Shield freezing reinforced rock-soil body elastic-plastic model calculation method

Abstract

The invention discloses a method for calculating an elastic-plastic model of a shield freezing reinforced rock-soil body, which comprises the following steps of: training a support vector machine model by constructing a sample library of the rock-soil body which takes water content and rock-soil body temperature as inputs and takes hardening parameters and softening parameters as outputs; obtaining a support vector machine expression model of hardening parameters and a support vector machine expression model of softening parameters; obtaining a stress-strain constitutive expression of the rock-soil body based on the intelligent agent model; and finally, obtaining an elastic-plastic model of the frozen soil layer of the rock-soil body comprising the intelligent agent model. And in combination with the temperature of the rock-soil body, a ground surface displacement settlement value of frozen shield construction is obtained, and calculation of the elastic-plastic model of the shield frozen reinforced rock-soil body is completed. According to the method, the elastic-plastic mechanics of the soil body is well used, the freezing process and the thawing process are combined, the state of the shield freezing reinforced rock-soil body can be well reflected, the characteristics of freezing, thawing and softening of the soil body are described, and the method has a strong guiding effect on engineering practice.

Description

Technical Field

[0001] The invention relates to the technical field of shield construction, and in particular to a calculation method for an elastic-plastic model of a shield frozen reinforced rock and soil body. Background Art

[0002] For shield engineering construction in poor strata in complex environments with rich water, weak strata, shallow burials, and dense buildings and structures, artificial freezing is an effective method to reinforce poor soil strata. The core principle of the freezing method is to use artificial refrigeration technology to bury freezing pipes in the soil layer to be treated, and send low-temperature refrigerants into the water-rich strata around the underground space to be excavated, so that the water in the surrounding strata is in a temperature field below its freezing point, so that the water in the soil layer will continue to freeze to form ice, so that the soil particles in the stratum are cemented by ice to form a closed overall structure. The overall strength and elastic modulus of the soil are much greater than the soil structure before freezing. The freezing method will freeze the strata around the soil to be excavated into a closed continuum.

[0003] In fact, except for frost heave deformation, soil generally conforms to the elastic-plastic constitutive relationship. Low-temperature freezing and melting after freezing are equivalent to changing the mechanical properties of the soil, producing an effect of enhancement or damage degradation, which affects the original constitutive relationship, thereby bringing different mechanical response laws of rock and soil in shield construction. Although the current freezing method has been widely used in engineering, the calculation of freezing and thawing processes is generally frost heave force calculation, three-dimensional frost heave deformation calculation, etc., which cannot well integrate the elastic-plastic mechanical calculation of soil in the freezing and thawing process. Summary of the invention

[0004] The invention discloses a shield freezing reinforcement rock and soil body elastoplastic model calculation method to overcome the above technical problems.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A shield freezing reinforcement rock and soil elastic-plastic model calculation method comprises the following steps:

[0007] S1: Establishing an elastic-plastic model of the frozen soil layer of the shield frozen reinforced rock and soil body; the elastic-plastic model of the frozen soil layer includes an elastic-plastic constitutive model of the frozen soil layer considering the hardening parameters of the soil layer during freezing and an elastic-plastic constitutive model of the thawed soil layer considering the softening parameters of the soil layer during thawing;

[0008] S2: Construct a sample library of rock and soil with water content and rock and soil temperature as input and hardening parameters and softening parameters as output to train the support vector machine model, and then obtain the support vector machine expression model of the hardening parameters in the elastic-plastic constitutive model of the soil layer when frozen and the support vector machine expression model of the softening parameters in the elastic-plastic constitutive model of the soil layer when melted;

[0009] S3: obtaining a shear modulus after freezing based on an intelligent proxy model and a bulk modulus after freezing based on an intelligent proxy model according to a support vector machine expression model of hardening parameters;

[0010] According to the support vector machine expression model of softening parameters, the shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model are obtained;

[0011] S4: according to the shear modulus after freezing based on the intelligent proxy model and the bulk modulus after freezing based on the intelligent proxy model, a stress-strain constitutive expression considering hardening factors of the rock and soil body after freezing based on the intelligent proxy model is obtained;

[0012] According to the shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model, a stress-strain constitutive expression considering softening factors after freezing and melting of the rock and soil body based on the intelligent proxy model is obtained;

[0013] S5: according to the stress-strain constitutive expression of the rock-soil body after freezing based on the intelligent proxy model and the stress-strain constitutive expression of the rock-soil body after freezing and melting based on the intelligent proxy model and the softening factor, the elastic-plastic model of the frozen soil layer of the rock-soil body of the intelligent proxy model is obtained, including the elastic-plastic constitutive model of the soil layer when freezing and the elastic-plastic constitutive model of the soil layer when melting of the intelligent proxy model;

[0014] S6: According to the temperature of the rock and soil mass, the elastic-plastic constitutive model of the soil layer when frozen by the intelligent proxy model, and the elastic-plastic constitutive model of the soil layer when melted by the intelligent proxy model, the surface displacement and settlement values ​​of the frozen shield construction are obtained to complete the calculation of the elastic-plastic model of the rock and soil mass reinforced by the shield freezing.

[0015] Furthermore, the elastic-plastic constitutive model of the soil layer during freezing of the intelligent agent model is obtained as follows:

[0016]

[0017] The elastic-plastic constitutive model of the soil layer during melting of the intelligent agent model is obtained as follows:

[0018]

[0019] Furthermore, the method for establishing the elastic-plastic constitutive model of the soil layer considering freezing is as follows:

[0020] First: Get the soil hardening parameters during freezing as follows:

[0021]

[0022] In the formula, EH (w,T) is the elastic modulus of the rock and soil at the freezing temperature; E0 is the elastic modulus of the rock and soil before freezing; w is the water content; T is the rock and soil temperature; T0 is the freeze-thaw threshold of the rock and soil temperature;

[0023] Secondly: According to the soil hardening parameters during freezing, the stress-strain constitutive expression of the rock and soil mass after freezing is established as follows:

[0024]

[0025] Where: H is the stress tensor of the soil layer when frozen; is the tensor of elastic strain of soil layer when frozen; : is the symbol in tensor operation; D He is the elastic modulus matrix after freezing,

[0026] in,

[0027]

[0028] Where: I s represents a fourth-order symmetric tensor, G H represents the shear modulus after freezing; K H represents the bulk modulus after freezing; Represents the tensor product of two vectors multiplied together;

[0029] Finally: Based on the stress-strain constitutive expression considering the hardening factor after the rock mass is frozen, the elastic-plastic constitutive model of the soil layer during freezing is established as follows:

[0030]

[0031] at this time,

[0032] Where: F H is the plastic yield function of the soil layer when frozen; I1 is the first invariant of stress; J2(s) is the second invariant of deviatoric stress, s is the intermediate calculation parameter; I represents the unit matrix, where i,j represent the row and column labels of the identity matrix respectively; δ ij is the Kronecker symbol; e i Represents a matrix whose i-th row element is 1 and the rest are 0; represents the tensor product of two vectors; c is the cohesion; θ is the stress Lode angle; is the internal friction angle.

[0033] Furthermore, the method for establishing the elastic-plastic constitutive model of the soil layer during melting is as follows:

[0034] First: Get the softening parameters of the soil layer during melting as follows:

[0035]

[0036] Where S(w,T) represents the softening parameter; E S (w,T) represents the elastic modulus of the rock and soil when its temperature returns to room temperature from freezing temperature; E0 is the elastic modulus of the rock and soil before freezing.

[0037] Secondly: Based on the softening parameters of the soil layer during melting, the stress-strain constitutive expression considering the softening factor after freezing and melting of the rock and soil mass is established as follows:

[0038]

[0039] Where: S is the stress tensor of the soil layer during melting; is the tensor of elastic strain of the soil layer during melting; D Se is the elastic modulus matrix after softening;

[0040] in,

[0041]

[0042] Where I represents a fourth-order symmetric tensor; G S is the shear modulus after melting; K S is the bulk modulus after melting; G0 is the shear modulus of the rock mass; K0 is the bulk modulus of the rock mass; E0 is the elastic modulus of the rock mass before freezing; μ is the Poisson's ratio of the rock mass when it is not damaged; S(w,T) represents the softening parameter; w is the water content, and T is the temperature of the rock mass;

[0043] Finally: Based on the stress-strain constitutive expression considering the softening factor after the freezing and melting of the rock mass, the elastic-plastic constitutive model of the soil layer during melting is established as follows:

[0044]

[0045] at this time,

[0046] Furthermore, the support vector machine expression model of the hardening parameter and the support vector machine expression model of the softening parameter are obtained as follows:

[0047] SVMH(w,T)=H(w,T)

[0048] SVMS(w,T)=S(w,T)

[0049] Where: SVMH(w,T) represents the support vector machine expression of the hardening parameter H(w,T); SVMS(w,T) represents the support vector machine expression of the softening parameter S(w,T).

[0050] Furthermore, the shear modulus after freezing based on the intelligent proxy model and the bulk modulus after freezing based on the intelligent proxy model are obtained as follows:

[0051]

[0052] Where: SVMG H represents the shear modulus after freezing expressed by the support vector machine; SVMK H represents the bulk modulus after freezing expressed by the support vector machine;

[0053] The shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model are obtained as follows:

[0054]

[0055] Where: SVMG S represents the shear modulus after melting expressed by support vector machine; SVMK S represents the bulk modulus after melting expressed by the support vector machine.

[0056] Furthermore, the stress-strain constitutive expression of the rock and soil mass after freezing considering the hardening factor based on the intelligent agent model is obtained as follows:

[0057]

[0058] in,

[0059]

[0060] Where: SVMσ H represents the stress tensor of the soil layer during freezing expressed based on support vector machine; SVMD He represents the elastic modulus matrix after freezing expressed based on support vector machine;

[0061] The stress-strain constitutive expression considering the softening factor after freezing and thawing of the rock mass based on the intelligent agent model is obtained as follows:

[0062]

[0063] in,

[0064]

[0065] Where: SVMσ SRepresents the stress tensor of the soil layer during melting expressed based on support vector machine; SVMD Se Represents the softened elastic modulus matrix expressed based on support vector machine.

[0066] Beneficial effects: The present invention provides a method for calculating the elastic-plastic model of rock and soil reinforced by shield freezing. By constructing a sample library of rock and soil with water content and rock and soil temperature as input and hardening parameters and softening parameters as output, a support vector machine model is trained to obtain a support vector machine expression model of hardening parameters in the elastic-plastic constitutive model of the soil layer when frozen and a support vector machine expression model of softening parameters in the elastic-plastic constitutive model of the soil layer when melted; and then the shear modulus after freezing, the bulk modulus after freezing, the shear modulus after melting and the bulk modulus after melting based on the intelligent agent model are obtained; further, the stress-strain constitutive expression considering the hardening factor after freezing of the rock and soil based on the intelligent agent model and the stress-strain constitutive expression considering the softening factor after freezing and melting of the rock and soil based on the intelligent agent model can be obtained; finally, the elastic-plastic model of the frozen soil layer of the rock and soil including the intelligent agent model is obtained; combined with the temperature of the rock and soil, the surface displacement and settlement values ​​of the frozen shield construction are obtained to complete the calculation of the elastic-plastic model of the rock and soil reinforced by shield freezing. The present invention makes better use of the elastic-plastic mechanics of soil, combines the freezing and thawing processes, can better reflect the state of shield freezing reinforcement of rock and soil, describes the characteristics of soil freeze-thaw softening, and has a strong guiding role in engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0068] Figure 1 It is a flow chart of the calculation method of the shield freezing reinforcement rock and soil elastic-plastic model of the present invention;

[0069] Figure 2 It is a flow chart of the calculation method of the shield frozen rock and soil strengthening-softening elastoplastic model in the embodiment of the present invention;

[0070] Figure 3 Abaqus secondary development flow chart in an embodiment of the present invention;

[0071] Figure 4 It is a schematic diagram of the formation of a frozen soil wall in an embodiment of the present invention;

[0072] Figure 5 A diagram of a shield excavation model in an embodiment of the present invention;

[0073] Figure 6a The vertical displacement cloud diagram of the shield section when the freezing is not implemented in the embodiment of the present invention

[0074] Figure 6b The vertical displacement cloud diagram of the shield section at a freezing temperature of -5°C in the embodiment of the present invention

[0075] Figure 6c The vertical displacement cloud diagram of the shield section at a freezing temperature of -10°C in the embodiment of the present invention Figure 7 is a surface settlement curve during single-hole excavation in an embodiment of the present invention;

[0076] Figure 8a This is a distribution diagram of the softening zone after melting at a freezing temperature of -5°C in an embodiment of the present invention;

[0077] Figure 8b This is a distribution diagram of the softening zone after melting at a freezing temperature of -10°C in an embodiment of the present invention. DETAILED DESCRIPTION

[0078] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0079] This embodiment introduces a calculation method for the elastic-plastic model of shield frozen reinforced rock and soil. Figure 1 and Figure 2 As shown, the following steps are included:

[0080] S1: Establishing an elastic-plastic model of a frozen soil layer for shield freezing reinforcement of rock and soil mass during shield freezing method construction; the elastic-plastic model of the frozen soil layer includes an elastic-plastic constitutive model of the frozen soil layer taking into account the hardening parameters of the soil layer during freezing and an elastic-plastic constitutive model of the thawed soil layer taking into account the softening parameters of the soil layer during thawing;

[0081] Preferably, the method for establishing the elastic-plastic constitutive model of the soil layer considering freezing is as follows:

[0082] Specifically, in this embodiment, the rock and soil mass during the shield freezing method construction process is regarded as a continuous porous medium. Since the soil layer hardens during freezing, the degree of hardening is affected by the water content and the low temperature. Therefore, the hardening parameter is selected as a function of the water content and the freezing temperature, expressed as H(w,T). Freezing increases the elastic modulus and also has a certain impact on the plastic internal variable. When the temperature is lower than the freezing temperature of room temperature,

[0083] First: Get the soil hardening parameters during freezing as follows:

[0084]

[0085] In the formula, E H (w,T) is the elastic modulus of the rock and soil at the freezing temperature; E0 is the elastic modulus of the rock and soil before freezing; w is the water content; T is the rock and soil temperature; T0 is the freeze-thaw threshold of the rock and soil temperature;

[0086] Secondly: According to the soil hardening parameters during freezing, the stress-strain constitutive expression considering the hardening factor after the rock and soil body is frozen is established as follows:

[0087]

[0088] Where: H is the stress tensor of the soil layer when frozen; is the tensor of the elastic strain of the soil layer when it is frozen; : is the symbol in tensor operations, representing double point multiplication, which means that the components are multiplied in a certain order; D He is the elastic modulus matrix after freezing,

[0089] in,

[0090]

[0091] Among them, G H , K H The relationship with G0 and K0 is expressed as:

[0092]

[0093] Where: I s represents a fourth-order symmetric tensor, G H represents the shear modulus after freezing; K H represents the bulk modulus after freezing; Represents the tensor product of two vectors multiplied together;

[0094] Finally: Based on the stress-strain constitutive expression considering the hardening factor after the rock mass is frozen, the elastic-plastic constitutive model of the soil layer during freezing is established as follows:

[0095] Specifically, since the internal friction angle is insensitive to changes in freezing hardening and melting softening, the impact is small, so only the effect of damage on cohesion is considered. When the soil layer hardens during freezing, its elastoplastic constitutive model is:

[0096]

[0097] in,

[0098] J2(s)=(1 / 2)s:s

[0099] at this time,

[0100] Where: F H is the plastic yield function of the soil layer when frozen; I1 is the first invariant of stress; J2(s) is the second invariant of deviatoric stress, s is the intermediate calculation parameter; I represents the unit matrix, that is, all elements on the main diagonal are 1, where, i,j represent the row and column labels of the identity matrix, respectively, where i,j=1,2,3,δ ij is the Kronecker symbol; e i Represents a matrix whose i-th row element is 1 and the rest are 0; represents the tensor product of two vectors; c is the cohesion; θ is the stress Lode angle; is the internal friction angle;

[0101] Preferably, the method for establishing the elastic-plastic constitutive model of the soil layer during melting is as follows:

[0102] Specifically, when the frozen soil layer returns to its original temperature from the freezing temperature, that is, when it melts, the soil will be damaged and softened, which is manifested as a decrease in the elastic modulus. The softening parameter is selected as a function of the water content w and the freezing temperature T, expressed as S(w,T). When the temperature T returns to the original room temperature from the freezing temperature, first: the softening parameters of the soil layer during melting are obtained as follows:

[0103]

[0104] Where S(w,T) represents the softening parameter; E S (w,T) represents the elastic modulus of the rock and soil when its temperature recovers from the freezing temperature to the original room temperature (0 degrees); E0 is the elastic modulus of the rock and soil before freezing.

[0105] Secondly: Based on the softening parameters of the soil layer during melting, the stress-strain constitutive expression considering the softening factor after freezing and melting of the rock and soil mass is established as follows:

[0106]

[0107] Where: S is the stress tensor of the soil layer during melting; is the tensor of elastic strain of the soil layer during melting; D Se is the elastic modulus matrix after softening;

[0108] in,

[0109]

[0110] GS , K S The relationship with G0 and K0 is expressed as:

[0111]

[0112] In the formula, I S represents a symmetric tensor of order four; G S is the shear modulus after melting; K S is the bulk modulus after melting; G0 is the shear modulus of the rock mass; K0 is the bulk modulus of the rock mass; E0 is the elastic modulus of the rock mass before freezing; μ is the Poisson's ratio of the rock mass when it is not damaged; S(w,T) represents the softening parameter; w is the water content, and T is the temperature of the rock mass;

[0113] Finally: According to the stress-strain constitutive expression considering the softening factor after the freezing and melting of the rock mass, the elastic-plastic constitutive model of the soil layer during melting is established: At this time, the soil layer during melting undergoes damage and softening:

[0114]

[0115] at this time,

[0116] Specifically, the elastic-plastic model of the frozen soil layer in this embodiment is solved by the Newton-Raphson method of the finite element incremental method.

[0117] Specifically, in the process of calculating the elastic-plastic model of the frozen soil layer, it is difficult to give an explicit formula for the hardening parameter H(w,T) and the softening parameter S(w,T). The formulas for the hardening parameter H(w,T) and the softening parameter S(w,T) are crucial for calculating the elastic-plastic model of the frozen soil layer. This embodiment uses the SVMH(w,T) and SVMS(w,T) intelligent proxy models to replace the original formulas. The steps for establishing the SVMH(w,T) intelligent proxy model are as follows:

[0118] For different combinations of water content w and T parameters, the elastic modulus of the corresponding specimens was measured by uniaxial tests through freezing test and melting test. The hardening parameter and softening parameter were calculated according to the following formulas:

[0119] S2: Construct a sample library of rock and soil bodies with different water contents w and rock and soil body temperatures T as inputs and hardening parameters H(w,T) and softening parameters S(w,T) as outputs to train the support vector machine model, and then obtain the support vector machine SVM expression model of the hardening parameter H(w,T) in the elastic-plastic constitutive model of the soil layer when frozen and the support vector machine SVM expression model of the softening parameter S(w,T) in the elastic-plastic constitutive model of the soil layer when melted;

[0120] Specifically, the sample library of rock and soil mass established in this embodiment is as follows:

[0121] {w1,T1;H1(w1,T1),S1(w1,T1)}, {w2,T2;H2(w2,T2),S2(w2,T2)},

[0122] {w3,T3;H3(w3,T3),S3(w3,T3)},…,{w m ,T m ;H m (w m ,T m ),S m (w m ,T m )}、

[0123] {w m+1 ,T m+1 ;H m+1 (w m+1 ,T m+1 ),S m+1 (w m+1 ,T m+1 )}、…、{w n ,T n ;H n (w n ,T n ),S n (w n ,T n )}(11)

[0124] Among them, w n represents the water content of the nth sample; T n represents the temperature of the nth sample; H n represents the hardening parameter of the nth sample; S n represents the softening parameter of the nth sample; n is the total number of samples of the rock and soil body, and m is the number of learning samples, where n>m>1.

[0125] Specifically, this embodiment uses the rock and soil sample library to perform machine learning training on the support vector machine model. Among them, {w1, T1; H1 (w1, T1), S1 (w1, T1)}, {w2, T2; H2 (w2, T2), S2 (w2, T2)}, {w3, T3; H3 (w3, T3), S3 (w3, T3)}, ..., {w m ,T m ;H m (w m ,T m ),S m (w m ,T m)} is a learning sample; {w m+1 ,T m+1 ;H m+1 (w m+1 ,T m+1 ),S m+1 (w m+1 ,T m+1 )}、…、{w n ,T n ;H n (w n ,T n ),S n (w n ,T n )} is the prediction test sample.

[0126] Specifically, this embodiment adopts a cross-validation method to select the hyperparameters of the SVM, including the kernel parameter σ and the penalty factor C. The goal of cross-validation is to minimize the absolute error between the predicted value and the actual value.

[0127] Preferably, the support vector machine SVM expression model of the hardening parameter H(w,T) and the support vector machine SVM expression model of the softening parameter S(w,T) are obtained as follows:

[0128] SVMH(w,T)=H(w,T) (T-11)

[0129] SVMS(w,T)=S(w,T) (T-12)

[0130] Where: SVMH(w,T) represents the support vector machine expression of the hardening parameter H(w,T); SVMS(w,T) represents the support vector machine expression of the softening parameter S(w,T);

[0131] S3: according to the support vector machine SVM expression model of the hardening parameter H(w,T), the shear modulus after freezing based on the intelligent agent model and the bulk modulus after freezing based on the intelligent agent model are obtained;

[0132] According to the support vector machine (SVM) expression model of the softening parameter S(w,T), the shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model are obtained;

[0133] Preferably, the shear modulus after freezing based on the intelligent proxy model and the bulk modulus after freezing based on the intelligent proxy model are obtained as follows:

[0134]

[0135] Where: SVMG H represents the shear modulus after freezing expressed by the support vector machine; SVMK Hrepresents the bulk modulus after freezing expressed by the support vector machine;

[0136] The shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model are obtained as follows:

[0137]

[0138] Where: SVMG S represents the shear modulus after melting expressed by support vector machine; SVMK S represents the bulk modulus after melting expressed by the support vector machine;

[0139] S4: according to the shear modulus after freezing based on the intelligent proxy model and the bulk modulus after freezing based on the intelligent proxy model, a stress-strain constitutive expression considering hardening factors of the rock and soil body after freezing based on the intelligent proxy model is obtained;

[0140] According to the shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model, a stress-strain constitutive expression considering softening factors after freezing and melting of the rock and soil body based on the intelligent proxy model is obtained;

[0141] Preferably, the stress-strain constitutive expression of the rock and soil mass after freezing considering the hardening factor based on the intelligent agent model is obtained as follows:

[0142]

[0143] in,

[0144]

[0145] Where: SVMσ H represents the stress tensor of the soil layer during freezing expressed based on support vector machine; SVMD H "e" represents the elastic modulus matrix after freezing expressed based on support vector machine;

[0146] The stress-strain constitutive expression considering the softening factor after freezing and thawing of the rock mass based on the intelligent agent model is obtained as follows:

[0147]

[0148] in,

[0149]

[0150] Where: SVMσ S Represents the stress tensor of the soil layer during melting expressed based on support vector machine; SVMD S"e" represents the elastic modulus matrix after softening expressed based on support vector machine;

[0151] S5: according to the stress-strain constitutive expression of the rock-soil body after freezing considering the hardening factor based on the intelligent proxy model and the stress-strain constitutive expression of the rock-soil body after freezing and melting considering the softening factor based on the intelligent proxy model, the elastic-plastic model of the frozen soil layer of the rock-soil body of the intelligent proxy model is obtained, that is, the strengthening-softening elastic-plastic model of the rock-soil body of the shield construction of the intelligent proxy model, including the elastic-plastic constitutive model of the soil layer when freezing and the elastic-plastic constitutive model of the soil layer when melting of the intelligent proxy model;

[0152] Specifically, substitute formula (T-11) and (T-11) into formula (T-3), (T-4), (T-8), (T-9), (T-10), and (T-5). The intelligent agent model of shield construction rock and soil strengthening-softening elastoplastic model calculation company is obtained. The corresponding hardening calculation after freezing is shown in formula (T-13), (T-14), and (T-17). The corresponding hardening calculation after freezing is shown in formula (T-15), (T-16), and (T-18).

[0153] Preferably, the elastic-plastic constitutive model of the soil layer during freezing of the intelligent agent model is obtained as follows:

[0154]

[0155] The elastic-plastic constitutive model of the soil layer during melting of the intelligent agent model is obtained as follows:

[0156]

[0157] S6: According to the temperature of the rock and soil mass, the elastic-plastic constitutive model of the soil layer when frozen by the intelligent proxy model and the elastic-plastic constitutive model of the soil layer when melted by the intelligent proxy model, based on the Newton-Raphson method, the surface displacement and settlement values ​​of the frozen shield construction are obtained to complete the calculation of the elastic-plastic model of the rock and soil mass reinforced by the shield freezing.

[0158] Specifically, the elastic-plastic model of the frozen soil layer of the rock and soil body of the intelligent proxy model, that is, the strengthening-softening elastic-plastic model of the shield construction rock and soil body of the intelligent proxy model, is embedded in the finite element calculation method; wherein, the strengthening-softening elastic-plastic model of the rock and soil body also needs to be programmed through the finite element stress reflection algorithm. Figure 3, combined with the secondary development platform provided by ABAQUS, the corresponding UMAT subroutine is written in FORTRAN language. When ABAQUS calls the user subroutine, it will use two actual parameters KSTEP and KINC to transfer the current STEP and INCREMENT to the user subroutine, thereby realizing the interconnection between the main program and the UMAT subroutine. The Newton-Raphson iterative process of the Newton-Raphson method is adopted. After knowing the result of the mth iteration step, the calculation process of the m+1th incremental step is as follows: where m represents the number of the iteration step.

[0159] 1. Initialize the external force vector of step m+1 to F m+1 =F m +△F, and initialize the node displacement vector U at the same time m+1 =U m ;

[0160] Among them, F m represents the external force vector at the end of the mth iteration step; U m represents the node displacement vector at the end of the mth iteration step; △F represents the external force increment at the m+1th iteration step;

[0161] 2. Start the overall equilibrium iteration of the structure, first calculate the residual stress of the structure Among them, F int It is the internal force of the structure; Represents the residual stress of the structure;

[0162] 3. Then the consistent stiffness matrix forms the overall stiffness matrix K to solve the updated node displacement increments The strain increment △ε is calculated m+1 , and then start to check the convergence of the overall equilibrium iteration. Among them, the calculation of the elastic stiffness matrix is ​​realized by formulas (2) and (6). The elastic-plastic stiffness matrix needs to be calculated by the plastic stress reflection algorithm combined with (9) and (10).

[0163] if It does not converge, and iterates again. Where TOL represents the set convergence error; ΔU m+1 Represents the node displacement increment after the m+1th iteration step;

[0164] 4. Start stress update. This step is implemented through the UMAT subroutine. The strain increment calculated in the previous step is transferred to the subroutine. According to the stress regression mapping algorithm in the previous section, the updated stress and consistent stiffness matrix are calculated, and then a new round of iteration is started.

[0165] 5. At the end of the incremental step, update the displacement of the m+1 step, U m+1 =U m+ΔU m+1 , U m Represents the surface displacement and settlement value after the mth iteration step;.

[0166] Specifically, the steps of numerical simulation of shield construction in frozen strata in this embodiment are as follows:

[0167] (a) Establish a finite element model for shield construction in frozen strata;

[0168] (b) Setting boundary conditions for shield excavation;

[0169] (c) Ground parameters for shield construction;

[0170] (d) Conduct numerical simulation of shield construction;

[0171] (e) Solving the elastic-plastic finite element method; that is, calling the algorithm of the above frozen soil layer freezing hardening and melting softening model;

[0172] (f) Output the calculation results of surface displacement and settlement of cryoshield construction.

[0173] The calculation model of this embodiment takes into account the strengthening of low-temperature frozen soil and the softening of frozen and thawed soil, and provides an intelligent determination method based on support vector machine parameters, an Abaqus finite element model secondary development method, and a finite element numerical calculation method for frozen soil shield construction. In a specific embodiment of the present invention, the process of soil freezing is as follows Figure 4 As shown. The refrigerant liquid vaporizes directly in the freezing pipe and absorbs a large amount of heat in the stratum. At this time, the frozen soil wall can be formed in a very short time. The shield excavation construction in the frozen soil wall has the characteristics of fast speed and large bearing capacity of the frozen soil wall. Figure 5 This is the excavation model of the shield tunnel after freezing. Based on this established model, unit grids are divided and the method of this embodiment is used to perform finite element calculation. Figure 6a , Figure 6b , Figure 6c The vertical displacement cloud diagram of the shield section at different freezing temperatures is shown. As can be seen from the figure, as the freezing temperature changes from unfrozen, freezing temperature -5℃ to freezing temperature -10℃, the displacement of the surrounding rock top arch changes from 30.2mm, 15.9mm to 7.7mm. It can be seen that the surrounding rock displacement of the shield tunnel is decreasing with freezing. Figure 7 Conditions 1, 2, and 3 represent the three conditions where the freezing temperature is from never freezing, freezing temperature -5°C to freezing temperature -10°C. It can be seen that as the freezing temperature decreases, the surface settlement curve during single-hole excavation also decreases continuously. Figure 8a and 8bIt is the distribution diagram of the softening zone of shield tunneling after melting at a freezing temperature of -5°C and after melting at a freezing temperature of -10°C. The greater the degree of freezing, the greater the softening after melting. It can be seen from the figure that the model established in this embodiment can describe the characteristics of freeze-thaw softening of soil.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A calculation method for the elastic-plastic model of shield frozen reinforced rock and soil, characterized in that: The steps include: S1: Establishing an elastic-plastic model of the frozen soil layer of the shield frozen reinforced rock and soil body; the elastic-plastic model of the frozen soil layer includes an elastic-plastic constitutive model of the frozen soil layer considering the hardening parameters of the soil layer during freezing and an elastic-plastic constitutive model of the thawed soil layer considering the softening parameters of the soil layer during thawing; S2: Construct a sample library of rock and soil with water content and rock and soil temperature as input and hardening parameters and softening parameters as output to train the support vector machine model, and then obtain the support vector machine expression model of the hardening parameters in the elastic-plastic constitutive model of the soil layer when frozen and the support vector machine expression model of the softening parameters in the elastic-plastic constitutive model of the soil layer when melted; S3: obtaining a shear modulus after freezing based on an intelligent proxy model and a bulk modulus after freezing based on an intelligent proxy model according to a support vector machine expression model of hardening parameters; According to the support vector machine expression model of the softening parameter, the shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model are obtained; S4: according to the shear modulus after freezing based on the intelligent proxy model and the bulk modulus after freezing based on the intelligent proxy model, a stress-strain constitutive expression considering hardening factors of the rock and soil body after freezing based on the intelligent proxy model is obtained; According to the shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model, a stress-strain constitutive expression considering softening factors after freezing and melting of the rock and soil body based on the intelligent proxy model is obtained; S5: according to the stress-strain constitutive expression of the rock-soil body after freezing based on the intelligent proxy model and the stress-strain constitutive expression of the rock-soil body after freezing and melting based on the intelligent proxy model and the softening factor, the elastic-plastic model of the frozen soil layer of the rock-soil body of the intelligent proxy model is obtained, including the elastic-plastic constitutive model of the soil layer when freezing and the elastic-plastic constitutive model of the soil layer when melting of the intelligent proxy model; S6: According to the temperature of the rock and soil mass, the elastic-plastic constitutive model of the soil layer when frozen by the intelligent proxy model, and the elastic-plastic constitutive model of the soil layer when melted by the intelligent proxy model, the surface displacement and settlement values ​​of the frozen shield construction are obtained to complete the calculation of the elastic-plastic model of the rock and soil mass reinforced by the shield freezing.

2. The calculation method of the elastoplastic model of shield frozen reinforced rock and soil according to claim 1 is characterized in that: The elastic-plastic constitutive model of the soil layer during freezing of the intelligent agent model is obtained as follows: The elastic-plastic constitutive model of the soil layer during melting of the intelligent agent model is obtained as follows:

3. The calculation method of the elastic-plastic model of shield frozen reinforced rock and soil according to claim 1 is characterized in that: The method for establishing the elastic-plastic constitutive model of the soil layer considering freezing is as follows: First: Get the soil hardening parameters during freezing as follows: In the formula, E H (w,T) is the elastic modulus of the rock and soil at the freezing temperature; E0 is the elastic modulus of the rock and soil before freezing; w is the water content; T is the rock and soil temperature; T0 is the freeze-thaw threshold of the rock and soil temperature; Secondly: According to the soil hardening parameters during freezing, the stress-strain constitutive expression of the rock and soil mass after freezing is established as follows: Where: H is the stress tensor of the soil layer when frozen; is the tensor of elastic strain of soil layer when frozen; : is the symbol in tensor operation; D He is the elastic modulus matrix after freezing, in, Where: I s represents a fourth-order symmetric tensor, G H represents the shear modulus after freezing; K H represents the bulk modulus after freezing; Represents the tensor product of two vectors multiplied together; Finally: Based on the stress-strain constitutive expression considering the hardening factor after the rock and soil mass is frozen, the elastic-plastic constitutive model of the soil layer during freezing is established as follows: at this time, Where: F H is the plastic yield function of the soil layer when frozen; I1 is the first invariant of stress; J2(s) is the second invariant of deviatoric stress, s is the intermediate calculation parameter; I represents the unit matrix, where i,j represent the row and column labels of the unit matrix respectively; δ ij is the Kronecker symbol; e i Represents a matrix whose i-th row element is 1 and the rest are 0; represents the tensor product of two vectors; c is the cohesion; θ is the stress Lode angle; is the internal friction angle.

4. The calculation method of the elastic-plastic model of shield frozen reinforced rock and soil according to claim 1 is characterized in that: The method for establishing the elastic-plastic constitutive model of the soil layer during melting is as follows: First: Get the softening parameters of the soil layer during melting as follows: Where S(w,T) represents the softening parameter; E S (w,T) represents the elastic modulus of the rock and soil when the temperature of the rock and soil returns to room temperature from the freezing temperature; E0 is the elastic modulus of the rock and soil before freezing; Secondly: Based on the softening parameters of the soil layer during melting, the stress-strain constitutive expression considering the softening factor after freezing and melting of the rock and soil mass is established as follows: Where: S is the stress tensor of the soil layer during melting; is the tensor of elastic strain of the soil layer during melting; D Se is the elastic modulus matrix after softening; in, Where I represents a fourth-order symmetric tensor; G S is the shear modulus after melting; K S is the bulk modulus after melting; G0 is the shear modulus of the rock mass; K0 is the bulk modulus of the rock mass; E0 is the elastic modulus of the rock mass before freezing; μ is the Poisson's ratio of the rock mass when it is not damaged; S(w,T) represents the softening parameter; w is the water content, and T is the temperature of the rock mass; Finally: Based on the stress-strain constitutive expression considering the softening factor after the freezing and melting of the rock mass, the elastic-plastic constitutive model of the soil layer during melting is established as follows: at this time, 5. The calculation method of the elastoplastic model of shield frozen reinforced rock and soil according to claim 1 is characterized in that: The support vector machine expression model for obtaining hardening parameters and the support vector machine expression model for softening parameters are as follows: SVMH(w,T)=H(w,T) SVMS(w,T)=S(w,T) Where: SVMH(w,T) represents the support vector machine expression of the hardening parameter H(w,T); SVMS(w,T) represents the support vector machine expression of the softening parameter S(w,T).

6. The calculation method of the elastic-plastic model of shield frozen reinforced rock and soil according to claim 1 is characterized in that: The shear modulus after freezing based on the intelligent proxy model and the bulk modulus after freezing based on the intelligent proxy model are obtained as follows: Where: SVMG H represents the shear modulus after freezing expressed by the support vector machine; SVMK H represents the bulk modulus after freezing expressed by the support vector machine; The shear modulus after melting based on the intelligent proxy model and the bulk modulus after melting based on the intelligent proxy model are obtained as follows: Where: SVMG S represents the shear modulus after melting expressed by support vector machine; SVMK S represents the bulk modulus after melting expressed by the support vector machine.

7. The calculation method of the elastoplastic model of shield frozen reinforced rock and soil according to claim 1 is characterized in that: The stress-strain constitutive expression of the rock and soil mass after freezing considering the hardening factor based on the intelligent agent model is obtained as follows: in, Where: SVMσ H represents the stress tensor of the soil layer during freezing expressed based on support vector machine; SVMD He represents the elastic modulus matrix after freezing expressed based on support vector machine; The stress-strain constitutive expression considering the softening factor after freezing and thawing of the rock mass based on the intelligent agent model is obtained as follows: in, Where: SVMσ S Represents the stress tensor of the soil layer during melting expressed based on support vector machine; SVMD Se Represents the elastic modulus matrix after softening expressed based on support vector machine.

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