Estimation method and system for vertical bearing capacity of steel pipe pile

Abstract

The present application provides a steel pipe pile vertical bearing capacity estimation method and system, relates to the field of pile foundation engineering technology field, the present application carries out static sounding test to the seabed stratum required to be set for the steel pipe pile foundation, obtains experimental data and carries out normalization processing, divides the soil behavior type, and inverts the soil layer mechanical parameter; based on the soil layer mechanical parameter, the side friction and the end resistance of the steel pipe pile are calculated, and the initial static ultimate bearing capacity is obtained; the historical equivalent cyclic load experimental data of the construction sea area wave are obtained, the equivalent cyclic load reduction coefficient, the liquefaction reduction coefficient and the time-varying corrosion reduction coefficient are constructed, and the comprehensive time-varying reduction coefficient is constructed; based on the comprehensive time-varying reduction coefficient, the initial static ultimate bearing capacity is corrected, the vertical bearing capacity of the steel pipe pile in the long-term service period is predicted, and the time-varying ultimate bearing capacity is obtained; according to the time-varying ultimate bearing capacity, the evaluation threshold is set, the bearing capacity classification threshold interval is dynamically adjusted, and the bearing capacity classification evaluation result is output.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pile foundation engineering, in particular to a steel pipe pile vertical bearing capacity estimation method and system. BACKGROUND

[0002] With the rapid development of offshore wind power, offshore oil platforms and other marine engineering, the accurate estimation of the bearing capacity of steel pipe piles, which are an important foundation form of marine engineering structures, is crucial to engineering safety. The bearing performance of steel pipe piles in marine environments is influenced by various factors, including soil properties, environmental loads, and material properties. Currently, the estimation methods for the vertical bearing capacity of steel pipe piles are mainly based on static sounding test data, high-strain test data, and empirical formulas.

[0003] Static sounding technology is an important means of obtaining stratum parameters. The prior art disclosed in CN102587426A discloses an analysis method for estimating the bearing capacity of pile foundations based on sounding technology. This method measures the cone tip resistance and side friction resistance corresponding to different relative deformations between the probe and the soil, extracts the pile tip resistance and pile side friction resistance corresponding to different pile-soil relative deformations of each soil, establishes an empirical formula, and inversely calculates the pile foundation load-settlement curve to determine the bearing capacity of the pile foundation. This method has a clear mechanism and is simple to apply, but it is mainly for land pile foundations and does not consider the special nature of marine environments.

[0004] In the field of offshore wind power, the prior art disclosed in CN119203746A proposes a method for predicting the bearing capacity of a single pile in offshore wind power. This method obtains measured data of different strata where the single pile is located based on pore pressure static sounding tests, determines the side friction resistance and unit pile tip resistance of different strata, and optimizes the prediction by combining a neural network model and a genetic algorithm. This method improves the prediction accuracy, but does not fully consider the influence of time-varying factors in marine environments on the long-term bearing performance of pile foundations.

[0005] For the analysis of the vertical bearing capacity of pipe piles, CN108509755A discloses a method and system for analyzing the vertical bearing capacity of pipe piles based on high-strain test data. By obtaining a large amount of high-strain test data, extracting mechanical parameters to construct a database, using big data analysis techniques to classify and calculate the mechanical parameters, and combining finite element analysis to construct a load transfer function, the ultimate bearing capacity of the pipe pile is finally determined. Although this method considers the influence of different soil types on bearing capacity, it does not systematically study the effects of cyclic loads in marine environments.

[0006] However, the existing steel pipe pile bearing capacity estimation methods have the following shortcomings: first, most methods are mainly based on static soil mechanics parameters for calculation, without fully considering the dynamic factors in the marine environment; second, the cyclic load effect in the marine environment, soil liquefaction phenomenon and steel corrosion are not fully considered; third, there is a lack of systematic method for coupling analysis of multiple influencing factors; finally, the existing methods cannot accurately predict the change rule of the bearing capacity of the steel pipe pile during long-term service, and cannot provide reliable basis for engineering safety assessment. Especially in deep sea or complex seabed conditions, the traditional method is difficult to accurately reflect the actual working state of the pile foundation, resulting in great uncertainty in engineering design, affecting the safety and economy of the marine engineering structure.

[0007] Therefore, it is urgent to develop a steel pipe pile vertical bearing capacity estimation method that can comprehensively consider the coupling of multiple mechanisms such as cyclic load, soil liquefaction, material corrosion and other time-varying effects in the marine environment, to improve the accuracy and reliability of the design of marine engineering pile foundation.

[0008] The above information disclosed in the background section is only used to strengthen the understanding of the background of the present disclosure, and therefore it can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0009] The purpose of the present application is to provide a steel pipe pile vertical bearing capacity estimation method and system to solve the problems raised in the background.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0011] The steel pipe pile vertical bearing capacity estimation method comprises the following specific steps:

[0012] S1: Perform a static sounding test on the seabed stratum required to be set for the steel pipe pile foundation, obtain experimental data of each depth test point in the static sounding test, normalize the experimental data point by point, divide the soil behavior type based on the normalization result, and inversely obtain the mechanical parameters of each soil behavior type soil layer;

[0013] S2: Based on the soil layer mechanical parameters of each soil behavior type, calculate the side friction resistance between the steel pipe pile pile body and the surrounding soil and the end resistance of the pile end, to obtain the initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions;

[0014] S3: Obtain the historical equivalent cyclic load experimental data of the waves in the steel pipe pile construction sea area, construct the equivalent cyclic load reduction coefficient, the liquefaction reduction coefficient and the time-varying corrosion reduction coefficient, and construct the comprehensive time-varying reduction coefficient through multi-mechanism coupling;

[0015] S4: Based on the comprehensive time-varying reduction coefficient, the initial static ultimate bearing capacity of the steel pipe pile is corrected, the vertical bearing capacity of the steel pipe pile during the long-term service period is predicted, and the time-varying ultimate bearing capacity of the steel pipe pile is obtained.

[0016] S5: Set the bearing capacity assessment threshold according to the time-varying ultimate bearing capacity, and dynamically adjust the bearing capacity grading threshold range. Match the time-varying ultimate bearing capacity with the dynamic bearing capacity grading threshold range, and output the grading evaluation result for the vertical bearing capacity to be estimated for the steel pipe pile.

[0017] Furthermore, during the static cone penetration test, the seabed strata region was selected based on the location of the steel pipe pile foundation. During the test, a static cone penetration device was used to advance the device through the seabed strata in layers, with a predetermined total detection depth and equal intervals between detection layers. The midpoint depth of each predetermined equal interval layer was used as a test point to collect experimental data. The experimental data included: net cone tip resistance, side friction resistance, and static pore water pressure at each test point. The experimental data were normalized point by point to obtain the normalized cone tip resistance and normalized friction ratio for each test point, forming a data sequence for different test points. The specific formulas for obtaining the normalized cone tip resistance and normalized friction ratio for each test point are as follows:

[0018] ;

[0019] in, For the first Depth of each test point for Normalized cone tip resistance at depth for Normalized friction ratio at depth for Net cone tip resistance at depth for Side friction at depth Standard atmospheric pressure for Total overburden stress at depth for Effective overburden stress, Stress index; Total overburden stress, i.e., current depth The total weight of all the soil, including seawater, is calculated using the following formula:

[0020] ;

[0021] ;

[0022] in, The density of seawater, It is the acceleration due to gravity. Because of the water depth, The soil weight, yes Static pore water pressure at depth; further, soil layers are divided based on the normalized results, i.e., according to... and Soil behavior was classified by comparing with the soil behavior type chart, and the soil behavior types were divided into clay, sand, and mixed soil. The soil behavior type corresponding to the test point at the midpoint depth of each predetermined detection interval layer represents the soil behavior type of that detection interval layer. At the same time, the mechanical parameters of each interval layer were inverted for each interval layer soil behavior type. The undrained shear strength was inverted for clay interval layer, and the internal friction angle was inverted for sand interval layer. The inversion formulas are as follows:

[0023] ;

[0024] ;

[0025] in, clay-based interlayer Shear strength at depth without drainage For the empirical cone factor, Sandy soil interlayer The internal friction angle at depth; the equivalent friction angle and equivalent cohesion of the mixed soil interlayer are solved iteratively, satisfying the following formula:

[0026] ;

[0027] in, Interlayer of mixed soil Equivalent internal friction angle at depth This is a soil behavior index. This is an empirical coefficient. Interlayer of mixed soil Equivalent cohesion at depth.

[0028] Furthermore, the side friction between the steel pipe pile and the surrounding soil, and the end resistance at the pile tip are calculated. The steel pipe pile is divided along the depth direction from the soil surface to the pile tip into... Each micro-segment is at the same height as the probe's equally spaced layers, with the midpoint depth of each micro-segment being equal to... One-to-one correspondence, the height of each micro-segment is The initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions is obtained:

[0029] ;

[0030] in, This is the initial ultimate bearing capacity. for side friction at the micro segment, is the end resistance, is the micro segment number, is the underwater self-weight of the steel pipe pile.

[0031] Further, the steel pipe pile body is at different soil behavior type interval layers at each micro segment, the side friction corresponding to the soil behavior type interval layer where each micro segment is located is calculated respectively, and the steel pipe pile end is also at different soil behavior type interval layers corresponding to different end resistances; when the soil behavior type interval layer where the micro segment is located is clay, the formula for the side friction and the end resistance is:

[0032] ;

[0033] When the soil behavior type interval layer where the micro segment is located is sand, the formula for the side friction and the end resistance is:

[0034] ;

[0035] When the soil behavior type interval layer where the micro segment is located is mixed soil, the formula for the side friction and the end resistance is:

[0036] ;

[0037] wherein, is the adhesion coefficient at the micro segment, is the lateral earth pressure coefficient, is the diameter of the steel pipe pile, is the bearing capacity coefficient related to the friction angle of the sand type interval layer, is the bearing capacity coefficient related to the friction angle of the mixed soil type interval layer, is the bearing capacity coefficient related to the cohesion of the clay type interval layer, is the bearing capacity coefficient related to the cohesion of the mixed soil type interval layer.

[0038] Further, the equivalent cyclic load experimental data of the wave in the steel pipe pile construction sea area is obtained, the equivalent cyclic load reduction coefficient, the liquefaction reduction coefficient, and the time-varying corrosion reduction coefficient are constructed, the comprehensive time-varying reduction coefficient is constructed through multi-mechanism coupling , the formula is as follows:

[0039] ;

[0040] wherein, is the comprehensive time-varying reduction coefficient, is the liquefaction reduction coefficient, ​The time-varying corrosion reduction coefficient, the liquefaction reduction coefficient and the construction idea of the time-varying corrosion reduction coefficient are as follows: obtaining the historical equivalent cyclic load experimental data of waves in the sea area of steel pipe pile construction, wherein the historical equivalent cyclic load experimental data: annual average equivalent cyclic load times, annual average equivalent cyclic load stress ratio, annual average equivalent cyclic load resistance ratio, equivalent cyclic load reduction coefficient, liquefaction reduction coefficient and time-varying corrosion reduction coefficient calculation formula is as follows:

[0041] ;

[0042] Among them, is the equivalent cyclic load reduction coefficient, is the cyclic load empirical coefficient, is the average equivalent cyclic load, is the liquefaction reduction empirical coefficient, is the annual average equivalent cyclic load stress ratio, is the annual average equivalent cyclic load resistance ratio, is the average value ratio of and , is the initial wall thickness of steel pipe pile, is the length of steel pipe pile, is the corrosion depth, is the time variable.

[0043] Further, based on the comprehensive time-varying reduction coefficient, the initial static ultimate bearing capacity of the steel pipe pile is corrected, the vertical bearing capacity of the steel pipe pile in the long-term service period is predicted, the time-varying ultimate bearing capacity of the steel pipe pile is obtained, and the formula is as follows:

[0044] ;

[0045] Among them, is the initial ultimate bearing capacity, is the time-varying ultimate bearing capacity, that is, the ultimate bearing capacity at time t.

[0046] Further, according to the time-varying ultimate bearing capacity, the bearing capacity evaluation threshold is set, the bearing capacity classification threshold interval is dynamically adjusted, the time-varying ultimate bearing capacity is matched with the dynamic bearing capacity classification threshold interval, and the classification evaluation result of the steel pipe pile to be estimated vertical bearing capacity is output; The specific logic is as follows: if , it is safe, and the bearing capacity is sufficient; If , it is normal, and the steel pipe pile is in normal state; if , it is early warning, and the bearing capacity is lower than or close to the failure threshold; in the formula, is the preset bearing capacity threshold.

[0047] The application also provides a steel pipe pile vertical bearing capacity estimation system for executing the above steel pipe pile vertical bearing capacity estimation method, comprising:

[0048] The surveying and data processing module is used for performing a static sounding test on seabed strata required to be set for a steel pipe pile foundation, obtaining experimental data of each depth test point in the static sounding test, performing point-by-point normalization processing on the experimental data, performing soil behavior type division based on the normalization result, and inversely obtaining mechanical parameters of each soil behavior type soil layer;

[0049] The static bearing capacity calculation module is used for calculating side friction between a steel pipe pile body and surrounding soil and end resistance of a pile end based on the mechanical parameters of each soil behavior type soil layer, so as to obtain initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions;

[0050] The time-varying reduction coefficient calculation module is used for obtaining historical equivalent cyclic load experimental data of waves in a steel pipe pile construction sea area, constructing equivalent cyclic load reduction coefficients, liquefaction reduction coefficients, and time-varying corrosion reduction coefficients, and constructing comprehensive time-varying reduction coefficients through multi-mechanism coupling;

[0051] The time-varying bearing capacity prediction module is used for correcting the initial static ultimate bearing capacity of the steel pipe pile based on the comprehensive time-varying reduction coefficients, predicting vertical bearing capacity of the steel pipe pile in a long-term service period, and obtaining time-varying ultimate bearing capacity of the steel pipe pile;

[0052] The safety grade evaluation module is used for setting a bearing capacity evaluation threshold according to the time-varying ultimate bearing capacity, dynamically adjusting a bearing capacity classification threshold interval, matching the time-varying ultimate bearing capacity with the dynamic bearing capacity classification threshold interval, and outputting a classification evaluation result for the steel pipe pile to be estimated vertical bearing capacity.

[0053] Compared with the prior art, the beneficial effects of the present application are: through the static sounding test to obtain the soil layer parameters and carry out the normalization processing, the accurate division and mechanical parameter inversion of different soil behaviors are realized, compared with the traditional method, the actual situation of the seabed stratum can be more accurately reflected, and the precision of the basic data of the bearing capacity estimation is improved; the steel pipe pile is divided into multiple micro segments along the depth direction, the side friction and end resistance under different soil layer types are calculated respectively, and the initial ultimate bearing capacity is accumulated, this micro element method can reflect the complexity of the pile-soil interaction more than the traditional overall calculation method, and the accuracy of the static bearing capacity calculation is improved; the comprehensive time-varying reduction coefficient is innovatively constructed, the coupling of multiple time-varying factors such as cyclic load, soil liquefaction and material corrosion is considered, the whole cycle safety evaluation from static to dynamic and from short term to long term is realized, and the shortcomings of the traditional method considering only static conditions are made up; by setting the dynamic threshold interval, the time-varying bearing capacity is matched with the threshold value, the safety, normal or warning level is output, the dynamic evaluation of the steel pipe pile bearing capacity state is realized, the practicality and adaptability of the evaluation results are improved according to the flexible adjustment of different engineering safety standards; compared with the prior art, the accuracy of the steel pipe pile bearing capacity prediction in the marine environment is improved, and more reliable technical support is provided for the long-term safety evaluation of the marine engineering structure. BRIEF DESCRIPTION OF DRAWINGS

[0054] Fig. 1 It is the overall method flowchart of the present application;

[0055] Fig. 2 It is the static sounding test parameter curve with depth change of the embodiment of the present application;

[0056] Fig. 3 It is the relationship graph of the partial corrosion depth and the reduction coefficient of the embodiment of the present application;

[0057] Fig. 4 It is the vertical bearing capacity estimation system schematic block diagram of the steel pipe pile in the present application. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the present application is further described in detail below combined with specific embodiments.

[0059] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the meanings that can be commonly understood by a person having ordinary skill in the art to which the present application belongs. The terms "first", "second", and similar terms in the present application do not denote any order, quantity, or importance, but are used to distinguish different components. The terms "include", "contain", and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like are used only to represent relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0060] Embodiment:

[0061] Please refer to Figs. 1 to 3 , the present application provides a technical solution:

[0062] The steel pipe pile vertical bearing capacity estimation method comprises the following specific steps:

[0063] S1: Static cone penetration test is performed on the seabed stratum required to be set for the steel pipe pile foundation, experimental data of each depth test point in the static cone penetration test is obtained, the experimental data is point-by-point normalized, soil behavior type classification is performed based on the normalization result, and the mechanical parameters of each soil behavior type soil layer are inversely obtained; in the embodiment, the seabed stratum region is selected according to the position of the steel pipe pile foundation during the static cone penetration test, the seabed stratum is layered and pushed forward by using a static cone penetration device during the static cone penetration test, and a predetermined total detection depth and detection equal-interval layers are used, wherein the midpoint depth of each predetermined detection equal-interval layer is used as a test point to collect experimental data; the experimental data includes net cone tip resistance, side friction resistance, and static pore water pressure at each test point; the experimental data is point-by-point normalized to obtain the normalized cone tip resistance and normalized friction ratio of each test point, and a data sequence of different test points is formed, as shown in Table 1; the normalization is to eliminate the influence of overburden stress on the test results, so that the static cone penetration test data under different depths and different geological conditions can be compared and classified under the same standard, and the stress conditions of each depth point are normalized and calculated separately; the specific formulae of the normalized cone tip resistance and the normalized friction ratio of each test point are as follows:

[0064] ;

[0065] wherein, is the depth of the i th test point, is the normalized cone tip resistance of the i th test point, and is the normalized friction ratio of the i th test point. Normalized cone tip drag at depth is used to eliminate effective overburden stress at different depths. The influence of this necessitates normalization of the net cone tip resistance. A stress exponent is used here. We need to consider the effect of stress level on the normalization effect. A commonly used normalization method is to divide the net cone tip drag by standard atmospheric pressure. Then multiply by the ratio of effective overburden stress to reference stress. The purpose of this is to convert the cone tip drag at different stress levels to standard atmospheric pressure. The comparison is made because soil stiffness varies under different confining pressures. This is a stress level correction term; for Normalized friction ratio at depth, the friction ratio is the sidewall frictional resistance. With cone tip resistance The ratio of [the two values], however, to more accurately reflect the properties of the soil, the net cone tip resistance is used here. As the denominator, the sidewall friction resistance It mainly reflects the frictional characteristics of the pile-soil interface, while the cone tip resistance... Subtracting the overburden stress provides a more accurate reflection of the soil's true strength. Therefore, using... Dividing by the net cone tip resistance can eliminate the influence of overburden stress on the friction ratio, making the friction ratio more reflective of the soil type; for Net cone tip resistance at depth for Side friction at depth Standard atmospheric pressure for Total overburden stress at depth for Effective overburden stress at depth Stress index; Total overburden stress, i.e., current depth The total weight of all the soil, including seawater, is calculated using the following formula:

[0066] ;

[0067] ;

[0068] in, The density of seawater, It is the acceleration due to gravity. Because of the water depth, The soil weight, yes Static pore water pressure at depth; soil layers are divided based on normalized results, i.e., according to... and Soil behavior was classified by comparing with the soil behavior type chart, and the soil behavior types were divided into clay, sand, and mixed soil. The soil behavior type corresponding to the test point at the midpoint depth of each predetermined detection interval layer represents the soil behavior type of that detection interval layer. At the same time, the mechanical parameters of each interval layer were inverted for each interval layer soil behavior type. The undrained shear strength was inverted for clay interval layer, and the internal friction angle was inverted for sand interval layer. The inversion formulas are as follows:

[0069] ;

[0070] ;

[0071] in, clay-based interlayer The undrained shear strength at depth is determined based on the spherical cavity expansion theory, establishing a relationship between the net cone tip resistance and the undrained shear strength. For the empirical cone factor, Sandy soil interlayer The internal friction angle at depth; the equivalent friction angle and equivalent cohesion of the mixed soil interlayer are solved iteratively, satisfying the following formula:

[0072] ;

[0073] in, Interlayer of mixed soil Equivalent internal friction angle at depth For soil behavior index, This is an empirical coefficient. Interlayer of mixed soil Equivalent cohesion at depth.

[0074] Static cone penetration testing significantly reduces soil sample disturbance and stress release errors associated with traditional borehole sampling and laboratory testing. Soil parameter inversion is based on internationally recognized soil classification charts (such as the Robertson diagram) and inversion formulas, transforming the probe data into the mechanical parameters directly required for design.

[0075] In this embodiment, the marine static sounding system is positioned to the pile design position, the probe rod is pressed into the seabed at a constant rate of 2 cm / s until the predetermined depth, the sensor continuously collects the net cone tip resistance, side friction resistance and pore water pressure of each depth point; Normalization processing and systematic soil behavior classification (Robertson chart) are adopted, so that the total overburden stress and effective overburden stress are calculated point by point according to the soil layer and seawater information, the steel pipe pile parameters, the diameter is 1.5 m, the length is 50 m, the initial wall thickness is 0.05 m, the underwater self weight is 600 kN, the sea water density required to be set for the steel pipe pile foundation is 1025 kg / m³, the water depth is 21.7 m, the gravitational acceleration is 9.81 m / s², the standard atmospheric pressure is 101.3 kPa, the normally consolidated clay is very sensitive to confining pressure, and its stiffness is roughly proportional to the effective stress, so the clay stress index is 1; The stiffness of quartz sand is roughly proportional to the square root of the effective stress, so the sand stress index is 0.5; The characteristics of mixed soil are between the two, so take an intermediate value, so the mixed soil stress index is 0.75; Empirical cone factor , the cone factor value needs to be calibrated by regional experience, and the local geological survey report and engineering experience should be referred to; Empirical coefficient , empirical coefficient , soil behavior index ; In this embodiment, the net cone tip resistance at the depth of , the side friction resistance at the depth of , the following experimental data table 1 is generated by calculation: Table 1 clearly shows the data of each test point from the seabed surface to 50 meters deep, the table contains the original experimental data , , and the key normalized parameters , and inversion parameters calculated at each depth point.

[0076] Table 1: Soil behavior data table of test points

[0077]

[0078] Please refer to Fig. 2 , Fig. 2 ​​The static sounding device is used to divide the seabed stratum into layers in step S1 in the embodiment, the total detection depth is predetermined, and the detection is carried out at equal intervals. The total detection depth should ensure complete coverage of the pile foundation influence area. The total detection depth must be greater than the pile penetration depth, and the soil below the pile tip also has an important influence on the bearing capacity. The goal is to reveal all the soil layers within the range of the pile body friction resistance and the bearing stratum and underlying layer on which the pile tip resistance depends. The total detection depth should be at least the planned penetration depth plus k times the pile diameter. The soil properties within k times the pile diameter have a significant impact on the end resistance. The detection interval height is predetermined. The smaller the interval, the higher the data density, and the stronger the ability to distinguish thin layers. However, the longer the exploration time, the larger the amount of data. If the interval is too large, key thin layers may be missed, resulting in model distortion. In the embodiment, 2m is used as the detection interval height, and the midpoint depth of each predetermined detection interval is used as the test point. The experimental data collected at each test point include the net cone tip resistance, side friction resistance, and static pore water pressure. The experimental data in Table 1 are visualized. By Fig. 2 we can see that the net cone tip resistance increases with depth and shows a clear layered trend: in the shallow layer, about 1-9 meters of clay layer, the value is low and increases slowly; in the sand layer, about 11-33 meters, the value increases significantly, showing the high bearing capacity characteristics of sand; in the deep mixed soil layer, 35-49 meters, the value tends to be stable. The side friction resistance also increases with depth, especially in the sand and mixed soil layers. The static pore water pressure increases linearly with depth, which is consistent with the distribution of hydrostatic pressure. These trends provide a reliable data basis for the classification of soil behavior types and the inversion of mechanical parameters.

[0079] S2: Based on the soil layer mechanical parameters of each soil behavior type, the side friction resistance between the steel pipe pile body and the surrounding soil and the end resistance of the pile tip are calculated to obtain the initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions. The side friction resistance between the steel pipe pile body and the surrounding soil and the end resistance of the pile tip are calculated, and the steel pipe pile is divided into micro-segments along the depth direction from the soil surface to the pile tip, each micro-segment has a height consistent with the detection interval height, and the midpoint depth of each micro-segment corresponds to each detection interval, that is, the micro-segment height is consistent with the detection interval height, the micro-segment corresponds to the detection interval, and the height of each micro-segment is , to obtain the initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions:

[0080] ;

[0081] in, This is the initial ultimate bearing capacity. for Side friction at the micro-segment For end resistance, For micro-segment numbers, The underwater self-weight of the steel pipe pile is considered. Each micro-segment of the steel pipe pile is located in an interval layer with different soil behavior types. The side skin friction corresponding to the soil behavior type interval layer of each micro-segment is calculated separately, and the end resistance corresponding to different soil behavior type interval layers at the pile tip is also calculated. When the soil behavior type of the micro-segment is clay, the formulas used for the side skin friction and end resistance are as follows:

[0082] ;

[0083] When the soil behavior type of the micro-segment is a sandy interlayer, the formulas for side friction and end resistance are as follows:

[0084] ;

[0085] Based on the effective stress principle, it is assumed that the side friction resistance is proportional to the effective overburden stress at that point; if Taking a value that is too small will underestimate the side skin resistance in sandy soil; the pile driving process has an impact on... The value has a significant impact; if Taking a value that is too large will directly overestimate the side friction resistance.

[0086] When the soil behavior type of the micro-segment is a mixed soil interlayer, the formulas for side friction and end resistance are as follows:

[0087] ;

[0088] in, micro-segment The adhesion coefficient at the location, The lateral earth pressure coefficient, The diameter of the steel pipe pile is... The bearing capacity coefficient related to the friction angle of the sandy soil interlayer is... The bearing capacity coefficient related to the friction angle of the mixed soil interlayer. This refers to the bearing capacity coefficient related to the cohesion of clay-based interlayers. It provides bearing capacity coefficients related to cohesion in mixed soil layers; and offers different calculation models for clay, sand, and mixed soil, enabling flexible adaptation to complex marine geological conditions. , The value of the bearing capacity coefficient directly affects the end resistance. The layered summation method is adopted to refine the contribution of different soil layers to the lateral resistance and to clarify the source of the end resistance. The model has clear physical meaning and is much better than a single comprehensive formula.

[0089] In this embodiment, the initial ultimate bearing capacity is further calculated according to the S1 experimental results and the data obtained, wherein,

[0090] ;

[0091] The actual adhesion force of the pile-soil interface in clay is not equal to the undrained shear strength of the soil body, and the adhesion coefficient is used to represent the reduction; The value is related to the sensitivity of the soil and the stress history; the complex interaction of the pile-soil interface is simplified as an empirical coefficient related to the strength and stress history of the soil body. For clay with a high overconsolidation ratio and high strength, the value is small; for normally consolidated soft clay, the value is large but does not exceed 1.0.

[0092] ;

[0093] ;

[0094] In this embodiment, , ; the lateral earth pressure coefficient 0.8. During the piling process, the soil body is severely disturbed. For open-ended piles, part of the soil core will enter the inside of the pile pipe, and the extrusion effect on the soil around the pile is smaller than that of closed piles, so the value is smaller than the static earth pressure coefficient, and the static earth pressure coefficient is usually about ;

[0095] The lateral friction at the second micro-section in this embodiment, i.e., the position , and the end resistance at the 25th micro-section, i.e., the position , are calculated as calculation examples:

[0096] ;

[0097] The sum of all 25 micro-sections is calculated, , For example, the purpose is to show the process. In actual calculation, all micro-sections need to be accurately summed, and the formula for the end resistance of the pile may be different. In this case, the S2 formula is used for calculation, and the subsequent time-varying reduction will be based on this new value.

[0098] S3: Obtain the historical equivalent cyclic load experimental data of the steel pipe pile construction sea area wave, construct the equivalent cyclic load reduction coefficient, liquefaction reduction coefficient and time-varying corrosion reduction coefficient, and construct the comprehensive time-varying reduction coefficient through multi-mechanism coupling;

[0099] In this embodiment, the equivalent cyclic load experimental data of the steel pipe pile construction sea area wave is obtained, the equivalent cyclic load reduction coefficient, the liquefaction reduction coefficient and the time-varying corrosion reduction coefficient are constructed, and the comprehensive time-varying reduction coefficient is constructed through multi-mechanism coupling , the formula is as follows:

[0100] ;

[0101] Among them, is the comprehensive time-varying reduction coefficient, is the liquefaction reduction coefficient, is the time-varying corrosion reduction coefficient, and the construction idea of the liquefaction reduction coefficient and the time-varying corrosion reduction coefficient is as follows: the historical equivalent cyclic load experimental data of the steel pipe pile construction sea area wave is obtained, wherein the historical equivalent cyclic load experimental data: the annual average equivalent cyclic load number, the annual average equivalent cyclic load stress ratio, the annual average equivalent cyclic load resistance ratio, the equivalent cyclic load reduction coefficient, the liquefaction reduction coefficient and the time-varying corrosion reduction coefficient calculation formula is as follows:

[0102] ;

[0103] Among them, is the equivalent cyclic load reduction coefficient, is the cyclic load empirical coefficient, is the average equivalent cyclic load number; the logarithmic form of the fatigue cumulative damage model is adopted, which shows that the bearing capacity degradation rate is fast first and then slow, which is consistent with the material fatigue test rule; is the liquefaction reduction empirical coefficient, is the annual average equivalent cyclic load stress ratio, is the annual average equivalent cyclic load resistance ratio, which captures two failure modes: cyclic softening and complete liquefaction , is the average value ratio of and , which is the core of judging liquefaction. If is overestimated or is too small, the value of will increase, which may trigger the liquefaction reduction term and cause the bearing capacity to drop sharply; directly from the geometric point of view, the ratio of the remaining effective cross-sectional area is calculated, which has clear concept and clear physical meaning, is the initial wall thickness of the steel pipe pile, is the length of the steel pipe pile, is the corrosion depth, is a time variable. In this embodiment, , .

[0104] S4: Based on the comprehensive time-varying reduction coefficient, the initial static ultimate bearing capacity of the steel pipe pile is corrected, the vertical bearing capacity of the steel pipe pile in the long-term service period is predicted, and the time-varying ultimate bearing capacity of the steel pipe pile is obtained. Based on the comprehensive time-varying reduction coefficient, the initial static ultimate bearing capacity of the steel pipe pile is corrected, the vertical bearing capacity of the steel pipe pile in the long-term service period is predicted, and the time-varying ultimate bearing capacity of the steel pipe pile is obtained. The formula is as follows:

[0105] ;

[0106] wherein, is the initial ultimate bearing capacity, is the time-varying ultimate bearing capacity, that is, the ultimate bearing capacity at time t; the influence of the three reduction mechanisms on the bearing capacity is coupled, and is proportional to the initial bearing capacity;

[0107] S5: According to the time-varying ultimate bearing capacity, the bearing capacity evaluation threshold is set, the bearing capacity classification threshold interval is dynamically adjusted, the time-varying ultimate bearing capacity is matched with the dynamic bearing capacity classification threshold interval, and the classification evaluation result for the vertical bearing capacity to be estimated of the steel pipe pile is output. According to the time-varying ultimate bearing capacity, the bearing capacity evaluation threshold is set, the bearing capacity classification threshold interval is dynamically adjusted, the time-varying ultimate bearing capacity is matched with the dynamic bearing capacity classification threshold interval, and the classification evaluation result for the vertical bearing capacity to be estimated of the steel pipe pile is output. The specific logic is as follows: if , it is safe and the bearing capacity is sufficient; If , the steel pipe pile is in a normal state; if , it is a warning, and the bearing capacity is below or close to the failure threshold; wherein, is a preset bearing capacity threshold. In this embodiment, , then, , it is safe; , it is normal, , it is a warning, and the bearing capacity is below or close to the failure threshold; wherein,

[0108] Table 2: Reduction coefficient and time-varying ultimate bearing capacity data table

[0109]

[0110] As can be seen from Table 2, the corrosion depth increases over time. The time-varying corrosion reduction coefficient gradually increases. Corresponding reduction; equivalent cyclic load reduction factor and liquefaction reduction factor Influenced by the interannual fluctuations of wave loads, it exhibits a certain degree of volatility. (Comprehensive reduction factor) The variation between 0.664 and 0.82 results in a time-varying ultimate bearing capacity. The load fluctuated between 21288 kN and 26289 kN. At 20 years, due to significant liquefaction reduction, the bearing capacity dropped to the "normal" level, while in other years it remained in a "safe" state, indicating that the steel pipe piles in this embodiment have sufficient overall safety margin during their 30-year service life.

[0111] Please see Fig. 3 , Fig. 3 The paper clearly demonstrates the relationship between corrosion depth and the time-varying corrosion reduction coefficient and the comprehensive reduction coefficient during the service life of steel pipe piles. Corrosion depth is inversely proportional to both the time-varying corrosion reduction coefficient and the comprehensive reduction coefficient; the deeper the corrosion, the lower the reduction coefficient. Fig. 3 It can be seen that the corrosion depth With reduction factor and A clear negative correlation is observed. As corrosion deepens, the effective cross-sectional area of ​​the pile decreases, leading to a gradual decline in the reduction factor. The curves in the figure clearly demonstrate the cumulative weakening effect of corrosion on long-term bearing capacity. They also reflect that under well-controlled corrosion conditions, the reduction factor decreases relatively slowly, but the reduction effect intensifies later as corrosion accelerates. This relationship highlights the importance of corrosion prevention measures in maintaining the long-term performance of pile foundations in marine environments.

[0112] Please see Fig. 4 The present invention also provides a system for estimating the vertical bearing capacity of steel pipe piles, the system being used to execute the above-described method for estimating the vertical bearing capacity of steel pipe piles, comprising:

[0113] The exploration and data processing module is used to conduct static cone penetration tests on the seabed strata required for steel pipe pile foundations, obtain experimental data at each depth test point in the static cone penetration test, normalize the experimental data point by point, classify soil behavior types based on the normalization results, and invert the mechanical parameters of soil layers of each soil behavior type.

[0114] Static bearing capacity calculation module: used to calculate the side friction resistance between the steel pipe pile body and the surrounding soil and the end resistance of the pile end based on the soil mechanical parameters of each soil behavior type, so as to obtain the initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions.

[0115] The time-varying reduction coefficient calculation module is configured to obtain historical equivalent cyclic load experimental data of waves in a steel pipe pile construction sea area, construct an equivalent cyclic load reduction coefficient, a liquefaction reduction coefficient, and a time-varying corrosion reduction coefficient, and construct a comprehensive time-varying reduction coefficient through multi-mechanism coupling.

[0116] The time-varying bearing capacity prediction module is configured to correct the initial static ultimate bearing capacity of the steel pipe pile based on the comprehensive time-varying reduction coefficient, predict the vertical bearing capacity of the steel pipe pile in a long-term service period, and obtain the time-varying ultimate bearing capacity of the steel pipe pile.

[0117] The safety grade evaluation module is configured to set a bearing capacity evaluation threshold according to the time-varying ultimate bearing capacity, dynamically adjust a bearing capacity classification threshold interval, match the time-varying ultimate bearing capacity with the dynamic bearing capacity classification threshold interval, and output a classification evaluation result for the steel pipe pile to be evaluated in terms of the vertical bearing capacity.

[0118] The above formulas are all dimensionless values calculated, the formulas are obtained by collecting a large amount of data to simulate a formula of the most recent real situation, and preset parameters in the formulas are set by a person skilled in the art according to actual conditions.

[0119] The above embodiments can be realized wholly or partially by software, hardware, firmware, or any other combination. When realized by software, the above embodiments can be realized wholly or partially in the form of a computer program product. Those skilled in the art can realize that the units and algorithm steps of the examples described in connection with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized by hardware or software methods depends on the specific application and design constraints of the technical solutions.

[0120] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, which can be located in one place or distributed on multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0121] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for estimating the vertical bearing capacity of steel pipe piles, characterized in that, The specific steps include: S1: Conduct static cone penetration tests on the seabed strata where the steel pipe pile foundation is located, obtain experimental data at each depth test point in the static cone penetration test, normalize the experimental data point by point, classify the soil behavior type based on the normalization results, and invert the mechanical parameters of the soil layer of each soil behavior type. S2: Based on the soil mechanical parameters of each soil behavior type, calculate the side friction between the steel pipe pile body and the surrounding soil and the end resistance at the pile end to obtain the initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions. S3: Obtain historical equivalent cyclic load experimental data of waves in the sea area where steel pipe piles are constructed, construct equivalent cyclic load reduction coefficient, liquefaction reduction coefficient and time-varying corrosion reduction coefficient, and construct comprehensive time-varying reduction coefficient through multi-mechanism coupling. S4: Based on the comprehensive time-varying reduction coefficient, the initial static ultimate bearing capacity of the steel pipe pile is corrected, the vertical bearing capacity of the steel pipe pile during the long-term service period is predicted, and the time-varying ultimate bearing capacity of the steel pipe pile is obtained. S5: Set the bearing capacity assessment threshold according to the time-varying ultimate bearing capacity, and dynamically adjust the bearing capacity grading threshold range. Match the time-varying ultimate bearing capacity with the dynamic bearing capacity grading threshold range, and output the grading evaluation result for the vertical bearing capacity to be estimated for the steel pipe pile.

2. The method for estimating the vertical bearing capacity of steel pipe piles according to claim 1, characterized in that: During static cone penetration testing, the seabed strata region is selected based on the location of the steel pipe pile foundation. The test is conducted in layers, with a predetermined total depth and equal intervals between layers. The midpoint depth of each predetermined interval layer serves as a test point, and experimental data is collected. The experimental data includes net cone tip resistance, side friction resistance, and static pore water pressure at each test point. The experimental data is then normalized point by point to obtain the normalized cone tip resistance and normalized friction ratio for each test point, forming a data sequence for different test points. The specific formulas for obtaining the normalized cone tip resistance and normalized friction ratio for each test point are as follows: ； in, For the first Depth of each test point for Normalized cone tip resistance at depth for Normalized friction ratio at depth for Net cone tip resistance at depth for Side friction at depth Standard atmospheric pressure for Total overburden stress at depth for Effective overburden stress at depth Stress index; Total overburden stress, i.e., current depth The total weight of all the soil, including seawater, is calculated using the following formula: ； ； in, The density of seawater, It is the acceleration due to gravity. Because of the water depth, The soil weight, yes Static pore water pressure at depth.

3. The method for estimating the vertical bearing capacity of steel pipe piles according to claim 2, characterized in that: Soil layer division is based on normalization results, i.e., according to and Soil behavior was classified by comparing with the soil behavior type chart, and the soil behavior types were divided into clay, sand, and mixed soil. The soil behavior type corresponding to the test point at the midpoint depth of each predetermined detection interval layer represents the soil behavior type of that detection interval layer. At the same time, the mechanical parameters of each interval layer were inverted for each interval layer soil behavior type. The undrained shear strength was inverted for clay interval layer, and the internal friction angle was inverted for sand interval layer. The inversion formulas are as follows: ； in, clay-based interlayer Undrained shear strength at depth For the empirical cone factor, Sandy soil interlayer The internal friction angle at depth; the equivalent friction angle and equivalent cohesion of the mixed soil interlayer are solved iteratively, satisfying the following formula: ； in, Interlayer of mixed soil Equivalent internal friction angle at depth For soil behavior index, This is an empirical coefficient. Interlayer of mixed soil Equivalent cohesion at depth.

4. The method for estimating the vertical bearing capacity of steel pipe piles according to claim 1, characterized in that: Calculate the side friction between the steel pipe pile and the surrounding soil, and the end resistance at the pile tip. Divide the steel pipe pile along the depth direction from the soil surface to the pile tip into sections. Each micro-segment is at the same height as the probe's equally spaced layers, with the midpoint depth of each micro-segment being equal to... One-to-one correspondence, the height of each micro-segment is The initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions is obtained: ； in, This is the initial ultimate bearing capacity. for Side friction at the micro-segment For end resistance, For micro-segment numbers, The underwater weight of the steel pipe pile.

5. The method for estimating the vertical bearing capacity of steel pipe piles according to claim 4, characterized in that: Each micro-segment of the steel pipe pile body is located in an interval layer with different soil behavior types. The side skin friction corresponding to the soil behavior type interval layer in which each micro-segment is located is calculated separately, and the end resistance corresponding to different soil behavior type interval layers in which the steel pipe pile tip is located is also different. When the soil behavior type of the micro-segment is clay, the formulas used for the side skin friction and end resistance are as follows: ； When the soil behavior type of the micro-segment is a sandy interlayer, the formulas for side friction and end resistance are as follows: ； When the soil behavior type of the micro-segment is a mixed soil interlayer, the formulas for side friction and end resistance are as follows: ； in, micro-segment The adhesion coefficient at the location, The lateral earth pressure coefficient, The diameter of the steel pipe pile is... The bearing capacity coefficient related to the friction angle of the sandy soil interlayer is... The bearing capacity coefficient related to the friction angle of the mixed soil interlayer is... This refers to the bearing capacity coefficient related to the cohesion of clay-based interlayers. This is the bearing capacity coefficient related to the cohesion of the interlayer in mixed soil.

6. The method for estimating the vertical bearing capacity of steel pipe piles according to claim 2, characterized in that: Equivalent cyclic load experimental data of waves in the sea area where steel pipe piles are constructed were obtained. Equivalent cyclic load reduction factors, liquefaction reduction factors, and time-varying corrosion reduction factors were constructed. A comprehensive time-varying reduction factor was then constructed through multi-mechanism coupling. The formula is as follows: ； in, To incorporate the time-varying reduction factor, This is the liquefaction reduction factor. The time-varying corrosion reduction factor, liquefaction reduction factor, and time-varying corrosion reduction factor are constructed using the following approach: Historical equivalent cyclic load experimental data of waves in the sea area where steel pipe piles are constructed are obtained. This historical equivalent cyclic load experimental data includes: the annual average number of equivalent cyclic loads in the construction sea area, the annual average equivalent cyclic load stress ratio, and the annual average equivalent cyclic load resistance ratio. The calculation formulas for the equivalent cyclic load reduction factor, liquefaction reduction factor, and time-varying corrosion reduction factor are as follows: ； ； in, This is the equivalent cyclic load reduction factor. For cyclic load empirical coefficients, The average equivalent number of cycles, This is the empirical coefficient for liquefaction reduction. The annual average equivalent cyclic load stress ratio, The annual average equivalent cyclic load resistance ratio. This represents the initial wall thickness of the steel pipe pile. The length of the steel pipe pile. For corrosion depth, It is a time variable.

7. The method for estimating the vertical bearing capacity of steel pipe piles according to claim 6, characterized in that: Based on the aforementioned comprehensive time-varying reduction coefficient, the initial static ultimate bearing capacity of the steel pipe pile is corrected, and the vertical bearing capacity of the steel pipe pile during its long-term service life is predicted, thus obtaining the time-varying ultimate bearing capacity of the steel pipe pile, as shown in the following formula: ； in, This is the initial ultimate bearing capacity. The time-varying ultimate bearing capacity, i.e. Limit load capacity at all times.

8. The method for estimating the vertical bearing capacity of steel pipe piles according to claim 7, characterized in that: Based on the time-varying ultimate bearing capacity, a bearing capacity assessment threshold is set, and the bearing capacity grading threshold range is dynamically adjusted. The time-varying ultimate bearing capacity is matched with the dynamic bearing capacity grading threshold range, and a grading evaluation result for the vertical bearing capacity to be estimated for the steel pipe pile is output. The specific logic is as follows: If Therefore, it is safe and has sufficient load-bearing capacity; like If so, it's normal; the steel pipe pile is in a normal state. If the load-bearing capacity is below or close to the failure threshold, an early warning will be issued; where, This is the preset load-bearing capacity threshold.

9. A system for estimating the vertical bearing capacity of steel pipe piles, characterized in that: The steel pipe pile vertical bearing capacity estimation system is used to execute the steel pipe pile vertical bearing capacity estimation method according to any one of claims 1-8, including: The exploration and data processing module is used to conduct static cone penetration tests on the seabed strata required for steel pipe pile foundations, obtain experimental data at each depth test point in the static cone penetration test, normalize the experimental data point by point, classify soil behavior types based on the normalization results, and invert the mechanical parameters of soil layers of each soil behavior type. Static bearing capacity calculation module: used to calculate the side friction resistance between the steel pipe pile body and the surrounding soil and the end resistance of the pile end based on the soil mechanical parameters of each soil behavior type, so as to obtain the initial static ultimate bearing capacity of the steel pipe pile under ideal static conditions. Time-varying reduction factor calculation module: used to obtain historical equivalent cyclic load experimental data of waves in the sea area where steel pipe piles are constructed, construct equivalent cyclic load reduction factor, liquefaction reduction factor and time-varying corrosion reduction factor, and construct comprehensive time-varying reduction factor through multi-mechanism coupling; Time-varying bearing capacity prediction module: used to correct the initial static ultimate bearing capacity of steel pipe piles based on the comprehensive time-varying reduction coefficient, predict the vertical bearing capacity of steel pipe piles during long-term service, and obtain the time-varying ultimate bearing capacity of steel pipe piles; Safety level assessment module: used to set the bearing capacity assessment threshold based on the time-varying ultimate bearing capacity, dynamically adjust the bearing capacity grading threshold range, match the time-varying ultimate bearing capacity with the dynamic bearing capacity grading threshold range, and output the grading evaluation result for the vertical bearing capacity to be estimated for the steel pipe pile.

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