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

Abstract

The invention relates to a micro-settlement control method for an extra-large-span flat-top straight-wall tunnel under the dynamic load action of an aircraft, and relates to the technical field of tunnel construction. The control method comprises the following steps: S10, uniformly spreading the weight of the airplane to each airplane wheel, and calculating to obtain a static load P1 of the airplane; s20, vertical kinetic energy of the aircraft is converted into impact force, dynamic additional force F is obtained and evenly spread to each aircraft wheel, and the dynamic load P2 of the aircraft is obtained through calculation; s30, adding the static load P1 and the dynamic load P2 to obtain an aircraft landing impact load P3; s40, the distance r from the load acting point to the calculation point and the burial depth h of the tunnel are obtained, and settlement S of the tunnel vault is calculated through the aircraft landing impact load; s50, through Moire-Coulomb model simulation analysis, the influence of the aircraft dynamic load on tunnel construction settlement is obtained; and S60, making a corresponding construction scheme according to the influence of the airplane dynamic load on tunnel construction settlement. The construction problem of undercrossing the airport runway by the tunnel can be solved, and settlement of the airport runway is controlled.

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 a super-large-span flat-top straight-wall tunnel under the action of aircraft dynamic load. Background Art

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

[0003] The impact of aircraft dynamic loads is significant. The dynamic loads generated when the aircraft taxis, takes off and lands 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

[0004] Based on this, it is necessary to provide a method for controlling micro-settlement of extra-large-span flat-top straight-wall tunnels under aircraft dynamic loads in order to address the high risk of tunnel construction support under dynamic loads.

[0005] To achieve the above objectives, the technical solutions adopted in this application are as follows: The present application embodiment provides a method for controlling micro-settlement of a large-span flat-top straight-wall tunnel under the action of aircraft dynamic loads, the control method comprising: S10, distribute the weight of the aircraft to each wheel and calculate the static load P1 of the aircraft; S20, convert the vertical kinetic energy of the aircraft into impact force, obtain the dynamic additional force F, and evenly distribute 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 action point to the calculation point and a buried depth h of the tunnel, wherein the distance r is proportional to the buried depth h, and calculating the settlement S of the tunnel vault by the aircraft landing impact load P3; S50, through Mohr-Coulomb model simulation analysis, obtain the impact of aircraft dynamic load on tunnel construction settlement; S60, formulate corresponding construction plan based on the impact of aircraft dynamic load on tunnel construction settlement.

[0006] In one embodiment, the calculation of the static load P1 of the aircraft 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, and the expression formula of the static load P1 is: .

[0007] In one embodiment, the calculation of the dynamic load P2 of the aircraft includes: 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: ; 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: .

[0008] In one embodiment, the aircraft landing impact load P3 is expressed as: .

[0009] In one embodiment, the calculating the settlement S of the tunnel vault by the aircraft landing impact load comprises: S401, based on the elastic half-space foundation assumption, obtain the Poisson's ratio u and elastic modulus E of the soil s , the basic expression formula of the settlement S of the tunnel vault is obtained; S402, setting a correction coefficient k, obtaining a load action point of the tunnel vault at a buried depth h of the tunnel, and calculating a relationship between the settlement S of the tunnel vault and the buried 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 stiffness EI of the supporting structure, and calculating the relationship between the settlement S of the tunnel vault and the stiffness EI of the supporting structure; S405, combining the influence of soil response, the span D of the tunnel and the stiffness EI of the supporting structure on the settlement S of the tunnel vault, obtaining a final relational expression for the settlement S of the tunnel vault.

[0010] In one embodiment, the final relational expression for the settlement S of the tunnel vault is: ; Among them, 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, E 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 buried 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.

[0011] In one embodiment, k3 is derived based on elastic thin plate theory or Pasternak foundation model, and the expression formula of k3 is: ; Where u is the Poisson's ratio of the soil, is the value of pi, which is 3.14.

[0012] In one of the embodiments, based on the settlement analysis of the tunnel vault caused by the dynamic load of the aircraft, a closed pipe curtain arrangement is used for advanced support.

[0013] In one of the embodiments, 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; 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.

[0014] In one of the embodiments, 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 lining is reinforced as a whole.

[0015] Compared with the related 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 settlement of the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0017] Figure 1 This is a flow chart of a method for controlling micro-settlement of a super-large-span flat-top straight-wall tunnel under the action of aircraft dynamic loads in this application; Figure 2 This is a schematic diagram of the calculation process of the settlement of the tunnel vault in this application; Figure 3 A schematic diagram of force node selection for the Mohr-Coulomb model of this application; Figure 4Schematic diagram of numerical results of ground settlement under static and dynamic loads for this application; Figure 5 The surface settlement curves of the two types of pipe curtain arrangements, closed type and non-closed type, for this application; Figure 6 This is a schematic diagram of the construction structure of step S61 of this application; Figure 7 This is a schematic diagram of the construction structure of step S62 of this application; Figure 8 This is a schematic diagram of the construction structure of step S63 of this application; Fig. 9 This is a schematic diagram of the construction structure of step S64 of this application; Fig.10 This is a schematic diagram of the construction structure of step S65 of this application; Fig.11 This is a schematic diagram of the construction structure of step S66 of this application. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0019] In the description of the present 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 the present 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 the present application.

[0020] 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: 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 before and after 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.

[0021] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0022] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it 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. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0023] 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 a central 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 a central element at the same time. 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 implementation method.

[0024] The construction of a large-span flat-top straight-wall tunnel on an airport runway or apron is very challenging due to the dynamic load of the aircraft. First, the settlement control standard of the airport runway is extremely high, with a total settlement requirement of less than 30 mm and a flatness requirement of less than 1‰. However, the tunnel has a large span (reaching 23.9 m), a small burial depth (only 5.6 m), and a span-cover ratio of only 0.23. In addition, the tunnel has a flat-top straight-wall structure, and the stratum is silty clay with a high water content and poor stability. The settlement control during the tunnel construction process is extremely difficult, and any carelessness will lead to excessive runway settlement, landslides, and even major accidents such as aircraft destruction and death. Second, the density of aircraft taxiing, taking off and landing on the runway is very high, and the tunnel construction process has to withstand frequent aircraft dynamic loads. For example, the largest A380 aircraft taxiing load is 600 tons. Under the repeated action of such huge dynamic loads, the overburden of the tunnel is easy to loosen, and all loads are borne by advance support, or advance support + initial support before the tunnel support structure is constructed. The risk is extremely high, and it is very difficult to analyze the interaction between aircraft dynamic loads and tunnel excavation. Third, a large pipe curtain with a diameter of 970 and a length of 232m is required for advance support around the tunnel. How to control the settlement of the runway 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.

[0025] See also Figure 1 As shown, in order to improve the above-mentioned problems, an embodiment of the present application provides a method for controlling micro-settlement of a super-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 standard of airport runway settlement less than 30 mm and flatness less than 1‰.

[0026] Specifically, the control method includes: S10, evenly distribute the weight of the aircraft to each wheel, and calculate the static load P1 of the aircraft.

[0027] Specifically, the static load P1 of the aircraft is calculated including: Obtain the weight M of the aircraft, the number N of aircraft wheels, and the contact area A between each wheel and the ground, and calculate the static load P1. The expression formula of the static load P1 is: .

[0028] 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 .

[0029] It is understandable that when carrying out construction, the maximum dynamic load during a single aircraft dive should be considered, and the largest aircraft model operating at the airport should be considered, and the simulation analysis should be carried out based on the largest aircraft model. At present, among the large passenger aircraft that mainly take off and land on the central runway of each airport, the largest aircraft model is the Airbus A380, which has the greatest impact on the tunnel structure during take-off and landing. Therefore, in the embodiment of the present application, the simulation technology of aircraft dynamic load can be studied by taking the Airbus A380 as an example.

[0030] S20, convert the vertical kinetic energy of the aircraft into impact force, obtain the dynamic additional force F, and evenly distribute it to each wheel, and calculate the dynamic load P2 of the aircraft.

[0031] 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 settlement of the tunnel.

[0032] Furthermore, the calculated dynamic load P2 of the aircraft includes: Convert the vertical kinetic energy of the aircraft into impact force, kinetic energy , where m=M / g. In the ideal case where loss is not considered, the kinetic energy Ek is the same as the work done by the dynamic additional force F, that is: ; The deformation results in the expression formula of dynamic additional force F: .

[0033] Then, the dynamic additional force F is evenly distributed to each wheel to obtain the dynamic load P2 of the aircraft.

[0034] The expression formula of dynamic load P2 is: ; 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 of gravity. The value of the calculation process is 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 .

[0035] S30, adding the static load P1 and the dynamic load P2 to obtain the aircraft landing impact load P3.

[0036] Specifically, the aircraft landing impact load P3 is the sum of the static load P1 and the dynamic load P2, and the expression is: P3=P1+P2; in, , ,but ; Deformation gives: .

[0037] 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 crown is calculated using the aircraft landing impact load P3.

[0038] Obtaining aircraft dynamic loads is of great significance to the settlement of the tunnel vault, which is convenient for the later construction support and provides a strong theoretical support for ensuring the steady operation and support strength of the tunnel construction.

[0039] Continue reading Figure 2 As shown, specifically, the calculation process of the settlement S of the tunnel vault includes: S401, based on the elastic half-space foundation assumption, obtain the Poisson's ratio u and elastic modulus E of the soil s , and the basic expression formula of the settlement S of the tunnel vault is obtained.

[0040] 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: .

[0041] 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, in m, is the value of pi, which is 3.14.

[0042] S402, setting a correction coefficient k1, obtaining the load action point of the tunnel crown at the buried depth h of the tunnel, and calculating the relationship between the settlement S of the tunnel crown and the buried depth h of the tunnel.

[0043] In the actual force analysis process, the aircraft is in contact with the ground instead of directly acting on the tunnel vault, so the load is converted into settlement at the buried depth.

[0044] At this time, the load is transmitted 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 point to the calculation point is proportional to the burial depth h. ,Right now: r=k1h.

[0045] Among them, k1 is the proportionality coefficient related to the Poisson's ratio u of the soil.

[0046] Substituting into the Boussinesq formula, we get: ; 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.

[0047] S403, obtaining the span D of the tunnel, and calculating the relationship between the settlement S of the tunnel crown and the span D of the tunnel.

[0048] 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: .

[0049] 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: .

[0050] Among them, EI is the support stiffness, unit kN*m 2 , here we need to combine the soil response. In actual settlement, when the span D increases, the load area of ​​the soil increases, resulting in increased settlement. Therefore, settlement is proportional to D, and the correction formula is: ; 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 in kN / m, u is the Poisson's ratio of the soil, and D is the span of the tunnel in m. is the circumference of a circle, 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 burial depth of the tunnel, in meters.

[0051] S404, obtaining the stiffness EI of the supporting structure, and calculating the relationship between the settlement S of the tunnel vault and the stiffness EI of the supporting structure.

[0052] Specifically, the supporting structure is an important part of the tunnel structure, and its stiffness EI will significantly affect the interaction between the soil and the structure under load. In order to quantify the influence of the supporting structure stiffness on the settlement, the supporting structure needs to be simplified as a beam on an elastic foundation.

[0053] The supporting structure is a beam with uniform cross-section and bending stiffness EI. The supporting effect of soil on the supporting structure is simplified to the Winkler foundation model, that is, the foundation reaction force p(x) is proportional to the deflection w(x) of the supporting structure: ; Where k2 is the foundation reaction modulus (which is similar to the soil elastic modulus E s related).

[0054] The bending behavior of the supporting structure is described by the differential equation of the elastic foundation beam: ; Where w(x) is the deflection of the beam.

[0055] The tunnel is calculated as a simply supported beam. For symmetrical loads, the mid-span deflection is the largest and the boundary conditions are: The beam is simply supported at both ends: , .

[0056] Solving the differential equation by Fourier transform or characteristic function method, we can get the expression of mid-span deflection: .

[0057] 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.

[0058] Will Substituting into the deflection formula, we get: .

[0059] S405, combining the influence of soil response, tunnel span D and support structure stiffness EI on the settlement S of the tunnel crown, a final relational expression for the settlement S of the tunnel crown is obtained.

[0060] Further sorting, introducing dimensionless parameters (k3 is a constant to be determined), and the influence of the support structure stiffness is expressed as: ; The correction effect of the support structure stiffness EI is reflected in the additional term in the denominator , the final settlement formula is: ; 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*m 2 .

[0061] The expression of k3 is derived based on the elastic thin plate theory or the Pasternak foundation model: .

[0062] Combined with the above formula, the final relationship of the settlement S of the tunnel vault is: ; Among them, 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, E 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 supporting structure.

[0063] In addition, it should be noted that in the above formula In summary, the above method provides a basis for designing the corresponding pipe curtain stiffness and support system for subsequent settlement control by accurately calculating the surface settlement of the tunnel vault under the dynamic load of the aircraft.

[0064] S50, through the Mohr-Coulomb model simulation analysis, the influence of aircraft dynamic load on tunnel construction settlement is obtained.

[0065] Continue reading Figure 3 and Figure 4 As shown in the figure, the dynamic finite element model is constructed by using the Mohr-Coulomb model and Rayleigh damping. The force nodes on the model are selected, and the static load and dynamic load of the aircraft are respectively applied to the simulation nodes to obtain the surface settlement value of the model. It can be seen from the figure that under the action of static load and dynamic load, the surface shows a certain settlement, but the vertical displacement response of the tunnel caused by the dynamic load is slightly larger.

[0066] Based on the above content, the following conclusions are drawn: (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.

[0067] (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.

[0068] S60, formulate corresponding construction plan based on the impact of aircraft dynamic load on tunnel construction settlement.

[0069] Continue reading Figure 5 As shown, specifically, according to the settlement analysis of the tunnel vault caused by the dynamic load of the aircraft, this application studies the reasonable layout of the pipe curtain advance support to overcome the settlement effect caused by the dynamic load of the aircraft. In the test, the closed and non-closed pipe curtain layouts were compared, and other test conditions remained unchanged. The test results are shown in the figure. The final settlement curve shows a rule that the settlement is larger in the middle and smaller 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 settlement of the ground surface is 0.6mm and 0.9mm respectively, and 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 the closed pipe curtain layout scheme in actual engineering to better control the settlement and reduce the influence of aircraft dynamic load on settlement and structural internal force.

[0070] Furthermore, precise control of the pipe curtain jacking direction helps to improve the stability of the pipe curtain structure and enhance the support strength, thereby effectively reducing the impact of aircraft dynamic loads on tunnel construction settlement. Therefore, this study adopted a micro-shield machine measurement and control intelligent system during the pipe curtain jacking process and simultaneously injected lubricating slurry.

[0071] Specifically, when the shield machine is performing pipe curtain jacking operations, the laser system will directly illuminate the jacking direction of the steel pipe and display the light spot on the laser target plate. The operator determines the deviation of the jacking direction based on the laser point image captured by the camera on the display screen and corrects it through automatic fine-tuning. This process effectively ensures the accuracy of pipe curtain construction, so that the deviation of up, down, left and right is controlled within 12mm, meeting the requirements.

[0072] 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.

[0073] Furthermore, during the tunnel construction process, the gaps around the pipe curtain are filled with grouting technology to make the pipe curtain structure form a whole, and the soil around the tunnel is reinforced through deep hole pre-grouting technology, thereby achieving the purpose of increasing the stiffness of the pipe curtain. Under the protection of the pipe curtain, a ten-pilot tunnel step-by-step excavation support method is adopted.

[0074] Specifically, the ten-pilot tunnel step-by-step 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.

[0075] For ease of understanding, the present embodiment of the invention sequentially numbers each pilot tunnel along 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: See also Figure 6 As shown, S61, the tunnel excavation construction first excavates the pilot tunnel 1 and the pilot tunnel 2. The pilot tunnel 1 is excavated by 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 a steel frame. After the excavation is completed, the initial spraying of concrete is immediately carried out to form an initial support to prevent a large settlement. After ensuring that the upper pilot tunnel support is stable, the excavation of the lower pilot tunnel can be carried out. The excavation of the pilot tunnel 2 starts after the upper pilot tunnel is excavated to about 4m. After the excavation is completed, the initial support construction of the invert 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 about 15m to reinforce the soil around the face to prevent instability or avoid the occurrence of large settlement.

[0076] See also Figure 7 As shown, S62, after the initial support and secondary lining of pilot tunnels 1 and 2 are completed, pilot tunnels 9 and 10 are excavated, and the excavation steps of pilot tunnels 9 and 10 are the same as those of pilot tunnels 1 and 2. Among them, pilot tunnel 9 corresponds to the process of pilot tunnel 1, and pilot tunnel 10 corresponds to the process of pilot tunnel 2.

[0077] See also Figure 8 As shown, S63, after the pilot tunnels 9 and 10 are initially supported and the secondary lining is completed, the pilot tunnels 5 and 6 are excavated. The excavation of the pilot tunnels 5 and 6 is the same as that of the pilot tunnels 1 and 2. The pilot tunnel 5 corresponds to the process of the pilot tunnel 1, and the pilot tunnel 6 corresponds to the process of the pilot tunnel 2.

[0078] See also Fig. 9 As shown, in step S64, after the initial support and secondary lining of pilot tunnels 5 and 6 are completed, pilot tunnels 3 and 4 are excavated, and the excavation steps are the same as step S61. The temporary supports applied to pilot tunnels 1 and 2 are broken by mechanical tools, and after breaking, the rigidity of the initial support is strengthened and a steel arch frame is applied. The settlement of the arch and the ground surface is monitored in real time. If the settlement value is too large, the support measures should be strengthened in time.

[0079] See also Fig.10As shown, in step S65, after the excavation of pilot tunnels 3 and 4 is completed, an invert is constructed to close the ring, the dark excavation of the left tunnel is completed, and secondary lining backfilling and grouting are performed. Pilot tunnels 7 and 8 are excavated using the same process as step S61.

[0080] See also Fig.11 As shown, after the excavation of S66, pilot tunnels 7 and 8 is completed, an invert arch is constructed to close the ring, the dark excavation of the right tunnel is completed, and the secondary lining backfill grouting is carried out. After all the excavation is completed, the overall lining is reinforced.

[0081] Through the above construction method, during the construction of the ultra-shallow buried extra-large span flat-top straight wall tunnel under the runway, the instability of the tunnel face and excessive settlement were effectively prevented through reasonable pilot tunnel excavation sequence, segmented support design and deep hole grouting reinforcement measures; the strategy of combining step excavation with real-time settlement monitoring was adopted to ensure the stability of the support system at each stage. The 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.

[0082] Finally, during the specific construction process, through the 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 the settlement of the tunnel.

[0083] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0084] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for controlling micro-settlement of a large-span flat-top straight-wall tunnel under aircraft dynamic load, characterized in that: The control method comprises: S10, distribute the weight of the aircraft to each wheel and calculate the static load P1 of the aircraft; S20, convert the vertical kinetic energy of the aircraft into impact force, obtain the dynamic additional force F, and evenly distribute 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 action point to the calculation point and a buried depth h of the tunnel, wherein the distance r is proportional to the buried depth h, and calculating the settlement S of the tunnel vault by the aircraft landing impact load P3; S50, through Mohr-Coulomb model simulation analysis, obtain the impact of aircraft dynamic load on tunnel construction settlement; S60, formulate corresponding construction plan based on the impact of aircraft dynamic load on tunnel construction settlement.

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, and the expression formula of the static load P1 is: 。 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 of the aircraft at the moment of landing, the gravity acceleration 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: The calculation of the settlement S of the tunnel vault by the aircraft landing impact load comprises: S401, based on the elastic half-space foundation assumption, obtain the Poisson's ratio u and elastic modulus E of the soil s , the basic expression formula of the settlement S of the tunnel vault is obtained; S402, setting a correction coefficient k, obtaining a load action point of the tunnel vault at a buried depth h of the tunnel, and calculating a relationship between the settlement S of the tunnel vault and the buried 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 stiffness EI of the supporting structure, and calculating the relationship between the settlement S of the tunnel vault and the stiffness EI of the supporting structure; S405, combining the influence of soil response, the span D of the tunnel and the stiffness EI of the supporting structure on the settlement S of the tunnel vault, obtaining a final relational expression for the settlement S of the tunnel vault.

6. The control method according to claim 5, characterized in that: The final relational expression for the settlement S of the tunnel vault is: ； Among them, 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, E 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 buried 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.

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7. The control method according to claim 6, characterized in that: The k3 is derived based on the elastic thin plate theory or the Pasternak foundation model, and the expression formula of k3 is: ； Where u is the Poisson's ratio of the soil, is the value of pi, which is 3.

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8. The control method according to claim 1, characterized in that: According to the analysis of the settlement of the tunnel vault caused by aircraft dynamic load, a closed pipe curtain arrangement is adopted for advanced support.

9. The control method according to claim 8, 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.

10. The control method according to claim 8, characterized in that: During tunnel construction, a step-by-step excavation and support method of ten pilot tunnels is adopted. After all the pilot tunnels are excavated, the lining is reinforced as a whole.

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