Method for estimating vertical load when shield tunnel passes through inclined composite stratum

Abstract

The invention discloses a method for estimating a vertical load when a shield tunnel passes through an inclined compound stratum. The method comprises the following steps: 1, constructing a database according to basic parameters of the shield tunnel and geometric parameters and physical and mechanical property parameters of the inclined compound stratum; 2, calculating an initial stress and a principal stress deflection angle when the stratum under the inclined earth surface is only subjected to gravity, and calculating an inclination angle after the slip plane above the tunnel is deflected; 3, establishing a geometric model, importing the geometric model into the excavation influence width of the shield tunnel, and calculating the excavation influence width of the shield tunnel based on a broken line slip plane method; 4, initializing the geometric model to form a calculation model; 5, solving the vertical stress of the upper half part of the calculation model; and solving the vertical load of the inclined homogeneous stratum tunnel vault for the lower half part of the calculation model. In the vertical load estimation of the shield tunnel, the difference between the property of principal stress deflection of the inclined stratum and the form of the slip plane in the composite stratum is added, and the defects in the prior art are overcome.

Description

Technical Field

[0001] The invention relates to the technical field of computer-aided design, and in particular to a method for estimating vertical load when a shield tunnel passes through an inclined composite stratum. Background Art

[0002] Composite strata refer to a special stratum condition formed by the staggered distribution of different strata with greatly different physical and mechanical properties. It is more common in South China, Southwest my country, Southeast China and other regions. Currently, the number of ultra-large diameter shield tunnels passing through composite strata with soft upper part and hard lower part is gradually increasing.

[0003] Due to the different sliding surface morphology, the external load distribution of the shield tunnel in composite strata is quite different from that of the shield tunnel in homogeneous strata, which leads to the fact that the stress and deformation law of the tunnel structure is also different from that of the homogeneous strata.

[0004] Therefore, establishing an external load estimation model is of great significance to the design and construction of ultra-large diameter shield tunnels in composite strata.

[0005] The existing models mainly study the shape of the slip surface above the tunnel excavation surface, but there are relatively few studies on the slip surfaces on both sides of the tunnel section.

[0006] Moreover, the traditional tunnel load calculation model is mainly aimed at homogeneous strata and horizontal strata. For composite strata, the stratum parameters are directly weighted averaged, which is difficult to reflect the differences in the physical and mechanical properties of different strata in the composite strata.

[0007] Therefore, how to incorporate the properties of the principal stress deflection of the inclined strata and the differences in the slip surface morphology in the composite strata into the vertical load estimation when the shield tunnel passes through the inclined composite strata has become a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0008] In view of the above-mentioned defects of the prior art, the present invention provides a method for estimating the vertical load when a shield tunnel passes through an inclined composite stratum. The purpose of the present invention is to incorporate the properties of the principal stress deflection of the inclined stratum and the differences in the slip surface morphology in the composite stratum into the vertical load estimation when the shield tunnel passes through the inclined composite stratum, so as to provide a reference for the design and construction of ultra-large diameter shield tunnels passing through the upper soft and lower hard composite strata.

[0009] To achieve the above object, the present invention discloses a method for estimating vertical load when a shield tunnel passes through an inclined composite stratum; the method is characterized by comprising the following steps:

[0010] Step 1: extract basic parameters of the shield tunnel and geometric parameters and physical and mechanical property parameters of the inclined composite stratum based on the survey data of the shield tunnel passing through the inclined composite stratum, and after data standardization, build a database in the shield machine PLC system;

[0011] Step 2: In the shield machine PLC system, the initial stress and the principal stress deflection angle of the stratum under the inclined surface when only subjected to gravity are calculated by the deflection angle calculation module, and the inclination angle of the slip surface above the tunnel after deflection is calculated;

[0012] Step 3: after establishing a geometric model of the shield tunnel passing through the inclined composite stratum, the geometric model is imported into the excavation influence width of the shield tunnel, and then the excavation influence width of the shield tunnel is calculated based on the broken line sliding surface method;

[0013] Step 4: Import the standard data in the database and the geometric model into the model initialization module in the PLC system of the shield machine to initialize and form a calculation model;

[0014] Step 5: For the upper part of the calculation model, a differential equation for vertical stress is established using equilibrium conditions, and the boundary conditions are substituted to solve the vertical stress; for the lower part of the calculation model, the vertical load on the vault of the tunnel in the inclined homogeneous stratum is solved according to the vertical force balance.

[0015] Preferably, in step 1, the basic parameters of the shield tunnel in the database include the outer diameter of the lining, the buried depth of the vault and the ground overload, the geometric parameters of the inclined composite strata include the inclination angle of the strata and the thickness of each stratum, and the physical and mechanical property parameters of the inclined composite strata include the density, internal friction angle, cohesion and Poisson's ratio of each stratum.

[0016] Preferably, in step 2, the working steps of the deflection angle calculation module are as follows:

[0017] Step 2.1, initial stress calculation; specifically: calculate the initial stress of the inclined subsurface stratum of the inclined composite stratum when it is subjected only to gravity, and the calculation formula is as follows:

[0018]

[0019] Among them, σ x , σ y and τ xy are the horizontal stress, vertical stress and shear stress of the point in the soil where the initial stress needs to be calculated, γ is the soil weight, β is the stratum inclination, μ is the Poisson's ratio of the soil, and y is the vertical distance from the point in the soil where the initial stress needs to be calculated to the inclined surface;

[0020] Step 2.2, principal stress deflection angle calculation: specifically, calculating the principal stress deflection angle of the inclined composite formation, the calculation formula is as follows:

[0021]

[0022] Among them, α 0is the principal stress deflection angle;

[0023] Step 2.3, calculation of deflection inclination angle; specifically: calculating the inclination angle of the upper sliding surface of the shield tunnel after deflection, the calculation formula is as follows:

[0024]

[0025] Among them, θ 1 ,θ 2 are the angles between the slip plane on one side and the slip plane on the other side and the vertical plane, is the internal friction angle of the soil.

[0026] More preferably, step 3 is as follows:

[0027] Step 3.1, calculation of the inclination angle of the slip surface; specifically, calculating the inclination angle of each segment of the broken line slip surface on both sides of the shield tunnel, the specific formula is as follows:

[0028]

[0029] Among them, α 1 , α 2 and α 3 is the inclination angle of each segment of the broken line sliding surface on one side of the shield tunnel, α 1 '、α' 2 and α 3 ' is the inclination angle of each segment of the broken line slip surface on the other side of the tunnel, and is the internal friction angle of each stratum;

[0030] Step 3.2, calculate the position of the sliding surface on one side; specifically, calculate the distance B from the sliding surface on one side of the shield tunnel to the tunnel centerline after extending to the ground surface. tR , the specific formula is as follows:

[0031] B tR =L 0 +L 1 +L 2 +L 3 ;

[0032] in,

[0033]

[0034] Among them, B tR h is the distance from the central axis of the tunnel after the sliding surface on one side of the shield tunnel extends to the ground surface, 1 、h 2 and h 3 is the thickness of each layer at the tunnel centerline, H 0 , L 0 , L1 , L 2 , L 3 They are all geometric quantities in the calculation process, R is the outer radius of the lining;

[0035] Step 3.3, calculate the position of the other side slip surface; specifically: calculate the distance B from the other side slip surface of the shield tunnel to the tunnel centerline after extending to the ground surface tL ;

[0036] Step 3.4, calculation of the shield tunnel excavation influence width; specifically, calculation of the shield tunnel excavation influence width when the shield tunnel passes through the inclined composite stratum, the specific formula is as follows:

[0037] 2B t =B tL +B tR

[0038] Among them, B t It is half of the width affected by the tunnel excavation.

[0039] More preferably, in step 4, during the initialization process by the model initialization module, the following initial boundary conditions are set: the shield tunnel is a shallow buried tunnel, the soil sliding surface is an inclined plane and extends to the ground surface, the sliding body is a rigid body and moves as a whole, and only moves within the plane; the ground surface is an inclined plane; there is no horizontal shear stress on the section parallel to the ground surface.

[0040] More preferably, step 5 is as follows:

[0041] Step 5.1, equation establishment; specifically: taking a differential thin layer in the upper half of the calculation model to establish a balance equation;

[0042] Step 5.2, solving the equation; specifically, simplifying the equilibrium equations to obtain a differential equation, substituting the boundary conditions into the equations, and solving the vertical stress;

[0043] Step 5.3, vertical load calculation: specifically: according to the vertical balance of the lower half of the calculation model, solve the vertical load of the vault of the inclined homogeneous stratum tunnel.

[0044] More preferably, the calculation method of the vertical load of the tunnel vault in the inclined homogeneous stratum in step 5.3 is as follows:

[0045]

[0046] Among them, q y is the vertical load on the tunnel crown, σ yGI is the vertical stress on the GI surface, w is the gravity of the lower half of the calculation model, σ bIJ and τ bIJare the normal stress and shear stress on the IJ surface of the lower half of the calculation model, and c is the cohesion of the soil.

[0047] More preferably, if the vertical load on the top of the shield tunnel is linearly distributed in the horizontal direction and the distribution slope is the same as the surface slope, the vertical loads of the intermediate points are calculated by interpolation in step 5.3.

[0048] More preferably, the formula for calculating the vertical load at each intermediate point by interpolation is as follows:

[0049]

[0050] Among them, q 1 ,q 2 They are the vertical loads on the left and right sides of the shield tunnel vault respectively.

[0051] Beneficial effects of the present invention:

[0052] The invention incorporates the property of the principal stress deflection of the inclined strata and the difference in the slip surface morphology in the composite strata into the vertical load estimation when the shield tunnel passes through the inclined composite strata, so as to provide a reference for the design and construction of the ultra-large diameter shield tunnel passing through the upper soft and lower hard composite strata.

[0053] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A schematic diagram showing calculation of tunnel excavation impact width in one embodiment of the present invention is shown.

[0055] Figure 2 A tunnel load calculation model in one embodiment of the present invention is shown.

[0056] Figure 3 A schematic diagram of force analysis of the upper half of the model in one embodiment of the present invention is shown.

[0057] Figure 4 A schematic diagram of force analysis of the lower half of the model in one embodiment of the present invention is shown.

[0058] Figure 5 A schematic diagram of horizontal distribution of vertical load on the top of a tunnel in one embodiment of the present invention is shown.

[0059] Figure 6 A schematic cross-sectional view of a tunnel passing through an inclined composite stratum in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0060] Example

[0061] like Figures 1 to 6 As shown, a method for estimating vertical load when a shield tunnel passes through an inclined composite stratum is characterized by comprising the following steps:

[0062] Step 1: Based on the survey data of the shield tunnel passing through the inclined composite stratum, the basic parameters of the shield tunnel and the geometric parameters and physical and mechanical property parameters of the inclined composite stratum are extracted, and after data standardization, a database is constructed in the shield machine PLC system;

[0063] Step 2, calculating the initial stress and the principal stress deflection angle of the stratum under the inclined surface when it is only subjected to gravity through the deflection angle calculation module, and calculating the inclination angle of the slip surface above the tunnel after deflection;

[0064] Step 3: After establishing a geometric model of a shield tunnel passing through an inclined composite stratum in the shield machine PLC system, the geometric model is imported into the excavation influence width of the shield tunnel, and then the excavation influence width of the shield tunnel is calculated based on the broken line sliding surface method;

[0065] Step 4: Import the standard data and geometric model in the database into the model initialization module in the shield machine PLC system to initialize and form a calculation model;

[0066] Step 5: For the upper part of the calculation model, the differential equation for vertical stress is established using equilibrium conditions, and the boundary conditions are substituted to solve the vertical stress; for the lower part of the calculation model, the vertical load on the vault of the tunnel in inclined homogeneous strata is solved according to the vertical force balance.

[0067] The invention takes into account the properties of the principal stress deflection of the inclined strata and the differences in the morphology of the slip surface in the composite strata, and provides a reference for the design and construction of an ultra-large diameter shield tunnel passing through a composite stratum with soft upper and hard lower layers.

[0068] In certain embodiments, in step 1, the basic parameters of the shield tunnel in the database include the outer diameter of the lining, the buried depth of the vault and the ground overload, the geometric parameters of the inclined composite strata include the inclination angle of the strata and the thickness of each stratum, and the physical and mechanical property parameters of the inclined composite strata include the density, internal friction angle, cohesion and Poisson's ratio of each stratum.

[0069] In some embodiments, in step 2, the deflection angle calculation module operates as follows:

[0070] Step 2.1, initial stress calculation: specifically, calculate the initial stress of the inclined subsurface stratum of the inclined composite stratum when it is subjected only to gravity, and the calculation formula is as follows:

[0071]

[0072] Among them, σ x , σ y and τ xyare the horizontal stress, vertical stress and shear stress of the point in the soil where the initial stress needs to be calculated, γ is the soil weight, β is the stratum inclination, μ is the Poisson's ratio of the soil, and y is the vertical distance from the point in the soil where the initial stress needs to be calculated to the inclined surface;

[0073] Step 2.2, calculation of principal stress deflection angle; specifically: calculate the principal stress deflection angle of the inclined composite stratum, the calculation formula is as follows:

[0074]

[0075] Among them, α 0 is the principal stress deflection angle;

[0076] Step 2.3, calculation of deflection inclination angle; specifically: calculate the inclination angle of the upper sliding surface of the shield tunnel after deflection, the calculation formula is as follows:

[0077]

[0078] Among them, θ 1 ,θ 2 are the angles between the slip plane on one side and the slip plane on the other side and the vertical plane, is the internal friction angle of the soil.

[0079] In some embodiments, step 3 is as follows:

[0080] Step 3.1, calculation of the inclination angle of the slip surface; specifically: calculate the inclination angle of each segment of the broken line slip surface on both sides of the shield tunnel. The specific formula is as follows:

[0081]

[0082] Among them, α 1 , α 2 and α 3 is the inclination angle of each segment of the broken line sliding surface on one side of the shield tunnel (the right or left side in the figure), α 1 '、α' 2 and α 3 ' is the inclination angle of each segment of the broken line slip surface on one side of the tunnel (right or left side in the figure), and is the internal friction angle of each stratum;

[0083] Step 3.2: Calculate the position of the slip surface on one side; specifically: calculate the distance B from the centerline of the tunnel after the slip surface on one side of the shield tunnel (the right or left side in the figure) extends to the ground surface. tR , the specific formula is as follows:

[0084] B tR =L 0 +L 1 +L2 +L 3 ;

[0085] in,

[0086]

[0087] Among them, B tR h is the distance from the tunnel centerline after the sliding surface on one side of the shield tunnel (the right or left side in the figure) extends to the ground surface, 1 、h 2 and h 3 is the thickness of each layer at the tunnel centerline, H 0 , L 0 , L 1 , L 2 , L 3 They are all geometric quantities in the calculation process, R is the outer radius of the lining;

[0088] Step 3.3, calculate the position of the slip surface on the other side; specifically: calculate the distance B from the centerline of the tunnel after the slip surface on the other side of the shield tunnel (the left or right side in the figure) extends to the ground surface tL ;

[0089] Step 3.4: Calculate the affected width of shield tunnel excavation; specifically, calculate the affected width of shield tunnel excavation when it passes through inclined composite strata. The specific formula is as follows:

[0090] 2B t =B tL +B tR

[0091] Among them, B t It is half of the width affected by the tunnel excavation.

[0092] In some embodiments, in step 4, during the initialization process through the model initialization module, the following initial boundary conditions are set: the shield tunnel is a shallow buried tunnel, the soil sliding surface is an inclined plane and extends to the ground surface, the sliding body is a rigid body and moves as a whole, and only moves within the plane; the ground surface is an inclined plane; there is no horizontal shear stress on the section parallel to the ground surface.

[0093] In some embodiments, step 5 is as follows:

[0094] Step 5.1, equation establishment; specifically: take a differential thin layer in the upper half of the calculation model and establish the equilibrium equation;

[0095] Step 5.2, solve the equation; specifically, simplify the equilibrium equations to obtain differential equations, substitute the boundary conditions, and solve the vertical stress;

[0096] Step 5.3: Calculate the vertical load. Specifically, calculate the vertical load on the vault of the tunnel in the inclined homogeneous stratum based on the vertical equilibrium of the lower part of the calculation model.

[0097] In some embodiments, the vertical load of the tunnel crown in inclined homogeneous strata in step 5.3 is calculated as follows:

[0098]

[0099] Among them, q y is the vertical load on the tunnel crown, σ yGI is the vertical stress on the GI surface, w is the gravity of the lower part of the calculation model, σ bIJ and τ bIJ is the normal stress and shear stress on the IJ surface of the lower part of the calculation model, and c is the cohesion of the soil.

[0100] In some embodiments, if the vertical load on the top of the shield tunnel is linearly distributed in the horizontal direction and the distribution slope is the same as the surface slope, the vertical loads of the intermediate points are calculated by interpolation in step 5.3.

[0101] In some embodiments, the formula for calculating the vertical load of each intermediate point by interpolation is as follows:

[0102]

[0103] Among them, q 1 ,q 2 They are the vertical loads on the left and right sides of the shield tunnel vault, respectively.

[0104] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for estimating vertical load when a shield tunnel passes through an inclined composite stratum; characterized in that: The steps include: Step 1: extract basic parameters of the shield tunnel and geometric parameters and physical and mechanical property parameters of the inclined composite stratum based on the survey data of the shield tunnel passing through the inclined composite stratum, and after data standardization, build a database in the shield machine PLC system; Step 2, calculating the initial stress and the principal stress deflection angle of the stratum under the inclined surface when it is only subjected to gravity through the deflection angle calculation module, and calculating the inclination angle of the slip surface above the tunnel after deflection; Step 3: after establishing a geometric model of the shield tunnel passing through the inclined composite stratum in the shield machine PLC system, the geometric model is imported into the excavation influence width of the shield tunnel, and then the excavation influence width of the shield tunnel is calculated based on the broken line sliding surface method; Step 4: Import the standard data in the database and the geometric model into the model initialization module in the PLC system of the shield machine to initialize and form a calculation model; Step 5: For the upper part of the calculation model, a differential equation for vertical stress is established using equilibrium conditions, and the boundary conditions are substituted to solve the vertical stress; For the lower part of the calculation model, the vertical load on the vault of the tunnel in inclined homogeneous strata is solved according to the vertical force balance.

2. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 1 is characterized in that: In step 1, the basic parameters of the shield tunnel in the database include the outer diameter of the lining, the buried depth of the vault and the ground overload, the geometric parameters of the inclined composite stratum include the stratum inclination angle and the thickness of each stratum, and the physical and mechanical property parameters of the inclined composite stratum include the density, internal friction angle, cohesion and Poisson's ratio of each stratum.

3. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 1, characterized in that: In step 2, the working steps of the deflection angle calculation module are as follows: Step 2.1, initial stress calculation; specifically: calculate the initial stress of the inclined subsurface stratum of the inclined composite stratum when it is subjected only to gravity, and the calculation formula is as follows: Among them, σ x , σ y and τ xy are the horizontal stress, vertical stress and shear stress of the point in the soil where the initial stress needs to be calculated, γ is the soil weight, β is the stratum inclination, μ is the Poisson's ratio of the soil, and y is the vertical distance from the point in the soil where the initial stress needs to be calculated to the inclined surface; Step 2.2, principal stress deflection angle calculation: specifically, calculating the principal stress deflection angle of the inclined composite formation, the calculation formula is as follows: Among them, α0 is the principal stress deflection angle; Step 2.3, calculation of deflection inclination angle; specifically: calculating the inclination angle of the upper sliding surface of the shield tunnel after deflection, the calculation formula is as follows: Among them, θ1 and θ2 are the angles between the slip plane on one side and the slip plane on the other side and the vertical plane, is the internal friction angle of the soil.

4. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 3 is characterized in that: Step 3 is as follows: Step 3.1, calculation of the inclination angle of the slip surface; specifically, calculating the inclination angle of each segment of the broken line slip surface on both sides of the shield tunnel, the specific formula is as follows: Among them, α1, α2 and α3 are the inclination angles of each segment of the broken line slip surface on one side of the shield tunnel, α1', α'2 and α3' are the inclination angles of each segment of the broken line slip surface on one side of the tunnel, and is the internal friction angle of each stratum; Step 3.2, calculate the position of the sliding surface on one side; specifically, calculate the distance B from the sliding surface on one side of the shield tunnel to the tunnel centerline after extending to the ground surface. tR , the specific formula is as follows: <h2 style=";text-align:left;direction:ltr">B<h2 style=";text-align:left;direction:ltr"> tR <h2 style=";text-align:left;direction:ltr"> (L0+L1+L2+L3) in, Among them, B tR is the distance from the central axis of the tunnel to the ground surface after the sliding surface on one side of the shield tunnel extends, h1, h2 and h3 are the thickness of each layer at the central axis of the tunnel, H0, L0, L1, L2, L3 are all geometric quantities in the calculation process, and R is the outer radius of the lining; Step 3.3, calculate the position of the other side slip surface; specifically: calculate the distance B from the other side slip surface of the shield tunnel to the tunnel centerline after extending to the ground surface tL ; Step 3.4, calculation of the shield tunnel excavation influence width; specifically, calculation of the shield tunnel excavation influence width when the shield tunnel passes through the inclined composite stratum, the specific formula is as follows: 2B t =B tL +B tR Among them, B t It is half of the width affected by the tunnel excavation.

5. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 4 is characterized in that: In step 4, during the initialization process through the model initialization module, the following initial boundary conditions are set: the shield tunnel is a shallow buried tunnel, the soil sliding surface is an inclined plane and extends to the ground surface, the sliding body is a rigid body and moves as a whole, and only moves within the plane; the ground surface is an inclined plane; there is no horizontal shear stress on the section parallel to the ground surface.

6. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 1, characterized in that: Step 5 is as follows: Step 5.1, equation establishment; specifically: taking a differential thin layer in the upper half of the calculation model to establish a balance equation; Step 5.2, solving the equation; specifically, simplifying the equilibrium equations to obtain a differential equation, substituting the boundary conditions into the equations, and solving the vertical stress; Step 5.3, vertical load calculation; specifically: according to the vertical balance of the lower half of the calculation model, solve the vertical load of the tunnel vault in the inclined homogeneous stratum.

7. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 6 is characterized in that: The calculation method of the vertical load on the vault of the tunnel in inclined homogeneous strata in step 5.3 is as follows: Among them, q y is the vertical load on the tunnel crown, σ yGI is the vertical stress on the GI surface, w is the gravity of the lower half of the calculation model, σ bIJ and τ bIJ are the normal stress and shear stress on the IJ surface of the lower half of the calculation model, and c is the cohesion of the soil.

8. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 7, characterized in that: If the vertical load on the top of the shield tunnel is distributed linearly in the horizontal direction and the distribution slope is the same as the surface slope, the vertical loads of the intermediate points are calculated by interpolation in step 5.

3.

9. The method for estimating vertical load when a shield tunnel passes through an inclined composite stratum according to claim 8, characterized in that: The formula for calculating the vertical load at each intermediate point by interpolation is as follows: Among them, q1 and q2 are the vertical loads on the left and right sides of the shield tunnel vault respectively.

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