Marine facies soft soil deformation characteristic evaluation method based on disturbance state concept

Abstract

The invention relates to the technical field of geotechnical engineering, and provides a marine facies soft soil deformation characteristic evaluation method based on a disturbance state concept, comprising the following steps: step 1, constructing a constitutive model based on the disturbance state concept; 2, acquiring natural physical and mechanical parameters of the marine soft soil based on indoor test data; 3, based on the natural physical and mechanical parameters, the disturbance process of engineering construction on the marine facies soft soil stratum is simulated step by step, and calculation variables of all stratum units in the simulation process are extracted; 4, identifying potential damage units in each stratum by adopting a dual-threshold damage judgment method; and step 5, based on the spatial distribution of all potential damage units, generating a stratum damage distribution cloud picture, and realizing visual identification and partition grading of the engineering risk area. According to the scheme, a coupling criterion among structural evolution, energy dissipation and plastic deformation is constructed, and meanwhile quantitative recognition and risk zoning of potential damage areas and key deformation areas in the soft soil stratum are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering, and particularly relates to a marine soft soil deformation characteristic evaluation method based on a disturbance state concept. BACKGROUND

[0002] Marine soft soil is widely distributed in coastal areas of China, and has engineering properties such as high natural void ratio, high water content, low shear strength, high compressibility, and significant structure. In major engineering construction such as urban rail transit, cross-sea channel, deep foundation pit, and underground space development, marine soft soil as an important engineering medium, its mechanical behavior and stability are directly related to the safety and sustainability of the project. However, when subjected to external disturbance (such as tunneling, foundation pit excavation, load application, etc.), the structural property of marine soft soil is easily damaged, leading to complex responses such as strength attenuation, enhanced shear dilation behavior, pore pressure accumulation, and deformation mutation, which can easily cause ground deformation instability, surrounding rock damage, and supporting structure damage.

[0003] Existing marine soft soil deformation evaluation methods are mostly based on traditional elastic-plastic theory or empirical criteria, and usually use stress-strain curves, cumulative plastic strain, and shear modulus degradation as indicators to analyze deformation characteristics. However, these methods often have the following shortcomings: (1) lack of systematic characterization of the structural degradation process caused by disturbance, unable to accurately reflect the coupling relationship between soil mechanical parameters and structural evolution; (2) difficult to distinguish between reversible and irreversible stages of deformation, unable to identify key damage units or potential risk areas; (3) most methods rely on engineering experience or a single physical quantity, with strong subjectivity and poor timeliness of evaluation results, making it difficult to meet the needs of fine deformation prediction and control under complex geological conditions and construction disturbance.

[0004] The Disturbance State Concept (DSC) was first proposed by Desai, which describes the continuous damage process of material internal structure by introducing a disturbance factor. This theory has clear physical meaning and is easy to implement numerically. It combines the structural changes of materials with stress-strain response and energy dissipation mechanism, and can effectively simulate the strain softening, strength loss, and deformation development of marine soft soil under disturbance. However, there is still no systematic method for identifying the response of marine soft soil to engineering disturbance and distinguishing deformation areas based on DSC, and its application in numerical simulation and engineering risk control is still in its early stages.

[0005] Therefore, it is urgent to propose a marine soft soil deformation characteristic evaluation method based on the disturbance state concept, which combines energy dissipation analysis and plastic strain criteria to establish a scientific deformation identification mechanism and evaluation process, and to realize dynamic tracking of marine soft soil disturbance response, key unit identification, and risk level classification, providing new theoretical and technical support for engineering design, construction control, and disaster warning. SUMMARY

[0006] To solve the problems in the background art, the application provides a marine soft soil deformation feature evaluation method based on a disturbance state concept, a coupling criterion between structural evolution, energy dissipation and plastic deformation is constructed, and quantitative identification and risk zoning of potential damage areas and key deformation areas in the soft soil layer are realized.

[0007] To achieve the above-mentioned purpose, the application adopts the following scheme: A marine soft soil deformation feature evaluation method based on a disturbance state concept, comprising the following steps: Step 1, a constitutive model based on the disturbance state concept is constructed, the constitutive model represents the structural continuous evolution process of the soil from the relative complete state to the completely adjusted state through the disturbance function; the relative complete state and the completely adjusted state are two extreme examples of the constitutive model; Step 2, the natural physical and mechanical parameters of the marine soft soil are obtained based on the indoor test data of the marine soft soil sample; Step 3, the natural physical and mechanical parameters are input into the constitutive model based on the disturbance state concept constructed in step 1, the disturbance process of the marine soft soil layer caused by the engineering construction is simulated step by step, and the calculation variables of each stratum unit in the simulation process are extracted; Step 4, based on the calculation variables, a double-threshold damage judgment method is used to identify the potential damage units in each stratum; Step 5, based on the spatial distribution of all potential damage units, a stratum damage distribution cloud chart is generated, and the visual identification and zoning of the engineering risk area are realized.

[0008] Optionally, the calculation program in step 1 is written in Python language, and the method for constructing the constitutive model based on the disturbance state concept comprises the following steps: Step 1.1, the incremental matrix equation of the constitutive model under the relative complete state is obtained based on the Duncan-Zhang model, and the formula is represented as:

[0009] In the formula, is the volumetric strain under the relative complete state; is the shear strain under the relative complete state; is represented as 1 / K , K is the initial elastic modulus related parameter; is zero or a partial derivative definition, which is used to reflect the dependence of the volumetric strain on the change of the deviatoric stress; 0 is taken by default, which is used to represent the dependence of the shear strain on the change of the average effective stress; is 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:

[0010] 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:

[0011] 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:

[0012] In the formula, , .

[0013] Optionally, in step 1.1, The expression for the volumetric strain increment of the constitutive model in a relatively intact state is as follows:

[0014] In the formula, The tangent modulus calculated in the Duncan-Chang 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:

[0015] wherein, is the increment of shear stress.

[0016] Optionally, in step 1.2, the constitutive model in the fully adjusted state is expressed as:

[0017] wherein, is the increment of elastic volumetric strain; is the increment of plastic volumetric strain; is the average effective stress; is the initial void ratio; the increment of shear strain of the constitutive model in the fully adjusted state is expressed as:

[0018] wherein, is the increment of shear strain in the fully adjusted state; is the current effective stress; is the equivalent Young's modulus; is the critical state stress ratio.

[0019] Optionally, in step 1.3, the the mechanical parameters are obtained by isotropic consolidation creep test, wherein,

[0020] wherein, is the initial void ratio of the marine soft soil in the natural state; is the elastic volumetric strain coefficient in the relatively complete state; is the elastic volumetric strain coefficient in the fully adjusted state; is the compression coefficient of the marine soft soil in the natural state; the the mechanical parameters are obtained by triaxial consolidation undrained creep test, wherein, , is obtained by integrating formula (8) and formula (17) and combining the initial condition.

[0021] Optionally, in step 1.4, the conceptual incremental equation of the marine soft soil in the disturbed state is:

[0022] wherein, is the actual observed strain tensor; is the strain tensor in the relatively complete state; is the strain tensor in the fully adjusted state; is the disturbance function.

[0023] Optionally, in step 2, the natural physical mechanics parameters are the material constants and initial state parameters of the constitutive model in the respective relative intact state and fully adjusted state, used for parallel calculation of the mechanical response increments in the two states at each loading step.

[0024] Optionally, in step 3, the calculation variables include, but are not limited to, the stress, strain, unit volume dissipated energy and equivalent plastic shear strain of each stratum unit.

[0025] Optionally, in step 4, the double-threshold damage judgment method includes the following steps: Step 4.1, for each finite element unit, extract the unit volume dissipated energy and equivalent plastic shear strain data throughout the entire simulation process to form an "energy dissipation-plastic strain" data sequence; Step 4.2, under different working conditions, identify the curve inflection point of the data sequence, and extract the inflection point data including the critical dissipated energy value and the critical equivalent plastic shear strain value; Step 4.3, aggregate multiple inflection point data as a sample set, construct a residual sum of squares objective function using the least squares method principle, and solve the optimal fitting parameters using an optimization algorithm to obtain the energy threshold expression in the damage judgment based on a power function relationship: , In the formula, is the critical dissipated energy; is the critical equivalent plastic shear strain; a , b , c is the optimal fitting parameter; Step 4.4, for any calculation unit, if its cumulative dissipated energy at the final simulation time D and the equivalent plastic shear strain simultaneously satisfy the following conditions, it is determined to be a potential damage unit: , In the formula, is the minimum discriminant strain set by engineering experience.

[0026] Optionally, in step 4.3, the residual sum of squares objective function is represented as , The power function relationship is: In the formula, a, b, c are undetermined fitting parameters.

[0027] The present application has the beneficial effects that: first, the present application discards the traditional mode of splitting the relative complete state and the completely adjusted state, and innovatively constructs a unified constitutive model framework. By introducing a disturbance function D in the energy dissipation elastoplastic framework, the "relative complete state (D=0)" and "completely adjusted state (D=1)" are taken as two limit examples of the same model, the model parameters (such as structural parameters, hardening amount or yield surface shape parameters) are interpolated and mapped between the two limits with the constraint of D, the yield surface closure and energy positivity are maintained, and the dynamic and accurate description of the continuous degradation process of the marine soft soil under external disturbance is realized, which fundamentally overcomes the defects that the traditional method cannot effectively reflect the coupling evolution relationship between the soil mechanical parameters and the structural state.

[0028] Moreover, the present application proposes a double-criterion damage identification method based on "energy dissipation threshold" and "plastic strain threshold". The method combines the deformation degree and the energy dissipation mechanism, can scientifically distinguish the reversible and irreversible stages of deformation, accurately identify the key elements and potential sliding surfaces in the soil where damage occurs first, realizes the quantitative and fine positioning of the engineering risk area, and overcomes the subjectivity and hysteresis of relying on single index or engineering experience.

[0029] In addition, the present application finally visualizes the complex soil structural degradation state through generating a damage distribution cloud map, which can directly provide clear risk classification and spatial distribution guidance for engineering design, construction control and disaster warning. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The flowchart of the method of the present application; Figure 2 The numerical calculation model diagram in the embodiment of the present application, wherein a is a structural schematic diagram; and b is a numerical calculation model diagram; Figure 3 The stress-strain and equivalent plastic strain cloud maps of the marine soft soil layer induced in the embodiment of the present application, wherein c is a displacement cloud map; d is a stress cloud map; e is a schematic diagram of a failure mode under a load of 200kPa; f is a schematic diagram of a failure mode under a load of 300kPa; and g is a schematic diagram of a failure mode under a load of 500kPa. DETAILED DESCRIPTION

[0031] In order to make the present application clearer and more understandable, the following describes the present application in detail with reference to the accompanying drawings, embodiments and examples. It should be understood that the embodiments given are only one of the implementation manners, and do not represent all the embodiments.

[0032] In combination Figure 1 The embodiment of the present application provides a marine soft soil deformation characteristic evaluation method based on the disturbance state concept, which comprises the following steps: Step 1, a constitutive model based on the concept of disturbed state is constructed, which represents the continuous evolution process of the structure of the soil from the relative intact state to the fully adjusted state through the disturbance function; the relative intact state and the fully adjusted state are two extreme cases of the constitutive model. In this embodiment, the relative intact state is the initial relatively perfect state of the soil, i.e., the disturbance function D = 0, and the fully adjusted state is the limit state reached by the soil after being stressed, i.e., the disturbance function D = 1.

[0033] This step introduces the disturbance function D into the energy dissipation elastoplasticity framework, takes the “relative intact state (D = 0)” and the “fully adjusted state (D = 1)” as two extreme cases of the same model, makes the model parameters (such as the structural parameters, the hardening amount or the yield surface shape parameters) interpolate and map between the two extremes with constraints, and keeps the yield surface closed and the energy positive definite.

[0034] The calculation program of this step is written in Python language, and the construction method specifically includes the following steps: Step 1.1, based on the Duncan-Chang model, the incremental matrix equation of the constitutive model in the relative intact state is obtained. The relative intact state of the constitutive model adopts the Duncan-Chang model, because the model considers the nonlinear and elastoplastic behavior of the soil in the loading and unloading process, and can well simulate the rheological properties of soft soil, and the stress-strain relationship calculation formula is:

[0035] In the formula, σ x and σ 3 are the maximum and minimum principal stresses respectively; and are the maximum and minimum principal stresses respectively; is the axial strain; K is the initial elastic modulus related parameter, which is obtained by fitting experimental data; n is the material nonlinear degree parameter, which is obtained by fitting experimental data; is the failure stress ratio, which is usually determined by experiment, and generally takes a value between 0 and 1; is the strain at material failure, which is determined by experimental data.

[0036] The formula (1) is differentiated to obtain:

[0037] The axial strain increment expression of the Duncan-Chang model in the relative intact state is obtained as follows:

[0038] Based on the Duncan-Chang model, the calculation of the volumetric strain increment is directly related to the increments of the axial strain and the radial strain, therefore, according to wherein, is the volumetric strain, is the axial strain, is the radial strain, whose increment expression in the relative intact state is:

[0039] where, is the tangent modulus calculated in the Duncan-Chang model, is the Poisson's ratio, which needs to be determined by experiment. It needs to be explained that the formula assumes that the marine soft soil is isotropic, so its radial strain increment is expressed by the Poisson's ratio.

[0040] Based on the shear stress expression in the Duncan-Chang model:

[0041] where, is the shear stress; is the shear strain; G is the shear modulus, whose expression is .

[0042] Thus, the mathematical expression of the shear strain increment of the Duncan-Chang model in the relative intact state is obtained as:

[0043] where, The mathematical expression is:

[0044] where, is the effective normal stress; is the effective friction angle; is the parameter in the Duncan-Chang model, representing the increment of the friction angle; is the effective confining pressure, is the atmospheric pressure (usually as the reference pressure); is a model parameter, affecting the degree of pressure dependence.

[0045] The incremental matrix equation of the constitutive model in the relative intact state can be obtained as follows:

[0046] where, is the bulk strain in the relative intact state; is the shear strain in the relative intact state; represents 1 / K , K is the initial elastic modulus related parameter; is zero or partial derivative definition, used to reflect the dependence of the volume strain on the change of the deviatoric stress; Default value is 0, which is used to represent the dependence of shear strain on the change of average effective stress. If the weak coupling is declared, the value is used The checkable bounds and dimensions are given. The value is 1 / G . The value is the increment of effective average stress. The value is the increment of shear stress.

[0047] Step 1.2, the increment matrix equation of the constitutive model in the fully adjusted state is obtained based on the modified Cambridge model. The modified Cambridge model is mainly used for the behavior of soil in the plastic zone, which is used to describe the nonlinear relationship between stress and strain of soil, mainly considering the effects of strain hardening and strain softening. In this embodiment, the critical state theory is used to describe the mechanical behavior of the state, that is, the modified Cambridge model is used to describe the remolded soil.

[0048] Based on the fully adjusted state, the elastic, plastic or elastoplastic model can be used to describe, therefore, according to the super stress rheological theory, the viscous plastic strain rate is represented as:

[0049] In the formula, The value is the viscous plastic strain rate tensor; The value is the viscous plastic proportionality coefficient, which is used to represent the size of the viscous plastic strain rate tensor; The value is the effective stress tensor; The value is the direction used to determine the viscous plastic strain rate in the plastic flow rule, F The value is the viscous plastic function, that is, the yield surface function.

[0050] The yield surface equation of the modified Cambridge model based on the modified Cambridge model is:

[0051] In the formula, The value is the average effective stress; The value is the deviatoric stress; The value is the effective value of the vertical stress in the initial stress field; M The value is the slope of the soil on the critical state line.

[0052] Thus, the mathematical expression of the modified Cambridge model of the bulk strain in the fully adjusted state is obtained as:

[0053] In the formula, The value is the bulk strain in the fully adjusted state; The value is the initial bulk strain; The value is the compression coefficient; The value is the elastic bulk strain coefficient; The value is the current effective stress. Simplified as:

[0054] Thus, the expression of the increment of the volumetric strain of the modified Cam-Clay model in the fully adjusted state is:

[0055] where, is the initial void ratio.

[0056] Based on the mathematical expression of the shear strain of the modified Cam-Clay model:

[0057] where, G is the shear modulus, which can be a constant or a variable depending on the state of the soil (such as effective stress, void ratio), In addition, in the modified Cam-Clay model, the plastic potential function is often taken as a straight line parallel to the critical state line, and its equation is .

[0058] Thus, the expression of the increment of the shear strain of the modified Cam-Clay model in the fully adjusted state is:

[0059] where, the parameter M is calculated by the following formula:

[0060] where, is the internal friction angle of marine soft soil.

[0061] For the parameters and are obtained by the following formula from the confined compression test: , , where, , are the compression index and the rebound index of the remolded soil in the e -lg p plane, respectively.

[0062] In summary, the increment matrix equation of the constitutive model in the fully adjusted state is obtained:

[0063] where, is the volumetric strain in the fully adjusted state; is the shear strain in the fully adjusted state; is the compression coefficient; is the elastic volumetric strain coefficient.

[0064] Step 1.3, based on the test, the disturbance degree parameter is obtained, and the disturbance function of the bulk strain and shear strain describing the evolution of the material from the relatively complete state to the fully adjusted state is constructed.

[0065] Based on the general expression of the disturbance function:

[0066] In the formula, , are the disturbance functions of the bulk strain and shear strain, respectively, , , , are test parameters.

[0067] Obtained, the disturbance function of the bulk strain and shear strain evolving from the relatively complete state to the fully adjusted state is:

[0068] In the formula, is the void ratio of the marine soft soil in the relatively complete state; is the void ratio of the marine soft soil in the actual state; is the void ratio of the marine soft soil in the fully adjusted state; is the shear strain in the actual state.

[0069] Wherein, the The mechanical parameters are obtained by isotropic consolidation creep test, wherein,

[0070] In the formula, is the initial void ratio of the marine soft soil in the natural state; is the elastic bulk strain coefficient in the relatively complete state; is the elastic bulk strain coefficient in the fully adjusted state; is the compression coefficient of the marine soft soil in the natural state; The The mechanical parameters are obtained by triaxial consolidation undrained creep test, wherein, , By integrating formula (8), formula (17) and combining the initial conditions, we get The actual observed shear strain taken from the same path is directly calculated from the axial / radial strain obtained by triaxial consolidation undrained creep test.

[0071] Step 1.4, based on the disturbance function of the bulk strain and shear strain, the bulk strain increment and shear strain increment matrix are obtained, and the constitutive model based on the disturbance state concept is constructed, specifically: Based on the disturbed state theory, the increment equation of the disturbed state concept of marine soft soil is:

[0072] wherein, is the actual observed strain tensor; is the strain tensor of the relative intact state; is the strain tensor of the fully adjusted state; is the disturbed function.

[0073] Thus, the matrix expressions of the volumetric strain increment and the shear strain increment can be obtained:

[0074] wherein, , .

[0075] Therefore, by obtaining the volumetric strain increment, the shear strain increment and the unified algorithm tangent matrix, they can be directly used for numerical integration and global Newton iteration; when the disturbed function changes the “equivalent parameter / hardening variable”, the above expressions can automatically reflect the transition from the relative intact state to the fully adjusted state through parameter updating.

[0076] Step 2, based on the indoor test data of the marine soft soil sample, the natural physical and mechanical parameters of the marine soft soil are obtained. The natural physical and mechanical parameters are the material constants and initial state parameters of the constitutive model in the respective states of the relative intact state and the fully adjusted state, which are used to calculate the mechanical response increment in the two states in parallel at each loading step. The material constants and initial state parameters include the initial elastic modulus related parameters K , the shear modulus G or its compliance, the model structural parameters , and the like.

[0077] Step 3, the natural physical and mechanical parameters are input into the constitutive model based on the disturbed state concept constructed in step 1, the disturbance process of the marine soft soil layer caused by the engineering construction is simulated step by step, and the calculation variables of each stratum unit in the simulation process are extracted, which include but are not limited to the stress, strain, unit volume dissipation energy and equivalent plastic shear strain of each stratum unit.

[0078] Step 4, based on the calculation variables, a double-threshold damage judgment method is used to identify the potential damage units in each stratum, which specifically includes the following steps: Step 4.1, for each finite element unit, the unit volume dissipation energy and equivalent plastic shear strain data in the entire simulation process are extracted to form an “energy dissipation-plastic strain” data sequence.

[0079] Step 4.2, under different working conditions, identify the curve inflection point of the data sequence, and extract the inflection point data including the critical dissipated energy value and the critical equivalent plastic shear strain value.

[0080] Step 4.3, aggregate multiple inflection point data as a sample set, construct a residual sum of squares objective function using the least squares method, and obtain optimal fitting parameters by using the scipy.optimize.curve_fit function in Python to obtain the energy threshold expression in damage judgment based on the power function relationship: , In the formula, is the critical dissipated energy; is the critical equivalent plastic shear strain; a *, b *, c * is the optimal fitting parameter.

[0081] Further, the residual sum of squares objective function is expressed as: , The power function relationship is: , In the formula, a, b, c are undetermined fitting parameters.

[0082] Step 4.4, for any calculation unit, if its cumulative dissipated energy at the simulation final time D and the equivalent plastic shear strain satisfy the following conditions at the same time, it is determined to be a potential damage unit: , In the formula, is the minimum discriminant strain set by engineering experience.

[0083] Step 5, based on the spatial distribution of all potential damage units, all units that satisfy the double criteria in step 4.4 are identified by color; at the same time, the stratum damage distribution cloud chart is generated by using the post-processing function of ABAQUS, realizing the visualization identification and zoning of engineering risk area.

[0084] Therefore, by the above steps, a coupling criterion between structural evolution, energy dissipation and plastic deformation is constructed, realizing the quantitative identification and risk zoning of potential damage area and key deformation area in soft soil stratum.

[0085] Simulation example: In order to verify the effectiveness and accuracy of the marine soft soil deformation characteristic evaluation method based on the disturbance state concept proposed in the present application, this embodiment combines the actual working conditions of a marine soft soil area in Shenzhen City, and carries out finite element numerical simulation analysis.

[0086] Based on the ABAQUS finite element program, a two-dimensional foundation settlement simplified model is established, as shown in the drawings. Figure 2 The model size is 60m long and 40m high, and the overall stratum is marine soft soil. In order to compare and analyze, the constitutive relation first adopts the traditional Mohr-Coulomb model, and the material parameters are set as follows: 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 a uniform load of 200kPa, 300kPa and 500kPa is respectively applied on the reference point (RP) of the rigid body, so as to simulate the influence of temporary pile-up municipal building concrete structure on the settlement of marine soft soil.

[0087] As shown in the drawings, Figure 3 the stress-strain and equivalent plastic strain contours of the marine soft soil induced by the temporary pile-up municipal building concrete structure are given. The analysis shows that: (1) Under different load levels, the strain trend of the marine soft soil is consistent, only the deformation value is different, and the maximum settlement is located at the contact between the structure and the soil. The specific settlement values are: the maximum settlement deformation value of the marine soft soil under the action of 200kPa load is 1.27cm, the maximum settlement deformation value of the marine soft soil under the action of 300kPa load is 1.89cm, and the maximum settlement deformation value of the marine soft soil under the action of 500kPa load is 3.52cm.

[0088] (2) Under the action of different loads, the stress trend of the marine soft soil is also consistent, only the stress value is different, and the maximum stress value is also located at the contact between the structure and the soil, which are: the maximum stress value of the marine soft soil under the action of 200kPa load is 109.37kPa, the maximum stress value of the marine soft soil under the action of 300kPa load is 149.02kPa, and the maximum stress value of the marine soft soil under the action of 500kPa load is 228.86kPa.

[0089] (3) With the increase of the temporary pile-up load value, the contact area between the marine soft soil and the concrete structure gradually occurs shear deformation failure, and is finally penetrated and destroyed. In order to quantitatively verify the constitutive model based on the disturbance state concept in the present application, the lower 1.00m of the contact position between the center point of the temporary pile-up municipal building concrete structure and the marine soft soil is taken as the reference point, and the calculated value of the constitutive model proposed in the present application is compared and analyzed.

[0090] As shown in Table 1, the ABAQUS numerical calculation results at the reference point are compared with the calculation results of the constitutive model based on the disturbance state concept proposed in the present application. The data show that the maximum stress values calculated by the constitutive model based on the disturbance state concept are all smaller than the ABAQUS numerical calculation values, and the errors of both are kept within 3%, which are in good agreement.

[0091] Table 1 Comparison of maximum stress values between ABAQUS numerical calculation and disturbance state constitutive model calculation

[0092] Therefore, in summary, by comparing the calculation results of the traditional finite element analysis and the model of the present application, it is proved that the constitutive model based on the disturbance state concept has high calculation accuracy and reliability, and can be effectively applied to the evaluation of the bearing capacity performance of the marine soft soil foundation.

Claims

1. A method for evaluating deformation characteristics of marine soft soil based on a concept of a disturbance state, characterized by, Comprising the following steps: Step 1, constructing a constitutive model based on the concept of disturbed state, which represents the continuous evolution process of soil structure from the relative intact state to the fully adjusted state through the disturbance function; the relative intact state and the fully adjusted state are two extreme cases of the constitutive model; Step 2, obtaining the natural physical and mechanical parameters of marine soft soil based on the indoor test data of marine soft soil samples; Step 3, inputting the natural physical and mechanical parameters into the constitutive model based on the concept of disturbed state constructed in step 1, simulating the disturbance process of marine soft soil layer by engineering construction step by step, and extracting the calculation variables of each stratum unit in the simulation process; Step 4, based on the calculation variables, using a double-threshold damage judgment method to identify the potential damage units in each stratum; Step 5, based on the spatial distribution of all potential damage units, generating a stratum damage distribution cloud map to realize the 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: The calculation program in step 1 is written in Python language, and the method of constructing the constitutive model based on the concept of disturbed state includes the following steps: Step 1.1, obtaining the incremental matrix equation of the constitutive model in the relative intact state based on the Duncan-Zhang model, which is expressed as: wherein is the bulk strain in the relative intact state; is the shear strain in the relative intact state; is the initial elastic modulus related parameter; K , K is the initial elastic modulus related parameter; is zero or a partial derivative, used to reflect the dependence of the bulk strain on the change of the deviatoric stress; is zero by default, used to reflect the dependence of the shear strain on the change of the average effective stress; is 1 / G , G is the shear modulus; is the effective average stress increment; is the shear stress increment; Step 1.2, obtaining the incremental matrix equation of the constitutive model in the fully adjusted state based on the modified Cambridge model, which is expressed as: wherein is the bulk strain in the fully relaxed state; is the shear strain in the fully relaxed state; is the compressibility; is the elastic bulk strain coefficient; Step 1.3, constructing a disturbance function based on the test to describe the evolution of the material from the relative intact state to the fully adjusted state, which is expressed as: wherein is the void ratio of the marine soft soil in the relative intact state; is the void ratio of the marine soft soil in the actual state; is the void ratio of the marine soft soil in the fully consolidated state; is the disturbance function of the bulk strain; is the disturbance function of the shear strain; is the shear strain in the actual state; Step 1.4, based on the disturbance function of the volumetric strain and shear strain, obtaining the volumetric strain increment and shear strain increment matrix expression, and constructing the constitutive model based on the concept of disturbed state, which is expressed as: In the formulae, , .

3. The method according to claim 2, characterized in that: In step 1.1, The expression of the volumetric strain increment of the constitutive model in the relative intact state is: wherein G is the shear modulus, ν is the Poisson's ratio, σ1is the maximum principal stress; The expression of the shear strain increment of the constitutive model in the relative intact state is: In the formula, is the increment of shear stress.

4. The marine soft soil deformation characteristic evaluation method based on the disturbance state concept according to claim 2, characterized in that: In step 1.2, the expression of the volumetric strain increment of the constitutive model in the fully adjusted state is: wherein is the increment of elastic volumetric strain; is the increment of plastic volumetric strain; is the average effective stress; is the initial void ratio; The expression of the shear strain increment of the constitutive model in the fully adjusted state is: wherein is the shear strain for fully adjusted state; is the current effective stress; is the equivalent Young's modulus; is the critical state stress ratio.

5. The marine soft soil deformation characteristic evaluation method based on the disturbance state concept according to claim 2, characterized in that: In step 1.3, the The mechanical parameters are obtained by isotropic consolidation creep test, wherein, wherein is the initial void ratio of the marine soft soil in the natural state; is the coefficient of elastic strain of the relative intact state; is the coefficient of elastic strain of the fully adjusted state; is the compression coefficient of the marine soft soil in the natural state; The The mechanical parameters are obtained by triaxial consolidation undrained creep test, wherein, , The is obtained by integrating equation (8), equation (17) and combining initial conditions.

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 1.4, the incremental equation of the disturbed state concept of marine soft soil is: where is the actual observed strain tensor; is the strain tensor for the relative intact state; is the strain tensor for the fully adjusted state; is the disturbance function.

7. The method according to claim 1, wherein, In step 2, the natural physical and mechanical parameters are the material constants and initial state parameters of the constitutive model in the relative intact state and the fully adjusted state, which are used to calculate the mechanical response increment in parallel in each loading step.

8. The method according to claim 1, wherein, In step 3, the calculation variables include but are not limited to stress, strain, unit volume dissipation energy and equivalent plastic shear strain of each stratum unit.

9. The method according to claim 1, wherein the method is characterized by, In step 4, the double-threshold damage judgment method includes the following steps: Step 4.1, for each finite element unit, extract the unit volume dissipation energy and equivalent plastic shear strain data in the entire simulation process to form an "energy dissipation-plastic strain" data sequence; Step 4.2, under different working conditions, identify the curve inflection point of the data sequence, and extract the inflection point data including the critical dissipation energy value and the critical equivalent plastic shear strain value; Step 4.3, the multiple inflection points data are summarized as a sample set, the least square principle is used to construct a residual sum of squares objective function, and an optimization algorithm is used to solve the optimal fitting parameters, and the energy threshold expression in damage judgment is obtained based on the power function relationship: ， wherein is the critical dissipated energy; is the critical equivalent plastic shear strain; a *, b *, c * are the optimal fitting parameters; Step 4.4, for any computational element, if its simulated accumulated dissipated energy at the final time step D and the equivalent plastic shear strain If the following conditions are satisfied simultaneously, it is determined as a potential damage element: ， In the formula, Minimum discriminating strain set for engineering experience.

10. The method according to claim 9, wherein the method is characterized by, The residual sum of squares objective function described in step 4.3 is expressed as , The power function relationship is: where a, b, c are undetermined fitting parameters.

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