Micro-settlement control method for extra-long span flat-top straight-wall tunnel under aircraft dynamic load

Abstract

The present application relates to a method for controlling micro-settlement of a super-large span flat-top straight-wall tunnel under the action of an aircraft dynamic load, and relates to the field of tunnel construction technology. The control method includes: S10, distributing the weight of the aircraft to each wheel, and calculating the static load P1 of the aircraft; S20, converting the vertical kinetic energy of the aircraft into an impact force, obtaining a dynamic additional force F, and distributing it to each wheel, and calculating the dynamic load P2 of the aircraft; S30, adding the static load P1 and the dynamic load P2 to obtain the aircraft landing impact load P3; S40, obtaining the distance r from the load application point to the calculation point and the buried depth h of the tunnel, and calculating the settlement S of the tunnel vault according to the aircraft landing impact load; S50, obtaining the influence of the aircraft dynamic load on the tunnel construction settlement through Mohr-Coulomb model simulation analysis; S60, formulating a corresponding construction plan based on the influence of the aircraft dynamic load on the tunnel construction settlement. The present application can solve the construction problem of tunnels under airport runways and control the settlement of airport runways.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel construction, and in particular to a method for controlling micro-settlement of an extra-large-span flat-top straight-wall tunnel under the action of aircraft dynamic loads. Background Art

[0002] There are two major technical challenges when building a tunnel under an airport runway or apron:

[0003] The settlement control requirements are high, but the tunnel has a large span, shallow burial depth, low cover-span ratio, and the strata are mostly silty clay with high water content and poor stability. It is very easy to cause excessive settlement or even landslide accidents during construction.

[0004] The impact of aircraft dynamic loads is significant. The dynamic loads generated by aircraft taxiing, taking off and landing will repeatedly act on the overlying soil of the tunnel, causing the soil to loosen. Before the tunnel support structure is constructed, the load is entirely borne by the advance support or initial support, which is extremely risky. Summary of the Invention

[0005] Based on this, it is necessary to provide a micro-settlement control method for extra-large span flat-top straight-wall tunnels under aircraft dynamic loads to address the high risk of tunnel construction support under dynamic loads.

[0006] To achieve the above objectives, the technical solutions adopted in this application are as follows:

[0007] The present application provides a method for controlling micro-settlement of a large-span flat-top straight-wall tunnel under dynamic load from an aircraft. The method comprises:

[0008] S10, evenly distribute the weight of the aircraft to each wheel and calculate the static load P1 of the aircraft;

[0009] S20, converting the vertical kinetic energy of the aircraft into impact force to obtain the dynamic additional force F, and evenly distributing it to each wheel to calculate the dynamic load P2 of the aircraft;

[0010] S30, adding the static load P1 and the dynamic load P2 to obtain the aircraft landing impact load P3;

[0011] S40, obtaining a distance r from the load application point to the calculation point and a buried depth h of the tunnel, wherein the distance r is directly proportional to the buried depth h, and calculating the settlement S of the tunnel vault using the aircraft landing impact load P3;

[0012] S50, using Mohr-Coulomb model simulation analysis to obtain the impact of aircraft dynamic loads on tunnel construction settlement;

[0013] S60: Develop corresponding construction plans based on the impact of aircraft dynamic loads on tunnel construction settlement.

[0014] In one embodiment, calculating the static load P1 of the aircraft includes:

[0015] The weight M of the aircraft, the number N of the aircraft wheels, and the contact area A between each wheel and the ground are obtained to calculate the static load P1. The static load P1 is expressed as follows:

[0016] .

[0017] In one embodiment, calculating the dynamic load P2 of the aircraft includes:

[0018] Get the vertical descent speed v and gravity acceleration g=9.8m / s at the moment of landing 2 , landing gear buffer distance L, calculate the dynamic additional force F, and the expression formula of the dynamic additional force F is:

[0019] ;

[0020] The dynamic additional force F is evenly distributed to each wheel to obtain the dynamic load P2, and the expression formula of the dynamic load P2 is:

[0021] .

[0022] In one embodiment, the aircraft landing impact load P3 is expressed as follows:

[0023] .

[0024] In one embodiment, calculating the settlement S of the tunnel vault using the aircraft landing impact load includes:

[0025] S401, based on the elastic half-space foundation assumption, obtain the Poisson's ratio u and the elastic modulus E of the soil s , the basic expression formula of the tunnel vault settlement S is obtained;

[0026] S402, establishing a correction coefficient k, obtaining a load action point of the tunnel crown at a depth h of the tunnel, and calculating a relationship between the settlement S of the tunnel crown and the depth h of the tunnel;

[0027] S403, obtaining the span D of the tunnel, and calculating the relationship between the settlement S of the tunnel vault and the span D of the tunnel;

[0028] S404, obtaining the support structure stiffness EI, and calculating the relationship between the settlement S of the tunnel vault and the support structure stiffness EI;

[0029] S405 , combining the effects of soil response, the tunnel span D, and the support structure stiffness EI on the settlement S of the tunnel vault, to obtain a final relationship for the settlement S of the tunnel vault.

[0030] In one embodiment, the final relationship of the settlement S of the tunnel vault is:

[0031] ;

[0032] Where S is the settlement of the tunnel vault caused by the dynamic load of the aircraft, M is the weight of the aircraft, N is the number of aircraft wheels, A is the contact area between each wheel and the ground, v is the vertical descent speed of the aircraft at the moment of landing, g is the acceleration of gravity, L is the landing gear buffer distance, u is the Poisson's ratio of the soil, D is the span of the tunnel, and E is the vertical descent speed of the aircraft at the moment of landing. s is the elastic modulus of the soil, h is the depth of the tunnel, EI is the stiffness of the support structure, k3 is an undetermined constant, is the value of pi, which is 3.14.

[0033] In one embodiment, k3 is derived based on elastic thin plate theory or Pasternak foundation model, and the expression formula of k3 is:

[0034] ;

[0035] Where u is the Poisson's ratio of the soil, is the value of pi, which is 3.14.

[0036] In one embodiment, based on the analysis of the settlement of the tunnel vault caused by aircraft dynamic loads, a closed pipe curtain arrangement is used for advanced support.

[0037] In one embodiment, during the pipe roof jacking process, a micro-shield machine measurement and control intelligent system is used, and lubricating slurry is injected synchronously during the pipe roof jacking process;

[0038] The micro shield machine measurement and control intelligent system includes a laser target plate, a camera and a display screen. The laser target plate is installed on the head of the shield machine. The camera is used to shoot the laser point on the laser target plate and transmit it to the display screen.

[0039] In one embodiment, a step-by-step excavation and support method of ten pilot tunnels is adopted during tunnel construction. After all the pilot tunnels are excavated, the entire tunnel is reinforced with lining.

[0040] Compared with the relevant technologies, the beneficial effects of the present application are as follows: the present application calculates the dynamic load of the aircraft, analyzes the impact of the dynamic load of the aircraft on the settlement of the tunnel construction, and thus selects a suitable support method, simultaneously injects lubricating slurry during the pipe curtain jacking process, and adopts a ten-guide tunnel step-by-step excavation support method, which solves the construction problem of the tunnel under the airport runway and reduces the tunnel settlement. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is a flow chart of the micro-settlement control method for a large-span flat-top straight-wall tunnel under aircraft dynamic loads;

[0043] Figure 2 This is a schematic diagram of the calculation process for the settlement of the tunnel vault in this application;

[0044] Figure 3 Schematic diagram of force node selection for the Mohr-Coulomb model of this application;

[0045] Figure 4 Schematic diagram of the numerical results of surface settlement under static and dynamic loads for this application;

[0046] Figure 5 Surface settlement curves for the two pipe curtain arrangements of closed and non-closed types in this application;

[0047] Figure 6 This is a schematic diagram of the construction structure of step S61 of this application;

[0048] Figure 7 This is a schematic diagram of the construction structure of step S62 of this application;

[0049] Figure 8 This is a schematic diagram of the construction structure of step S63 of this application;

[0050] Figure 9 This is a schematic diagram of the construction structure of step S64 of this application;

[0051] Figure 10 This is a schematic diagram of the construction structure of step S65 of this application;

[0052] Figure 11 This is a schematic diagram of the construction structure of step S66 of this application. DETAILED DESCRIPTION

[0053] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0054] In the description of this application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0055] In addition, if the term "and / or" appears, "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the objects associated with each other are in an "or" relationship. If the terms "first" and "second" appear, these terms are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "multiple" appears, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0056] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connected," "fixed," etc., should be interpreted broadly. For example, these terms may refer to fixed connections, removable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; and internal communication between two components or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0057] In this application, unless otherwise expressly specified or limited, if a first feature is described as being "above" or "below" a second feature, or similar descriptions, this may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is described as being "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is described as being "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0058] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only embodiment.

[0059] Constructing extra-large-span, flat-top, straight-wall tunnels on runways or aprons presents significant construction challenges due to the dynamic loads of aircraft. First, runway settlement control standards are extremely stringent, requiring total settlement to be less than 30mm and a flatness of less than 1‰. However, the tunnel span is large (reaching 23.9m), the burial depth is small (only 5.6m), and the cover-span ratio is only 0.23. Furthermore, the tunnel's flat-top, straight-wall structure is located in a silty clay soil with a high water content and poor stability. Controlling settlement during tunnel construction is extremely difficult, and even the slightest negligence can lead to excessive runway settlement, landslides, or even fatal accidents resulting in aircraft destruction and loss of life. Second, the density of aircraft taxiing, taking off, and landing on the runway is very high, and the tunnel construction process must withstand frequent aircraft dynamic loads. For example, the taxiing load of the largest A380 aircraft reaches 600 tons. Under the repeated action of such huge dynamic loads, the overburden of the tunnel is easily loosened. Moreover, before the tunnel support structure is installed, the entire load is borne by the advance support, or advance support plus initial support, which is extremely risky. It is very difficult to analyze the interaction between aircraft dynamic loads and tunnel excavation. Third, a large Φ970, 232m long pipe curtain is required for advance support around the tunnel. How to control the runway settlement during the construction of the large-diameter pipe curtain and how to ensure the guidance accuracy of the extra-long pipe curtain are technically difficult to achieve and construction control is very difficult.

[0060] See Figure 1As shown, in order to improve the above problems, the embodiment of the present application provides a method for controlling micro-settlement of an extra-large span flat-top straight-wall tunnel under the action of aircraft dynamic load, analyzes the influence of aircraft dynamic load on settlement and structural internal force, ensures the construction accuracy of the pipe curtain, and achieves the control standards of airport runway settlement less than 30mm and flatness less than 1‰.

[0061] Specifically, the control method includes:

[0062] S10: Evenly distribute the weight of the aircraft to each wheel and calculate the static load P1 of the aircraft.

[0063] Specifically, the static load P1 of the aircraft is calculated including:

[0064] Obtain the weight M of the aircraft, the number N of aircraft wheels, and the contact area A of each wheel with the ground to calculate the static load P1. The expression formula of the static load P1 is:

[0065] .

[0066] Where M is the total weight of the aircraft, in kN, N is the number of wheels, in units, and no unit operations are performed during the calculation process. A is the area of ​​contact between each wheel and the ground, in m 2 .

[0067] Understandably, during construction, the maximum dynamic load during a single aircraft dive should be considered. Therefore, the largest aircraft operating at the airport should be considered and the simulation analysis performed using that largest aircraft. Currently, the Airbus A380 is the largest aircraft primarily used for takeoff and landing on central runways at airports, and its takeoff and landing processes have the greatest impact on the tunnel structure. Therefore, in the examples of this application, the Airbus A380 was used as an example to simulate aircraft dynamic loads.

[0068] In step S20, the vertical kinetic energy of the aircraft is converted into an impact force to obtain a dynamic additional force F, which is evenly distributed to each wheel to calculate the dynamic load P2 of the aircraft.

[0069] Specifically, in addition to considering the aircraft's own gravity load, it is also necessary to consider the dynamic load generated by the aircraft during takeoff and landing, especially the dive force generated during its landing, which has the greatest impact on the tunnel's settlement.

[0070] Furthermore, the calculated dynamic load P2 of the aircraft includes:

[0071] Convert the vertical kinetic energy of the aircraft into impact force, kinetic energy , where m=M / g. In the ideal case without considering loss, the kinetic energy Ek is the same as the work done by the dynamic additional force F, that is:

[0072] ;

[0073] The deformation results in the expression formula of the dynamic additional force F:

[0074] .

[0075] Then, the dynamic additional force F is evenly distributed to each wheel to obtain the dynamic load P2 of the aircraft.

[0076] The expression formula of dynamic load P2 is:

[0077] ;

[0078] Where M is the total weight of the aircraft, in kN, v is the vertical descent speed of the aircraft at the moment of landing, in m / s, and g is the acceleration due to gravity, which is calculated as 9.8 m / s. 2 , L is the landing gear buffer distance, unit is m, N is the number of wheels, unit is not used in the calculation process, A is the area of ​​each wheel in contact with the ground, unit is m 2 .

[0079] S30 , adding the static load P1 and the dynamic load P2 to obtain the aircraft landing impact load P3 .

[0080] Specifically, the aircraft landing impact load P3 is the sum of the static load P1 and the dynamic load P2, and is expressed as:

[0081] P3=P1+P2;

[0082] in, , ,but ; Transformed to:

[0083] .

[0084] S40, obtaining the distance r from the load action point to the calculation point and the buried depth h of the tunnel, and , the settlement S of the tunnel vault is calculated using the aircraft landing impact load P3.

[0085] Obtaining aircraft dynamic loads is of great significance to the settlement of tunnel vaults, which facilitates the subsequent construction support and provides strong theoretical support for ensuring the stable operation and support strength of tunnel construction.

[0086] Continue reading Figure 2 As shown, specifically, the calculation process of the tunnel vault settlement S includes:

[0087] S401, based on the elastic half-space foundation assumption, obtain the Poisson's ratio u and the elastic modulus E of the soil s , and the basic expression formula of the tunnel vault settlement S is obtained.

[0088] According to the elastic half-space foundation assumption, when the aircraft landing impact load P3 acts on the tunnel vault, the settlement S of the tunnel vault is:

[0089] .

[0090] Among them, P3 is the aircraft landing impact load, unit kN / m 2 In this application, only the load under unit width is analyzed. In the calculation process, the unit of P3 is changed to kN / m, u is the Poisson's ratio of the soil, and Es is the elastic modulus of the soil, in kN / m. 2 , r is the distance from the aircraft load action point to the calculation point, unit is m, is the value of pi, which is 3.14.

[0091] S402 , establishing a correction coefficient k1 to obtain the relationship between the tunnel crown settlement S and the tunnel burial depth h when the load action point of the tunnel crown is located at the tunnel burial depth h.

[0092] During the actual load analysis, the aircraft is in contact with the ground rather than directly acting on the tunnel vault, so the load is converted into settlement at the buried depth.

[0093] At this time, the load is transferred to the tunnel support structure through the soil, and the distance r needs to be corrected. Assuming that the stress diffusion in the soil is axisymmetric, the distance r from the aircraft load action point to the calculation point is proportional to the burial depth h. ,Right now:

[0094] r=k1h.

[0095] Where k1 is the proportionality coefficient related to the Poisson's ratio u of the soil.

[0096] Substituting into the Boussinesq formula, we get:

[0097] ;

[0098] Among them, P3 is the aircraft landing impact load, unit kN / m 2 In this application, only the load under unit width is analyzed. In the calculation process, the unit of P3 is changed to kN / m, u is the Poisson's ratio of the soil, Es is the elastic modulus of the soil, and the unit is kN / m. 2 , h is the burial depth of the tunnel, unit is m, k1 is the proportional coefficient related to the Poisson's ratio u of the soil, which is a unitless constant.

[0099] S403 , obtaining the span D of the tunnel, and calculating the relationship between the settlement S of the tunnel vault and the span D of the tunnel.

[0100] The tunnel support structure is simplified as an elastic foundation beam. According to the elastic foundation beam theory, the deformation of the tunnel is related to the span D. According to the beam bending theory, the mid-span deflection δ is proportional to the span D. The specific relationship is:

[0101] .

[0102] Where q is the distributed load. Since this is the aircraft landing impact load P3, it is assumed that the equivalent distributed load , substituting into:

[0103] .

[0104] Among them, EI is the support stiffness, unit is kN*m 2 , here we need to consider the soil response. In actual settlement, when the span D increases, the loaded area of ​​the soil increases, resulting in increased settlement. Therefore, settlement is proportional to D, and the correction formula is:

[0105] ;

[0106] Among them, P3 is the aircraft landing impact load, unit kN / m 2 In this application, only the load under the width is analyzed. In the calculation process, P3 is expressed in kN / m, u is the Poisson's ratio of the soil, and D is the span of the tunnel in m. is the pi, which can be taken as 3.14 in the specific calculation process, and Es is the elastic modulus of the soil, in kN / m 2 , h is the depth of the tunnel, unit is m.

[0107] S404: Obtain the support structure stiffness EI and calculate the relationship between the tunnel vault settlement S and the support structure stiffness EI.

[0108] Specifically, the supporting structure is a crucial component of the tunnel structure, and its stiffness (EI) significantly affects the interaction between the soil and the structure under load. To quantify the effect of the supporting structure stiffness on settlement, the supporting structure needs to be simplified as a beam on an elastic foundation.

[0109] The supporting structure is a beam with a uniform cross-section and a bending stiffness of EI. The soil support on the supporting structure is simplified to the Winkler foundation model, that is, the foundation reaction p(x) is proportional to the supporting structure deflection w(x):

[0110] ;

[0111] Where k2 is the foundation reaction modulus (which is the same as the soil elastic modulus E s related).

[0112] The bending behavior of the supporting structure is described by the differential equation of the elastic foundation beam:

[0113] ;

[0114] Where w(x) is the deflection of the beam.

[0115] The tunnel is calculated as a simply supported beam. For symmetrical loads, the deflection at mid-span is maximum and the boundary conditions are:

[0116] Beam simply supported at both ends: , .

[0117] Solve the differential equation by Fourier transform or characteristic function method to obtain the expression of mid-span deflection:

[0118] .

[0119] Winkler foundation modulus k2 and soil elastic modulus E s It is related to the geometric parameters of the tunnel. Through dimensional analysis and elastic half-space theory, it can be assumed that , then k2 and E s / D is directly proportional.

[0120] Will Substituting into the deflection formula, we get:

[0121] .

[0122] S405 , combining the effects of soil response, tunnel span D, and support structure stiffness EI on the settlement S of the tunnel crown, a final relationship for the settlement S of the tunnel crown is obtained.

[0123] Further sorting, introducing dimensionless parameters (k3 is a constant to be determined), the influence of the support structure stiffness is expressed as:

[0124] ;

[0125] The correction effect of the support structure stiffness EI is reflected in the additional term in the denominator , the final settlement formula is:

[0126] ;

[0127] Where: The unit of aircraft landing impact load P3 is kN / m 2 In this application, only the load under unit width is analyzed. In the calculation process, the unit of P3 is changed to kN / m, u is the Poisson's ratio of the soil, and Es is the elastic modulus of the soil, in kN / m. 2 , h is the tunnel depth, unit is m, D is the tunnel width, unit is m, EI is the support stiffness kN*m2 .

[0128] The expression of k3 is derived based on the elastic thin plate theory or the Pasternak foundation model:

[0129] .

[0130] Combined with the above formula, the final relationship for the tunnel vault settlement S is:

[0131] ;

[0132] Where S is the settlement of the tunnel vault caused by the dynamic load of the aircraft, M is the weight of the aircraft, N is the number of aircraft wheels, A is the contact area between each wheel and the ground, v is the vertical descent speed of the aircraft at the moment of landing, g is the acceleration of gravity, L is the landing gear buffer distance, u is the Poisson's ratio of the soil, D is the span of the tunnel, and E is the vertical descent speed of the aircraft at the moment of landing. s is the elastic modulus of the soil, h is the burial depth of the tunnel, and EI is the stiffness of the support structure.

[0133] In addition, it should be noted that in the above formula In summary, the above method accurately calculates the surface settlement of the tunnel vault under the action of aircraft dynamic load, providing a basis for the design of the corresponding pipe roof stiffness and support system for subsequent settlement control.

[0134] S50, through Mohr-Coulomb model simulation analysis, obtain the impact of aircraft dynamic load on tunnel construction settlement.

[0135] Continue reading Figure 3 and Figure 4 As shown in the figure, a dynamic finite element model was constructed using the Mohr-Coulomb model and Rayleigh damping. Forced nodes on the model were selected and the static and dynamic loads from the aircraft were applied to the simulated nodes to obtain the model's surface settlement values. As can be seen from the figure, the ground surface exhibits some settlement under both static and dynamic loads, but the dynamic load causes a slightly larger vertical displacement response in the tunnel.

[0136] Based on the above, the following conclusions are drawn:

[0137] (1) During the landing process, the wheels of the aircraft have an impact on the pavement, which increases the effect of the aircraft load on the pavement.

[0138] (2) The maximum displacement curves of the tunnel under the two loads are basically the same. The overall trend is that the settlement in the middle of the tunnel is larger and the settlement on both sides of the tunnel is smaller. The dynamic load of the aircraft significantly increases the surface settlement of the tunnel, especially in the middle area of ​​the tunnel.

[0139] S60: Develop corresponding construction plans based on the impact of aircraft dynamic loads on tunnel construction settlement.

[0140] Continue reading Figure 5 As shown, specifically, based on the analysis of the settlement caused by aircraft dynamic loads on the tunnel vault, this application studies the reasonable layout of pipe curtain advance support to overcome the settlement effect caused by aircraft dynamic loads. In the test, two pipe curtain layout methods, closed and non-closed, were compared, and other test conditions remained unchanged. The test results are shown in the figure. The final settlement curve shows a pattern of larger settlement in the middle and smaller settlement on both sides. The settlement curve of the closed pipe curtain is relatively flat and wide, and the settlement of the edge measuring points accounts for about 50% of the maximum settlement value. In contrast, the settlement curve of the non-closed pipe curtain is relatively narrow and long, and the settlement of the edge measuring points accounts for 55% of the maximum settlement value. Under the two layout methods, the maximum surface settlement is 0.6mm and 0.9mm respectively. The surface settlement of the non-closed pipe curtain is about 50% higher than that of the closed pipe curtain. Therefore, it is recommended to adopt a closed pipe curtain layout scheme in actual engineering to better control settlement and reduce the impact of aircraft dynamic loads on settlement and structural internal forces.

[0141] Furthermore, precise control of the tunnel roof's jacking direction helps improve the stability of the tunnel roof structure and enhance its support strength, effectively reducing the impact of aircraft dynamic loads on tunnel construction settlement. Therefore, this study employed an intelligent measurement and control system for a micro-shield machine during the tunnel roof jacking process, while also simultaneously injecting lubricating slurry.

[0142] Specifically, when the shield machine is advancing the pipe curtain, the laser system directly illuminates the direction of the steel pipe's advancement, while simultaneously displaying a light spot on the laser target disk. The operator uses the laser spot image captured by the camera on the display screen to determine any deviation in the advancement direction and automatically adjusts the deviation through fine-tuning. This process effectively ensures the accuracy of the pipe curtain construction, keeping vertical and horizontal deviations within 12 mm, meeting the required standards.

[0143] During the jacking process, slurry must be injected continuously and steadily during the jacking operation, which can not only effectively prevent the hole wall from collapsing and sinking, but also play a role in lubrication and reducing resistance.

[0144] Furthermore, during tunnel construction, grouting was used to fill the gaps around the pipe curtain, allowing the structure to form a cohesive whole. Deep hole pre-grouting was also used to reinforce the surrounding soil, thereby increasing the rigidity of the pipe curtain. Under the protection of the pipe curtain, a phased excavation and support method involving ten pilot tunnels was employed.

[0145] Specifically, the ten-pilot tunnel excavation and support method divides the large section into ten smaller pilot tunnels, which are excavated and supported one by one, thereby effectively reducing the disturbance of large-scale excavation to the surrounding strata.

[0146] For ease of understanding, the present embodiment of the invention sequentially numbers each pilot tunnel along the transverse direction of the large cross section, and uses serial numbers to refer to and explain during the construction process. The specific process of the ten-pilot tunnel step-by-step excavation and support method is as follows:

[0147] See Figure 6 As shown, S61, the tunnel excavation construction first carries out the excavation of pilot tunnel 1 and pilot tunnel 2. Pilot tunnel 1 is excavated using the step method. During the excavation process, the core soil of the face is retained as a temporary support to prevent the face from becoming unstable. The advance of each excavation does not exceed the spacing of one steel frame. After the excavation is completed, the initial spraying of concrete is immediately carried out to form the initial support to prevent large settlements. After ensuring that the support of the upper pilot tunnel is stable, the excavation of the lower pilot tunnel can be carried out. The excavation of pilot tunnel 2 begins after the upper pilot tunnel is excavated to about 4m. After the excavation is completed, the initial support construction of the invert arch is immediately carried out and connected with the initial support of the side wall to form a closed bearing structure. During the tunnel excavation process, deep hole grouting is carried out on the soil every approximately 15m to reinforce the soil around the face to prevent instability or avoid the occurrence of large settlements.

[0148] See Figure 7 As shown, in S62, after the initial support and secondary lining of pilot tunnels 1 and 2 are completed, pilot tunnels 9 and 10 are excavated. The excavation steps of pilot tunnels 9 and 10 are the same as those of pilot tunnels 1 and 2. Pilot tunnel 9 corresponds to the process of pilot tunnel 1, and pilot tunnel 10 corresponds to the process of pilot tunnel 2.

[0149] See Figure 8 As shown, in S63, after pilot tunnels 9 and 10 are initially supported and secondary lining is completed, pilot tunnels 5 and 6 are excavated. The excavation steps for pilot tunnels 5 and 6 are the same as those for pilot tunnels 1 and 2. Pilot tunnel 5 follows the same process as pilot tunnel 1, while pilot tunnel 6 follows the same process as pilot tunnel 2.

[0150] See Figure 9 As shown in step S64, after pilot tunnels 5 and 6 are initially supported and secondary lining is completed, pilot tunnels 3 and 4 are excavated, following the same excavation steps as step S61. The temporary supports installed in pilot tunnels 1 and 2 are mechanically removed. After removal, the rigidity of the initial supports is reinforced, and steel arches are constructed. Real-time monitoring of arch and ground settlement is performed, and if settlement is excessive, support measures are promptly strengthened.

[0151] See Figure 10 As shown in step S65, after the excavation of pilot tunnels 3 and 4 is completed, an inverted arch is constructed to close the ring, the left tunnel is excavated, and secondary lining backfill grouting is performed. Pilot tunnels 7 and 8 are excavated using the same process as step S61.

[0152] See Figure 11As shown, after the excavation of S66, pilot tunnels 7 and 8 is completed, an invert arch is constructed to close the ring. After the dark excavation of the right tunnel is completed, the secondary lining backfill grouting is carried out. After all the excavation is completed, the overall lining is reinforced.

[0153] Through this construction method, a rational pilot tunnel excavation sequence, segmented support design, and deep-hole grouting reinforcement measures effectively prevented tunnel face instability and excessive settlement during the construction of this ultra-shallow, extra-large-span, flat-top, straight-wall tunnel beneath the runway. A strategy combining bench excavation with real-time settlement monitoring ensured the stability of the support system at each stage. These two measures effectively reduced the impact of aircraft dynamic loads on tunnel construction settlement, ensuring the safety and stability of the tunnel under the runway during construction and operation.

[0154] Finally, during the specific construction process, through measurement and analysis of the tunnel ground settlement, the settlement of the airport runway was less than 30mm and the flatness was less than 1‰. This application effectively improved the impact of aircraft dynamic loads on tunnel settlement.

[0155] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for controlling micro-settlement of a large-span flat-top straight-wall tunnel under aircraft dynamic load, characterized by: The control method includes: S10, evenly distribute the weight of the aircraft to each wheel and calculate the static load P1 of the aircraft; S20, converting the vertical kinetic energy of the aircraft into impact force to obtain the dynamic additional force F, and evenly distributing it to each wheel to calculate the dynamic load P2 of the aircraft; S30, adding the static load P1 and the dynamic load P2 to obtain the aircraft landing impact load P3; S40, obtaining a distance r from the load application point to the calculation point and a buried depth h of the tunnel, wherein the distance r is directly proportional to the buried depth h, and calculating the settlement S of the tunnel vault using the aircraft landing impact load P3; S50, using Mohr-Coulomb model simulation analysis to obtain the impact of aircraft dynamic loads on tunnel construction settlement; S60: Develop a corresponding construction plan based on the impact of aircraft dynamic loads on tunnel construction settlement; The calculation of the tunnel vault settlement S by the aircraft landing impact load includes: S401, based on the elastic half-space foundation assumption, obtain the Poisson's ratio u and the elastic modulus E of the soil s , the basic expression formula of the tunnel vault settlement S is obtained; S402, establishing a correction coefficient k, obtaining a load action point of the tunnel crown at a depth h of the tunnel, and calculating a relationship between the settlement S of the tunnel crown and the depth h of the tunnel; S403, obtaining the span D of the tunnel, and calculating the relationship between the settlement S of the tunnel vault and the span D of the tunnel; S404, obtaining the support structure stiffness EI, and calculating the relationship between the settlement S of the tunnel vault and the support structure stiffness EI; S405, combining the effects of soil response, the tunnel span D, and the support structure stiffness EI on the settlement S of the tunnel vault, to obtain a final relationship for the settlement S of the tunnel vault; The final relational expression for the settlement S of the tunnel vault is: ； Where S is the settlement of the tunnel vault caused by the dynamic load of the aircraft, M is the weight of the aircraft, N is the number of aircraft wheels, A is the contact area between each wheel and the ground, v is the vertical descent speed of the aircraft at the moment of landing, g is the acceleration of gravity, L is the landing gear buffer distance, u is the Poisson's ratio of the soil, D is the span of the tunnel, and E is the vertical descent speed of the aircraft at the moment of landing. s is the elastic modulus of the soil, h is the depth of the tunnel, EI is the stiffness of the support structure, k3 is an undetermined constant, is the value of pi, which is 3.14; The k3 is derived based on the elastic thin plate theory or the Pasternak foundation model. The expression formula of the k3 is: ； Where u is the Poisson's ratio of the soil, is the value of pi, which is 3.

14.

2. The control method according to claim 1, characterized in that: The static load P1 of the aircraft obtained by calculation includes: The weight M of the aircraft, the number N of the aircraft wheels, and the contact area A between each wheel and the ground are obtained to calculate the static load P1. The static load P1 is expressed as follows: 。 3. The control method according to claim 2, characterized in that: The calculated dynamic load P2 of the aircraft includes: Get the vertical descent speed v at the moment of landing, the acceleration of gravity g=9.8m / s 2 , landing gear buffer distance L, calculate the dynamic additional force F, and the expression formula of the dynamic additional force F is: ； The dynamic additional force F is evenly distributed to each wheel to obtain the dynamic load P2, and the expression formula of the dynamic load P2 is: 。 4. The control method according to claim 3, characterized in that: The expression formula of the aircraft landing impact load P3 is: 。 5. The control method according to claim 1, characterized in that: Based on the analysis of the settlement of the tunnel vault caused by aircraft dynamic load, a closed pipe curtain arrangement is adopted for advanced support.

6. The control method according to claim 5, characterized in that: During the pipe roof jacking process, the micro shield machine measurement and control intelligent system is used, and lubricating slurry is injected synchronously during the pipe roof jacking process; The micro shield machine measurement and control intelligent system includes a laser target plate, a camera and a display screen. The laser target plate is installed on the head of the shield machine. The camera is used to shoot the laser point on the laser target plate and transmit it to the display screen.

7. The control method according to claim 5, characterized in that: During tunnel construction, a step-by-step excavation and support method of ten pilot tunnels was adopted. After all the pilot tunnels were excavated, the entire tunnel was reinforced with lining.

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