Pipe roof structure and design method thereof

Abstract

The application relates to the technical field of tunnel support, and provides a pipe shed structure and a design method thereof. The structure comprises a guide wall, guide grooves and pipe shed pipes. The guide wall is annular. The guide grooves are arranged along the guide wall in a ring shape. At least one guide groove is arranged on the guide wall. The guide grooves are arranged at intervals. The distance between two adjacent guide grooves is the same. The pipe shed pipes are arranged in the guide grooves. The diameter of the guide grooves is greater than that of the pipe shed pipes. The application ensures the accurate positioning and uniform distribution of the pipe shed pipe group outside the tunnel excavation contour, thereby significantly improving the overall rigidity and bearing efficiency of the pipe shed support system, effectively controlling the deformation of surrounding rock, and enhancing the stability of the tunnel portal section or soft surrounding rock stratum.

Description

Technical Field

[0001] This invention relates to the field of tunnel support technology, and more specifically, to a pipe roof structure and its design method. Background Technology

[0002] In the field of tunnel and underground engineering, pipe roofs are a commonly used advanced support method, widely applied in tunnel portal sections or weak surrounding rock strata to control rock deformation and maintain the stability of the excavation face. However, the working mechanism of traditional pipe roof structures is similar to that of a simply supported beam, relying mainly on its own bending resistance when bearing surrounding rock loads, resulting in limited load-bearing capacity. Especially under conditions of high surrounding rock pressure or complex geological conditions, pipe roofs are prone to excessive bending deformation or even torsional failure, which not only affects the support effect but also poses a threat to construction safety. Existing technologies usually attempt to improve the overall load-bearing capacity by increasing the number or cross-sectional size of pipe roofs, but this method often leads to a significant increase in material consumption and engineering costs, and fails to fundamentally improve its stress performance, resulting in deficiencies in both economy and effectiveness. Summary of the Invention

[0003] The purpose of this invention is to provide a pipe roof structure and its design method to improve the above-mentioned problems. To achieve the above objective, the technical solution adopted by this invention is as follows: On the one hand, this application provides a pipe roof structure, including: The system includes a guide wall, a guide groove, and a pipe roof. The guide wall is annular. The guide groove is arranged circumferentially along the guide wall, and at least one guide groove is provided. The guide grooves are spaced apart on the guide wall, and the distance between two adjacent guide grooves is the same. The pipe roof is disposed in the guide groove, and the diameter of the guide groove is larger than the diameter of the pipe roof.

[0004] On the other hand, this application provides a pipe roof structure design method, the method comprising: Obtain preliminary design parameters; Based on the preliminary design parameters, a prestressed pipe shed with integrated sensing elements was constructed in a selected test section, and tensioning and monitoring were carried out to obtain a test section monitoring dataset, which includes the effective prestress time history curve of the steel strand and the deformation of the surrounding rock. Based on the monitoring dataset of the test section, an inversion analysis based on the calculation model of the elastic foundation beam was performed to obtain the calibration parameters; Based on the calibration parameters, the spacing, prestress value and layout of the pipe sheds along the entire line are reviewed and optimized to obtain an optimized design scheme.

[0005] The beneficial effects of this invention are as follows: This invention constructs a stable and rationally arranged pipe roof structure by employing a ring-shaped guide wall in conjunction with circumferentially spaced guide grooves, and by placing pipe roof tubes of matching diameter within the guide grooves. This structure ensures the precise positioning and uniform distribution of the pipe roof tube group outside the tunnel excavation outline, thereby significantly improving the overall rigidity and load-bearing efficiency of the pipe roof support system, effectively controlling surrounding rock deformation, and enhancing the stability of the tunnel entrance section or weak surrounding rock strata.

[0006] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a structural layout diagram of the pipe shed.

[0009] Figure 2 This is a schematic diagram of the pipe structure of the pipe shed.

[0010] Figure 3 This is a diagram showing the layout of the grouting holes.

[0011] The markings in the diagram are: 1. Guide wall; 2. Pipe shed; 3. First anchor head; 4. Steel flower pipe; 5. Second anchor head; 6. Steel strand; 7. Grouting hole. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0013] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0014] Example 1 like Figure 1 As shown, this embodiment provides a pipe roof structure, including a guide wall 1, guide grooves, and pipe roof tubes 2. The guide wall 1 is annular; the guide grooves are arranged circumferentially along the guide wall 1, and at least one guide groove is provided. The guide grooves are spaced apart on the guide wall 1, with the distance between two adjacent guide grooves being the same. The pipe roof tubes 2 are placed in the guide grooves, and the diameter of the guide grooves is larger than the diameter of the pipe roof tubes 2. In this invention, several guide grooves are precisely opened circumferentially on the wall of the guide wall 1. The spacing of these guide grooves must be kept uniform to ensure the regularity of the subsequent pipe roof tube layout. After the pipe roof tubes 2 are initially fixed by the anchoring components provided at their tails, they are inserted one by one into the corresponding guide grooves. The inner diameter of the guide grooves must be slightly larger than the outer diameter of the pipe roof tubes 2. This design provides the necessary radial adjustment margin for the pipe roof tubes 2, enabling them to adapt to small hole position deviations during installation, and after final grouting and consolidation, to form a tight, enveloping, cooperative bearing system with the surrounding rock mass. This structural form, in which the pipe roof is uniformly positioned by the annular guide wall 1 and the pipe roof is installed through the guide groove with gaps, is particularly suitable for tunnel entrance sections with uneven geological conditions or bias pressure. It not only ensures the overall rigidity and stability of the pipe roof group, but also releases local stress concentration through the gaps, thereby significantly improving the reliability of the advanced support system and its adaptability to complex geological conditions.

[0015] In one specific embodiment of this disclosure, the pipe roof 2 includes a steel perforated pipe 4, a first anchor head 3, a second anchor head 5, and a steel strand 6. The steel perforated pipe 4 is disposed in a guide groove, the first anchor head 3 is disposed at the head of the steel perforated pipe 4, and the second anchor head 5 is disposed at the tail of the steel perforated pipe 4. A steel strand 6 is disposed between the first anchor head 3 and the second anchor head 5. The steel strand 6 is inserted between the two anchor heads, and prestress is applied to the steel strand 6 by a tensioning device to put it in a tensile state. In scenarios such as tunnel entrance sections where the surrounding rock is weak and easily deformable, the introduction of this prestress enables the pipe roof to have an inherent ability to resist bending moments before bearing external surrounding rock loads, transforming the traditional passive support into active support, significantly suppressing the bending deformation trend of the pipe roof, thereby fundamentally improving the load-bearing capacity of the pipe roof and the stability of the tunnel excavation face.

[0016] In one specific embodiment of this disclosure, cement grout is placed inside the pipe 2 of the pipe roof, with a water-cement ratio of 1:1. By confining the pipe roof to fill with cement grout of a specific water-cement ratio, a single steel pipe component is transformed into a composite load-bearing body in which the steel pipe and the core concrete work together, thereby achieving a fundamental improvement in load-bearing capacity at the material level. Existing pipe roofs mainly rely on the strength of the steel pipe wall, and their interiors are usually hollow or simply grouted, failing to form an effective composite structure. When subjected to bending moments, the steel pipe is prone to local buckling and loss of stability. This invention injects and solidifies cement grout with a water-cement ratio of 1:1. This ratio ensures that the grout has both good fluidity and final strength. The solidified cement can significantly enhance the steel pipe's ability to resist local buckling. At the same time, when the pipe roof is subjected to bending, the tensile stress in the tension zone of the steel pipe is borne by the steel, while the compressive stress in the compression zone is borne by the cement core that is enclosed and constrained by the steel pipe. The material advantages of the two complement each other, forming a highly efficient structural mechanism similar to steel-concrete composite pipes. This internal reinforcement effect is particularly suitable for tunnel support scenarios that are subjected to complex bending moments, greatly improving the overall stiffness and bending bearing capacity of the pipe roof section, enabling the pipe roof to withstand greater surrounding rock loads with the same amount of steel.

[0017] In one specific embodiment of this disclosure, the steel pipe 4 is composed of at least two seamless steel pipes, with adjacent seamless steel pipes connected by threaded connections. Existing pipe sheds, if using a single long steel pipe, face challenges in restricted environments such as mountain tunnels, including transportation difficulties, inability to adapt to curved tunnel layouts, and the risk of the entire pipe shed being scrapped due to damage at a single point. This invention limits the steel pipe 4 to be composed of multiple seamless steel pipe sections connected by threaded connections. This not only reliably transmits axial force and bending moment, ensuring the overall structural strength is no weaker than the steel pipe body, but also allows for flexible adjustment of the length combination of individual pipe sheds according to actual site conditions, and effectively bypasses underground obstacles, improving the flexibility of pipe shed construction.

[0018] In one specific embodiment of this disclosure, the diameter of the steel pipe is 56mm-180mm and the length of the steel pipe is 2m-8m. Limiting the diameter of the steel pipe allows designers to make precise selections based on the formation pressure. At the same time, limiting the length of a single section of the steel pipe allows it to be flexibly combined into any length required for the project through threaded connections, ensuring that the single section components are easy to transport, handle and operate in narrow tunnels.

[0019] like Figure 3 As shown, in one specific embodiment of this disclosure, at least one grouting hole 7 is provided on the side wall of the steel pipe. The grouting holes 7 are arranged in a quincunx pattern. This arrangement forms a uniform diffusion network in three-dimensional space. When the grout is injected through these holes under pressure, it can achieve more three-dimensional and uniform penetration and splitting in the rock mass around the pipe roof, effectively filling the rock mass fissures and forming a reinforced shell that wraps around the pipe roof with significantly improved strength.

[0020] Example 2 This embodiment provides a pipe roof structure design method, the method including steps S1-S4, specifically including: Step S1: Obtain preliminary design parameters; The core of this step lies in extracting preliminary design basis from macro-level engineering requirements and geological conditions. By analyzing geological survey reports and structural design objectives, complex and spatially variable geological information is transformed into a mechanical model that can be used for quantitative calculation. The basic shape of the pipe roof components and possible prestress loss are also preliminarily estimated. This step establishes a theoretical starting point for the entire invention based on specific site conditions, so that subsequent design is no longer a purely theoretical calculation divorced from geological reality. In particular, it lays an analytical foundation for dealing with common geological uncertainties in tunnel portal sections.

[0021] Step S1 further includes steps S11-S15, which specifically include: Step S11: Obtain the engineering geological survey report and structural design requirements; Understandably, the geological survey report provides information on the physical and mechanical parameters of the rock and soil mass and their spatial distribution obtained through drilling, geophysical exploration, and other means; while the structural design requirements specify the safety level, allowable deformation, and other objectives that the tunnel support needs to achieve.

[0022] Step S12: Based on the engineering geological survey report, perform spatial variability analysis based on geostatistical Kriging interpolation to obtain a continuous distribution cloud map of the elastic modulus and Poisson's ratio of the surrounding rock at the tunnel entrance section; This step uses Kriging interpolation to spatially interpolate discrete geological data. Specifically, the elastic modulus and Poisson's ratio of the surrounding rock at each borehole point in the exploration report are used as known sample data. Based on their spatial location and the spatial correlation reflected by the variogram model, the parameter values ​​of unsampled areas are estimated using the Kriging algorithm. This ultimately generates a continuously distributed elastic modulus and Poisson's ratio cloud map covering the entire tunnel entrance section. This process transforms isolated point-like geological information into a visualized continuous field, clearly revealing the spatial variability of rock mass mechanical properties and providing refined data support for accurately assessing the differences in foundation reaction forces at different locations along the tunnel's longitudinal direction.

[0023] Step S13: Calculate the distribution curve of the preliminary foundation resistance coefficient along the entire length of the pipe roof based on the continuous distribution cloud map of the elastic modulus and Poisson's ratio of the surrounding rock at the tunnel entrance section; This step, based on the theory of elastic foundation beams, calculates the foundation resistance coefficient at each point along the expected pipe roof laying path by using the continuously distributed elastic modulus and Poisson's ratio of the surrounding rock, forming a continuous distribution curve. The specific calculation formula for the foundation resistance coefficient is as follows: In the above formula, Indicates the foundation resistance coefficient; Indicates the outer diameter of the pipe in the pipe shed; This indicates the elastic modulus of the surrounding rock at the tunnel entrance. This represents the Poisson's ratio of the surrounding rock. This indicates the elastic modulus of the pipe roof material; The moment of inertia of the cross-section of the pipe in the pipe shed is expressed by the following formula: , and These represent the outer diameter and inner diameter of the pipe in the pipe shed, respectively.

[0024] Step S14: Based on the distribution curve of the target bearing capacity and the preliminary foundation resistance coefficient specified in the structural design requirements, perform iterative optimization calculation of the normal section bearing capacity based on the prestressed concrete beam theory to obtain the initial geometric and material parameter set of the pipe roof component; It is understandable that the bending moment of the cross-section bearing capacity of the pipe roof is provided by both the steel pipe (and its internal concrete) and the steel strands. The sum of the two should meet the target bearing capacity specified in the structural design requirements. The specific formula for calculating the bearing capacity of the steel pipe is as follows: In the above formula, This indicates the yield strength of the steel pipe material; This indicates the cross-sectional area of ​​the steel pipe in the tension zone. This represents the distance from the centroid of the steel tube in the tension zone to the neutral axis of the entire cross-section; Indicates the concrete strength enhancement factor; This represents the standard value of the axial compressive strength of concrete. This represents the equivalent compressive area of ​​the core concrete in the compression zone of the cross section; This represents the distance from the equivalent resultant force point of the concrete in the compression zone to the neutral axis of the cross section. The specific formula for calculating the bearing capacity of the steel strand is: In the above formula, The effective prestress of the steel strand is represented by the formula: [Formula omitted for brevity]. , This indicates the area of ​​the steel strand. Indicates the effective prestress value; This indicates the distance from the centroid of the prestressed steel strand to the compression edge of the cross-section; The height of the neutral axis represents the equivalent rectangular stress diagram of the cross section.

[0025] It should be noted that the iterative optimization calculation process specifically includes: assuming a set of initial pipe roof parameters, such as the outer diameter of the steel pipe, wall thickness, area of ​​the steel strands, and initial tension control stress; simplifying the pipe roof pipe as a beam supported on a Winkler elastic foundation; calculating the maximum bending moment borne by the pipe roof pipe according to the target load condition; substituting the maximum bending moment borne by the pipe roof pipe as the target value into the section equilibrium equation; solving the equation by adjusting the assumed neutral axis height to back-calculate the required parameters such as the steel pipe diameter, wall thickness, and effective prestress value; checking whether the back-calculated parameters are reasonable (e.g., whether the wall thickness is within the commonly used range, whether the prestress is feasible, etc.); if unreasonable, adjusting the initial parameter assumptions, and re-performing the mechanical analysis and section back-calculation until a set of initial geometric and material parameters for the pipe roof component that satisfies the section equilibrium equation is found.

[0026] Step S15: Based on the initial geometric and material parameter set of the pipe roof component and the engineering geological survey report, perform a superposition prediction of the sub-items of loss considering borehole wall friction, material relaxation and shrinkage creep to obtain a preliminary prestress loss model.

[0027] In this step, the losses caused by hole wall friction are specifically as follows: In the above formula, This represents the prestress loss caused by friction at a distance of x meters from the tensioning end; This indicates the control stress applied at the tensioning end; This represents the coefficient of friction between the prestressed steel strand and the hole wall; This represents the total angle through which the duct rotates from the tensioning end to the calculated section. The coefficient representing the influence of local deviation per meter of duct length on friction; This represents the distance from the tensioning end to the calculated section.

[0028] The specific losses caused by stress relaxation in steel strands are as follows: In the above formula, This represents the prestress loss caused by the relaxation of the steel strand within time t; Indicates the relaxation rate of the steel strand; Indicates the time elapsed after tensioning; This represents the reference time constant, used to normalize time effects.

[0029] The specific losses caused by grout shrinkage and creep are as follows: In the above formula, This represents the prestress loss value caused by the combined shrinkage and creep of the grouting body. This indicates the elastic modulus of the steel strand; Indicates the elastic modulus of the grout; This represents the long-term compressive stress borne by the grout body at the horizontal position of the steel strand; The creep coefficient represents the ratio of creep deformation to initial elastic deformation at time t after loading at age τ. This represents the shrinkage strain of the grout, and the total shrinkage from the start of the curing period to time t.

[0030] By calculating and summing the various losses separately, a preliminary predictive model for the changes in prestress loss over time or under working conditions is established. This ensures that the tension control stress determined in the design phase can fully compensate for these expected losses, guaranteeing that the pipe roof can maintain an effective prestress level during long-term service and ensuring the durability of its active support effect.

[0031] Step S2: Based on the preliminary design parameters, construct a prestressed pipe shed with integrated sensing elements in the selected test section and perform tensioning and monitoring to obtain the test section monitoring dataset. The test section monitoring dataset includes the effective prestress time history curve of the steel strand 6 and the deformation of the surrounding rock. This step involves constructing a tube roof test structure integrated with sensing elements and collecting data on prestress changes and surrounding rock response in real time during tensioning and subsequent processes, thereby linking abstract design parameters with actual mechanical behavior.

[0032] Step S2 further includes steps S21-S24, which specifically include: Step S21: Based on the geometric parameters of the pipe roof and the arrangement of prestressed tendons included in the preliminary design parameters of the test section, the sensor layout is optimized to obtain the initial structure, which is a sensor-pipe roof integrated structure with spatial coordinate markings. This step optimizes the sensor placement based on the geometric dimensions of the test section's pipe roof (e.g., length, diameter) and the arrangement of the prestressed steel strands (e.g., single strand centered or multiple strands symmetrically arranged). First, sensors are placed at key mechanical characteristic points of the pipe roof structure (e.g., the maximum bending moment prediction section, anchoring end, and tensioning end). Fiber optic strain gauges are installed on the steel strands to measure prestress, resistance strain gauges are attached to the steel pipe surface to measure pipe wall strain, and multiple displacement gauges are embedded in the surrounding rock mass to measure surrounding rock deformation. Subsequently, the wiring of all sensors is integrated into a protective sleeve, and their spatial coordinates (distance from the tunnel entrance, circumferential position, radial depth) are precisely correlated and recorded with the pipe roof structure, forming a sensor-pipe roof integrated structure with clearly defined spatial coordinates. This ensures the spatial representativeness and traceability of subsequent data acquisition, laying the foundation for accurately correlating structural response with geological conditions in a concealed underground environment.

[0033] Step S22: Based on the initial structure, synchronously acquire multi-source data during the tensioning process and separate the instantaneous loss based on the system stiffness model to obtain the initial effective prestress value; This step involves simultaneously triggering all sensors while using jacks to tension the steel strands in stages, continuously collecting multi-source data such as oil pressure gauge readings, steel strand strain (via fiber optic grating sensors), and steel pipe strain (via resistance strain gauges). Then, based on a pre-established system stiffness model, the total tension force is subtracted from the prestress loss due to system elastic deformation, thereby separating and calculating the initial effective prestress value applied to the pipe roof at the moment of locking. It should be noted that the system stiffness model comprehensively considers the combined deformation characteristics of the tensioning equipment, anchorages, steel pipes, and their internal grout; its construction process is a well-known technical solution and will not be elaborated here.

[0034] Step S23: Perform noise reduction processing on the initial effective prestress to obtain the effective prestress time history curve of the steel strand 6; In this step, a digital filtering algorithm is used to smooth the initial effective prestress, ultimately outputting a smooth and stable time history curve of the effective prestress of the steel strand. This significantly improves the signal-to-noise ratio of the data, allowing the long-term variation law of the prestress to be clearly displayed and avoiding interference from noise in trend interpretation.

[0035] Step S24: Based on the effective prestress time history curve of the steel strand 6 and the internal displacement monitoring data of the surrounding rock, the deformation field of the surrounding rock is reconstructed and correlated to obtain the deformation amount of the surrounding rock.

[0036] In this step, the effective prestressing time history curve of the steel strand is compared and analyzed with the displacement-time curve measured by displacement gauges at some points within the rock mass. Numerical interpolation is used to reconstruct the overall deformation field cloud map of the surrounding rock using discrete displacement monitoring point data. By analyzing the temporal correlation between the prestress change rate and the surrounding rock deformation rate, the effect of prestressing on suppressing surrounding rock deformation is evaluated, and it is determined whether the deformation is mainly driven by rock creep or prestress loss. This multi-source data correlation analysis transcends the limitations of single-point data, revealing the mechanism of interaction between the pipe roof and the surrounding rock from both spatial and temporal dimensions.

[0037] Step S3: Perform inversion analysis based on the elastic foundation beam calculation model according to the test section monitoring dataset to obtain calibration parameters; Step S3 further includes steps S31-S34, which specifically include: Step S31: Standardize the test section monitoring dataset to obtain a standardized test section monitoring dataset; Step S32: Construct a multi-objective error evaluation function based on the least squares principle using the standardized test section monitoring dataset to obtain the error evaluation function; Key monitoring data from the standardized test section monitoring dataset, including the prestressed steel strand time history curve and surrounding rock deformation, were selected as inversion targets. The predicted values ​​of these targets from the elastic foundation beam calculation model were compared with these targets. Based on the least squares principle, the weighted sum of the squared residuals of each data point was calculated to form an error evaluation function. The specific error evaluation function is as follows: In the above formula, and These represent the weighting coefficients of the prestressing monitoring error term and the surrounding rock deformation monitoring error term, respectively. This represents the normalized error term in the prestressing monitoring data; This represents the normalized error term for the surrounding rock deformation monitoring data. It should be noted that, to eliminate the influence of the absolute magnitude of the data, normalization is performed using the mean square error relative to the variance or average of the prestressing monitoring data, specifically: In the above formula, This represents the total number of steps in the time series. This indicates the total number of prestressed sensors; Indicates the location place, time The measured values ​​of prestress obtained from the measurements; This indicates that the calculation at the location was obtained using the elastic foundation beam model. place, time The predicted value of prestress; This represents the average value of all measured prestressing data. The calculation method for the normalized error term of the surrounding rock deformation monitoring data is the same as that for the prestressing monitoring data, so it will not be elaborated here.

[0038] Step S33: Perform global search optimization of the parameter space based on the genetic algorithm according to the error evaluation function to obtain the global optimal solution estimate of the parameter to be inverted; In this step, the parameters to be inverted are encoded as genes, and a large number of parameter combinations are randomly generated to form an initial population. Then, simulating the selection, crossover, and mutation processes in biological evolution, through multiple iterations, parameter combinations with large error function values ​​are gradually eliminated, while superior combinations are retained and propagated. Finally, the globally optimal solution estimate that minimizes or nearly minimizes the error function value is found within the entire space of possible parameters. This effectively avoids the trap of local optima. When dealing with complex problems such as soil and rock parameter inversion, which are highly nonlinear and may have multiple extreme points, this method is more robust than traditional local search methods such as gradient descent, greatly increasing the probability of finding a globally optimal parameter set that truly matches the actual geological conditions.

[0039] Step S34: Perform uncertainty quantification analysis based on Monte Carlo simulation according to the estimated global optimal solution of the parameters to be inverted, and obtain the calibrated foundation resistance coefficient and prestress loss prediction model.

[0040] This step employs the Monte Carlo simulation method, using the globally optimal estimated value of the parameters to be inverted as the mean, and setting a reasonable variance fluctuation range. Then, thousands of random samples are performed within this range, each forming a set of parameters, which are substituted into the elastic foundation beam model for forward modeling. Finally, the distribution of the fit between all forward modeling results and measured data is statistically analyzed, thereby quantifying the uncertainty range of the inverted parameters and obtaining the calibrated foundation resistance coefficient and prestress loss prediction model and their confidence intervals. Clarifying the probability distribution of the inversion results allows designers to understand the possible fluctuation range of the parameters, enabling them to adopt more conservative or risk-aware design strategies during subsequent full-line design, greatly improving the scientific rigor and robustness of the design scheme in the face of geological uncertainties.

[0041] Step S4: Based on the calibration parameters, the spacing, prestress value and layout of the entire pipe shed are checked and optimized to obtain an optimized design scheme.

[0042] In this step, calibration parameters are used as new input conditions and substituted into the pipe roof design model based on the elastic foundation beam theory. These replace the initial design parameters based on geological survey reports and empirical formulas. With geological conditions at different mileages along the entire line as constraints, and pipe roof spacing, applied prestress values, and circumferential layout range as variables, a large-scale forward calculation analysis is performed again to calculate the surrounding rock deformation and pipe roof stress distribution under given load conditions. This allows the design scheme to actively respond to longitudinal changes in geological conditions, enabling appropriate optimization in areas with better geological conditions (such as increasing spacing and reducing prestress) and precise reinforcement in areas with weaker geological conditions, ultimately resulting in a non-homogeneous optimized design scheme that achieves the best balance between safety and economy.

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0044] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of designing a pipe roof structure, characterized by, include: Obtain preliminary design parameters; According to the preliminary design parameters, a prestressed pipe shed with integrated sensing elements was constructed in the selected test section and tensioned and monitored to obtain the test section monitoring dataset. The test section monitoring dataset includes the effective prestress time history curve of the steel strand (6) and the deformation of the surrounding rock. Based on the monitoring dataset of the test section, an inversion analysis based on the calculation model of the elastic foundation beam was performed to obtain the calibration parameters; Based on the calibration parameters, the spacing, prestress value and layout of the pipe sheds along the entire line are checked and optimized to obtain an optimized design scheme; The preliminary design parameters include: Obtain engineering geological survey reports and structural design requirements; Based on the engineering geological survey report, a spatial variability analysis based on geostatistical Kriging interpolation was conducted to obtain a continuous distribution cloud map of the elastic modulus and Poisson's ratio of the surrounding rock at the tunnel entrance. Based on the continuous distribution cloud map of the elastic modulus and Poisson's ratio of the surrounding rock at the tunnel entrance section, the distribution curve of the preliminary foundation resistance coefficient along the entire length of the pipe roof is obtained. Based on the distribution curve of the target bearing capacity and the preliminary foundation resistance coefficient specified in the structural design requirements, the normal section bearing capacity is iteratively optimized based on the prestressed concrete beam theory to obtain the initial geometric and material parameter set of the pipe roof component; Based on the initial geometric and material parameter set of the pipe roof components and the engineering geological survey report, a preliminary prestress loss model is obtained by superimposing and predicting the sub-items of loss considering hole wall friction, material relaxation and shrinkage creep. The process includes constructing a prestressed pipe roof integrated with sensing elements within a selected test section, and then performing tensioning and monitoring based on the preliminary design parameters. Based on the geometric parameters of the pipe roof and the arrangement of prestressed tendons included in the preliminary design parameters of the test section, the sensor layout was optimized to obtain the initial structure, which is a sensor-pipe roof integrated structure with spatial coordinate markings. Based on the initial structure, multi-source data synchronous acquisition and instantaneous loss separation based on the system stiffness model are performed during the tensioning process to obtain the initial effective prestress value; The initial effective prestress is subjected to noise reduction processing to obtain the effective prestress time history curve of the steel strand (6); Based on the effective prestress time history curve of the steel strand (6) and the internal displacement monitoring data of the surrounding rock, the deformation field of the surrounding rock is reconstructed and correlated to obtain the deformation amount of the surrounding rock.

2. The pipe roof structure design method according to claim 1, wherein Based on the monitoring dataset of the test section, an inversion analysis based on the calculation model of the elastic foundation beam is performed, including: The test section monitoring dataset is standardized to obtain the standardized test section monitoring dataset. Based on the standardized test section monitoring dataset, a multi-objective error evaluation function based on the least squares principle is constructed to obtain the error evaluation function. Based on the error evaluation function, a global search optimization of the parameter space based on a genetic algorithm is performed to obtain the estimated global optimal solution value of the parameter to be inverted; Uncertainty quantification analysis based on Monte Carlo simulation is performed on the estimated global optimal solution of the parameters to be inverted to obtain the calibrated foundation resistance coefficient and prestress loss prediction model.

3. A pipe roof structure for use in the pipe roof structure design method according to any one of claims 1 to 2, characterized by, include: Guide wall (1), the guide wall (1) is annular; The guide groove is arranged circumferentially along the guide wall (1), and at least one guide groove is provided. The guide grooves are spaced apart on the guide wall (1), and the distance between two adjacent guide grooves is the same. Pipe shed pipe (2), the pipe shed pipe (2) is set in the guide groove, the diameter of the guide groove is larger than the diameter of the pipe shed pipe (2).

4. The tube shed structure of claim 3, wherein The pipe shed pipe (2) includes a steel flower pipe (4), a first anchor head (3), a second anchor head (5), and a steel strand (6). The steel flower pipe (4) is set in the guide groove. The first anchor head (3) is set at the head of the steel flower pipe (4). The second anchor head (5) is set at the tail of the steel flower pipe (4). The steel strand (6) is set between the first anchor head (3) and the second anchor head (5).

5. The pipe roof structure according to claim 3, characterized in that The pipe shed (2) is filled with cement grout, and the water-cement ratio of the cement grout is 1:

1.

6. The pipe shed structure of claim 4, wherein The steel pipe (4) is composed of at least two seamless steel pipes, and the two adjacent seamless steel pipes are connected by threads.

7. The tube shed structure of claim 6, wherein The diameter of the steel pipe is 56mm-180mm, and the length of the steel pipe is 2m-8m.

8. The pipe shed structure of claim 6, wherein At least one grouting hole (7) is provided on the side wall of the steel pipe, and the grouting hole (7) is arranged in a quincunx pattern.

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