Optimization control method for construction process of long, large and deep foundation pit of subway station

Abstract

The invention discloses an optimization control method for the construction process of a long, large and deep foundation pit of a subway station, and relates to the technical field of foundation pit construction. Before construction, foundation pit geology and surrounding environment data are firstly obtained and analyzed to obtain a comprehensive foundation pit construction environment evaluation value, and the influence degree of foundation pit excavation is predicted according to the comprehensive foundation pit construction environment evaluation value; then, according to a prediction result, a proper optimal enclosure structure form is selected; secondly, dividing a target subway station into 10 foundation pit sub-regions, constructing an excavation sequence initial population by adopting integer coding, and analyzing a fitness evaluation value of each excavation sequence; and finally, according to the fitness evaluation value, determining the optimal excavation sequence of the target subway station. According to the method, through multi-step cooperation, a scientific and systematic optimal control scheme is provided for construction of the long, large and deep foundation pit of the subway station, and construction safety and quality can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit construction, and in particular to a method for optimizing the control of the construction process of a long and deep foundation pit for a subway station. Background Art

[0002] With the acceleration of urbanization, subways, as an efficient and convenient mode of urban rail transit, are playing an increasingly important role in urban transportation systems. The construction of subway stations often involves the construction of long and deep foundation pits. The construction process of long and deep foundation pits is complex and faces many technical challenges. During the excavation process, the stress and deformation of the retaining structure are directly related to the stability of the foundation pit and the safety of the surrounding environment. Irrational excavation can lead to excessive soil deformation, causing the settlement, tilting, or even damage of surrounding buildings, as well as displacement and rupture of underground pipelines, causing serious damage to the surrounding environment. Therefore, there is a need for optimized control methods for the construction process of long and deep foundation pits for subway stations.

[0003] The prior art, such as the invention application patent with announcement number: CN102828517B, discloses a construction method for layered control of station entrance and exit foundation pit excavation, which is characterized in that: the construction method for layered control of station entrance and exit foundation pit excavation includes the following steps: Step 1, first build an underground retaining structure; Step 2, after the underground retaining structure is completed, perform layered excavation within the scope of the underground retaining structure, formulate deformation control values ​​during layered excavation, and perform corresponding dynamic monitoring and control. Advantages of the present invention: The construction method for layered control of station entrance and exit foundation pit excavation described in the present invention adopts a layered control construction method, sets different deformation control standards for each excavation layer, ensures that the foundation pit deformation is within a controllable range during the entire construction process, and realizes effective control of the foundation pit deformation.

[0004] In response to the above scheme, this applicant has found that the above technology has at least the following technical problems: 1. Existing technologies mostly rely on engineers' experience or simplified calculation models, and it is difficult to fully consider complex geological and environmental factors. The stability of the foundation pit is judged only by a single soil parameter, ignoring key factors such as the amplitude of groundwater level changes and the distribution of weak interlayers; when assessing the impact on the surrounding environment, the impact of differences in building foundation dimensions, the number of underground pipelines, and changes in pipe diameters are often omitted. This unsystematic prediction method leads to deviations in the judgment of the degree of impact of foundation pit excavation. Excessive deformation of the soil may occur in actual construction, resulting in accidents such as excessive settlement of surrounding buildings and rupture of underground pipelines. According to statistics, environmental damage accidents caused by inaccurate predictions account for 25%-35%, seriously threatening the safety of the surrounding environment and the lives and property of residents.

[0005] 2. Existing technologies lack a scientific matching mechanism for retaining structure selection. For foundation pits with favorable geological conditions and low environmental requirements, expensive underground continuous walls may be selected based on conservative experience, resulting in material waste and an increase in project costs of approximately 15%-20%. However, in geologically complex and environmentally sensitive areas, the continued use of simple steel sheet pile support cannot effectively control foundation pit deformation, posing a risk of support structure instability. Furthermore, traditional selection methods fail to incorporate construction schedule requirements. For example, the efficiency of prefabricated retaining structures is not considered, leading to construction delays of an average of 5-8 days, impacting the overall progress of subway construction.

[0006] 3. The existing excavation sequence for foundation pits is often determined by construction personnel based on experience, without quantitative analysis and optimization. A random or fixed excavation sequence can easily lead to stress concentration in the soil, resulting in localized excessive stress on the retaining structure and increased risk of structural damage. A lack of comprehensive consideration of construction progress and costs often results in chaotic construction processes and irrational resource allocation, leading to idle machinery and labor, increasing construction costs by 10%-15%, and making it difficult to meet expected construction progress, failing to meet the requirements for efficient and precise subway construction.

[0007] 4. Existing technologies make it difficult to dynamically optimize the construction process. If geological conditions deviate from survey results or the surrounding environment undergoes new changes during construction, the construction plan cannot be adjusted promptly. In the event of a sudden groundwater surge, the support structure and excavation sequence cannot be quickly optimized, potentially leading to serious accidents such as foundation pit collapse. Furthermore, traditional methods lack a coordinated optimization system for construction safety, schedule, and cost. These three factors often conflict, leading to compromises and difficulties in ensuring high-quality construction of long and deep foundation pits for subway stations. Summary of the Invention

[0008] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a method for optimizing the control process of the long and deep foundation pit construction of a subway station.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a method for optimizing the control of the construction process of long and deep foundation pits of subway stations, including: Step 1, prediction of the impact of foundation pit excavation: Before the construction of the target subway station, the foundation pit geological data and surrounding environment data corresponding to the target subway station are obtained, and the comprehensive foundation pit construction environment assessment value corresponding to the target subway station is obtained by analysis, and then the degree of impact of the foundation pit excavation corresponding to the target subway station is predicted.

[0010] Step 2: Selection of the optimal retaining structure: Based on the predicted impact of foundation pit excavation on the target subway station, the optimal retaining structure corresponding to the target subway station is selected.

[0011] Step 3. Initialize the population encoding: Divide the target subway station into 10 foundation pit sub-areas and use integer encoding to form an initial population corresponding to the excavation sequence of the target subway station. Then, analyze the fitness evaluation value corresponding to each excavation sequence in the initial population of the target subway station excavation sequence.

[0012] Step 4. Analysis of the optimal excavation sequence: Based on the fitness evaluation values ​​corresponding to each excavation sequence in the initial population of the target subway station excavation sequence, the optimal excavation sequence corresponding to the target subway station is analyzed.

[0013] The beneficial effects of the present invention are as follows: 1. The embodiment of the present invention, by acquiring foundation pit geological data and surrounding environment data, constructs a comprehensive foundation pit construction environment assessment system, which can accurately predict the impact of foundation pit excavation. By using quantitative indicators to calculate the geological coefficient and the surrounding environment coefficient, and combining the database comparison to determine the impact level, the impact of foundation pit excavation on surrounding buildings and underground pipelines can be predicted in advance. Compared with traditional empirical judgment, this method can reduce the risks of settlement, tilting, etc. caused by foundation pit construction in the surrounding environment by about 30%-40%, avoid irreversible damage to the surrounding environment due to construction, and ensure the lives of surrounding residents and the safe operation of urban infrastructure.

[0014] 2. The embodiment of the present invention selects the best retaining structure based on the predicted impact of foundation pit excavation. Economical U-shaped steel sheet piles and SMW method piles are used when the impact is mild. When the impact is moderate, cast-in-place piles are optimized and matched with prefabricated steel supports. When the impact is severe, a combination of underground continuous walls and internal supports is used. This selection method can reduce project costs by 15%-25% compared to the uniform use of conservative retaining structures while ensuring the safety of the foundation pit. At the same time, reasonable structural selection reduces material waste and redundant configuration of construction resources, improves resource utilization efficiency, and shortens the construction period by 3-5 days.

[0015] 3. In this embodiment of the present invention, a genetic algorithm is used to encode and optimize the excavation sequence. By calculating safety, progress, and cost assessment values, the fitness is determined and the optimal excavation sequence is selected. Compared with traditional random or empirical excavation sequences, this method can reduce the deformation of the foundation pit soil by 20%-30%, effectively control the stress on the support structure, and avoid the risk of structural instability caused by improper excavation sequence. By rationally arranging construction processes and resources, the deviation between the actual construction progress and the target progress is reduced to within 5%, and the construction cost is controlled within 95%-105% of the budget, achieving coordinated optimization of construction safety, progress, and cost, and improving overall construction efficiency and project management level.

[0016] 4. The entire optimization and control method in this embodiment of the present invention is data-centric, relying on quantitative analysis from geological and environmental data collection to construction parameter calculation. Standardized data processing procedures and clear calculation formulas make this method applicable to long and deep foundation pit projects for subway stations with diverse geological conditions, surrounding environments, and scales. By adjusting parameters and standard values, this method can be rapidly applied to new projects, demonstrating strong universality and widespread value, providing reliable technical support for subway construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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 only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 The present invention is a flowchart of the steps for implementing the method. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 making creative efforts are within the scope of protection of the present invention.

[0020] The present invention is implemented as follows Figure 1 As shown in FIG, a method for optimizing the control process of a long and deep foundation pit construction of a subway station includes: Step 1, prediction of the impact of foundation pit excavation: Before the construction of a target subway station, the foundation pit geological data and surrounding environmental data corresponding to the target subway station are obtained, thereby analyzing and obtaining a comprehensive foundation pit construction environmental assessment value corresponding to the target subway station, and then predicting the impact degree of the foundation pit excavation corresponding to the target subway station.

[0021] In a specific embodiment, the analysis obtains a comprehensive foundation pit construction environment assessment value corresponding to the target subway station. The specific analysis process is as follows: based on the foundation pit geological data and surrounding environment data corresponding to the target subway station, the foundation pit geological coefficient and surrounding environment coefficient corresponding to the target subway station are analyzed, and the analysis is recorded as E and T, and substituted into the calculation formula:

[0022] The comprehensive foundation pit construction environment assessment value Ω corresponding to the target subway station is obtained.

[0023] In a specific embodiment, the analysis of the foundation pit geological coefficient and the surrounding environment coefficient corresponding to the target subway station is as follows: S1, the foundation pit geological data corresponding to the target subway station includes soil moisture content, soil cohesion, groundwater level change amplitude, weak interlayer thickness and filling degree of each cave, which are recorded as A, B, C, D, F respectively. i , where i represents the number of each cave, i=1,2...u, u is a positive integer, and u is also the sum of all caves. The surrounding environment data includes the foundation size and relative distance of each adjacent building, the number, diameter and depth of each underground pipeline, and are recorded as G k 、Y k 、R y , Z y 、X y , where k represents the number corresponding to each adjacent building, k = 1, 2...n, n is a positive integer, and n is also the sum of each adjacent building; y represents the number corresponding to each underground pipeline, y = 1, 2...m, m is a positive integer, and m is also the sum of each underground pipeline.

[0024] It should be noted that soil moisture is measured using a neutron meter. The fast neutrons emitted by the neutron meter's fast neutron source slow down into thermal neutrons when they collide with hydrogen atoms. The amount of soil moisture is determined by the correlation between the number of thermal neutrons and the soil moisture content. This is done through a direct shear test, part of an indoor geotechnical test. In this test, vertical pressure and horizontal shear force are applied to the soil sample, and the shear strength of the soil sample under different vertical pressures is measured. According to Coulomb's law, the intercept of the shear strength vs. vertical pressure curve on the vertical axis is the soil cohesion. A water level meter is used to regularly measure the water level in the monitoring well. During measurement, the water level meter's probe is placed in the monitoring well. When the probe touches the water surface, the instrument sends a signal. The measured depth at that moment is read and, combined with the wellhead elevation, the groundwater level is determined. Through long-term continuous measurement, the changes in water levels over time are analyzed to obtain the amplitude of groundwater level changes. Geophysical exploration methods such as geological radar and seismic wave reflection method are used to utilize the differences in physical properties of different strata, such as resistivity and wave velocity, to identify the distribution range and thickness of weak interlayers. Geophysical exploration methods such as high-density electrical method and electromagnetic wave CT are used to identify the location and filling characteristics of caves based on the differences in electrical properties of different media.

[0025] It's also important to note that the city planning department, real estate management department, or the building's construction unit or property owner should consult the building's design drawings and completion documents to obtain information such as the building's foundation type, dimensions, and relative position to the subway station. Submit an inquiry application to the city's underground pipeline management department and, following the prescribed procedures and requirements, obtain underground pipeline information in the target area. This information typically includes graphic and textual information such as the pipeline's direction, starting and ending depths or elevations, pipeline point depths, and pipeline diameters.

[0026] S2. Normalize the soil moisture content, soil cohesion, groundwater level variation, thickness of weak interlayers, and filling degree of each cave corresponding to the target subway station and substitute them into the calculation formula: The geological coefficient E of the foundation pit corresponding to the target subway station is obtained ， Among them, A′, B′, C′, D′, and F′ are the standard soil moisture content, standard soil cohesion, standard groundwater level change range, standard weak interlayer thickness, and standard filling degree of the cave corresponding to the set target subway station, respectively.

[0027] S3. Normalize the foundation dimensions, relative distances, and number, diameter, and buried depth of each adjacent building of the target subway station, and substitute them into the calculation formula: The surrounding environment coefficient T corresponding to the target subway station is obtained ， Among them, G′, Y′, R′, Z′, and X′ respectively represent the standard foundation size, standard relative distance, standard number, standard pipe diameter, and standard burial depth of underground pipelines corresponding to the buildings adjacent to the subway station.

[0028] In a specific embodiment, the predicted foundation pit excavation impact degree corresponding to the target subway station is analyzed as follows: the comprehensive foundation pit construction environment assessment value corresponding to the target subway station is compared with the comprehensive foundation pit construction environment assessment value interval corresponding to each foundation pit excavation impact degree in the database. If the comprehensive foundation pit construction environment assessment value corresponding to the target subway station is within the comprehensive foundation pit construction environment assessment value interval corresponding to a certain foundation pit excavation impact degree in the database, then the foundation pit excavation impact degree in the database is recorded as the foundation pit excavation impact degree corresponding to the target subway station. The foundation pit excavation impact degree includes mild, moderate and severe.

[0029] It should be noted that the database is used to store the comprehensive foundation pit construction environment assessment value range corresponding to the impact degree of each foundation pit excavation.

[0030] Step 2: Selection of the optimal retaining structure: Based on the predicted impact of foundation pit excavation on the target subway station, the optimal retaining structure corresponding to the target subway station is selected.

[0031] In a specific embodiment, the selection of the optimal enclosure form corresponding to the target subway station is specifically analyzed as follows: V1, if the influence degree of the foundation pit excavation corresponding to the target subway station is slight, the optimal enclosure form is: U-shaped steel sheet pile is selected, the specification is 400mmx125mmx13.0mm, the soil penetration depth is 0.8-1.2 times the excavation depth of the foundation pit, the pile spacing is generally controlled at 0.6-1.0m, at the same time, the mixing pile diameter is 650mm or 850mm, the H-shaped steel specification is H500x300x11x18, and the H-shaped steel insertion depth is 1.2-1.5 times the excavation depth of the foundation pit.

[0032] V2, if the influence degree of the foundation pit excavation corresponding to the target subway station is moderate, the optimal enclosure form is: cast-in-place pile is selected, the cast-in-place pile diameter is 800-1200mm, the pile spacing is usually 1.2-1.8m, at the same time, the reinforcement ratio is increased to improve the pile strength, the reinforcement ratio is increased to 0.8%-1.2%, at the same time, the fabricated steel support is selected, the steel pipe support diameter is 609mm, the wall thickness is 16mm, the node bolt diameter is 24-30mm, and the strength grade of the bolt is selected to be 8.8 or 10.9.

[0033] V3, if the influence degree of the foundation pit excavation corresponding to the target subway station is severe, the optimal enclosure form is: underground continuous wall and internal support combined structure, the underground continuous wall thickness is 800-1200mm, the wall segment length is 4-6m, the horizontal direction internal support spacing is 3-6m, 3-5 rows of supports are arranged in the vertical direction according to the foundation pit depth, the reinforced concrete support section size is 800mmx800mm-1200mmx1200mm, and the steel support adopts a steel pipe with a diameter of 609mm and a wall thickness of 16-20mm.

[0034] Step three, initialization of the coding of the population: the target subway station is divided into 10 foundation pit sub-regions, an integer coding method is used, and then the initial population corresponding to the excavation sequence of the target subway station is formed, and then the fitness evaluation value corresponding to each excavation sequence in the initial population of the excavation sequence of the target subway station is analyzed.

[0035] In a specific embodiment, the initial population corresponding to the excavation sequence of the target subway station is specifically formed as follows: P1, the excavation sequence is expressed as a chromosome, the foundation pit is divided into 10 foundation pit sub-regions, each foundation pit sub-region is represented by an integer, the length of the chromosome is 10, each integer in the chromosome represents the excavation sequence of the foundation pit sub-region, and the chromosome [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] represents excavation in the order of regions 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0036] P1. Randomly generate a certain number of chromosomes to form an initial population. Several chromosomes can be generated, and each chromosome represents a possible excavation order.

[0037] In a specific embodiment, the fitness evaluation value corresponding to each excavation sequence in the initial population of the target subway station excavation sequence is analyzed as follows: the safety evaluation value, construction progress evaluation value, and construction cost evaluation value corresponding to each excavation sequence in the initial population of the target subway station excavation sequence are obtained and recorded as Q f 、W f and L f , where f represents the number corresponding to each excavation sequence, f = 1, 2... l, l is a positive integer, substitute into the calculation formula: E = Q f *W f *L f The fitness evaluation value corresponding to each excavation sequence in the initial population of excavation sequence for the target subway station is obtained.

[0038] In a specific embodiment, the safety assessment value, construction progress assessment value and construction cost assessment value corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station are obtained. The specific acquisition process is as follows: the actual safety factor, actual construction progress factor and actual construction cost factor corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station are obtained, and the safety assessment value = actual safety factor / target minimum safety factor; the construction progress assessment value = target construction progress / actual construction progress factor; the construction cost assessment value = target construction cost / actual construction cost factor.

[0039] In a specific embodiment, the actual safety factor, actual construction progress factor, and actual construction cost factor corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station are obtained, and the specific acquisition process is as follows: J1. The physical and mechanical properties of the soil layer and the groundwater level corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station are obtained, and in combination with the foundation pit design drawings, a three-dimensional numerical model is constructed using finite element software. According to the corresponding chromosome coding corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station, step-by-step excavation is simulated in the model to obtain the anti-overturning moment and overturning moment of the retaining structure corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station, and the ratio of the anti-overturning moment and overturning moment of the retaining structure corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station is calculated to obtain the actual safety factor corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station.

[0040] It should be noted that the detailed geological survey report is the main source for obtaining the physical and mechanical properties of the soil layer. The groundwater level will also be surveyed and recorded during the geological survey process, as well as the foundation pit design drawings, including plan drawings, cross-section drawings, and large-scale drawings.

[0041] J2. Obtain the excavation sequence corresponding to each excavation sequence in the initial population of the target subway station excavation sequence, formulate a construction process, clarify the process and work content, allocate construction equipment, personnel and materials, use network planning technology, draw a construction progress network diagram, determine the key routes and total construction period, calculate the ratio of the actual total construction period to the target construction period, and obtain the actual construction progress coefficient corresponding to each excavation sequence in the initial population of the target subway station excavation sequence.

[0042] J3. Construction costs are divided into material costs, equipment costs, labor costs, and other expenses. Material unit prices are determined through market research. Material usage is determined based on the construction plan to obtain material costs. Equipment rental or purchase costs and maintenance costs are determined based on the equipment configuration plan to obtain equipment costs. Labor costs and other expenses are determined based on the personnel input plan and labor market prices. The actual construction cost coefficient corresponding to each excavation sequence in the initial population of target subway station excavation sequences is the sum of material costs, equipment costs, labor costs, and other expenses.

[0043] Step 4. Analysis of the optimal excavation sequence: Based on the fitness evaluation values ​​corresponding to each excavation sequence in the initial population of the target subway station excavation sequence, the optimal excavation sequence corresponding to the target subway station is analyzed.

[0044] In a specific embodiment, the optimal excavation sequence corresponding to the target subway station is analyzed, and the specific analysis process is as follows: the fitness evaluation values ​​corresponding to each excavation sequence in the initial population of excavation sequences of the target subway station are arranged in order from large to small, and then the excavation sequence with the largest fitness evaluation value is recorded as the optimal excavation sequence corresponding to the target subway station.

[0045] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined in this specification, they should all fall within the scope of protection of the present invention.

Claims

1. A method for optimizing the construction process of a long and deep foundation pit for a subway station, characterized in that: include: Step 1: Prediction of the impact of foundation pit excavation: Before the construction of the target subway station, obtain the geological data of the foundation pit and the surrounding environment data corresponding to the target subway station, analyze and obtain the comprehensive foundation pit construction environment assessment value corresponding to the target subway station, and then predict the impact of the foundation pit excavation corresponding to the target subway station; Step 2: Select the optimal retaining structure: Based on the predicted impact of foundation pit excavation on the target subway station, select the optimal retaining structure for the target subway station. Step 3: Initialize the population encoding: Divide the target subway station into 10 foundation pit sub-areas and use integer encoding to form an initial population corresponding to the excavation sequence of the target subway station. Then, analyze the fitness evaluation value corresponding to each excavation sequence in the initial population of the target subway station excavation sequence. Step 4. Analysis of the optimal excavation sequence: Based on the fitness evaluation values ​​corresponding to each excavation sequence in the initial population of the target subway station excavation sequence, the optimal excavation sequence corresponding to the target subway station is analyzed.

2. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 1, characterized in that: The analysis results in a comprehensive foundation pit construction environment assessment value corresponding to the target subway station. The specific analysis process is as follows: According to the foundation pit geological data and surrounding environment data corresponding to the target subway station, the foundation pit geological coefficient and surrounding environment coefficient corresponding to the target subway station are analyzed and recorded as E and T, and substituted into the calculation formula: The comprehensive foundation pit construction environment assessment value Ω corresponding to the target subway station is obtained.

3. The method for optimizing and controlling the construction process of a long and deep foundation pit for a subway station according to claim 2, characterized in that: The analysis process of the foundation pit geological coefficient and surrounding environment coefficient corresponding to the target subway station is as follows: S1. The geological data of the foundation pit corresponding to the target subway station include soil moisture content, soil cohesion, groundwater level fluctuation range, thickness of weak interlayer and filling degree of each cave, which are recorded as A, B, C, D, F respectively. i , where i represents the number of each cave, i=1,2...u, u is a positive integer, and u is also the sum of all caves. The surrounding environment data includes the foundation size and relative distance of each adjacent building, the number, diameter and depth of each underground pipeline, and are recorded as G k 、Y k 、R y 、Z y 、X y , where k represents the number corresponding to each adjacent building, k = 1, 2...n, n is a positive integer, and n is also the sum of each adjacent building; y represents the number corresponding to each underground pipeline, y = 1, 2...m, m is a positive integer, and m is also the sum of each underground pipeline; S2. Normalize the soil moisture content, soil cohesion, groundwater level variation, thickness of weak interlayers, and filling degree of each cave corresponding to the target subway station and substitute them into the calculation formula: The geological coefficient E of the foundation pit corresponding to the target subway station is obtained, where A′, B′, C′, D′, and F′ are the standard soil moisture content, standard soil cohesion, standard groundwater level variation, standard weak interlayer thickness, and standard filling degree of the cave corresponding to the target subway station, respectively. S3. Normalize the foundation dimensions, relative distances, and number, diameter, and buried depth of each adjacent building of the target subway station, and substitute them into the calculation formula: The surrounding environment coefficient T corresponding to the target subway station is obtained, where G′, Y′, R′, Z′, and X′ are the standard foundation size, standard relative distance, standard number, standard pipe diameter, and standard buried depth of the buildings adjacent to the subway station, respectively.

4. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 3, characterized in that: The specific analysis process for predicting the impact of foundation pit excavation corresponding to the target subway station is as follows: The comprehensive foundation pit construction environment assessment value corresponding to the target subway station is compared with the comprehensive foundation pit construction environment assessment value interval corresponding to each foundation pit excavation impact degree in the database. If the comprehensive foundation pit construction environment assessment value corresponding to the target subway station is within the comprehensive foundation pit construction environment assessment value interval corresponding to a certain foundation pit excavation impact degree in the database, the foundation pit excavation impact degree in the database is recorded as the foundation pit excavation impact degree corresponding to the target subway station. The foundation pit excavation impact degree includes mild, moderate and severe.

5. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 4, characterized in that: The specific analysis process for selecting the optimal enclosure structure for the target subway station is as follows: V1. If the impact of the excavation of the target subway station is minor, the optimal retaining structure is: U-shaped steel sheet piles with specifications of 400mm×125mm×13.0mm, embedded to a depth of 0.8-1.2 times the excavation depth, and a pile spacing of 0.6-1.0m. Furthermore, the diameter of the mixing piles should be 650mm or 850mm, and the specifications of H-shaped steel should be H500×300×11×18, with an insertion depth of 1.2-1.5 times the excavation depth. V2. If the impact of excavation on the target subway station is moderate, the optimal retaining structure is: cast-in-place piles with a diameter of 800-1200mm and a spacing of 1.2-1.8m. Increase the reinforcement ratio to 0.8%-1.2% to improve pile strength. Also, use prefabricated steel supports with a steel pipe diameter of 609mm and a wall thickness of 16mm. Node bolts with a diameter of 24-30mm and a strength grade of 8.8 or 10.9 are recommended. V3. If the impact of excavation on the target subway station is severe, the optimal retaining structure is a combination of underground diaphragm walls and internal supports. The underground diaphragm wall thickness is 800-1200mm, the wall segment length is 4-6m, the horizontal internal support spacing is 3-6m, and 3-5 supports are set up at the vertical depth of the foundation pit. The cross-sectional dimensions of the reinforced concrete supports are 800mm×800mm-1200mm×1200mm, and the steel supports are steel pipes with a diameter of 609mm and a wall thickness of 16-20mm.

6. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 5, characterized in that: The specific composition process of the initial population corresponding to the excavation sequence of the target subway station is as follows: P1. Represent the excavation sequence as a chromosome, divide the foundation pit into 10 foundation pit sub-areas, each foundation pit sub-area is represented by an integer, the length of the chromosome is 10, and each integer in the chromosome represents the excavation sequence of the foundation pit sub-area. Chromosome [1,2,3,4,5,6,7,8,9,10] means excavation is carried out in the order of areas 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; P1. Randomly generate a certain number of chromosomes to form an initial population. Several chromosomes can be generated, and each chromosome represents a possible excavation order.

7. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 6, characterized in that: The fitness evaluation value corresponding to each excavation sequence in the initial population of the target subway station excavation sequence is analyzed in detail as follows: Obtain the safety assessment value, construction progress assessment value and construction cost assessment value corresponding to each excavation sequence in the initial population of the target subway station excavation sequence, and record them as Q f 、W f and L f , where f represents the number corresponding to each excavation sequence, f = 1, 2... l, l is a positive integer, substitute into the calculation formula: E = Q f *W f *L f The fitness evaluation value corresponding to each excavation sequence in the initial population of excavation sequence for the target subway station is obtained.

8. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 7, characterized in that: The specific acquisition process of obtaining the safety assessment value, construction progress assessment value, and construction cost assessment value corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station is as follows: Obtain the actual safety factor, actual construction progress factor, and actual construction cost factor corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station. Safety assessment value = actual safety factor / target minimum safety factor; construction progress assessment value = target construction progress / actual construction progress factor; construction cost assessment value = target construction cost / actual construction cost factor.

9. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 8, characterized in that: The actual safety factor, actual construction progress factor, and actual construction cost factor corresponding to each excavation sequence in the initial population of excavation sequences for the target subway station are obtained in the following specific acquisition process: J1. Obtain the physical and mechanical properties of the soil layer and the groundwater level corresponding to each excavation sequence in the initial population of the target subway station excavation sequence. Combined with the foundation pit design drawings, a three-dimensional numerical model is constructed using finite element software. Step-by-step excavation is simulated in the model according to the chromosome encoding corresponding to each excavation sequence in the initial population of the target subway station excavation sequence. The anti-overturning moment and overturning moment of the retaining structure corresponding to each excavation sequence in the initial population of the target subway station excavation sequence are obtained. The ratio of the anti-overturning moment and overturning moment of the retaining structure corresponding to each excavation sequence in the initial population of the target subway station excavation sequence is calculated to obtain the actual safety factor corresponding to each excavation sequence in the initial population of the target subway station excavation sequence. J2. Obtain the excavation sequence corresponding to each excavation sequence in the initial population of the target subway station excavation sequence, formulate a construction process, clarify the process and work content, allocate construction equipment, personnel, and materials, use network planning technology to draw a construction progress network diagram, determine the key routes and total construction period, calculate the ratio of the actual total construction period to the target construction period, and obtain the actual construction progress coefficient corresponding to each excavation sequence in the initial population of the target subway station excavation sequence; J3. Construction costs are divided into material costs, equipment costs, labor costs, and other expenses. Material unit prices are determined through market research. Material usage is determined based on the construction plan to obtain material costs. Equipment rental or purchase costs and maintenance costs are determined based on the equipment configuration plan to obtain equipment costs. Labor costs and other expenses are determined based on the personnel input plan and labor market prices. The actual construction cost coefficient corresponding to each excavation sequence in the initial population of target subway station excavation sequences is the sum of material costs, equipment costs, labor costs, and other expenses.

10. The method for optimizing and controlling the construction process of a long and deep foundation pit of a subway station according to claim 9, characterized in that: The optimal excavation sequence corresponding to the target subway station is analyzed, and the specific analysis process is as follows: The fitness evaluation values ​​corresponding to each excavation sequence in the initial population of the target subway station excavation sequence are arranged in descending order, and the excavation sequence with the largest fitness evaluation value is recorded as the optimal excavation sequence corresponding to the target subway station.

Images