Composite stratum tunnel construction earth surface three-dimensional settlement prediction method

Abstract

The invention discloses a composite stratum tunnel construction earth surface three-dimensional settlement prediction method, which comprises the following steps: constructing a two-dimensional earth surface settlement formula to express the relationship between the earth surface settlement amount and the tunnel radius and the settling tank width; obtaining a relation curve graph under the condition of different tunnel radiuses and tunnel burial depths, constructing a relation model, and fitting the relation model; and predicting the width of the settling tank under different tunnel burial depths in the composite stratum by using the fitted relation model, and then introducing a space deformation factor to calculate the three-dimensional ground settlement under different tunnel radiuses and tunnel burial depths in the composite stratum. The invention provides an earth surface three-dimensional settlement rapid prediction method which can comprehensively consider complex stratum conditions, construction conditions and tunnel excavation disturbance transfer characteristics so as to realize timely prediction of a tunnel construction stratum disturbance transfer effect. And the problems of inconvenience in correlation and great difficulty in understanding and using by construction technicians in the conventional technical means can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction, and specifically to a method for predicting three-dimensional surface settlement during tunnel construction in composite strata. Background Technology

[0002] With continuous economic development, tunnel boring technology has become increasingly mature, even reaching international first-class levels in some areas. Major cities have successively launched subway tunnel construction projects, which has brought new vitality to the development of these cities, but also many challenges. The urban surface contains a large number of existing buildings, and tunnel construction can trigger surface subsidence, leading to uneven settlement of the superstructure. If not addressed promptly, this can cause surface cracking. Therefore, timely prediction of surface subsidence before tunnel construction can reduce subsequent remedial costs and mitigate the risk of economic and property losses.

[0003] Existing methods for predicting surface settlement during tunnel excavation mainly include theoretical analysis, numerical simulation, neural networks, or a combination of these methods. In summary, they have the following two main drawbacks: (1) The theoretical analysis failed to comprehensively consider the soil parameters of the composite strata and the tunnel structure parameters. The influence of these two types of parameters on surface settlement is a complex and mutually influential process.

[0004] (2) Three-dimensional surface settlement methods rely primarily on numerical simulation and neural network technology. The accuracy of numerical simulation depends on the values ​​of soil parameters. Although soil parameters can be inverted through on-site measured surface settlement, this method is only suitable for post-settlement analysis and cannot achieve the purpose of pre-settlement prevention. The hyperparameter optimization of neural network technology has a great deal of randomness and lacks a mechanical basis, so it cannot be truly applied to the prediction of related engineering projects. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a method for predicting three-dimensional surface settlement during tunnel construction in composite strata, solving the technical challenge of predicting three-dimensional surface settlement in composite layered strata under the combined influence of soil parameters and tunnel structural parameters.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A method for predicting three-dimensional surface settlement during tunnel construction in composite strata is provided, comprising the following steps: S1: Construct a two-dimensional surface settlement formula, use the known tunnel crown convergence value and the tunnel portal excavation volume per unit excavation length to calculate the surface loss volume per unit excavation length, and express the relationship between surface settlement and tunnel radius and settlement trough width. S2: Obtain the dimensionless settlement trough width relationship curve under different tunnel radius and tunnel burial depth conditions, and based on the relationship between the settlement amount and the tunnel radius and settlement trough width, construct the relationship model between settlement trough width, tunnel radius and tunnel burial depth, fit the slope coefficient of each relationship curve in the relationship curve graph and calculate the constant term to obtain the fitted relationship model. S3: The width of the settlement trough at different tunnel depths under the composite strata is predicted using the fitted relational model and input into the two-dimensional surface settlement formula. Then, the spatial deformation factor is introduced to calculate the three-dimensional surface settlement under different tunnel radii and tunnel depths in the composite strata.

[0007] Further, step S1 includes: S11: Constructing a two-dimensional formula for surface settlement: ,in, i The width of the settling tank. This refers to the surface loss volume per unit length of excavation during tunnel excavation. x The distance from the center of the settlement curve to the calculation point is... This refers to surface subsidence. S12: Tunnel excavation volume per unit excavation length during tunnel excavation. Calculate the surface loss volume ; , ; in, ε This refers to the surface volume loss rate. R Where is the tunnel radius. This is the convergence value of the tunnel arch; S13: Surface loss volume Substituting the calculation formula into the surface subsidence prediction formula, we obtain the surface subsidence amount. With tunnel radius R Settling trough width i Relationship; .

[0008] Further, step S2 includes: S21: Obtain different tunnel radii R With tunnel depth h Dimensionless settling trough width under 0 conditions i The relationship curves were plotted, and a model was constructed to show the relationship between the settlement trough width, tunnel radius, and tunnel depth. ; in, These are the slope coefficients, d For constant terms, y For the thickness of the strata, Functions for relational models; S22: Based on the tunnel radius corresponding to each relationship curve in the relationship curve diagram. R Tunnel depth h 0 data and distance x The fitting yielded n Group slope coefficient and the constant terms corresponding to different relationship curves d and take n Group slope coefficient The arithmetic mean of the values ​​is used to obtain the slope coefficients of the fitted curve. ; S23: Constant term d The value of is related to the tunnel radius. R Tunnel depth h 0 related, establish tunnel radius R With constant term d Relational Coupling R 1. Tunnel depth h 0 and constant term d Relational Coupling h 01 And based on the difference between the constant term variation and the tunnel radius between adjacent tunnels with different burial depths, a constant term is established. d With tunnel radius R Tunnel depth h The general relationship between 0 and 0.

[0009] Further, step S23 includes: S231: Constant term d The value of is related to the tunnel radius. R Tunnel depth h 0 related, establish tunnel radius R With constant term d Relational Coupling R 1. Tunnel depth h 0 and constant term d Relational Coupling h 01 Coupling quantity R 1. Describe the relative positional relationships and coupling quantities of the relational curves within the same curve family. h 01 Describe the relative positional relationship between different curve families, and define the relationship curves under the same tunnel burial depth and different tunnel radii as the same curve family, with one relationship curve corresponding to one tunnel; Then the first j Coupling quantity under tunnel burial depth conditions The relationship with the constant term is as follows: ; in, s Tunnels with different radii but the same burial depth are numbered. For the first j The first under the condition of tunnel burial depth s The constant term corresponding to each tunnel R s For the first s The radius of the tunnel, Indicates the first s tunnel radius R s Depth of formation under conditions y The relational model value when =0; S232: Calculate the proportional relationship between the change in constant terms and the change in tunnel radius for two adjacent tunnels under different tunnel burial depths, and obtain the relationship coupling quantity under the same tunnel burial depth conditions. ; ; in, For the first j The first under the condition of tunnel burial depth s+ The constant term corresponding to one tunnel, For the first j The first under the condition of tunnel burial depth s+ The radius of a tunnel, For the first j The first under the condition of tunnel burial depth s The radius of the tunnel; This represents the change in a constant term between two adjacent tunnels. This represents the change in radius between two adjacent tunnels; S233: Obtain the coupling quantity of the relationship between different tunnel radii under the same tunnel burial depth. Then, subtract the relationship coupling values ​​corresponding to the radii of two adjacent tunnels to obtain the relationship coupling value difference. And obtain the difference in relational coupling. The difference between the radii of two adjacent tunnels And satisfy ; , ; in, For the first s +1 tunnel corresponding to the relationship coupling quantity; S243: Calculate the average value of the relationship coupling difference under each tunnel burial depth condition. ; ; in, S The number of tunnels under the same burial depth conditions; S235: Based on the tunnel burial depth, calculate the average value of the relationship coupling amount under the burial depth conditions of adjacent tunnels from top to bottom. , And calculate the average value. , The difference between ; ; For the first j +1 average value of the relationship coupling difference under different tunnel burial depth conditions; S236: Setting about the difference threshold ,like Then determine the first j Tunnel burial depth If the spacing between the relationship curves corresponding to the following tunnels is stable, proceed to step S2310; otherwise, if the spacing is unstable and the spacing between the relationship curves is equal to 0, proceed to step S237. S237: Extraction tunnel burial depth not exceeding The relationship between the tunnel and the coupling difference and the tunnel burial depth data are fitted, and the tunnel burial depth does not exceed [the specified value]. The tunnel corresponding to the tunnel burial depth Difference in coupling quantity with relation Relationship functions; ; in, The coefficients for the tunnel burial depth are independent variables. These are the fitting constants; S238: Due to ,but Difference in relational coupling Taking the limit, we get: ; in, The radius of the tunnel; S239: Based on step S238, the tunnel burial depth can be further obtained as not exceeding... A model relating time-dependent coupling quantities, tunnel radius, and tunnel depth: ; in, k Let the tunnel number be the constant term to be determined under homogeneous geological conditions. For the constant term to be determined under homogeneous layer conditions, the first term is... k The radius of the tunnel, For the first k The relationship coupling quantity of each tunnel This refers to the relational coupling quantity; S2310: Extracting tunnel burial depth The above data on the relationship between the tunnels and their corresponding coupling differences, along with the tunnel burial depth data, are used to construct a tunnel burial depth within... The above tunnels correspond to the following tunnel depths Difference in coupling quantity with relation Relationship functions; ; S2311: Based on the relational function in step S2310, the tunnel burial depth can be obtained. The above is a model showing the relationship between the time-dependent coupling quantity and the tunnel burial depth: ; S2312: Coupling amount based on the relationship in step S232 The calculation formula and the simultaneous relational model Relationship Model ;get: ; Among them, when When it approaches 0, the first j The coupling quantity of the relationship between +1 types of tunnel burial depths approaches the first... k The coupling quantity relating to the burial depth of various tunnels; S2313: Integrate the formula in step S2312 to obtain the constant term. d With tunnel radius R Tunnel depth h The general relationship between 0 and 0; ; in, d s For homogeneous layers, the first s The known constant term corresponding to the radius of the tunnel is the measured width of the surface settlement trough of the existing tunnel. For homogeneous layers, the first k Type of tunnel radius The corresponding constant term to be determined; S2314: Change the constant term d With tunnel radius R Tunnel depth h The general relationship between 0 and 0 and the slope coefficient of the fit Input the relational model to obtain the fitted relational model.

[0010] Further, step S3 includes: S31: Obtain the thickness of each stratum in the composite formation. h u , uThe strata are numbered, and each stratum is equivalently formed into a homogeneous layer. The elastic modulus of the homogeneous layer is... E n The equivalent thickness of each layer in the composite strata is then... The depth of the tunnel axis for: ; ; in, strata u The elastic modulus, n The number of strata above the tunnel axis; S32: The burial depth of the tunnel axis in the composite strata. Substituting into the general relation, using the embedment depth Replace tunnel burial depth h 0, calculate the tunnel depth. Values ​​of the constant term under certain conditions d u ; S33: Value to be taken d u In the fitted relational model, calculate the predicted settlement trough width for different tunnel burial depths under composite strata. ; ; S34: Based on the two-dimensional surface settlement formula, a spatial deformation factor is introduced to obtain the three-dimensional surface settlement calculation formula for tunnel construction in composite strata; ; ; in, z This is the distance from the tunnel face to the starting point of excavation. t This is a correction term for the distance from the tunnel face to the starting point of excavation. This refers to the three-dimensional subsidence of the earth's surface. S35: Predicted settlement trough width Input the three-dimensional settlement calculation formula to calculate the settlement under the composite strata. Three-dimensional surface settlement at different tunnel depths.

[0011] The beneficial effects of this invention are as follows: This invention proposes a rapid three-dimensional prediction method for surface settlement that can comprehensively consider complex geological conditions, construction conditions, and the characteristics of tunnel excavation disturbance transmission, so as to realize timely prediction of the geological disturbance transmission effect during tunnel construction, and can also effectively solve the problems of inconvenience of previous technical means and difficulty in understanding and use by construction technicians. Attached Figure Description

[0012] Figure 1 A flowchart for a method to predict three-dimensional surface settlement during tunnel construction in composite strata.

[0013] Figure 2 A schematic diagram of the coordinate system constructed for an example.

[0014] Figure 3 This is a curve showing the relationship between the tunnel radius and the dimensionless settlement trough width at the burial depth.

[0015] Figure 4 This is a graph showing the relationship between the coupling quantity and the tunnel burial depth. Figure 5 A schematic diagram of homogeneous equivalent formation. Detailed Implementation

[0016] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0017] like Figure 1 As shown, a method for predicting three-dimensional surface settlement during tunnel construction in composite strata includes the following steps: S1: Construct a two-dimensional surface settlement formula. Using the known tunnel arch convergence value and the tunnel portal excavation volume per unit excavation length, calculate the surface loss volume per unit excavation length, and express the relationship between surface settlement and tunnel radius and settlement trough width. Step S1 specifically includes: S11: Constructing a two-dimensional formula for surface settlement: ,in, i The width of the settling tank. This refers to the surface loss volume per unit length of excavation during tunnel excavation. x The distance from the center of the settlement curve to the calculation point is... This refers to surface subsidence. y Vertical direction; In this embodiment, the following is introduced: Figure 2 In the coordinate system shown, the positive direction of the coordinate axes represents the positive direction of the physical quantity in subsequent calculations.

[0018] S12: Tunnel excavation volume per unit excavation length during tunnel excavation. Calculate the surface loss volume ; , ; in, ε This refers to the surface volume loss rate.R Where is the tunnel radius. This is the convergence value of the tunnel arch; S13: Surface loss volume Substituting the calculation formula into the surface subsidence prediction formula, we obtain the surface subsidence amount. With tunnel radius R Settling trough width i Relationship; .

[0019] S2: Obtain the dimensionless settlement trough width relationship curve under different tunnel radius and tunnel burial depth conditions, and based on the relationship between the settlement amount and the tunnel radius and settlement trough width, construct the relationship model between settlement trough width, tunnel radius and tunnel burial depth, fit the slope coefficient of each relationship curve in the relationship curve graph and calculate the constant term to obtain the fitted relationship model.

[0020] Step S2 specifically includes: S21: Obtain different tunnel radii R With tunnel depth h Dimensionless settling trough width under 0 conditions i The relationship curve was plotted, and a model of the relationship between the width of the settlement trough and the tunnel burial depth was constructed. ; in, These are the slope coefficients, d For constant terms, y For the thickness of the strata, This is a function for the relational model.

[0021] like Figure 3 As shown, this embodiment plots tunnels with different radii. R Tunnel depth h 0. Settling tank width i The relationship curves are plotted. Based on the data corresponding to each relationship curve in the relationship curve plot, the slope coefficients and constant terms are obtained as shown in Table 1 below.

[0022] Table 1. Fit coefficients and goodness of fit

[0023] S22: Based on the tunnel radius corresponding to each relationship curve in the relationship curve diagram. R Tunnel depth h 0 data and distance x The fitting yielded n Group slope coefficient and the constant terms corresponding to different relationship curves d and take nGroup slope coefficient The arithmetic mean of the slope coefficients is used in this embodiment, taking the arithmetic mean of the 35 slope coefficients in Table 1 to obtain the fitted slope coefficients. ; according to Figure 2 The relationship curves shown exhibit a smooth relationship, and the slope of each curve should be the same as the slope of the relationship model. The slope coefficients calculated in this embodiment... .

[0024] S23: Constant term d The value of is related to the tunnel radius. R Tunnel depth h 0 related, establish tunnel radius R With constant term d Relational Coupling R 1. Tunnel depth h 0 and constant term d Relational Coupling h 01 And based on the difference between the constant term variation and the tunnel radius between adjacent tunnels with different burial depths, a constant term is established. d With tunnel radius R Tunnel depth h The general relationship between 0 and 0. Step S23 specifically includes: S231: Constant term d The value of is related to the tunnel radius. R Tunnel depth h 0 related, establish tunnel radius R With constant term d Relational Coupling R 1. Tunnel depth h 0 and constant term d Relational Coupling h 01 Coupling quantity R 1. Describe the relative positional relationships and coupling quantities of the relational curves within the same curve family. h 01 Describe the relative positional relationship between different curve families, and define the relationship curves under the same tunnel burial depth and different tunnel radii as the same curve family, with one relationship curve corresponding to one tunnel; Then the first j Coupling quantity under tunnel burial depth conditions The relationship with the constant term is as follows: ; in, s Tunnels with different radii but the same burial depth are numbered. For the first j The first under the condition of tunnel burial depth sThe constant term corresponding to each tunnel R s For the first s The radius of the tunnel, Indicates the first s tunnel radius R s Depth of formation under conditions y The relational model value when =0; The lower coupling quantity determines the relative position of different curve clusters, which includes the influence of two major tunnel structural parameters: tunnel radius and tunnel depth. Based on the data in Table 1, Table 2 is summarized below. Table 2 clearly shows that the constant term for different tunnel radii exhibits a trend of first increasing and then decreasing with tunnel depth.

[0025] Table 2. Relationship between constant terms and tunnel radius and tunnel depth.

[0026] S232: Calculate the proportional relationship between the change in constant terms and the change in tunnel radius for two adjacent tunnels under different tunnel burial depths, and obtain the relationship coupling quantity under the same tunnel burial depth conditions. ; ; in, For the first j The first under the condition of tunnel burial depth s+ The constant term corresponding to one tunnel, For the first j The first under the condition of tunnel burial depth s+ The radius of a tunnel, For the first j The first under the condition of tunnel burial depth s The radius of the tunnel; This represents the change in a constant term between two adjacent tunnels. This represents the change in radius between two adjacent tunnels; In this embodiment, the data relationship between the relationship coupling quantity and the tunnel radius is shown in Table 3 below, and the relationship curve between the relationship coupling quantity and the tunnel burial depth is shown in the figure below. Figure 4 As shown.

[0027] Table 3. Data Relationship Between Coupling Amount and Tunnel Radius

[0028] The radii of two adjacent tunnels at the same tunnel depth (i.e., within the same curve cluster) satisfy Δ R =1) Subtract the corresponding relational coupling quantities to obtain the relational coupling quantity difference, as shown in Table 4 below.

[0029] Table 4. Relationship Table of Coupling Amount Difference

[0030] S233: Obtain the coupling quantity of the relationship between different tunnel radii under the same tunnel burial depth. Then, subtract the relationship coupling values ​​corresponding to the radii of two adjacent tunnels to obtain the relationship coupling value difference. And obtain the difference in relational coupling. The difference between the radii of two adjacent tunnels And satisfy ; , ; in, For the first s +1 tunnel corresponding to the relationship coupling quantity; S243: Calculate the average value of the relationship coupling difference under each tunnel burial depth condition. ; ; in, S The number of tunnels under the same burial depth conditions; S235: Based on the tunnel burial depth, calculate the average value of the relationship coupling amount under the burial depth conditions of adjacent tunnels from top to bottom. , And calculate the average value. , The difference between ; ; For the first j +1 average value of the relationship coupling difference under different tunnel burial depth conditions; S236: Setting about the difference threshold ,like Then determine the first j Tunnel burial depth If the spacing between the relationship curves corresponding to the following tunnels is stable, proceed to step S2310; otherwise, if the spacing is unstable and the spacing between the relationship curves is equal to 0, proceed to step S237. In this embodiment, the average value of the relationship coupling difference at each tunnel burial depth is taken as the representative value, and then the relationship between the tunnel burial depth and these representative values ​​is analyzed. It can be found that when the burial depth exceeds 35 m, Δ R 1 approaches 0.001, meaning different tunnel radii R The spacing between the various relationship curves remains basically constant. When the tunnel depth is less than 35 m, as the tunnel depth increases, the spacing between the different tunnels... RThe spacing between the various relationship curves becomes smaller and smaller, but the rate at which the spacing decreases becomes slower and slower. Until it exceeds 35 m, the rate at which the spacing between the various relationship curves decreases is basically stable at 0.001.

[0031] S237: Extraction tunnel burial depth not exceeding The relationship between the tunnel and the coupling difference and the tunnel burial depth data are fitted, and the tunnel burial depth does not exceed [the specified value]. The tunnel corresponding to the tunnel burial depth Difference in coupling quantity with relation Relationship functions; ; in, The coefficients for the tunnel burial depth are independent variables. These are the fitting constants; In this embodiment, a linear first-order fitting was performed on the portion of the tunnel with a burial depth not exceeding 35 m to obtain the following: ; S238: Due to ,but Difference in relational coupling Taking the limit, we get: ; in, The radius of the tunnel; The formula obtained in this embodiment is: ; S239: Based on step S238, the tunnel burial depth can be further obtained as not exceeding... Model of the relationship between time-dependent coupling quantity, tunnel radius, and tunnel burial depth: ; in, k Let the tunnel number be the constant term to be determined under homogeneous geological conditions. For the constant term to be determined under homogeneous layer conditions, the first term is... k The radius of the tunnel, For the first k The relationship coupling quantity of each tunnel This refers to the relational coupling quantity; The relationship model obtained by fitting in this embodiment is: ; S2310: Extracting tunnel burial depth The above data on the relationship between the tunnels and their corresponding coupling differences, along with the tunnel burial depth data, are used to construct a tunnel burial depth within... The above tunnels correspond to the following tunnel depths Difference in coupling quantity with relation Relationship functions; ; S2311: Based on the relational function in step S2310, the tunnel burial depth can be obtained. The above is a model showing the relationship between the time-dependent coupling quantity and the tunnel burial depth: ; In this embodiment, a linear first-order fit is performed on the portion of the tunnel with a burial depth exceeding 35 m, yielding the following result: ; Similarly, we can conclude that: ; S2312: Coupling amount based on the relationship in step S232 The calculation formula and the simultaneous relational model Relationship Model ;get: ; Among them, when When it approaches 0, the first j The coupling quantity of the relationship between +1 types of tunnel burial depths approaches the first... k Coupling quantity related to tunnel burial depth; S2313: Integrate the formula in step S2312 to obtain the constant term. d With tunnel radius R Tunnel depth h The general relationship between 0 and 0; ; in, d s For homogeneous layers, the first s The known constant term corresponding to the radius of the tunnel is the measured width of the surface settlement trough of the existing tunnel. For homogeneous layers, the first k Type of tunnel radius The corresponding constant term to be determined; S2314: Change the constant term d With tunnel radius R Tunnel depth h The general relationship between 0 and 0 and the slope coefficient of the fit Input the relational model to obtain the fitted relational model.

[0032] S3: Predict the width of the settlement trough at different tunnel depths under composite strata using the fitted relationship model, and input it into the two-dimensional surface settlement formula. Then, introduce the spatial deformation factor to calculate the three-dimensional surface settlement under different tunnel radii and tunnel depths in composite strata. Step S3 specifically includes: S31: As Figure 5 As shown, the thickness of each stratum in the composite strata is obtained. h u , u The strata are numbered, and each stratum is equivalently formed into a homogeneous layer. The elastic modulus of the homogeneous layer is... E n The equivalent thickness of each layer in the composite strata is then... and the depth of the tunnel axis for: ; ; in, strata u The elastic modulus, n The number of strata above the tunnel axis; S32: The burial depth of the tunnel axis in the composite strata. Substituting into the general relation, using the embedment depth Replace tunnel burial depth h 0, calculate the tunnel depth. Values ​​of the constant term under certain conditions d u ; S33: Value to be taken d u In the fitted relational model, calculate the predicted settlement trough width for different tunnel burial depths under composite strata. ; ; S34: Based on the two-dimensional surface settlement formula, a spatial deformation factor is introduced to obtain the three-dimensional surface settlement calculation formula for tunnel construction in composite strata; ; ; in, z This is the distance from the tunnel face to the starting point of excavation. t This is a correction term for the distance from the tunnel face to the starting point of excavation. This refers to the three-dimensional subsidence of the earth's surface. S35: Predicted settlement trough width Input the three-dimensional settlement calculation formula to calculate the settlement under the composite strata. Three-dimensional surface settlement at different tunnel depths.

[0033] In this embodiment t The value needs to be taken as (0.1-0.2)×2 RThe value is such that the position of the longitudinal settlement inflection point is horizontally shifted to the rear of the working face. The effect of this improvement is equivalent to shifting the inflection point that originally appeared above the working face to the rear of the working face, which is consistent with the phenomenon observed in actual engineering monitoring.

[0034] This invention proposes a rapid three-dimensional prediction method for surface settlement that can comprehensively consider complex geological conditions, construction conditions, and the characteristics of disturbance transmission during tunnel excavation. This method enables timely prediction of the effects of geological disturbance transmission during tunnel construction and effectively solves the problems of inconvenience and difficulty in understanding and using previous technologies.

Claims

1. A method for predicting three-dimensional surface settlement during tunnel construction in composite strata, characterized in that, Includes the following steps: S1: Construct a two-dimensional surface settlement formula, use the known tunnel crown convergence value and the tunnel portal excavation volume per unit excavation length to calculate the surface loss volume per unit excavation length, and express the relationship between surface settlement and tunnel radius and settlement trough width. S2: Obtain the dimensionless settlement trough width relationship curve under different tunnel radius and tunnel burial depth conditions, and based on the relationship between the settlement amount and the tunnel radius and settlement trough width, construct the relationship model between settlement trough width, tunnel radius and tunnel burial depth, fit the slope coefficient of each relationship curve in the relationship curve graph and calculate the constant term to obtain the fitted relationship model. S3: The width of the settlement trough at different tunnel depths under the composite strata is predicted using the fitted relational model and input into the two-dimensional surface settlement formula. Then, the spatial deformation factor is introduced to calculate the three-dimensional surface settlement under different tunnel radii and tunnel depths in the composite strata.

2. The method for predicting three-dimensional surface settlement during tunnel construction in composite strata according to claim 1, characterized in that, The step S1 comprises: S11: Constructing a two-dimensional formula for surface settlement: ,in, i The width of the settling tank. This refers to the surface loss volume per unit length of excavation during tunnel excavation. x The distance from the center of the settlement curve to the calculation point is... This refers to surface subsidence. S12: Tunnel excavation volume per unit excavation length during tunnel excavation. Calculate the surface loss volume ; ， ； in, ε This refers to the surface volume loss rate. R Where is the tunnel radius. This is the convergence value of the tunnel arch; S13: Surface loss volume Substituting the calculation formula into the surface subsidence prediction formula, we obtain the surface subsidence amount. With tunnel radius R Settling trough width i Relationship; 。 3. The method for predicting three-dimensional surface settlement during tunnel construction in composite strata according to claim 1, characterized in that, The step S2 comprises: S21: Obtain different tunnel radii R With tunnel depth h Dimensionless settling trough width under 0 conditions i The relationship curves were plotted, and a model was constructed to show the relationship between the settlement trough width, tunnel radius, and tunnel depth. ； in, These are the slope coefficients, d For constant terms, y For the thickness of the strata, Functions for relational models; S22: Based on the tunnel radius corresponding to each relationship curve in the relationship curve diagram. R Tunnel depth h 0 data and distance x The fitting yielded n Group slope coefficient and the constant terms corresponding to different relationship curves d and take n Group slope coefficient The arithmetic mean of the values ​​is used to obtain the slope coefficients of the fitted curve. ; S23: Constant term d The value of is related to the tunnel radius. R Tunnel depth h 0 related, establish tunnel radius R With constant term d Relational Coupling R 1. Tunnel depth h 0 and constant term d Relational Coupling h 01 And based on the difference between the constant term variation and the tunnel radius between adjacent tunnels with different burial depths, a constant term is established. d With tunnel radius R Tunnel depth h The general relationship between 0 and 0.

4. The method for predicting three-dimensional surface settlement during tunnel construction in composite strata according to claim 3, characterized in that, Step S23 includes: S231: Constant term d The value of is related to the tunnel radius. R Tunnel depth h 0 related, establish tunnel radius R With constant term d Relational Coupling R 1. Tunnel depth h 0 and constant term d Relational Coupling h 01 Coupling quantity R 1. Describe the relative positional relationships and coupling quantities of the relational curves within the same curve family. h 01 Describe the relative positional relationship between different curve families, and define the relationship curves under the same tunnel burial depth and different tunnel radii as the same curve family, with one relationship curve corresponding to one tunnel; Then the first j Coupling quantity under tunnel burial depth conditions The relationship with the constant term is as follows: ； in, s Tunnels with different radii but the same burial depth are numbered. For the first j The first under the condition of tunnel burial depth s The constant term corresponding to each tunnel R s For the first s The radius of the tunnel, Indicates the first s tunnel radius R s Depth of formation under conditions y The relational model value when =0; S232: Calculate the proportional relationship between the change in constant terms and the change in tunnel radius for two adjacent tunnels under different tunnel burial depths, and obtain the relationship coupling quantity under the same tunnel burial depth conditions. ; ； in, For the first j The first under the condition of tunnel burial depth s+ The constant term corresponding to one tunnel, For the first j The first under the condition of tunnel burial depth s+ The radius of a tunnel, For the first j The first under the condition of tunnel burial depth s The radius of the tunnel; This represents the change in a constant term between two adjacent tunnels. This represents the change in radius between two adjacent tunnels; S233: Obtain the coupling quantity of the relationship between different tunnel radii under the same tunnel burial depth. Then, subtract the relationship coupling values ​​corresponding to the radii of two adjacent tunnels to obtain the relationship coupling value difference. And obtain the difference in relational coupling. The difference between the radii of two adjacent tunnels And satisfy ; ， ； in, For the first s +1 tunnel corresponding to the relationship coupling quantity; S243: Calculate the average value of the relationship coupling difference under each tunnel burial depth condition. ; ； in, S The number of tunnels under the same burial depth conditions; S235: Based on the tunnel burial depth, calculate the average value of the relationship coupling amount under the burial depth conditions of adjacent tunnels from top to bottom. , And calculate the average value. , The difference between ; ; For the first j +1 average value of the relationship coupling difference under different tunnel burial depth conditions; S236: Setting about the difference threshold ,like Then determine the first j Tunnel burial depth If the spacing between the relationship curves corresponding to the following tunnels is stable, proceed to step S2310; otherwise, if the spacing is unstable and the spacing between the relationship curves is equal to 0, proceed to step S237. S237: Extraction tunnel burial depth not exceeding The relationship between the tunnel and the coupling difference and the tunnel burial depth data are fitted, and the tunnel burial depth does not exceed [the specified value]. The tunnel corresponding to the tunnel burial depth Difference in coupling quantity with relation Relationship functions; ； in, The coefficients for the tunnel burial depth are independent variables. These are the fitting constants; S238: Due to ,but Difference in relational coupling Taking the limit, we get: ； in, The radius of the tunnel; S239: Based on step S238, the tunnel burial depth can be further obtained as not exceeding... A model relating time-dependent coupling quantities, tunnel radius, and tunnel depth: ； in, k Let the tunnel number be the constant term to be determined under homogeneous geological conditions. For the constant term to be determined under homogeneous layer conditions, the first term is... k The radius of the tunnel, For the first k The relationship coupling quantity of each tunnel This refers to the relational coupling quantity; S2310: Extracting tunnel burial depth The above data on the relationship between the tunnels and their corresponding coupling differences, along with the tunnel burial depth data, are used to construct a tunnel burial depth within... The above tunnels correspond to the following tunnel depths Difference in coupling quantity with relation Relationship functions; ； S2311: Based on the relational function in step S2310, the tunnel burial depth can be obtained. The above is a model showing the relationship between the time-dependent coupling quantity and the tunnel burial depth: ； S2312: Coupling amount based on the relationship in step S232 The calculation formula and the simultaneous relational model Relationship Model ;get: ； Among them, when When it approaches 0, the first j The coupling quantity of the relationship between +1 types of tunnel burial depths approaches the first... k Coupling quantity related to tunnel burial depth; S2313: Integrate the formula in step S2312 to obtain the constant term. d With tunnel radius R Tunnel depth h The general relationship between 0 and 0; ； in, d s For homogeneous layers, the first s The known constant term corresponding to the radius of the tunnel is the measured width of the surface settlement trough of the existing tunnel. For homogeneous layers, the first k Type of tunnel radius The corresponding constant term to be determined; S2314: Change the constant term d With tunnel radius R Tunnel depth h The general relationship between 0 and 0 and the slope coefficient of the fit Input the relational model to obtain the fitted relational model.

5. The method for predicting three-dimensional surface settlement during tunnel construction in composite strata according to claim 4, characterized in that, The step S3 comprises: S31: Obtain the thickness of each stratum in the composite formation. h u , u The strata are numbered, and each stratum is equivalently formed into a homogeneous layer. The elastic modulus of the homogeneous layer is... E n The equivalent thickness of each layer in the composite strata is then... and the depth of the tunnel axis for: ； ； in, strata u The elastic modulus, n The number of strata above the tunnel axis; S32: The burial depth of the tunnel axis in the composite strata. Substituting into the general relation, using the embedment depth Replace tunnel burial depth h 0, calculate the tunnel depth. Values ​​of the constant term under certain conditions d u ; S33: Value to be taken d u In the fitted relational model, calculate the predicted settlement trough width for different tunnel burial depths under composite strata. ; ； S34: Based on the two-dimensional surface settlement formula, a spatial deformation factor is introduced to obtain the three-dimensional surface settlement calculation formula for tunnel construction in composite strata; ； ； in, z This is the distance from the tunnel face to the starting point of excavation. t This is a correction term for the distance from the tunnel face to the starting point of excavation. This refers to the three-dimensional subsidence of the earth's surface. S35: Predicted settlement trough width Input the three-dimensional settlement calculation formula to calculate the surface three-dimensional settlement at different tunnel burial depths under composite strata.

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