Method for improving anti-seismic liquefaction performance of foundation based on long and large underground structure

Abstract

The invention provides a foundation anti-seismic liquefaction performance improving method based on a long and large underground structure, and belongs to civil engineering and earthquake engineering technologies, and the foundation anti-seismic liquefaction performance improving method comprises the steps that basic data of the long and large underground structure are obtained; determining a liquefaction sensitive area; calculating the liquefaction grade of the liquefaction sensitive area, and carrying out regional division on the underground structure; different reinforcement treatment measures are made according to the divided areas, then foundation anti-seismic liquefaction evaluation is conducted on the foundation subjected to reinforcement treatment, and the reinforcement treatment measures are optimized according to the evaluation result; and the foundation subjected to reinforcement treatment is monitored in real time, the liquefaction performance of the foundation is evaluated in real time, and an evaluation result is sent to the reinforcement scheme making module to make a reinforcement scheme again. According to the foundation anti-seismic liquefaction performance improving method based on the long and large underground structure, through comprehensive reinforcement measures and monitoring technologies, the anti-seismic performance of the foundation is effectively improved, the liquefaction risk of the foundation under the earthquake action is reduced, and the safety and stability of the underground structure are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical fields of civil engineering and earthquake engineering, and in particular to a method for improving the anti-seismic liquefaction performance of a foundation based on a long and large underground structure. Background Art

[0002] With the development of urbanization, large underground structures such as subways and underground shopping malls are becoming more and more important. However, the foundations of these large underground structures are easily damaged by earthquakes, which leads to a decrease in the overall stability of the structure and even causes serious accidents.

[0003] At present, most methods for analyzing the seismic performance of underground structures are based on deterministic methods, which have limitations when dealing with complex earthquake effects. The seismic vulnerability analysis method provides a method for analyzing the seismic performance of underground structures that fully considers uncertain factors. It can predict the conditional probability of various damage levels of underground structures under earthquakes of different intensities, and provide a reference for the seismic design of underground structures, earthquake risk decision-making, and rapid post-earthquake assessment. However, the application of this method in improving the seismic liquefaction performance of foundations of large and long underground structures still needs further research and improvement. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the seismic liquefaction performance of the foundation based on a long and large underground structure. Through comprehensive reinforcement measures and monitoring technology, the seismic resistance of the foundation is effectively improved, the liquefaction risk of the foundation under the action of an earthquake is reduced, and the safety and stability of the underground structure are ensured.

[0005] To achieve the above object, the present invention provides a method for improving the seismic liquefaction performance of a foundation based on a long underground structure, comprising the following steps:

[0006] S1, data acquisition module performs geological survey on long underground structures to obtain basic data;

[0007] S2, the liquefaction analysis module analyzes the liquefaction performance of the foundation and determines the liquefaction sensitive area based on the acquired basic data;

[0008] S3, the regional division module calculates the liquefaction level of the liquefaction sensitive area, and divides the underground structure into regions according to the liquefaction level, namely, slightly liquefied area, moderately liquefied area, severely liquefied area and non-liquefied area;

[0009] S4, the reinforcement scheme formulation module formulates different reinforcement measures according to the divided areas, then conducts seismic liquefaction assessment on the reinforced foundation, and optimizes the reinforcement measures according to the assessment results;

[0010] S5. The intelligent monitoring and evaluation module monitors the reinforced foundation in real time through intelligent monitoring equipment, and evaluates the liquefaction performance of the foundation in real time based on the monitoring information, and then sends the evaluation results to the reinforcement plan formulation module to formulate a reinforcement plan again.

[0011] Preferably, in step S1, the basic data include soil layer properties, groundwater level depth, overlying non-liquefied layer thickness, foundation burial depth, liquefaction characteristic depth, underground temperature and underground humidity;

[0012] Soil layer properties include particle grading, relative density and clay content.

[0013] Preferably, in step S2, the liquefaction performance of the foundation is analyzed, and the specific operations are:

[0014] S21. First, make a preliminary judgment on whether the foundation soil is liquefied. The judgment criteria are as follows:

[0015] d u +d w >1.5d o +2d b -4.5

[0016] Among them, d u is the thickness of the overlying non-liquefied layer, minus the thickness of the silt and silty soil layer; d w is the depth of groundwater level, using the annual average maximum water level during the design reference period; d o The foundation burial depth is 2.0m if it does not exceed 2.0m; d b is the characteristic depth of liquefaction (m), which is selected according to relevant specifications or test data;

[0017] S22: When the initial judgment is liquefaction, further judgment is made. The judgment criteria are as follows:

[0018] N 63.5 <N cr

[0019] Among them, N 63.5 N is the number of hammer blows in the actual field test of soil layer; cr is the critical value of the penetration hammer number for liquefaction judgment, which is determined according to factors such as the nature of the soil layer, burial depth, groundwater level, and earthquake intensity. 63.5 Less than the critical value N cr When the soil is liquefied, it should be judged as liquefied soil; otherwise, it is non-liquefied soil.

[0020] Preferably, in step S22, N cr The method of determining is as follows:

[0021] In Python, we use the RandomForestRegressor class in the Scikit-learn library to construct N cr A random forest regression model with soil properties, groundwater level depth, temperature, humidity, and thickness of the overlying non-liquefiable layer was constructed, and the performance of the constructed model was evaluated by mean square error and mean absolute error.

[0022] Preferably, when constructing the random forest regression model, the following hyperparameters are set: the number of decision trees, the feature selection method, the growth depth of the decision tree (max_depth), the minimum number of samples for node splitting, and the minimum number of samples for leaf nodes.

[0023] Preferably, in step S3, the liquefaction level is determined according to the liquefaction index, and the calculation formula of the liquefaction index is as follows:

[0024]

[0025] Among them, I LE is the liquefaction index; d i is the soil layer thickness; ω i is the weight factor; N is the number of soil layers; i is the initial value of the soil layer.

[0026] Preferably, in step S4, the reinforcement plan formulation module formulates different reinforcement measures according to different performance improvement areas, and the specific operations are as follows:

[0027] For non-liquefied areas, no reinforcement is required;

[0028] For areas with slight liquefaction, one or more of the following methods, vibratory compaction, vibratory rolling or vibratory agitation, are used to treat the foundation depth to improve the density and strength of the soil, thereby enhancing the foundation's ability to resist liquefaction;

[0029] For moderate liquefaction areas, shallow foundation treatment is used to use the covering soil layer above the liquefiable sand layer as the foundation support layer;

[0030] For severely liquefied areas, a comprehensive method of vibration reinforcement, grouting reinforcement, pile foundation reinforcement, construction of a composite drainage system and addition of foundation treatment agents is adopted. After reinforcement, the structure of the severely liquefied areas is optimized;

[0031] Vibration reinforcement: Use one or more of the following methods: vibration compaction, vibration rolling or vibration agitation to deeply treat the foundation to increase the density and strength of the soil and reduce the risk of foundation liquefaction during an earthquake.

[0032] Grouting reinforcement: Set grouting holes under the foundation and inject high-strength cement slurry, chemical slurry or other suitable grouting materials to fill the soil pores and enhance the bearing capacity and stability of the foundation.

[0033] Pile foundation reinforcement: Reinforced concrete piles or other types of pile foundations are set in the foundation to transfer the upper load to the deep stable strata and improve the overall seismic resistance of the foundation.

[0034] Construct a composite waterproof system: Set up permanent vertical and horizontal pore pressure dissipation drainage bodies in the foundation, such as plastic drainage boards, permeable pipes, etc., to form a composite drainage system. Ensure effective connection between drainage bodies and with the surface drainage system to form a smooth drainage channel and reduce excess pore water pressure in the foundation.

[0035] Addition of foundation treatment agent: Evenly add appropriate amount of cement, lime, polyacrylamide or other foundation treatment agents to the foundation to improve the physical and mechanical properties of the soil through physical and chemical reactions and enhance the foundation's ability to resist liquefaction.

[0036] Preferably, in step S4, the method for evaluating the seismic liquefaction resistance of the reinforced foundation is a numerical simulation method.

[0037] Preferably, the intelligent monitoring equipment includes a soil sampler, a power drill, a foundation sonic tester, a seismic wave velocity tester and a pore water pressure gauge.

[0038] Preferably, in step S5, when the reinforcement plan formulation module saves the evaluation results sent by the intelligent monitoring module, the reinforcement plan formulation module directly gives a corresponding reinforcement plan; when the reinforcement plan formulation module does not save the evaluation results sent by the intelligent monitoring module, the reinforcement plan formulation module sends the monitoring information and the evaluation results to the expert module, the expert module sends the corresponding monitoring information to the corresponding engineer terminal, the engineer formulates a new reinforcement plan based on the monitoring information, and returns the new reinforcement plan to the reinforcement plan formulation module.

[0039] Therefore, the present invention adopts the above-mentioned method for improving the anti-seismic liquefaction performance of foundation based on a long underground structure, and the beneficial technical effects are as follows:

[0040] (1) The method proposed in the present invention significantly improves the bearing capacity and stability of the foundation of a large underground structure and reduces the risk of foundation liquefaction during an earthquake;

[0041] (2) This method has the advantages of simple construction, significant effect, and controllable cost. It is suitable for foundation reinforcement projects of large and large underground structures of various types and sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of a method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to the present invention;

[0043] Figure 2It is a schematic diagram of a system for improving the seismic liquefaction performance of foundations based on long and large underground structures. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0045] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0046] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0047] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0048] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] Embodiment 1

[0050] like Figure 2As shown, the present invention provides a system for improving the seismic liquefaction performance of foundations based on long and large underground structures, including a data acquisition module, a liquefaction analysis module, a regional division module, a reinforcement plan formulation module and an intelligent monitoring and evaluation module.

[0051] like Figure 1 As shown, a method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to the present invention specifically comprises the following steps:

[0052] S1, data acquisition module performs geological survey on long underground structures to obtain basic data;

[0053] Basic data include soil properties, groundwater level depth, thickness of overlying non-liquefied layer, foundation burial depth, liquefaction characteristic depth, underground temperature and underground humidity;

[0054] The consideration of basic data keeps pace with the times. With the development of relevant technologies, in addition to the above basic data, more factors such as external loads and composite indicators can also be considered to make subsequent performance tests more accurate.

[0055] The properties of the soil layer include the particle grading, relative density and clay content of the soil layer.

[0056] S2, liquefaction analysis module analyzes the liquefaction performance of the foundation and determines the liquefaction sensitive area based on the acquired basic data;

[0057] Analyze the liquefaction performance of the foundation. The specific operations are as follows:

[0058] S21. First, make a preliminary judgment on whether the foundation soil is liquefied. The judgment criteria are as follows:

[0059] d u +d w >1.5d o +2d b -4.5

[0060] Among them, d u is the thickness of the overlying non-liquefied layer, minus the thickness of the silt and silty soil layer; d w is the depth of groundwater level, using the annual average maximum water level during the design reference period; d o The foundation burial depth is 2.0m if it does not exceed 2.0m; d b is the characteristic depth of liquefaction (m), which is selected according to relevant specifications or test data;

[0061] S22: When the initial judgment is liquefaction, further judgment is made. The judgment criteria are as follows:

[0062] N 63.5 <N cr

[0063] Among them, N 63.5 N is the number of hammer blows in the actual field test of soil layer; cr is the critical value of the penetration hammer number for liquefaction judgment, which is determined according to factors such as the nature of the soil layer, burial depth, groundwater level, and earthquake intensity. 63.5 When it is less than the critical value Ncr, it should be judged as liquefied soil; otherwise, it is non-liquefied soil.

[0064] In this embodiment, N cr The method of determining is as follows:

[0065] In Python, we use the RandomForestRegressor class in the Scikit-learn library to construct N cr A random forest regression model with soil properties, groundwater level depth, temperature, humidity, and thickness of the overlying non-liquefiable layer was constructed, and the performance of the constructed model was evaluated by mean square error and mean absolute error.

[0066] When building a random forest regression model, the following hyperparameters are set: the number of decision trees, the method of feature selection, the growth depth of the decision tree, the minimum number of samples for node splitting, and the minimum number of samples for leaf nodes. The specific settings are conventional techniques and will not be elaborated here.

[0067] S3, the regional division module calculates the liquefaction level of the liquefaction sensitive area, and divides the underground structure into regions according to the liquefaction level, namely, slightly liquefied area, moderately liquefied area, severely liquefied area and non-liquefied area;

[0068] The liquefaction level is determined based on the liquefaction index, which is calculated using the following formula:

[0069]

[0070] Among them, I LE is the liquefaction index; d i is the soil layer thickness; ω i is the weight factor; N is the number of soil layers; i is the initial value of the soil layer.

[0071] S4, the reinforcement scheme formulation module formulates different reinforcement measures according to the divided areas, then conducts seismic liquefaction assessment on the reinforced foundation, and optimizes the reinforcement measures according to the assessment results;

[0072] The reinforcement plan formulation module formulates different reinforcement measures according to different performance improvement areas. The specific operations are as follows:

[0073] For non-liquefied areas, no reinforcement is required;

[0074] For areas with slight liquefaction, one or more of the following methods, vibratory compaction, vibratory rolling or vibratory agitation, are used to treat the foundation depth to improve the density and strength of the soil, thereby enhancing the foundation's ability to resist liquefaction;

[0075] For moderate liquefaction areas, shallow foundation treatment is used to use the covering soil layer above the liquefiable sand layer as the foundation support layer;

[0076] For severely liquefied areas, a comprehensive method of vibration reinforcement, grouting reinforcement, pile foundation reinforcement, construction of a composite drainage system and addition of foundation treatment agents is adopted. After reinforcement, the structure of the severely liquefied areas is optimized;

[0077] Vibration reinforcement: Use one or more of the following methods: vibration compaction, vibration rolling or vibration agitation to deeply treat the foundation to increase the density and strength of the soil and reduce the risk of foundation liquefaction during an earthquake.

[0078] Specifically, they include:

[0079] Equipment selection: Choose the appropriate vibration reinforcement equipment according to the type and depth of foundation soil;

[0080] Parameter setting: according to the physical and mechanical properties of the foundation soil and the target density, set the vibration frequency, amplitude, action time and other parameters. These parameters are determined through experiments or empirical data;

[0081] Construction operation: Place the vibration reinforcement equipment on the foundation surface or drill a hole to a predetermined depth, turn on the vibration source, and perform vibration compaction or vibration rolling on the foundation. During the construction process, the vibration speed, walking route and number of times must be controlled to ensure that the foundation is evenly vibrated.

[0082] Grouting reinforcement: Set grouting holes under the foundation and inject high-strength cement slurry, chemical slurry or other suitable grouting materials to fill the soil pores and enhance the bearing capacity and stability of the foundation.

[0083] Specifically, they include:

[0084] Grouting hole arrangement: According to the actual situation of the foundation and design requirements, determine the location, diameter, depth and spacing of the grouting holes. The grouting holes should be evenly arranged and penetrate the potential liquefied soil layer.

[0085] Slurry preparation: Select appropriate grouting materials (such as cement slurry, chemical slurry, etc.) and prepare them according to the designed proportion. During the preparation process, attention should be paid to the mixing uniformity and fluidity of the materials.

[0086] Grouting construction: Use grouting equipment to inject the prepared slurry into the grouting hole. During the grouting process, the grouting pressure and grouting speed must be controlled to ensure that the slurry can fully fill the soil pores and react chemically with the soil. After the grouting is completed, timely sealing treatment is carried out to prevent the slurry from overflowing.

[0087] Pile foundation reinforcement: Reinforced concrete piles or other types of pile foundations are set in the foundation to transfer the upper load to the deep stable strata and improve the overall seismic resistance of the foundation.

[0088] Specifically, they include:

[0089] Pile foundation design: According to the bearing capacity and stability requirements of the foundation, design the appropriate pile foundation type (such as reinforced concrete piles, steel pipe piles, etc.), diameter, length and layout. The connection method and force transmission path between the pile foundation and the superstructure must be considered during the design.

[0090] Construction preparation: clean up the construction site and ensure that there are no obstacles in the pile foundation construction area. Prepare necessary construction equipment and materials, such as drilling rigs, steel cages, concrete mixing plants, etc.

[0091] Pile foundation construction: Carry out pile foundation construction according to design requirements. For reinforced concrete piles, it is necessary to first drill holes to the predetermined depth, then lower the steel cage and pour concrete; for steel pipe piles, they can be directly driven or vibrated into the predetermined position. During the construction process, the verticality of the pile body and the elevation of the pile top must be controlled to ensure the construction quality of the pile foundation.

[0092] Construct a composite waterproof system: Set up permanent vertical and horizontal pore pressure dissipation drainage bodies in the foundation, such as plastic drainage boards, permeable pipes, etc., to form a composite drainage system. Ensure effective connection between drainage bodies and with the surface drainage system to form a smooth drainage channel and reduce excess pore water pressure in the foundation.

[0093] Addition of foundation treatment agent: Evenly add appropriate amount of cement, lime, polyacrylamide or other foundation treatment agents to the foundation to improve the physical and mechanical properties of the soil through physical and chemical reactions and enhance the foundation's ability to resist liquefaction.

[0094] Specifically, they include:

[0095] Treatment agent selection: According to the nature of the foundation soil and the improvement objectives, select the appropriate foundation treatment agent (such as cement, lime, polyacrylamide, etc.). The selection of the treatment agent should take into account its chemical stability, reaction speed and impact on the environment.

[0096] Adding method: After the treatment agent is mixed evenly with an appropriate amount of water or other solvent, it is added to the foundation soil by spraying, stirring or grouting. During the adding process, the amount and distribution uniformity of the treatment agent must be controlled to ensure that the foundation soil can fully absorb and react chemically.

[0097] Subsequent treatment: After the treatment agent is added, a certain curing time is required to allow the treatment agent to fully react with the soil and solidify. During the curing period, the moisture and temperature of the foundation soil must be kept stable to promote the reaction process.

[0098] After reinforcement, the structural optimization is as follows:

[0099] Basic design;

[0100] Foundation selection: Select the appropriate foundation form (such as expanded foundation, pile foundation, etc.) based on the actual situation after foundation improvement and the load requirements of the superstructure.

[0101] Size calculation: According to the bearing capacity of the foundation and the load distribution of the superstructure, calculate the bottom surface size, burial depth, reinforcement and other parameters of the foundation.

[0102] Structural design: Design the detailed structure of the foundation, such as the thickness of the foundation slab, reinforcement method, waterproofing measures, etc.

[0103] Structural seismic design;

[0104] Earthquake fortification: Determine the earthquake fortification objectives and performance requirements of the structure based on the earthquake intensity and earthquake fortification requirements of the project location.

[0105] Earthquake-resistant measures: Take necessary earthquake-resistant measures in structural design, such as adding structural walls, strengthening columns, setting shock-absorbing bearings and dampers, etc.

[0106] Node connection design: Optimize the structural node connection design to ensure that the nodes can maintain sufficient bearing capacity and deformation capacity under earthquake action.

[0107] The method for evaluating the seismic liquefaction of the reinforced foundation is the numerical simulation method, which can be performed by finite element numerical simulation and other methods. This is the existing technology and will not be elaborated in detail.

[0108] Intelligent monitoring equipment includes soil samplers, power drills, foundation acoustic wave testers, seismic wave velocity testers and pore water pressure meters.

[0109] S5. The intelligent monitoring and evaluation module monitors the reinforced foundation in real time through intelligent monitoring equipment, and evaluates the liquefaction performance of the foundation in real time based on the monitoring information, and then sends the evaluation results to the reinforcement plan formulation module to formulate a reinforcement plan again.

[0110] When the reinforcement plan formulation module saves the evaluation results sent by the intelligent monitoring module, the reinforcement plan formulation module directly gives the corresponding reinforcement plan; when the reinforcement plan formulation module does not save the evaluation results sent by the intelligent monitoring module, the reinforcement plan formulation module sends the monitoring information and evaluation results to the expert module, and the expert module sends the corresponding monitoring information to the corresponding engineer terminal. The engineer formulates a new reinforcement plan based on the monitoring information and returns the new reinforcement plan to the reinforcement plan formulation module.

[0111] The present invention also provides a system for improving the seismic liquefaction performance of foundations based on long and large underground structures, including a data acquisition module, a liquefaction analysis module, a region division module, a reinforcement scheme formulation module, an intelligent monitoring and evaluation module, and an expert module;

[0112] Among them, the embodiments of the system part correspond to the embodiments of the method part, so for the embodiments of the system part, please refer to the description of the embodiments of the method part, and they will not be repeated here.

[0113] Therefore, the present invention adopts the above-mentioned method for improving the seismic liquefaction performance of the foundation based on a long and large underground structure, and through comprehensive reinforcement measures and monitoring technology, effectively improves the seismic resistance of the foundation, reduces the liquefaction risk of the foundation under the action of an earthquake, and ensures the safety and stability of the underground structure.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for improving the seismic liquefaction performance of foundations based on long and large underground structures, characterized in that: The following steps are involved: S1, data acquisition module performs geological survey on long underground structures to obtain basic data; S2, liquefaction analysis module analyzes the liquefaction performance of the foundation and determines the liquefaction sensitive area based on the acquired basic data; S3, the regional division module calculates the liquefaction level of the liquefaction sensitive area, and divides the underground structure into regions according to the liquefaction level, namely, slightly liquefied area, moderately liquefied area, severely liquefied area and non-liquefied area; S4, the reinforcement scheme formulation module formulates different reinforcement measures according to the divided areas, then conducts seismic liquefaction assessment on the reinforced foundation, and optimizes the reinforcement measures according to the assessment results; S5. The intelligent monitoring and evaluation module monitors the reinforced foundation in real time through intelligent monitoring equipment, and evaluates the liquefaction performance of the foundation in real time based on the monitoring information, and then sends the evaluation results to the reinforcement plan formulation module to formulate a reinforcement plan again.

2. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 1, characterized in that: In step S1, the basic data includes soil layer properties, groundwater level depth, thickness of overlying non-liquefied layer, foundation burial depth, liquefaction characteristic depth, underground temperature and underground humidity; Soil layer properties include particle grading, relative density and clay content.

3. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 2, characterized in that: In step S2, the liquefaction performance of the foundation is analyzed, and the specific operations are as follows: S21. First, make a preliminary judgment on whether the foundation soil is liquefied. The judgment criteria are as follows: <h2 style=";text-align:left;direction:ltr">d<h2 style=";text-align:left;direction:ltr"> u <h2 style=";text-align:left;direction:ltr"> +d<h2 style=";text-align:left;direction:ltr"> w <h2 style=";text-align:left;direction:ltr"> >1.5d<h2 style=";text-align:left;direction:ltr"> o <h2 style=";text-align:left;direction:ltr"> +2d<h2 style=";text-align:left;direction:ltr"> b <h2 style=";text-align:left;direction:ltr"> -4.5 Among them, d u is the thickness of the overlying non-liquefied layer, minus the thickness of the silt and silty soil layer; d w is the depth of groundwater level; d o The foundation burial depth; d b is the liquefaction feature depth; S22: When the initial judgment is liquefaction, further judgment is made. The judgment criteria are as follows: N 63.5 <N cr Among them, N 63.5 N is the number of hammer blows in the actual field test of soil layer; cr It is the critical value of the number of penetration hammer blows for liquefaction judgment.

4. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 3, characterized in that: In step S22, N cr The method of determining is as follows: In Python, we use the RandomForestRegressor class in the Scikit-learn library to construct N cr A random forest regression model with soil properties, groundwater level depth, temperature, humidity, and thickness of the overlying non-liquefiable layer was constructed, and the performance of the constructed model was evaluated by mean square error and mean absolute error.

5. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 4, characterized in that: When building a random forest regression model, the following hyperparameters are set: the number of decision trees, the method of feature selection, the growth depth of the decision tree, the minimum number of samples for node splitting, and the minimum number of samples for leaf nodes.

6. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 5, characterized in that: In step S3, the liquefaction level is determined according to the liquefaction index, and the calculation formula of the liquefaction index is as follows: Among them, I LE is the liquefaction index; d i is the soil layer thickness; ω i is the weight factor; N is the number of soil layers; i is the initial value of the soil layer.

7. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 6, characterized in that: In step S4, the reinforcement plan formulation module formulates different reinforcement measures according to different performance improvement areas. The specific operations are as follows: For non-liquefied areas, no reinforcement is required; For slightly liquefied areas, one or more of the following methods, vibratory compaction, vibratory rolling or vibratory agitation, are used to treat the foundation depth; For moderate liquefaction areas, shallow foundation treatment is used to use the covering soil layer above the liquefiable sand layer as the foundation support layer; For severely liquefied areas, a comprehensive method of vibration reinforcement, grouting reinforcement, pile foundation reinforcement, construction of a composite drainage system and addition of foundation treatment agents is adopted. After reinforcement, the structure of the severely liquefied areas is optimized; Construct a composite waterproofing system: permanent vertical and horizontal pore pressure dissipation drains are set up in the foundation.

8. The method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 7, characterized in that: In step S4, the method for evaluating the seismic liquefaction of the reinforced foundation is a numerical simulation method.

9. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 8, characterized in that: Intelligent monitoring equipment includes soil samplers, power drillers, foundation sonic testers, seismic wave velocity testers and pore water pressure meters.

10. A method for improving the anti-seismic liquefaction performance of a foundation based on a long underground structure according to claim 9, characterized in that: In step S5, when the reinforcement plan formulation module saves the evaluation results sent by the intelligent monitoring module, the reinforcement plan formulation module directly gives the corresponding reinforcement plan; when the reinforcement plan formulation module does not save the evaluation results sent by the intelligent monitoring module, the reinforcement plan formulation module sends the monitoring information and the evaluation results to the expert module, and the expert module sends the corresponding monitoring information to the corresponding engineer terminal. The engineer formulates a new reinforcement plan based on the monitoring information and returns the new reinforcement plan to the reinforcement plan formulation module.

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