Safe clear distance calculation method for small-clear-distance shallow-buried parallel shield tunnel

Abstract

The invention discloses a small-clear-distance shallow-buried parallel shield tunnel safety clear distance calculation method, and relates to the technical field of tunnel and underground engineering, and the method comprises the following steps: calculating a small-clear-distance shallow-buried parallel shield tunnel safety clear distance based on a small-clear-distance shallow-buried parallel shield tunnel surrounding rock pressure calculation mode and a middle partition bearing column M-C shear failure criterion; a small-clear-distance shallow-buried parallel shield safety clear distance theoretical judgment model suitable for different stratums is constructed, and a safety clear distance judgment formula is deduced; a stratum comprehensive calculation friction angle phi c and a tunnel excavation vertical sliding surface friction angle theta are determined according to engineering stratum parameters (cohesive force c, an internal friction angle phi and a weight gamma of different types of soil of each layer above the tunnels), and the safe clear distance between the two tunnels can be calculated by substituting into a theoretical judgment formula in combination with the tunnel burial depth h and the diameter D. In addition, parameter sensitivity analysis can be carried out through a theoretical model, and the optimal parameter range of the reinforced stratum is obtained when the auxiliary stratum reinforcement mode is adopted for small-clear-distance shallow-buried parallel shield construction.

Description

Technical Field

[0001] The invention relates to the technical field of tunnels and underground engineering, and in particular to a method for calculating the safe clearance of a shallow parallel shield tunnel with a small clearance. Background Art

[0002] When constructing a double-line shield tunnel in a limited underground space, the clearance design between the two lines must consider not only the safety issues of the interaction during the excavation process, but also the economic and low-carbon effects, accurately shorten the distance between the two lines, and make full use of the underground space, thereby saving land resources. At present, the safe clearance of double-line parallel tunnels is relatively extensive, and there is no theoretical calculation applicable to different strata and different tunnel conditions. Although machine learning obtains quantitative data, it does not consider the impact of specific stratum parameters and data training errors on it. Therefore, it is necessary to invent a safe clearance calculation method for shallow parallel shield tunnels with small clearance, which can determine the safe and accurate distance between the two parallel tunnels through theory. Summary of the invention

[0003] The purpose of the present invention is to provide a method for calculating the safe clearance of a shallow parallel shield tunnel with a small clearance in order to achieve the purpose of making the best use of underground space while ensuring the safety of the tunnel structure.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for calculating the safe clearance of shallow parallel shield tunnels with small clearance, based on the surrounding rock pressure calculation mode of shallow parallel shield tunnels with small clearance and the shear failure criterion of the MC of the intermediate bearing columns between tunnels, a theoretical judgment model for the safe clearance of shallow parallel shield tunnels with small clearance is constructed, a judgment formula for the safe clearance is derived, and the safe clearance between the two tunnels is calculated by substituting the judgment formula into the parameters; the optimal range of the stratum reinforcement parameters is quantified through the theoretical model.

[0005] As a further solution of the present invention: based on the surrounding rock pressure calculation mode of the shallow parallel shield tunnel with small clearance, the relevant parameters required by the safe clearance judgment formula are calculated, and the calculation formula of the relevant parameters is as follows:

[0006] in, φ c Calculate friction angle for the formation; β 1 is the rupture angle of the inner side of the leading tunnel; λ 2 ՛ When the following tunnel is excavated, the lateral pressure coefficient inside the leading tunnel; β 2 is the rupture angle of the inner side of the rear tunnel; T2՛ is the frictional resistance exerted by the soil inside the leading tunnel on the soil column of the vault; T2 is the frictional resistance exerted by the soil inside the rear tunnel on the soil column of the arch; c is the cohesion of each layer of different types of soil above the tunnel; φ is the internal friction angle; γ is severe; θ is the friction angle of the vertical sliding surface of tunnel excavation; h is the tunnel depth; D is the tunnel diameter.

[0007] As a further solution of the present invention: Based on the shear failure criterion of the MC bearing column between the tunnels, the calculation formulas for the maximum principal stress and the minimum principal stress of the soil are as follows:

[0008] σ1 is the maximum principal stress of the soil, σ3 is the minimum principal stress of the soil, which is manifested as the lateral horizontal pressure provided by the supporting structure of the subsequent tunnel.

[0009] As a further solution of the present invention: analyzing the critical condition for preventing the septum bearing column from reaching the breaking stress, that is, when the actual stress σ0 of the septum bearing column is not greater than the maximum principal stress σ1 under its limit equilibrium condition, as shown in the following formula: .

[0010] As a further solution of the present invention: construct a theoretical model of safe clearance of shallow parallel shield tunnels with small clearance, and then derive a calculation formula for safe clearance of shallow parallel shield tunnels with small clearance. The derivation process is as follows: The longitudinal overburden pressure per unit length of the middle septum bearing column during the subsequent tunnel excavation is P: ; The stress per unit length of the septum bearing column is: ; make

[0011] but can be written as:

[0012] The practical solution of the equation X is:

[0013] Substitute it into , Thus, the safe clearance judgment formula is obtained: .

[0014] As a further solution of the present invention: the stratum parameters contained in the discrimination formula: the cohesion c, internal friction angle φ, and gravity γ of each layer of different types of soil above the tunnel are determined according to different stratum properties.

[0015] As a further solution of the present invention: a safety clearance discrimination formula is used to perform parameter sensitivity analysis, thereby obtaining an optimal range of formation reinforcement parameters.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Based on the surrounding rock pressure calculation mode of small-clearance shallow-buried parallel shield tunnels and the shear failure criterion of the intermediate bearing column MC, the present invention constructs a theoretical judgment model for the safe clearance of small-clearance shallow-buried parallel shields applicable to different strata, and derives a safe clearance judgment formula; according to the engineering stratum parameters (cohesion c, internal friction angle φ, and gravity γ of each layer of different types of soil above the tunnel), the stratum comprehensive calculation friction angle φc and the friction angle θ of the vertical sliding surface of the tunnel excavation are determined, and combined with the tunnel burial depth h and diameter D, the safe clearance of the two tunnels can be calculated by substituting them into the theoretical judgment formula. In addition, the parameter sensitivity analysis can be performed through the theoretical model to obtain the optimal parameter range of the reinforced stratum when the small-clearance shallow-buried parallel shield construction adopts the auxiliary reinforcement stratum method. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Derivation and calculation process of safe clearance calculation method for shallow parallel shield tunnels with small clearance; Figure 2 It is a calculation model for the confining pressure of shallow parallel shield tunnels with small clearance; Figure 3 It is a theoretical model for safe clearance of shallow parallel shield tunnels with small clearance. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] See also Figure 1-Figure 3 In an embodiment of the present invention, a method for calculating the safe clearance of a shallow parallel shield tunnel with a small clearance is provided, comprising: constructing a theoretical judgment model for the safe clearance of a shallow parallel shield tunnel with a small clearance applicable to different strata based on the surrounding rock pressure calculation mode of the shallow parallel shield tunnel with a small clearance and the shear failure criterion of the intermediate bearing column MC, and deriving a safe clearance judgment formula: ; Determine the comprehensive calculation friction angle φ of the stratum according to the engineering stratum parameters (cohesion c, internal friction angle φ, and gravity γ of each layer of different types of soil above the tunnel) c The vertical sliding surface friction angle θ, combined with the tunnel burial depth h and tunnel diameter D, can be substituted into the theoretical judgment formula to calculate the safe clearance between the two tunnels. In addition, the parameter sensitivity analysis can be performed through the theoretical model to obtain the optimal parameter range of the reinforced stratum when the small clearance parallel shield construction adopts the auxiliary reinforcement stratum method.

[0020] The derivation process of the discriminant formula is as follows: Based on the calculation model of surrounding rock pressure of shallow parallel shield tunnels with small clearance, such as Figure 2 As shown, the relevant parameters required by the theoretical model of safe clearance can be calculated. The calculation formula of relevant parameters is as follows:

[0021] φ c Calculate friction angle for the formation; β 1 is the rupture angle of the inner side of the leading tunnel; λ 2 ՛ When the following tunnel is excavated, the lateral pressure coefficient inside the leading tunnel; β 2 is the rupture angle of the inner side of the rear tunnel; T2՛ is the frictional resistance exerted by the soil inside the leading tunnel on the soil column of the vault; T2 is the frictional resistance exerted by the soil inside the rear tunnel on the soil column of the arch.

[0022] Based on the MC shear failure criterion of the tunnel partition bearing column, the formula is as follows:

[0023] but

[0024] σ1 is the maximum principal stress of the soil, σ3 is the minimum principal stress of the soil, which is manifested as the lateral horizontal pressure provided by the supporting structure of the subsequent tunnel.

[0025] Further analysis is performed to avoid the critical condition of the septum bearing column reaching the failure stress, that is, when the actual stress on the septum bearing column is not greater than the maximum principal stress under its limit equilibrium condition, as shown in the following formula: .

[0026] A theoretical model of safe clearance of shallow parallel shield tunnels with small clearance was constructed. Figure 3 As shown in Figure 2, the safe clearance calculation formula for shallow parallel shield tunnels with small clearance can be derived.

[0027] The longitudinal overburden pressure per unit length of the middle septum bearing column during the subsequent tunnel excavation is P:

[0028] The stress per unit length of the septum bearing column is:

[0029] make

[0030]

[0031] but It can be written as:

[0032] The practical solution of the equation X is

[0033] Substitute it into ,

[0034] Thus, the safe clearance judgment formula is obtained

[0035] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0036] In view of the defects and shortcomings of the prior art, an embodiment of the present invention provides a confining pressure calculation model for shallow parallel shield tunnels with small clearance and a shear failure criterion for the MC of the intermediate bearing columns, constructs a theoretical judgment model for the safe clearance of shallow parallel shield tunnels with small clearance, and derives a safe clearance judgment formula, which can be adapted to the safe clearance calculation of shallow parallel shield tunnels with small clearance in different strata.

[0037] The processing flow chart of a method for calculating the safe clearance of a shallow parallel shield tunnel with a small clearance provided by an embodiment of the present invention is shown in the attached figure. Figure 1 As shown, the processing steps include: Step S1: Define the engineering stratum parameters (c, φ, γ) and tunnel parameters (D, h). For example, the proposed double-line shield tunnel and stratum conditions are shown as follows.

[0038] <![CDATA[重度γ(KN / m 3 )]]> Cohesion c(KPa) Internal friction angle φ(°) Tunnel diameter D(m) Tunnel burial depth h(m) 18.65 22.76 17.35 6.2 11 Step S2: Calculate the parameters required for the discriminant formula.

[0039] Calculate the friction angle of the formation

[0040] The clay layer is grade VI, and the vertical sliding surface friction angle of tunnel excavation

[0041] Step S3: Substitute the relevant parameters into the discriminant formula.

[0042]

[0043] Calculation shows that L≥6.1m, that is, under the geological conditions and without any reinforcement measures, the distance between the two shallowly buried, small-clearance parallel shield tunnels with a tunnel diameter of 6.2m and a burial depth of 11m shall not be less than 6.1m.

[0044] in

[0045]

[0046] Step S4: When the stratum is reinforced under the condition that the engineering cost allows, the purpose is to reduce the distance between the two tunnels. This can be achieved by changing the friction angle φ and cohesion c in the stratum. Substituting them into the clearance judgment formula, the corresponding safety clearance L can be obtained. The degree of stratum parameters that need to be achieved after reinforcement and the corresponding safety clearance can be clearly determined, and the most cost-effective solution can be selected.

[0047] What has been described above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for calculating the safe clearance of shallow parallel shield tunnels with small clearance, characterized in that: Based on the surrounding rock pressure calculation model of small-clearance shallow-buried parallel shield tunnels and the MC shear failure criterion of the intermediate bearing column between tunnels, a theoretical judgment model for the safe clearance of small-clearance shallow-buried parallel shield tunnels is constructed, and the safe clearance judgment formula is derived. The safe clearance of the two tunnels is calculated by substituting the judgment formula into the parameters. The optimal range of formation reinforcement parameters is quantified through theoretical models.

2. The method for calculating the safe clearance of shallow parallel shield tunnels with small clearance according to claim 1 is characterized in that: Based on the surrounding rock pressure calculation model of small clearance shallow buried parallel shield tunnel, the relevant parameters required for the safe clearance judgment formula are calculated. The calculation formula of the relevant parameters is as follows: ； in, φ c Calculate friction angle for the formation; β 1 is the rupture angle of the inner side of the leading tunnel; λ 2 ՛ When the following tunnel is excavated, the lateral pressure coefficient inside the leading tunnel; β 2 is the rupture angle of the inner side of the rear tunnel; T2՛ is the frictional resistance exerted by the soil inside the leading tunnel on the soil column of the vault; T2 is the frictional resistance exerted by the soil inside the rear tunnel on the soil column of the arch; c is the cohesion of each layer of different types of soil above the tunnel; φ is the internal friction angle; γ is severe; θ is the friction angle of the vertical sliding surface of tunnel excavation; h is the tunnel depth; D is the tunnel diameter.

3. The method for calculating the safe clearance of shallow parallel shield tunnels with small clearance according to claim 1 is characterized in that: Based on the MC shear failure criterion of the tunnel intermediate bearing column, the calculation formulas for the maximum principal stress and the minimum principal stress of the soil are as follows: ； ； σ1 is the maximum principal stress of the soil, σ3 is the minimum principal stress of the soil, which is manifested as the lateral horizontal pressure provided by the supporting structure of the subsequent tunnel.

4. The method for calculating the safe clearance of shallow parallel shield tunnels with small clearance according to claim 1 is characterized in that: The critical condition for avoiding the septum bearing column from reaching the failure stress is analyzed, that is, when the actual stress σ0 of the septum bearing column is not greater than the maximum principal stress σ1 under its limit equilibrium condition, as shown in the following formula: .

5. The method for calculating the safe clearance of shallow parallel shield tunnels with small clearance according to claim 1 is characterized in that: A theoretical model of safe clearance of shallow parallel shield tunnels with small clearance is constructed, and then the calculation formula of safe clearance of shallow parallel shield tunnels with small clearance is derived. The derivation process is as follows: The longitudinal overburden pressure per unit length of the middle septum bearing column during the subsequent tunnel excavation is P: ； The stress per unit length of the septum bearing column is: ； make ； It can be written as: ； The practical solution of the equation X is: ； Substitute it into , Thus, the safe clearance judgment formula is obtained: 。 6. The method for calculating the safe clearance of shallow parallel shield tunnels with small clearance according to claim 1 is characterized in that: The judgment formula contains the formation parameters: cohesion c, internal friction angle φ, and gravity γ of each layer of different types of soil above the tunnel, which are determined according to different formation properties.

7. The method for calculating the safe clearance of shallow parallel shield tunnels with small clearance according to claim 1 is characterized in that: The safety clearance judgment formula is used to carry out parameter sensitivity analysis, and then the optimal range of ground reinforcement parameters is obtained.

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