Soil body excavation and ballasting method based on numerical simulation optimization

Abstract

The invention discloses a soil body excavation and ballasting method based on numerical simulation optimization, and relates to the technical field of excavation construction. The soil excavation and ballasting method based on numerical simulation optimization comprises the method steps of foundation pit zoning, excavation scheme determining, field monitoring scheme determining, field excavation construction, dynamic monitoring and real-time adjusting and underground structure construction, zoning is conducted in the horizontal direction, zoning is also conducted in the vertical direction, and the underground structure is constructed. And interval excavation is conducted by adopting a method that multiple interval areas are propelled at the same time. And in the excavation construction process, according to the real-time numerical simulation result, the excavation scheme is dynamically adjusted, and the excavation construction efficiency is improved to the maximum extent. And in the aspect of deformation control, according to a field deformation monitoring result, a pre-arranged plan of adding ballast to an area with large deformation is added, and the deformation control effect in the excavation process is ensured. The method has good deformation control over the excavation process, the safety of the underlying operation subway tunnel is enhanced, and the construction efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of excavation construction, and particularly relates to a soil excavation and ballast method optimized based on numerical simulation. Background Art

[0002] With the acceleration of the urbanization process, the development and utilization of underground space has become an important means to relieve the tension of ground space and improve the urban carrying capacity.

[0003] In a dense urban environment, foundation pit excavation often involves interaction with existing subway tunnels. During the foundation pit excavation process, factors such as the redistribution of stratum stress, the change of groundwater, and the deformation of the support structure will have varying degrees of influence on the underlying subway tunnel. These influences include the deformation of the tunnel structure, surface settlement, the change of groundwater level, etc. If these factors are not properly controlled, it may pose a serious threat to the safe operation of the subway tunnel. Moreover, the form of change in ground stress during foundation pit excavation under the condition of long-distance overlap of subway tunnels is different from that of general projects, and the deformation mechanism of the stratum and the underlying subway tunnel caused thereby is also different. The existing technology lacks deformation control measures during the excavation process.

[0004] Therefore, the excavation construction method needs to be correspondingly improved to meet the requirements of engineering construction. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing excavation construction of the foundation pit overlapping with the subway tunnel has an adverse impact on the subway tunnel. The purpose is to provide a soil excavation and ballast method optimized based on numerical simulation, adopting corresponding technical solutions, which has good deformation control during the excavation process, enhances the safety of the underlying operating subway tunnel, and improves the construction efficiency.

[0006] The present invention is achieved by the following technical solutions:

[0007] A soil excavation and ballast method optimized based on numerical simulation, which includes the following steps,

[0008] Foundation pit zoning:

[0009] First, divide the overall area of a predetermined depth in the vertical direction of the foundation pit, and divide it into several spaced areas in the horizontal direction below the predetermined depth;

[0010] Determine the excavation plan:

[0011] Use the hardening soil model to model the foundation pit excavation, check whether the excavation plan meets the requirements, and on this basis, determine the optimal excavation plan for the foundation pit zoning by changing the depth parameter of the overall area excavation, the range parameter of a single spaced area, and the number parameter of the simultaneously excavated spaced areas;

[0012] Determine the on-site monitoring plan:

[0013] Arrange displacement monitoring points in the subway tunnel. The monitoring range covers both ends outside the overlapping area. Record the displacement data of the subway tunnel and check whether it meets the protection standards of the subway tunnel;

[0014] On-site excavation construction:

[0015] Excavate and remove the entire area of the foundation pit, pour the first internal support, and then carry out earth excavation according to the method of at least one interval area. After excavating to the bottom of the pit, apply ballast to the bottom of the pit;

[0016] Dynamic monitoring and real-time adjustment:

[0017] During the excavation process, continuously monitor the deformation of the subway tunnel. Conduct numerical simulation of the excavation process based on the real-time soil layer parameters. Combine the monitoring data to predict the deformation impact of the next excavation construction on the subway. For working conditions with small deformation, increase the excavation width and the number of interval areas for excavation. For working conditions with large deformation, reduce the excavation width and increase the ballast load on the excavated area;

[0018] Underground structure construction:

[0019] For the excavated foundation pit, construct the foundation pit floor and underground structure. After the underground structure construction is completed, backfill the soil.

[0020] Furthermore, in the present invention, the method for verifying the excavation plan in the step of determining the excavation plan is as follows: First, select the hardening soil model, draw the plan of the model, then import it into the finite element software to establish the geometric model, then perform mesh division and assign material parameters to the mesh, then apply loads and boundary conditions, then deactivate the mesh in the excavation area to simulate the excavation process, and finally calculate the established model. According to the results of the calculated values, compare the deformation control effects of different excavation plans.

[0021] Furthermore, in the present invention, the above hardening soil model calculates the elastic modulus of the soil mass using the following formula,

[0022] E = 2ρV s 2 (1 + v)

[0023] In the formula, E is the elastic modulus of the soil mass, ρ is the density of the soil mass, V s is the shear wave velocity of the soil mass, and v is the Poisson's ratio of the soil mass.

[0024] Furthermore, in the present invention, in the above step of foundation pit zoning, the predetermined depth is 1 meter to 3 meters.

[0025] Further, in the present invention, in the step of determining the on-site monitoring plan, the displacement monitoring points are arranged at equal intervals in the subway tunnel, and the interval between the arrangements does not exceed 5 meters.

[0026] Further, in the present invention, in the step of determining the on-site monitoring plan, the monitoring range extends not less than 50 meters at both ends beyond the overlapping area.

[0027] Further, in the present invention, in the step of determining the on-site monitoring plan, the time points for the displacement monitoring points to collect the displacement data of the subway tunnel are the start stage, the middle stage, and the end stage during the excavation process.

[0028] Further, in the present invention, in the step of on-site excavation construction, the internal support includes vertical column piles and horizontal concrete supports.

[0029] Further, in the present invention, in the step of on-site excavation construction, the ballast uses multiple layers of counterweight blocks, and the counterweight blocks are stacked staggered up and down.

[0030] Further, in the present invention, in the step of dynamic monitoring and real-time adjustment, the excavation range is reduced for the deformation approaching the warning value, and the excavation area is ballasted with plain concrete.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] The present invention improves the excavation method and deformation control measures for the situation where the foundation pit excavation overlaps with the subway tunnel over a long distance. In terms of the sectional excavation of the foundation pit, in addition to sectionalizing in the horizontal direction, it is also sectionalized in the vertical direction, including the upper and lower parts of the overall area and the interval area, and the method of simultaneous advancement of multiple interval areas is used for interval excavation. In determining the excavation plan, the hardening soil constitutive model more suitable for the numerical simulation of foundation pit excavation is adopted, and the parameters of the soil layer are determined through on-site wave velocity tests, significantly improving the accuracy of the numerical simulation results. During the excavation construction process, according to the real-time numerical simulation results, the excavation plan is dynamically adjusted to maximize the efficiency of the excavation construction. In terms of deformation control, according to the results of on-site deformation monitoring, a pre-plan for increasing ballast in the areas with larger deformation is made to ensure the deformation control effect during the excavation process. The soil excavation and ballast methods optimized based on numerical simulation will significantly improve the construction efficiency, resource utilization rate, and deformation control accuracy of the excavation construction under the condition of long-distance overlap between the foundation pit and the subway. This method realizes the precise control of soil deformation and the deformation of the underlying structure by comprehensively analyzing and optimizing using three-dimensional numerical simulation technology before construction and combining real-time monitoring and dynamic adjustment during the construction process. It not only greatly improves the safety and economy of the construction, but also ensures the completion of the project on schedule and efficiently, and provides a new technical means for the design and construction of similar projects, with broad application prospects. Brief Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings. In the drawings:

[0034] Figure 1 is the plan view of the overall area of the foundation pit and the subway tunnel;

[0035] Figure 2 is the plan view of the spaced area of the foundation pit and the subway tunnel;

[0036] Figure 3 is the distribution schematic diagram of displacement monitoring points;

[0037] Figure 4 is the cross-sectional schematic diagram of subway tunnel monitoring;

[0038] Figure 5 is the schematic diagram of ballast;

[0039] Figure 6 is the simulation flow chart;

[0040] Figure 7 is the cross-sectional schematic diagram of the support of the foundation pit and the subway tunnel;

[0041] Figure 8 is the data schematic diagram of displacement monitoring.

[0042] Reference numerals in the drawings and corresponding component names: 1 - foundation pit, 2 - overall area, 3 - spaced area, 4 - displacement monitoring point, 5 - total station, 6 - counterweight block, 7 - bottom plate. Detailed Embodiments

[0043] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments and the drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention. The following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0044] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if the terms "set", "installed", "connected" are used, they 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 directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0045] Embodiment

[0046] Combined with Figure 1 As shown, in a dense urban area, it is planned to build a tunnel foundation pit 1 project, and there is an operating subway tunnel under this project. Since the excavation of foundation pit 1 may have an adverse impact on the underlying subway tunnel, it is necessary to adopt the soil excavation and ballast method based on numerical simulation optimization in this embodiment to ensure the safety of the subway tunnel.

[0047] Partition foundation pit 1, combined with Figure 1 and Figure 2 As shown, in the vertical direction, the predetermined depth of excavation is set to 2 m. Above 2 m is the overall area 2, and below 2 m is divided into 29 spaced areas 3, which are distinguished by dividing lines between the spaced areas 3. As shown in the appendix Figure 2 As shown, the excavation is carried out in 5 working procedures, and the method of excavating at least one spaced area 3 is adopted. For example, in the first excavation, the spaced areas 3 numbered 1, 6, 11, 16, 21, 26 are excavated; in the second excavation, the spaced areas 3 numbered 2, 7, 12, 17, 22, 27 are excavated; in the third excavation, the spaced areas 3 numbered 3, 8, 13, 18, 23, 28 are excavated; in the fourth excavation, the spaced areas 3 numbered 4, 9, 14, 19, 24, 29 are excavated; in the fifth excavation, the spaced areas 3 numbered 5, 10, 15, 20, 25 are excavated.

[0048] The process of determining the excavation plan is as Figure 6 shown. Taking the Midas GTS NX finite element software as an example, the process of numerical simulation is described.

[0049] The first step, sorting out the exploration report and design data: By systematically sorting out the exploration report and design data, basic information such as the stratum distribution, soil layer parameters, support measures, support structure materials, and subway tunnel structure materials on the site is understood.

[0050] Step 2: Determine the numerical model parameters: First, determine the geometric dimensions of the model. Generally, the overall dimension of the model is preferably 3 to 4 times the excavation depth. The thickness parameters of the soil layers can be determined from the soil layer distribution revealed by on-site drilling. Refer to Figure 7 As shown, the measured soil layer distribution from top to bottom is miscellaneous fill, silt, silt, silty clay, silty sand, silt, silty clay with silt. Based on the data from different boreholes, a non-uniform soil layer model consistent with the actual stratum can be established, or it can be assumed that the soil mass is a uniform soil layer and the average thickness of the soil layer is used for modeling. In this embodiment, it is assumed that the soil layer is a uniform soil layer. In this embodiment, measures such as grouting reinforcement, diaphragm wall, and internal support are adopted for deformation control. The internal support includes vertical column piles and horizontal concrete supports. The geometric dimensions of the foundation pit 1 support structure and the cross-section of the subway tunnel are as shown in the appendix Figure 7 shown.

[0051] Then determine the material parameters of the numerical model. The hardening soil model can reflect the differences in the mechanical properties of soil mass during loading and unloading, and has been widely used in the numerical simulation of foundation pit 1 excavation. However, due to the disturbance during the indoor test sampling process, there is a large error between the simulation results of the indoor test parameters and the measured values. Therefore, in this embodiment, the results of on-site wave velocity tests are used to determine the parameters of the model. According to the results of the soil layer wave velocity tests in the on-site test, using the relationship between the shear wave velocity and the elastic modulus, the following formula is used to calculate the elastic modulus of the soil mass:

[0052]

[0053] In the formula, E is the elastic modulus of the soil mass, ρ is the density of the soil mass, V s is the shear wave velocity of the soil mass, and v is the Poisson's ratio of the soil mass. In the hardening soil model, the main parameters controlling the deformation of the soil mass are the secant stiffness of the triaxial test the tangent stiffness of the primary consolidation loading test the unloading elastic modulus These three parameters. Assuming that the unloading of the soil mass satisfies the linear elastic relationship, the unloading elastic modulus can take the value of the elastic modulus determined by the on-site wave velocity test, and the other two stiffness parameters are determined by the proportional relationship determined. Other model parameters can be taken according to the indoor test results provided in the exploration report. The parameter values of the soil mass in this embodiment are as shown in the following soil mass parameter table.

[0054]

[0055] Soil mass parameter table

[0056] The subway tunnel and the support structure are simulated using the linear elastic model, and the material parameters are set according to the actual reinforced concrete characteristics, as shown in the following concrete parameter table.

[0057]

[0058]

[0059] Concrete Parameter Table

[0060] Then draw the CAD plan of the model. According to the geometric scale of the model and the geometric positional relationship between Foundation Pit 1 and the subway tunnel, draw the CAD plan of the model, as Figure 1 shown

[0061] Then import it into the finite element software to establish a geometric model. Import the CAD plan of the model into the Midas GTS NX software, and establish a three-dimensional geometric model through operations such as stretching, scanning, cutting, and moving

[0062] Then conduct mesh generation and assign material parameters to the mesh. Use a mixed method of hexahedrons and tetrahedrons to conduct mesh generation on the geometric model. Establish the material constitutive models of the soil layer and the support structure according to the soil parameter table and the concrete parameter table, and assign the properties of the materials to the divided mesh

[0063] Then apply loads and boundary conditions. Apply the gravitational acceleration to the model to apply the gravitational load, and simulate the ballast after excavation by applying a normal pressure load at the bottom of Foundation Pit 1. Apply a fixed constraint at the bottom of the model and a normal constraint to the sides of the model

[0064] Then passivate the mesh in the excavation area to simulate the excavation process. Establish each excavation analysis step, and passivate the corresponding soil layer mesh in the excavation analysis step to simulate the excavation process of Foundation Pit 1

[0065] Finally, perform calculations and post-process the results. Calculate the established numerical model and extract the displacement nephogram of the calculation results. According to the results of the numerical simulation, compare the deformation control effects of different excavation schemes, and finally determine the optimal excavation scheme

[0066] Determine the on-site monitoring plan. According to the requirements for protecting the subway tunnel, 39 displacement monitoring points 4 are respectively set on the two lines of the subway tunnel. The monitoring numbers are 1 - 39, and the spacing of the displacement monitoring points 4 is 5m. It is divided into two parts: the left line and the right line. The layout of the displacement monitoring points 4 is as Figure 3 shown. And the monitoring range of the displacement monitoring points 4 is extended by 50m respectively at both ends of the overlapping area for more comprehensive monitoring. Record the displacement data of the subway tunnel at the beginning stage, middle stage, and end stage of the excavation process, or collect it once every 5 hours from the beginning stage to the end stage to check whether it meets the protection standards of the subway tunnel

[0067] Combined with Figure 4As shown, 5 observation points (DM1 - DM5) are arranged at each monitoring section, and a total station 5 is used to record the displacement data of each observation point during the construction process.

[0068] After the on-site monitoring plan is determined and implemented, on-site excavation construction is carried out. In the early stage of on-site excavation construction, grouting reinforcement, diaphragm wall and column pouring are carried out. On the basis that the displacement monitoring points 4 are arranged, the overall surface area 2 of the foundation pit 1 is excavated and removed, and then the first internal support is poured. After the construction of the first internal support is completed, earth excavation is carried out in the method of at least one interval area 3 at intervals. After excavation to the bottom of the pit, 6 counterweight blocks are used to load the bottom slab 7 of the bottom of the pit to prevent excessive heave deformation at the bottom of the foundation pit 1 before the bottom construction. As Figure 5 shown, the counterweight blocks 6 are made of four layers of plain concrete blocks and arranged in a staggered manner between the upper and lower layers.

[0069] In the dynamic monitoring and real-time adjustment steps, the parameters of the soil layers at different excavation stages are calculated in real time through on-site wave velocity tests, and the above numerical model is used for real-time numerical simulation to verify with the on-site monitoring values and predict the deformation of the subway tunnel in real time. As Figure 4 shown in the displacement monitoring schematic diagram of the monitoring point 3 (MD3) in Figure 8 shown, according to the results of on-site monitoring and numerical simulation, the on-site monitoring includes the measured vertical displacement and the measured horizontal displacement of the right line, and the numerical simulation includes the calculated vertical displacement and the calculated horizontal displacement of the right line. The excavation range is adjusted in real time. The situation where the deformation is close to the warning value indicates a working condition with large deformation, and it is necessary to reduce the excavation width range and increase the load of the plain concrete on the excavated area. The situation where the deformation is far from the warning value indicates a working condition with small deformation. The excavation range is appropriately expanded to improve the construction efficiency, and the deformation that may be caused by the excavation is evaluated through the numerical model to ensure the safety of the subway tunnel.

[0070] For the excavated area, the construction of the bottom slab 7 of the foundation pit 1 and the underground structure is carried out, and the soil body is backfilled after the construction of the underground structure is completed.

[0071] In summary, the present invention provides a soil excavation and ballasting method optimized based on numerical simulation, including foundation pit 1 zoning: first divide the overall area 2 of a predetermined depth in the vertical direction of the foundation pit 1, and divide it into several interval areas 3 in the horizontal direction below the predetermined depth;

[0072] Determine the excavation plan: use the hardening soil model to model the excavation of the foundation pit 1, check whether the excavation plan meets the requirements, and on this basis, determine the optimal excavation plan for the foundation pit 1 zoning by changing the depth parameter of the excavation of the overall area 2, the range parameter of a single interval area 3, and the number parameter of the simultaneously excavated interval areas 3;

[0073] Determine the on-site monitoring plan: Arrange displacement monitoring points 4 in the subway tunnel, with the monitoring range covering both ends outside the overlapping area, record the displacement data of the subway tunnel, and check whether it meets the protection standards of the subway tunnel;

[0074] On-site excavation construction: Excavate and remove the overall area 2 of the foundation pit 1, pour the first internal support, and then carry out earth excavation in the method of at least one interval area 3 at intervals. After excavating to the bottom of the pit, apply ballast to the bottom of the pit;

[0075] Dynamic monitoring and real-time adjustment: During the excavation process, monitor the deformation of the subway tunnel in real time, conduct numerical simulation of the excavation process based on the real-time soil layer parameters, combine the monitoring data to predict the deformation impact of the next excavation construction on the subway, increase the excavation width and the number of interval areas 3 for the working conditions with small deformation, reduce the excavation width for the working conditions with large deformation, and increase the ballast load for the excavated areas;

[0076] Underground structure construction: For the completed foundation pit 1, carry out the construction of the bottom plate 7 of the foundation pit 1 and the underground structure. After the underground structure construction is completed, backfill the soil body.

[0077] In the embodiment of the present invention, by vertically and horizontally dividing the overlapping area of the foundation pit 1 and the subway tunnel, the excavation area of the foundation pit 1 is divided into the overall area 2 on the surface and the interval area 3 below. The overall area 2 is suitable for overall excavation, and the interval area 3 is suitable for interval excavation. While ensuring that the deformation control of the subway tunnel meets the requirements, the construction efficiency is improved. The present invention also conducts numerical simulation by real-time testing of soil layer parameters through on-site wave velocity tests, combines the on-site monitoring data, and makes real-time predictions on the deformation of the subway tunnel during the current excavation and the next excavation construction, dynamically adjusts the excavation range, reasonably allocates the construction team while ensuring the safety of the underlying subway tunnel, and improves the economy of the project construction. In order to adapt to the characteristics of large-scale and long-distance excavation of the foundation pit 1, in addition to adopting conventional deformation control measures such as grouting, diaphragm wall, and internal support, the present invention adds the deformation control measure of plain concrete ballast after excavation to ensure that excessive uplift deformation occurs at the bottom of the pit before the completion of the underground structure construction, and enhances the safety of the underlying operating subway tunnel.

[0078] The above specific implementation manners further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above is only the specific implementation manners of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A soil excavation and ballasting method based on numerical simulation optimization, characterized in that: The following steps are included: Pit partition: The whole area of ​​the predetermined depth is first divided in the vertical direction of the foundation pit, and the area below the predetermined depth is divided into several interval areas in the horizontal direction; Determine the excavation plan: The hardened soil model is used to model the foundation pit excavation to verify whether the excavation plan meets the requirements. On this basis, the optimal excavation plan for the foundation pit partition is determined by changing the depth parameters of the overall area excavation, the range parameters of the single interval area, and the number parameters of the simultaneous excavation interval areas. Determine the on-site monitoring plan: Arrange displacement monitoring points in the subway tunnel, with the monitoring range covering both ends of the overlapping area, record the displacement data of the subway tunnel, and verify whether it meets the protection standards of the subway tunnel; On-site excavation construction: Excavate and remove the entire area of ​​the foundation pit, cast the first internal support, and then excavate the earth in accordance with the method of at least one interval area, and ballast the bottom of the pit after excavating to the bottom of the pit; Dynamic monitoring and real-time adjustment: During the excavation process, the deformation of the subway tunnel is monitored in real time. According to the real-time soil layer parameters, the excavation process is numerically simulated. Combined with the monitoring data, the deformation impact of the next excavation construction on the subway is predicted. For the working conditions with small deformation, the excavation width and the number of excavation intervals are increased. For the working conditions with large deformation, the excavation width is reduced, and the ballast load is increased in the excavated area. Underground structure construction: For the excavated foundation pit, the foundation pit bottom plate and underground structure are constructed, and the soil is backfilled after the underground structure construction is completed.

2. The soil excavation and ballasting method based on numerical simulation optimization according to claim 1, characterized in that: The method for verifying the excavation plan in the step of determining the excavation plan is to first select the hardened soil model, draw the plane view of the model, then import the finite element software to establish the geometric model, then mesh and assign mesh material parameters, then apply loads and boundary conditions, and then passivate the mesh of the excavation area to simulate the excavation process, and finally calculate the established model, and compare the deformation control effects of different excavation schemes based on the calculated numerical results.

3. The soil excavation and ballasting method based on numerical simulation optimization according to claim 2, characterized in that: The hardened soil model uses the following formula to calculate the elastic modulus of the soil: E=2ρV s 2 (1+v) Where E is the elastic modulus of the soil, ρ is the density of the soil, and V s is the shear wave velocity of the soil, and v is the Poisson's ratio of the soil.

4. The soil excavation and ballasting method based on numerical simulation optimization according to claim 1, characterized in that: In the foundation pit partitioning step, the predetermined depth is 1 meter to 3 meters.

5. The soil excavation and ballasting method based on numerical simulation optimization according to claim 1, characterized in that: In the step of determining the on-site monitoring plan, the displacement monitoring points are arranged at equal intervals in the subway tunnel, and the spacing between them does not exceed 5 meters.

6. The soil excavation and ballasting method based on numerical simulation optimization according to claim 5, characterized in that: In the step of determining the on-site monitoring plan, the monitoring range exceeds the overlapping area at both ends by no less than 50 meters.

7. The soil excavation and ballasting method based on numerical simulation optimization according to claim 6, characterized in that: In the step of determining the on-site monitoring plan, the displacement monitoring points collect the displacement data of the subway tunnel at the beginning, middle and end stages of the excavation process.

8. The soil excavation and ballasting method based on numerical simulation optimization according to claim 1, characterized in that: During the on-site excavation construction steps, the internal support includes vertical column piles and horizontal concrete supports.

9. The soil excavation and ballasting method based on numerical simulation optimization according to claim 1, characterized in that: During the on-site excavation construction steps, multiple layers of counterweight blocks are used for ballast, and the counterweight blocks are stacked alternately up and down.

10. The soil excavation and ballasting method based on numerical simulation optimization according to claim 1, characterized in that: In the dynamic monitoring and real-time adjustment steps, the excavation range is reduced when the deformation is close to the warning value, and the excavation area is ballasted with plain concrete.

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