Method for calculating surrounding rock pressure of tunnel structure through pipe-roofing pre-construction method

Abstract

The invention relates to the field of tunnel engineering, in particular to a method for calculating surrounding rock pressure of a tunnel structure through a pipe-roofing pre-construction method. Compared with an existing tunnel surrounding rock pressure calculation method, the method for calculating the surrounding rock pressure of the tunnel structure constructed through the pipe-roofing pre-building method has the advantages that the construction characteristics of the tunnel structure constructed through the pipe-roofing pre-building method can be accurately reflected by combining a tunnel load forming mechanism of the pre-building lining method, and the construction technology and structural characteristics of the pre-building lining method are embodied.

Description

Technical Field

[0001] The present invention relates to the field of tunnel engineering, and more specifically, to a method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method. Background Art

[0002] In tunnel design, in addition to analogies based on engineering experience, force analysis is generally required. At present, the calculation method recommended by my country's tunnel specifications is mainly the load-structure method. When the tunnel structure is calculated using the load-structure model, the surrounding rock pressure (load) to be borne must be clearly defined. Tunnel surrounding rock pressure generally consists of two parts: one is the loose load, which is the deadweight of the soil in the tensile and detached parts of the surrounding rock; the other is the deformation pressure, which is related to the deformation capacity, structural stiffness and construction timing of the surrounding rock-support. The tunnel surrounding rock pressure is the deformation of the stratum after tunnel excavation, excavation face exposure, and lining support. Therefore, the basis of the existing tunnel surrounding rock pressure is the loose load and deformation pressure formed after the partial excavation or full-section excavation of the tunnel, which leads to the deformation of the stratum.

[0003] When the pipe-curtain prefabrication method is used for tunnel structure construction, the lining is completed before the tunnel is excavated, and then the tunnel is excavated under the protection of the lining. Therefore, the stratum exposure range and load formation mechanism of the tunnel formation process are different from those of existing tunnels. According to the construction method, the pipe-curtain prefabrication method generally builds multiple small-diameter tunnels in the tunnel section and then connects them into an integral tunnel. Its characteristics are: 1. The lining prefabrication process is a continuous interaction of small sections, which eventually forms a large tunnel section influence range; 2. When the overall tunnel is excavated, it is under the protection of the prefabricated lining, and the prefabricated lining will have a certain deformation, and its deformation will also cause a certain stratum deformation and load.

[0004] The existing method for calculating the surrounding rock pressure of tunnel structures is to consider that after the rock and soil within the outer contour of the tunnel is excavated first, an open surface is generated, the stratum is disturbed, and the stress is redistributed, thus acting on the lining to be constructed later. The load action process is "excavation first, then load bearing". However, unlike the existing tunnels, the pre-built lining method is to use the more traditional shield technology or jacking technology to construct a small-section tunnel structure along the outer contour of the tunnel before excavating the rock and soil within the contour of the tunnel. The structure is constructed in the small-section tunnel and connected to form the outer contour of the overall underground structure. Then, the rock and soil inside the tunnel is excavated under the protection of the formed structure, and the internal structure is constructed. The load action process is "load bearing first, then excavation". Therefore, it can be seen that the load formation mechanism of the pre-built lining method tunnel is different from that of the existing dark-cut tunnel, and the structural stress is completely different. The existing tunnel load calculation method does not take into account the characteristics of the precast lining method, that is, it does not take into account the continuous impact of the two stages of lining precast and overall tunnel excavation on the stratum. The calculated load is inconsistent with the actual engineering of the precast lining method. The existing tunnel load calculation method cannot reflect the construction characteristics of the pipe curtain precast method. Therefore, it is necessary to develop a load calculation method that reflects the construction technology and structural characteristics of the precast lining method. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the surrounding rock pressure of a tunnel structure constructed by the pipe-curtain prefabrication method. Combined with the load formation mechanism of the prefabricated lining method tunnel, compared with the existing tunnel surrounding rock pressure calculation method, the method can accurately reflect the construction characteristics of the tunnel structure constructed by the pipe-curtain prefabrication method and embody the construction technology and structural characteristics of the prefabricated lining method.

[0006] In order to achieve these purposes and other advantages according to the present invention, a method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method is provided, comprising the following steps:

[0007] S1. Establish a finite element calculation model of the tunnel structure;

[0008] S2, simulating the surrounding rock damage zone generated by the construction of the pipe-roof pre-support structure in the finite element calculation model, and calculating the horizontal surrounding rock pressure E1 generated by the construction of the pipe-roof pre-support structure;

[0009] S3, simulating tunnel excavation construction in the finite element calculation model under the pre-support condition of the pipe curtain structure, obtaining the surrounding rock damage zone caused by the tunnel excavation construction, and calculating the lateral pressure E2 generated by the tunnel excavation construction;

[0010] S4. Obtain the horizontal surrounding rock pressure e of the pipe-curtain prefabrication method tunnel structure, and take the larger value of the horizontal surrounding rock pressure E1 caused by the construction of the pre-support structure and the lateral pressure E2 caused by the tunnel excavation of the pre-support structure: e=max{E1,E2}.

[0011] Furthermore, the method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method further includes:

[0012] S5. Envelope the surrounding rock damage zone generated by the construction of the pipe-curtain pre-support structure obtained in S2 and the surrounding rock damage zone generated by the tunnel excavation construction obtained in S3, and the surrounding rock deadweight of the surrounding rock damage zone obtained by enveloping is the vertical surrounding rock pressure of the pipe-curtain pre-construction method tunnel structure.

[0013] Furthermore, in the method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, S1 specifically includes:

[0014] S11. Establishing the finite element calculation model based on actual data of the tunnel structure, wherein the actual data of the tunnel structure at least includes: tunnel section dimensions, burial depth, physical and mechanical parameters of the support structure, and physical and mechanical parameters of the surrounding rock;

[0015] S12, determining the material properties and constitutive model of each unit in the finite element calculation model, defining the compression and shear failure limit strain and tensile strength threshold of the surrounding rock, applying boundary constraints and gravity, and performing initial self-weight stress balance on the finite element calculation model.

[0016] Furthermore, in the method for calculating the surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, the calculation method of E1 is as follows:

[0017] E1=λ*Qg (1)

[0018] Where: E1 is the horizontal surrounding rock pressure generated by the construction of the pipe-curtain pre-support structure; Qg is the vertical load generated by the construction of the pipe-curtain pre-support structure; λ is the horizontal side pressure coefficient in the tunnel after the construction of the pipe-curtain pre-support structure.

[0019] in, is the friction angle calculated for the surrounding rock; β is the angle between the fracture surface and the horizontal plane; θ is the sliding surface friction angle.

[0020] Furthermore, in the method for calculating the surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, the calculation method of Qg is as follows:

[0021] S2.1. Simulate the excavation construction of each pipe curtain respectively to obtain the surrounding rock damage zone caused by the excavation of each pipe curtain. The surrounding rock damage zone caused by the construction of the pipe curtain pre-support structure is the envelope of the surrounding rock damage zone caused by all pipe curtain excavation;

[0022] S2.2. Calculate the self-weight Pg of the surrounding rock in the surrounding rock damage zone caused by the construction of the pipe-roof pre-support structure, Qg = Pg.

[0023] Furthermore, in the method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, S2.1 specifically includes:

[0024] S2.1.1. Combined with the stratum loss during the pipe-curtain excavation process, the rock and soil units in the first pipe-curtain are killed, the pipe-curtain structure units are activated, the excavation of the first pipe-curtain is simulated, and the surrounding rock that exceeds the compression-shear failure limit strain and tensile strength threshold is taken as the surrounding rock failure zone caused by the excavation of the first pipe-curtain;

[0025] S2.1.2. Repeat the operation of S2.1.1, and simulate the excavation of other pipe curtains in the finite element calculation model in turn to obtain the surrounding rock damage zone caused by the excavation of each pipe curtain. The surrounding rock damage zone caused by the construction of the pipe curtain pre-support structure is the envelope of the surrounding rock damage zone caused by the excavation of all pipe curtains.

[0026] Furthermore, in the method for calculating the surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, the calculation method of E2 is as follows:

[0027] E2=λ*Ug (2)

[0028] Where: Ug is the vertical load generated by tunnel excavation construction; λ is the horizontal side pressure coefficient in the tunnel after tunnel excavation construction.

[0029] Furthermore, in the method for calculating the surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, the calculation method of Ug is as follows:

[0030] S3.1. Kill the rock and soil units in the tunnel by section or full section, simulate the excavation of the soil in the tunnel, and take the surrounding rock that exceeds the compression-shear failure limit strain and tensile strength threshold as the surrounding rock failure zone caused by tunnel excavation construction;

[0031] S3.2. Calculate the self-weight Ug of the surrounding rock in the surrounding rock damage zone caused by tunnel excavation construction, where Ug = Sg.

[0032] The beneficial effects of the present invention are:

[0033] The surrounding rock pressure calculation method of the present invention aims at the characteristics of the pipe curtain preconstruction method. By establishing a finite element calculation model of the tunnel structure, the construction of the pipe curtain pre-support structure and the tunnel construction under the pipe curtain pre-support are simulated respectively, and the damage zone of the tunnel excavation construction under the conditions of pipe curtain pre-support and pipe curtain structure pre-support is obtained, thereby calculating the surrounding rock pressure of the tunnel structure of the pipe curtain preconstruction method. Compared with the existing tunnel surrounding rock pressure calculation method, this method can accurately reflect the construction characteristics of the pipe curtain preconstruction method and embody the construction process and structural characteristics of the pre-built lining method.

[0034] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1It is a flow chart of the method for calculating the surrounding rock pressure of the tunnel structure using the pipe-roof prefabrication method of the present invention;

[0036] Figure 2 It is a schematic diagram of the tunnel structure of the pipe-roof prefabrication method of the present invention;

[0037] Figure 3 It is a simplified schematic diagram of the cross section of the tunnel structure of the pipe-roof prefabrication method of the present invention;

[0038] Figure 4 It is a schematic diagram of a finite element calculation model of a tunnel structure using the pipe-roof prefabrication method according to the present invention;

[0039] Figure 5 It is a cloud diagram of the initial self-weight stress field of the tunnel structure of the pipe-roof prefabrication method described in the present invention;

[0040] Figure 6 A schematic diagram of the surrounding rock damage zone caused by the excavation of a single pipe curtain in the pipe curtain prefabrication method tunnel structure of the present invention;

[0041] Figure 7 A schematic diagram of the surrounding rock damage zone generated by the construction of the pipe-roof pre-support structure of the pipe-roof prefabrication method tunnel structure of the present invention;

[0042] Figure 8 It is a schematic diagram of the surrounding rock damage zone produced by the tunnel excavation construction of the pipe-roof prefabricated tunnel structure described in the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0044] It should be noted that, in the description of the present invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0045] like Figure 1-Figure 8 As shown, an embodiment of the present invention provides a method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, comprising the following steps:

[0046] S1. Obtain the structural form of the pipe-roof prefabricated tunnel structure (such as Figure 2 and Figure 3As shown in the figure, the geological survey data of the tunnel location and the actual working conditions, including at least the tunnel section size, burial depth, physical and mechanical parameters of the support structure and the physical and mechanical parameters of the surrounding rock, establish a finite element calculation model of the tunnel structure (as shown in the figure), ... establish a finite element calculation model of the tunnel structure (as shown in the figure), establish a finite element calculation model of the tunnel structure (as shown in the figure), establish a finite element calculation model of the tunnel structure (as shown in the figure), establish a finite element calculation model of the tunnel structure (as shown in the figure), establish a finite element calculation model of the tunnel structure (as shown in the figure), establish a finite element calculation model of the tunnel structure (as shown in the figure), establish a finite Figure 4 As shown in the figure), determine the material properties and constitutive model of each unit in the finite element calculation model, define the compression and shear failure limit strain and tensile strength threshold of the surrounding rock, apply fixed constraints on both sides and the bottom of the model, and apply gravity load, perform initial stress balance on the finite element calculation model, and use it as the initial state of the tunnel structure construction of the pipe-roof prefabrication method (as shown in the figure). Figure 5 shown).

[0047] Among them, in order to eliminate the influence of boundary conditions, 3 to 5 times the outer contour of the tunnel excavation should be selected on both sides and the bottom of the model; in order to ensure the accuracy of the calculation results, the grid close to the tunnel area in the finite element calculation model should be appropriately encrypted.

[0048] S2. Simulating the excavation construction of each pipe curtain in the tunnel structure one by one in the finite element calculation model, obtaining the surrounding rock damage zone generated by the construction of the pipe curtain pre-support structure, and calculating the vertical surrounding rock pressure and horizontal surrounding rock pressure generated by the construction of the pipe curtain pre-support structure;

[0049] Among them, S2 specifically includes:

[0050] S2.1. Simulate the excavation construction of each pipe curtain respectively to obtain the surrounding rock damage zone caused by the excavation of each pipe curtain. The surrounding rock damage zone caused by the construction of the pipe curtain pre-support structure is the envelope of the surrounding rock damage zone caused by all pipe curtain excavation;

[0051] Among them, S2.1 specifically includes:

[0052] S2.1.1. Combined with the stratum loss during the pipe curtain excavation process, the rock and soil units in the first pipe curtain are killed, the pipe curtain structure units are activated, the excavation of the first pipe curtain is simulated, and the surrounding rock that exceeds the compression shear failure limit strain and tensile strength threshold is taken as the surrounding rock failure zone caused by the excavation of the first pipe curtain (such as Figure 6 As shown), marked as F1;

[0053] The calculation of formation loss can be achieved using existing technology. It can comprehensively consider factors such as engineering geology, hydrogeological conditions, construction methods and technologies (differences in the size of the pipe curtain cutter head and the pipe curtain structure, and the synchronous grouting strength-time curve) to calculate the formation loss rate of the small-section pipe curtain. The above-mentioned formation loss rate simulation can be achieved by adjusting the stress release coefficient or the section contraction.

[0054] S2.1.2, repeat the operation of S2.1.1, and simulate the excavation of the second pipe curtain, the third pipe curtain to the last pipe curtain in the finite element calculation model in turn, and mark them as: F2, F2, ... Fi, and the i-th pipe curtain is the last pipe curtain. The damage zone caused by the excavation of the i-th pipe curtain is the damage zone of the envelope F1, F2, ... Fi, and the damage zone caused by the construction of the pipe curtain structure is the envelope of the damage zone caused by the construction of all pipe curtains, which is recorded as Fg. Figure 7 As shown, the red and blue parts are the envelope areas of the damage zone during the entire construction process.

[0055] The surrounding rock damage area caused by all pipe curtain excavation is enclosed as the surrounding rock damage area caused by the construction of the pipe curtain pre-support structure.

[0056] S2.2. Calculate the horizontal surrounding rock pressure generated by the construction of the pipe-roof pre-support structure. The calculation method is as follows:

[0057] E1=λ1*Qg (1)

[0058] Where: E1 is the horizontal surrounding rock pressure generated by the construction of the pipe-roof pre-support structure; Qg is the vertical load generated by the construction of the pipe-roof pre-support structure; the calculation method is shown in the following formulas (3) and (4):

[0059]

[0060] in, is the friction angle of surrounding rock; β is the angle between the fracture surface and the horizontal plane; θ is the friction angle of sliding surface. The values ​​of the above parameters can refer to the relevant provisions on the calculation method of surrounding rock pressure of shallow buried tunnels in the "Railway Tunnel Design Code" (TB10003-2016) or "Highway Tunnel Design Code" (JTG3370.1-2018).

[0061] At the same time, the self-weight of the surrounding rock in the surrounding rock damage zone in the pipe-curtain structure is recorded as Pg, and the vertical load caused by the pre-support construction is recorded as Qg, Qg=Pg, and the self-weight of the surrounding rock in the surrounding rock damage zone caused by the construction of the pipe-curtain pre-support structure is the vertical load generated by the construction of the pipe-curtain pre-support structure.

[0062] S3. Simulate tunnel excavation construction under the pre-support condition of the pipe-roof structure to obtain the surrounding rock damage zone caused by the tunnel excavation construction, and calculate the vertical surrounding rock pressure and lateral pressure caused by the tunnel excavation construction;

[0063] Among them, S3 specifically includes:

[0064] S3.1. By killing the rock and soil units in the tunnel in sections or in full sections, simulating the excavation of the soil in the tunnel, calculating the distribution range of the damage zone under 100% stress release of the rock and soil in the tunnel under the pre-support of the pipe-roof structure, the surrounding rock that exceeds the compression-shear damage limit strain and tensile strength threshold is regarded as the surrounding rock damage zone caused by the tunnel excavation construction;

[0065] S3.2. Calculate the lateral pressure generated by tunnel excavation construction. The calculation method is as follows:

[0066] E2=λ*Ug (2)

[0067] Where: E2 is the horizontal surrounding rock pressure generated by tunnel excavation construction; Ug is the vertical load generated by tunnel excavation construction; the calculation method of λ is as follows (5):

[0068]

[0070] The deadweight of the surrounding rock in the surrounding rock damage zone caused by tunnel excavation construction is recorded as Sg, and the vertical load caused by tunnel construction under pre-support is recorded as Ug, Ug = Sg, and the deadweight of the surrounding rock in the surrounding rock damage zone caused by tunnel excavation construction is the vertical load caused by tunnel excavation construction.

[0071] S4, enveloping the surrounding rock damage area generated by the pipe-roof pre-support structure construction obtained in S2 and the surrounding rock damage area generated by the tunnel excavation construction obtained in S3, and obtaining the final surrounding rock damage area (such as Figure 8 As shown, the blue part is the surrounding rock damage zone caused by the construction of the pipe-curtain pre-support structure, and the red part is the surrounding rock damage zone caused by the tunnel excavation construction). The deadweight of the surrounding rock in the damage zone above the pipe-curtain structure is recorded as Ps, and the vertical load caused by the tunnel excavation construction is recorded as qs, qs=Ps. The deadweight of the surrounding rock in the final surrounding rock damage zone is taken as the vertical surrounding rock pressure of the pipe-curtain pre-construction tunnel structure. The larger value of the horizontal surrounding rock pressure generated by the pipe-curtain pre-support structure construction obtained by S2 and the lateral pressure generated by the tunnel excavation construction obtained by S3 is taken as the horizontal surrounding rock pressure of the pipe-curtain pre-construction tunnel structure, that is, the horizontal surrounding rock pressure of the pipe-curtain pre-construction tunnel structure e=max{E1,E2}.

[0072] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method, characterized in that: The following steps are involved: S1. Establish a finite element calculation model of the tunnel structure; S2, simulating the surrounding rock damage zone generated by the construction of the pipe-roof pre-support structure in the finite element calculation model, and calculating the horizontal surrounding rock pressure E1 generated by the construction of the pipe-roof pre-support structure; S3, simulating tunnel excavation construction in the finite element calculation model under the pre-support condition of the pipe curtain structure, obtaining the surrounding rock damage zone caused by the tunnel excavation construction, and calculating the lateral pressure E2 generated by the tunnel excavation construction; S4. Obtain the horizontal surrounding rock pressure e of the pipe-curtain prefabrication method tunnel structure, and take the larger value of the horizontal surrounding rock pressure E1 caused by the construction of the pre-support structure and the lateral pressure E2 caused by the tunnel excavation of the pre-support structure: e=max{E1,E2}.

2. The method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method according to claim 1, characterized in that: Also includes: S5. Envelope the surrounding rock damage zone generated by the construction of the pipe-curtain pre-support structure obtained in S2 and the surrounding rock damage zone generated by the tunnel excavation construction obtained in S3, and the surrounding rock deadweight of the surrounding rock damage zone obtained by enveloping is the vertical surrounding rock pressure of the pipe-curtain pre-construction method tunnel structure.

3. The method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method according to claim 1, characterized in that: S1 specifically includes: S11. Establishing the finite element calculation model based on actual data of the tunnel structure, wherein the actual data of the tunnel structure at least includes: tunnel section dimensions, burial depth, physical and mechanical parameters of the support structure, and physical and mechanical parameters of the surrounding rock; S12, determining the material properties and constitutive model of each unit in the finite element calculation model, defining the compression and shear failure limit strain and tensile strength threshold of the surrounding rock, applying boundary constraints and gravity, and performing initial self-weight stress balance on the finite element calculation model.

4. The method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method as claimed in claim 3, characterized in that: The calculation method of E1 is as follows: E1=λ*Qg (1) Where: E1 is the horizontal surrounding rock pressure generated by the construction of the pipe-curtain pre-support structure; Qg is the vertical load generated by the construction of the pipe-curtain pre-support structure; λ is the horizontal lateral pressure coefficient.

5. The method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method as claimed in claim 4, characterized in that: The calculation method of Qg is as follows: S2.

1. Simulate the excavation construction of each pipe curtain respectively to obtain the surrounding rock damage zone caused by the excavation of each pipe curtain. The surrounding rock damage zone caused by the construction of the pipe curtain pre-support structure is the envelope of the surrounding rock damage zone caused by all pipe curtain excavation; S2.

2. Calculate the self-weight Pg of the surrounding rock in the surrounding rock damage zone caused by the construction of the pipe-roof pre-support structure, Qg = Pg.

6. The method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method as claimed in claim 5, characterized in that: S2.1 specifically includes: S2.1.

1. Combined with the stratum loss during the pipe-curtain excavation process, the rock and soil units in the first pipe-curtain are killed, the pipe-curtain structure units are activated, the excavation of the first pipe-curtain is simulated, and the surrounding rock that exceeds the compression-shear failure limit strain and tensile strength threshold is taken as the surrounding rock failure zone caused by the excavation of the first pipe-curtain; S2.1.

2. Repeat the operation of S2.1.1, and simulate the excavation of other pipe curtains in the finite element calculation model in turn to obtain the surrounding rock damage zone caused by the excavation of each pipe curtain. The surrounding rock damage zone caused by the construction of the pipe curtain pre-support structure is the envelope of the surrounding rock damage zone caused by the excavation of all pipe curtains.

7. The method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method as claimed in claim 3, characterized in that: The calculation method of E2 is as follows: E2=λ*Ug (2) Where: Ug is the vertical load generated by tunnel excavation construction; λ is the horizontal lateral pressure coefficient.

8. The method for calculating surrounding rock pressure of a tunnel structure using a pipe-roof prefabrication method according to claim 7, characterized in that: The calculation method of Ug is as follows: S3.

1. Kill the rock and soil units in the tunnel by section or full section, simulate the excavation of the soil in the tunnel, and take the surrounding rock that exceeds the compression-shear failure limit strain and tensile strength threshold as the surrounding rock failure zone caused by tunnel excavation construction; S3.

2. Calculate the self-weight Ug of the surrounding rock in the surrounding rock damage zone caused by tunnel excavation construction, where Ug = Sg.

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