Multi-index determination method and device for applicable stratum of jacket suction pile foundation

Abstract

The application discloses a kind of multi-index determination method and device of jacket suction pile foundation applicable stratum, and relates to the technical field of ocean engineering.The method comprises the following steps: obtaining target site soil layer distribution data and suction pile design parameters; based on the principle of CPT static sounding, calculate the penetration resistance under different penetration depths; calculate available negative pressure and soil failure critical negative pressure; establish a multi-index comprehensive determination framework, while checking the penetration feasibility, soil stability and barrel buckling stability three indexes, when any index does not meet, parameter optimization or additional auxiliary sinking measures are carried out until all meet.The application overcomes the safety blind area of traditional single-index determination method, establishes a systematic multi-index joint determination system, can comprehensively evaluate the applicability of stratum, effectively prevent soil seepage failure and barrel buckling instability and other engineering risks, provides a scientific basis for offshore wind power suction pile foundation site selection and design, and has wide engineering practical value.

Description

Technical Field

[0001] This invention relates to the field of offshore wind power safety assessment technology, specifically to a multi-index method for determining the applicable geological formations for jacket suction cylinder foundations. Background Technology

[0002] With the global energy structure transformation and the advancement of "dual-carbon" goals, offshore wind power, as a clean and renewable energy source, has experienced rapid development. my country possesses vast sea areas and abundant wind energy resources, and its installed offshore wind power capacity continues to grow. The jacketed suction cylinder foundation (also known as a suction barrel foundation or suction anchor foundation), as a new type of offshore wind power foundation, has gained increasing attention and application in offshore wind power projects due to its advantages such as convenient installation, reusability, and minimal disturbance to the seabed. This foundation type uses a negative pressure sinking method to penetrate the cylinder into the seabed, forming a reliable anchored foundation, suitable for offshore wind farms in deep water.

[0003] The construction process of a suction cylinder foundation mainly includes two stages: the first stage relies on the structure's own weight to achieve initial mud penetration (self-weight mud penetration stage); the second stage uses a water pump at the top of the cylinder to create negative pressure inside, and utilizes the pressure difference between the negative pressure and the external water pressure to penetrate the cylinder to the design depth (negative pressure penetration stage). However, the feasibility of suction cylinder foundation penetration is highly dependent on the engineering geological characteristics of the seabed soil. Soil conditions vary significantly at different sites, including soil type (cohesive soil, sandy soil, and mixed soil layers), soil thickness, shear strength parameters, and permeability characteristics. These factors directly affect the magnitude of penetration resistance, the upper limit of usable negative pressure, and the stability of the soil under negative pressure.

[0004] Currently, the determination of suitable soil layers for suction cylinder foundations mainly relies on engineering experience or single-index evaluation methods. Traditional methods typically use penetration feasibility as the sole criterion, comparing the required negative pressure with the available negative pressure, neglecting the stability of the soil under negative pressure and the buckling stability of the cylinder structure itself. This single-index method has the following shortcomings: First, it does not consider the soil plugging effect and the risk of soil seepage failure, which may lead to engineering accidents such as soil liquefaction or piping during construction; second, it does not perform cylinder buckling verification, which may lead to structural instability under deep penetration or high negative pressure conditions; third, it lacks a systematic multi-index comprehensive evaluation framework, failing to provide comprehensive safety assurance for engineering design.

[0005] Therefore, there is an urgent need for a systematic, comprehensive, and reliable method for determining the applicable strata for jacket suction cylinder foundations, which can comprehensively evaluate multiple key indicators such as penetration feasibility, soil stability, and barrel buckling stability, and provide a scientific basis for the site selection and design of offshore wind turbine suction cylinder foundations. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a multi-index determination method and device for the applicable strata of jacket suction cylinder foundations. This method establishes a joint determination framework based on three core indicators: penetration feasibility, soil stability, and cylinder buckling stability. This enables a comprehensive and systematic evaluation of the suitability of the target site's strata, addressing the safety risks and engineering hazards inherent in existing single-index determination methods.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a multi-index method for determining the applicable strata for jacket suction cylinder foundations, including:

[0009] Obtain soil layer distribution data and suction cylinder foundation design parameters for the target site; the soil layer distribution data includes the thickness of each soil layer, buoyant unit weight, undrained shear strength or internal friction angle, and permeability coefficient; the suction cylinder foundation design parameters include the outer diameter of the cylinder, the cylinder wall thickness, the design penetration depth, and the cylinder height.

[0010] Based on the principle of static cone penetration test, the penetration process is divided into cohesive soil section and sandy soil section, and the penetration resistance at different penetration depths is calculated based on the obtained parameters.

[0011] Based on the acquired parameters and the penetration resistance, the required negative pressure Preq, the available negative pressure Pavail, and the critical negative pressure Pfail for soil failure are calculated.

[0012] Based on the acquired parameters and the required negative pressure, available negative pressure, and critical negative pressure for soil failure, a comprehensive judgment is made using multiple indicators; the multiple indicators include: penetration feasibility index, soil stability index, and barrel buckling stability index.

[0013] The penetration feasibility criteria include: the required negative pressure Preq is less than or equal to the available negative pressure Pavail, and the penetration feasibility safety factor SFp is greater than or equal to 1.15.

[0014] The soil stability index determination includes: the required negative pressure Preq is less than the critical negative pressure Pfail for soil failure, and the soil stability safety factor SFs is greater than or equal to 1.15;

[0015] The buckling stability index of the barrel is determined by the following criteria: the buckling UC value is less than or equal to 1.0, and the buckling safety factor is greater than or equal to 1.0.

[0016] When all three indicators are satisfied, the system outputs the penetration feasibility safety factor SFp, the soil stability safety factor SFs, the buckling safety factor, and the recommended design parameters. When any indicator is not satisfied, the system outputs the name of the unsatisfied indicator, the difference between the current value and the target value, and performs parameter optimization and re-evaluation until all three indicators are satisfied, and then outputs the recommended design parameters.

[0017] Preferably, the penetration resistance is calculated as follows:

[0018] Qd = Qf + Qp = f·As + q·Ap,

[0019] Where Qd is the penetration resistance, Qf is the total side friction resistance, f is the soil side friction resistance, As is the sidewall area, Qp is the total end resistance, q is the soil end resistance, and Ap is the end area.

[0020] The sidewall area As =π·Do·z, where z is the current penetration depth and Do is the outer diameter of the cylinder;

[0021] End area Ap = π·(Do) 2 - Di 2 ) / 4, where Di is the inner diameter of the cylinder.

[0022] Preferably, for cohesive soil sections, the side frictional resistance f of the soil layer is calculated using the α adhesion coefficient method:

[0023] f = α · Su,

[0024] Where α is the adhesion coefficient and Su is the undrained shear strength of the soil;

[0025] The soil end resistance q = Nc · Su, where Nc is the bearing capacity coefficient.

[0026] Preferably, for sandy soil sections, the soil side friction f is calculated using the bearing capacity coefficient method:

[0027] f = K · sigma_v' · tan(delta),

[0028] Where K is the earth pressure coefficient, sigma_v' is the effective overburden pressure, and delta is the wall friction angle;

[0029] Soil end resistance q = Nq · sigma_v', where Nq is the bearing capacity coefficient.

[0030] Preferably, the required negative pressure Preq is calculated as follows:

[0031] Preq = (Qd - Ws) / Ain,

[0032] Where Ws is the structural self-weight and Ain is the internal cross-sectional area of ​​the cylinder;

[0033] The available negative pressure Pavail is calculated as follows:

[0034] Pavail = min(gamma_w · h, Qa),

[0035] Where gamma_w is the unit weight of seawater, h is the water depth from the water surface to the top of the cylinder, and Qa is the soil's resistance to seepage damage.

[0036] For cohesive soil sections, the critical negative pressure Pfail for soil failure is determined according to the undrained failure criterion for cohesive soil, and is expressed as:

[0037] Pfail = Nc·Su +γ'·L,

[0038] Where Nc is the bearing capacity coefficient, Su is the undrained shear strength of the soil, and γ' is the buoyant unit weight of the soil;

[0039] For sandy soil sections, the critical negative pressure Pfail for soil failure is determined according to the seepage failure criterion, and is expressed as:

[0040] Pfail =γ'·h / (1 +γ' / (gamma_w·ic)) ,

[0041] Where: ic is the critical hydraulic gradient, ic = (Gs - 1) / (1 + e), where Gs is the specific gravity of soil particles and e is the void ratio.

[0042] Preferably, for cohesive soil sections, the soil's resistance to seepage failure, Qa, is calculated according to the DNV-RP-E303 standard and expressed as:

[0043] Qa= Nc·Su·Ain +π·Di·L·α·Su / Ain,

[0044] Where Di is the inner diameter of the cylinder, L is the penetration depth, and α is the adhesion coefficient;

[0045] For sandy soil sections, Qa is calculated according to seepage theory and expressed as:

[0046] Qa= γ'·h·Nq·(1 + (2·tanφ) / (3·Nq))·(1 + Di / (2·h)),

[0047] Where Nq is the bearing capacity coefficient and φ is the internal friction angle.

[0048] Preferably, the penetration feasibility safety factor is expressed as:

[0049] SFp = Pavail / Preq,

[0050] The soil stability safety factor is expressed as:

[0051] SFs = Pfail / Preq,

[0052] The buckling UC value is expressed as:

[0053] UC = fa / Fcr + (fb / Fb) 2 ,

[0054] Where fa is the axial compressive stress, Fcr is the critical buckling stress, fb is the bending stress, and Fb is the bending buckling stress.

[0055] The buckling safety factor is the reciprocal of the buckling UC value.

[0056] Preferably, the parameter optimization includes at least one of the following methods:

[0057] Adjusting the cylinder diameter, adjusting the penetration depth, adjusting the cylinder wall thickness, and adding auxiliary penetration measures include: water jet flushing auxiliary penetration, pre-drilling auxiliary penetration, and vibration auxiliary penetration.

[0058] Preferably, the soil layer distribution data is obtained through on-site CPT static cone penetration test, borehole sampling laboratory test, or geological survey report.

[0059] This invention also provides a multi-index determination device for the applicable strata of jacket foundation suction cylinder foundations, used to implement the above-mentioned multi-index determination method for the applicable strata of jacket foundation suction cylinder foundations, the device comprising:

[0060] The parameter acquisition module is used to acquire soil layer distribution data and suction cylinder foundation design parameters of the target site; the soil layer distribution data includes the thickness of each soil layer, buoyant unit weight, undrained shear strength or internal friction angle, and permeability coefficient; the suction cylinder foundation design parameters include cylinder outer diameter, cylinder wall thickness, design penetration depth, and cylinder height.

[0061] The penetration resistance calculation module is used to divide the penetration process into cohesive soil sections and sandy soil sections based on the static cone penetration principle, and calculate the penetration resistance at different penetration depths based on the acquired parameters.

[0062] The boundary condition calculation module is used to calculate the required negative pressure Preq, the available negative pressure Pavail, and the critical negative pressure Pfail for soil failure based on the acquired parameters and the penetration resistance.

[0063] The comprehensive judgment module is used to make a comprehensive judgment based on the acquired parameters and the required negative pressure, available negative pressure and critical negative pressure for soil failure; the multiple indicators include: penetration feasibility index, soil stability index and barrel buckling stability index.

[0064] The penetration feasibility criteria include: the required negative pressure Preq is less than or equal to the available negative pressure Pavail, and the penetration feasibility safety factor SFp is greater than or equal to 1.15.

[0065] The soil stability index determination includes: the required negative pressure Preq is less than the critical negative pressure Pfail for soil failure, and the soil stability safety factor SFs is greater than or equal to 1.15;

[0066] The buckling stability index of the barrel is determined by the following criteria: the buckling UC value is less than or equal to 1.0, and the buckling safety factor is greater than or equal to 1.0.

[0067] When all three indicators are satisfied, the system outputs the penetration feasibility safety factor SFp, the soil stability safety factor SFs, the buckling safety factor, and the recommended design parameters. When any indicator is not satisfied, the system outputs the name of the unsatisfied indicator, the difference between the current value and the target value, and performs parameter optimization and re-evaluation until all three indicators are satisfied, and then outputs the recommended design parameters.

[0068] The beneficial effects of this invention include:

[0069] (1) The present invention establishes differentiated calculation models for penetration resistance and boundary conditions for cohesive soil and sandy soil, which can meet the applicability evaluation needs of sites with different geological conditions along the coast of my country and has wide applicability and engineering practical value.

[0070] (2) The present invention introduces a parameter optimization feedback mechanism. When the initial design parameters do not meet the judgment index, it can automatically give parameter adjustment suggestions and auxiliary measures, providing an iterative optimization technical path for engineering design and improving design efficiency and engineering economy.

[0071] (3) This invention establishes a systematic multi-index joint judgment framework, which incorporates the three core indicators of penetration feasibility, soil stability and barrel buckling stability into a unified evaluation system, overcomes the safety blind spot of traditional single index judgment methods, and significantly improves the comprehensiveness and reliability of the formation applicability evaluation.

[0072] (4) The method of the present invention has a clear process and clear calculation steps. Each indicator has a clear safety factor threshold, which is easy for engineering technicians to understand and apply, and is conducive to its promotion and use in the offshore wind power industry. Attached Figure Description

[0073] Figure 1 A schematic diagram of the process for determining the applicable underlying multi-index method for the duct stent foundation provided by the present invention;

[0074] Figure 2 This is a schematic diagram of the cylinder foundation penetration principle in an embodiment of the present invention;

[0075] Figure 3 The curves showing the required negative pressure and available negative pressure as a function of penetration depth in this embodiment of the invention (ZK04 point).

[0076] Figure 4 This is a simplified diagram of buckling calculation in an embodiment of the present invention;

[0077] Figure 5 This is a columnar section of the soil layer at point ZK04 and a schematic diagram of the design parameters of the suction cylinder in an embodiment of the present invention. Detailed Implementation

[0078] 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 embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0079] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0080] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0081] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0082] In the following description, embodiments of the invention will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar parts, or the same or similar steps.

[0083] It should be emphasized here that the step markers mentioned below are not a limitation on the order of the steps, but should be understood as meaning that the steps can be executed in the order mentioned in the embodiments, or in a different order than in the embodiments, or several steps can be executed simultaneously.

[0084] Example 1

[0085] like Figure 1 As shown in Embodiment 1, this method provides a multi-index determination method for the applicable strata of a jacket suction cylinder foundation, including the following steps:

[0086] Step S1, Data Input: Obtain soil layer distribution data and suction cylinder foundation design parameters for the target site.

[0087] The soil layer distribution data includes parameters such as the thickness of each soil layer, buoyant unit weight, undrained shear strength or internal friction angle, and permeability coefficient. The suction cylinder foundation design parameters include the cylinder outer diameter Do, cylinder wall thickness t, design penetration depth L, and cylinder height H. Soil layer distribution data can be obtained through on-site CPT static cone penetration tests, borehole sampling laboratory tests, or existing geological survey reports.

[0088] Taking a certain offshore wind farm in my country as an example, the site is located in the East China Sea, with a water depth of approximately 10 meters. Soil layer distribution data from borehole ZK04 was obtained through on-site geological surveys, such as... Figure 5 As shown. The soil layer distribution from the seabed downwards at point ZK04 is as follows:

[0089] First layer: silty clay, bottom depth 4.5m, undrained shear strength Su = 18.7kPa, buoyant unit weight = 7.64kN / m³ 3 ;

[0090] Second layer: silty clay interbedded with silty sand, bottom depth 7.2m, undrained shear strength Su = 18.7kPa, buoyant unit weight = 9.5kN / m³ 3 ;

[0091] The third layer consists of silty clay interbedded with pebbles, with a bottom depth of 16.6m. Its undrained shear strength Su = 35.0kPa and buoyant unit weight = 10.5kN / m³. 3 .

[0092] The design parameters for the suction cylinder foundation are: outer diameter Do = 9.5m, wall thickness t = 25mm, design penetration depth L = 8.8m, and cylinder height H = 8.5m. The inner diameter Di = Do - 2t = 9.45m, and the internal cross-sectional area Ain = π·Di. 2 / 4 = 70.12m 2 .

[0093] Step S2, Penetration Resistance Calculation: Based on the CPT (Cone Penetration Test) static cone penetration principle, the penetration process is divided into cohesive soil section and sandy soil section, and the penetration resistance Qd at different penetration depths is calculated respectively.

[0094] like Figure 2 As shown, during the penetration of the suction cylinder, a side frictional resistance f is generated between the cylinder wall and the surrounding soil, and an end resistance q is generated between the cylinder end and the soil below. The penetration resistance Qd is the sum of the side frictional resistance and the end resistance, expressed as:

[0095] Qd = Qf + Qp = f·As + q·Ap (1)

[0096] In the formula: Qf is the total side friction resistance, f is the side friction resistance of the soil layer (kPa), and As is the sidewall area (m²). 2 Qp is the total end resistance, q is the soil end resistance (kPa), and Ap is the end area (m²). 2 For cohesive soils, the side friction resistance is calculated using the α coefficient method, and the end resistance is calculated using the bearing capacity coefficient method; for sandy soils, the side friction resistance is calculated using the earth pressure coefficient method, and the end resistance is calculated using the bearing capacity coefficient method.

[0097] For the cohesive soil layer in this embodiment, the side friction resistance is calculated using the α adhesion coefficient method:

[0098] f = α · Su (2)

[0099] In the formula: α is the adhesion coefficient, which, according to the DNV-RP-E303 specification, is α = min(1.0, 0.5· Su / sigma_v'), where sigma_v' is the effective overburden pressure.

[0100] The formula for calculating end resistance is:

[0101] q = Nc · Su (3)

[0102] In the formula: Nc is the bearing capacity coefficient, which ranges from 5 to 9. In this embodiment, Nc = 7.5 is taken.

[0103] The sidewall area As = π·Do·z, where z is the current penetration depth.

[0104] End area Ap = π·(Do) 2 - Di 2 ) / 4.

[0105] Taking a penetration depth of z = 8.8m as an example, at this point the cylinder wall passes through the first layer (4.5m thick) and the second layer (2.7m thick), and enters the third layer 1.6m deep.

[0106] The side friction resistances of each layer are as follows: first layer f1 = 0.5·18.7 = 9.35kPa, second layer f2 = 0.5·18.7 = 9.35kPa, third layer f3 = 0.5·35.0 = 17.5kPa.

[0107] Total side friction resistance: Qf=π·Do·(f1·4.5 + f2·2.7 + f3·1.6) = 3.14·9.5·(9.35·4.5 +9.35·2.7 + 17.5·1.6) = 3294.6kN.

[0108] Total end resistance Qp = Nc ·Su·Ap = 7.5·35.0·0.371 = 97.4kN.

[0109] The penetration resistance Qd = Qf + Qp = 3294.6 + 97.4 = 3392.0kN.

[0110] Step S3, Boundary Condition Calculation: The calculation can use negative pressure Pavail and critical negative pressure Pfail for soil failure.

[0111] The negative pressure Pavail can be taken as the smaller value between the negative pressure provided by the hydrostatic pressure and the soil's resistance to seepage failure, Qa, and expressed as:

[0112] Pavail = min(gamma_w · h, Qa) (4)

[0113] In the formula: gamma_w is the bulk density of seawater (kN / m3), h is the water depth from the water surface to the top of the cylinder (m), and Qa is the soil's resistance to seepage failure (kPa).

[0114] For cohesive soil, Qa is calculated according to the DNV-RP-E303 standard: Qa = Nc·Su·Ain +π·Di·L·α·Su / Ain, where Di is the inner diameter of the cylinder, L is the penetration depth, α is the adhesion coefficient, Su is the undrained shear strength, and Ain is the cross-sectional area inside the cylinder.

[0115] For sandy soil, Qa is calculated according to the seepage theory: Qa = γ'·h·Nq·(1 + (2·tanφ) / (3·Nq))·(1 + Di / (2·h)), where γ' is the buoyant unit weight of the soil, Nq is the bearing capacity coefficient, φ is the internal friction angle, and Di is the inner diameter of the cylinder.

[0116] The critical negative pressure Pfail for soil failure is determined according to the soil type, either by the undrained failure criterion for cohesive soil or the seepage failure criterion for sandy soil.

[0117] In this embodiment, the negative pressure provided by hydrostatic pressure is gamma_w · h = 10.25 · 10 = 102.5 kPa. For cohesive soil, the soil's resistance to seepage failure, Qa, is calculated according to the DNV-RP-E303 standard:

[0118] Qa = Nc·Su·Ain +π·Di·L·α·Su / Ain (5)

[0119] Calculations show that Qa = 123 kPa at a penetration depth of 8.8 m. Therefore, a negative pressure of Pavail = min(102.5, 123) = 102.5 kPa can be applied.

[0120] The critical negative pressure Pfail for soil failure is determined according to the undrained failure criterion for cohesive soils. According to DNV-RP-E303, the critical negative pressure for soil plug failure is:

[0121] Pfail = Nc·Su +γ'·L (6)

[0122] Calculations show that when the penetration depth is 8.8m, Pfail = 7.5·35.0 + 10.5·8.8 = 354.9kPa.

[0123] Step S4: Comprehensive judgment based on multiple indicators:

[0124] Indicator A – Feasibility Verification of Implementation:

[0125] The required negative pressure Preq is less than or equal to the available negative pressure Pavail, and the penetration feasibility safety factor SFp = Pavail / Preq >= 1.15. The formula for calculating the required negative pressure is:

[0126] Preq = (Qd - Ws) / Ain (7)

[0127] In the formula: Qd is the penetration resistance (kN), Ws is the structural self-weight (kN), and Ain is the internal cross-sectional area of ​​the cylinder (m²). 2 ).

[0128] In this embodiment, the required negative pressure Preq = (Qd - Ws) / Ain = (3392.0 - 2150.0) / 70.12 = 17.7 kPa (Note: The structural self-weight Ws is the sum of the self-weights of the suction cylinder and the guide frame, and is determined according to the actual design value).

[0129] The penetration feasibility safety factor SFp = Pavail / Preq = 102.5 / 17.7 = 5.79 >= 1.15, which meets the penetration feasibility requirements.

[0130] like Figure 3 The figure shows the relationship between the required negative pressure Preq and the available negative pressure Pavail at point ZK04 as a function of penetration depth. It can be seen from the figure that throughout the entire penetration depth range, the available negative pressure Pavail is always greater than the required negative pressure Preq, indicating sufficient safety margin for penetration feasibility.

[0131] Index B – Soil stability check:

[0132] The required negative pressure Preq is less than the critical negative pressure Pfail for soil failure, and the soil stability safety factor SFs = Pfail / Preq >= 1.15. This indicator ensures that the negative pressure applied during penetration will not cause soil failure, preventing engineering accidents such as soil plug heave or seepage failure.

[0133] In this embodiment, the soil stability safety factor SFs = Pfail / Preq = 354.9 / 17.7 = 20.05 >= 1.15, which meets the soil stability requirements. This result indicates that the negative pressure applied during penetration is much smaller than the critical negative pressure for soil failure, and the soil will not experience seepage failure or soil plug heave.

[0134] Index C – Buckle buckling stability check:

[0135] Buckling verification was performed according to the API Bulletin 2U specification, with a buckling UC value <= 1.0 and a buckling safety factor >= 1.0. This specification ensures that the tank will not buckle instability under negative pressure.

[0136] like Figure 4 As shown, in this embodiment, buckling verification is performed according to the API Bulletin 2U specification. The buckling calculation length is the sum of the length from above the mud surface to the top of the cylinder and the length from below the mud surface to the bottom of the cylinder. The portion above the mud surface is calculated as a compression member with hinged ends, and the portion below the mud surface is considered as having no lateral constraints.

[0137] The buckling UC value is calculated using the following formula:

[0138] UC = fa / Fcr + (fb / Fb) 2 <= 1.0 (8)

[0139] In the formula: fa is the axial compressive stress (MPa), Fcr is the critical buckling stress (MPa), fb is the bending stress (MPa), and Fb is the bending buckling stress (MPa).

[0140] Calculations show that under the maximum required negative pressure condition, the buckling UC value is 0.357 <= 1.0, and the buckling safety factor is 1 / 0.357 = 2.80 >= 1.0, which meets the buckling stability requirements.

[0141] Overall judgment conclusion:

[0142] When all three indicators are met, the output includes the penetration feasibility safety factor SFp, the soil stability safety factor SFs, the buckling safety factor, and recommended design parameters. When any indicator is not met, the output includes the name of the unmet indicator, the difference between the current value and the target value, and optimization suggestions.

[0143] In addition, if any indicator is not met, adjust the design parameters of the suction cylinder (such as cylinder diameter, wall thickness, penetration depth, etc.) or add auxiliary penetration measures (such as water jet flushing, pre-drilling, vibration assistance, etc.), and repeat steps S2 to S4 until all three indicators are met.

[0144] In this embodiment, all three indicators meet the requirements, and the strata at point ZK04 are suitable for jacket suction cylinder foundations. The specific judgment results are summarized in Table 1 below:

[0145] Table 1 Summary of Multi-Indicator Judgment Results for ZK04 Location

[0146] Penetration Feasibility SFp = 5.79 >= 1.15 satisfy Soil stability SFs = 20.05 >= 1.15 satisfy Bucket buckling stability UC = 0.357 <= 1.0 satisfy Comprehensive judgment -- -- Applicable

[0147] Example 2

[0148] For sandy soil strata, this embodiment 2 makes corresponding adjustments to the calculation model in steps S2 and S3 of the method of the present invention.

[0149] In step S2, the side friction resistance of the sandy soil section is calculated using the bearing capacity coefficient method:

[0150] f = K · sigma_v' · tan(delta) (9)

[0151] In the formula: K is the earth pressure coefficient, taken as K = 0.8; sigma_v' is the effective overburden pressure (kPa); delta is the wall friction angle, taken as delta = φ.

[0152] The formula for calculating end resistance is:

[0153] q = Nq · sigma_v' (10)

[0154] In the formula: Nq is the bearing capacity coefficient, which is determined according to the API specification.

[0155] In step S3, the seepage resistance capacity Qa of the sandy soil is calculated using the Houlsby and Byrne method:

[0156] Qa =γ'·h·Nq·(1 + 2tan(φ) / (3Nq))·(1 + Di / (2h)) (11)

[0157] In the formula: γ' is the buoyant unit weight of the soil (kN / m3), Nq is the bearing capacity coefficient, φ is the internal friction angle, and Di is the inner diameter of the cylinder (m).

[0158] The critical negative pressure Pfail for soil failure in sandy soil is determined according to the seepage failure criterion, that is, seepage failure occurs when the hydraulic gradient exceeds the critical hydraulic gradient:

[0159] Pfail =γ'·h / (1 +γ' / (gamma_w·ic)) (12)

[0160] In the formula: ic is the critical hydraulic gradient, ic = (Gs - 1) / (1 + e), where Gs is the specific gravity of soil particles and e is the void ratio.

[0161] Through the aforementioned differentiated calculation model, this embodiment can meet the applicability evaluation needs of sites with different geological conditions along my country's coast, including common cohesive soil, sandy soil, and mixed soil layers in the East China Sea and South China Sea.

[0162] Example 3

[0163] When the initial design parameters do not meet the judgment criteria, step S5 of the method of this invention provides a parameter optimization path. In this embodiment 3, taking a certain site as an example, if the penetration feasibility safety factor SFp < 1.15, it indicates that the available negative pressure is insufficient to overcome the penetration resistance, and the following optimization measures can be taken:

[0164] (1) Increase cylinder diameter Do: Increasing the cylinder diameter can increase the depth of the slurry under its own weight, and at the same time increase the cross-sectional area Ain inside the cylinder, reducing the required negative pressure Preq. However, it should be noted that increasing the cylinder diameter will also increase the structural self-weight and material cost.

[0165] (2) Reduce the penetration depth L: Appropriately reducing the design penetration depth can reduce the total penetration resistance Qd, but it is necessary to ensure that the bearing capacity requirements are met.

[0166] (3) Add auxiliary penetration measures: including water jet flushing auxiliary penetration (by setting water jet pipes on the inner side of the cylinder wall to reduce side friction resistance), pre-drilling auxiliary penetration (by pre-drilling holes at the cylinder foundation location to reduce end resistance), and vibration auxiliary penetration (by using vibration equipment to assist the cylinder penetration).

[0167] (4) Increase wall thickness t: If the buckling safety factor does not meet the requirements, the buckling resistance of the barrel can be improved by increasing the wall thickness.

[0168] Through iterative optimization, until all three indicators are met, the recommended design parameters and judgment conclusions are finally output.

[0169] Example 4

[0170] Based on the above inventive concept, this embodiment 4 provides a multi-index determination device for the applicable strata of the jacket suction cylinder foundation, used to implement the multi-index determination method for the applicable strata of the jacket suction cylinder foundation in the above embodiment. The device includes:

[0171] The parameter acquisition module is used to acquire soil layer distribution data and suction cylinder foundation design parameters of the target site; the soil layer distribution data includes the thickness of each soil layer, buoyant unit weight, undrained shear strength or internal friction angle, and permeability coefficient; the suction cylinder foundation design parameters include cylinder outer diameter, cylinder wall thickness, design penetration depth, and cylinder height.

[0172] The penetration resistance calculation module is used to divide the penetration process into cohesive soil sections and sandy soil sections based on the static cone penetration principle, and calculate the penetration resistance at different penetration depths based on the acquired parameters.

[0173] The boundary condition calculation module is used to calculate the required negative pressure Preq, the available negative pressure Pavail, and the critical negative pressure Pfail for soil failure based on the acquired parameters and the penetration resistance.

[0174] The comprehensive judgment module is used to make a comprehensive judgment based on the acquired parameters and the required negative pressure, available negative pressure and critical negative pressure for soil failure; the multiple indicators include: penetration feasibility index, soil stability index and barrel buckling stability index.

[0175] The penetration feasibility criteria include: the required negative pressure Preq is less than or equal to the available negative pressure Pavail, and the penetration feasibility safety factor SFp is greater than or equal to 1.15.

[0176] The soil stability index determination includes: the required negative pressure Preq is less than the critical negative pressure Pfail for soil failure, and the soil stability safety factor SFs is greater than or equal to 1.15;

[0177] The buckling stability index of the barrel is determined by the following criteria: the buckling UC value is less than or equal to 1.0, and the buckling safety factor is greater than or equal to 1.0.

[0178] When all three indicators are satisfied, the system outputs the penetration feasibility safety factor SFp, the soil stability safety factor SFs, the buckling safety factor, and the recommended design parameters. When any indicator is not satisfied, the system outputs the name of the unsatisfied indicator, the difference between the current value and the target value, and performs parameter optimization and re-evaluation until all three indicators are satisfied, and then outputs the recommended design parameters.

[0179] It is worth noting that this device embodiment corresponds to the above method embodiment. The implementation methods of the above method embodiments are all applicable to this device embodiment and can achieve the same or similar technical effects, so they will not be described in detail here.

[0180] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0181] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0182] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0183] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A multi-index determination method for applicable strata of jacket foundation suction cylinder foundation, characterized in that, include: Obtain soil layer distribution data and suction cylinder foundation design parameters for the target site; the soil layer distribution data includes the thickness of each soil layer, buoyant unit weight, undrained shear strength or internal friction angle, and permeability coefficient; the suction cylinder foundation design parameters include the outer diameter of the cylinder, the cylinder wall thickness, the design penetration depth, and the cylinder height. Based on the principle of static cone penetration test, the penetration process is divided into cohesive soil section and sandy soil section, and the penetration resistance at different penetration depths is calculated based on the obtained parameters. Based on the acquired parameters and the penetration resistance, the required negative pressure Preq, the available negative pressure Pavail, and the critical negative pressure Pfail for soil failure are calculated. Based on the acquired parameters and the required negative pressure, available negative pressure, and critical negative pressure for soil failure, a comprehensive judgment is made using multiple indicators; the multiple indicators include: penetration feasibility index, soil stability index, and barrel buckling stability index. The penetration feasibility criteria include: the required negative pressure Preq is less than or equal to the available negative pressure Pavail, and the penetration feasibility safety factor SFp is greater than or equal to 1.

15. The soil stability index determination includes: the required negative pressure Preq is less than the critical negative pressure Pfail for soil failure, and the soil stability safety factor SFs is greater than or equal to 1.15; The buckling stability index of the barrel is determined by the following criteria: the buckling UC value is less than or equal to 1.0, and the buckling safety factor is greater than or equal to 1.

0. When all three indicators are satisfied, the system outputs the penetration feasibility safety factor SFp, the soil stability safety factor SFs, the buckling safety factor, and the recommended design parameters. When any indicator is not satisfied, the system outputs the name of the unsatisfied indicator, the difference between the current value and the target value, and performs parameter optimization and re-evaluation until all three indicators are satisfied, and then outputs the recommended design parameters.

2. The multi-index determination method for applicable strata of a jacket suction cylinder foundation according to claim 1, characterized in that, The penetration resistance is calculated as follows: Qd = Qf + Qp = f·As + q·Ap, Where Qd is the penetration resistance, Qf is the total side friction resistance, f is the soil side friction resistance, As is the sidewall area, Qp is the total end resistance, q is the soil end resistance, and Ap is the end area. The sidewall area As =π·Do·z, where z is the current penetration depth and Do is the outer diameter of the cylinder; End area Ap = π·(Do) 2 - Di 2 ) / 4, where Di is the inner diameter of the cylinder.

3. The multi-index determination method for applicable strata of a jacket suction cylinder foundation according to claim 2, characterized in that, For the cohesive soil section, the side frictional resistance f of the soil layer is calculated using the α adhesion coefficient method: f = α · Su, Where α is the adhesion coefficient and Su is the undrained shear strength of the soil; The soil end resistance q = Nc · Su, where Nc is the bearing capacity coefficient.

4. The multi-index determination method for applicable strata of a jacketed tube suction cylinder foundation according to claim 2, characterized in that, For the sandy soil section, the side frictional resistance f of the soil layer is calculated using the bearing capacity coefficient method: f = K · sigma_v' · tan(delta), Where K is the earth pressure coefficient, sigma_v' is the effective overburden pressure, and delta is the wall friction angle; Soil end resistance q = Nq · sigma_v', where Nq is the bearing capacity coefficient.

5. The multi-index determination method for applicable strata of a jacket suction cylinder foundation according to claim 2, characterized in that, The required negative pressure Preq is calculated as follows: Preq = (Qd - Ws) / Ain, Where Ws is the structural self-weight and Ain is the internal cross-sectional area of ​​the cylinder; The available negative pressure Pavail is calculated as follows: Pavail = min(gamma_w · h, Qa), Where gamma_w is the unit weight of seawater, h is the water depth from the water surface to the top of the cylinder, and Qa is the soil's resistance to seepage damage. For cohesive soil sections, the critical negative pressure Pfail for soil failure is determined according to the undrained failure criterion for cohesive soil, and is expressed as: Pfail = Nc·Su +γ'·L, Where Nc is the bearing capacity coefficient, Su is the undrained shear strength of the soil, and γ' is the buoyant unit weight of the soil; For sandy soil sections, the critical negative pressure Pfail for soil failure is determined according to the seepage failure criterion, and is expressed as: Pfail =γ'·h / (1 +γ' / (gamma_w·ic)) , Where: ic is the critical hydraulic gradient, ic = (Gs - 1) / (1 + e), where Gs is the specific gravity of soil particles and e is the void ratio.

6. The multi-index determination method for applicable strata of a jacket suction cylinder foundation according to claim 5, characterized in that, For cohesive soil sections, the soil's resistance to seepage failure, Qa, is calculated according to the DNV-RP-E303 standard and expressed as follows: Qa= Nc·Su·Ain +π·Di·L·α·Su / Ain, Where Di is the inner diameter of the cylinder, L is the penetration depth, and α is the adhesion coefficient; For sandy soil sections, Qa is calculated according to seepage theory and expressed as: Qa= γ'·h·Nq·(1 + (2·tanφ) / (3·Nq))·(1 + Di / (2·h)), Where Nq is the bearing capacity coefficient and φ is the internal friction angle.

7. The multi-index determination method for applicable strata of a jacket suction cylinder foundation according to claim 5, characterized in that, The penetration feasibility safety factor is expressed as: SFp = Pavail / Preq, The soil stability safety factor is expressed as: SFs = Pfail / Preq, The buckling UC value is expressed as: UC = fa / Fcr + (fb / Fb) 2 , Where fa is the axial compressive stress, Fcr is the critical buckling stress, fb is the bending stress, and Fb is the bending buckling stress. The buckling safety factor is the reciprocal of the buckling UC value.

8. The multi-index determination method for applicable strata of a jacket suction cylinder foundation according to claim 1, characterized in that, The parameter optimization includes at least one of the following methods: Adjusting the cylinder diameter, adjusting the penetration depth, adjusting the cylinder wall thickness, and adding auxiliary penetration measures include: water jet flushing auxiliary penetration, pre-drilling auxiliary penetration, and vibration auxiliary penetration.

9. The multi-index determination method for applicable strata of a jacket suction cylinder foundation according to claim 1, characterized in that, The soil layer distribution data were obtained through on-site CPT static cone penetration tests, borehole sampling laboratory tests, or geological survey reports.

10. A multi-index determination device for applicable strata of a jacket foundation suction cylinder foundation, characterized in that, The apparatus for implementing the multi-index determination method for applicable geological formations of the jacket suction cylinder foundation according to any one of claims 1 to 9, the apparatus comprising: The parameter acquisition module is used to acquire soil layer distribution data and suction cylinder foundation design parameters of the target site; the soil layer distribution data includes the thickness of each soil layer, buoyant unit weight, undrained shear strength or internal friction angle, and permeability coefficient; the suction cylinder foundation design parameters include cylinder outer diameter, cylinder wall thickness, design penetration depth, and cylinder height. The penetration resistance calculation module is used to divide the penetration process into cohesive soil sections and sandy soil sections based on the static cone penetration principle, and calculate the penetration resistance at different penetration depths based on the acquired parameters. The boundary condition calculation module is used to calculate the required negative pressure Preq, the available negative pressure Pavail, and the critical negative pressure Pfail for soil failure based on the acquired parameters and the penetration resistance. The comprehensive judgment module is used to make a comprehensive judgment based on the acquired parameters and the required negative pressure, available negative pressure and critical negative pressure for soil failure; the multiple indicators include: penetration feasibility index, soil stability index and barrel buckling stability index. The penetration feasibility criteria include: the required negative pressure Preq is less than or equal to the available negative pressure Pavail, and the penetration feasibility safety factor SFp is greater than or equal to 1.

15. The soil stability index determination includes: the required negative pressure Preq is less than the critical negative pressure Pfail for soil failure, and the soil stability safety factor SFs is greater than or equal to 1.15; The buckling stability index of the barrel is determined by the following criteria: the buckling UC value is less than or equal to 1.0, and the buckling safety factor is greater than or equal to 1.

0. When all three indicators are satisfied, the system outputs the penetration feasibility safety factor SFp, the soil stability safety factor SFs, the buckling safety factor, and the recommended design parameters. When any indicator is not satisfied, the system outputs the name of the unsatisfied indicator, the difference between the current value and the target value, and performs parameter optimization and re-evaluation until all three indicators are satisfied, and then outputs the recommended design parameters.

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