A method for predicting torsional deformation of an existing tunnel caused by shield excavation

Abstract

The present application relates to the technical field of tunnel adjacent construction, and particularly relates to a method for predicting torsional deformation of an existing tunnel caused by shield excavation, which comprises the following steps: predicting and determining stratum loss rate according to geometric characteristics of the shield tunnel and construction factors; determining vertical spatial position and horizontal spatial angle between the existing tunnel and the new shield tunnel caused by shield excavation in the crossing area; calculating full cross-section deformation of the existing tunnel caused by shield excavation; and predicting cross-section torsional deformation and longitudinal uneven torsional deformation of the existing tunnel according to the full cross-section deformation of the existing tunnel. The present application has the advantages that: it can realize the prediction of vertical and torsional deformation of the tunnel at the same time, and more comprehensively analyzes the deformation of the tunnel caused by shield excavation; the calculation method is more simple and has high prediction accuracy, and the structural deformation response of the existing tunnel caused by tunnel excavation can be obtained simply and quickly, which can guarantee the shield crossing the existing tunnel and other constructions.

Description

Technical Field

[0001] This invention relates to the field of tunnel close-in construction technology, and in particular to a method for predicting torsional deformation of existing tunnels caused by shield tunneling. Background Technology

[0002] To address the increasing density of urban populations and the urgent need for urban rail transit, underground space has developed rapidly. Underground tunnels are widely used in public tunnels, pedestrian passages, highway tunnels, and rectangular shield tunnels. During long-term operation, excessive longitudinal settlement inevitably occurs in tunnels, affecting their safety—a problem that has attracted widespread attention. Besides common settlement patterns, irregularly shaped tunnels subjected to asymmetric loads and deformations are particularly susceptible to uneven longitudinal torsion due to their irregular cross-sections. While research on the impact of cross-sectional torsion on tunnel structures is limited, it warrants attention.

[0003] Underground tunnels, subjected to asymmetric loads such as those from shield excavation, exhibit asymmetric and constantly changing characteristics, making them highly susceptible to cross-sectional torsional deformation and longitudinal relative torsion. This is extremely detrimental to the structural stress and operational safety of the tunnel. Currently, there is limited research on monitoring technologies for tunnel torsion.

[0004] Therefore, there is an urgent need to propose a method for predicting the torsional deformation of existing tunnels caused by shield tunneling, so as to assess the torsional situation of the tunnel and avoid safety risks. Summary of the Invention

[0005] The purpose of this invention is to provide a method for predicting torsional deformation of existing tunnels caused by shield tunneling, based on the shortcomings of the prior art. This method can quickly and easily obtain the deformation response of existing tunnel structures caused by tunnel excavation, providing a reference for adjusting shield tunneling construction parameters and thus achieving better construction control.

[0006] The objective of this invention is achieved through the following technical solutions:

[0007] A method for predicting torsional deformation of existing tunnels caused by shield tunneling excavation, characterized by the following steps:

[0008] The ground loss rate is predicted and determined based on the geometric characteristics of the shield tunnel and construction factors.

[0009] Determine the vertical spatial position and horizontal spatial angle between the existing tunnel and the newly constructed shield tunnel excavated within the crossing area;

[0010] Calculate the full-section deformation of the existing tunnel caused by shield excavation;

[0011] Based on the overall cross-sectional deformation of the existing tunnel, predict the cross-sectional torsional deformation and longitudinal uneven torsional deformation of the existing tunnel.

[0012] The formation loss rate is predicted and determined using the following formula:

[0013] ;

[0014] Among them, V loss The formation loss rate is R, the diameter of the new tunnel is g, and the calculated gap between the shield and the existing tunnel can be expressed as:

[0015] In the formula, G p It is the combined gap between the shield and the existing tunnel, and k is a correction coefficient.

[0016] Determine the vertical distance h between the existing tunnel and the newly built shield tunnel within the crossing area, as well as the angle between the longitudinal axis of the existing tunnel and the excavation face of the newly built shield tunnel, i.e., the horizontal spatial angle α.

[0017] The deformation at any point within the entire cross-section of the existing tunnel caused by shield excavation is as follows:

[0018] ;

[0019] Where x represents the longitudinal direction of the tunnel, with the origin at the ground surface at the center of the excavation face, and positive at the front of the tunnel; y represents the transverse direction of the tunnel, with the origin at the center of the excavation face, and positive to the right of the tunnel's direction of travel; z represents the burial depth, with the origin at the ground surface directly above the excavation face, and positive downwards; H represents the burial depth of the newly constructed tunnel axis; v represents the Poisson's ratio of the soil; V loss R is the formation loss rate; R is the diameter of the newly constructed tunnel.

[0020] After obtaining the deformation at any point of the existing tunnel, the torsional deformation of its arbitrary cross-section is obtained by the following expression:

[0021] ;

[0022] Where w1(x,y,z) is the deformation of the front corner of the existing tunnel cross-section bottom plate; It is the deformation of the rear corner of the existing tunnel cross-section bottom plate, and D is the width of the existing tunnel.

[0023] After obtaining the torsional deformation of any cross-section of the existing tunnel, the longitudinal non-uniform torsional deformation of its cross-section is obtained by the following expression:

[0024] ;

[0025] Where ΔL is the distance between adjacent sections.

[0026] When the existing tunnel is a rectangular tunnel, it is treated as a closed thin-walled component. The relationship between torsion and shear strain, and the relationship between torsion angle and torsion, of the closed thin-walled component are determined by the following formula:

[0027] ;

[0028] in, It is the maximum shear stress on the cross section; It is the torque on the cross section; Ω is twice the area enclosed by the tunnel cross section; It is the minimum value of the cross-sectional wall thickness; It is the length of the component along the axis. The increment of the torsion angle; It is the infinitesimal length of the component along the axis; t is the arc length of the infinitesimal element on the neutral line of the cross section; t is the thickness of the tunnel cross section at point s; and G is the shear modulus of the concrete. The above formula is used to determine whether there is a risk of cracking in the concrete.

[0029] The advantages of this invention are: it can simultaneously predict both vertical and torsional deformation of tunnels, providing a more comprehensive analysis of the deformation caused by shield excavation; the calculation method is simpler and the prediction accuracy is higher, enabling quick and easy acquisition of the deformation response of existing tunnel structures caused by tunnel excavation, thus providing a guarantee for shield tunneling through existing tunnels and other construction projects. Attached Figure Description

[0030] Figure 1 The structural response diagram of a shield tunnel to an adjacent tunnel;

[0031] Figure 2 A spatial relationship diagram of the newly built tunnel and the existing tunnel;

[0032] Figure 3 This is a decomposed view of the deformation of an existing tunnel.

[0033] Figure 4 An analysis diagram of an existing rectangular tunnel torsional deformation example;

[0034] Figure 5 This is an analysis diagram of an example of longitudinal uneven torsional deformation in an existing rectangular tunnel. Detailed Implementation

[0035] The following examples further illustrate the features and other related characteristics of the present invention in detail, to facilitate understanding by those skilled in the art:

[0036] Example: The method for predicting torsional deformation of existing tunnels caused by shield tunneling in this example is used to predict the torsional deformation of existing tunnels caused by shield tunneling when shield tunneling is close to existing tunnels, so as to assess the structural impact of shield tunneling on existing tunnels and ensure construction safety.

[0037] This embodiment takes a shield tunnel orthogonally passing under an existing rectangular tunnel as an example, such as... Figure 1 As shown, the steps for predicting the torsional deformation of this rectangular tunnel are as follows:

[0038] Data on the geometric characteristics of the shield tunnel and shield excavation parameters, including the diameter of the shield and tunnel, and the grouting volume, are collected. Based on actual cases, the ground loss rate of the construction section can be predicted using the following formula:

[0039] (1);

[0040] Where R is the diameter of the newly constructed tunnel, taken as 3.3m; gg is the calculated gap between the shield and the tunnel, taken as 10mm, and g can be expressed as: (2); where G p is the combined gap between the shield and the existing tunnel, taken as 10cm; k is a correction factor for the geometric gap, taking into account grouting, the calculated gap between the shield and the tunnel, and construction factors, taken as 0.1.

[0041] The vertical distance between the existing tunnel and the newly built shield tunnel in the traversing area is h=5m, and the relative angle α=0°, as shown below. Figure 2 As shown, Figure 2 (a) in the figure shows the planar relationship between the newly built shield tunnel and the existing tunnel; Figure 2 (b) in the figure shows the cross-sectional positional relationship between the newly built shield tunnel and the existing tunnel.

[0042]

[23] Ignoring cross-sectional distortion, the deformation of the disturbed ramp cross-section can be classified into two categories: vertical deformation w and torsional deformation φ, such as Figure 3 As shown. Assuming the soil and tunnel are closely connected, the tunnel displacement can be represented by the soil displacement. The deformation of any point in the existing tunnel caused by shield tunnel excavation is:

[0043] (3);

[0044] in x y is the longitudinal direction of the tunnel, with the origin at the ground surface at the center of the excavation face, and positive at the front of the tunnel; y is the transverse direction of the tunnel, with the origin at the center of the excavation face, and positive to the right of the tunnel's direction of travel; z is the burial depth direction, with the origin at the ground surface directly above the excavation face, and positive downwards; H=10m; v=0.25.

[0045] After obtaining the deformation at any point in the tunnel, the torsional deformation of the tunnel cross-section can be further obtained, and its expression is as follows:

[0046] (4);

[0047] Where w1(x,y,z) is the deformation of the front corner of the existing tunnel cross-section bottom plate; This represents the deformation at the rear corner of the existing tunnel cross-section floor slab, where D is the width of the existing tunnel, taken as 9m. The calculation results are as follows: Figure 4 As shown.

[0048] After obtaining the torsional deformation of any cross-section of the tunnel, the longitudinal non-uniform torsional deformation of the tunnel cross-section can be further obtained, and its expression is as follows:

[0049] (5);

[0050] Where ΔL is the distance between adjacent sections, which can be set to a unit length of 1m, or solved using a limit method. The calculation results are as follows: Figure 5 As shown.

[0051] A rectangular ramp can be considered a closed thin-walled component. Based on the torsional characteristics of closed thin-walled components, the tunnel concrete is in a bidirectional tensile-compressive state. Therefore, when the shear stress... Concrete cracking occurs. The relationships between torque and shear strain, and between torsional angle and torque, for closed thin-walled members are as follows:

[0052] (6);

[0053] in, It is the maximum shear stress on the cross section; It is the torque on the cross section; Ω is twice the area enclosed by the tunnel cross section; It is the minimum value of the cross-sectional wall thickness; It is the length of the component along the axis. The increment of the torsion angle; It is the infinitesimal length of the component along the axis; is the arc length of the infinitesimal element on the neutral line of the cross-section; t is the thickness of the tunnel cross-section at point s; and G is the shear modulus of the concrete. Calculations yield... Therefore, it can be determined that the concrete does not pose a risk of torsional shear cracking.

[0054] Although the above embodiments have been described in detail with reference to the concept and embodiments of the present invention, those skilled in the art will recognize that various improvements and modifications can still be made to the present invention without departing from the scope of the claims, and therefore will not be elaborated here.

Claims

1. A method for predicting torsional deformation of existing tunnels caused by shield tunneling, characterized in that: The method includes the following steps: The ground loss rate is predicted and determined based on the geometric characteristics of the shield tunnel and construction factors. Determine the vertical spatial position and horizontal spatial angle between the existing tunnel and the newly constructed shield tunnel excavated within the crossing area; Calculate the full-section deformation of the existing tunnel caused by shield excavation; Predict the cross-sectional torsional deformation and longitudinal uneven torsional deformation of the existing tunnel based on the overall cross-sectional deformation of the existing tunnel. The formation loss rate is predicted and determined using the following formula: ； Among them, V loss The formation loss rate is R, the diameter of the new tunnel is g, and the calculated gap between the shield and the existing tunnel can be expressed as: In the formula, G p The distance between the shield and the existing tunnel is the combined gap, and k is a correction coefficient; Determine the vertical distance h between the existing tunnel and the newly built shield tunnel within the crossing area, as well as the angle between the longitudinal axis of the existing tunnel and the excavation face of the newly built shield tunnel, i.e., the horizontal spatial angle α. The deformation at any point within the entire cross-section of the existing tunnel caused by shield excavation is as follows: ； Where x represents the longitudinal direction of the tunnel, with the origin at the ground surface at the center of the excavation face, and positive at the front of the tunnel; y represents the transverse direction of the tunnel, with the origin at the center of the excavation face, and positive to the right of the tunnel's direction of travel; z represents the burial depth, with the origin at the ground surface directly above the excavation face, and positive downwards; H represents the burial depth of the newly constructed tunnel axis; v represents the Poisson's ratio of the soil; V loss R is the formation loss rate; R is the diameter of the newly constructed tunnel; After obtaining the deformation at any point of the existing tunnel, the torsional deformation of its arbitrary cross-section is obtained by the following expression: ； Where w1(x,y,z) is the deformation of the front corner of the existing tunnel cross-section bottom plate; It is the deformation of the rear corner of the existing tunnel cross-section bottom plate, and D is the width of the existing tunnel; After obtaining the torsional deformation of any cross-section of the existing tunnel, the longitudinal non-uniform torsional deformation of its cross-section is obtained by the following expression: ； Where ΔL is the distance between adjacent sections.

2. The method for predicting torsional deformation of existing tunnels caused by shield tunneling according to claim 1, characterized in that: When the existing tunnel is a rectangular tunnel, it is treated as a closed thin-walled component. The relationship between torsion and shear strain, and the relationship between torsion angle and torsion, of the closed thin-walled component are determined by the following formula: ； in, It is the maximum shear stress on the cross section; It is the torque on the cross section; Ω is twice the area enclosed by the tunnel cross section; It is the minimum value of the cross-sectional wall thickness; It is the length of the component along the axis. The increment of the torsion angle; It is the infinitesimal length of the component along the axis; t is the arc length of the infinitesimal element on the neutral line of the cross section; t is the thickness of the tunnel cross section at point s; and G is the shear modulus of the concrete. The above formula can be used to determine whether there is a risk of cracking in the concrete.

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