ensure the integrity of the underwater cast-in-place pile.

[0028] Example 2: As Figure 3 As shown, based on Example 1, the process of establishing a single-sided open and closed temporary protective casing spatial grid model for the upper and lower reinforcing cylinder ends and the middle standard cylinder provided by this embodiment of the invention specifically includes the following steps: S101: In the nonlinear finite element software for computer-aided engineering, the creep coefficient and rheological index in the constitutive parameters are used as time hardening parameters and assigned to the soil element integration points in the contact area of ​​the outer wall of the single-sided open and closed temporary casing, respectively, to generate a nonlinear rheological field that varies with the loading time. The nonlinear rheological field is coupled with the external normal node displacement of the spatial mesh model of the single-sided open and closed temporary casing to obtain the lateral extrusion stress distribution under the indentation condition, the creep soil pressure growth curve under the holding condition, and the spatial node force vector of the viscous adsorption effect under the pull-out condition. S102: Based on the spatial node force vector, establish a spatial mesh model of a single-sided open and closed temporary casing for the upper and lower reinforcing cylinder ends and the middle standard cylinder; make the sliding pin surface and the inner wall of the inverted V-shaped groove form a contact pair, convert the tooth surface interlocking depth of the positive and negative labyrinth slot into the initial value of the penalty function contact stiffness, and superimpose the axial force transmission path of the tension rod flange end face; lock the buckling mode wavenumber under the load condition on the radial degree of freedom of the middle standard cylinder in the single-sided open and closed temporary casing spatial mesh model. S103: Associates the peak stress region of vibration and impact under the indentation condition on the axial degrees of freedom of the upper and lower reinforcing cylinder ends; outputs a single-sided open and closed temporary casing space mesh model containing nodal force vectors, contact pair stiffness and degree of freedom constraints, for loading calculation of three dynamic simulation conditions.

[0029] The working principle and beneficial effects of the above technical solution are as follows: The model in this embodiment can complete the coupled simulation of the entire process of pressing, holding, and pulling out in one go; the optimization algorithm can directly read the simulation extreme values ​​to give manufacturing parameters such as thickness and inclination angle; the casing manufactured on site according to the manufacturing parameters can be pulled out with zero damage at the golden initial setting point, the construction rhythm is compact, and the pile body quality is uniform.

[0030] Example 3: Based on Example 2, the coupling process between the nonlinear rheological field and the external normal nodal displacement of the single-sided open-closed temporary casing spatial grid model provided in this embodiment of the invention specifically includes the following steps: S1011: The creep coefficient and rheological index in the constitutive parameters of the soft rheological silt are set as time hardening parameters and written into the soil element integration points of the contact area of ​​the outer wall of the single-sided open and closed temporary casing to generate a nonlinear rheological field that varies with the loading time. The nonlinear rheological field is coupled with the external normal node displacement of the single-sided open and closed temporary casing spatial grid model to obtain the lateral compressive stress distribution under the indentation condition, the creep soil pressure growth curve under the holding condition, and the spatial node force vector of the viscous adsorption effect under the pull-out condition. S1012: Based on the spatial node force vector, establish a single-sided open and closed temporary casing spatial mesh model for the upper and lower reinforcing cylinder ends and the middle standard cylinder; combine the sliding pin surface with the inner wall of the inverted V-shaped groove to form a contact pair, read the tooth surface interlocking depth value of the positive and negative labyrinth slot and convert it into the initial value of the penalty function contact stiffness, and then superimpose the axial force transmission path of the tension rod flange end face onto the initial value; calculate the buckling mode wavenumber under the load-bearing condition with the radial degree of freedom position locked in the middle standard cylinder. S1013: Transfers the buckling mode wavenumber to the axial degree of freedom of the upper and lower reinforcing cylinder ends, and associates the vibration and impact peak stress region extracted from the pressing condition to this axial degree of freedom; it gathers the spatial node force vector, contact pair stiffness and degree of freedom constraints, and axial degree of freedom association results, and outputs a complete single-sided open and closed temporary casing spatial mesh model for loading calculation of three dynamic simulation conditions.

[0031] The working principle and beneficial effects of the above technical solution are as follows: In this embodiment, the soil rheology and structural response during the pressing, holding and pulling-out stages are captured simultaneously through one modeling, and the optimization algorithm directly reads the extreme values; the casing manufactured on site according to the parameters can be pulled out with low tension and zero damage at the predetermined initial setting point, the construction is continuous and the pile body is uniform.

[0032] Example 4: Based on Example 3, the process of collecting spatial nodal force vectors, contact pair stiffness and degree-of-freedom constraints, and axial degree-of-freedom correlation results provided in this embodiment of the invention specifically includes the following steps: S10131: Extract three components from the output spatial node force vector, namely the lateral compressive stress distribution under the indentation condition, the creep soil pressure growth curve under the load-bearing condition, and the spatial node force vector of the viscous adsorption effect under the pull-out condition. Write the three components sequentially onto the outer surface nodes of the single-sided open and closed temporary casing spatial mesh model. At the same time, read the penalty function stiffness value and the axial force transmission path superposition value of the contact pair between the sliding pin and the inclined groove from the contact stiffness and degree of freedom constraints. Write the two sets of values ​​into the attribute fields of the corresponding contact surface in the single-sided open and closed temporary casing spatial mesh model to generate an intermediate mesh model carrying external load and contact stiffness. S10132: Extract the radial degree of freedom locking value of the central standard cylinder from the buckling mode wavenumber, and apply the radial degree of freedom locking value of the central standard cylinder to the radial degree of freedom position of the central standard cylinder in the generated intermediate mesh model; then extract the correlation mapping table between the axial degree of freedom of the upper and lower reinforcing cylinder ends and the peak stress region of vibration and impact from the output axial degree of freedom correlation results, and write the correlation mapping table to the axial degree of freedom nodes of the upper and lower reinforcing cylinder ends of the intermediate mesh model to generate a secondary mesh model carrying degree of freedom constraints and stress region correlation; S10133: All fields in the generated secondary mesh model are subjected to integrity verification, including non-empty checks of the force vectors at the outer surface nodes, numerical range checks of the contact pair attribute fields, validity checks of the degree of freedom locking values, and consistency checks of the references in the axial association mapping table; after the verification passes, the secondary mesh model is output as a complete single-sided open and closed temporary casing space mesh model.

[0033] The working principle and beneficial effects of the above technical solution are as follows: This embodiment gradually integrates the dispersed load data, contact parameters, constraints and correlations into a unified mesh framework, forming a finite element model with complete structure and physical information; it can simultaneously reflect the effects of multiple working conditions, nonlinear contact behavior, local stability constraints and dynamic response correlations, providing a reliable and efficient numerical basis for subsequent static and dynamic analysis, buckling verification and fatigue assessment.

[0034] Example 5: Based on Example 4, the process of generating a secondary mesh model with degree-of-freedom constraints and stress region association provided by this embodiment of the invention specifically includes the following steps: S101321: From the output axial degree of freedom correlation results, read the correspondence between the axial degree of freedom numbers of the upper and lower reinforcing cylinder ends and the peak stress area numbers of the vibration and impact, organize the correspondence into an correlation mapping table, and store it in the temporary storage unit of the data cache area; each row of the correlation mapping table contains an axial degree of freedom number and a stress area number bound to it; S101322: Read the association mapping table line by line from the temporary storage unit of the data buffer, and write the stress region number in each line into the attribute field of the corresponding axial degree of freedom node in the generated intermediate mesh model; the writing operation is as follows: locate the node in the intermediate mesh model that matches the read axial degree of freedom number, update the value of the stress region identifier field of the node to the read stress region number; traverse all rows of the association mapping table, complete the attribute field update of all nodes, and generate an intermediate mesh model carrying stress region association markers; S101323: Read the constraint information applied to the radial degree of freedom position of the central standard cylinder from the output radial degree of freedom lock value of the central standard cylinder; merge the constraint information with the generated central mesh model carrying stress region association markers: write the constraint information into the constraint field of the corresponding degree of freedom of the central standard cylinder of the model, while retaining the written stress region association markers; after merging, the program outputs the model as a secondary mesh model carrying degree of freedom constraints and stress region associations.

[0035] The working principle and beneficial effects of the above technical solution are as follows: This embodiment completes the systematic integration from the correlation mapping between axial degrees of freedom and stress regions to the application of local constraint conditions, generating a secondary mesh model that simultaneously carries stress region correlation markers and degree of freedom constraints; it can not only reflect the stress concentration characteristics of a specific region of the structure under dynamic load, but also effectively control local buckling behavior through constraint conditions, providing a numerical model with both dynamic response orientation and constraint completeness for carrying out vibration and shock analysis and stability verification.

[0036] Example 6: As Figure 4 As shown, based on Example 1, the process of outputting the entity manufacturing data table provided in this embodiment of the invention specifically includes the following steps: S201: The maximum stress value of the tangential shear stress concentration area of ​​the labyrinth groove output from the pressing-in working condition simulation and the maximum axial tensile stress value of the tension rod flange area output from the pull-out large deformation working condition simulation are read into the data buffer of the example iteration; the example iteration sets the wall thickness of the middle standard cylinder as the first iteration variable and the ratio of the wall thickness of the upper and lower reinforcing cylinder ends to the wall thickness of the middle standard cylinder as the second iteration variable, generating a parameter matrix containing multiple combinations of wall thickness and ratio; the example iteration sequentially performs constraint judgment on each combination, the constraint judgment condition is that the maximum tangential shear stress does not exceed the material yield limit and the maximum axial tensile stress of the flange does not exceed the tensile strength limit; combinations that meet both conditions are retained, and the rest are discarded, and the feasible parameter matrix is ​​output; S202: Input the wall thickness values ​​of each group in the feasible parameter matrix into the simulation results of the load-bearing condition in sequence, extract the two extreme values ​​corresponding to each group of wall thicknesses. The two extreme values ​​are the maximum diameter reduction indentation of the central standard cylinder and the overall buckling critical load factor. The example iteration compares the maximum diameter reduction indentation with the preset allowable deviation value of the inner diameter of the casing. At the same time, it compares the overall buckling critical load factor with the design safety threshold. Select all wall thickness values ​​where the diameter reduction indentation is less than the allowable deviation and the load factor is greater than the safety threshold, and select the minimum value as the optimal thickness of the central standard section. The example iteration program returns the optimal thickness to the feasible parameter matrix, determines the corresponding wall thickness values ​​of the upper and lower reinforcing cylinder ends, and outputs the optimal thickening ratio. S203: The optimal thickness and best thickening ratio of the central standard section are written into the parameter locking area. The example iteration program sets the inclination angle of the inverted V-shaped groove relative to the axis of the casing as the only iteration variable, generating a discrete angle sequence from the lower limit angle to the upper limit angle. Each inclination angle is substituted into the simulation results of the large deformation condition of the pull-out, and two output values ​​are read under the inclination angle: the maximum contact pressure value of the contact surface between the sliding pin and the groove, and the peak value of the output tension of the jack. The example iteration program compares the maximum contact pressure value with the allowable compressive stress of the sliding pin material and eliminates all angles where the contact pressure exceeds the allowable value. Among the remaining inclination angles, the example iteration program extracts the angle corresponding to the minimum value of the peak tension and outputs it as the optimal inclination angle parameter of the groove.

[0037] The working principle and beneficial effects of the above technical solution are as follows: In this embodiment, the extreme value of the labyrinth groove shear during pressing and the axial tensile stress of the flange during pulling are read into the buffer together. The iterative program treats the wall thickness and thickening ratio as continuously adjustable design variables, and instantly completes the screening under the yield-ultimate dual criteria. The remaining combination avoids any one-time material failure, and the invalid area of ​​the design space is eliminated in one go. By substituting the wall thickness of the initial screening into the load-bearing condition, the diameter reduction depression and buckling margin are examined respectively, and the thinnest solution that meets both conditions is locked as the thickness of the middle standard section. At the same time, the thickening ratio of the upper and lower reinforcing ends is determined. The stiffness retention capability of the structure in long-term use is directly aligned with the minimum steel consumption. Any redundant wall thickness is eliminated, and the material volume and cost are then converged to the lowest feasible zone. Only the inclination angle of the inclined groove is allowed to change freely, and the optimal compromise between the sliding pin contact pressure and the peak value of the jack tension is found in the remaining space. The angle of the inclined groove is compressed to the only landing point where contact is not lost and the pulling force is minimized. The tonnage of the jack required for end unlocking naturally falls within the controllable range, and the lifting operation is no longer restricted by additional power reserves.

[0038] In summary, this embodiment links all the data of the four key aspects of stress, deformation, buckling and unlocking into a closed chain. Once the physical manufacturing data sheet is output, the casing can maintain structural safety and be smoothly recovered with the least amount of material and the least amount of pulling force during the entire process of pressing, holding and pulling out, thus achieving the overall optimization of materials, energy consumption and construction cycle.

[0039] Example 7: Based on Example 6, the process of outputting the feasible parameter matrix provided in this embodiment of the invention specifically includes the following steps: S2011: The simulation iteration writes the maximum stress value of the labyrinth groove tangential shear stress concentration area output by the indentation working condition simulation and the maximum axial tensile stress value of the tension rod flange area output by the pull-out large deformation working condition simulation into the first and second storage units of the data buffer, respectively; sets the wall thickness of the middle standard cylinder as the first iteration variable and the ratio of the wall thickness of the upper and lower reinforcing cylinder ends to the wall thickness of the middle standard cylinder as the second iteration variable, generating a parameter matrix containing multiple sets of wall thickness values ​​and ratio values, which is stored in the third storage unit of the data buffer; S2012: Read the wall thickness and ratio values ​​of each combination sequentially from the third storage unit of the data buffer. Substitute the combination into the material yield strength and tensile strength values ​​for dual judgment: send the maximum tangential shear stress value and the material yield strength value into the first comparison unit and output the first comparison flag; send the maximum flange axial tensile stress value and the tensile strength value into the second comparison unit and output the second comparison flag; send the first comparison flag and the second comparison flag into the logic AND operation unit to generate the combination's retention flag, and store the retention flag and the combination in the fourth storage unit of the data buffer. S2013: Traverse all combinations in the third storage unit of the data buffer, and read the corresponding reservation flags in the fourth storage unit in turn; copy the combinations with the reservation flags being true from the third storage unit to the fifth storage unit. After the copying is completed, the set of combinations in the fifth storage unit is the feasible parameter matrix.

[0040] The working principle and beneficial effects of the above technical solution are as follows: This embodiment establishes an automated parameter screening process based on multi-condition stress analysis and material strength criteria; it ensures the safety of parameter combinations at the strength level, and also improves the efficiency and comprehensiveness of parameter exploration through iteration and logical judgment.

[0041] Example 8: Based on Example 7, the process for determining the corresponding upper and lower reinforcing cylinder end wall thickness values ​​provided in this embodiment of the invention specifically includes the following steps: S2021: The example iteration compares the maximum diameter reduction indentation value with the pre-written allowable deviation value of the inner diameter of the casing; at the same time, it compares the overall buckling critical load factor value with the pre-written design safety threshold value. S2022: Retain all wall thickness values ​​where the diameter reduction indentation is less than the allowable deviation value and the buckling load factor is greater than the safety threshold, discard the remaining wall thicknesses, and generate an intermediate value sequence consisting of wall thicknesses that meet the two conditions; extract the smallest value from the intermediate value sequence and output it as the optimal thickness of the central standard section. S2023: Search for wall thickness entries that match the optimal thickness value in the feasible parameter matrix, and determine the wall thickness values ​​of the upper and lower reinforcing cylinder ends corresponding to the wall thickness entries; based on the locked upper and lower reinforcing cylinder end wall thickness values ​​and the optimal thickness value of the middle standard section, determine the magnification factor of the upper and lower reinforcing cylinder end wall thickness relative to the optimal thickness of the middle standard section, and output the magnification factor as the optimal thickening ratio.

[0042] The working principle and beneficial effects of the above technical solution are as follows: This embodiment realizes a coherent design process from global safety assessment to local parameter optimization, so that the casing can achieve a balance between efficient material utilization and design reliability while meeting the requirements of geometric accuracy, structural stability and local strength.

[0043] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of equivalents of this invention, this invention is also intended to include these modifications and variations.

Claims

1. A design method for a single-sided open / closed temporary casing and a method for constructing cast-in-place piles based on finite element analysis, characterized in that, Includes the following steps: Constitutive parameters of soft rheological silt were imported into computer-aided engineering nonlinear finite element software to establish a single-sided open and closed temporary casing spatial mesh model of the upper and lower reinforcing cylinder ends and the middle standard cylinder; high-order friction penalty function contact constraints were applied to the sliding pin, tension rod flange and positive and negative labyrinth joint; three dynamic simulation conditions were applied in sequence: pressing condition, holding condition and large deformation pulling condition. Based on the simulation results of three dynamic simulation conditions, extreme values ​​are automatically extracted through iterative calculations to obtain the optimal thickness of the standard section in the middle of the casing, the optimal thickening ratio of the upper and lower reinforcing cylinder ends, and the optimal inclination angle parameters of the inclined groove that prevents the sliding pin from jamming and minimizes the tension. The resulting physical manufacturing data table is then output.

2. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 1, characterized in that, in, The pressing condition involves high-frequency vibration and lateral pressure, and the tangential shear stress concentration in the labyrinth groove is analyzed. The holding condition involves internal asymmetric water pressure and external creep soil extrusion pressure, and fluid-structure interaction is used to calculate the diameter reduction distortion and buckling critical point. The large deformation pulling condition involves simulating the displacement of the tension rod and the sliding of the inclined groove, and calculating the optimal tension curve required for opening.

3. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 2, characterized in that... The process of establishing a spatial mesh model for a single-sided open / closed temporary casing for the upper and lower reinforcing cylinder ends and the middle standard cylinder includes the following steps: In computer-aided engineering nonlinear finite element software, the creep coefficient and rheological index in the constitutive parameters are used as time hardening parameters and assigned to the soil element integration points in the contact area of ​​the outer wall of a single-sided open and closed temporary casing, respectively, to generate a nonlinear rheological field that varies with the loading time. The nonlinear rheological field is coupled with the external normal node displacement of the spatial mesh model of the single-sided open and closed temporary casing to obtain the lateral compressive stress distribution under the indentation condition, the creep soil pressure growth curve under the holding condition, and the spatial node force vector of viscous adsorption under the pull-out condition. Based on the spatial node force vector, a spatial mesh model of a single-sided open and closed temporary casing is established for the upper and lower reinforcing cylinder ends and the middle standard cylinder. The sliding pin surface and the inner wall of the inverted V-shaped groove form a contact pair. The tooth surface interlocking depth of the positive and negative labyrinth slot is converted into the initial value of the penalty function contact stiffness, and the axial force transmission path of the tension rod flange end face is superimposed. On the radial degree of freedom of the middle standard cylinder of the single-sided open and closed temporary casing spatial mesh model, the buckling mode wavenumber under the load condition is locked. The peak stress region of vibration and impact under the indentation condition is associated with the axial degrees of freedom at the upper and lower reinforcing cylinder ends; a single-sided open and closed temporary casing space mesh model containing nodal force vectors, contact pair stiffness and degree of freedom constraints is output for loading calculation of three dynamic simulation conditions.

4. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 1, characterized in that, The process of outputting the entity manufacturing data sheet includes the following steps: The maximum stress value of the tangential shear stress concentration region of the labyrinth groove output from the simulation of the pressing condition, and the maximum axial tensile stress value of the tension rod flange region output from the simulation of the pull-out large deformation condition are read into the data buffer of the example iteration; the example iteration performs constraint judgment on each combination of parameter matrix in turn; the combination that meets the constraint judgment is retained, the rest are discarded, and the feasible parameter matrix is ​​output. For each set of wall thickness values ​​in the feasible parameter matrix, input them sequentially into the simulation results under the load condition. Extract the two extreme values ​​corresponding to each set of wall thicknesses. The two extreme values ​​are the maximum diameter reduction indentation of the central standard cylinder and the overall buckling critical load factor. Filter out all wall thickness values ​​where the diameter reduction indentation is less than the allowable deviation and the load factor is greater than the safety threshold. Select the minimum value from these as the optimal thickness of the central standard section. The example iterative program returns the optimal thickness to the feasible parameter matrix, determines the corresponding wall thickness values ​​of the upper and lower reinforcing cylinder ends, and outputs the optimal thickening ratio. The optimal thickness and best thickening ratio of the central standard section are written into the parameter locking area. The example iterative program sets the inclination angle of the inverted V-shaped groove relative to the axis of the casing as the only iteration variable, generating a discrete angle sequence from the lower limit angle to the upper limit angle. The example iterative program compares the maximum contact pressure value of the discrete angle sequence with the allowable compressive stress of the sliding pin material and eliminates all angles where the contact pressure exceeds the allowable value. Among the remaining inclination angles, the example iterative program extracts the angle corresponding to the minimum value of the tensile peak and outputs it as the optimal inclination angle parameter of the groove.

5. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 4, characterized in that, The example iteration sets the wall thickness of the central standard cylinder as the first iteration variable and the ratio of the wall thickness of the upper and lower reinforcing cylinder ends to the wall thickness of the central standard cylinder as the second iteration variable, generating a parameter matrix containing multiple combinations of wall thickness and ratio. The constraint judgment condition is that the maximum tangential shear stress does not exceed the material yield limit and the maximum axial tensile stress of the flange does not exceed the tensile strength limit.

6. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 4, characterized in that, The simulation comparison compares the maximum diameter reduction and indentation with the preset allowable deviation value of the inner diameter of the casing; at the same time, it compares the overall buckling critical load factor with the design safety threshold; and substitutes each tilt angle into the simulation results of the large deformation condition of the pull-out, and reads two output values ​​under the tilt angle: the maximum contact pressure value of the contact surface between the sliding pin and the inclined groove, and the peak value of the output tension of the jack.

7. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 4, characterized in that, The process of outputting the feasible parameter matrix includes the following steps: The simulation example will write the maximum stress value of the labyrinth groove tangential shear stress concentration area output by the indentation working condition simulation and the maximum axial tensile stress value of the tension rod flange area output by the pull-out large deformation working condition simulation into the first storage unit and the second storage unit of the data buffer, respectively. The wall thickness of the central standard cylinder is set as the first iteration variable, and the ratio of the wall thickness of the upper and lower reinforcing cylinder ends to the wall thickness of the central standard cylinder is set as the second iteration variable. A parameter matrix containing multiple combinations of wall thickness values ​​and ratio values ​​is generated and stored in the third storage unit of the data cache area. Read the wall thickness and ratio values ​​of each combination sequentially from the third storage unit of the data cache, and substitute the combination into the material yield strength and tensile strength values ​​for dual judgment; Traverse all combinations in the third storage unit of the data buffer, and sequentially read the corresponding reserved flags in the fourth storage unit; The combinations with the retention flag set to true are copied from the third storage unit to the fifth storage unit. After the copying is complete, the set of combinations in the fifth storage unit becomes the feasible parameter matrix.

8. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 7, characterized in that, The dual judgment includes: sending the maximum tangential shear stress value and the material yield strength value into the first comparison unit and outputting the first comparison flag; sending the maximum axial tensile stress value and the tensile strength limit value of the flange into the second comparison unit and outputting the second comparison flag; sending the first comparison flag and the second comparison flag into the logic AND operation unit to generate a combined retention flag, and storing the retention flag and the combination in the fourth storage unit of the data buffer.

9. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 4, characterized in that, The process of determining the corresponding upper and lower reinforcing cylinder end wall thickness values ​​includes the following steps: The numerical example iteratively compares the maximum diameter reduction indentation value with the pre-written allowable deviation value of the casing inner diameter; at the same time, it compares the overall buckling critical load factor value with the pre-written design safety threshold value. Retain all wall thickness values ​​where the diameter reduction indentation is less than the allowable deviation and the buckling load factor is greater than the safety threshold, discard the remaining wall thicknesses, and generate an intermediate value sequence consisting of wall thicknesses that meet the two conditions; extract the smallest value from the intermediate value sequence and output it as the optimal thickness of the central standard section. Search the feasible parameter matrix for wall thickness entries that match the optimal thickness value, and determine the wall thickness values ​​of the upper and lower reinforcing cylinder ends corresponding to the wall thickness entries; based on the locked upper and lower reinforcing cylinder end wall thickness values ​​and the optimal thickness value of the middle standard section, determine the magnification factor of the upper and lower reinforcing cylinder end wall thickness relative to the optimal thickness of the middle standard section, and output the magnification factor as the optimal thickness increase ratio.

10. The method for designing a single-sided open / closed temporary casing and constructing cast-in-place piles based on finite element analysis as described in claim 1, characterized in that, Manufacture the casing segments according to the optimized data in the physical manufacturing data sheet and splice them with high-strength bolts. Use jacks to lift the tension rod to force the sliding pin of the opening and closing plate to retract inward. After the casing is rigidly locked and closed, it is pressed into the soil by high-frequency vibration. Lower the optimized rotary drilling bit to advance the footage and build a closed-loop mud circulation system to maintain water head balance. After pouring concrete, determine the golden initial setting time point according to the setting performance test of cementitious materials. Release the tension rod in the reverse direction to make the sliding pin rise to the wide distance area of ​​the inclined groove. The casing slightly expands the diameter along the opening to decouple the ultimate frictional resistance and achieve low-damage pull-out and demolding.

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