A quantitative design method for the spacing between caverns in a large underground cavern group

Abstract

The present invention relates to the field of underground cavern design, and in particular to a quantitative design method for the spacing arrangement of caverns in a large underground cavern group. Three key parameters are selected: the buried depth of the underground cavern group, the geostress lateral pressure coefficient, and the cavern spacing ratio; the function expression between the displacement value of the key part and the key parameter is obtained by calculation to characterize the relationship between the key parameters of the large underground cavern group and the displacement value of the key part, and then for a specific large underground cavern group project, the buried depth of the underground cavern group and the geostress lateral pressure coefficient are determined values, and the relationship function between the displacement value of the key part and the cavern spacing ratio can be obtained. By drawing a curve graph and taking two groups of characteristic points at both ends of the curve that change approximately linearly, line segments are drawn through the characteristic points at both ends to obtain the intersection of the line segments, and the value corresponding to the intersection is the cavern arrangement spacing ratio of the large underground cavern group. The present invention has the characteristics of being scientific, complete, with clear indicators, and easy to implement, and can improve the overall stability of the underground cavern group.

Description

Technical Field

[0001] The invention relates to the field of underground cavern design, and in particular to a quantitative design method for cavern spacing arrangement of a large underground cavern group. Background Art

[0002] The selection of the spacing between large underground caverns should first consider the requirements of electromechanical layout and hydraulic operation, tailwater regulation guarantee calculation, etc., and then be preliminarily determined based on specific geological conditions and engineering experience. When adjusting the spacing between caverns, in order to ensure the overall stability of the cavern group, sufficient intact rock thickness should be retained between the caverns; on the premise of ensuring the stability of the rock mass between the caverns, the principle is to facilitate the operation of the unit, shorten the length of the busbar, reduce the amount of engineering, and minimize the spacing between the three caverns.

[0003] According to statistics, the distance between adjacent main caverns of underground powerhouses of large hydropower stations built at home and abroad is mostly 35m to 60m, which is about 0.5 to 0.8 times the height of the large cavern; the distance is about 0.8 to 2.5 times the average excavation span of adjacent caverns. A large distance between the main caverns of underground powerhouses is beneficial to the stability of the cavern surrounding rock and can reduce the risk of connection of the plastic zone of the rock column between the main caverns, but it will increase the project investment and long-term power loss accordingly. At present, relevant regulations and engineering experience usually determine the distance between adjacent main caverns based on geological conditions, using the engineering analogy method and combining the statistical values ​​of existing projects.

[0004] It can be seen that the traditional design methods for the design of the spacing between underground caverns mostly remain at the level of experience (norms), and have not been able to solve the quantitative design problem of the spacing between caverns. In view of the shortcomings of the traditional design methods, it is necessary to propose a more scientific and convenient quantitative design method for the spacing between caverns in large underground caverns. Summary of the invention

[0005] In order to overcome the above problems, the purpose of the present invention is to provide a quantitative design method for the cavern spacing arrangement of a large underground cavern group. The cavern spacing obtained through scientific quantitative calculation can not only ensure the stability of the underground cavern group, but also reduce project investment and long-term power loss.

[0006] To achieve the above object, the present invention provides a quantitative design method for the spacing arrangement of large underground caverns, which is characterized by comprising the steps of:

[0007] (1) Determine the three key parameters for the quantitative design of cavern spacing arrangement: the underground cavern group burial depth A, the geostress lateral pressure coefficient B, and the cavern spacing ratio C; where:

[0008] C=L / H (1)

[0009] In the formula, C is the ratio of the distance between caverns; L is the distance between caverns; H is the excavation height of the main powerhouse;

[0010] (2) Each key parameter is selected at n levels within its value range, and three factors and n levels of parameters are combined for the three key parameters to obtain m parameter combination methods; the value ranges of the underground cavern group depth A, the ground stress lateral pressure coefficient B, and the cavern spacing ratio C are: A min ≤A≤A max , B min ≤B≤B max , C min ≤C≤C max ;

[0011] (3) Based on the existing three-dimensional numerical model of a common large underground cavern group, the displacement D of the key part of the anchoring area of ​​the underground cavern group corresponding to each parameter combination is calculated by finite element or finite difference method, and the function expression between the displacement D of the key part and the three key parameters is obtained by fitting calculation: D = f(A, B, C);

[0012] (4) Substitute two key parameters of the underground cavern group to be tested: the burial depth A of the underground cavern group and the lateral pressure coefficient B of the ground stress into the function D = f (A, B, C) to obtain the function D = f (C);

[0013] (5) According to the function D = f(C), a curve of the displacement D of the key part and the ratio C of the spacing between the caverns is drawn. The horizontal axis is the ratio C of the spacing between the caverns, and the vertical axis is the displacement D of the key part. The value range of the ratio C of the spacing between the caverns is (C min ,C max ), take two sets of characteristic points (C min ,d Cmin ) and (α,d α ), and (β,d β ) and (C max ,d Cmax ), over (C min ,d Cmin ) and (α,d α ) draw the first line segment through (β,d β ) and (C max ,d Cmax ) is used to make a second line segment. The horizontal coordinate value of the intersection of the first line segment and the second line segment is obtained according to formula (2), which is the ratio C of the cavern spacing of the underground cavern group to be measured. According to formula (1), the cavern spacing L of the underground cavern group to be measured can be obtained.

[0014]

[0015] As a preferred solution, in step (2), an orthogonal experimental design method is used to perform parameter combinations of three factors and n levels on the three key parameters.

[0016] As a preferred solution, in step (2), n=5, and an orthogonal experimental design method is used to perform three-factor five-level parameter combinations on the three key parameters to obtain 25 parameter combinations.

[0017] As a preferred solution, in step (3), the function D=f(A, B, C) of the displacement value D of the key part is obtained by fitting and analyzing the data of the buried depth, lateral pressure coefficient of ground stress, ratio of the spacing between caverns and the displacement value of the key part of m groups of underground caverns using a multivariate linear regression analysis method to obtain a polynomial curve expression.

[0018] As a preferred solution, in step (3), according to formula (4), the buried depth A of the underground cavern group is dimensionless, and the functional expression between the displacement D of the key part and the three key parameters is obtained: D = f(A i ,B,C);

[0019]

[0020] In the formula, A i is the dimensionless burial depth of underground caverns; A is the burial depth of underground caverns.

[0021] As a preferred solution, in step (3), the structure of the existing common large underground cavern group includes a main power building and a main transformer room, the height of the main power building is 45 to 90 meters, and the underground cavern group is arranged in a rock mass dominated by Class III or above surrounding rock.

[0022] As a preferred solution, A min =200m, A max =600m, B min =0.7, B max =2.5, C min =0.5, C max =0.9.

[0023] As a preferred solution, in step (3), the displacement D of the key part of the anchoring area of ​​the underground cavern group is represented by the displacement value of the middle part of the downstream side wall of the main power building.

[0024] The advantages of the present invention are: the three key parameters selected by the present invention can more comprehensively characterize the characteristics of the caverns of a large underground cavern group, and the function expression between the displacement value of the key part and the key parameter can be obtained by calculating the relationship between the key parameters and the displacement value of the key part of the large underground cavern group, and then for a specific large underground cavern group project, the buried depth of the underground cavern group and the ground stress lateral pressure coefficient are determined values, and the relationship function between the displacement value of the key part and the cavern spacing ratio can be obtained, and by drawing a curve graph and taking two groups of characteristic points at both ends of the curve that change approximately linearly, line segments are drawn through the characteristic points at both ends to obtain the intersection of the line segments, and the value corresponding to the intersection is the cavern layout spacing ratio of the large underground cavern group. The design idea of ​​the present invention is clear, the method is scientific and effective, and the cavern layout spacing of the underground cavern group obtained by scientific quantitative calculation is helpful to improve the stability of the underground cavern group. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a quantitative design method for the arrangement of spacing between caverns in a large underground cavern group according to the present invention;

[0026] Figure 2 It is a structural schematic diagram of a large underground cavern group of a certain level of hydropower station in the embodiment;

[0027] Among them, there are 2 main powerhouses, 4 main transformer rooms, and 6 tail control rooms;

[0028] Figure 3 It is a curve chart for calculating the ratio of the spacing between the chambers in the embodiment. DETAILED DESCRIPTION

[0029] In order to better understand the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific examples.

[0030] Example

[0031] The underground powerhouse cavern group of a certain hydropower station is taken as the engineering background. The underground cavern group is a common underground cavern group structure. Figure 2 As shown, the large underground cavern group contains three cavern structures, namely, the main powerhouse 2, the main transformer room 4, and the tail regulating room 6. The three caverns are arranged in parallel, with a vertical burial depth of about 180 to 350 meters. The surrounding rock of the underground powerhouse area is mainly Class III1 marble. The design of the cavern spacing of the underground cavern group in this embodiment is specifically the spacing between the main powerhouse 2 and the main transformer room 4.

[0032] Combination Figure 1 As shown in the figure, the quantitative design of the spacing arrangement of the large underground caverns group includes the following steps:

[0033] (1) Determine the three key parameters for the quantitative design of cavern spacing arrangement: the underground cavern group burial depth A, the geostress lateral pressure coefficient B, and the cavern spacing ratio C; where:

[0034] C=L / H (1)

[0035] In the formula, C is the ratio of the distance between caverns; L is the distance between caverns; H is the excavation height of the main powerhouse;

[0036] (2) The ranges of the buried depth A of the underground cavern group, the lateral pressure coefficient B of the ground stress, and the ratio C of the cavern spacing are: 200m≤A≤600m, 0.7≤B≤2.5, and 0.5≤C≤0.9, respectively; five levels are selected for each parameter within its range, and the orthogonal experimental design method is used to perform three-factor five-level parameter combinations on the three key parameters, obtaining 25 parameter combinations; the selection of factors and level changes is shown in Table 1. One calculation is taken as one experiment, and calculations are performed according to different parameter combinations. Assuming that there is no interaction between the factors, according to the orthogonal table L of the selected three-factor five-level model 25 (5 3 ) to arrange the test, only 25 tests are needed, which is only 5 times the workload of the full test. 3 = one fifth of 125 times, and the amount of calculation is greatly reduced.

[0037] Table 1 Factors and level values

[0038] Level value Buried depth A(m) Ground stress lateral pressure coefficient B The ratio of the distance between the chambers C 1 200 0.7 0.5 2 300 1.0 0.6 3 400 1.5 0.7 4 500 2.0 0.8 5 600 2.5 0.9

[0039] (3) Based on the existing three-dimensional numerical model of common large underground cavern groups, the displacement D of the key part of the anchoring area of ​​the underground cavern group corresponding to each parameter combination is calculated by finite element or finite difference method. A total of 25 groups of underground cavern group burial depth, ground stress lateral pressure coefficient, cavern spacing ratio and key part displacement value data are obtained. In order to make the analysis have a more universal effect and significance, dimensionless analysis is adopted, and the underground cavern group burial depth A is dimensionlessly processed:

[0040]

[0041] In the formula, A i is the dimensionless buried depth of underground caverns; A is the buried depth of underground caverns;

[0042] The multivariate linear regression analysis method was used to analyze the burial depths of 25 groups of dimensionless underground caverns. i The function D of the displacement value D of the key part is obtained by fitting the data of the ground stress lateral pressure coefficient B, the ratio of the distance between the caverns C and the displacement value D of the key part. i ,B,C), the function is a polynomial curve expression.

[0043] Among them, the displacement D of the key part of the anchoring area of ​​the underground cavern group is the displacement value of the middle part of the downstream side wall of the main powerhouse; since the downstream side wall of the underground main powerhouse is the weakest position, the middle part of the downstream side wall, close to the main transformer room, is more obviously affected by the adjacent cavern. A large amount of monitoring data and calculation and analysis results show that the displacement of this part is mostly one of the maximum displacement values ​​around the cavern. Therefore, the displacement value of the middle part of the downstream side wall is taken as the displacement value of the key part of the underground cavern group.

[0044] (4) For Jinping I Hydropower Station, the underground cavern group burial depth A and the geostress lateral pressure coefficient B are fixed values. The burial depth is 260m (dimensionless underground cavern group burial depth A i =1.3), the ground stress lateral pressure coefficient B = 0.8 is substituted into the fitted displacement value function D = f(A i ,B,C), the function is further simplified to D = f(C) = 4.6C 2 -8.010C+18.221.

[0045] (5) Combination Figure 3 As shown in the figure, according to D = f(C), a curve of the displacement value D of the key part and the ratio of the cavern spacing C is drawn, where the horizontal axis is the ratio of the cavern spacing, the vertical axis is the displacement value of the key part, and the value range of the horizontal axis is [0.5, 0.9]. The two sets of characteristic points (0.5, d 0.5 ) and (α,d α ), and (β,d β ) and (0.9,d 0.9 ), over (0.5,d 0.5 ) and (α, d α ) draw the first line segment through (β,d β ) and (0.9,d 0.9 ) to make the second line segment, and C min =0.5 ， C max =0.9 is substituted into formula (2) to obtain formula (3) to obtain the intersection point of the first line segment and the second line segment C=0.68.

[0046]

[0047] The height of the main powerhouse of Jinping I Hydropower Station is H=68.8m, and the spacing between the main powerhouse and the main transformer room of the underground cavern group to be tested is L=C*H=0.68*68.8m=46.8m.

[0048] During the actual construction of Jinping I Hydropower Station, the main cavern spacing was about 45 m, which was 4% consistent with the optimal value obtained by this method, proving the effectiveness of the quantitative design method for cavern spacing arrangement of large underground cavern groups of the present invention.

Claims

1. A quantitative design method for the spacing arrangement of large underground caverns, characterized in that: Includes steps: (1) Determine the three key parameters for the quantitative design of cavern spacing arrangement: the underground cavern group burial depth A, the geostress lateral pressure coefficient B, and the cavern spacing ratio C; where: C=L / H (1) In the formula, C is the ratio of the distance between caverns; L is the distance between caverns; H is the excavation height of the main powerhouse; (2) Each key parameter is selected at n levels within its value range, and three factors and n levels of parameters are combined for the three key parameters to obtain m parameter combination methods; the value ranges of the underground cavern group depth A, the ground stress lateral pressure coefficient B, and the cavern spacing ratio C are: A min ≤A≤A max , B min ≤B≤B max , C min ≤C≤C max ; (3) Based on the existing three-dimensional numerical model of a common large underground cavern group, the displacement D of the key part of the anchoring area of ​​the underground cavern group corresponding to each parameter combination is calculated by finite element or finite difference method, and the function expression between the displacement D of the key part and the three key parameters is obtained by fitting calculation: D = f(A, B, C); (4) Substitute two key parameters of the underground cavern group to be tested: the burial depth A of the underground cavern group and the lateral pressure coefficient B of the ground stress into the function D = f (A, B, C) to obtain the function D = f (C); (5) According to the function D = f(C), a curve of the displacement D of the key part and the ratio C of the spacing between the caverns is drawn. The horizontal axis is the ratio C of the spacing between the caverns, and the vertical axis is the displacement D of the key part. The value range of the ratio C of the spacing between the caverns is (C min , C max ), take two sets of characteristic points (C min ,d Cmin ) and (α,d α ), and (β,d β ) and (C max ,d Cmax ), over (C min ,d Cmin ) and (α,d α ) draw the first line segment through (β,d β ) and (C max ,d Cmax ) is used to make a second line segment. The horizontal coordinate value of the intersection of the first line segment and the second line segment is obtained according to formula (2), which is the ratio C of the cavern spacing of the underground cavern group to be measured. According to formula (1), the cavern spacing L of the underground cavern group to be measured can be obtained.

2. The quantitative design method for the spacing arrangement of large underground caverns according to claim 1 is characterized in that: In the step (2), an orthogonal experimental design method is used to perform parameter combination of three factors and n levels on the three key parameters.

3. The quantitative design method for the spacing arrangement of large underground caverns according to claim 2 is characterized in that: In the step (2), n=5, and an orthogonal experimental design method is used to perform parameter combinations of three factors and five levels on the three key parameters to obtain 25 parameter combinations.

4. The quantitative design method for the spacing arrangement of large underground caverns according to claim 1 is characterized in that: In the step (3), the function D=f(A, B, C) of the displacement D of the key part is obtained by fitting and analyzing the data of the buried depth, lateral pressure coefficient of ground stress, ratio of the distance between the caverns and the displacement value of the key part of the m groups of underground caverns using a multivariate linear regression analysis method to obtain a polynomial curve expression.

5. The quantitative design method for the spacing arrangement of large underground caverns according to claim 1 is characterized in that: In step (3), according to formula (4), the buried depth A of the underground cavern group is dimensionless, and the functional expression between the displacement D of the key part and the three key parameters is obtained: D = f(A i ,B,C); In the formula, A i is the dimensionless burial depth of underground caverns; A is the burial depth of underground caverns.

6. The quantitative design method for the spacing arrangement of large underground caverns according to claim 1 is characterized in that: In the step (3), the structure of the existing common large underground cavern group includes a main powerhouse and a main transformer room, the height of the main powerhouse is 45 to 90 meters, and the underground cavern group is arranged in a rock mass dominated by Class III or above surrounding rock.

7. The quantitative design method for the spacing arrangement of large underground caverns according to claim 1 is characterized in that: A min =200m,A max =600m,B min =0.7,B max =2.5,C min =0.5,C max =0.9。 8. The method for quantitative design of the spacing between caverns in a large underground cavern group according to claim 1 is characterized in that: In the step (3), the displacement D of the key part of the anchoring area of ​​the underground cavern group is characterized by the displacement value of the middle part of the downstream side wall of the main power building.

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