CN115017587A - Superimposed effect-based stress deformation analysis method for shallow-buried weak broken surrounding rock tunnel - Google Patents

Abstract

The invention relates to a method for analyzing the stress and deformation of a shallow-buried weak and broken surrounding rock tunnel based on superposition effect, which specifically includes: obtaining relevant soil layer parameters and structural parameters in a calculation section according to a tunnel site area geological survey report and tunnel design data ; Establish a three-dimensional model of the tunnel invert-soil layer by using the stratum structure method; calculate the rupture angle of the surrounding rock, and remove the surrounding rock within the range of the rupture angle above the tunnel; apply the surrounding rock pressure and structural self-weight to both sides in the form of uniform loads The arch foot is used to obtain the settlement deformation of the tunnel arch foot and the internal force and deformation of the inverted arch under the design conditions; 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; According to the principle, the settlement deformation of the tunnel vault under the design condition is obtained. The invention effectively solves the problem that it is difficult to simulate the inner drum of the inverted arch and the subsidence of the arch foot in the conventional numerical simulation analysis, and provides a numerical analysis method for the deformation analysis of the tunnel which cannot form a natural arch.

Description

Analysis method of force and deformation of shallow tunnel with weak and broken surrounding rock based on superposition effect

technical field

The invention belongs to the technical field of tunnel engineering structure design, in particular to a method for analyzing the stress and deformation of a shallow-buried weak and broken surrounding rock tunnel based on a superposition effect.

Background technique

In the design of tunnel structure, numerical simulation software is often used to establish a two-dimensional or three-dimensional finite element model for tunnel deformation and internal force analysis to verify the rationality of the design scheme. However, 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 of the supporting structure when analyzing the tunnel with relatively large buried depth and good surrounding rock. However, it has obvious limitations for weak and broken surrounding rock tunnels with shallow burial depth. When the burial depth is shallow, the surrounding rock at the top of the tunnel cannot form a natural arch during the excavation process. The surrounding rock pressure calculated by the conventional stratigraphic method is too small, and the tunnel structure is prone to appear due to the poor self-stabilizing ability of the weak and broken surrounding rock. The phenomenon that the arches on both sides sink and the inverted arch is bulging. 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 the tunnel deformation.

CN 112765864 A discloses a method for simulating stress and deformation in the excavation process of weak surrounding rock of a tunnel. This method uses ANSYS software to establish a three-dimensional finite element analysis model, and analyzes the force and deformation of the excavation process of the weak surrounding rock of the tunnel. The excavation method is the three-step excavation method with reserved core soil. The method dynamically monitors the stress and deformation of the monitoring points in each excavation step by simulating each stage of the tunnel excavation process. However, when this method is used to simulate the tunnel excavation process, due to the release of stress after soil excavation, the bottom of the inverted arch and the arch foot are uplifted, which is different from the subsidence of the arch foot on both sides of the actual shallow-buried weak and broken surrounding rock tunnel, and the inner bulge of the inverted arch. Compared with the actual value, this method is not suitable for the simulation analysis of the excavation process of the shallow tunnel with weak and broken surrounding rock.

SUMMARY OF THE INVENTION

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

The object of the present invention can be realized through the following technical solutions:

A method for analyzing the force and deformation of a shallow-buried weak and broken surrounding rock tunnel based on the superposition effect, specifically comprising the following steps:

S1. According to the geological survey report of the tunnel site area, obtain the relevant soil layer parameters of the tunnel section to be analyzed;

S2. Obtain relevant structural parameters of the tunnel section to be analyzed according to the tunnel design data;

S3. Calculate the fracture angle α of the surrounding rock of the tunnel, and its calculation expression is as follows:

为隧道围岩内摩擦角；In the formula,

is the internal friction angle of the tunnel surrounding rock;

S4. Through the three-dimensional finite element numerical analysis software, the stratum structure method is used to establish a three-dimensional finite element model of the tunnel invert-soil layer, the surrounding rock within the range of the rupture angle α above the tunnel is removed, and the relevant material parameters of each part of the model are given;

S5. Calculate the vertical earth pressure P at the top of the tunnel, and its calculation expression is as follows:

where i is the number of soil layers at the top of the tunnel from top to bottom; n is the number of soil layers at the top of the tunnel; γ _i is the weight of the _i -th layer of soil; hi is the thickness of the i-th layer of soil; B is the tunnel span;

S6. The vertical earth pressure P at the top of the tunnel and the self-weight W of the structure are applied to the arches on both sides in the form of uniform load. The calculation expression of the uniform load q is as follows:

In the formula, l is the width of the unilateral arch foot of the tunnel inverted arch structure;

S7. Apply a normal distributed load f on the rupture surfaces on both sides, and its calculation expression is as follows:

In the formula, j is the number of the soil layer where the load calculation point is located; h _j0 is the thickness of the soil layer between the calculation point in the j layer of soil and the top of the j layer; γ _j is the soil layer weight of the jth layer;

S8. After setting the interaction between the components and the boundary constraints of the model, perform mesh division, and obtain the settlement deformation y _j0 of the tunnel arch foot and the force and deformation in the inverted arch area through numerical calculation;

S9. Through 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, and the vertical earth pressure at the top of the tunnel is applied to the arch of the initial support structure in the form of a vertically downward uniform load q _v External surface, the uniform load q _v is calculated as follows:

where k is the load sharing ratio of the initial support structure of the tunnel;

S10. Apply the lateral earth pressure q _h of the tunnel to the outer surface of the primary arch and the side wall. The load direction is the left side of the tunnel centerline horizontally to the right and the right side horizontally to the left. The calculation expression of q _h is as follows:

where λ _j is the soil side pressure coefficient of the jth layer;

S11. The grounding spring is set around the initial support structure of the tunnel. The spring stiffness is determined according to the elastic resistance coefficient of the surrounding rock. The interaction of each component and other boundary constraints are set, and the model is meshed. After calculation, the tunnel under the same design conditions is obtained. The settlement value y _j1 at the same position of the arch foot, and the settlement value y _d1 of the tunnel lining, the internal force of the steel bar and the vault at this time;

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

Δy=y _d1 -y _j1

S13. According to the superposition principle, calculate the actual settlement value y _d0 of the tunnel vault, and the calculation expression is as follows:

y _d0 =y _j0 +Δy;

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

Further, the relevant structural parameters of the tunnel section include tunnel structural dimensions, material parameters, tunnel burial depth, steel bars, steel arches, foot-locking anchors and jetted pile parameters and distribution.

Further, in the tunnel inverted arch-soil three-dimensional finite element model established by the stratum structure method, the soil adopts the elastic-plastic Mohr Coulomb constitutive model, and the steel bars, the locking anchors, the steel arches, and the rotary jet piles adopt elastic Plastic constitutive model, lining adopts concrete damage plastic constitutive model.

Further, in the three-dimensional finite element model of the initial support structure of the tunnel established by the load structure method, the steel bar and the steel arch adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage-plastic constitutive model. The elastic modulus conversion algorithm converts the parameters of the steel arch into the concrete of the initial support.

Beneficial effects of the present invention: compared with the prior art, the present invention has the following advantages:

1. Based on the superposition principle, the present invention adopts the analysis method combining the stratum structure method and the load structure method to analyze the force and deformation of the shallowly buried soft and broken surrounding rock tunnel, which overcomes the small surrounding rock pressure calculated by the conventional stratum structure method. It also solves the problem that the load structure method is difficult to consider the coordinated deformation of the surrounding rock and the lining;

2, the calculation result of the present invention is consistent with the phenomenon of the subsidence of the arch foot on both sides of the actual shallow-buried weak broken surrounding rock tunnel, the inner bulge of the inverted arch, and the vault settlement value is closer to the actual value than the calculation result of the conventional simulation method;

3. The present invention provides a new and more effective method for the analysis of the influence of the tunnel base treatment measures on the stress and deformation of the structure.

Description of drawings

FIG. 1 is a schematic flow chart of the present invention.

FIG. 2 is a 1:100 design drawing of the tunnel section in the calculation section in the embodiment.

Figure 3 is a schematic diagram of the inverted arch-soil three-dimensional model.

Figure 4 is a schematic diagram of the three-dimensional model of the initial support structure of the tunnel.

Figure 5 is a schematic diagram of the surrounding rock pressure of the initial support structure of the tunnel.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

A method for analyzing the force and deformation of a shallow-buried weak and broken surrounding rock tunnel based on the superposition effect is shown in Figure 1. The specific implementation steps of the measurement method are as follows:

粘聚力、弹性模量、泊松比、侧压力系数和计算区段内土层厚度；Step S1, according to the geological survey report of the tunnel site area, 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 layer thickness within the calculation section;

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

Step S3, calculate the rupture angle α of the surrounding rock of the tunnel, and its calculation expression is as follows:

Step S4, through the three-dimensional finite element numerical analysis software, the stratum structure method is used to establish a three-dimensional finite element model of the tunnel invert-soil layer, the surrounding rock within the range of the rupture angle α above the tunnel is removed, and the relevant material parameters of each part of the model are given, wherein The soil adopts the elastic-plastic Mohr-Coulomb constitutive model, the steel bar, the anchor bolt, the steel arch and the jetted pile adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage-plastic constitutive model;

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

where i is the number of soil layers at the top of the tunnel from top to bottom; n is the number of soil layers at the top of the tunnel; γ _i is the weight of the _i -th layer of soil; hi is the thickness of the i-th layer of soil; B is the tunnel span;

In step S6, the vertical earth pressure P at the top of the tunnel and the self-weight W of the structure are applied to the arches on both sides in the form of uniform load. The calculation expression of the uniform load q is as follows:

In the formula, l is the width of the unilateral arch foot of the tunnel inverted arch structure;

In step S7, the normal distributed load f is applied to the rupture surfaces on both sides, and the calculation expression is as follows:

In the formula, j is the number of the soil layer where the load calculation point is located; h _j0 is the thickness of the soil layer between the calculation point in the j layer of soil and the top of the j layer; γ _j is the soil layer weight of the jth layer;

Step S8, after setting the interaction between the components and the boundary constraints of the model, perform grid division, and obtain the settlement deformation y _j0 of the tunnel arch foot and the force and deformation in the inverted arch area through numerical calculation;

Step S9, through 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, in which the steel bars and steel arches adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage-plastic constitutive model. The top vertical earth pressure is applied to the outer surface of the arch of the initial support structure in the form of a vertically downward uniform load q _v . The calculation expression of the uniform load q _v is as follows:

where k is the load sharing ratio of the initial support structure of the tunnel;

In step S10, the lateral earth pressure q _h of the tunnel is applied to the outer surface of the primary arch and the side wall, and the load direction is the left side of the tunnel centerline horizontally to the right and the right side horizontally to the left, and the calculation expression of q _h is as follows:

where λ _j is the soil side pressure coefficient of the jth layer;

Step S11, set grounding springs around the initial support structure of the tunnel, the spring stiffness is determined according to the elastic resistance coefficient of the surrounding rock, set the interaction of each component and other boundary constraints, mesh the model, and obtain the same design conditions after calculation. The settlement value y _j1 at the same position of the tunnel arch foot, and the settlement value y _d1 of the tunnel lining, steel internal force and the vault at this time;

Step S12, calculate the settlement difference Δy between the tunnel vault and the arch foot position, and the calculation expression is as follows:

Δy=y _d1 -y _j1 ;

Step S13, according to the superposition principle, calculate the actual settlement value y _d0 of the tunnel vault, and the calculation expression is as follows:

y _d0 =y _j0 +Δy;

The following are specific implementation cases:

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

Table 1 Soil layer parameters

2. According to the tunnel design data, obtain the relevant structural parameters in the calculation section: the structure size of the tunnel is shown in Figure 2; the tunnel burial depth is 13.67m; the steel arch adopts I22a I-beam, and the longitudinal spacing is 60cm; the initial support arch is sprayed 28cm thick C25 concrete, side walls are C30 cast concrete; full-section moulded C30 reinforced concrete secondary lining with a thickness of 50cm, inverted arch is 78cm thick C30 reinforced concrete; the jetted piles are arranged in plum blossom, with two piles in the middle The length is 4m, the horizontal spacing is 150cm, the vertical row spacing is 120cm, the piles on both sides are 6m long, and the horizontal spacing and vertical row spacing are both 120cm; three 6m long, Ф89×6mm locking foot anchors are set on both sides of the arch foot. The parameters of the steel arch can be converted into the concrete of the initial support according to the density and elastic modulus conversion algorithm. The parameters of the tunnel support structure are shown in Table 2:

Table 2 Tunnel support structure parameters

3. Calculate the fracture angle α of the surrounding rock of the tunnel to be 56°.

4. Through the three-dimensional finite element numerical analysis software, the stratum structure method is used to establish a three-dimensional finite element model of the tunnel invert-soil layer. As shown in Figure 3, the surrounding rock within the range of the rupture angle α above the tunnel is removed, and the relevant components of the model are assigned. Material parameters, the soil adopts the elastic-plastic Mohr-Coulomb constitutive model, the steel bar, the anchor bolt and the jetted pile adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage-plastic constitutive model.

5. Calculate the vertical earth pressure at the top of the tunnel

6. Calculate the weight of the structure W=440.9kN/m, and calculate the uniform load q:

A uniform load q is applied to the arches on both sides.

并法向施加于两侧破裂面上。7. Calculate the distributed load

And the normal direction is applied to the rupture surfaces on both sides.

8. After setting the interaction between the components and the boundary constraints of the model, perform mesh division, and obtain the settlement deformation y _j0 of the tunnel arch under the design condition through numerical calculation to be -6.91cm.

9. Through the three-dimensional finite element numerical analysis software, the load structure method is used to establish the three-dimensional finite element model of the initial support structure of the tunnel, in which the reinforcement and steel arches adopt the elastic-plastic constitutive model, and the lining adopts the concrete damage-plastic constitutive model, as shown in the attached drawings. 4 shown;

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%. The load bearing ratio is ≥50%, and the load sharing ratio of the initial support in the "Code for Design of Highway Tunnels" (JTG3370.1-2018) is 20% to 40%. Considering comprehensively, the load sharing ratio of the initial support structure is 50%;

The uniform load q _v is calculated to be 107.3kPa, and q _v is applied to the outer surface of the arch of the initial support structure.

10. Calculate the lateral earth pressure of the tunnel q _h = 3572h (Pa) and apply it to the primary arch and the outer surface of the side wall. The load direction is the left side of the tunnel centerline horizontally to the right and the right side horizontally to the left. The schematic diagram of the surrounding rock pressure of the tunnel is as follows Figure 5.

11. Grounding springs are installed all around the primary support structure of the tunnel, and the spring stiffness is 70MPa/m. Except for the inverted arch and the arch foot, the springs at other positions are set as nonlinear springs that are only compressed and not tensioned. At the same time, the interaction and For other boundary constraints, as shown in Figure 4, the model is divided into meshes. After calculation, the settlement value y _j1 at the same position of the tunnel arch foot under the same design conditions is -0.41cm, and the settlement value y _d1 of the initial support vault at this time is is -0.88cm.

12. Calculate the settlement difference Δy=y _d1 -y _j1 =-0.47cm between the tunnel vault and the arch foot position.

13. According to the superposition principle, calculate the actual settlement value of the tunnel vault y _d0 = y _j0 +Δy = -7.38cm, and the measured settlement value of the primary vault of the tunnel in this section is 6-17cm. The calculation result of the method of the present invention is as follows: within this range.

The preferred embodiments of the present invention have been described above in detail. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, any technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the prior art according to the concept of the present invention shall fall within the protection scope required by the claims of the present invention. Inside.

Claims (5)

1. A shallow-buried weak broken surrounding rock tunnel stress deformation analysis method based on superposition effect is characterized by comprising the following steps:

s1, acquiring relevant soil layer parameters of the tunnel section to be analyzed according to the geological survey report of the tunnel site area;

s2, acquiring relevant structural parameters of the tunnel section to be analyzed according to the tunnel design data;

s3, calculating the fracture angle alpha of the tunnel surrounding rock, wherein the calculation expression is as follows:

in the formula (I), the compound is shown in the specification,

the angle is the internal friction angle of the tunnel surrounding rock;

s4, establishing a tunnel inverted arch-soil layer three-dimensional finite element model by adopting a stratum structure method through three-dimensional finite element numerical analysis software, removing surrounding rocks within a cracking angle alpha range above the tunnel, and giving relevant material parameters to each component of the model;

s5, calculating the vertical soil pressure P at the top of the tunnel, wherein the calculation expression is as follows:

in the formula, i is the serial number of the soil layer at the top of the tunnel from top to bottom; n is the number of soil layers at the top of the tunnel; gamma ray _i The soil layer weight of the ith layer; h is _i The thickness of the ith soil layer; b is a tunnel span;

s6, applying vertical soil pressure P and structure dead weight W at the top of the tunnel to arch springing at two sides in a uniformly distributed load mode, wherein the uniformly distributed load q is calculated by the following expression:

in the formula, l is the width of a single-side arch springing of the tunnel inverted arch structure;

s7, applying normal distribution load f on the fracture surfaces on the two sides, wherein the calculation expression is as follows:

in the formula, j is the serial number of the soil layer where the load calculation point is located; h is _j0 Calculating the thickness of the soil layer from the top of the j layer to the point where the j layer soil is located; gamma ray _j The soil layer weight of the j layer;

s8, after interaction among all parts and constraint of model boundary are set, grid division is carried out, and settlement deformation y of tunnel arch springing under design working condition is obtained through numerical calculation _j0 And force and deformation in the inverted arch area;

s9, establishing a three-dimensional finite element model of a tunnel primary support structure by a load structure method through three-dimensional finite element numerical analysis software, and uniformly distributing a load q vertically downward to the top of the tunnel under the action of vertical soil pressure _v Applying the form to the outer surface of the arch part of the primary supporting structure and uniformly distributing the load q _v The calculation expression is as follows:

in the formula, k is the load sharing ratio of the primary tunnel supporting structure;

s10, subjecting the lateral soil pressure q of the tunnel to _h Applied to the outer surfaces of the primary arch part and the side wall, and the load directions are that the left side of the center line of the tunnel is horizontally rightward, the right side of the center line of the tunnel is horizontally leftward, and q is _h The calculation expression of (c) is as follows:

in the formula of lambda _j The pressure coefficient of the soil side of the jth layer is taken as the pressure coefficient of the soil side of the jth layer;

s11, arranging grounding springs around the tunnel primary support structure, determining the spring stiffness according to the elastic resistance coefficient of surrounding rocks, setting the interaction and other boundary constraints of each part, carrying out grid division on the model, and calculating to obtain the settlement value y of the same position of the tunnel arch springing under the same design working condition _j1 At the moment, the tunnel lining, the internal force of the reinforcing steel bars and the vault settlement value y _d1 ；

S12, calculating the settlement difference value delta y between the arch crown and the arch foot position of the tunnel, wherein the calculation expression is as follows:

Δy＝y _d1 -y _j1 ；

s13, calculating the actual settlement value y of the vault of the tunnel according to the superposition principle _d0 The calculation expression is as follows:

y _d0 ＝y _j0 +Δy。

2. the superposition effect-based shallow-buried weak broken surrounding rock tunnel stress deformation analysis method according to claim 1, wherein the relevant soil layer parameters comprise volume weight, internal friction angle, cohesive force, elastic modulus, Poisson ratio, lateral pressure coefficient and calculated section internal soil layer thickness of each soil layer.

3. The superposition effect-based shallow-buried weak fractured surrounding rock tunnel stress deformation analysis method according to claim 1, wherein relevant structural parameters of the tunnel section comprise tunnel structure size, material parameters, tunnel burial depth, steel bars, steel arches, foot-locking anchor rods and jet grouting pile parameters and distribution.

4. The method for analyzing the stressed deformation of the shallow-buried weak broken surrounding rock tunnel based on the superposition effect as claimed in claim 1, wherein in the tunnel inverted arch-soil layer three-dimensional finite element model established by the stratigraphic structure method, the soil body adopts an elastic-plastic molar coulomb constitutive model, the reinforcing steel bars, the locking anchor rods and the jet grouting piles adopt an elastic-plastic constitutive model, and the lining adopts a concrete damage plastic constitutive model.

5. The method for analyzing the stressed deformation of the shallow soft broken surrounding rock tunnel based on the superposition effect as claimed in claim 1, wherein in the three-dimensional finite element model of the tunnel primary supporting structure established by the loading structure method, the steel bars adopt an elastic-plastic constitutive model, the lining adopts a concrete damage-plastic constitutive model, and parameters of the steel arch frame can be converted into the concrete of the primary supporting structure according to a density and elastic-mold conversion algorithm during modeling.

Images