Stress-deformation analysis method of shallow buried soft and broken surrounding rock tunnel based on superposition effect

Abstract

The present invention relates to a stress deformation analysis method for a shallow buried soft and broken surrounding rock tunnel based on the superposition effect, specifically: according to the geological survey report of the tunnel site area and the tunnel design data, the relevant soil layer parameters and structural parameters in the calculation section are obtained; the three-dimensional model of the tunnel invert soil layer is established by using the stratum structure method; the surrounding rock fracture angle is calculated, and the surrounding rock within the fracture angle range above the tunnel is removed; the surrounding rock pressure and the deadweight of the structure are applied to the arch feet on both sides in the form of uniformly distributed loads, and the settlement deformation of the tunnel arch foot and the internal force and deformation of the invert under the design working condition are obtained; the load structure method is used to establish a three-dimensional model of the initial support structure of the tunnel, and the internal force and deformation of the tunnel structure under the same surrounding rock pressure are obtained; and the settlement deformation of the tunnel vault under the design working condition is obtained by the superposition principle. The present invention effectively solves the problem that it is difficult to simulate the internal bulging of the invert and the sinking of the arch foot in conventional numerical simulation analysis, and provides a numerical analysis method for the deformation analysis of tunnels that cannot form natural arches.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering structure design, and in particular relates to a stress deformation analysis method for a shallow buried soft and broken surrounding rock tunnel based on superposition effect. Background Art

[0002] In tunnel structure design, numerical simulation software is often used to establish a two-dimensional or three-dimensional finite element model to analyze tunnel deformation and internal forces in order to verify the rationality of the design scheme. The conventional finite element method based on the continuum theory can better simulate the deformation coordination characteristics between the surrounding rock and the lining and the crushing failure process of the support structure when analyzing tunnels with relatively large burial depths and good surrounding rock. However, it has obvious limitations for tunnels with weak and broken surrounding rocks at shallow burial depths. When the burial depth is shallow, the top surrounding rock cannot form a natural arch during the excavation process of the tunnel. The surrounding rock pressure calculated by the conventional stratum structure method is too small, and due to the poor self-stabilization ability of the weak and broken surrounding rock, the tunnel structure is prone to sinking of the arch feet on both sides and bulging of the invert. If only the load structure method is used for simulation, it is difficult to consider the elastic-plastic coordinated deformation and load sharing between the surrounding rock and the lining, and it is even more difficult to analyze the control effect of different base treatment measures on tunnel deformation.

[0003] CN 112765864 A discloses a stress-deformation analysis method for simulating the excavation process of a tunnel with weak surrounding rock. The method uses ANSYS software to establish a three-dimensional finite element analysis model, and performs stress-deformation analysis on the excavation process of the tunnel with weak surrounding rock. The excavation method is a three-step excavation method with reserved core soil. The method dynamically monitors the stress-deformation conditions of the monitoring points in each excavation step by simulating each stage of the tunnel excavation process. However, when the method is used to simulate the tunnel excavation process, due to the stress release after the soil is excavated, the bottom and arch foot of the invert arch are both bulged, which is inconsistent with the deformation characteristics of the arch foot sinking on both sides of the actual shallow-buried soft and broken surrounding rock tunnel and the inner bulging of the invert arch, and the calculated arch crown settlement is smaller than the actual value. Therefore, the method is not suitable for the simulation analysis of the excavation process of a shallow-buried soft and broken surrounding rock tunnel. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the existing numerical simulation methods and to provide a design calculation method for shallow buried soft and broken surrounding rock tunnels based on superposition effect.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A stress deformation analysis method for a shallow buried soft and broken surrounding rock tunnel based on superposition effect specifically comprises the following steps:

[0007] S1. Obtain relevant soil layer parameters of the tunnel section to be analyzed based on the geological survey report of the tunnel site;

[0008] S2. Obtain relevant structural parameters of the tunnel section to be analyzed based on tunnel design data;

[0009] S3. Calculate the tunnel surrounding rock fracture angle α, the calculation expression is as follows:

[0010]

[0011] In the formula, is the internal friction angle of the tunnel surrounding rock;

[0012] S4. Using the three-dimensional finite element numerical analysis software and the stratum structure method, a three-dimensional finite element model of the tunnel invert-soil layer is established, the surrounding rock within the rupture angle α above the tunnel is removed, and relevant material parameters are assigned to each component of the model;

[0013] S5. Calculate the vertical soil pressure P at the top of the tunnel. The calculation expression is as follows:

[0014]

[0015] Where i is the soil layer number from top to bottom at the top of the tunnel; n is the number of soil layers at the top of the tunnel; γ i is the soil weight of the i-th layer; h i is the thickness of the i-th soil layer; B is the tunnel span;

[0016] S6. The vertical soil pressure P at the top of the tunnel and the deadweight W of the structure are applied to the arch feet on both sides in the form of uniformly distributed loads. The calculation expression of the uniformly distributed load q is as follows:

[0017]

[0018] Where, l is the width of the arch foot on one side of the tunnel invert structure;

[0019] S7. Apply normal distributed load f on both sides of the fracture surface, and its calculation expression is as follows:

[0020]

[0021] Where, j is the soil layer number where the load calculation point is located; h j0 is the thickness of the soil layer from the calculation point in the j-layer to the top of the j-layer; γ j is the weight of the jth soil layer;

[0022] S8. After setting the interaction between components and model boundary constraints, meshing is performed and the tunnel arch foot settlement deformation y under the design condition is obtained through numerical calculation. j0 and internal forces and deformations in the invert area;

[0023] S9. Using the three-dimensional finite element numerical analysis software, the load structure method is used to establish a three-dimensional finite element model of the initial tunnel support structure. The vertical soil pressure on the top of the tunnel is calculated as a uniformly distributed load q v The uniform load q is applied to the outer surface of the arch of the initial support structure. v The calculation expression is as follows:

[0024]

[0025] Where k is the load sharing ratio of the initial tunnel support structure;

[0026] S10, the lateral earth pressure of the tunnel q h Applied to the outer surface of the primary arch and side wall, the load direction is horizontal to the right on the left side of the tunnel centerline and horizontal to the left on the right side. h The calculation expression is as follows:

[0027]

[0028] In the formula, λ j is the soil lateral pressure coefficient of the jth layer;

[0029] S11. Ground springs are set around the primary support structure of the tunnel. The spring stiffness is determined according to the elastic resistance coefficient of the surrounding rock. The interaction between each component and other boundary constraints are set. The model is meshed and the settlement value y at the same position of the tunnel arch foot under the same design condition is obtained after calculation. j1 At this time, the tunnel lining, steel internal forces and arch settlement value y d1 ;

[0030] S12. Calculate the settlement difference Δy between the tunnel vault and the vault foot. The calculation expression is as follows:

[0031] Δy=y d1 -y j1

[0032] S13. According to the superposition principle, calculate the actual settlement value y of the tunnel vault d0 , the calculation expression is as follows:

[0033] y d0 =y j0 +Δy;

[0034] Furthermore, the relevant soil layer parameters include the bulk density, internal friction angle, cohesion, elastic modulus, Poisson's ratio, lateral pressure coefficient and soil layer thickness in the calculation section of each soil layer.

[0035] Furthermore, the relevant structural parameters of the tunnel section include tunnel structure dimensions, material parameters, tunnel burial depth, steel bars, steel arch frames, locking anchor rods and jet grouting pile parameters and distribution.

[0036] Furthermore, in the three-dimensional finite element model of the tunnel invert-soil layer established by the stratum structure method, the soil adopts the elastic-plastic Mohr-Coulomb constitutive model, the steel bars, locking anchor rods, steel arch frames, and jet-jet piles adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage plastic constitutive model.

[0037] Furthermore, in the three-dimensional finite element model of the initial support structure of the tunnel established by the load-structure method, the steel bars and steel arch frames adopt an elastoplastic constitutive model, and the lining adopts a concrete damage plastic constitutive model. When modeling, the parameters of the steel arch frames can be converted into the concrete of the initial support according to the density and elastic modulus conversion method.

[0038] Beneficial effects of the present invention: Compared with the prior art, the present invention has the following advantages:

[0039] 1. Based on the superposition principle, the present invention adopts an analysis method combining the stratum structure method and the load structure method to analyze the stress deformation of shallow buried soft and broken surrounding rock tunnels, which overcomes the problem that the surrounding rock pressure calculated by the conventional stratum structure method is too small, and solves the problem that the load structure method is difficult to consider the coordinated deformation of the surrounding rock and the lining;

[0040] 2. The calculation results of the present invention are consistent with the phenomenon of sinking of arch feet on both sides and bulging of invert arch in actual shallow-buried soft and broken surrounding rock tunnels, and the arch crown settlement value is closer to the actual value than the calculation results of conventional simulation methods;

[0041] 3. The present invention provides a new and more effective method for analyzing the influence of tunnel base treatment measures on structural stress and deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the process of the present invention.

[0043] Figure 2 This is a 1:100 design drawing of the calculated section tunnel section in the embodiment.

[0044] Figure 3 It is a schematic diagram of the three-dimensional model of the invert-soil layer.

[0045] Figure 4 Schematic diagram of the three-dimensional model of the initial support structure of the tunnel.

[0046] Figure 5 Schematic diagram of surrounding rock pressure of initial tunnel support structure. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0048] A stress-deformation analysis method for shallow buried soft and broken surrounding rock tunnels based on superposition effect. Figure 1 As shown, the specific implementation steps of the measurement method are as follows:

[0049] Step S1: According to the geological survey report of the tunnel site, obtain the relevant soil layer parameters in the calculation section, including the bulk density and internal friction angle of each soil layer. Cohesion, elastic modulus, Poisson's ratio, lateral pressure coefficient and soil thickness in the calculation section;

[0050] Step S2, according to the tunnel design data, obtain relevant structural parameters in the calculation section, including tunnel structure size, material parameters, tunnel burial depth, steel bars, steel arches, locking anchors and jet grouting pile parameters and distribution;

[0051] Step S3, calculating the tunnel surrounding rock fracture angle α, the calculation expression is as follows:

[0052]

[0053] Step S4, using a three-dimensional finite element numerical analysis software and a stratum structure method to establish a three-dimensional finite element model of the tunnel invert-soil layer, removing the surrounding rock within the range of the rupture angle α above the tunnel, and assigning relevant material parameters to each component of the model, wherein the soil adopts an elastic-plastic Mohr Coulomb constitutive model, the steel bars, locking anchors, steel arch frames, and jet-jet piles adopt an elastic-plastic constitutive model, and the lining adopts a concrete damage plastic constitutive model;

[0054] Step S5, calculate the vertical earth pressure P at the top of the tunnel, and its calculation expression is as follows:

[0055]

[0056] Where i is the soil layer number from top to bottom at the top of the tunnel; n is the number of soil layers at the top of the tunnel; γ i is the soil weight of the i-th layer; h i is the thickness of the i-th soil layer; B is the tunnel span;

[0057] Step S6: The vertical soil pressure P at the top of the tunnel and the deadweight W of the structure are applied to the arch feet on both sides in the form of uniformly distributed loads. The calculation expression of the uniformly distributed load q is as follows:

[0058]

[0059] Where, l is the width of the arch foot on one side of the tunnel invert structure;

[0060] Step S7: Apply a normal distributed load f on the fracture surfaces on both sides, and the calculation expression is as follows:

[0061]

[0062] Where, j is the soil layer number where the load calculation point is located; h j0 is the thickness of the soil layer from the calculation point in the j-layer to the top of the j-layer; γ j is the weight of the jth soil layer;

[0063] Step S8: After setting the interaction between components and model boundary constraints, meshing is performed and the tunnel arch foot settlement deformation y under the design condition is obtained through numerical calculation. j0 and internal forces and deformations in the invert area;

[0064] Step S9: Use the load structure method to establish a three-dimensional finite element model of the initial support structure of the tunnel through three-dimensional finite element numerical analysis software, in which the steel bars and steel arch frame adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage plastic constitutive model. The vertical soil pressure on the top of the tunnel is calculated as a uniformly distributed load q downward. v The uniform load q is applied to the outer surface of the arch of the initial support structure. v The calculation expression is as follows:

[0065]

[0066] Where k is the load sharing ratio of the initial tunnel support structure;

[0067] Step S10: The tunnel lateral earth pressure q h Applied to the outer surface of the primary arch and side wall, the load direction is horizontal to the right on the left side of the tunnel centerline and horizontal to the left on the right side. h The calculation expression is as follows:

[0068]

[0069] In the formula, λ j is the soil lateral pressure coefficient of the jth layer;

[0070] Step S11: Ground springs are set around the tunnel primary support structure. The spring stiffness is determined according to the elastic resistance coefficient of the surrounding rock. The interaction between the components and other boundary constraints are set. The model is meshed and the settlement value y at the same position of the tunnel arch foot under the same design condition is calculated. j1 At this time, the tunnel lining, steel internal forces and arch settlement value y d1 ;

[0071] Step S12: Calculate the settlement difference Δy between the tunnel vault and the vault foot. The calculation expression is as follows:

[0072] Δy=y d1 -y j1 ;

[0073] Step S13: Calculate the actual settlement value y of the tunnel vault according to the superposition principle.d0 , the calculation expression is as follows:

[0074] y d0 =y j0 +Δy;

[0075] The following are specific implementation cases:

[0076] 1. According to the geological survey report of the tunnel site, obtain the relevant soil layer parameters in the calculation section, as shown in Table 1:

[0077] Table 1 Soil layer parameters

[0078]

[0079] 2. According to the tunnel design data, obtain the relevant structural parameters in the calculation section: Tunnel structure dimensions are shown in the attached Figure 2 ; The tunnel is buried at a depth of 13.67m; the steel arch frame is made of I22a I-steel with a longitudinal spacing of 60cm; the initial support arch is sprayed with 28cm thick C25 concrete, and the side wall is C30 cast-in-place concrete; the full-section cast-in-place C30 reinforced concrete secondary lining is 50cm thick, and the invert is 78cm thick C30 reinforced concrete; the jet grouting piles are arranged in a plum blossom shape, with the two middle piles being 4m long, 150cm horizontally, and 120cm longitudinally; the piles on both sides are 6m long, with both horizontal and longitudinal spacing of 120cm; three 6m long, Ф89×6mm locking anchors are set at the triangular support positions on both sides of the arch foot. When modeling, the parameters of the steel arch frame can be converted to the initial support concrete according to the density and elastic modulus conversion method. The tunnel support structure parameters are shown in Table 2:

[0080] Table 2 Tunnel support structure parameters

[0081]

[0082]

[0083] 3. The calculated fracture angle α of the tunnel surrounding rock is 56°.

[0084] 4. Using the 3D finite element numerical analysis software, the stratum structure method is used to establish a 3D finite element model of the tunnel invert-soil layer, as shown in the attached figure. Figure 3 The surrounding rock within the rupture angle α above the tunnel is removed, and the relevant material parameters of each component of the model are assigned. The soil adopts the elastic-plastic Mohr-Coulomb constitutive model, the steel bars, locking anchors, and jet-grouting piles adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage plastic constitutive model.

[0085] 5. Calculate the vertical earth pressure at the top of the tunnel

[0086] 6. Calculate the self-weight of the structure W = 440.9 kN / m and the uniformly distributed load q:

[0087]

[0088] Apply a uniformly distributed load q to the arch feet on both sides.

[0089] 7. Calculation of distributed loads And it is applied normally to the fracture surfaces on both sides.

[0090] 8. After setting the interaction between the components and the model boundary constraints, meshing is performed and the tunnel arch foot settlement deformation y under the design condition is obtained through numerical calculation. j0 It is -6.91cm.

[0091] IX. Using the three-dimensional finite element numerical analysis software, the load structure method is used to establish a three-dimensional finite element model of the initial support structure of the tunnel. The steel bars and steel arches use the elastic-plastic constitutive model, and the lining uses the concrete damage plastic constitutive model, as shown in the attached figure. Figure 4 As shown;

[0092] According to the measured contact pressure between the primary support and the secondary lining of the tunnel and the surrounding rock pressure, the load bearing ratio of the primary support is about 51%. Combined with the load bearing ratio of the primary support of the double-lane under the V-level surrounding rock given in the "Highway Tunnel Design Details", which is ≥50%, and the primary support load sharing ratio in the "Highway Tunnel Design Code" (JTG3370.1-2018) is 20% to 40%, the load sharing ratio of the initial support structure is taken as 50% after comprehensive consideration;

[0093] The uniformly distributed load q is calculated v is 107.3 kPa, and q v Applied to the outer surface of the arch of the initial supporting structure.

[0094] 10. Calculation of tunnel lateral earth pressure q h =3572h(Pa) is applied to the outer surface of the primary support arch and the side wall. The load direction is horizontally to the right on the left side of the tunnel centerline and horizontally to the left on the right side. The schematic diagram of the tunnel surrounding rock pressure is shown in the attached figure. Figure 5 .

[0095] 11. Ground springs are set around the primary support structure of the tunnel. The spring stiffness is 70MPa / m. Except for the invert and arch foot, the springs at other positions are set as nonlinear springs that are only compressed but not tensile. At the same time, the interaction between each component and other boundary constraints are set, such as the attached Figure 4 , the model is meshed, and the settlement value y at the same position of the tunnel arch foot under the same design conditions is obtained after calculation j1 is -0.41cm. At this time, the initial support arch settlement value y d1 It is -0.88cm.

[0096] 12. Calculate the settlement difference between the tunnel vault and the arch foot Δy = yd1 -y j1 =-0.47cm.

[0097] 13. Calculate the actual settlement value y of the tunnel vault according to the superposition principle d0 =y j0 +Δy=-7.38cm. The measured initial arch settlement of the tunnel in this section is 6-17cm. The calculation result of the method of the present invention is within this range.

[0098] The above describes in detail the preferred specific embodiments of the present invention. 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 required by the claims of the present invention.

Claims

1. A stress-deformation analysis method for shallow buried soft and broken surrounding rock tunnels based on superposition effect, characterized in that: The steps include: S1. Obtain relevant soil layer parameters of the tunnel section to be analyzed based on the geological survey report of the tunnel site; S2. Obtain relevant structural parameters of the tunnel section to be analyzed based on tunnel design data; S3. Calculate the tunnel surrounding rock fracture angle α, the calculation expression is as follows: In the formula, is the internal friction angle of the tunnel surrounding rock; S4. Using the three-dimensional finite element numerical analysis software and the stratum structure method, a three-dimensional finite element model of the tunnel invert-soil layer is established, the surrounding rock within the rupture angle α above the tunnel is removed, and relevant material parameters are assigned to each component of the model; S5. Calculate the vertical soil pressure P at the top of the tunnel. The calculation expression is as follows: Where i is the soil layer number from top to bottom at the top of the tunnel; n is the number of soil layers at the top of the tunnel; γ i is the soil weight of the i-th layer; h i is the thickness of the i-th soil layer; B is the tunnel span; S6. The vertical soil pressure P at the top of the tunnel and the deadweight W of the structure are applied to the arch feet on both sides in the form of uniformly distributed loads. The calculation expression of the uniformly distributed load q is as follows: Where, l is the width of the arch foot on one side of the tunnel invert structure; S7. Apply normal distributed load f on both sides of the fracture surface, and its calculation expression is as follows: Where, j is the soil layer number where the load calculation point is located; h j0 is the thickness of the soil layer from the calculation point in the j-layer to the top of the j-layer; γ j is the weight of the jth soil layer; S8. After setting the interaction between components and model boundary constraints, meshing is performed and the tunnel arch foot settlement deformation y under the design condition is obtained through numerical calculation. j0 and internal forces and deformations in the invert area; S9. Using the three-dimensional finite element numerical analysis software, the load structure method is used to establish a three-dimensional finite element model of the initial tunnel support structure. The vertical soil pressure on the top of the tunnel is calculated as a uniformly distributed load q v The uniform load q is applied to the outer surface of the arch of the initial support structure. v The calculation expression is as follows: Where k is the load sharing ratio of the initial tunnel support structure; S10, the lateral earth pressure of the tunnel q h Applied to the outer surface of the primary support arch and the side wall, the load direction is horizontal to the right on the left side of the tunnel centerline and horizontal to the left on the right side. h The calculation expression is as follows: In the formula, λ j is the soil lateral pressure coefficient of the jth layer; S11. Ground springs are set around the primary support structure of the tunnel. The spring stiffness is determined according to the elastic resistance coefficient of the surrounding rock. The interaction between each component and other boundary constraints are set. The model is meshed and the settlement value y at the same position of the tunnel arch foot under the same design condition is obtained after calculation. j1 At this time, the tunnel lining, steel bar internal force and arch settlement value y d1 ; S12. Calculate the settlement difference Δy between the tunnel vault and the vault foot. The calculation expression is as follows: Δy=y d1 -y j1 ; S13. According to the superposition principle, calculate the actual settlement value y of the tunnel vault d0 , the calculation expression is as follows: y d0 =y j0 +Δy。 2. The stress and deformation analysis method for shallow buried soft and broken surrounding rock tunnels based on superposition effect according to claim 1 is characterized in that: The relevant soil layer parameters include the bulk density, internal friction angle, cohesion, elastic modulus, Poisson's ratio, lateral pressure coefficient and soil layer thickness in the calculation section of each soil layer.

3. The stress deformation analysis method for shallow buried soft and broken surrounding rock tunnel based on superposition effect according to claim 1 is characterized in that: The relevant structural parameters of the tunnel section include tunnel structure size, material parameters, tunnel burial depth, steel bars, steel arch frames, locking anchor rods and jet grouting pile parameters and distribution.

4. The stress and deformation analysis method for shallow buried soft and broken surrounding rock tunnel based on superposition effect according to claim 1 is characterized in that: In the three-dimensional finite element model of the tunnel invert-soil layer established by the stratum structure method, the soil adopts the elastic-plastic Mohr-Coulomb constitutive model, the steel bars, locking anchor rods and jet-jet piles adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage plastic constitutive model.

5. The stress and deformation analysis method for shallow buried soft and broken surrounding rock tunnel based on superposition effect according to claim 1 is characterized in that: In the three-dimensional finite element model of the initial support structure of the tunnel established by the load structure method, the steel bar adopts an elastic-plastic constitutive model and the lining adopts a concrete damage plastic constitutive model. When modeling, the parameters of the steel arch frame can be converted into the concrete of the initial support according to the density and elastic modulus conversion method.

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