A method for predicting stress deformation of a confined space foundation pit enclosure structure

Abstract

The application relates to a stress deformation prediction method for a confined space foundation pit retaining structure, which comprises the following steps: S1: inputting soil body parameters and foundation pit design parameters to generate a stiffness matrix; S2: determining initial soil pressure parameters and calculating lateral deformation of the retaining structure; S3: according to the confined space of the foundation soil, updating the stiffness matrix; based on the updated stiffness matrix, performing second calculation; S4: judging whether an error Delta u reaches a precision requirement, if yes, turning to S5, and if not, repeating S3, and iteratively calculating until the error Delta u meets the precision requirement; S5: after the stiffness matrix is determined, calculating soil body shear stress, and further calculating shear strain and soil body shear stiffness; S6: calculating a soil spring elastic modulus k, and updating the stiffness matrix; step S7: recording u T ; then returning to S1 to enter next excavation stage calculation; S8: after the calculation to a design excavation depth, outputting the stiffness matrix, the shear strain and a bending moment M, so as to evaluate stress deformation conditions of the foundation pit retaining structure. The method is favorable for improving the precision of stress deformation prediction of the confined space foundation pit retaining structure.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit engineering, and in particular to a method for predicting the stress and deformation of a confined space foundation pit retaining structure coupled with nonlinear soil stiffness. Background Art

[0002] With the rapid development of urban construction and the further development of underground space, more and more foundation pit projects are adjacent to urban buildings. When such foundation pits are excavated, the pile foundations of adjacent buildings, overpasses, etc. will generate additional internal forces and additional deformations due to the unloading of the foundation pit. Excessive deformation may threaten the safety of the retaining structure and superstructure. Therefore, studying the stress and deformation of the retaining structure caused by foundation pit excavation is of great engineering significance.

[0003] Currently, the main methods for predicting deformation of foundation pit retaining structures include classical methods (such as the equivalent beam method and the plastic hinge method), analytical methods (such as the Yamashiro Kunio method), two-dimensional or three-dimensional finite element methods that treat the soil as a solid element, and the elastic foundation beam method. Compared to other methods, the elastic foundation beam method has many advantages, such as a simple model, clear loads, a small number of required calculation parameters, and the ability to leverage engineering experience, and is therefore widely used in actual foundation pit engineering design. However, the traditional elastic foundation beam method ignores the effects of confined soil space, soil stiffness hardening, support stiffness, and the shear stiffness attenuation characteristics of the soil at small strains, resulting in significant discrepancies between the calculated displacement of the retaining structure and the actual displacement. Summary of the Invention

[0004] The object of the present invention is to provide a method for predicting the stress and deformation of a confined space foundation pit retaining structure, which is beneficial to improving the accuracy of predicting the stress and deformation of a confined space foundation pit retaining structure.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for predicting the stress and deformation of a confined space foundation pit retaining structure, comprising the following steps:

[0006] Step S1: Based on the elastic foundation beam model, input the soil parameters and foundation pit design parameters interpreted based on the SPT in-situ test to generate the stiffness matrix ;

[0007] Step S2: Determine the initial earth pressure parameters , combined with the stiffness matrix , calculate the lateral deformation of the enclosure structure ;

[0008] Step S3: According to the lateral deformation of the enclosure structure , considering the confined space of foundation soil, update the soil pressure parameters ; Based on the updated earth pressure parameters , combined with the stiffness matrix , calculate the lateral deformation of the enclosure structure again ;

[0009] Step S4: Determine whether the lateral deformation error Δu of the enclosure structure calculated twice before and after meets the accuracy requirement. If yes, go to step S5. Otherwise, repeat step S3 and iteratively calculate the lateral deformation of the enclosure structure. Until the lateral deformation error Δu of the enclosure structure calculated twice before and after meets the accuracy requirements;

[0010] Step S5: Determine the lateral deformation of the enclosure structure Then, the soil shear stress τ is calculated, and then the shear strain is calculated. and soil shear stiffness;

[0011] Step S6: Calculate the shear stiffness attenuation characteristics of the soil in the coupled small strain stage and the soil spring elastic modulus k of the soil hardening, and update the stiffness matrix ;

[0012] Step S7: Record the displacement u of the retaining structure at the installation support position when excavation reaches the current depth T ; Then return to step S1 and enter the next excavation stage calculation until the designed excavation depth;

[0013] Step S8: After calculating the designed excavation depth, output the soil pressure parameters , lateral deformation of the retaining structure and bending moment M, to evaluate the stress and deformation of the foundation pit retaining structure;

[0014] Furthermore, in step S1, the soil parameters interpreted based on the SPT in-situ test are:

[0015]

[0016] in, is the effective cohesion of soil, is the initial overlying effective stress of the soil layer, is the effective internal friction angle of soil, is the standard penetration number, is the corrected standard penetration number, is standard atmospheric pressure, is the elastic modulus of soil under reference effective confining pressure, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness, is the initial shear stiffness, is the soil cohesion, is the effective major principal stress, is the static earth pressure coefficient, is the soil density, is the Poisson's ratio of soil, is the soil overconsolidation ratio.

[0017] Furthermore, in step S1, the elastic foundation beam model is:

[0018]

[0019] Where EI is the bending stiffness of the enclosure structure, u is the displacement of the enclosure structure, z e Calculate the depth for the enclosure structure, is the elastic modulus of soil spring, is the horizontal support stiffness of the foundation pit, is the difference between the active earth pressure and the passive earth pressure on the retaining structure. The displacement of the retaining structure at the installation support position when the foundation pit is excavated to the corresponding depth;

[0020] Convert the elastic foundation beam model into matrix form: , and thus can be achieved through and calculate ;

[0021] The stiffness matrix Expressed as:

[0022]

[0023] in, , 、 、 are intermediate variables. Calculate unit lengths for enclosure structures; represents the elastic modulus of the i-th soil spring, , is the total number of soil springs.

[0024] Furthermore, in step S3, the soil pressure parameter The update method is:

[0025] For the case where the soil exerts pressure on the surrounding structure, the earth pressure parameter Represents the active earth pressure parameter ; For the case where the retaining structure exerts pressure on the soil, the soil pressure parameter Represents the passive earth pressure parameter ;

[0026] According to the lateral deformation of the enclosure structure Calculate the active earth pressure parameters to be corrected and the passive earth pressure parameters to be corrected :

[0027]

[0028]

[0029] in, is the active earth pressure parameter to be corrected The i-th element in , is the passive earth pressure parameter to be corrected The i-th element in , Lateral deformation of the retaining structure The i-th element in ; is the elastic modulus of the soil spring in the active zone, is the elastic modulus of the passive zone soil spring, is the static earth pressure at the soil calculation depth, is the limit value of active earth pressure, is the limit value of passive earth pressure;

[0030] Considering the confined space of foundation soil and the arching effect of soil behind the wall, the active earth pressure correction coefficient β a and the passive earth pressure correction factor β p Active earth pressure parameters to be corrected and the passive earth pressure parameters to be corrected Correction is performed to obtain the corrected active earth pressure parameters and passive earth pressure parameters , that is, the updated earth pressure parameters are obtained ;

[0031]

[0032]

[0033]

[0034]

[0035] Among them, B is the excavation width of the foundation pit, H is the excavation depth of the foundation pit, is the internal friction angle of soil, c is the cohesion of soil, δ is the friction angle of soil-structure interface, is the soil weight, and μ is the soil-structure interface coefficient.

[0036] Furthermore, in step S4, the accuracy requirement for the lateral deformation error Δu of the enclosure structure calculated twice before and after is as follows:

[0037]

[0038] in, 、 Respectively sequence The lateral deformation of the enclosure structure calculated for the second time is Indicates the calculation of the Euclidean distance between matrices, is the set accuracy threshold.

[0039] Furthermore, in step S5, the soil transverse shear stress and the soil longitudinal shear stress are calculated according to the following formula:

[0040]

[0041]

[0042] in, is the transverse shear stress, is the longitudinal shear stress, F is the transverse concentrated force, Q is the longitudinal concentrated force, is the coordinate of the lateral concentrated force F, is the coordinate of the longitudinal concentrated force Q; x and z are the abscissa and ordinate of the resultant force of F and Q; , ; is the Poisson's ratio of soil;

[0043] The soil shear stress τ is obtained by synthesizing the transverse shear stress and the longitudinal shear stress;

[0044] Then the shear strain is calculated as follows :

[0045]

[0046] in, is the initial shear stiffness, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness;

[0047] In the small strain stage, the soil shear stiffness decays with the shear strain. After the shear strain is calculated, the soil shear stiffness is calculated according to the following formula: :

[0048]

[0049] in, is the soil shear stiffness.

[0050] Furthermore, in step S6, the soil shear stiffness attenuation characteristic and the soil spring elastic modulus k of the soil hardening in the coupled small strain stage are calculated according to the following formula:

[0051]

[0052] in, is the strain condition correction coefficient, is the elastic modulus of soil, is the Poisson's ratio of soil, B is the excavation width of foundation pit, and EI is the flexural stiffness of the retaining structure;

[0053] In the large strain stage, When considering the soil stiffness hardening characteristics, the soil elastic modulus The calculation formula is as follows:

[0054]

[0055] in, is the elastic modulus of soil under reference effective confining pressure, is the effective cohesion of soil, is the effective internal friction angle of soil, is the lateral effective stress of the soil, is the reference effective confining pressure, m represents the correlation between stiffness and stress level; is the cutoff value, which is calculated as follows:

[0056]

[0057] in, is the initial shear stiffness, is the unloading-reloading shear stiffness, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness;

[0058] In the small strain stage, When the soil elastic modulus The calculation formula is as follows:

[0059]

[0060] in, is the soil rebound Poisson’s ratio, is the soil shear stiffness.

[0061] Furthermore, in step S8, the calculation formula of the bending moment M of the enclosure structure is as follows:

[0062]

[0063] Where EI is the bending stiffness of the enclosure structure, u is the displacement of the enclosure structure, z e Calculate the depth for the enclosure.

[0064] The present invention also provides a stress and deformation prediction system for a confined space foundation pit retaining structure, comprising a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the above-mentioned method can be implemented.

[0065] The present invention also provides a computer-readable storage medium having computer program instructions stored thereon, which implement the above method when the computer program instructions are executed by a processor.

[0066] Compared with the existing technology, the present invention has the following beneficial effects: The present invention proposes a method for predicting the stress and deformation of a confined space foundation pit retaining structure coupled with soil stiffness nonlinearity. The method obtains soil parameters based on SPT in-situ testing, establishes an elastic foundation beam model and generates a dynamic stiffness matrix, proposes a confined space soil pressure model, and achieves lateral deformation convergence through bidirectional iterative calculation of deformation and soil pressure. It integrates the characteristics of soil stiffness hardening and soil shear stiffness attenuation in the small strain stage, and corrects the elastic modulus and stiffness matrix of the foundation beam in real time to reflect the stiffness nonlinearity. Through the support displacement-additional stress feedback mechanism, the soil spring and support spring states are dynamically updated to achieve simulation of the entire layered excavation process. This method fully considers most of the factors affecting soil parameters, improves the accuracy of soil pressure prediction for deep foundation pit retaining structures, and is suitable for foundation pit engineering design in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a flow chart for implementing a method for predicting stress and deformation of a confined space foundation pit retaining structure provided by an embodiment of the present invention;

[0068] Figure 2 is a plan view of a foundation pit in an embodiment of the present invention;

[0069] Figure 3 Schematic diagram of SPT in-situ test values ​​in an embodiment of the present invention;

[0070] Figure 4 This is a cross-sectional view of a foundation pit at a monitoring point in an embodiment of the present invention;

[0071] Figure 5 Schematic diagram of the bending moment of the retaining structure calculated to the designed excavation depth in an embodiment of the present invention;

[0072] Figure 6 It is a comparison diagram of the calculated value of the earth pressure of the retaining structure and the active earth pressure limit value, the static earth pressure distribution, and the comparison diagram of the calculated value of the lateral displacement and the monitored value in the embodiment of the present invention. DETAILED DESCRIPTION

[0073] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0074] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0075] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0076] like Figure 1 As shown, this embodiment provides a method for predicting the stress and deformation of a confined space foundation pit retaining structure, comprising the following steps:

[0077] Step S1: Based on the elastic foundation beam model, input the soil parameters and foundation pit design parameters interpreted based on the SPT in-situ test to generate the stiffness matrix .

[0078] The soil parameters interpreted based on the SPT in-situ test are:

[0079]

[0080] in, is the effective cohesion of soil, is the initial overlying effective stress of the soil layer, is the effective internal friction angle of soil, is the standard penetration number, is the corrected standard penetration number, is standard atmospheric pressure, is the elastic modulus of soil under reference effective confining pressure, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness, is the initial shear stiffness, is the soil cohesion, is the effective major principal stress, is the static earth pressure coefficient, is the soil density, is the Poisson's ratio of soil, is the soil overconsolidation ratio.

[0081] The elastic foundation beam model is:

[0082]

[0083] Where EI is the bending stiffness of the enclosure structure, u is the displacement of the enclosure structure, z e Calculate the depth for the enclosure structure, is the elastic modulus of soil spring, is the horizontal support stiffness of the foundation pit, is the difference between the active earth pressure and the passive earth pressure on the retaining structure. The displacement of the retaining structure at the installation support position when the foundation pit is excavated to the corresponding depth.

[0084] Convert the elastic foundation beam model into matrix form: , and then whether it can be passed in S2 and calculate ;

[0085] The stiffness matrix Expressed as:

[0086]

[0087] in, , 、 、 are intermediate variables. is the calculation unit length of the retaining structure; the soil exerts lateral force on the retaining structure through n soil springs. represents the elastic modulus of the i-th soil spring, , is the total number of soil springs.

[0088] Step S2: Determine the initial earth pressure parameters , combined with the stiffness matrix , calculate the lateral deformation of the enclosure structure .

[0089] Step S3: According to the lateral deformation of the enclosure structure , considering the confined space of foundation soil, update the soil pressure parameters ; Based on the updated earth pressure parameters , combined with the stiffness matrix , calculate the lateral deformation of the enclosure structure again .

[0090] Specifically, the earth pressure parameter The update method is:

[0091] For the case where the soil exerts pressure on the surrounding structure, the earth pressure parameter Represents the active earth pressure parameter ; For the case where the retaining structure exerts pressure on the soil, the soil pressure parameter Represents the passive earth pressure parameter .

[0092] First, according to the lateral deformation of the enclosure structure Calculate the active earth pressure parameters to be corrected and the passive earth pressure parameters to be corrected :

[0093]

[0094]

[0095] in, is the active earth pressure parameter to be corrected The i-th element in , is the passive earth pressure parameter to be corrected The i-th element in , Lateral deformation of the retaining structure The i-th element in ; is the elastic modulus of the soil spring in the active zone, is the elastic modulus of the passive zone soil spring, is the static earth pressure at the soil calculation depth, is the limit value of active earth pressure, is the limit value of passive earth pressure.

[0096] Considering the confined space of foundation soil and the arching effect of soil behind the wall, the active earth pressure correction coefficient β a and the passive earth pressure correction factor β p Active earth pressure parameters to be corrected and the passive earth pressure parameters to be corrected Correction is performed to obtain the corrected active earth pressure parameters and passive earth pressure parameters , that is, the updated earth pressure parameters are obtained ;

[0097]

[0098]

[0099]

[0100]

[0101] Among them, B is the excavation width of the foundation pit, H is the excavation depth of the foundation pit, is the internal friction angle of soil, c is the cohesion of soil, δ is the friction angle of soil-structure interface, is the soil weight, and μ is the soil-structure interface coefficient.

[0102] Step S4: Determine whether the lateral deformation error Δu of the enclosure structure calculated twice before and after meets the accuracy requirement. If yes, go to step S5. Otherwise, repeat step S3 and iteratively calculate the lateral deformation of the enclosure structure. The lateral deformation error Δu of the retaining structure calculated twice before and after meets the accuracy requirements.

[0103] Specifically, the accuracy requirement for the lateral deformation error Δu of the enclosure structure calculated twice before and after is as follows:

[0104]

[0105] in, 、 Respectively sequence The lateral deformation of the enclosure structure calculated for the second time is Indicates the calculation of the Euclidean distance between matrices, The precision threshold is set.

[0106] Step S5: Determine the lateral deformation of the enclosure structure Then, the soil shear stress τ is calculated, and then the shear strain is calculated. and soil shear stiffness.

[0107] First, calculate the soil transverse shear stress and soil longitudinal shear stress according to the following formula:

[0108]

[0109]

[0110] in, is the transverse shear stress, is the longitudinal shear stress, F is the transverse concentrated force, Q is the longitudinal concentrated force, is the coordinate of the lateral concentrated force F, is the coordinate of the longitudinal concentrated force Q; x and z are the abscissa and ordinate of the resultant force of F and Q; , ; is the Poisson's ratio of soil.

[0111] The soil shear stress τ is obtained by synthesizing the transverse shear stress and the longitudinal shear stress.

[0112] Then, the shear strain is calculated as follows :

[0113]

[0114] in, is the initial shear stiffness, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness.

[0115] In the small strain stage, the soil shear stiffness decays with the shear strain. After the shear strain is calculated, the soil shear stiffness is calculated according to the following formula: :

[0116]

[0117] in, is the soil shear stiffness.

[0118] Step S6: Calculate the shear stiffness attenuation characteristics of the soil in the coupled small strain stage and the soil spring elastic modulus k of the soil hardening, and update the stiffness matrix .

[0119] Specifically, the soil spring elastic modulus k of the coupled soil shear stiffness attenuation characteristic and soil hardening in the small strain stage is calculated according to the following formula:

[0120]

[0121] in, is the strain condition correction coefficient, is the elastic modulus of soil, is the Poisson's ratio of soil, B is the excavation width of foundation pit, and EI is the flexural stiffness of the retaining structure.

[0122] In the large strain stage, When considering the soil stiffness hardening characteristics, the soil elastic modulus The calculation formula is as follows:

[0123]

[0124] in, is the elastic modulus of soil under reference effective confining pressure, is the effective cohesion of soil, is the effective internal friction angle of soil, is the lateral effective stress of the soil, is the reference effective confining pressure, m represents the correlation between stiffness and stress level; is the cutoff value, which is calculated as follows:

[0125]

[0126] in, is the initial shear stiffness, is the unloading-reloading shear stiffness, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness.

[0127] In the small strain stage, When the soil elastic modulus The calculation formula is as follows:

[0128]

[0129] in, is the soil rebound Poisson’s ratio, is the soil shear stiffness.

[0130] After calculating the soil spring elastic modulus k, the stiffness matrix can be updated .

[0131] Step S7: Record the displacement u of the retaining structure at the installation support position when excavation reaches the current depth T Then, return to step S1 and enter the next excavation stage calculation until the designed excavation depth is reached.

[0132] Step S8: After calculating the designed excavation depth, output the soil pressure parameters , lateral deformation of the retaining structure and bending moment M, in order to evaluate the stress and deformation of the foundation pit retaining structure.

[0133] The calculation formula of the bending moment M of the enclosure structure is as follows:

[0134]

[0135] Where EI is the bending stiffness of the enclosure structure, u is the displacement of the enclosure structure, z e Calculate the depth for the enclosure.

[0136] The implementation process of this method is further described below with reference to a specific embodiment.

[0137] The research object is a confined space foundation pit retaining structure of a subway. Figure 2 SPT test is carried out inside and outside the confined space foundation pit to obtain SPT test value, as shown in Figure 3 When excavating to a certain depth, the first steel support, the second steel support, and the third steel support are arranged in sequence, as shown in the figure. Figure 4 The bending moment of the retaining structure to the designed excavation depth is calculated as follows: Figure 5 Record the monitoring value and calculated value of the lateral displacement of the retaining structure at each monitoring point at each excavation depth in sequence, as shown in Figure 6 As shown, Δh is the buried depth of the monitoring or calculation location, and L is the buried depth of the enclosure structure. The specific implementation steps are as follows:

[0138] Step 1: Before excavation, based on the SPT in-situ test and the above calculation formula, the undisturbed soil parameters and foundation pit design parameters before excavation are obtained, as shown in Table 1;

[0139] Step 2: During the excavation process, real-time monitoring of soil pressure and lateral displacement of the foundation pit retaining structure is performed;

[0140] Step 3: After the excavation of the foundation pit, calculate the soil shear stiffness attenuation characteristics and soil hardening parameters in the coupled small strain stage. Pick , compression modulus of medium-coarse sand Take the empirical value of 20 kPa and Substitute into the above formula to calculate the elastic modulus , update the model calculation parameters of the disturbance after excavation;

[0141] Step 4: Arrange all the model calculation parameters to derive the earth pressure, lateral displacement distribution and bending moment of the retaining structure, and compare the lateral displacement of the retaining structure with the on-site monitoring data to verify the applicability of the force and deformation calculation method of the deep foundation pit retaining structure coupled with the nonlinearity of soil stiffness. The comparison results are as follows: Figure 6 According to the comparison results, the present invention can correctly predict the soil pressure of deep foundation pit and the lateral displacement of the retaining structure.

[0142] Table 1 Parameters of undisturbed soil before excavation and design parameters of foundation pit

[0143]

[0144] This embodiment also provides a system for predicting the stress and deformation of a confined space foundation pit retaining structure, which includes a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the above-mentioned method can be implemented.

[0145] This embodiment further provides a computer-readable storage medium having computer program instructions stored thereon, which implements the above method when the computer program instructions are executed by a processor.

[0146] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0147] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0148] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0149] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0150] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for predicting stress and deformation of a confined space foundation pit retaining structure, characterized in that: The following steps are involved: Step S1: Based on the elastic foundation beam model, input the soil parameters and foundation pit design parameters interpreted based on the SPT in-situ test to generate the stiffness matrix ; Step S2: Determine the initial earth pressure parameters , combined with the stiffness matrix , calculate the lateral deformation of the enclosure structure ; Step S3: According to the lateral deformation of the enclosure structure , considering the confined space of foundation soil, update the soil pressure parameters ; Based on the updated earth pressure parameters , combined with the stiffness matrix , calculate the lateral deformation of the enclosure structure again ; Step S4: Determine whether the lateral deformation error Δu of the enclosure structure calculated twice before and after meets the accuracy requirement. If yes, go to step S5. Otherwise, repeat step S3 and iteratively calculate the lateral deformation of the enclosure structure. Until the lateral deformation error Δu of the enclosure structure calculated twice before and after meets the accuracy requirements; Step S5: Determine the lateral deformation of the enclosure structure Then, the soil shear stress τ is calculated, and then the shear strain is calculated. and soil shear stiffness; Step S6: Calculate the shear stiffness attenuation characteristics of the soil in the coupled small strain stage and the soil spring elastic modulus k of the soil hardening, and update the stiffness matrix ; Step S7: Record the displacement u of the retaining structure at the installation support position when excavation reaches the current depth T ; Then return to step S1 and enter the next excavation stage calculation until the designed excavation depth; Step S8: After calculating the designed excavation depth, output the soil pressure parameters , lateral deformation of the retaining structure and bending moment M, to evaluate the stress and deformation of the foundation pit retaining structure; In step S1, the soil parameters interpreted based on the SPT in-situ test are: in, is the effective cohesion of soil, is the initial overlying effective stress of the soil layer, is the effective internal friction angle of soil, is the standard penetration number, is the corrected standard penetration number, is standard atmospheric pressure, is the elastic modulus of soil under reference effective confining pressure, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness, is the initial shear stiffness, is the soil cohesion, is the effective major principal stress, is the static earth pressure coefficient, is the soil density, is the Poisson's ratio of soil, is the soil overconsolidation ratio.

2. The method for predicting stress and deformation of a confined space foundation pit retaining structure according to claim 1, characterized in that: In step S1, the elastic foundation beam model is: Where EI is the bending stiffness of the enclosure structure, u is the displacement of the enclosure structure, z e Calculate the depth for the enclosure structure, is the elastic modulus of soil spring, is the horizontal support stiffness of the foundation pit, is the difference between the active earth pressure and the passive earth pressure on the retaining structure. The displacement of the retaining structure at the installation support position when the foundation pit is excavated to the corresponding depth; Convert the elastic foundation beam model into matrix form: , and thus can be achieved through and calculate ; The stiffness matrix Expressed as: in, , 、 、 are intermediate variables. Calculate unit lengths for enclosure structures; represents the elastic modulus of the i-th soil spring, , is the total number of soil springs.

3. The method for predicting stress and deformation of a confined space foundation pit retaining structure according to claim 1, characterized in that: In step S3, the soil pressure parameter The update method is: For the case where the soil exerts pressure on the surrounding structure, the earth pressure parameter Represents the active earth pressure parameter ; For the case where the retaining structure exerts pressure on the soil, the soil pressure parameter Represents the passive earth pressure parameter ; According to the lateral deformation of the enclosure structure Calculate the active earth pressure parameters to be corrected and the passive earth pressure parameters to be corrected : in, is the active earth pressure parameter to be corrected The i-th element in , is the passive earth pressure parameter to be corrected The i-th element in , Lateral deformation of the retaining structure The i-th element in ; is the elastic modulus of the soil spring in the active zone, is the elastic modulus of the soil spring in the passive zone, is the static earth pressure at the soil calculation depth, is the limit value of active earth pressure, is the limit value of passive earth pressure; Considering the confined space of foundation soil and the arching effect of soil behind the wall, the active earth pressure correction coefficient β a and the passive earth pressure correction factor β p Active earth pressure parameters to be corrected and the passive earth pressure parameters to be corrected Correction is performed to obtain the corrected active earth pressure parameters and passive earth pressure parameters , that is, the updated earth pressure parameters are obtained ; Among them, B is the excavation width of the foundation pit, H is the excavation depth of the foundation pit, is the internal friction angle of soil, c is the cohesion of soil, δ is the friction angle of soil-structure interface, is the soil weight, and μ is the soil-structure interface coefficient.

4. The method for predicting stress and deformation of a confined space foundation pit retaining structure according to claim 1, characterized in that: In step S4, the accuracy requirement of the lateral deformation error Δu of the enclosure structure calculated twice before and after must be: in, 、 Respectively sequence The lateral deformation of the enclosure structure calculated for the second time is Indicates the calculation of the Euclidean distance between matrices, is the set accuracy threshold.

5. The method for predicting stress and deformation of a confined space foundation pit retaining structure according to claim 1, characterized in that: In step S5, the soil transverse shear stress and soil longitudinal shear stress are calculated according to the following formula: in, is the transverse shear stress, is the longitudinal shear stress, F is the transverse concentrated force, Q is the longitudinal concentrated force, is the coordinate of the lateral concentrated force F, is the coordinate of the longitudinal concentrated force Q; x and z are the abscissa and ordinate of the resultant force of F and Q; , ; is the Poisson's ratio of soil; The soil shear stress τ is obtained by synthesizing the transverse shear stress and the longitudinal shear stress; Then the shear strain is calculated as follows : in, is the initial shear stiffness, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness; In the small strain stage, the soil shear stiffness decays with the shear strain. After the shear strain is calculated, the soil shear stiffness is calculated according to the following formula: : in, is the soil shear stiffness.

6. The method for predicting stress and deformation of a confined space foundation pit retaining structure according to claim 1, characterized in that: In step S6, the soil shear stiffness attenuation characteristic and the soil spring elastic modulus k of soil hardening in the coupled small strain stage are calculated according to the following formula: in, is the strain condition correction coefficient, is the elastic modulus of soil, is the Poisson's ratio of soil, B is the excavation width of foundation pit, and EI is the flexural stiffness of the retaining structure; In the large strain stage, When considering the soil stiffness hardening characteristics, the soil elastic modulus The calculation formula is as follows: in, is the elastic modulus of soil under reference effective confining pressure, is the effective cohesion of soil, is the effective internal friction angle of soil, is the lateral effective stress of the soil, is the reference effective confining pressure, m represents the correlation between stiffness and stress level; is the cutoff value, which is calculated as follows: in, is the initial shear stiffness, is the unloading-reloading shear stiffness, is the shear strain characteristic value corresponding to the shear stiffness decaying to 70% of the initial shear stiffness; In the small strain stage, When the soil elastic modulus The calculation formula is as follows: in, is the soil rebound Poisson’s ratio, is the soil shear stiffness.

7. The method for predicting stress and deformation of a confined space foundation pit retaining structure according to claim 1, characterized in that: In step S8, the calculation formula of the bending moment M of the enclosure structure is as follows: Where EI is the bending stiffness of the enclosure structure, u is the displacement of the enclosure structure, z e Calculate the depth for the enclosure.

8. A stress and deformation prediction system for confined space foundation pit retaining structure, characterized in that: The method comprises a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the method according to any one of claims 1 to 7 can be implemented.

9. A computer-readable storage medium having computer program instructions stored thereon, characterized in that: When the computer program instructions are executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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