A method for evaluating large deformation of surrounding rock in a layered rock mass tunnel

Abstract

The present invention discloses a method for evaluating large deformation of surrounding rock in a layered rock mass tunnel. The evaluation method includes classifying the surrounding rock of the tunnel in the layered rock mass into multiple grades according to its large deformation degree, and each large deformation grade is determined through the following process: obtaining the maximum principal stress σ of the surrounding rock in the tunnel site area, the anisotropic strength of the rock mass, the layer thickness and the lithology type, and the groundwater type, and making a preliminary evaluation of the large deformation grade; then, correcting the preliminary evaluation grade of the large deformation through the included angle α between the obtained maximum principal stress and the tunnel axis and the bedding occurrence information of the rock mass to obtain the corrected large deformation grade. The present invention can accurately evaluate the risk grade of large deformation disasters of layered surrounding rock through multi-index synthesis, and improves the accuracy of grading.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mass engineering. Background Art

[0002] In fields such as mining engineering, water conservancy and hydropower engineering, tunnel engineering, and underground oil and gas storage engineering, the surrounding rock is mainly layered rock mass. The rock mass contains parallel distributed layered weak planes, making its mechanical properties significantly anisotropic. Under the action of high stress, bedding structure, groundwater and other factors, it is prone to large deformation disasters. The large deformation of layered surrounding rock usually shows characteristics such as large deformation amount, high deformation rate, long duration, and large depth of surrounding rock failure, threatening the personal safety of construction workers, damaging construction monitoring equipment, delaying the progress of project construction, and posing a serious threat to the safe, efficient construction and normal operation of underground projects. Therefore, it is very necessary to classify the large deformation of layered rock mass tunnels to support the surrounding rock with different large deformation risk levels more pertinently, reduce the blindness of support measures and reduce the occurrence of large deformation disasters.

[0003] In the prior art, large deformation classification is usually carried out with relatively single indicators, which does not match the complex large deformation occurrence mechanism of layered rock mass due to its special bedding structure, resulting in the inability of existing large deformation classification methods to be widely applied and referenced. For example, in current engineering practice, the strength-stress ratio or its equivalent form is mostly used as a single indicator to divide large deformation into 3 levels or 4 levels. In this classification form, factors such as the anisotropy and layer thickness of layered rock mass are not considered, and the reference value of the classification result is insufficient; or the three discriminant methods for large deformation of surrounding rock proposed in the existing patent documents 201811170774.3, 201810245461.3, and 201810228740.9 all have relatively single discriminant indicators and do not consider the mechanical particularity of layered rock mass, and their guiding significance for the evaluation and classification of large deformation of layered surrounding rock is also very limited. Summary of the Invention

[0004] Aiming at the defects of the prior art, the purpose of the present invention is to provide a new evaluation method for large deformation of surrounding rock of layered rock mass tunnels, which can accurately classify the large deformation of surrounding rock of layered rock mass tunnels through comprehensive, comprehensive and easily obtainable indicators, so as to accurately evaluate the risk level of large deformation disasters of layered surrounding rock and expand the practical application scope of the classification evaluation method.

[0005] The technical solution of the present invention is as follows:

[0006] An evaluation method for large deformation of surrounding rock of layered rock mass tunnels, which includes:

[0007] Classify the surrounding rock of the tunnel of layered rock mass into 0, 1, 2,..., n grades according to its large deformation degree, where grade 0 indicates no large deformation, and each subsequent grade indicates large deformation, and the severity of large deformation increases in turn;

[0008] Among them, the determination of each level includes:

[0009] Obtain the maximum principal stress σ of the tunnel surrounding rock to be evaluated in the tunnel site area, where the tunnel surrounding rock is a layered rock mass;

[0010] Obtain the rock mass layer thickness, anisotropy degree, and lithology type of the tunnel surrounding rock to be evaluated in the tunnel site area; among them, the anisotropy degree is divided into strong anisotropy and weak anisotropy;

[0011] Obtain the groundwater information in the tunnel site area, including the groundwater development status;

[0012] Obtain the included angle α between the maximum principal stress σ and the tunnel axis;

[0013] Obtain the bedding attitude information of the tunnel surrounding rock to be evaluated in the tunnel site area, and obtain the bedding dip angle γ of the surrounding rock and the included angle θ between the bedding strike and the tunnel axis according to the obtained bedding attitude information;

[0014] According to the maximum principal stress σ, the rock mass layer thickness, anisotropy degree, and lithology type, and the groundwater information, conduct a preliminary evaluation of the large deformation degree of the tunnel surrounding rock to be evaluated, and obtain the preliminary evaluation grade v1 of the surrounding rock large deformation in the tunnel site area 1 ;

[0015] According to the included angle α between the maximum principal stress σ and the tunnel axis, the bedding dip angle γ, and the included angle θ between the bedding strike and the tunnel axis, obtain the large deformation grade correction parameter M;

[0016] According to the large deformation grade correction parameter M, correct the preliminary evaluation grade v1 to obtain the final large deformation grade v2.

[0017] According to some preferred embodiments of the present invention, the obtaining of the maximum principal stress σ includes:

[0018] After the tunnel is excavated, select the area where the surrounding rock deformation exceeds the reserved deformation amount or the tunnel section convergence deformation amount is greater than 3% of the tunnel section as a typical large deformation area;

[0019] Inject grout into the surrounding rock of the typical large deformation area through a quick-setting material, and the grouting depth is greater than three times the tunnel diameter;

[0020] After the grouting stone body after the grouting treatment is fully solidified, use the hollow inclusion method to measure the magnitude and direction of its maximum principal stress σ.

[0021] According to some preferred embodiments of the present invention, the degree of anisotropy is determined by the ratio of the wave velocities in the direction parallel to the bedding plane and the direction perpendicular to the bedding plane in the rock mass. Among them, when the ratio of the wave velocity in the direction parallel to the bedding plane to the wave velocity in the direction perpendicular to the bedding plane is greater than 1.2, it is strongly anisotropic; otherwise, it is weakly anisotropic.

[0022] According to some preferred embodiments of the present invention, the rock mass layer thickness includes medium-thick layers, thin layers, and extremely thin layers. Among them, layers with a thickness greater than 30 cm are medium-thick layers, layers with a thickness less than 30 cm and greater than 1 cm are thin layers, and layers with a thickness less than 1 cm are extremely thin layers.

[0023] According to some preferred embodiments of the present invention, the lithology types include relatively soft rocks, soft rocks, and extremely soft rocks, which are determined by standard lithology classification methods.

[0024] According to some preferred embodiments of the present invention, the groundwater development status includes: dry, moist, or dripping water, and raining or gushing water.

[0025] According to some preferred embodiments of the present invention, the large deformation grades include four grades: 0, I, II, III, and IV, and the preliminary evaluation grade v1 is determined by the following rating model:

[0026] When the layered rock mass is a medium-thick soft rock with strong anisotropy or a thin-layer relatively soft rock or soft rock with weak anisotropy:

[0027] If the groundwater development status is dry and σ > 25 MPa, then v 1 = I;

[0028] If the groundwater development status is moist or dripping water and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or if σ > 25 MPa, then v 1 = II;

[0029] If the groundwater development status is raining or gushing water and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or if σ > 25 MPa, then v 1 = II;

[0030] When the layered rock mass is a thin-layer soft rock with strong anisotropy or an extremely thin-layer relatively soft rock - soft rock with weak anisotropy:

[0031] If the groundwater development status is dry and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or if σ > 25 MPa, then v 1 = II;

[0032] If the groundwater development status is moist or dripping water and 15 MPa < σ ≤ 25 MPa, then v1 = II, or if σ > 25 MPa, then v 1 = II;

[0033] If the groundwater development condition is shower or gushing water, and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or if σ > 25 MPa, then v 1 = III;

[0034] When the layered rock mass is extremely thin soft rock - extremely soft rock with strong anisotropy:

[0035] If the groundwater development condition is dry, and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or if σ > 25 MPa, then v 1 = III;

[0036] If the groundwater development condition is wet or dripping water, and σ ≤ 15 MPa, then v 1 = I, or if 15 MPa < σ ≤ 25 MPa, then v 1 = III, or if σ > 25 MPa, then v 1 = III;

[0037] If the groundwater development condition is wet or dripping water, and σ ≤ 15 MPa, then v 1 = I, or if 15 MPa < σ ≤ 25 MPa, then v 1 = III, or if σ > 25 MPa, then v 1 = III;

[0038] If the groundwater development condition is shower or gushing water, and σ ≤ 15 MPa, then v 1 = I, or if 15 MPa < σ ≤ 25 MPa, then v 1 = III, or if σ > 25 MPa, then v 1 = IV.

[0039] According to some preferred embodiments of the present invention, the large deformation grade correction parameter M is obtained through the following determination model:

[0040] When 0° ≤ α ≤ 30°, if γ > 20° and θ ≤ 30°, then M = 1;

[0041] When 30° < α ≤ 60°, if γ ≤ 20°, then M = 1; if γ > 20° and 30° < θ ≤ 60°, then M = 1; if γ > 20° and θ ≤ 30°, then M = 2;

[0042] When 60° < α ≤ 90°, if γ ≤ 20°, then M = 2; if γ > 20° and θ > 60°, then M = 1; if γ > 20° and 30° < θ ≤ 60°, then M = 1; if γ > 20° and θ ≤ 30°, then M = 3.

[0043] According to some preferred embodiments of the present invention, the large deformation level includes four levels: 0, I, II, III, and IV, and the large deformation level v2 is determined by the following calculation model:

[0044] When M = 1,

[0045] When M = 2,

[0046] When M = 3, v 2 = IV.

[0047] The present invention combines the maximum principal stress in the tunnel site area, the anisotropy of layered rock mass, layer thickness, lithology, and groundwater information to preliminarily evaluate the large deformation level of layered surrounding rock. By calculating the large deformation level correction parameters in combination with the included angle between the in-situ stress and the tunnel axis, the included angle between the bedding strike and the tunnel axis, and the bedding dip angle, and using the large deformation level correction parameters to correct the preliminary evaluation level of the large deformation of the layered surrounding rock in the tunnel site area, it can evaluate the risk level of the large deformation disaster of the layered surrounding rock, and the selected indicators are relatively comprehensive and easy to obtain, improving the classification accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic flow chart of the large deformation evaluation method of the present invention in the specific embodiment.

[0049] Figure 2 It is a schematic diagram of the acquisition method of the included angle θ between the bedding strike and the tunnel axis and the bedding dip angle γ of the present invention in the specific embodiment. SPECIFIC EMBODIMENTS

[0050] The present invention will be described in detail below in conjunction with the embodiments and the drawings. However, it should be understood that the embodiments and the drawings are only used for exemplary description of the present invention and do not constitute any limitation to the protection scope of the present invention. All reasonable transformations and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0051] Example 1

[0052] As Figure 1 shown, the large deformation classification of the surrounding rock of the layered rock mass tunnel is carried out through the following steps:

[0053] Step 1: Divide the large deformation grade v of the layered surrounding rock into four grades: 0, I, II, and III, where 0 represents no large deformation, and grades I, II, and III represent large deformation with the severity of deformation increasing in turn.

[0054] Step 2: Obtain the magnitude and direction of the maximum principal stress σ in the tunnel site area, including: after tunnel excavation, select the area where the surrounding rock deformation exceeds the reserved deformation amount or the tunnel section convergence deformation amount is greater than 3% of the tunnel section as a typical large deformation area, grout the surrounding rock in this area with a quick-setting material, and the grouting depth is greater than three times the tunnel diameter. After the grouting stone body is fully solidified, use the hollow inclusion method to measure the magnitude and direction of the maximum principal stress σ.

[0055] Step 3: Obtain the anisotropy, layer thickness, and lithology information of the layered rock mass in the tunnel site area, including:

[0056] Test along the parallel or perpendicular bedding direction through a wave velocity meter or acoustic logging instrument to obtain the wave velocities in the parallel bedding direction and perpendicular bedding direction in the layered rock mass. Divide those with the ratio of the wave velocity in the parallel bedding direction to the wave velocity in the perpendicular bedding direction greater than 1.2 into strong anisotropy, otherwise into weak anisotropy. Thus, divide the anisotropy of the layered rock mass into two levels: {strong, weak};

[0057] Obtain the thickness of the layered rock mass, i.e., the layer thickness, through a scale, and divide the layer thickness into three levels: {medium thickness, thin, extremely thin}. A layer with a thickness greater than 30 cm is a medium-thick layer, a layer with a thickness less than 30 cm and greater than 1 cm is a thin layer, and a layer with a thickness less than 1 cm is an extremely thin layer;

[0058] According to the lithology classification method in the "National Standard of the People's Republic of China: Standard for Classification of Engineering Rock Masses" (GB / T 50218 - 2014), divide the surrounding rock into three levels: {relatively soft, soft, extremely soft}.

[0059] Step 4: Obtain the groundwater information in the tunnel site area, including the groundwater development status.

[0060] Step 5: According to the magnitude of the maximum principal stress σ in the tunnel site area, the anisotropy, layer thickness, lithology information, and groundwater information of the layered rock mass, preliminarily evaluate the large deformation grade of the layered surrounding rock to obtain the preliminary evaluation grade v of the surrounding rock large deformation in the tunnel site area 1 , as follows:

[0061] When the layered rock mass is a medium-thick soft rock with strong anisotropy or a thin relatively soft rock or soft rock with weak anisotropy:

[0062] If the groundwater is dry and σ > 25 MPa, then v 1 = I;

[0063] If the groundwater is wet or dripping, and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or σ > 25 MPa, then v 1 = II;

[0064] If the groundwater is raining or gushing, and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or σ > 25 MPa, then v 1 = II;

[0065] When the layered rock mass is strongly anisotropic thin soft rock or weakly anisotropic extremely thin soft rock - soft rock:

[0066] If the groundwater is dry, and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or σ > 25 MPa, then v 1 = II;

[0067] If the groundwater is wet or dripping, and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or σ > 25 MPa, then v 1 = II;

[0068] If the groundwater is raining or gushing, and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or σ > 25 MPa, then v 1 = III;

[0069] When the layered rock mass is strongly anisotropic extremely thin soft rock - extremely soft rock:

[0070] If the groundwater is dry, and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or σ > 25 MPa, then v 1 = III;

[0071] If the groundwater is wet or dripping, and σ ≤ 15 MPa, then v 1 = I, or 15 MPa < σ ≤ 25 MPa, then v 1 = III, or σ > 25 MPa, then v 1 = III;

[0072] If the groundwater is wet or dripping, and σ ≤ 15 MPa, then v 1 = I, or 15 MPa < σ ≤ 25 MPa, then v 1 = III, or σ > 25 MPa, then v 1 = III;

[0073] If the groundwater is raining or gushing, and σ ≤ 15 MPa, then v1 = I, or 15 MPa < σ ≤ 25 MPa, then v 1 = III, or σ > 25 MPa, then v 1 = IV.

[0074] The above process is shown in Table 1 as follows:

[0075] Table 1

[0076]

[0077] Step 6: According to the design data, obtain the included angle α between the maximum principal stress σ measured in Step 2 in the tunnel site area and the tunnel axis.

[0078] Step 7: Obtain the bedding attitude information of the layered rock mass in the tunnel site area through on-site investigation, including bedding strike, dip direction, and dip angle; according to the bedding attitude information and design data, obtain the included angle θ between the bedding strike and the tunnel axis and the bedding dip angle γ, as shown in the appendix Figure 2 as follows.

[0079] Step 8: According to the included angle α between the maximum principal stress in the tunnel site area and the tunnel axis, the included angle θ between the bedding strike and the tunnel axis, and the bedding dip angle γ, calculate the large deformation grade correction parameter M as follows:

[0080] When 0° ≤ α ≤ 30°, if γ > 20° and θ ≤ 30°, then M = 1;

[0081] When 30° < α ≤ 60°, if γ ≤ 20°, then M = 1; if γ > 20° and 30° < θ ≤ 60°, then M = 1; if γ > 20° and θ ≤ 30°, then M = 2;

[0082] When 60° < α ≤ 90°, if γ ≤ 20°, then M = 2; if γ > 20° and θ > 60°, then M = 1; if γ > 20° and 30° < θ ≤ 60°, then M = 1; if γ > 20° and θ ≤ 30°, then M = 3.

[0083] The above process is shown in Table 2 as follows:

[0084] Table 2

[0085]

[0086] Step 9: Correct the initial evaluation grade v of the large deformation of the layered surrounding rock in the tunnel site area according to the large deformation grade correction parameter M 1 to obtain the corrected grade v of the large deformation of the surrounding rock in the tunnel site area 2 , as follows:

[0087] When M = 1,

[0088] When M = 2,

[0089] When M = 3, v 2 = IV.

[0090] The above grading evaluation method for large deformation fully considers the mechanical particularity of layered rock mass, and its guiding role in practice is more effective and reliable than other existing grading methods.

[0091] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for evaluating large deformation of surrounding rock in a layered rock mass tunnel, characterized in that, it includes: Classify the surrounding rock of the tunnel in the layered rock mass into 0, 1, 2, …, n grades according to its large deformation degree, where grade 0 indicates no large deformation, and each subsequent grade indicates large deformation, and the severity of large deformation increases in turn; Among them, the determination of each grade includes: Obtain the maximum principal stress σ of the surrounding rock of the tunnel to be evaluated in the tunnel site area, and the surrounding rock is a layered rock mass; Obtain the rock layer thickness, anisotropy degree and lithology type of the surrounding rock of the tunnel to be evaluated in the tunnel site area; among them, the anisotropy degree is divided into strong anisotropy and weak anisotropy; Obtain the groundwater information in the tunnel site area, including the development status of groundwater; Obtain the included angle α between the maximum principal stress σ and the tunnel axis; Obtain the bedding attitude information of the surrounding rock of the tunnel to be evaluated in the tunnel site area, and obtain the bedding dip angle γ of the surrounding rock and the included angle θ between the bedding strike and the tunnel axis according to the obtained bedding attitude information; According to the maximum principal stress σ, the thickness of the rock mass layer, the degree of anisotropy and the lithology type, and the groundwater information, a preliminary assessment of the large deformation degree of the tunnel surrounding rock to be evaluated is carried out to obtain the preliminary evaluation grade v of the surrounding rock large deformation in the tunnel site area 1 ; Obtain the large deformation grade correction parameter M according to the included angle α between the maximum principal stress σ and the tunnel axis, the bedding dip angle γ and the included angle θ between the bedding strike and the tunnel axis; Modify the initial evaluation level v according to the large deformation level correction parameter M 1 to obtain the final large deformation level v 2 .

2. The evaluation method according to claim 1, characterized in that, The obtaining of the maximum principal stress σ includes: After the tunnel is excavated, select the area where the surrounding rock deformation exceeds the reserved deformation amount or the tunnel section convergence deformation amount is greater than 3% of the tunnel section as a typical large deformation area; Inject slurry into the surrounding rock of the typical large deformation area through a quick-setting material, and the injection depth is greater than three times the tunnel diameter; After the grouting stone body after the grouting treatment is fully solidified, use the hollow inclusion method to measure the magnitude and direction of its maximum principal stress σ.

3. The evaluation method according to claim 1, characterized in that, The anisotropy degree is determined by the ratio of the wave velocities in the direction parallel to the bedding and perpendicular to the bedding in the rock mass. Among them, when the ratio of the wave velocity in the direction parallel to the bedding to the wave velocity in the direction perpendicular to the bedding is greater than 1.2, it is strong anisotropy, otherwise it is weak anisotropy.

4. The evaluation method according to claim 1, characterized in that, The rock layer thickness includes medium-thick layer, thin layer and extremely thin layer. Among them, the layer thickness greater than 30 cm is a medium-thick layer, the layer thickness less than 30 cm and greater than 1 cm is a thin layer, and the layer thickness less than 1 cm is an extremely thin layer.

5. The evaluation method according to claim 1, characterized in that, The lithology type includes relatively soft rock, soft rock and extremely soft rock, and is determined by a standard lithology classification method.

6. The evaluation method according to claim 1, characterized in that, The development status of groundwater includes: dry, moist or dripping water and raining or gushing water.

7. The evaluation method according to claim 1, characterized in that, The large deformation levels include four levels: 0, I, II, III, and IV, and the preliminary evaluation level v 1 is determined by the following rating model: When the layered rock mass is a medium-thick soft rock with strong anisotropy or a thin-layer relatively soft rock or soft rock with weak anisotropy: If the groundwater development condition is dry and σ > 25 MPa, then v 1 = I; If the groundwater development condition is wet or dripping water, and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or σ > 25 MPa, then v 1 = II; If the groundwater development condition is shower or gushing water, and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or σ > 25 MPa, then v 1 = II; When the layered rock mass is a thin-layer soft rock with strong anisotropy or an extremely thin-layer relatively soft rock - soft rock with weak anisotropy: If the groundwater development condition is dry, and 15 MPa < σ ≤ 25 MPa, then v 1 = I, or σ > 25 MPa, then v 1 = II; If the groundwater development condition is wet or dripping water, and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or σ > 25 MPa, then v 1 = II; If the groundwater development condition is rain-like or gushing water, and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or σ > 25 MPa, then v 1 = III; When the layered rock mass is an extremely thin-layer soft rock - extremely soft rock with strong anisotropy: If the groundwater development condition is dry and 15 MPa < σ ≤ 25 MPa, then v 1 = II, or if σ > 25 MPa, then v 1 = III; If the groundwater development condition is wet or dripping water, and σ ≤ 15 MPa, then v 1 = I, or 15 MPa < σ ≤ 25 MPa, then v 1 = III, or σ > 25 MPa, then v 1 = III; If the groundwater development condition is rain-like or gushing water, and σ ≤ 15 MPa, then v 1 = I, or 15 MPa < σ ≤ 25 MPa, then v 1 = III, or σ > 25 MPa, then v 1 = IV.

8. The evaluation method according to claim 1, characterized in that, The large deformation level correction parameter M is obtained through the following determination model: When 0° ≤ α ≤ 30°, if γ > 20° and θ ≤ 30°, then M = 1; When 30° < α ≤ 60°, if γ ≤ 20°, then M = 1; if γ > 20° and 30° < θ ≤ 60°, then M = 1; if γ > 20° and θ ≤ 30°, then M = 2; When 60° < α ≤ 90°, if γ ≤ 20°, then M = 2; if γ > 20° and θ > 60°, then M = 1; if γ > 20° and 30° < θ ≤ 60°, then M = 1; if γ > 20° and θ ≤ 30°, then M = 3.

9. According to the evaluation method described in claim 1, characterized in that The large deformation levels include four levels: 0, I, II, III, and IV, and the large deformation level v 2 is determined by the following calculation model: When M = 1, When M = 2, When M = 3, v 2 = IV.

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