Water inflow prediction method for underground powerhouse of pumped storage power station

Abstract

The invention relates to the field of hydropower engineering, and provides a water inflow prediction method for an underground powerhouse of a pumped storage power station in order to ensure the accuracy of a prediction result while realizing the usability of the prediction method. And a final water inflow prediction range is obtained according to the calculated three water inflow. The provided three water inflow calculation modes are easy to realize, and the calculation results of the three modes are integrated to obtain the final water inflow range, so that the accuracy of the prediction result is improved.

Description

Technical Field

[0001] The present invention relates to the field of hydropower engineering, and specifically to a method for predicting the water inflow of an underground powerhouse of a pumped-storage power station. Background Technique

[0002] The underground powerhouse of a pumped-storage power station can be divided into a head type, a middle type and a tail type. Among them, the underground powerhouse of the head type and the middle type has a large buried depth, a high groundwater head, and the problem of water inflow in the powerhouse is prominent. The water inflow directly determines the anti-drainage measures of the underground powerhouse system, and the anti-drainage measures are not only related to construction safety, but also related to the permanent safety of project operation. Generally, the buried depth and groundwater head of the underground powerhouse of hydropower projects are generally low, and the problem of water inflow in the cavern is not prominent. Usually, the engineering analogy method is adopted to obtain the predicted result of water inflow; when the buried depth of the underground powerhouse is large and the groundwater head is high, three-dimensional numerical simulation of water inflow can be adopted, but the technical difficulty of three-dimensional seepage numerical simulation is high, the time period is long, and the cost is high. In actual projects, a water inflow prediction method with relatively reliable results and easy use is needed to meet the needs of the survey and design of pumped-storage power stations. Summary of the Invention

[0003] In order to ensure the accuracy of the prediction result while realizing the ease of use of the prediction method, the present application provides a method for predicting the water inflow of an underground powerhouse of a pumped-storage power station.

[0004] The technical solution adopted by the present invention to solve the above problems is as follows:

[0005] A method for predicting the water inflow of an underground powerhouse of a pumped-storage power station, comprising:

[0006] Step 1: Arrange vertical holes in the exploration adit of the underground powerhouse, and conduct a water pressure test in the holes to measure the injection flow of the rock mass in the test section;

[0007] Step 2: Calculate the permeability of each test section;

[0008] Step 3: Divide each test section into group B and group C according to the permeability sectional value A, where the permeability of group B is less than A, the permeability of group C is greater than or equal to A, and the ratio of the test sections in group B to the total test sections is β 1 , and the ratio of the test sections in group C to the total test sections is β 2 ;

[0009] Step 4: Calculate the weighted permeability q", q imax is the maximum value of the permeability in group B, is the average value of the permeabilities of all test sections in group C;

[0010] Step 5: Calculate the rock mass permeability coefficients K corresponding to group B, group C and the weighted permeability q" respectively, L is the length of the tunnel passing through the water-bearing body, ro is the radius of the borehole,

[0011] When calculating the rock mass permeability coefficient K corresponding to Group B, Qi and Hi are the imax corresponding press-in flow rate and test water head;

[0012] When calculating the rock mass permeability coefficient K corresponding to Group C, Qi and Hi are the corresponding press-in flow rate and test water head;

[0013] When calculating the rock mass permeability coefficient K corresponding to the weighted water permeability q'', Qi and Hi are the press-in flow rate and test water head corresponding to q'';

[0014] Step 6: Calculate the water inflow Q corresponding to Group B, Group C and the weighted water permeability q'' respectively according to the rock mass permeability coefficient K 01 、Q 02 and Q b ;

[0015] Step 7: Calculate Q a ,Q a =Q 01 β 1 +Q 02 β 2 ;

[0016] Step 8: Calculate Q c Set a water measuring weir at the entrance of the exploration adit of the powerhouse, measure the total water volume Q 03 at the entrance of the adit, count the total area A1 of the seepage adit wall in the adit, calculate the total area A2 of the adit wall free surface after the excavation of the underground powerhouse, then Q c =Q 03 ×A2 / A1;

[0017] Step 9: The minimum value Q min of the water inflow of the underground powerhouse of the pumped storage power station is a =Min(Q b ,Q c ), the maximum value Q max of the water inflow is a =Max(Q b ,Q c ).

[0018] Furthermore, the layout steps of the vertical holes are as follows:

[0019] Step 11: According to the topographic conditions, arrange the main exploration adit above the elevation of the crown arch of the underground powerhouse to determine the location of the powerhouse;

[0020] Step 12: Arrange the axis of the powerhouse according to the stratigraphic lithology and geological structure revealed by the main exploration adit;

[0021] Step 13: Arrange exploration adits along the axis of the powerhouse in the main exploration adit;

[0022] Step 14: Arrange 3 - 5 vertical holes in the exploration adit.

[0023] Furthermore, the depth of the vertical holes is required to extend 10 - 30 m below the elevation of the powerhouse floor.

[0024] Furthermore, the water pressure test is carried out according to 3 levels of pressure: P1, P2, and P3, and in 5 stages: P1 - P2 - P3 - P2 - P1.

[0025] Furthermore, the water pressure test is carried out every 5 m in the vertical holes.

[0026] Furthermore, the sectional value A of the permeability rate is taken as 10 Lu.

[0027] Furthermore, the water inflow Q is calculated according to the rock mass permeability coefficient K o in the following way: M is the distance from the static water level to the center of the equivalent circle of the cross - section, and d is the diameter of the equivalent circle of the adit cross - section.

[0028] Furthermore, step 9 also includes: rounding the minimum and maximum values of the water inflow.

[0029] The beneficial effects of the present invention compared with the prior art are as follows: This application uses three different methods for calculating the water inflow to calculate a water inflow value from different perspectives respectively, and then obtains the final predicted range of the water inflow based on the three calculated water inflows; the three methods for calculating the water inflow provided in this application are all easy to implement, and the final water inflow range is obtained by integrating the calculation results of the three methods, improving the accuracy of the prediction results. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of the method for predicting the water inflow of the underground powerhouse of a pumped - storage power station. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] As Figure 1 shown, the method for predicting the water inflow of the underground powerhouse of a pumped - storage power station includes:

[0033] Step 1: Arrange vertical holes in the exploration adit of the underground powerhouse, and conduct a water pressure test in the holes to measure the injection flow rate of the rock mass in the test section;

[0034] Step 2: Calculate the permeability rate of each test section;

[0035] Step 3: Divide each test section into Group B and Group C according to the water permeability rate sectional value A, where the water permeability rate of Group B is less than A, and the water permeability rate of Group C is greater than or equal to A. The ratio of the test sections in Group B to the total test sections is β 1 , and the ratio of the test sections in Group C to the total test sections is β 2 ;

[0036] Step 4: Calculate the weighted water permeability rate q”, q imax is the maximum value of the water permeability rate in Group B, is the average value of the water permeability rates of all test sections in Group C;

[0037] Step 5: Calculate the rock mass infiltration coefficients K corresponding to Group B, Group C, and the weighted water permeability rate q” respectively, L is the length of the tunnel passing through the water-bearing body, ro is the borehole radius,

[0038] When calculating the rock mass infiltration coefficient K corresponding to Group B, Qi and Hi are the injection flow rate and test water head corresponding to q imax ;

[0039] When calculating the rock mass infiltration coefficient K corresponding to Group C, Qi and Hi are the injection flow rate and test water head corresponding to;

[0040] When calculating the rock mass infiltration coefficient K corresponding to the weighted water permeability rate q”, Qi and Hi are the injection flow rate and test water head corresponding to q”;

[0041] Step 6: Calculate the water inflow Q corresponding to Group B, Group C, and the weighted water permeability rate q” respectively according to the rock mass infiltration coefficient K 01 , Q 02 and Q b ; The calculation method is: Q o is the water inflow, M is the distance from the static water level to the center of the equivalent circle of the cross-section, and d is the diameter of the equivalent circle of the tunnel body cross-section;

[0042] Step 7: Calculate Q a , Q a = Q 01 β 1 + Q 02 β 2 ;

[0043] Step 8: Calculate Q c , set a water measuring weir at the entrance of the exploration adit of the power house, measure the total water volume Q 03 at the entrance of the adit, count the total area A1 of the seepage tunnel wall in the adit, calculate the total area A2 of the tunnel wall free surface after the excavation of the underground power house, then Q c = Q 03 × A2 / A1;

[0044] Step 9, minimum water inflow Q of the underground powerhouse of the pumped-storage power station min = Min(Q a , Q b , Q c ), maximum water inflow Q max = Max(Q a , Q b , Q c ).

[0045] The seepage characteristics of rock masses are very complex, and it is difficult for the existing various groundwater inflow prediction results to be completely consistent with the actual situation. In this application, the permeability is calculated by grouping, the water inflow is calculated according to the permeability respectively, and then the weighted water inflow is calculated; the water inflow is directly calculated according to the weighted permeability; the water inflow is calculated through the total water volume, the total area of the seepage tunnel wall and the total area of the free space of the tunnel wall; the water inflow is calculated by three different calculation methods, and then the water inflow interval value is provided according to the calculation results of the three methods, so as to make the engineering design as safe and reliable as possible and economically reasonable. When grouping and calculating the permeability, after comprehensively considering the complexity of groundwater calculation, engineering safety and the accuracy of calculation results, Group B is considered under the most unfavorable conditions, and Group C is considered according to the average value.

[0046] Taking a pumped-storage power station located in the northeastern section of the Longmenshan tectonic belt as an example, the project mainly consists of an upper reservoir (dam), a lower reservoir (dam), a water conveyance system, an underground powerhouse and a switchyard, etc. The installed capacity of the power station is 1200 MW, and the project scale is of the first-class large (1) type. The normal storage level of the upper reservoir is 1364.00 m, the total storage capacity is 7.26 million m3, the drawdown depth is 33 m, and the maximum dam height is 84.6 m. The normal storage level of the lower reservoir is 852.00 m, the total storage capacity is 9.63 million m3, and the maximum dam height is 99 m. The underground powerhouse is about 170 m long, about 56 m high, with an excavation span of 27.6 m, and the groundwater head is 288 m.

[0047] The steps for predicting the water inflow of the underground powerhouse according to the method of the present invention are as follows:

[0048] 1. A total of 4 boreholes are arranged in the exploration adit of the underground powerhouse, and each borehole extends 10 - 30 m below the elevation of the powerhouse floor. In this embodiment, the depth is about 200 m. The water pressure test is carried out every 5 m in the borehole, and the water pressure test is carried out in 5 stages P1, P2, P3, P2, P1 according to 3 levels of pressure P1, P2, P3; a total of 182 sections of rock mass water pressure tests are completed. According to multiple experiments, when the sectional value A of the permeability is taken as 10 Lu, the accuracy of the subsequent calculation results is higher. Therefore, the sectional value A of the permeability in this embodiment is taken as 10 Lu. Among all the test sections, there are 149 test sections with a permeability less than 10 Lu, accounting for about 82%, and 33 test sections with a permeability greater than or equal to 10 Lu, accounting for about 18%.

[0049] 2. In the test section with a permeability less than 10 Lu, the maximum permeability is 9.31 Lu, corresponding to a test water head H = 100 m and a pressure injection flow rate Q = 47.9 L / min. The calculated rock mass permeability coefficient K = 0.062 m / d, and the water inflow of the powerhouse Q 01 is 10582.97 m 3 / d.

[0050] In the test section with a permeability greater than or equal to 10 Lu, the average permeability is q = 26.88 Lu, corresponding to an average test water head H = 68.4 m and a pressure injection flow rate Q = 70.08 L / min. The calculated rock mass permeability coefficient K = 0.132 m / d, and the water inflow of the powerhouse Q 02 is 22636.55 m 3 / d.

[0051] The total water inflow of the powerhouse is weighted and averaged according to the proportions of permeabilities less than 10 Lu and greater than or equal to 10 Lu to obtain Q a = 12752.6 m 3 / d.

[0052] 3. When weighted averaging with a permeability less than 10 Lu based on the maximum permeability of 9.31 Lu and a permeability greater than or equal to 10 Lu based on the average value of 26.88 Lu, the weighted average permeability is 12.5 Lu. According to the pressure injection flow rate and test water head corresponding to the weighted average value, the calculated water inflow is Q b = 14736.63 m 3 / d.

[0053] 4. The measured water volume Q 03 at the exploration adit entrance is 1050 m 3 / d, and the area of the main seepage section of the adit wall A1 = 3688 m 3 . The area of the underground powerhouse wall A2 = 29410 m 3 , then the seepage water volume of the underground powerhouse is approximately Q c = 1050×29410 / 3688 = 8373.20 m 3 / d.

[0054] 5. The minimum water inflow of the underground powerhouse Q min = 8373.20 m 3 / d, and the maximum value Q max = 14736.63 m 3 / d. After considering rounding the calculation results, the minimum water inflow Q min = 8400 m 3 / d, and the maximum value Q max = 15000 m 3 / d.

Claims

1. A method for predicting water inflow in underground powerhouse of a pumped storage power station, characterized in that: include: Step 1: Arrange vertical holes in the underground powerhouse exploration tunnel, and conduct water pressure test in the holes to measure the pressure flow rate of the rock mass in the test section; Step 2, calculating the water permeability of each test section; Step 3, according to the water permeability segmentation value A, each test section is divided into group B and group C, wherein the water permeability of group B is less than that of A, and the water permeability of group C is greater than or equal to A, the ratio of the test section in group B to the total test section is β1, and the ratio of the test section in group C to the total test section is β2; Step 4: Calculate the weighted permeability q", q imax is the maximum water permeability in group B, is the average water permeability of all test sections in group C; Step 5: Calculate the rock mass permeability K corresponding to group B, group C and weighted permeability q” respectively. L is the length of the tunnel through the water body, ro is the radius of the borehole, When calculating the rock mass permeability coefficient K corresponding to group B, Qi and Hi are q imax Corresponding inlet flow and test water head; When calculating the rock mass permeability coefficient K corresponding to group C, Qi and Hi are Corresponding inlet flow and test water head; When calculating the rock mass permeability coefficient K corresponding to the weighted permeability q”, Qi and Hi are the inflow flow and test head corresponding to q”; Step 6: Calculate the water inflow Q corresponding to group B, group C and weighted permeability q” according to the rock mass permeability coefficient K 01 , Q 02 and Q b ; Step 7. Calculate Q a , Q a =Q 01 β1+Q 02 β2; Step 8. Calculate Q c , set up a water measuring weir at the entrance of the plant exploration flat tunnel to measure the total water volume Q at the entrance of the flat tunnel 03 , calculate the total area of ​​seepage wall in the flat tunnel A1, calculate the total area of ​​the wall exposed to air after the underground powerhouse is excavated A2, then Q c =Q 03 ×A2 / A1; Step 9: Minimum water inflow value Q of underground powerhouse of pumped storage power station min =Min(Q a , Q b , Q c ), maximum water inflow Q max =Max(Q a , Q b , Q c ).

2. The method for predicting water inflow in underground powerhouse of a pumped storage power station according to claim 1, characterized in that: The steps for arranging vertical holes are: Step 11: According to the terrain conditions, arrange the main exploration tunnel above the elevation of the underground powerhouse top arch to determine the location of the powerhouse; Step 12: Arrange the plant axis according to the stratum lithology and geological structure revealed by the main exploration adit; Step 13: Arrange exploration flat tunnels in the main exploration flat tunnel along the axis of the powerhouse; Step 14: Arrange 3 to 5 vertical holes in the exploration flat tunnel.

3. The method for predicting water inflow in underground powerhouse of a pumped storage power station according to claim 2, characterized in that: The vertical hole depth is required to be 10 to 30 meters above the factory floor elevation.

4. The method for predicting water inflow in underground powerhouse of a pumped storage power station according to claim 2, characterized in that: The water pressure test is carried out at three levels of pressure: P1, P2 and P3, and in five stages: P1-P2-P3-P2-P1.

5. The method for predicting water inflow in underground powerhouse of a pumped storage power station according to claim 4, characterized in that: Carry out water pressure test every 5m in the vertical hole.

6. The method for predicting water inflow in underground powerhouse of a pumped storage power station according to claim 1, characterized in that: The permeability segment value A is 10Lu.

7. The method for predicting water inflow in underground powerhouse of a pumped storage power station according to any one of claims 1 to 6, characterized in that: Calculate the water inflow Q based on the rock mass permeability coefficient K o The method is: M is the distance from the static water level to the center of the cross-section equivalent circle, and d is the diameter of the cross-section equivalent circle of the tunnel body.

8. The method for predicting water inflow in underground powerhouse of a pumped storage power station according to claim 7, characterized in that: Step 9 also includes: rounding the minimum and maximum values ​​of the water inflow.

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