A method for evaluating deformation characteristics of marine soft soil based on disturbance state concept

Abstract

The present application relates to geotechnical engineering technical field, provide a kind of marine soft soil deformation characteristic evaluation method based on disturbance state concept, comprising the following steps: step 1, construct the constitutive model based on disturbance state concept;Step 2, based on indoor test data acquisition marine soft soil's natural physical mechanics parameters;Step 3, based on natural physical mechanics parameters, simulates the disturbance process of marine soft soil layer to engineering construction construction in steps, and extraction calculation variable in the simulation process of each stratum unit;Step 4, potential damage unit in each stratum is identified using double threshold value damage determination method;Step 5, based on the spatial distribution of all potential damage units, generate stratum damage distribution nephogram, realize the visual identification and zoning of engineering risk area.This scheme constructs the coupling criterion between structural evolution, energy dissipation and plastic deformation, and realizes the quantitative identification and risk zoning of potential damage area and key deformation zone in soft soil layer.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, specifically to a method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state. Background Technology

[0002] Marine soft soils are widely distributed along my country's coastal areas and possess engineering properties such as naturally high void ratio, high water content, low shear strength, high compressibility, and significant structural characteristics. In major engineering projects such as urban rail transit, cross-sea channels, deep foundation pits, and underground space development, marine soft soils serve as crucial engineering media, and their mechanical behavior and stability directly affect the safety and sustainability of the projects. However, when subjected to external disturbances (such as tunneling, foundation pit excavation, and load application), the structural integrity of marine soft soils is easily disrupted, leading to complex responses such as strength attenuation, enhanced shear dilatation, pore pressure accumulation, and abrupt deformation. This can easily result in engineering defects such as ground deformation instability, surrounding rock failure, and damage to support structures.

[0003] Existing methods for evaluating the deformation of marine soft soil are mostly based on traditional elastoplastic theory or empirical criteria, and usually use stress-strain curves, cumulative plastic strain, shear modulus degradation and other indicators to analyze deformation characteristics. However, these methods often have the following shortcomings: (1) They lack a systematic characterization of the soil structural degradation process caused by disturbance, and cannot accurately reflect the coupling relationship between soil mechanical parameters and structural evolution; (2) They are difficult to distinguish between reversible and irreversible stages of deformation, and cannot identify key damage units or potential risk areas; (3) Most methods rely on engineering experience or a single physical quantity, and the evaluation results are highly subjective and have poor timeliness, making it difficult to meet the needs of refined deformation prediction and control under complex geological conditions and construction disturbances.

[0004] The Disturbance State Concept (DSC), initially proposed by Desai, introduces a disturbance factor to describe the continuous damage process within a material's internal structure. It is characterized by its clear physical meaning and ease of numerical implementation. This theory combines structural changes in materials with stress-strain response and energy dissipation mechanisms, effectively simulating the strain softening, strength loss, and deformation development of marine soft soils under disturbance. However, a systematic method for identifying the engineering disturbance response and determining deformation zones of marine soft soils based on DSC has yet to be developed, and its application in numerical simulation and engineering risk control remains in its early stages.

[0005] Therefore, it is urgent to propose an evaluation method for the deformation characteristics of marine soft soil based on the concept of disturbance state. By combining energy dissipation analysis and plastic strain criteria, a scientific deformation identification mechanism and evaluation process should be established to realize dynamic tracking of disturbance response of marine soft soil, identification of key units and classification of risk levels, so as to provide new theoretical and technical support for engineering design, construction control and disaster early warning. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention proposes an evaluation method for deformation characteristics of marine soft soil based on the concept of disturbance state. It constructs a coupled criterion between structural evolution, energy dissipation and plastic deformation, and realizes the quantitative identification and risk zoning of potential damage areas and key deformation zones in soft soil strata.

[0007] To achieve the above objectives, the present invention adopts the following solution:

[0008] A method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state includes the following steps:

[0009] Step 1: Construct a constitutive model based on the concept of perturbation state. The constitutive model characterizes the structural continuous evolution process of soil from a relatively intact state to a fully adjusted state through a perturbation function. The relatively intact state and the fully adjusted state are two extreme special cases of the constitutive model.

[0010] Step 2: Obtain the natural physical and mechanical parameters of marine soft soil based on indoor test data of marine soft soil samples;

[0011] Step 3: Input the natural physical and mechanical parameters into the constitutive model based on the concept of disturbance state constructed in Step 1, simulate the disturbance process of marine soft soil strata caused by engineering construction step by step, and extract the calculation variables of each stratum unit in the simulation process;

[0012] Step 4: Based on the calculated variables, identify potential damage units in each stratum using a dual-threshold damage determination method;

[0013] Step 5: Based on the spatial distribution of all potential damage units, generate a formation damage distribution cloud map to achieve visual identification and zoning of engineering risk areas.

[0014] Optionally, the calculation program in step 1 is written in Python. The method for constructing a constitutive model based on the concept of perturbation states includes the following steps:

[0015] Step 1.1: Obtain the incremental matrix equation of the constitutive model in the relatively complete state based on the Duncan-Zhang model. The formula is as follows:

[0016]

[0017] In the formula, The strain represents the volumetric strain in a relatively intact state. Shear strain in a relatively intact state; Represented as 1 / K , K These are parameters related to the initial elastic modulus; Defined as zero or a partial derivative, it is used to reflect the dependence of volumetric strain on changes in deviatoric stress; The default value is 0, which is used to represent the dependence of shear strain on the change of average effective stress; 1 / G , G Shear modulus; For the effective average stress increment; This represents the increment of shear stress.

[0018] Step 1.2: Obtain the incremental matrix equation of the constitutive model under the fully adjusted state based on the modified Cambridge model. Its formula is as follows:

[0019]

[0020] In the formula, For the body strain of the fully adjusted state; The shear strain is for a fully adjusted state; The compression factor is 1. The strain coefficient of the elastic body;

[0021] Step 1.3: Based on the perturbation parameters obtained from experiments, construct perturbation functions for volumetric strain and shear strain to describe the evolution of the material from a relatively intact state to a fully adjusted state. The formula is as follows:

[0022]

[0023] In the formula, The void ratio of marine soft soil in a relatively intact state; This represents the void ratio of marine soft soil under actual conditions. To fully adjust the void ratio of marine soft soil under the current condition; The perturbation function for volumetric strain; Let be the perturbation function for shear strain; This represents the shear strain under actual conditions.

[0024] Step 1.4: Based on the perturbation functions of the volumetric strain and shear strain, obtain the expressions for the volumetric strain increment and shear strain increment matrices, and construct a constitutive model based on the concept of perturbation state. The mathematical expressions for the volumetric strain increment and shear strain increment matrices are as follows:

[0025]

[0026] In the formula, , .

[0027] Optionally, in step 1.1,

[0028] The expression for the volumetric strain increment of the constitutive model in a relatively intact state is as follows:

[0029]

[0030] In the formula, The tangent modulus calculated in the Duncan-Chang model. Poisson's ratio, This is the maximum principal stress;

[0031] The expression for the shear strain increment of the constitutive model in the relatively intact state is as follows:

[0032]

[0033] In the formula, This represents the shear stress increment.

[0034] Optionally, in step 1.2, the expression for the volumetric strain increment of the constitutive model in the fully adjusted state is:

[0035]

[0036] In the formula, This represents the elastic volumetric strain increment; This represents the plastic volumetric strain increment; The average effective stress; The initial void ratio;

[0037] The expression for the shear strain increment of the constitutive model under the fully adjusted state is as follows:

[0038]

[0039] In the formula, The shear strain is for a fully adjusted state; This represents the current effective stress. Equivalent Young's modulus; This represents the critical stress ratio.

[0040] Optionally, in step 1.3, the Mechanical parameters were obtained through isotropic consolidation creep tests, among which...

[0041]

[0042] In the formula, The initial void ratio of marine soft soil in its natural state; The strain coefficient of the elastic body in a relatively intact state; The strain coefficient of the elastic body under fully adjusted conditions; The compression coefficient of marine soft soil in its natural state;

[0043] The Mechanical parameters were obtained through triaxial consolidated undrained creep tests. , The results are obtained by integrating formulas (8) and (17) and combining them with the initial conditions.

[0044] Optionally, in step 1.4, the incremental equation for the disturbance state of marine soft soil is:

[0045]

[0046] In the formula, This is the strain tensor observed in practice; The strain tensor represents the strain of the relatively intact state; The strain tensor for fully adjusted state; This is the perturbation function.

[0047] Optionally, in step 2, the natural physical and mechanical parameters are the material constants and initial state parameters of the constitutive model in the relatively intact state and the fully adjusted state, respectively, and are used to calculate the mechanical response increment in the two states in parallel at each loading step.

[0048] Optionally, in step 3, the calculation variables include, but are not limited to, the stress, strain, energy dissipated per unit volume, and equivalent plastic shear strain of each stratum element.

[0049] Optionally, in step 4, the dual-threshold damage determination method includes the following steps:

[0050] Step 4.1: For each finite element element, extract the dissipated energy and equivalent plastic shear strain data per unit volume throughout the entire simulation process to form an "energy dissipation-plastic strain" data sequence.

[0051] Step 4.2: Under different working conditions, identify the inflection points of the data sequence curves and extract the inflection point data, including the critical dissipated energy value and the critical equivalent plastic shear strain value.

[0052] Step 4.3: Multiple inflection point data are aggregated as a sample set. The least squares method is used to construct the residual sum of squares objective function, and an optimization algorithm is used to solve for the optimal fitting parameters. Based on the power function relationship, the energy threshold expression for damage assessment is obtained.

[0053] ,

[0054] In the formula, The critical dissipation energy; This is the critical equivalent plastic shear strain; a ∗, b ∗, c * represents the optimal fitting parameters;

[0055] Step 4.4, for any computing unit, if its cumulative energy dissipation at the final simulation time is... D With equivalent plastic shear strain If the following conditions are met simultaneously, it is determined to be a potential damage element:

[0056] ,

[0057] In the formula, The minimum discriminant strain is set based on engineering experience.

[0058] Optionally, the objective function for the sum of squared residuals described in step 4.3 is expressed as follows: ,

[0059] The power function relationship is as follows: In the formula, a, b, and c are the fitting parameters to be determined.

[0060] The beneficial effects of this invention are as follows: First, this scheme abandons the traditional approach of treating the relatively intact state and the fully adjusted state separately, and innovatively constructs a unified constitutive model framework. By introducing a perturbation function D within the energy dissipation elastoplastic framework, the "relatively intact state (D=0)" and the "fully adjusted state (D=1)" are treated as two extreme special cases of the same model. This allows the model parameters (such as structural parameters, hardening amount, or yield surface shape parameters) to be interpolated and mapped with D between the two extremes under constraints, while maintaining the closure of the yield surface and positive energy definiteness. This achieves a dynamic and accurate characterization of the continuous structural degradation process of marine soft soil under external perturbation, fundamentally overcoming the shortcomings of traditional methods that cannot effectively reflect the coupled evolution relationship between soil mechanical parameters and structural state.

[0061] Furthermore, this scheme proposes a dual-criteria damage identification method based on "energy dissipation threshold" and "plastic strain threshold". This method integrates the degree of deformation and the energy dissipation mechanism, and can scientifically distinguish between the reversible and irreversible stages of deformation. It can accurately identify the key units and potential sliding surfaces in the soil that are damaged first, and realize the quantitative and refined positioning of engineering risk areas, overcoming the subjectivity and lag of relying on a single indicator or engineering experience.

[0062] In addition, this solution ultimately generates a damage distribution cloud map, which visually represents the complex structural degradation state of soil, providing clear risk classification and spatial distribution guidance for engineering design, construction control, and disaster early warning. Attached Figure Description

[0063] Figure 1 This is a flowchart of the method of the present invention;

[0064] Figure 2The diagram shows the numerical calculation model in this embodiment of the invention, where a is a structural schematic diagram and b is a numerical calculation model diagram.

[0065] Figure 3 The above are the stress-strain and equivalent plastic strain cloud diagrams of marine soft soil strata induced in this embodiment of the invention, where c is the displacement cloud diagram; d is the stress cloud diagram; e is a schematic diagram of the failure mode under a load of 200 kPa; f is a schematic diagram of the failure mode under a load of 300 kPa; and g is a schematic diagram of the failure mode under a load of 500 kPa. Detailed Implementation

[0066] To make the present invention clearer and more understandable, the present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the given embodiments are only one implementation method and do not represent all embodiments.

[0067] Combination Figure 1 This invention provides a method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state, comprising the following steps:

[0068] Step 1: Construct a constitutive model based on the concept of perturbation state. This constitutive model uses a perturbation function to characterize the continuous structural evolution of the soil from a relatively intact state to a fully adjusted state. The relatively intact state and the fully adjusted state are two extreme special cases of the constitutive model. In this embodiment, the relatively intact state is the initial relatively perfect state of the soil, i.e., the perturbation function D=0, and the fully adjusted state is the ultimate state reached by the soil after being subjected to force, i.e., the perturbation function D=1.

[0069] This step introduces a perturbation function D within the energy dissipation elastoplastic framework, treating the "relatively intact state (D=0)" and the "fully adjusted state (D=1)" as two extreme special cases of the same model. This allows model parameters (such as structural parameters, hardening amount, or yield surface shape parameters) to be interpolated and mapped between the two extremes with constraint as D is applied, while maintaining the closure of the yield surface and positive energy definiteness.

[0070] The calculation program for this step is written in Python, and its construction method includes the following steps:

[0071] Step 1.1: Obtain the incremental matrix equations of the constitutive model under the relatively intact state based on the Duncan-Chang model. The Duncan-Chang model is used for the relatively intact state of the constitutive model because it considers the nonlinear and elastoplastic behavior of the soil during loading and unloading, and can well simulate the rheological properties of soft soil. The stress-strain relationship calculation formula is as follows:

[0072]

[0073] In the formula, and These are the maximum and minimum principal stresses, respectively; For axial strain; K The parameters related to the initial elastic modulus were obtained by fitting experimental data. n The nonlinearity parameter of the material is obtained by fitting experimental data. The destructive stress ratio is usually determined experimentally and typically ranges from 0 to 1. The strain at which the material fails is determined through experimental data.

[0074] Differentiating formula (1) yields:

[0075]

[0076] Therefore, the expression for the axial strain increment of the Duncan-Chang model under relatively intact conditions can be obtained:

[0077]

[0078] Based on the Duncan-Chang model, the calculation of volumetric strain increments is directly related to the increments of axial and radial strains. Therefore, according to... ,in, For the body to adapt to strain, For axial strain, For radial strain, the expression for the volumetric strain increment relative to the intact state is:

[0079]

[0080] In the formula, The tangent modulus calculated in the Duncan-Chang model. The value is Poisson's ratio and needs to be determined experimentally. It should be noted that this formula assumes marine soft soil is isotropic; therefore, the radial strain increment is expressed as Poisson's ratio.

[0081] Based on the shear stress expression in the Duncan-Chang model:

[0082]

[0083] In the formula, Shear stress; For shear strain; G Let be the shear modulus, and its expression is: .

[0084] Therefore, the mathematical expression for the shear strain increment of the Duncan-Chang model in the relatively intact state is obtained as follows:

[0085]

[0086] in, The mathematical expression is:

[0087]

[0088] In the formula, Effective normal stress; The effective friction angle; For the parameters in the Duncan-Zhang model, representing the friction angle increment; For effective confining pressure, Atmospheric pressure (usually used as a reference pressure); This is a model parameter that affects the degree of stress dependence.

[0089] In summary, the incremental matrix equation of the constitutive model in the relatively complete state can be obtained as follows:

[0090]

[0091] In the formula, The strain represents the volumetric strain in a relatively intact state. Shear strain in a relatively intact state; Represented as 1 / K , K These are parameters related to the initial elastic modulus; Defined as zero or a partial derivative, it is used to reflect the dependence of volumetric strain on changes in deviatoric stress; The default value is 0, used to represent the dependence of shear strain on the change of mean effective stress. If weak coupling is declared, then use... Provide verifiable boundaries and dimensions; 1 / G ; For the effective average stress increment; This represents the shear stress increment.

[0092] Step 1.2: Obtain the incremental matrix equations of the constitutive model under the fully adjusted state based on the modified Cambridge model. The modified Cambridge model is mainly used for the behavior of soil in the plastic zone, describing the nonlinear relationship between stress and strain in soil, primarily considering the effects of strain hardening and strain softening. In this embodiment, the critical state theory is used to describe the mechanical behavior of this state, i.e., the modified Cambridge model is used to describe the remolded soil.

[0093] Since the fully adjusted state can be described by elastic, plastic, or elastoplastic models, the viscoplastic strain rate, according to the hyperstress rheological theory, is expressed as:

[0094]

[0095] In the formula, For viscoplastic strain rate tensor; is the viscoplastic proportionality coefficient, used to represent the magnitude of the viscoplastic strain rate tensor; For effective stress tensor; The direction used in plastic flow rules to determine the viscoplastic strain rate. F It is a viscoplastic function, i.e., a yield surface function.

[0096] Yield surface equation based on the modified Cambridge model:

[0097]

[0098] In the formula, The average effective stress; It is a deviatoric stress; Vertical stress in the initial stress field The effective value; M Let be the slope of the soil on the critical state line.

[0099] Therefore, the mathematical expression for the strain of the modified Cambridge model in its fully adjusted state can be obtained as follows:

[0100]

[0101] In the formula, For the body strain of the fully adjusted state; The initial volumetric strain; The compression factor is 1. The strain coefficient of the elastic body; This represents the current effective stress. Simplified to:

[0102]

[0103] Therefore, the expression for the strain increment of the modified Cambridge model in a fully tuned state can be obtained as follows:

[0104]

[0105] In the formula, This represents the initial void ratio.

[0106] Mathematical expression for shear strain based on the modified Cambridge model:

[0107]

[0108] In the formula, G is the shear modulus, which can be a constant or a variable dependent on the soil state (such as effective stress, void ratio). Furthermore, in the modified Cambridge model, the plastic potential function is often taken as a straight line parallel to the critical state line, and its equation is: .

[0109] Therefore, the expression for the incremental shear strain of the modified Cambridge model in the fully adjusted state is obtained as follows:

[0110]

[0111] Among them, parameters M It is calculated using the following formula:

[0112]

[0113] In the formula, The internal friction angle of marine soft soil.

[0114] For parameters and The result is obtained from the lateral constriction compression test using the following formula:

[0115] , ,

[0116] In the formula, , Reconstructing soil respectively e -lg p The compressibility index and springback index of a plane.

[0117] In summary, the incremental matrix equation of the constitutive model under the fully adjusted state is obtained:

[0118]

[0119] In the formula, For the body strain of the fully adjusted state; The shear strain is for a fully adjusted state; The compression factor is 1. is the strain coefficient of the elastic body.

[0120] Step 1.3: Based on the perturbation parameters obtained from the experiment, construct perturbation functions for volumetric strain and shear strain that describe the evolution of the material from a relatively intact state to a fully adjusted state.

[0121] Based on the general expression of the perturbation function:

[0122]

[0123] In the formula, , These are the perturbation functions for volumetric strain and shear strain, respectively. , , , These are the experimental parameters.

[0124] The perturbation functions of volumetric strain and shear strain evolving from a relatively intact state to a fully adjusted state are obtained, and their formulas are as follows:

[0125]

[0126] In the formula, The void ratio of marine soft soil in a relatively intact state; This represents the void ratio of marine soft soil under actual conditions. To fully adjust the void ratio of marine soft soil under the current condition; This represents the shear strain under actual conditions.

[0127] Among them, the Mechanical parameters were obtained through isotropic consolidation creep tests, among which...

[0128]

[0129] In the formula, The initial void ratio of marine soft soil in its natural state; The strain coefficient of the elastic body in a relatively intact state; The strain coefficient of the elastic body under fully adjusted conditions; The compression coefficient of marine soft soil in its natural state;

[0130] The Mechanical parameters were obtained through triaxial consolidated undrained creep tests. , By integrating formulas (8) and (17) and combining them with the initial conditions, we can obtain the following: The actual observed shear strains taken from the same path are directly calculated from the axial / radial strains measured by triaxial consolidated undrained creep.

[0131] Step 1.4: Based on the perturbation functions of the volumetric strain and shear strain, obtain the volumetric strain increment and shear strain increment matrices, and construct a constitutive model based on the concept of perturbation state, specifically as follows:

[0132] Based on the disturbance state theory, the incremental equation for the disturbance state concept of marine soft soil is:

[0133]

[0134] In the formula, This is the strain tensor observed in practice; The strain tensor represents the strain of the relatively intact state; The strain tensor for fully adjusted state; This is the perturbation function.

[0135] Therefore, the expressions for the bulk strain increment and deviatoric strain increment matrices can be obtained:

[0136]

[0137] In the formula, , .

[0138] Therefore, the obtained volumetric strain increment, shear strain increment, and unified algorithm tangent matrix can be directly used for numerical integration and global Newton iteration; when the perturbation function changes the "equivalent parameter / hardening variable", the above expression can automatically reflect the transition from the relatively intact state to the fully adjusted state through parameter updates.

[0139] Step 2: Obtain the natural physical and mechanical parameters of the marine soft soil based on indoor test data from marine soft soil samples. These natural physical and mechanical parameters are the material constants and initial state parameters of the constitutive model in both the relatively intact and fully adjusted states, used to calculate the mechanical response increments in parallel under each loading step. The material constants and initial state parameters include parameters related to the initial elastic modulus. K shear modulus G Or its flexibility, model structural parameters , wait.

[0140] Step 3: Input the natural physical and mechanical parameters into the constitutive model based on the concept of disturbance state constructed in Step 1, simulate the disturbance process of marine soft soil strata caused by engineering construction step by step, and extract the calculation variables of each stratum unit during the simulation process. The calculation variables include, but are not limited to, the stress, strain, energy dissipated per unit volume and equivalent plastic shear strain of each stratum unit.

[0141] Step 4: Based on the calculated variables, a dual-threshold damage determination method is used to identify potential damage units in each stratum, which specifically includes the following steps:

[0142] Step 4.1: For each finite element element, extract the dissipated energy and equivalent plastic shear strain data per unit volume throughout the entire simulation process to form an "energy dissipation-plastic strain" data sequence.

[0143] Step 4.2: Under different operating conditions, identify the inflection points of the data sequence curves and extract the inflection point data, including the critical dissipated energy value and the critical equivalent plastic shear strain value.

[0144] Step 4.3: Multiple inflection point data points are aggregated as a sample set. The least squares method is used to construct the residual sum of squares objective function, and the optimal fitting parameters are obtained using the `scipy.optimize.curve_fit` function in Python. Based on the power function relationship, the energy threshold expression for damage assessment is obtained.

[0145] ,

[0146] In the formula, The critical dissipation energy; This is the critical equivalent plastic shear strain; a ∗, b ∗, c * represents the optimal fitting parameters.

[0147] Furthermore, the objective function for the sum of squared residuals is expressed as:

[0148] ,

[0149] The power function relationship is as follows: ,

[0150] In the formula, a, b, and c are the fitting parameters to be determined.

[0151] Step 4.4, for any computing unit, if its cumulative energy dissipation at the final simulation time is... D With equivalent plastic shear strain If the following conditions are met simultaneously, it is determined to be a potential damage element:

[0152] ,

[0153] In the formula, The minimum discriminant strain is set based on engineering experience.

[0154] Step 5: Based on the spatial distribution of all potential damage units, mark all units that meet the dual criteria in Step 4.4 with color; at the same time, use the ABAQUS post-processing function to generate a formation damage distribution cloud map to realize the visual identification and zoning of engineering risk areas.

[0155] Therefore, by constructing the above steps, a coupled criterion between structural evolution, energy dissipation and plastic deformation was established, enabling quantitative identification and risk zoning of potential damage areas and key deformation zones in soft soil strata.

[0156] Simulation Example:

[0157] To verify the effectiveness and accuracy of the proposed evaluation method for deformation characteristics of marine soft soil based on the concept of disturbance state, this embodiment combines the actual working conditions of a temporary surcharged municipal building concrete structure in a marine soft soil area of ​​Shenzhen and conducts finite element numerical simulation analysis.

[0158] A simplified two-dimensional foundation settlement model was established based on the ABAQUS finite element program, such as... Figure 2As shown, the model measures 60m in length and 40m in height, and the entire stratum consists of marine soft soil. For comparative analysis, the constitutive relation is first adopted using the traditional Mohr-Coulomb model, with the following material parameters: internal friction angle 10°, cohesion 11kPa, elastic modulus 1.26MPa, and Poisson's ratio 0.3. The municipal building concrete structure is simplified as a rigid body, and uniformly distributed loads of 200kPa, 300kPa, and 500kPa are applied at its reference point (RP) to simulate the impact of temporary loading of the municipal building concrete structure on the settlement of the marine soft soil stratum.

[0159] like Figure 3 The paper presents contour maps of stress-strain and equivalent plastic strain induced in marine soft soil strata by temporary surcharge on municipal building concrete structures. Analysis shows that:

[0160] (1) The strain trends of marine soft soil strata are consistent under different load levels, with only the deformation values ​​differing, and the maximum settlement is located at the contact point between the structure and the soil. Specifically, the maximum settlement deformation value of marine soft soil strata under a load of 200 kPa is 1.27 cm, under a load of 300 kPa is 1.89 cm, and under a load of 500 kPa is 3.52 cm.

[0161] (2) The stress trends of marine soft soil strata under different loads are consistent, with only differences in stress values. The maximum stress value is also located at the contact point between the structure and the soil. The maximum stress values ​​are as follows: 109.37 kPa under 200 kPa load, 149.02 kPa under 300 kPa load, and 228.86 kPa under 500 kPa load.

[0162] (3) As the temporary surcharge load increases, the contact area between the marine soft soil and the concrete structure gradually undergoes shear deformation failure, eventually leading to through-through failure. To quantitatively verify the constitutive model based on the concept of disturbance state in this invention, the lower part of the contact position between the center point of the temporary surcharge municipal building concrete structure and the marine soft soil is 1.00m below the point of contact, and the calculated values ​​are compared and analyzed with those of the constitutive model proposed in this invention.

[0163] Table 1 shows a comparison between the ABAQUS numerical calculation results at this reference point and the calculation results of the constitutive model based on the concept of perturbation state proposed in this invention. The data shows that the maximum stress values ​​calculated by the constitutive model based on the concept of perturbation state are all smaller than those calculated by the ABAQUS numerical model, and the errors of both are kept within 3%, showing good agreement.

[0164] Table 1 Comparison of maximum stress values ​​calculated using ABAQUS numerical calculations and constitutive models under perturbed conditions.

[0165]

[0166] Therefore, in summary, this embodiment, by comparing the calculation results of traditional finite element analysis with those of the model proposed in this invention, confirms that the constitutive model based on the concept of perturbation state has high calculation accuracy and reliability, and can be effectively applied to the evaluation of the foundation bearing capacity performance of marine soft soil strata.

Claims

1. A method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state, characterized in that, Includes the following steps: Step 1: Construct a constitutive model based on the concept of perturbation state. The constitutive model characterizes the structural continuous evolution process of soil from a relatively intact state to a fully adjusted state through a perturbation function. The relatively intact state and the fully adjusted state are two extreme special cases of the constitutive model. Its computational program is written in Python, and the method for constructing a constitutive model based on the concept of perturbation states specifically includes: Step 1.1: Obtain the incremental matrix equation of the constitutive model in the relatively complete state based on the Duncan-Zhang model. The formula is as follows: In the formula, The strain represents the volumetric strain in a relatively intact state. Shear strain in a relatively intact state; Represented as 1 / K , K These are parameters related to the initial elastic modulus; Defined as zero or a partial derivative, it is used to reflect the dependence of volumetric strain on changes in deviatoric stress; The default value is 0, which is used to represent the dependence of shear strain on the change of average effective stress; 1 / G , G Shear modulus; For the effective average stress increment; This represents the increment of shear stress. Step 1.2: Obtain the incremental matrix equation of the constitutive model under the fully adjusted state based on the modified Cambridge model. Its formula is as follows: In the formula, For the body strain of the fully adjusted state; The shear strain is for a fully adjusted state; The compression factor is 1. The strain coefficient of the elastic body; Step 1.3: Based on the perturbation parameters obtained from experiments, construct perturbation functions for volumetric strain and shear strain to describe the evolution of the material from a relatively intact state to a fully adjusted state. The formula is as follows: In the formula, The void ratio of marine soft soil in a relatively intact state; This represents the void ratio of marine soft soil under actual conditions. To fully adjust the void ratio of marine soft soil under the current condition; The perturbation function for volumetric strain; Let be the perturbation function for shear strain; This represents the shear strain under actual conditions. Step 1.4: Based on the perturbation functions of the volumetric strain and shear strain, obtain the expressions for the volumetric strain increment and shear strain increment matrices, and construct a constitutive model based on the concept of perturbation state. The mathematical expressions for the volumetric strain increment and shear strain increment matrices are as follows: In the formula, , ; Step 2: Obtain the natural physical and mechanical parameters of marine soft soil based on indoor test data of marine soft soil samples; Step 3: Input the natural physical and mechanical parameters into the constitutive model based on the concept of disturbance state constructed in Step 1, simulate the disturbance process of marine soft soil strata caused by engineering construction step by step, and extract the calculation variables of each stratum unit in the simulation process; Step 4: Based on the calculated variables, identify potential damage units in each stratum using a dual-threshold damage determination method; Step 5: Based on the spatial distribution of all potential damage units, generate a formation damage distribution cloud map to achieve visual identification and zoning of engineering risk areas.

2. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 1, characterized in that: In step 1.1, The expression for the volumetric strain increment of the constitutive model in a relatively intact state is as follows: In the formula, This is the tangent modulus calculated in the Duncan-Zhang model. Poisson's ratio, This is the maximum principal stress; The expression for the shear strain increment of the constitutive model in the relatively intact state is as follows: In the formula, This represents the shear stress increment.

3. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 1, characterized in that: In step 1.2, the expression for the volumetric strain increment of the constitutive model in the fully adjusted state is: In the formula, This represents the elastic volumetric strain increment; This represents the plastic volumetric strain increment; The average effective stress; The initial void ratio; The expression for the shear strain increment of the constitutive model under the fully adjusted state is as follows: In the formula, The shear strain is for a fully adjusted state; This represents the current effective stress. Equivalent Young's modulus; This represents the critical stress ratio.

4. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 1, characterized in that: In step 1.3, the Mechanical parameters were obtained through isotropic consolidation creep tests, among which... In the formula, The initial void ratio of marine soft soil in its natural state; The strain coefficient of the elastic body in a relatively intact state; The strain coefficient of the elastic body under fully adjusted conditions; The compression coefficient of marine soft soil in its natural state; The Mechanical parameters were obtained through triaxial consolidated undrained creep tests. , The results are obtained by integrating formulas (8) and (17) and combining them with the initial conditions.

5. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 1, characterized in that: In step 1.4, the incremental equation for the disturbance state of marine soft soil is: In the formula, This is the strain tensor observed in practice; The strain tensor represents the strain of the relatively intact state; The strain tensor for fully adjusted state; This is the perturbation function.

6. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 1, characterized in that, In step 2, the natural physical and mechanical parameters are the material constants and initial state parameters of the constitutive model in the relatively intact state and the fully adjusted state, respectively, and are used to calculate the mechanical response increment in the relatively intact state and the fully adjusted state in parallel at each loading step.

7. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 1, characterized in that, In step 3, the calculation variables include, but are not limited to, the stress, strain, energy dissipated per unit volume, and equivalent plastic shear strain of each stratum element.

8. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 1, characterized in that, Step 4, the dual-threshold damage determination method includes the following steps: Step 4.1: For each finite element, extract the dissipated energy and equivalent plastic shear strain data per unit volume throughout the entire simulation process to form an "energy dissipation-plastic strain" data sequence. Step 4.2: Under different working conditions, identify the inflection points of the data sequence curves and extract the inflection point data, including the critical dissipated energy value and the critical equivalent plastic shear strain value. Step 4.3: Multiple inflection point data are aggregated as a sample set. The least squares method is used to construct the residual sum of squares objective function, and an optimization algorithm is used to solve for the optimal fitting parameters. Based on the power function relationship, the energy threshold expression for damage assessment is obtained. ， In the formula, The critical dissipation energy; This is the critical equivalent plastic shear strain; a , b , c These are the optimal fitting parameters; Step 4.4, for any computing unit, if its cumulative energy dissipation at the final simulation time is... D With equivalent plastic shear strain If the following conditions are met simultaneously, it is determined to be a potential damage element: ， In the formula, The minimum discriminant strain is set based on engineering experience.

9. The method for evaluating the deformation characteristics of marine soft soil based on the concept of disturbance state according to claim 8, characterized in that, The objective function for the sum of squared residuals described in step 4.3 is expressed as follows: , The power function relationship is as follows: In the formula, a, b, and c are the fitting parameters to be determined.

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