Method for calculating settlement of squeezed branch pile in karst area by considering squeezing compaction effect

Abstract

The invention discloses a karst area extrusion and expansion branch pile settlement calculation method considering the extrusion and expansion compaction effect, and the method comprises the steps: calculating the self-weight stress, confining pressure and partial principal stress of a soil layer through on-site drilling coring, indoor soil test, triaxial compression test and single pile test, and obtaining a relation curve of the partial principal stress and axial strain; the method comprises the following steps: establishing a pile-soil three-dimensional model based on finite element software, respectively arranging extrusion and diffusion hard areas on the lower part and the periphery of a supporting disc, establishing analysis steps by combining a graded load sequence, calculating a soil body secant modulus between adjacent loads, endowing differentiated elastic modulus, and completing corresponding elastic modulus assignment and finite element calculation under each analysis step, extracting a pile top settlement value, comparing the pile top settlement value with a field test pile load-displacement curve, and substituting the pile top settlement value into engineering pile design parameters to estimate instantaneous and long-term settlement; the method can accurately quantify the squeezing and diffusion compaction effect, is adaptive to the complex stratum of the karst area, and has important guiding significance for further estimating the settlement of the engineering pile applied on a large scale subsequently.

Description

Technical Field

[0001] This invention belongs to the field of pile foundation engineering technology, and more specifically, relates to a method for calculating the settlement of karst zone expansion piles that takes into account the expansion and compaction effect. Background Technology

[0002] Since its introduction in the late 1980s, expanded-base pile technology has been widely used in many engineering fields, including high-rise buildings, industrial plants, power transmission lines, bridge engineering, and soft soil foundation treatment, due to its unique load-bearing advantages. However, because the load transfer mechanism of expanded-base piles is extremely complex, involving the interaction between the pile's lateral resistance and the end resistance of multiple support plates, the engineering community has not yet formed a unified, standardized, and universally applicable settlement calculation formula. Existing calculation methods all have significant defects and are difficult to meet the precise requirements of engineering design.

[0003] Existing methods for calculating the settlement of expanded and displaced pile foundations mainly fall into four categories: First, the equivalent pier foundation method. This method treats the pile and soil above the lowest support as a solid deep foundation, considering only the soil compression corresponding to the projected area of ​​the lowest support, completely ignoring the bearing capacity of the upper support. This results in overly conservative calculations, failing to fully realize the actual bearing potential of the pile foundation. Second, the equivalent friction pile method. This method equates the bearing capacity of the support to the increased side surface area of ​​the pile. However, its core difficulty lies in the lack of precise basis for determining the equivalent frictional resistance on the side of the support, making it difficult for existing technologies to obtain accurate results and leading to significant calculation errors. Third, the empirical analogy and field test method. The empirical analogy method is highly regional and relies on marine testing. The empirical formulas constructed from quantitative test data have limited applicability, while the field static load test, although reliable, suffers from high cost and long cycle, and can only be applied to extra-large projects or projects with extremely complex geological conditions. The fourth method is numerical simulation, which can take into account complex geometries, soil nonlinearity, and construction processes, and is the preferred solution for major projects or complex geological conditions. However, traditional numerical simulation often takes the elastic modulus of soil as a constant value, ignoring the nonlinear characteristics of the elastic modulus of soil with load during graded loading. At the same time, it does not consider the squeezing and compaction effect of the surrounding soil caused by the construction of the support plate, resulting in a significant deviation between the calculated settlement value and the field test pile results, making it difficult to effectively guide the design of engineering piles.

[0004] The geological conditions in karst areas are more complex. Uneven soil distribution and karst development can lead to complex load transfer paths, and the compaction effect caused by the construction of the bearing plate has a more significant impact on pile settlement. Existing methods are not optimized for the special geological conditions of karst areas, nor do they systematically consider the compaction effect and the nonlinear changes in the elastic modulus of the soil. This results in insufficient accuracy in settlement calculations, making it difficult to ensure the safety and rationality of engineering pile design in karst areas. Therefore, there is an urgent need for a settlement calculation method for expanded bearing plate piles that can accurately consider the compaction effect and is adapted to the geological conditions of karst areas. This would solve the technical problem of large deviations between the calculation results and actual engineering conditions in existing technologies, which cannot effectively guide design. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method for calculating the settlement of karst zone expanded support piles considering the expansion and compaction effect. First, through field core drilling, indoor geotechnical tests, triaxial compression tests, and single-pile tests, the stratum distribution, karst development state, soil physical and mechanical parameters, graded load-displacement curves, and the load shared by the support are obtained. The soil's self-weight stress, confining pressure, and deviatoric principal stress are calculated, and a deviatoric principal stress-axial strain relationship curve is constructed. Subsequently, a three-dimensional pile-soil model is established using finite element software. The bottom and side hardened zones of the support are set according to preset rules. An analysis step is created based on the graded load sequence to calculate the secant modulus of the soil between adjacent loads and assign differentiated elastic moduli (bottom hardened zone 2). Side hardening zone 1.5 Ordinary soil layer After verifying the effectiveness of the model by comparing the calculated curves with the field test pile curves, the instantaneous and long-term settlement is estimated by substituting the engineering pile design parameters. The system of this invention has four core modules: parameter acquisition and preprocessing, finite element model construction and parameter assignment, model verification, and engineering pile settlement estimation, which can realize full-process automation and intelligence. This invention can accurately quantify the squeezing and compaction effect, adapt to complex strata in karst areas, and the calculation results are consistent with the field test piles by less than 10%, with the error reduced by more than 30% compared with traditional methods. It can provide reliable technical support for the design optimization of squeezing and expanding support piles in karst areas and the safety of the structure throughout its entire life cycle.

[0006] To achieve the above objectives, one aspect of the present invention provides a method for calculating the settlement of expanded support piles in karst areas considering the expansion and compaction effect, comprising the following steps: S1: Conduct on-site drilling and core sampling, indoor geotechnical tests and single pile tests to obtain the stratum distribution, soil physical and mechanical parameters, graded load-displacement curves and load sharing of the support plate, calculate the soil self-weight stress, confining pressure and deviatoric principal stress, and obtain the relationship curve between deviatoric principal stress and axial strain through triaxial compression tests. S2: A three-dimensional model of the expanded support pile and the surrounding soil is established based on finite element software. Hardened zones are set at the bottom and sides of the support according to preset rules. Finite element analysis steps are created according to the graded load sequence of field test piles. The actual deviatoric principal stress of the soil at the support under each analysis step is calculated using the deviatoric principal stress-axial strain relationship curve. Based on the deviatoric principal stress and axial strain corresponding to two adjacent load levels on the deviatoric principal stress-axial strain relationship curve, the secant modulus of the soil between these two adjacent load levels is calculated. The differentiated elastic modulus of the ordinary soil layer, the bottom of the support, and the hardened zones on the sides is determined through back-analysis of a large amount of field test pile data. Simultaneously, the design elastic modulus is assigned to the pile body. S3: In each analysis step, the corresponding elastic modulus is assigned to the soil layer and the hardened zone, and then finite element calculation is performed. The settlement value at the top of the pile is extracted and compared with the load-displacement curve of the on-site test pile. The parameters are adjusted until the consistency meets the preset requirements to verify the effectiveness of the calculation model. S4: Using a proven and effective calculation model, the design parameters of the engineering pile are substituted to predict its normal service limit state and long-term settlement, providing a basis for the engineering design of the expansion and spur pile in the karst area.

[0007] Further, step S1 includes: S11: Conduct on-site drilling and core sampling to determine the stratum distribution and karst development within the pile body area. Simultaneously, carry out indoor geotechnical tests to determine the physical and mechanical parameters of each soil layer according to specifications. The physical and mechanical parameters include density, water content, void ratio, internal friction angle, and cohesion. S12: Calculate the self-weight stress of the soil layer above the center of each layer based on the density and depth of each layer; combine this with the internal friction angle of the soil layer. Determine the coefficient of earth pressure at rest, and then calculate the actual confining pressure at the center of each soil layer; S13: Using the actual confining pressure at the center of each soil layer as the confining pressure, conduct triaxial compression tests on each soil layer sample, apply axial loads in stages and record the corresponding axial strains, and construct the relationship curve between the deviatoric principal stress and axial strain. S14: Conduct on-site single-pile test piles with expanded support plates. Use the slow-speed sustained load method to obtain graded load-displacement curves. Measure the axial force distribution of the pile body under each load level using pile strain gauges to determine the vertical load shared by the support plate. Calculate the vertical stress of the soil at the bottom of the support plate based on the area of ​​the support plate. Obtain the deviatoric principal stress by subtracting the vertical stress of the soil at the bottom of the support plate from the actual confining pressure at the center of each soil layer.

[0008] Furthermore, in step S12, the actual confining pressure at the center of each soil layer... Calculated using formula (3): (3) in, This is the coefficient of earth pressure at rest; The vertical self-weight stress generated by all soil layers above the center of the target soil layer; Vertical stress of the soil at the bottom of the plate in step S13 Calculated using formula (4): (4) in, Vertical loads shared by the support plate; The area of ​​the support plate; Off-principal stress in step S13 Calculated using formula (5): (5).

[0009] Further, step S2 includes: S21: Based on finite element software, and according to the actual pile body size, support plate geometry and stratum distribution of the project, a three-dimensional solid model of the expanded support plate pile and the surrounding soil is established to accurately restore the spatial positional relationship between the pile and the soil. S22: In the 3D model, set a hardened area for the bottom of the support plate: create a surface with the outline of the vertical downward 1 times the length of the hypotenuse from the outer vertex of the hypotenuse at the bottom of the support plate to the vertex of the bottom of the support plate, and rotate it 360° to form a solid hardened area. S23: Set a hardening zone on the side of the support plate: Extend 1 times the height of the support plate upwards and downwards from the center height of the support plate, create an arc with a radius of 0.5 times the height of the support plate and an angle of 180°, merge them to form a surface, and rotate 360° to form a solid hardening zone. S24: Create a finite element analysis step according to the graded load sequence of the on-site test piles, and calculate the actual deviatoric principal stress of the soil at the support plate under each analysis step according to step S14, based on the deviatoric principal stress-axial strain relationship curve obtained in step S13. S25: On the aforementioned deviatoric principal stress-axial strain relationship curve, find the deviatoric principal stress and axial strain corresponding to two adjacent load levels, and calculate the secant modulus of the soil between the two adjacent load levels. S26: Based on the secant modulus of the soil between two adjacent load levels in step S25, assign differentiated elastic modulus to the soil region in the three-dimensional solid model of the expanded support pile and the surrounding soil: the elastic modulus of the hardened zone at the bottom of the support pile is 2. The elastic modulus of the hardened zone on the side of the support plate is 1.5. The elastic modulus of ordinary soil is The mechanical behavior of the pile is simulated using a "linear elastic constitutive model" and the elastic modulus parameters determined in the design stage are input.

[0010] Furthermore, the secant modulus of the soil between two adjacent load levels in step S25 is calculated using equation (6): (6) in, For the first Level and First Secant modulus of soil between load levels; For the first Under a level load, the deviatoric principal stress of the soil; For the first Under a level load, the deviatoric principal stress of the soil; No. The axial strain of the soil under a level load; For the first The axial strain of the soil under a certain load.

[0011] Further, step S3 includes: S31. For the graded load corresponding to the current analysis step, run the solver of the finite element software to calculate the stress and deformation response of the pile-soil system. S32. Extract the pile top settlement data from the finite element calculation results for the current analysis step; S33. Integrate the pile top settlement values ​​from all analysis steps, plot the numerical calculation "graded load-displacement curve", and compare it with the load-displacement curve obtained from the field single pile test in step S1. S34. If the relative error between the two curves is less than or equal to the preset requirement, the calculation model is confirmed to be valid. If the error exceeds the requirement, adjust the soil constitutive parameters or boundary conditions of the model and repeat steps S31-S33 until the consistency meets the requirements.

[0012] Further, step S4 includes: Substitute the design parameters of the extruded and expanded support piles in actual engineering into the verified and effective finite element calculation model; According to the engineering design requirements, the vertical load corresponding to the normal serviceability limit state is set, and the influence of long-term load is considered. Run the finite element solver to calculate the pile top settlement response of the engineering pile under the target load condition; The instantaneous settlement under normal serviceability limit state is extracted from the calculation results, and the long-term settlement of the engineering pile is calculated by combining the soil creep characteristics. The calculated instantaneous and long-term settlement results are compiled into a report and compared with the settlement limit requirements of the engineering design, providing a quantitative basis for optimizing the design parameters of pile length and support plate arrangement for karst area expansion piles.

[0013] The second aspect of the present invention provides a settlement calculation system for karst zone expanded and compacted piles that consider the expansion and compaction effect, used to implement the settlement calculation method for karst zone expanded and compacted piles that consider the expansion and compaction effect, including a parameter acquisition and preprocessing module, a finite element model construction and parameter assignment module, a model verification module, and an engineering pile settlement prediction module; The parameter acquisition and preprocessing module is used to carry out field drilling and core sampling, indoor geotechnical tests and single pile tests, to obtain the stratum distribution, soil physical and mechanical parameters, graded load-displacement curves and load sharing of the support plate, to calculate the soil self-weight stress, confining pressure and deviatoric principal stress, and to obtain the relationship curve between deviatoric principal stress and axial strain through triaxial compression tests. The finite element model construction and parameter assignment module is used to build a three-dimensional model of the expanded support pile and the surrounding soil based on finite element software. Hardened zones are set at the bottom and sides of the support according to preset rules. Finite element analysis steps are created according to the graded load sequence of field test piles. The actual deviatoric principal stress of the soil at the support under each analysis step is calculated using the deviatoric principal stress-axial strain relationship curve. Based on the deviatoric principal stress and axial strain corresponding to two adjacent load levels on the deviatoric principal stress-axial strain relationship curve, the secant modulus of the soil between the two adjacent load levels is calculated. The differentiated elastic modulus of the ordinary soil layer, the bottom of the support, and the hardened zones on the sides is determined through back-analysis of a large amount of field test pile data. Simultaneously, the design elastic modulus is assigned to the pile body. The model verification module is used to assign values ​​to the modulus of the soil layer and the compaction zone in each analysis step, perform finite element calculations, extract the pile top settlement value and compare it with the load-displacement curve of the on-site test pile, and adjust the parameters until the degree of agreement meets the preset requirements to verify the effectiveness of the calculation model. The engineering pile settlement prediction module is used to predict the normal service limit state and long-term settlement of engineering piles by using a verified and effective calculation model and substituting the design parameters of the engineering piles, providing a basis for the engineering design of extruded and expanded support piles in karst areas.

[0014] A third aspect of the present invention provides an electronic device including a processor and a memory interconnected thereto; The memory is used to store computer programs; The processor is configured to execute the settlement calculation method for karst zone expansion and compaction piles that takes into account the expansion and compaction effect when the computer program is invoked.

[0015] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program that is executed by a processor to implement the method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect.

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: (1) The present invention provides a method and system for calculating the settlement of karst zone expansion bearing piles considering the expansion and compaction effect. The calculation accuracy is high. Through back analysis of field single pile test data, the hardened zone at the bottom of the bearing (elastic modulus 2) is clearly defined. ) and the side hardened area (elastic modulus 1.5) The invention utilizes differentiated stiffness values ​​to overcome the limitations of traditional calculations that treat the soil around the pile as a homogeneous material and ignore the effect of expansion and compaction on soil stiffness. This allows the calculation model to accurately reproduce the compaction characteristics of the soil around the support plate caused by expansion and compaction. By quantifying the differentiated stiffness of the bottom / side hardened zone of the support plate and obtaining strata and stress-strain parameters based on field drilling and testing, this invention solves the problems of neglecting the expansion and compaction effect and poor adaptability of traditional methods. The settlement calculation error is reduced by more than 30% compared with traditional methods, and the field test pile curve verification shows a consistency of less than 10%. This invention can provide accurate data support for the settlement control of pile foundations in karst areas.

[0017] (2) The settlement calculation method and system for expanded and compacted piles in karst areas considering the expansion and compaction effect of the present invention first investigates the stratum distribution and karst development state within the pile body by drilling and core sampling in the field. Then, it calculates the soil self-weight stress and confining pressure based on actual stratum parameters, and obtains the stress-strain constitutive relationship that fits the characteristics of soil layers in karst areas by combining triaxial compression tests. This avoids the problem of traditional methods "using empirical stratum parameters and being unable to adapt to the heterogeneity of strata in karst areas". It can be widely applied to the settlement calculation of expanded and compacted piles in karst development areas with different soil layer combinations (such as clay layer, sand layer, and fractured rock layer), and the stratum adaptability is significantly improved.

[0018] (3) The settlement calculation method and system of karst area expansion support pile considering the expansion and compaction effect of the present invention is based on the measured data obtained by field drilling, indoor geotechnical test and single pile test. It forms a complete technical closed loop through finite element model construction, graded load analysis step creation and test pile curve comparison verification: first, the model parameters are determined by measured data, then the model is optimized by the consistency between the calculation results and the test pile data, and finally the settlement of the engineering pile is predicted by the verified model. It completely solves the drawback of traditional calculation "relying on theoretical assumptions and being out of touch with the actual situation on site". The calculation results can be directly used as the core basis for the design of the pile length and the optimization of the support layout of karst area expansion support pile, and the engineering guidance is stronger.

[0019] (4) The settlement calculation method and system of karst zone expansion bearing pile considering the expansion and compaction effect of the present invention, by considering the nonlinear change of the elastic modulus of the soil under different loads when calculating with finite element software, and setting expansion and compaction hardening zones at the bottom and around the bearing, and assigning values ​​to the elastic modulus of the hardened soil in the zone, can achieve the match between the numerical calculation results and the load-displacement curve of the field test pile, thereby verifying the rationality of the calculation method of the present invention. Using the method of the present invention, the settlement of engineering piles to be applied on a large scale in the future can be further predicted, which is of great significance for guiding the design of engineering piles.

[0020] (5) The settlement calculation method and system of the karst area expansion and compaction pile considering the squeezing and expansion compaction effect of the present invention not only calculates the instantaneous settlement under the normal service limit state in the settlement prediction stage of the engineering pile, but also calculates the long-term settlement in combination with the creep characteristics of the soil (such as Merchant creep constitutive model). It breaks through the limitation of the traditional method that "only focuses on instantaneous settlement and ignores the impact of long-term soil deformation on the safety of the pile foundation". It can accurately predict the settlement development trend of the karst area expansion and expansion pile under long-term load, avoid problems such as cracking of the superstructure and equipment displacement caused by excessive long-term settlement, and ensure the long-term safety and stability of the engineering structure.

[0021] (6) The settlement calculation method and system for karst expansion and compaction piles in the present invention, which considers the expansion and compaction effect, integrates the entire process of settlement calculation, including data acquisition, parameter calculation, model construction and result output, through the modular design of "parameter acquisition and preprocessing module - finite element model construction and parameter assignment module - model verification module - engineering pile settlement prediction module". The modules automatically transmit data through standardized data interfaces (such as the stress parameters output by the parameter acquisition module are directly imported into the model construction module without manual secondary input), which greatly reduces the manual operation links. The calculation efficiency is more than 60% higher than the traditional "distributed software operation and manual data conversion" method. It also supports visual parameter input and automatic generation of calculation reports, reducing the dependence on the professional skills of operators and making it more practical for engineering. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating a method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect, according to an embodiment of the present invention. Figure 2 This is a schematic diagram illustrating the calculation process of a method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect, according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the relationship between the deviatoric principal stress and axial strain in an embodiment of the present invention, which considers the squeezing and compaction effect of a karst zone squeezed and expanded support pile. Figure 4 This is a schematic diagram of a three-dimensional model of a karst-area slab pile, which is a method for calculating the settlement of slab piles with expansion and compaction effects in karst areas according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the hardened zone at the bottom of the support plate of a pile with an expanded support plate, which is part of an embodiment of the present invention for calculating the settlement of piles with expanded support plates in karst areas, taking into account the expansion and compaction effect. Figure 6 This is a schematic diagram of the hardened zone on the side of the expanded bearing pile, which is part of an embodiment of the present invention, for calculating the settlement of expanded bearing piles in karst areas considering the expansion and compaction effect. Figure 7This is a schematic diagram of the secant modulus of the soil between two adjacent load levels in a method for calculating the settlement of karst zone expansion and compaction piles considering the expansion and compaction effect, according to an embodiment of the present invention. Figure 8 This is a schematic diagram comparing the measured and numerical calculation results of pile top settlement values ​​under field test piles, without considering soil compaction, and with considering soil compaction in a method for calculating the settlement of expanded support piles in karst areas, which considers the expansion and compaction effect, according to an embodiment of the present invention. Figure 9 This is a schematic diagram of a settlement calculation system for karst zone expansion and compaction piles considering the expansion and compaction effect, according to an embodiment of the present invention. Figure 10 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] like Figure 1 and Figure 2 As shown, one aspect of the present invention provides a method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect, comprising the following steps: S1: Conduct on-site drilling and core sampling, indoor geotechnical tests and single pile tests to obtain the stratum distribution, soil physical and mechanical parameters, graded load-displacement curves and load sharing of the support plate, calculate the soil self-weight stress, confining pressure and deviatoric principal stress, and obtain the relationship curve between deviatoric principal stress and axial strain through triaxial compression tests. S2: A three-dimensional model of the expanded support pile and the surrounding soil is established based on finite element software. Hardened zones are set at the bottom and sides of the support according to preset rules. Finite element analysis steps are created according to the graded load sequence of the field test piles. The actual deviatoric principal stress of the soil at the support pile under each analysis step is calculated using the deviatoric principal stress-axial strain relationship curve. Based on the deviatoric principal stress and axial strain corresponding to two adjacent load levels on the deviatoric principal stress-axial strain relationship curve, the secant modulus of the soil between the two adjacent load levels is calculated. The differentiated elastic modulus of the ordinary soil layer, the bottom of the support pile, and the hardened zones on the sides are determined through back-analysis of a large amount of field test pile data (i.e., deriving reasonable values ​​for soil parameters based on the actual settlement of the test piles). Simultaneously, the design elastic modulus is assigned to the pile body. S3: In each analysis step, the corresponding elastic modulus is assigned to the soil layer and the hardened zone, and then finite element calculation is performed. The settlement value at the top of the pile is extracted and compared with the load-displacement curve of the on-site test pile. The parameters are adjusted until the consistency meets the preset requirements to verify the effectiveness of the calculation model. S4: Using a proven and effective calculation model, the design parameters of the engineering pile are substituted to predict its normal service limit state and long-term settlement, providing a basis for the engineering design of the expansion and spur pile in the karst area; Further, step S1 includes: S11: Conduct on-site drilling and core sampling to determine the stratum distribution and karst development within the pile body area. Simultaneously, carry out indoor geotechnical tests and determine the physical and mechanical parameters of each soil layer according to the specifications. The physical and mechanical parameters include, but are not limited to, density, water content, void ratio, internal friction angle and cohesion. S12: Based on the density and depth of each soil layer, calculate the self-weight stress of the soil layer above the center of each soil layer to determine the vertical reference stress; combine the internal friction angle of the soil layer to determine the static earth pressure coefficient, and then calculate the actual confining pressure at the center of each soil layer. S13: Using the actual confining pressure at the center of each soil layer as the confining pressure, conduct triaxial compression tests on each soil layer sample, apply axial loads in stages, and record the corresponding axial strains. Construct the relationship curve between the partial principal stress and the axial strain (e.g.) Figure 3 (as shown) S14: Conduct on-site single-pile test piles with expanded support plates, use the slow-speed sustained load method to obtain graded load-displacement curves, measure the axial force distribution of the pile body under each load level using pile strain gauges to determine the vertical load shared by the support plate, calculate the vertical stress of the soil at the bottom of the support plate in combination with the area of ​​the support plate, and obtain the deviatoric principal stress by subtracting the vertical stress of the soil at the bottom of the support plate from the actual confining pressure at the center of each soil layer. Furthermore, in step S12, the self-weight stress of the soil layer above the center of each soil layer... The expression is: (1) in, The vertical self-weight stress generated by all soil layers above the center of the target soil layer; For the first The natural density of the soil layers; It is the acceleration due to gravity; For the first The thickness of the soil layer, and the summation range is all soil layers from the ground surface to the plane above the center of the target soil layer; The summation symbol represents the accumulation of the self-weight stress of each soil layer above the center of the target soil layer; coefficient of earth pressure at rest in step S12 Calculate using formula (2) (2) in, The internal friction angle of the soil layer; The actual confining pressure at the center of each soil layer in step S12 Calculated using formula (3): (3) Vertical stress of the soil at the bottom of the plate in step S13 Calculated using formula (4): (4) in, Vertical loads shared by the support plate; The area of ​​the support plate; Off-principal stress in step S13 Calculated using formula (5): (5); Further, step S2 includes: S21: Based on finite element software (such as ABAQUS, ANSYS, etc.), and according to the actual pile dimensions, support geometry (diameter, height, hypotenuse length, etc.), and soil strata distribution, establish a three-dimensional solid model of the expanded support pile and the surrounding soil (e.g., ...). Figure 4 As shown in the figure, the spatial relationship between the pile and the soil is accurately restored; S22: In the 3D model, set a hardened area for the bottom of the support plate: Create a surface with the outline of a vertical downward section of 1 times the length of the hypotenuse from the outer vertex of the hypotenuse's bottom edge to the vertex of the bottom edge of the support plate, and rotate it 360° to form the hardened area solid (e.g., Figure 5 (as shown) S23: For the side of the support plate, create a hardened area: Extend upwards and downwards by one time the support plate height from the center height, creating arcs with a radius of 0.5 times the support plate height and an angle of 180°. Merge these arcs to form a surface, then rotate 360° to form the solid hardened area (e.g., ...). Figure 6 (as shown) S24: Create a finite element analysis step according to the graded load sequence of the field test piles. Combining the deviatoric principal stress-axial strain relationship curve obtained in step S13, calculate the actual deviatoric principal stress of the soil at the support plate under each analysis step (corresponding to each load level) according to step S14. ； S25: On the aforementioned partial principal stress-axial strain relationship curve, find the partial principal stress and axial strain corresponding to two adjacent load levels, and calculate the secant modulus of the soil between these two adjacent load levels (e.g., ...). Figure 7 (as shown) S26: Based on the secant modulus of the soil between two adjacent load levels in step S25, assign differentiated elastic modulus to the soil region in the three-dimensional solid model of the expanded support pile and the surrounding soil: the elastic modulus of the hardened zone at the bottom of the support pile is 2. The elastic modulus of the hardened zone on the side of the support plate is 1.5. The elastic modulus of ordinary soil is The mechanical behavior of the pile is simulated using a "linear elastic constitutive model", and the elastic modulus parameters determined in the design stage are input. Furthermore, the secant modulus of the soil between two adjacent load levels in step S25 is calculated using equation (6): (6) in, For the first Level and First Secant modulus of soil between load levels; For the first Under a level load, the deviatoric principal stress of the soil; For the first Under a level load, the deviatoric principal stress of the soil; For the first The axial strain (dimensionless) of the soil under the load level is calculated by the ratio of the axial deformation of the soil under the load level to the initial height. For the first Axial strain (dimensionless) of soil under level load. Further, step S3 includes: S31. Finite element calculation execution: For the graded load corresponding to the current analysis step, run the solver of the finite element software to calculate the stress and deformation response of the pile-soil system. S32. Pile top settlement value extraction: Extract the pile top settlement data of the current analysis step from the finite element calculation results; S33. Curve Comparison and Verification: Integrate the pile top settlement values ​​from all analysis steps, plot the numerically calculated "graded load-displacement curve," and compare it with the load-displacement curve obtained from the on-site single-pile test in step S1 (e.g., ...). Figure 8 (as shown) S34. Matching Determination and Parameter Adjustment: If the relative error between the two curves is less than or equal to the preset requirement (usually 10%), the calculation model is confirmed to be effective. If the error exceeds the requirement, adjust the soil constitutive parameters (such as the modulus multiple of the hardened zone and the Poisson's ratio of the soil) or boundary conditions of the model, and repeat steps S31-S33 until the matching degree meets the requirements.

[0025] Figure 8This is a comparison of the load-settlement curves for expanded and displaced piles. The horizontal axis represents the vertical load applied to the pile top, and the vertical axis represents the settlement deformation at the pile top under the corresponding load. The curves show that the calculation curve considering soil compaction closely matches the results of field pile tests (small difference in settlement). Conversely, the calculation curve without considering soil compaction shows a settlement much larger than the results of field pile tests (larger error). This directly verifies the rationality of considering the expansion and compaction effect in this invention; it significantly improves the accuracy of settlement calculations and better reflects actual engineering conditions. Further, step S4 includes: Substitute the design parameters of the extruded and expanded support piles in actual engineering (including pile diameter / length, number / size of support plates, elastic modulus of pile material, target load conditions, etc.) into the verified and effective finite element calculation model; According to the engineering design requirements, set the vertical load corresponding to the normal serviceability limit state (such as the standard value of the design load), and consider the influence of long-term load action (such as the attenuation characteristics of the load over a long period of time). Run the finite element solver to calculate the pile top settlement response of the engineering pile under the target load condition; The instantaneous settlement under normal serviceability limit state is extracted from the calculation results. At the same time, the long-term settlement of the engineering pile is calculated by combining the soil creep characteristics (if the model includes long-term deformation constitutive model). The calculated instantaneous settlement and long-term settlement results are compiled into a report and compared with the settlement limit requirements of the engineering design to provide a quantitative basis for optimizing the design parameters such as pile length and support layout of the extrusion support pile in karst area.

[0026] The estimated results provide a scientific basis for engineering design, guiding the rational design and construction of engineering piles. By accurately predicting pile foundation settlement, engineering accidents caused by excessive pile foundation settlement can be effectively avoided, ensuring the safety and stability of the project.

[0027] The settlement calculation method of this invention first obtains data such as stratum distribution, soil physical and mechanical parameters, graded load-displacement curves, and load-sharing of the support plate through field drilling core sampling, indoor geotechnical tests, triaxial compression tests, and single pile tests. It then calculates the soil's self-weight stress, confining pressure, and deviatoric principal stress, and obtains the relationship curve between deviatoric principal stress and axial strain. Next, it establishes a three-dimensional pile-soil model based on finite element software, sets up hardened zones at the bottom and sides of the support plate, creates analysis steps according to the graded load sequence of the field pile tests, and calculates the actual deviatoric principal stress of the soil at the support plate under each analysis step based on the aforementioned relationship curves. The soil secant modulus between two adjacent load levels was determined by back-analysis of field test pile data, and the differentiated elastic modulus of ordinary soil layers and hardened zones was determined, and the design elastic modulus was assigned to the pile body. Subsequently, the corresponding elastic modulus was assigned and finite element calculations were completed in each analysis step. The pile top settlement value was extracted and compared with the load-displacement curve of the field test pile. The parameters were adjusted to meet the preset requirements to verify the effectiveness of the model. Finally, the effective model was used to substitute the engineering pile design parameters to predict its normal service limit state and long-term settlement, which can provide a basis for the design of karst area expansion and support pile engineering.

[0028] like Figure 9 As shown, the second aspect of the present invention provides a settlement calculation system for karst zone expansion and compaction piles that consider the expansion and compaction effect, including a parameter acquisition and preprocessing module, a finite element model construction and parameter assignment module, a model verification module, and an engineering pile settlement prediction module. The parameter acquisition and preprocessing module is used to carry out field drilling and core sampling, indoor geotechnical tests and single pile tests, to obtain the stratum distribution, soil physical and mechanical parameters, graded load-displacement curves and load sharing of the support plate, to calculate the soil self-weight stress, confining pressure and deviatoric principal stress, and to obtain the relationship curve between deviatoric principal stress and axial strain through triaxial compression tests. The finite element model construction and parameter assignment module is used to build a three-dimensional model of the expanded support pile and the surrounding soil based on finite element software. Hardened zones are set at the bottom and sides of the support according to preset rules. Finite element analysis steps are created according to the graded load sequence of field test piles. The actual deviatoric principal stress of the soil at the support under each analysis step is calculated using the deviatoric principal stress-axial strain relationship curve. Based on the deviatoric principal stress and axial strain corresponding to two adjacent load levels on the deviatoric principal stress-axial strain relationship curve, the secant modulus of the soil between the two adjacent load levels is calculated. The differentiated elastic modulus of the ordinary soil layer, the bottom of the support, and the hardened zones on the sides is determined through back-analysis of a large amount of field test pile data. Simultaneously, the design elastic modulus is assigned to the pile body. The model verification module is used to assign values ​​to the modulus of the soil layer and the compaction zone in each analysis step, perform finite element calculations, extract the pile top settlement value and compare it with the load-displacement curve of the on-site test pile, and adjust the parameters until the degree of agreement meets the preset requirements to verify the effectiveness of the calculation model. The engineering pile settlement prediction module is used to predict the normal service limit state and long-term settlement of engineering piles by using a verified and effective calculation model and substituting the design parameters of the engineering piles, providing a basis for the engineering design of extruded and expanded support piles in karst areas.

[0029] Furthermore, the parameter acquisition and preprocessing module includes a geological and geotechnical parameter acquisition unit, a stress calculation unit, a triaxial test data processing unit, and a single pile test data acquisition unit. The geological and geotechnical parameter acquisition unit is used to perform on-site drilling and core sampling operations, collect stratum distribution data and karst development status information within the pile body area, and simultaneously connect to indoor geotechnical testing equipment to determine the physical and mechanical parameters of each soil layer (density, water content, void ratio, internal friction angle, cohesion, etc.), and standardize and store the parameters to form a stratum distribution table and a soil layer physical and mechanical parameter database. The stress calculation unit is used to calculate the self-weight stress above the center of each soil layer based on the soil layer density and thickness output by the geological and geotechnical parameter acquisition unit, by calling formula (1); combined with the internal friction angle, the static earth pressure coefficient is calculated by formula (2), and then the actual confining pressure at the center of each soil layer is obtained according to formula (3), and a stress calculation report is generated; the self-weight stress, static earth pressure coefficient, and actual confining pressure list of each soil layer are output. The triaxial test data processing unit receives test data (axial deformation corresponding to confining pressure and graded axial loads) transmitted from the indoor triaxial compression testing equipment and converts the axial deformation into axial strain. ( =Axial deformation / Initial height of the specimen), combined with formula (5) to calculate the deviatoric principal stress, and finally draw and store the deviatoric principal stress-axial strain relationship curves of each soil layer; The single pile test data acquisition unit is used to connect with the on-site single pile static load test system (such as the JYC-5000 static load test system), and uses the slow sustained load method to acquire graded load-displacement curves; through the monitoring data of the pile strain gauge, the axial force distribution of the pile under each load level is analyzed to determine the vertical load shared by the support plate; combined with the area of ​​the support plate, the vertical stress of the soil at the bottom of the plate is calculated by formula (4), and the actual deviatoric stress at the support plate is obtained by formula (5), generating a test pile data report; outputting graded load-displacement curves, pile axial force distribution table, vertical load shared by the support plate, vertical stress of the soil at the bottom of the plate, and actual deviatoric stress at the support plate; Furthermore, the finite element model construction and parameter assignment module includes a three-dimensional geometric modeling unit, a hardening zone creation unit, an analysis step and modulus calculation unit, and a material parameter assignment unit; The 3D geometric modeling unit is used based on the API interface of finite element software to receive engineering design parameters (pile diameter / length, number / diameter / height / hypotenuse length, and stratum distribution range) and automatically generate a 3D solid model of the expanded support pile (pile body + support) and the surrounding soil. The soil model range is set to more than 5 times the pile size to eliminate boundary effects and accurately restore the spatial positional relationship between the pile and the soil. The hardening zone creation unit is used to automatically create hardening zones in the 3D model according to preset rules, generate hardening zone geometric identification files, associate them with the 3D geometric model, and output the hardening zone geometric model and the association mapping table between the hardening zone and the pile-soil model. Among them, the bottom hardening zone of the support plate: a surface is generated with the outline of the bottom edge of the support plate extending vertically downward from the outer vertex to the bottom vertex by 1 times the length of the hypotenuse, and then rotated 360° to form a solid; the side hardening zone of the support plate: an arc is created by extending upward and downward from the center height of the support plate by 1 times the height of the support plate, with a radius of 0.5 times the height of the support plate and an angle of 180°, and then merged to form a surface and rotated 360° to form a solid; The analysis step and modulus calculation unit are used to automatically create the corresponding finite element analysis step in the finite element software based on the graded load sequence output by the single pile test data acquisition unit; combined with the "deviatoric principal stress-axial strain relationship curve" of the triaxial test data processing unit and the deviatoric principal stress at the support plate of the single pile test, the deviatoric principal stress value corresponding to each analysis step is determined; the formula (6) is called to calculate the secant modulus between two adjacent load levels and generate the modulus calculation list; The material parameter assignment unit receives the secant modulus from the analysis step and the modulus calculation unit, and assigns elastic modulus to each region of the 3D model according to rules: assignment of ordinary soil layers. 2. The bottom hardening zone of the support plate is assigned a value of 2. The side hardening zone of the support plate is assigned a value of 1.5. Simultaneously, configure a linear elastic constitutive model for the pile body, input the design elastic modulus (e.g., 30 GPa for C30 concrete), generate a material parameter assignment report and associate it with the finite element model; output a material parameter assignment table and a finite element calculation model file containing parameters; Furthermore, the model verification module includes a finite element calculation execution unit, a curve comparison and consistency judgment unit, and a parameter optimization and adjustment unit. The finite element calculation execution unit is used to call the finite element software solver, automatically execute the stress and deformation calculation of the pile-soil system under each graded load according to the analysis step sequence, monitor the calculation process in real time (such as convergence and calculation error), and generate a calculation log. After the calculation is completed, the pile top settlement value corresponding to each analysis step is automatically extracted and stored as a settlement data list. The curve comparison and consistency judgment unit integrates the pile top settlement value output by the finite element calculation execution unit with the "graded load-displacement curve" of the single pile test data acquisition unit to generate a numerically calculated "graded load-displacement curve". The relative error formula (relative error = |calculated value - test value| / test value × 100%) is used to compare the two curves to determine whether they meet the preset consistency requirements (usually ≤10%). If they meet the requirements, a model validity verification report is generated; if they do not meet the requirements, the error analysis results are output and parameter adjustment prompts are triggered. The parameter optimization and adjustment unit is used to receive the error analysis results of the curve comparison and consistency judgment unit when the consistency does not meet the requirements, and automatically recommends adjustable parameters (such as the modulus multiple of the hardened zone, the Poisson's ratio of the soil, and boundary constraint conditions). Users can manually input the adjustment parameters or select the "automatic optimization" mode. The system will iteratively execute the "parameter adjustment - finite element calculation - curve comparison" process until the consistency meets the requirements and generate a parameter optimization report. Furthermore, the engineering pile settlement prediction module includes an engineering pile parameter input unit, a settlement calculation execution unit, and a design basis output unit; the engineering pile parameter input unit is used to provide a visual input interface, supporting users to enter actual engineering pile design parameters (pile body size, support plate arrangement, pile body material, target load conditions (such as standard value of design load), long-term load characteristics (such as load attenuation coefficient)), or import CAD / BIM design files to automatically parse parameters and generate an engineering pile parameter list; The settlement calculation execution unit is used to automatically substitute the parameters of the engineering pile parameter input unit into the verified and effective finite element model, configure the normal service limit state load and long-term load conditions; call the finite element solver to perform settlement calculation and extract instantaneous settlement values; if the model contains soil creep constitutive structure (such as Merchant model), it calculates the long-term settlement in combination with long-term load characteristics and generates a settlement calculation result table. The design basis output unit is used to compare the results of the settlement calculation execution unit with the engineering design settlement limit to analyze whether the settlement of the engineering piles meets the design requirements; it generates an engineering pile settlement prediction report containing "calculation parameters, settlement results, limit comparison, and optimization suggestions (such as adjusting pile length / number of support plates)", and supports export to PDF / Excel format, providing a quantitative basis for the design of extruded support plate piles in karst areas.

[0030] The parameter acquisition and preprocessing module of this invention can be directly connected to field drilling equipment, indoor geotechnical testing systems, and single pile static load testing equipment to realize the automatic acquisition and storage of stratum data, geotechnical parameters, and test pile data. At the same time, it automatically completes stress calculation, strain calculation, and deviatoric principal stress calculation through built-in algorithms, completely avoiding the reading errors and calculation errors that are prone to occur in the traditional process of "manually recording data and manually calculating parameters". The data processing accuracy is significantly improved, providing high-quality basic data for subsequent model construction and settlement calculation.

[0031] The model verification module of this invention has the functions of "automatic curve comparison, consistency judgment, and parameter optimization": it can automatically generate a comparison chart between the finite element calculation curve and the field test pile curve, and determine the validity of the model based on a preset threshold (such as relative error ≤10%); when the error exceeds the limit, it automatically analyzes the source of error and recommends adjustable parameters (such as the modulus multiple of the hardened zone and the Poisson's ratio of the soil), supports the "automatic iterative optimization" mode, eliminates the need for repeated manual adjustment of model parameters, greatly shortens the model verification cycle, and ensures that the output engineering pile settlement prediction results are always based on the effective model, resulting in higher calculation reliability.

[0032] The finite element model construction and parameter assignment module of this invention supports integration with mainstream finite element software such as ABAQUS, ANSYS, and MidasGTSNX (achieving model file format compatibility through API interfaces). It is also compatible with drilling equipment (such as XY-100 and XY-200 models), geotechnical testing equipment (such as TSZ-6A and GDS triaxial apparatus), and single pile static load testing equipment (such as JYC-5000 and YJW-10000 models) from different brands. This completely solves the problems of "poor software compatibility and incompatible equipment interfaces" in traditional calculation systems, meets the equipment configuration needs of different engineering teams, and has a wider range of applications.

[0033] The engineering pile settlement prediction module of this invention can automatically generate a standardized settlement prediction report containing "calculation parameters, settlement results, limit comparison, and optimization suggestions". The report format complies with industry standards such as the "Technical Specification for Building Pile Foundations" (JGJ94-2008) and the "Technical Specification for Building Foundations in Karst Areas" (JGJ258-2011). It supports exporting to PDF, Excel, and CAD compatible formats and can be directly used in the design briefing, construction drawing review, and project acceptance of extruded and expanded support piles in karst areas. It can provide compliant technical documents for the entire project process and reduce the workload of subsequent result processing.

[0034] It should be noted that the settlement calculation system for karst zone expansion and compaction piles considering the expansion and compaction effect provided in this embodiment can be a computer program (including program code) running on a computer device. For example, the settlement calculation system for karst zone expansion and compaction piles considering the expansion and compaction effect is an application software. The settlement calculation system for karst zone expansion and compaction piles considering the expansion and compaction effect can be used to execute the corresponding steps in the above-mentioned method provided in the embodiments of this application.

[0035] In some feasible implementations, the settlement calculation system for karst area expansion and compaction piles considering the expansion and compaction effect provided in this embodiment can be implemented using a combination of hardware and software. As an example, the settlement calculation system for karst area expansion and compaction piles considering the expansion and compaction effect provided in this application embodiment can be a processor in the form of a hardware decoding processor, which is programmed to execute the settlement calculation method for karst area expansion and compaction piles considering the expansion and compaction effect provided in this application embodiment. For example, the processor in the form of a hardware decoding processor can adopt one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), or other electronic components.

[0036] In some feasible implementations, the settlement calculation system for karst zone expansion and compaction piles considering the expansion and compaction effect provided in this embodiment can be implemented in software. It can be software in the form of programs and plug-ins, and includes a series of modules to implement the settlement calculation method for karst zone expansion and compaction piles considering the expansion and compaction effect provided in this embodiment of the invention.

[0037] A third aspect of the present invention also provides an electronic device, Figure 4 This is a schematic diagram of the electronic device in this embodiment, as shown below. Figure 10 As shown, the electronic device 1000 in this embodiment may include: a processor 1001, a network interface 1004, and a memory 1005. Furthermore, the electronic device 1000 may also include: a user interface 1003, and at least one communication bus 1002. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen and a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be high-speed RAM or non-volatile memory, such as at least one disk storage device. Optionally, the memory 1005 may also be at least one storage device located remotely from the aforementioned processor 1001. Figure 10As shown, the memory 1005, which is a computer-readable storage medium, may include an operating system, a network communication module, a user interface module, and a device control application.

[0038] like Figure 10 In the electronic device 1000 shown, the network interface 1004 provides network communication functions; the user interface 1003 is mainly used to provide an input interface for users; and the processor 1001 can be used to call the device control application stored in the memory 1005 to implement the above-mentioned optimization method.

[0039] It should be understood that in some feasible implementations, the processor 1001 described above may be a central processing unit (CPU), which may also be other general-purpose processors, DSPs, ASICs, FPGAs, or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor. The memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of the memory may also include non-volatile random access memory. For example, the memory may also store device type information.

[0040] In specific implementation, the aforementioned electronic device 1000 can perform the above-described actions through its built-in functional modules. Figure 1 The implementation methods provided for each step are detailed in the above-mentioned implementation methods, and will not be repeated here.

[0041] This application also provides a computer-readable storage medium storing a computer program that is executed by a processor to implement... Figure 1 The methods provided in each step are detailed in the implementation methods provided in the above steps, and will not be repeated here.

[0042] Any references to memory, storage, database, or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM), etc.

[0043] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating the settlement of expanded and compacted piles in karst areas, considering the expansion and compaction effect, characterized in that... Includes the following steps: S1: Conduct on-site drilling and core sampling, indoor geotechnical tests and single pile tests to obtain the stratum distribution, soil physical and mechanical parameters, graded load-displacement curves and load sharing of the support plate, calculate the soil self-weight stress, confining pressure and deviatoric principal stress, and obtain the relationship curve between deviatoric principal stress and axial strain through triaxial compression tests. S2: A three-dimensional model of the expanded support pile and the surrounding soil is established based on finite element software. Hardened zones are set at the bottom and sides of the support according to preset rules. Finite element analysis steps are created according to the graded load sequence of field test piles. The actual deviatoric principal stress of the soil at the support under each analysis step is calculated using the deviatoric principal stress-axial strain relationship curve. Based on the deviatoric principal stress and axial strain corresponding to two adjacent load levels on the deviatoric principal stress-axial strain relationship curve, the secant modulus of the soil between these two adjacent load levels is calculated. The differentiated elastic modulus of the ordinary soil layer, the bottom of the support, and the hardened zones on the sides is determined through back-analysis of a large amount of field test pile data. Simultaneously, the design elastic modulus is assigned to the pile body. S3: In each analysis step, the corresponding elastic modulus is assigned to the soil layer and the hardened zone, and then finite element calculation is performed. The settlement value at the top of the pile is extracted and compared with the load-displacement curve of the on-site test pile. The parameters are adjusted until the consistency meets the preset requirements to verify the effectiveness of the calculation model. S4: Using a proven and effective calculation model, the design parameters of the engineering pile are substituted to predict its normal service limit state and long-term settlement, providing a basis for the engineering design of the expansion and spur pile in the karst area.

2. The method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect according to claim 1, characterized in that, Step S1 includes: S11: Conduct on-site drilling and core sampling to determine the stratum distribution and karst development within the pile body area. Simultaneously, carry out indoor geotechnical tests and determine the physical and mechanical parameters of each soil layer according to the specifications. The physical and mechanical parameters include density, water content, void ratio, internal friction angle, and cohesion. S12: Calculate the self-weight stress of the soil layer above the center of each soil layer based on the density and depth of each soil layer; determine the static earth pressure coefficient by combining the internal friction angle of the soil layer, and then calculate the actual confining pressure at the center of each soil layer. S13: Using the actual confining pressure at the center of each soil layer as the confining pressure, conduct triaxial compression tests on each soil layer sample, apply axial loads in stages and record the corresponding axial strains, and construct the relationship curve between the deviatoric principal stress and axial strain. S14: Conduct on-site single-pile test piles with expanded support plates. Use the slow-speed sustained load method to obtain graded load-displacement curves. Measure the axial force distribution of the pile body under each load level using pile strain gauges to determine the vertical load shared by the support plate. Calculate the vertical stress of the soil at the bottom of the support plate based on the area of ​​the support plate. Oblique principal stress is obtained by subtracting the vertical stress of the soil at the bottom of the support plate from the actual confining pressure at the center of each soil layer.

3. The method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect according to claim 2, characterized in that, The actual confining pressure at the center of each soil layer in step S12 Calculated using formula (3): (3) in, This is the coefficient of earth pressure at rest; The vertical self-weight stress generated by all soil layers above the center of the target soil layer; Vertical stress of the soil at the bottom of the plate in step S13 Calculated using formula (4): (4) in, Vertical loads shared by the support plate; The area of ​​the support plate; Off-principal stress in step S13 Calculated using formula (5): (5).

4. The method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect according to claim 3, characterized in that, Step S2 includes: S21: Based on finite element software, and according to the actual pile body size, support plate geometry and stratum distribution of the project, a three-dimensional solid model of the expanded support plate pile and the surrounding soil is established to accurately restore the spatial positional relationship between the pile and the soil. S22: In the 3D model, set a hardened area for the bottom of the support plate: create a surface with the outline of the vertical downward 1 times the length of the hypotenuse from the outer vertex of the hypotenuse at the bottom of the support plate to the vertex of the bottom of the support plate, and rotate it 360° to form a solid hardened area. S23: Set a hardening zone on the side of the support plate: Extend 1 times the height of the support plate upwards and downwards from the center height of the support plate, create an arc with a radius of 0.5 times the height of the support plate and an angle of 180°, merge them to form a surface, and rotate 360° to form a solid hardening zone. S24: Create a finite element analysis step according to the graded load sequence of the on-site test piles, and calculate the actual deviatoric principal stress of the soil at the support plate under each analysis step according to step S14, based on the deviatoric principal stress-axial strain relationship curve obtained in step S13. S25: On the aforementioned deviatoric principal stress-axial strain relationship curve, find the deviatoric principal stress and axial strain corresponding to two adjacent load levels, and calculate the secant modulus of the soil between the two adjacent load levels. S26: Based on the secant modulus of the soil between two adjacent load levels in step S25, assign differentiated elastic modulus to the soil region in the three-dimensional solid model of the expanded support pile and the surrounding soil: the elastic modulus of the hardened zone at the bottom of the support pile is 2. The elastic modulus of the hardened zone on the side of the support plate is 1.

5. The elastic modulus of ordinary soil is The mechanical behavior of the pile is simulated using a "linear elastic constitutive model" and the elastic modulus parameters determined in the design stage are input.

5. The method for calculating the settlement of karst zone expansion and compaction piles considering the expansion and compaction effect, as described in claim 4, is characterized in that... In step S25, the secant modulus of the soil between two adjacent load levels is calculated using equation (6): （6） in, For the first Level and First Secant modulus of soil between load levels; For the first Under a level load, the deviatoric principal stress of the soil; For the first Under a level load, the deviatoric principal stress of the soil; No. The axial strain of the soil under a level load; For the first The axial strain of the soil under a certain load.

6. A method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect according to any one of claims 1-5, characterized in that, Step S3 includes: S31. For the graded load corresponding to the current analysis step, run the solver of the finite element software to calculate the stress and deformation response of the pile-soil system. S32. Extract the pile top settlement data from the finite element calculation results for the current analysis step; S33. Integrate the pile top settlement values ​​from all analysis steps, plot the numerical calculation "graded load-displacement curve", and compare it with the load-displacement curve obtained from the field single pile test in step S1. S34. If the relative error between the two curves is less than or equal to the preset requirement, the calculation model is confirmed to be valid. If the error exceeds the requirement, adjust the soil constitutive parameters or boundary conditions of the model and repeat steps S31-S33 until the consistency meets the requirements.

7. A method for calculating the settlement of karst zone expansion piles considering the expansion and compaction effect according to any one of claims 1-5, characterized in that, Step S4 includes: Substitute the design parameters of the extruded and expanded support piles in actual engineering into the verified and effective finite element calculation model; According to the engineering design requirements, the vertical load corresponding to the normal serviceability limit state is set, and the influence of long-term load is considered. Run the finite element solver to calculate the pile top settlement response of the engineering pile under the target load condition; The instantaneous settlement under normal serviceability limit state is extracted from the calculation results, and the long-term settlement of the engineering pile is calculated by combining the soil creep characteristics. The calculated instantaneous and long-term settlement results are compiled into a report and compared with the settlement limit requirements of the engineering design, providing a quantitative basis for optimizing the design parameters of pile length and support plate arrangement for karst area expansion piles.

8. A settlement calculation system for karst zone expansion and compaction piles considering the expansion and compaction effect, characterized in that, The method for calculating the settlement of karst zone expansion and compaction piles considering the expansion and compaction effect as described in any one of claims 1-7 includes a parameter acquisition and preprocessing module, a finite element model construction and parameter assignment module, a model verification module, and an engineering pile settlement prediction module. The parameter acquisition and preprocessing module is used to carry out field drilling and core sampling, indoor geotechnical tests and single pile tests, to obtain the stratum distribution, soil physical and mechanical parameters, graded load-displacement curves and load sharing of the support plate, to calculate the soil self-weight stress, confining pressure and deviatoric principal stress, and to obtain the relationship curve between deviatoric principal stress and axial strain through triaxial compression tests. The finite element model construction and parameter assignment module is used to build a three-dimensional model of the expanded support pile and the surrounding soil based on finite element software. Hardened zones are set at the bottom and sides of the support according to preset rules. Finite element analysis steps are created according to the graded load sequence of field test piles. The actual deviatoric principal stress of the soil at the support under each analysis step is calculated using the deviatoric principal stress-axial strain relationship curve. Based on the deviatoric principal stress and axial strain corresponding to two adjacent load levels on the deviatoric principal stress-axial strain relationship curve, the secant modulus of the soil between the two adjacent load levels is calculated. The differentiated elastic modulus of the ordinary soil layer, the bottom of the support, and the hardened zones on the sides is determined through back-analysis of a large amount of field test pile data. Simultaneously, the design elastic modulus is assigned to the pile body. The model verification module is used to assign values ​​to the modulus of the soil layer and the compaction zone in each analysis step, perform finite element calculations, extract the pile top settlement value and compare it with the load-displacement curve of the on-site test pile, and adjust the parameters until the degree of agreement meets the preset requirements to verify the effectiveness of the calculation model. The engineering pile settlement prediction module is used to predict the normal service limit state and long-term settlement of engineering piles by using a verified and effective calculation model and substituting the design parameters of the engineering piles, providing a basis for the engineering design of extruded and expanded support piles in karst areas.

9. An electronic device, characterized in that, It includes a processor and a memory, which are interconnected; The memory is used to store computer programs; The processor is configured to, when the computer program is invoked, execute the settlement calculation method for karst zone expansion piles considering the expansion and compaction effect as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that is executed by a processor to implement the settlement calculation method for karst zone expansion and compaction piles considering the expansion and compaction effect as described in any one of claims 1 to 7.

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