Supporting method and structure of station with underground excavation in jointed rock mass

Abstract

The application discloses a supporting method and structure of a joint rock mass subsurface station, which comprises the following steps: vertically excavating a shaft in a rock mass from the ground; excavating a horizontal passage from the bottom of the shaft; excavating a plurality of guide holes in the horizontal passage; simultaneously performing concrete backfilling to set an outer primary support; performing inner primary support and arch secondary lining construction; continuously excavating the rock mass below the arch top; performing side wall primary lining construction; striking side wall anchor cables from the side wall primary lining; performing inverted arch secondary lining construction and setting a station structure middle plate above the inverted arch secondary lining; and setting platform layer structure columns. The application sets a shaft, excavates a horizontal passage at the bottom of the shaft as a foundation working face, and excavates the whole station, so that the required area of the construction site is effectively reduced. Meanwhile, through the setting of the outer primary support, the inner primary support, the arch secondary lining, the longitudinal beam anchor cable and the side wall anchor cable above the station arch top, the supporting effect of the supporting structure on the rock mass is effectively ensured.

Description

Technical Field

[0001] This invention relates to the field of long-span tunnel construction, and particularly to a support method and structure for a tunnel station built in jointed rock mass. Background Technology

[0002] During the construction of urban subway stations, minimizing the impact of station construction on surrounding existing structures is a key concern. Furthermore, station construction is often concentrated in densely built-up urban areas, limiting construction space. When the shield tunneling method is used for tunnel sections, receiving shafts are required, further increasing the required construction area. Additionally, because it is difficult to avoid traversing unfavorable rock formations (joints, faults, interlayers) during station construction, it is challenging to guarantee the supporting structure's effectiveness for the entire station. Summary of the Invention

[0003] This invention provides a support method and structure for tunneling stations in jointed rock masses to overcome the aforementioned technical problems.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A support method for a tunnel-excavated railway station in jointed rock mass includes the following steps:

[0006] S1: Excavate a vertical shaft from the ground down into the rock mass;

[0007] S2: Excavate a horizontal passage from the bottom of the shaft;

[0008] S3: Excavate a first longitudinal guide tunnel and a second longitudinal guide tunnel within the transverse passage, wherein the excavation direction of the first longitudinal guide tunnel and the second longitudinal guide tunnel is perpendicular to the axis of the vertical shaft.

[0009] S4: Steel pipe piles are constructed below the first longitudinal guide tunnel and the second longitudinal guide tunnel respectively, so as to drive the steel pipe piles into the rock mass in a vertically downward direction;

[0010] S5: Along the excavation direction of the first longitudinal guide tunnel, excavate the third longitudinal guide tunnel and the fourth longitudinal guide tunnel in the transverse passage; the third longitudinal guide tunnel and the fourth longitudinal guide tunnel form the initial support of the shaft with the shaft wall;

[0011] S6: Concrete backfilling is carried out on the first and second longitudinal pilot tunnels in the direction away from the rock mass to form a concrete backfill layer;

[0012] S7: On the side of the concrete backfill layer, the third longitudinal guide tunnel and the fourth longitudinal guide tunnel away from the rock mass, an outer initial support is set along the direction away from the rock mass;

[0013] S8: Construct the bottom longitudinal beam at the bottom end of the arch, and pour concrete at the connection between the bottom end of the arch and the rock mass;

[0014] S9: Construction of longitudinal beam anchor cables is carried out at the end of the bottom of the arch to drive the longitudinal beam anchor cables into the rock mass.

[0015] S10: On the side of the outer primary support away from the rock mass, the inner primary support and the arch secondary lining are constructed in sequence, and the outer primary support, inner primary support and arch secondary lining together form the arch crown;

[0016] S11: The shaft is constructed in sequence along the direction away from the rock mass, with the initial lining and secondary lining of the shaft to reinforce the shaft;

[0017] S12: Construction of a reinforcement zone at the connection between the arch and the shaft; so that the arch and the primary and secondary linings of the shaft are connected through the reinforcement zone;

[0018] S13: Continue excavating the rock mass below the arch to form the station passage;

[0019] S14: Construction of the initial lining of the sidewalls is carried out below the ends on both sides of the bottom of the arch; the initial lining of the sidewalls is set on the side of the steel pipe pile away from the rock mass; and the sidewall anchor cables are driven from the initial lining of the sidewalls toward the rock mass.

[0020] S15: Construction of the invert arch secondary lining at the bottom of the station passage; the two ends of the invert arch secondary lining are respectively connected to the bottom of the side wall primary lining on both sides.

[0021] S16: A station structure middle plate is horizontally installed above the secondary lining of the inverted arch; the two ends of the station structure middle plate are respectively connected to the initial lining of the side walls on both sides;

[0022] S17: Construction of platform layer structural columns is carried out between the station structure slab and the inverted arch lining. The top of the platform layer structural columns is connected to the station structure slab, and the bottom is connected to the inverted arch lining.

[0023] Furthermore, the thickness of the arch, the length of the longitudinal beam anchor cable, the distance between two longitudinal beam anchor cables, the length of the steel pipe pile, the distance between two steel pipe piles, the length of the side wall anchor cable, the distance between two side wall anchor cables, and the number of side wall anchor cable rows are all calculated based on the joint parameters of the rock mass during the station construction process.

[0024] Furthermore, the joint parameters of the rock mass include: joint cohesion, joint expansion angle, joint friction angle, joint tensile strength, joint dip direction, and joint dip angle.

[0025] Furthermore, the method for obtaining joint parameters of the rock mass during the station construction process is as follows:

[0026] S101, Based on the initially determined surrounding rock grade, determine the range of joint parameters for the rock mass;

[0027] S102, using orthogonal design and uniform design methods, obtain combination schemes of joint parameters for rock masses with several orthogonal designs and combination schemes of joint parameters for rock masses with several uniform designs respectively;

[0028] S103: Establish a numerical calculation model for the tunnel excavation of the jointed rock mass; and obtain the crown settlement displacement, arch waist convergence displacement, and crown structural stress based on the combination scheme of the joint parameters of the orthogonally designed rock mass and the combination scheme of the joint parameters of the uniformly designed rock mass.

[0029] S104: Based on the random forest algorithm, the crown settlement displacement, the waist convergence displacement, and the crown structural stress are taken as inputs, and the joint parameters of the rock mass are taken as outputs, in order to obtain an optimized random forest algorithm.

[0030] S105. Based on the optimized random forest algorithm and the range of values ​​for the joint parameters of the rock mass, obtain the optimal joint parameters of the rock mass, i.e., the joint parameters of the rock mass during the station construction process.

[0031] S106, Based on the joint parameters of the optimal rock mass, provide guidance on the construction plan for the tunnel-excavated station in the jointed rock mass.

[0032] A support structure for a tunnel-excavated railway station in jointed rock mass includes: a shaft, an arch, several steel pipe piles, a middle plate of the station structure, a secondary lining of the inverted arch, structural columns of the platform layer, and initial linings of two side walls.

[0033] The shaft is set vertically downwards from the ground; the shaft includes a primary lining and a secondary lining; the primary lining and the secondary lining are sequentially arranged in the direction away from the rock mass and into the shaft.

[0034] The arch is located at the bottom of the shaft and extends in a direction perpendicular to the axis of the shaft, with the top of the arch abutting against the rock mass;

[0035] The arch includes an outer primary support, an inner primary support, and an arch lining; and the outer primary support, the inner primary support, and the arch lining are stacked sequentially in a downward direction along the shaft axis; the surface of the outer primary support away from the inner primary support abuts against the rock mass.

[0036] The inverted arch lining is located below the arch crown, and its bottom abuts against the rock mass.

[0037] The initial lining of the sidewall is disposed between the secondary lining of the inverted arch and the arch top, and the top of the initial lining of the sidewall is fixedly connected to one end of the bottom of the arch top, and the bottom of the initial lining of the sidewall is fixedly connected to the corresponding end of the secondary lining of the inverted arch.

[0038] The station structure slab is horizontally positioned between the arch and the second lining of the inverted arch, and the station structure slab is fixedly connected to the two initial linings of the side walls respectively.

[0039] A first passage is formed between the station structure's central slab and the arch; the station structure's central slab, the initial lining of the sidewalls, and the secondary lining of the inverted arch together form a second passage.

[0040] The platform layer structure column is located between the inverted arch lining and the station structure middle plate, with one end fixedly connected to the bottom of the station structure middle plate and the other end fixedly connected to the top of the inverted arch lining.

[0041] The steel pipe piles are fixedly installed in the rock mass on the side of the initial lining of the sidewall away from the second channel, with one end fixedly connected to one end of the bottom of the arch, and the other end extending vertically downward to the bottom of the second lining of the inverted arch; a number of the steel pipe piles are sequentially installed along one end of the bottom of the arch.

[0042] Furthermore, it also includes two bottom longitudinal beams and several longitudinal beam anchor cables; one end of the bottom of the arch is fixedly connected to the steel pipe pile / side wall lining through the bottom longitudinal beams;

[0043] One end of the longitudinal beam anchor cable is fixedly connected to the bottom longitudinal beam, and the other end is inserted into the rock mass in a direction away from the first channel; a plurality of the longitudinal beam anchor cables are arranged sequentially along the bottom longitudinal beam.

[0044] Furthermore, the shaft and the vault are connected by a reinforced area;

[0045] Furthermore, it also includes several sidewall anchor cables; one end of the sidewall anchor cable is fixedly connected to the initial sidewall lining, and the other end is inserted into the rock mass in a direction away from the second channel.

[0046] Beneficial effects: The present invention provides a support method and structure for a tunnel-excavated railway station in jointed rock mass. By setting up a vertical shaft and excavating a transverse channel at the bottom of the shaft as the foundation working face for the excavation of the entire station, the required area of ​​the construction site is effectively reduced. At the same time, by setting up a primary lining for the shaft, i.e., a secondary lining for the shaft, i.e., a multi-layer support system with an outer primary support, an inner primary support, and a secondary lining for the arch at the station arch, as well as setting up longitudinal beam anchor cables and sidewall anchor cables, the support structure effectively ensures the supporting effect of the rock mass. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a flowchart of the support method for a tunnel-excavated station in jointed rock mass according to the present invention.

[0049] Figure 2 This is a schematic diagram of the steps for excavating a railway station in jointed rock mass according to an embodiment of the present invention. Figure 1 ;

[0050] Figure 3 This is a schematic diagram of the steps for excavating a railway station in jointed rock mass according to an embodiment of the present invention. Figure 2 ;

[0051] Figure 4 This is a schematic diagram of the steps for excavating a railway station in jointed rock mass according to an embodiment of the present invention. Figure 3 ;

[0052] Figure 5 This is a schematic diagram of the steps for excavating a railway station in jointed rock mass according to an embodiment of the present invention. Figure 4 ;

[0053] Figure 6 This is a schematic diagram of the steps for excavating a railway station in jointed rock mass according to an embodiment of the present invention. Figure 5 ;

[0054] Figure 7 This is a schematic diagram of the steps for excavating a railway station in jointed rock mass according to an embodiment of the present invention. Figure 6 ;

[0055] Figure 8 This is a schematic diagram of the jointed rock mass tunnel station in an embodiment of the present invention;

[0056] Figure 9 This is a top view of the jointed rock mass tunnel station in an embodiment of the present invention;

[0057] Figure 10 This is a schematic diagram of the numerical model of the rock mass surrounding the station in the jointed rock mass excavation in an embodiment of the present invention;

[0058] Figure 11 This is a schematic diagram of the numerical model of the tunnel station built into jointed rock mass in an embodiment of the present invention;

[0059] Figure 12 This is a diagram illustrating the iterative process for optimizing joint cohesion and tensile strength in an embodiment of the present invention.

[0060] Figure 13 This is a diagram illustrating the optimization and iteration process of the joint internal friction angle and tilt angle in an embodiment of the present invention;

[0061] Figure 14 This is a diagram illustrating the joint expansion angle and tendency optimization iteration process in an embodiment of the present invention. Detailed Implementation

[0062] 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 embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] This embodiment provides a support method for a tunnel-excavated railway station in jointed rock mass, such as... Figure 1 As shown, the steps include:

[0064] S1: Excavate a vertical shaft 1 from the ground down into the rock mass;

[0065] S2: Excavate a horizontal passage 28 from the bottom of the vertical shaft; as the basic working face for the construction of the underground station;

[0066] S3: Excavate a first longitudinal guide tunnel 281 and a second longitudinal guide tunnel 282 in the transverse passage, wherein the excavation direction of the first longitudinal guide tunnel 281 and the second longitudinal guide tunnel 282 is perpendicular to the axis of the vertical shaft.

[0067] S4: Construction of steel pipe piles 4 is carried out below the first longitudinal guide tunnel 281 and the second longitudinal guide tunnel 282, respectively, so as to drive the steel pipe piles into the rock mass 900 in a vertically downward direction; S1 to S4 are as follows Figure 2 As shown;

[0068] S5: Along the direction of the first longitudinal guide tunnel 281, excavate the third longitudinal guide tunnel 283 and the fourth longitudinal guide tunnel 284 in the transverse passage; the 283 and the fourth longitudinal guide tunnel 284 form a vertical shaft initial support 15 between the vertical shaft and the outer wall of the vertical shaft;

[0069] S6: Concrete backfilling is carried out on the first longitudinal guide tunnel 281 and the second longitudinal guide tunnel 282 in the direction away from the rock mass by 900, forming a concrete backfill layer 285; the concrete backfill layer 285 together with the top of the third longitudinal guide tunnel 283 and the fourth longitudinal guide tunnel 284 form the prototype of the arch.

[0070] S7: On the side of the concrete backfill layer 285, the third longitudinal guide tunnel 283 and the fourth longitudinal guide tunnel 284 away from the rock mass, an outer initial support 21 is set along the direction away from the rock mass 900;

[0071] S8: Construct the bottom longitudinal beam 3 at the bottom end of the arch, and pour concrete at the connection between the bottom end of the arch and the rock mass to make the connection between the steel pipe pile 4, the longitudinal beam anchor cable 31 and the bottom end of the arch more reliable.

[0072] S9: Construct the longitudinal beam anchor cable 31 at the end of the bottom of the arch to drive the longitudinal beam anchor cable 31 into the rock mass at a direction of 90°; as Figure 3 As shown;

[0073] S10: On the side of the outer primary support 21 away from the rock mass, the inner primary support 22 and the arch secondary lining 23 are constructed sequentially, and the outer primary support 21, inner primary support 22, and arch secondary lining 23 together form the arch crown; as Figure 4 and Figure 5 As shown;

[0074] S11: The shaft is constructed in sequence along a direction 900 degrees away from the rock mass, with the initial lining 11 and the secondary lining 12 constructed in order to reinforce the shaft;

[0075] S12: Construction of reinforcement zone 13 at the connection between the arch and the shaft; so that the arch, the initial lining 11, and the secondary lining 12 of the shaft are connected through the reinforcement zone; such as Figure 5 As shown;

[0076] S13: Continue excavating the rock mass below the arch to form station passage 100;

[0077] S14: Construction of the initial lining 9 of the sidewalls is carried out below the ends on both sides of the bottom of the arch; the initial lining 9 of the sidewalls is set on the side of the steel pipe pile 4 away from the rock mass 900; and the sidewall anchor cables 91 are driven into the rock mass from the initial lining 9 of the sidewalls; as Figure 6 As shown;

[0078] S15: Construction of the invert arch secondary lining 7 at the bottom of the station passage 100; the two ends of the invert arch secondary lining 7 are respectively connected to the bottom of the side wall primary lining 9 on both sides.

[0079] S16: A station structure middle plate 6 is horizontally installed above the invert arch secondary lining 7; the two ends of the station structure middle plate 6 are respectively connected to the side wall primary linings 9 on both sides.

[0080] S17: Construction of the platform layer structural column 8 is carried out between the station structure slab 6 and the inverted arch secondary lining. The top end of the platform layer structural column 8 is connected to the station structure slab 6, and the bottom end is connected to the inverted arch secondary lining 7. For example... Figure 7 As shown;

[0081] Specifically, the shaft serves as a connecting passage between the above-ground and underground areas. Its lower part connects to the horizontal passage. From the horizontal passage, the first, second, third, and fourth longitudinal guide tunnels are excavated sequentially, while the tops of the guide tunnels are backfilled with concrete to form a concrete backfill layer. During the excavation of the guide tunnels, the outer initial support is constructed in a timely manner. During the excavation of the third and fourth longitudinal guide tunnels, the inner initial support is constructed. The first and second longitudinal guide tunnels are equipped with bottom longitudinal beams, longitudinal beam anchor cables, and steel pipe piles. After the vertical initial support of the guide tunnels is removed, the arch lining is constructed. The outer initial support, inner initial support, and arch lining constitute the arch crown. An opening is set at the intersection of the arch crown and the shaft, which is perpendicularly connected to the upper shaft. A reinforcement zone is set at the connection point. After the arch lining is completed, the lower main structure rock mass is excavated. During the excavation, the sidewall initial support and sidewall anchor cables are constructed. After the lower rock mass is excavated, the bottom lining is constructed.

[0082] Preferably, the thickness of the arch 2, the length of the longitudinal beam anchor cable 31, the distance between two longitudinal beam anchor cables 31, the length of the steel pipe pile 4, the distance between two steel pipe piles 4, the length of the side wall anchor cable 91, the distance between two side wall anchor cables 91, and the number of side wall anchor cable rows are all dynamically calculated based on the joint parameters of the rock mass during the station construction process. Specifically, the methods used to calculate the thickness of the arch 2, the length of the longitudinal beam anchor cable, the distance between two longitudinal beam anchor cables 31, the length of the steel pipe pile, the distance between two steel pipe piles, the length of the side wall anchor cable, the distance between two side wall anchor cables, and the number of side wall anchor cable rows during the station construction process using the joint parameters of the rock mass are all conventional techniques, and the calculation methods will not be described in detail here.

[0083] Preferably, the joint parameters of the rock mass include: joint cohesion, joint expansion angle, joint friction angle, joint tensile strength, joint dip direction, and joint dip angle.

[0084] Preferably, in an embodiment of the present invention, during the construction of the station, the joint parameters of the rock mass, including joint cohesion, joint expansion angle, joint friction angle, joint tensile strength, joint dip direction, and joint dip angle, are obtained using the following method: (Details follow)

[0085] S101, Based on the initially determined surrounding rock grade, determine the range of joint parameters for the rock mass; the initially determined surrounding rock grade is determined manually by staff based on local geological conditions during the early stages of construction at the subway station.

[0086] S102, using orthogonal design and uniform design methods, obtain combination schemes of joint parameters for rock masses with several orthogonal designs and combination schemes of joint parameters for rock masses with several uniform designs respectively;

[0087] S103: Establish a numerical calculation model for the tunnel excavation of a jointed rock mass station; and obtain the crown settlement displacement, arch waist convergence displacement, and crown structural stress based on the combination scheme of joint parameters of the orthogonally designed rock mass and the combination scheme of joint parameters of the uniformly designed rock mass; wherein, the combination scheme of joint parameters of the orthogonally designed rock mass is used as a training sample, and the combination scheme of joint parameters of the uniformly designed rock mass is used as a test sample; the numerical calculation model is established using general numerical software.

[0088] S104: Based on the random forest algorithm, the crown settlement displacement, the waist convergence displacement, and the crown structural stress are taken as inputs, and the joint parameters of the rock mass are taken as outputs, in order to obtain an optimized random forest algorithm, that is, to obtain the nonlinear mapping relationship between the joint parameters of the rock mass and the displacement and stress.

[0089] Specifically, the two key parameters of the Random Forest algorithm are the number of variables pre-selected in the tree nodes (Q1) and the number of random forest trees (Q2). A small Q1 can lead to overfitting by the classifier, resulting in decreased prediction accuracy; a large Q1 can slow down the algorithm, as the correlation between trees gradually decreases, further reducing classification accuracy. A small Q2 can lead to insufficient training, while a large Q2 increases the computational burden on the model. Since manually selecting these parameters is difficult, this paper uses the Cuckoo Algorithm to optimize Q1 and Q2, resulting in an optimized Random Forest algorithm.

[0090] The optimized random forest algorithm is as follows:

[0091] (a-1) Initially set the number of tree nodes to the number of variables Q1 and the number of random forest trees Q2, and determine the range of values ​​for parameters Q1 and Q2.

[0092] (a-2) Initialize a population with N nests, including the number of nests N and the probability P of a nest being discovered by its owner. a Given the number of iterations K, the locations of the bird nests are randomly generated, with each nest location representing a pair of parameters (Mtry, Ntree).

[0093] (a-3) Using the root mean square error E M,S As the fitness value, the fitness value corresponding to each bird's nest is calculated, and the optimal bird's nest position is retained for the next generation. The root mean square error is defined as follows: the root mean square error is calculated using training samples of the joint parameters of the rock mass;

[0094]

[0095] In the formula: E M,S The root mean square error is: y i This is the actual value; is the predicted value; n is the number of predicted samples.

[0096] (a-4) Update the nest according to Lévy's flight path:

[0097]

[0098] In the formula: x i ( t+1 Let ) represent the position of the i-th bird's nest in the (t+1)-th iteration; x i t Let be the position of the i-th bird's nest in the t-th iteration; α is the step size scaling factor, α > 0; s is the step size; This is a point-to-point multiplication; L(s,λ) is the path of the random walk, and follows the rule u = t - λ The exponential distribution is given by λ, where λ is a constant, typically taken as λ∈(1,3).

[0099] (a-5) Calculate the fitness of the updated bird's nest, compare it with the fitness of the previous generation bird's nest, and update the position of the optimal bird's nest. That is, compare the predicted value of the joint parameters of the rock mass obtained by the random forest algorithm with the true value of the joint parameters of the rock mass in the training sample to determine whether the condition is met. If it is met, stop the iteration; otherwise, return to step (a-3).

[0100] (a-6) Output the number of pre-selected tree nodes Q1 and the number of random forest trees Q2 corresponding to the optimal bird's nest position, and assign them to the random forest algorithm model to obtain the optimized random forest algorithm.

[0101] Through the above steps, an optimized random forest algorithm can be obtained.

[0102] S105. Based on the optimized random forest algorithm and the range of joint parameters of the rock mass, obtain the optimal joint parameters;

[0103] Specifically, based on the optimized random forest algorithm, the joint parameters are selected based on the fitness value of the bird's nest. After satisfying the number of iterations, the optimal joint parameters are obtained. This is a utilization of existing technology and will not be described in detail here.

[0104] S106, Based on the joint parameters of the optimal rock mass, guide the construction plan of the tunnel-excavated station in the jointed rock mass, optimize the construction plan of the tunnel-excavated station in the jointed rock mass, effectively guide the construction, and improve the construction efficiency.

[0105] Specifically, the method for obtaining the optimal joint parameters based on the optimized random forest algorithm is as follows: obtain training samples from the orthogonal design combination scheme, construct a decision tree for each sample, and then use the average of the predictions of all decision trees as the final prediction result.

[0106] Step 1: Sample from the sample and randomly generate k training sets θ1, θ2, ..., θ k ; Generate a corresponding set of decision trees {{T(x,θ1)}, {T(x,θ2)}, ..., {T(x,θ1)} using each training set. k )}}。 Where k is the number of training sets, i.e., the number of combinations of joint parameters of the orthogonally designed rock mass; x is the sampled sample; T(x,θ) k ) represents the k-th decision tree;

[0107] Step 2: Assuming the jointed rock mass parameters have M dimensions, randomly select m features from these M dimensions as the splitting feature set for the current leaf node. Split the leaf node using the feature with the smallest fitness value (generally, the value of m remains constant throughout the entire forest growth process). Each leaf node of the decision tree corresponds to a rectangular space of size B, denoted as _____. Among them, R l Let L be the number of elements in the rectangular space, and l be the element number in the rectangular space. For each x∈B, a leaf node l(x,θ) is defined if and only if there is a leaf node l(x,θ). Satisfying x∈R l Let the decision tree be T(x,θ). k The leaf node of ) is l(x,θ) k ).

[0108] Step 3: Calculate the predicted value of the decision tree by averaging the observations at the leaf nodes. Suppose an observation X... i If a node l(x,θ) belongs to a leaf node and is not zero, let its weight ω be... i (x,θ) is

[0109]

[0110] In the formula, the sum of the weights equals 1, and n is the number of observations.

[0111] Step 5: Prediction of a single decision tree using the observed values ​​Y of the dependent variable. i The weighted average of (i = 1, 2, ..., n) is used to obtain the prediction value of a single decision tree.

[0112]

[0113] Step 6: Using equation (7), the observed value Y of each dependent variable is obtained by averaging the weights of the decision tree. i The weight ω of ∈(1, 2, ..., n) i (x):

[0114]

[0115] The optimal joint parameter value obtained by the optimized cuckoo algorithm can be denoted as:

[0116]

[0117] Specifically, the joint parameters of the rock mass, including joint cohesion, joint expansion angle, joint friction angle, joint tensile strength, joint dip direction, and joint dip angle, are obtained using the methods described above. This yields the optimal joint cohesion, optimal joint expansion angle, optimal joint friction angle, optimal joint tensile strength, optimal joint dip direction, and optimal joint dip angle. Based on these rock mass joint parameters, calculations are performed on the thickness of the arch, the length of the longitudinal beam anchor cables, the distance between two longitudinal beam anchor cables, the length of the steel pipe piles, the distance between two steel pipe piles, the length of the sidewall anchor cables, the distance between two sidewall anchor cables, and the number of rows of sidewall anchor cables during station construction. The station's support construction is then carried out based on the calculation results.

[0118] Preferably, the present invention also discloses a support structure for a tunnel-excavated railway station in jointed rock mass, such as... Figure 8 and Figure 9 As shown, it includes: 1. Shaft, 2. Arch, 4. Several steel pipe piles, 6. Station structure middle plate, 7. Inverted arch secondary lining, 8. Platform layer structure columns, 9. Two side wall initial linings.

[0119] The shaft 1 is set vertically downwards to the ground; preferably, the shaft 1 includes a primary shaft lining 11 and a secondary shaft lining 12;

[0120] Specifically, the shaft 1 serves as a connecting passage between the above-ground and underground areas, allowing construction personnel to access the work area. The shaft 1 is equipped with a primary lining 11 and a secondary lining 12, with the secondary lining 12 connecting to the arch secondary lining 23 at the opening. The shaft 1 and the arch 2 form a composite structure, reducing the construction area required, and the reinforcement zone 13 increases the load-bearing capacity at the opening.

[0121] The arch 2 is located at the bottom of the shaft 1 and extends in a direction perpendicular to the axis of the shaft 1. The top of the arch 2 abuts against the rock mass. An opening 29 is formed between the arch 2 and the shaft 1.

[0122] Preferably, the arch 2 includes an outer primary support 21, an inner primary support 22, and an arch secondary lining 23; and the outer primary support 21, the inner primary support 22, and the arch secondary lining 23 are stacked sequentially in a downward direction along the axis of the shaft 1; the surface of the outer primary support 21 away from the inner primary support 22 abuts against the rock mass 900.

[0123] The inverted arch lining 7 is located below the arch crown 2, and its bottom abuts against the rock mass 900.

[0124] The initial lining of the side wall 9 is disposed between the secondary lining of the inverted arch 7 and the arch 2, and the top of the initial lining of the side wall 9 is fixedly connected to one end of the bottom of the arch 2, and the bottom of the initial lining of the side wall 9 is fixedly connected to the corresponding end of the secondary lining of the inverted arch 7.

[0125] The station structure plate 6 is horizontally positioned between the arch 2 and the inverted arch lining 7, and the station structure plate 6 is fixedly connected to the two side wall linings 9 respectively.

[0126] A first passage 61 is formed between the middle plate 6 of the station structure and the arch 2; the middle plate 6 of the station structure, the initial lining of the side wall 9 and the secondary lining of the inverted arch 7 together form a second passage 62.

[0127] The platform layer structure column 8 is located between the inverted arch lining 7 and the station structure middle plate 6, with one end fixedly connected to the bottom of the station structure middle plate 6 and the other end fixedly connected to the top of the inverted arch lining 7.

[0128] The steel pipe pile 4 is fixedly installed in the rock mass 900 on the side of the initial lining of the side wall away from the second channel 62, and one end of it is fixedly connected to one end of the bottom of the arch 2, while the other end extends vertically downward to the bottom of the invert arch lining 7, which can ensure that the subsequent initial lining of the side wall provides more reliable support for the station; a number of the steel pipe piles 4 are sequentially installed along one end of the bottom of the arch 2.

[0129] Preferably, it also includes two bottom longitudinal beams 3 and several longitudinal beam anchor cables 31; one end of the bottom of the arch 2 is fixedly connected to the steel pipe pile 4 / side wall lining 9 through the bottom longitudinal beams 3;

[0130] One end of the longitudinal beam anchor cable 31 is fixedly connected to the bottom longitudinal beam 3, and the other end is inserted into the rock mass 900 in a direction away from the first channel 61; a plurality of the longitudinal beam anchor cables 31 are arranged sequentially along the bottom longitudinal beam 3.

[0131] Preferably, the shaft 1 and the arch 2 are connected by a reinforcement zone 13;

[0132] Preferably, it also includes a plurality of sidewall anchor cables 91; one end of the sidewall anchor cable 91 is fixedly connected to the sidewall lining 9, and the other end is inserted into the rock mass 900 in a direction away from the second channel 62.

[0133] An embodiment of the present invention in an engineering application is as follows:

[0134] During the construction of a subway station using the arch method, the surrounding rock mass exhibited well-developed joints and fissures. Exploration revealed that the rock mass around the station was highly jointed, with most joints approaching micro-opening and remaining unfilled. Figure 10 As shown.

[0135] FLAC3D software was used to create a three-dimensional calculation model to simulate the station construction process, such as... Figure 11 As shown.

[0136] The preliminary range of values ​​for the joint parameters of the surrounding rock of the tunnel is shown in Table 1, which represents the horizontal division of the specific surrounding rock parameters.

[0137] Table 1 Parameter Level Division

[0138]

[0139] Twenty-five orthogonal design schemes and five uniform design parameter combinations were generated, and the parameters corresponding to each experimental scheme were substituted into FLAC. 3D Numerical calculations were performed, and the displacement and stress values ​​of the support structure during the excavation of the third longitudinal pilot tunnel were recorded to obtain the crown settlement A. Z C Z Bottom bulge value B Z The convergence value D in the horizontal direction Z The displacement and stress results calculated by the orthogonal parameter scheme and the uniform design parameter combination scheme are shown in Tables 2 and 3.

[0140] Using the data in Table 2 as training samples and the data in Table 3 as test samples, a decision tree model was constructed according to the above method to map the nonlinear relationship between rock mass joint parameters and their displacement and stress.

[0141] Table 2 Orthogonal schemes and calculated displacements

[0142]

[0143]

[0144] Table 3 Uniformity Test

[0145]

[0146]

[0147] Following the construction of the third longitudinal pilot tunnel, a back analysis of joint parameters was performed based on on-site monitoring results. The maximum number of iterations for the cuckoo algorithm was set to n = 200, the probability of nest discovery Pa = 0.25, and the number of nests N = 50. On-site data reduction A was obtained. Z It is 14.62mm, B Z It is 9.22mm, C Z The value of P1 is 13.73 mm, P2 is 168.76 kPa, and P3 is 131.61 kPa. The results of the back analysis are shown in Table 3.

[0148] Using the joint parameters obtained from back analysis, numerical simulation analysis was performed on the excavation of the fourth longitudinal pilot tunnel. The displacement changes at each monitoring point are shown in Table 5. The numerical simulation results were compared with the field monitoring data. As can be seen from Table 4-29, the maximum relative error between the two methods is 4.58%, verifying the accuracy of the back analysis results.

[0149] Table 4. Results of back analysis of surrounding rock parameters

[0150]

[0151] Table 5. Results of back analysis of surrounding rock parameters

[0152]

[0153] Table 6. Back-analysis calculation results and field monitoring results

[0154]

[0155] Figure 12-14 The results show how six parameters of the RF-CS (Cuckoo-Optimized Random Forest) algorithm change with the number of iterations. It can be seen that at the beginning of the iterations, these parameters are far from the optimal solution and fluctuate. As the number of iterations increases, these parameters tend to the optimal solution and remain stable when the number of iterations reaches 22. The results indicate that the optimal solution is obtained when the number of iterations reaches 22, demonstrating that the optimization process has good convergence.

[0156] This invention solves the problems of reducing the impact of station construction on surrounding existing structures and the limited construction site in densely built-up urban areas during the construction of urban subway stations. By setting up vertical shafts and excavating horizontal channels at the bottom of the shafts as the foundation working face for the excavation of the entire station, the required area of ​​the construction site is effectively reduced. At the same time, by setting up the primary lining of the shafts, i.e., the secondary lining of the shafts, i.e., the multi-layer support of the arch roof by setting up the outer primary support, the inner primary support, and the arch secondary lining, as well as the setting of longitudinal beam anchor cables and side wall anchor cables, the support structure effectively ensures the supporting effect of the rock mass.

[0157] Meanwhile, since the station construction process involves traversing unfavorable rock masses (joint surfaces, faults, and interlayers), the impact of these unfavorable rock masses on construction has been fully considered. The designed support structure can fully reflect the characteristics of the jointed rock mass, and the design and dynamic adjustment of the support structure are based on the influence of joint parameters.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A support method for a tunnel-excavated railway station in jointed rock mass, characterized in that, Includes the following steps: S1: Excavate a vertical shaft from the ground down into the rock mass (1); S2: Excavate a horizontal passage (28) from the bottom of the shaft; S3: Excavate a first longitudinal guide tunnel (281) and a second longitudinal guide tunnel (282) in the transverse passage. The excavation direction of the first longitudinal guide tunnel (281) and the second longitudinal guide tunnel (282) is perpendicular to the axis of the vertical shaft. S4: Steel pipe piles (4) are constructed below the first longitudinal guide tunnel (281) and the second longitudinal guide tunnel (282) respectively, so as to drive the steel pipe piles into the rock mass (900) in a vertically downward direction; S5: Along the excavation direction of the first longitudinal guide tunnel (281), excavate the third longitudinal guide tunnel (283) and the fourth longitudinal guide tunnel (284) in the transverse passage (28); The third longitudinal guide tunnel (283) and the fourth longitudinal guide tunnel (284) form the initial support (15) of the shaft with the shaft wall. S6: Concrete backfilling is carried out on the first longitudinal guide tunnel (281) and the second longitudinal guide tunnel (282) in the direction away from the rock mass (900) to form a concrete backfill layer (285). S7: On the side of the concrete backfill layer (285), the third longitudinal guide tunnel (283) and the fourth longitudinal guide tunnel (284) away from the rock mass, an outer initial support (21) is set in the direction away from the rock mass (900); S8: On the side of the outer primary support (21) away from the rock mass, the inner primary support (22) and the arch secondary lining (23) are constructed in sequence, and the outer primary support (21), the inner primary support (22), and the arch secondary lining (23) together form the arch top; S9: Construction of the bottom longitudinal beam (3) is carried out at the bottom end of the arch, and concrete is poured at the connection between the bottom end of the arch and the rock mass; S10: Construction of longitudinal beam anchor cable (31) is carried out at the end of the bottom of the arch to drive the longitudinal beam anchor cable (31) into the rock mass (900) direction. S11: The shaft is constructed in sequence along the direction away from the rock mass (900) for the initial lining (11) and the secondary lining (12) to reinforce the shaft; S12: Construction of a reinforcement zone (13) at the connection between the arch and the shaft; so that the arch and the initial lining (11) and the secondary lining (12) of the shaft are connected through the reinforcement zone; S13: Continue excavating the rock mass below the arch to form the station passage (100). S14: Construction of the initial lining (9) of the side wall is carried out below the ends on both sides of the bottom of the arch; the initial lining (9) of the side wall is set on the side of the steel pipe pile (4) away from the rock mass (900); and the side wall anchor cable (91) is driven from the initial lining (9) of the side wall towards the rock mass. S15: Construction of the invert arch secondary lining (7) at the bottom of the station passage (100); the two ends of the invert arch secondary lining (7) are respectively connected to the bottom of the side wall primary lining (9) on both sides; S16: A station structure middle plate (6) is horizontally installed above the invert arch secondary lining (7); the two ends of the station structure middle plate (6) are respectively connected to the side wall primary lining (9) on both sides; S17: Construction of the platform layer structural column (8) is carried out between the middle plate of the station structure and the secondary lining of the inverted arch. The top of the platform layer structural column (8) is connected to the middle plate (6) of the station structure, and the bottom is connected to the secondary lining of the inverted arch (7).

2. The support method for a tunnel-excavated railway station in jointed rock mass according to claim 1, characterized in that, The thickness of the arch (2), the length of the longitudinal beam anchor cable (31), the distance between two longitudinal beam anchor cables (31), the length of the steel pipe pile (4), the distance between two steel pipe piles (4), the length of the side wall anchor cable (91), the distance between two side wall anchor cables (91), and the number of side wall anchor cables are all calculated based on the joint parameters of the rock mass during the construction of the station.

3. The support method for a tunnel-excavated railway station in jointed rock mass according to claim 2, characterized in that, The joint parameters of the rock mass include: joint cohesion, joint expansion angle, joint friction angle, joint tensile strength, joint dip direction, and joint dip angle.

4. The support method for a tunnel-excavated railway station in jointed rock mass according to claim 2, characterized in that, The method for obtaining joint parameters of the rock mass during the station construction process is as follows: S101: Determine the range of joint parameters for the rock mass based on the initially determined surrounding rock grade; S102: Using orthogonal design and uniform design methods, obtain the combination schemes of joint parameters of rock masses with several orthogonal designs and the combination schemes of joint parameters of rock masses with several uniform designs; S103: Establish a numerical calculation model for the tunnel excavation of the jointed rock mass; and obtain the crown settlement displacement, arch waist convergence displacement, and crown structural stress based on the combination scheme of the joint parameters of the orthogonally designed rock mass and the combination scheme of the joint parameters of the uniformly designed rock mass. S104: Based on the random forest algorithm, the crown settlement displacement, the waist convergence displacement, and the crown structural stress are taken as inputs, and the joint parameters of the rock mass are taken as outputs, in order to obtain an optimized random forest algorithm. S105: Based on the optimized random forest algorithm and the range of values ​​for the joint parameters of the rock mass, obtain the optimal joint parameters of the rock mass, i.e., the joint parameters of the rock mass during the station construction process; S106: Based on the joint parameters of the optimal rock mass, provide guidance on the construction plan for the tunnel excavation of the jointed rock mass station.

5. The support structure of the support method for a tunnel-excavated station in jointed rock mass according to any one of claims 1 to 4, characterized in that, include: Shaft (1), arch (2), several steel pipe piles (4), station structure middle plate (6), inverted arch secondary lining (7), platform layer structure column (8), two side wall initial linings (9). The shaft (1) is set vertically downwards from the ground; the shaft (1) includes a primary lining (11) and a secondary lining (12); the primary lining and the secondary lining are set sequentially into the shaft along the direction away from the rock mass; The arch (2) is located at the bottom of the shaft (1) and extends in a direction perpendicular to the axis of the shaft (1), with the top of the arch (2) abutting against the rock mass; The arch (2) includes an outer primary support (21), an inner primary support (22), and an arch lining (23); the outer primary support (21), the inner primary support (22), and the arch lining (23) are stacked sequentially in a downward direction along the axis of the shaft (1); the surface of the outer primary support (21) away from the inner primary support (22) abuts against the rock mass (900); The inverted arch lining (7) is located below the arch top (2); and its bottom abuts against the rock mass (900); The initial lining of the side wall (9) is set between the second lining of the inverted arch (7) and the arch (2), and the top of the initial lining of the side wall (9) is fixedly connected to one end of the bottom of the arch (2), and the bottom of the initial lining of the side wall (9) is fixedly connected to the corresponding end of the second lining of the inverted arch (7). The station structure plate (6) is horizontally positioned between the arch (2) and the inverted arch lining (7), and the station structure plate (6) is fixedly connected to the two side wall linings (9) respectively. A first passage (61) is formed between the middle plate (6) of the station structure and the arch (2); the middle plate (6) of the station structure, the initial lining of the side wall (9) and the secondary lining of the inverted arch (7) together form a second passage (62). The platform layer structure column (8) is located between the arch lining (7) and the station structure middle plate (6), with one end fixedly connected to the bottom of the station structure middle plate (6) and the other end fixedly connected to the top of the arch lining (7). The steel pipe pile (4) is fixedly installed in the rock mass (900) on the side of the side wall lining (9) away from the second channel (62), and one end of it is fixedly connected to one end of the bottom of the arch (2), and the other end extends vertically downward to the bottom of the invert arch lining (7); a number of the steel pipe piles (4) are sequentially installed along one end of the bottom of the arch (2).

6. The support structure of the support method for a tunnel-excavated station in jointed rock mass according to claim 5, characterized in that, It also includes two bottom longitudinal beams (3) and several longitudinal beam anchor cables (31); one end of the bottom of the arch (2) is fixedly connected to the steel pipe pile (4) / side wall lining (9) through the bottom longitudinal beams (3); One end of the longitudinal beam anchor cable (31) is fixedly connected to the bottom longitudinal beam (3), and the other end is inserted into the rock mass (900) in a direction away from the first channel (61); a plurality of the longitudinal beam anchor cables (31) are arranged sequentially along the bottom longitudinal beam (3).

7. The support structure of the support method for a tunnel-excavated station in jointed rock mass according to claim 5, characterized in that, The shaft (1) and the vault (2) are connected by a reinforcement zone (13).

8. The support structure of the support method for a tunnel-excavated station in jointed rock mass according to claim 5, characterized in that, It also includes several sidewall anchor cables (91); one end of the sidewall anchor cable (91) is fixedly connected to the sidewall lining (9), and the other end is inserted into the rock mass (900) in a direction away from the second channel (62).

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