A method for calculating shaft wall water pressure based on seepage volume

Abstract

The present invention discloses a method for calculating the water pressure of a vertical shaft wall based on seepage volume, which is applicable to the design of a vertical shaft in a coal mine. The water pressure of the vertical shaft wall is estimated based on the concept of seepage volume commonly used in engineering. First, the vertical shaft parameters are preset according to the formation parameters. Then, the shaft-surrounding rock Darcy seepage model is established according to the parameters of the designed vertical shaft. Based on the shaft seepage volume, three water pressure reduction coefficients are calculated: the concrete material foundation reduction coefficient, the shaft wall damage reduction coefficient, and the wall rear surrounding rock grouting reduction coefficient. The water pressure of the vertical shaft wall is the product of the original formation water pressure and the three water pressure reduction coefficients. This method fills the gap in the current shaft wall water pressure design method that has no effective theoretical support. The parameters in the method are derived from engineering practice, the physical meaning is clear, the calculation process is simple, and it is convenient for engineering application.

Description

Technical Field

[0001] The invention relates to a method for calculating the water pressure of a shaft wall, and is particularly suitable for a method for calculating the water pressure of a shaft wall based on seepage volume and used in the design of a coal mine shaft. Background Art

[0002] The vertical shaft is an important transportation channel for coal mine production, and its design should reflect the principles of safety, reliability, advanced technology, and economic rationality. Among them, the design of shaft wall water load is the key and difficult point in shaft design. With the development of mineral resources in western my country, the shafts of coal mines are getting deeper and deeper, and the current calculation method of shaft wall water load is difficult to meet the needs of industry development. Due to the lack of relevant calculation theory of shaft wall water load, in order to ensure the so-called shaft safety, the design will fearlessly increase the design thickness of the shaft wall, thereby increasing the construction cost, construction difficulty and safety hazards of the vertical shaft. The core problem is that the value of the shaft wall water load is unclear.

[0003] The current "Design Code for Coal Mine Shafts and Chambers" (GB50384-2016) only provides the calculation range of the shaft wall water load. The specific description is: the standard value of the shaft wall water load P = 0.01kH, where H is the shaft wall design calculation depth, and k is the water load reduction factor, which is generally 0.81 to 1. It can be seen that the water load reduction factor β specified in the specification has a large range of variation and is difficult to be used directly in the design. In addition, most shaft wall water load test results show that the β value is actually much lower than 0.81. However, there is no theoretical model to reflect the evolution mechanism and design value principle of the water load reduction factor β.

[0004] In summary, it is urgent to propose a theoretical method that can accurately calculate the water load on the wellbore to facilitate engineering applications and provide a theoretical basis for wellbore design in deep earth engineering development. Summary of the invention

[0005] In view of the shortcomings of the existing technology, a method for calculating the water pressure on the shaft wall based on seepage volume is provided, which takes into account the reduction effect of the wellbore seepage water inflow on the water load. The calculation of the shaft wall water pressure is more reasonable and can provide a favorable theoretical basis for the optimization design of deep vertical shafts. The method for calculating the water pressure on the shaft wall based on seepage volume is used to solve the problem that the existing method cannot quantitatively calculate the water load reduction number.

[0006] To achieve the purpose of the above-mentioned technology, a method for calculating the water pressure of a vertical shaft wall based on seepage volume of the present invention first designs a vertical shaft according to the data of the strata in the construction area, and establishes a shaft-surrounding rock Darcy seepage model according to the parameters of the designed shaft, wherein the shaft seepage volume is measured by a water collecting device at the bottom of the shaft, and the water flow information outside the shaft is obtained through survey and design data. The shaft seepage volume based on the shaft-surrounding rock Darcy seepage model is used to calculate the concrete material foundation reduction coefficient when the shaft wall is intact, the shaft wall damage reduction coefficient and the surrounding rock grouting reduction coefficient behind the wall, respectively, and then the shaft wall water pressure is obtained by multiplying the original formation water pressure by the three water pressure reduction coefficients.

[0007] The specific steps are as follows:

[0008] a. Collect basic parameters of the strata in the vertical shaft construction area, including the surrounding rock permeability coefficient k w , surrounding rock grouting permeability reduction coefficient ξ, hydraulic radius R; propose preliminary parameters for well wall design, which include: concrete permeability coefficient k c0 and intensity f s , the design value of the inner diameter of the well wall is a, the design value of the outer diameter of the well wall is b, the design depth of the wellbore is H, and the allowable flow rate of the wellbore is Q;

[0009] b. Based on Darcy's seepage principle, a shaft-surrounding rock seepage field model of the vertical shaft is established, and the water pressure foundation reduction coefficient β1 when the concrete material seeps when the shaft wall is intact is calculated;

[0010] c. When simulating shaft damage, the permeability coefficient of the concrete shaft wall structure increases after damage, and the shaft seepage volume increases. The shaft allowable flow Q is used to reversely calculate the equivalent permeability coefficient k of the shaft wall concrete. c , establish the damaged shaft-surrounding rock seepage field model, and calculate the wellbore water pressure reduction coefficient β2 when the shaft wall is damaged based on Darcy's seepage principle;

[0011] d. When the wall is used to simulate the surrounding rock grouting method to improve the seepage of the wellbore, the grouting increases the surrounding rock permeability coefficient; a damaged wellbore-grouting surrounding rock permeability field model is established, and based on the Darcy seepage principle, the water pressure reduction coefficient β3 of the vertical shaft wall after confining pressure grouting is calculated;

[0012] e. Calculate the water pressure P at the maximum design depth of the wellbore based on the water pressure reduction coefficient β1 when the wellbore is intact, the water pressure reduction coefficient β2 when the wellbore is damaged, and the water pressure reduction coefficient β3 of the wellbore after confining pressure grouting. w ;

[0013] f. According to the water pressure P at the maximum design depth of the wellbore w Reverse the minimum value of the outer diameter of the wellbore b min and compared with the design value b of the wellbore outer diameter;

[0014] g. Such as the design value of the wellbore outer diameter b and the minimum value of the wellbore outer diameter b min Satisfy 0≤bb min ≤Tol, then the corresponding water pressure P w is the calculated value of the water pressure on the shaft wall based on the seepage rate, where Tol represents the optimization error; if the condition is not met, the design value b of the shaft wall outer diameter is re-optimized, when bb min When <0, increase b; bb min When >Tol, reduce b by 0.1m each time and redesign until the optimized wellbore outer diameter design value b' that meets the conditions is obtained.

[0015] Further, in step b, when the well wall is intact and the concrete material seepage occurs, the water pressure basic reduction coefficient β1 is:

[0016]

[0017] Further, in step c, the equivalent permeability coefficient k of the wellbore is c for:

[0018]

[0019] Using the equivalent permeability coefficient k of the wellbore c Calculate the water pressure reduction factor β2 related to wellbore rupture:

[0020]

[0021] Further, in step d, the surrounding rock grouting permeability coefficient k g for:

[0022] k g =ξk w (11)

[0023] Using the surrounding rock grouting permeability coefficient k g Calculate the water pressure reduction factor β3 related to surrounding rock grouting:

[0024]

[0025] Further, in step e, the water pressure P at the maximum design depth of the wellbore w The calculation method is:

[0026] P w =0.01·β1·β2·β3·H (13)

[0027] Furthermore, according to the water pressure P at the maximum design depth of the wellbore w Reverse the minimum value of the outer diameter of the wellbore b min The process is:

[0028]

[0029] Beneficial effects:

[0030] Based on the Darcy seepage model, this method introduces the reduction coefficient of the shaft wall concrete material foundation, considers the reduction coefficient of the shaft wall rupture and the reduction coefficient of the surrounding rock grouting behind the wall, and establishes a calculation formula for the shaft wall water pressure based on the seepage volume. This calculation method is an analytical method with simple parameters, clear physical meaning, no need for additional parameters, consistent with the actual situation, and easy for engineering application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic plan view of the surrounding rock of the well wall at the depth of the well designed in the present invention;

[0032] Figure 2 It is a schematic diagram of the seepage profile within the depth range of the well wall in the present invention;

[0033] Figure 3 The figure is a schematic diagram of a water pressure calculation process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings.

[0035] like Figure 1-3 As shown, a method for calculating the water pressure of a vertical shaft wall based on seepage volume includes the following steps:

[0036] 1. Collect the basic parameters of the wellbore design formation, including the surrounding rock permeability coefficient k w , surrounding rock grouting permeability reduction coefficient ξ, hydraulic radius R; proposed shaft wall design parameters, including concrete permeability coefficient k c0 and intensity f s , wellbore inner diameter a, wellbore outer diameter b, design depth H, wellbore allowable flow rate Q;

[0037] 2. Based on Darcy's seepage principle, the wellbore-surrounding rock seepage field is established, and the concrete material foundation reduction coefficient β1 is calculated when the wellbore is intact;

[0038] 3. When the wellbore is damaged, the concrete wellbore structure is damaged, its permeability coefficient increases, and the wellbore seepage volume increases. Use the wellbore allowable flow Q to reversely calculate the "equivalent permeability coefficient" of the wellbore concrete; establish a damaged wellbore-surrounding rock seepage field model, and calculate the wellbore water pressure reduction coefficient β2 when the wellbore is damaged based on the Darcy seepage principle;

[0039] 4. When the back-wall surrounding rock grouting method is used to improve the wellbore seepage, the grouting increases the surrounding rock permeability coefficient. A damaged wellbore-grouting surrounding rock permeability field model is established, and based on the Darcy seepage principle, the wellbore water pressure reduction coefficient β3 is calculated during confining pressure grouting;

[0040] 5. Based on the three reduction factors, estimate the water pressure P at the maximum design depth of the wellbore w ;

[0041] 6. Calculate the outer diameter of the wellbore b based on the estimated water pressure min and compared with the preliminary design value b;

[0042] 7. Such as b and b min If certain conditions are met, the calculation is terminated; if not, the outer diameter b of the wellbore is re-optimized and redesigned until the conditions are met. min The corresponding water pressure P when certain conditions are met w , which is the calculated value of the vertical shaft wall water pressure based on the seepage volume proposed by the present invention. Specific embodiment 1:

[0044] like Figure 1-2 As shown in the figure, the shaft wall design of a certain deep bedrock shaft in the west cannot accurately determine the shaft wall water load, so it is impossible to accurately judge whether the shaft wall design is reasonable. Therefore, the calculation method proposed in this invention is used to optimize the design based on water load, and the specific steps are as follows:

[0045] 1. Formation parameter k w =0.05m / h, surrounding rock grouting permeability reduction coefficient ξ = 0.4, hydraulic radius R = 500m; the proposed preliminary design parameters of the wellbore, including k c0 =1.0×10 -5 m / h and strength f s =35MPa, inner diameter of the well wall a = 5.5m, outer diameter b = 6.0m, design depth H = 640m, allowable flow rate of the wellbore Q = 5m 3 ;

[0046] 2. Establishment Figure 1 The wellbore-surrounding rock seepage model shown in the figure is combined with hydraulic boundary conditions and based on the concrete permeability coefficient, the wellbore water pressure foundation reduction coefficient β1 is calculated.

[0047]

[0048] 3. Considering the increase in the seepage of the concrete wellbore when the wellbore is damaged. Use the wellbore allowable flow Q to inversely calculate the "equivalent permeability coefficient" of the wellbore concrete; establish a damaged wellbore-surrounding rock seepage field model, and calculate the wellbore water pressure reduction coefficient β2 when the wellbore is damaged based on the Darcy seepage principle.

[0049]

[0050]

[0051] 4. Grouting increases the surrounding rock permeability coefficient, establishes a damaged wellbore-grouting surrounding rock permeability field model, and calculates the surrounding rock grouting permeability coefficient k when considering the surrounding rock grouting behind the wall based on the Darcy seepage principle. g Wellbore water pressure reduction factor β3;

[0052] k g =ξk w =0.02m / h (18)

[0053]

[0054] 5. Calculate the well wall water load P w

[0055] P w =0.01·β1·β2·β3·H=4.31MPa (20) 6.

[0057]

[0058] 7. Comparison with the initial design parameters of the wellbore b, b min , the preliminary design does not meet the requirements, the optimization and initial design parameters of the wellbore are compared b,

[0059] 8. Repeat steps 1-6. When the optimized wellbore outer diameter design value b' = 6.4m, β1 = 0.99, k c =2.1×10 -4 m / h, β2=0.89, k g =0.02m / h, β3=0.77, P w =4.35MPa, b min =6.35m. When the judgment criterion Tol = 0.1m, the design has met the water pressure requirements. Therefore, based on the allowable flow rate of the wellbore Q = 5m 3 / h, the water pressure on the shaft wall P w =4.35MPa.​

Claims

1. A method for calculating the water pressure of a vertical shaft wall based on seepage, characterized in that: Firstly, the vertical shaft is designed according to the data of the formation in the construction area, and the shaft-surrounding rock Darcy seepage model is established according to the parameters of the designed shaft, in which the shaft seepage is measured by the water collection equipment at the bottom of the shaft, and the water flow information outside the shaft is obtained through the survey and design data; the shaft seepage based on the shaft-surrounding rock Darcy seepage model is used to calculate the concrete material foundation reduction coefficient when the shaft wall is intact, the shaft wall damage reduction coefficient and the surrounding rock grouting reduction coefficient behind the wall, and then the shaft wall water pressure is obtained by multiplying the original formation water pressure and the three water pressure reduction coefficients; The specific steps are as follows: a. Collect basic parameters of the strata in the vertical shaft construction area, including the surrounding rock permeability coefficient k w , surrounding rock grouting permeability reduction coefficient ξ, hydraulic radius R; Propose preliminary parameters for shaft wall design. Including: Concrete permeability coefficient k c0 and intensity f s , the design value of the inner diameter of the well wall is a, the design value of the outer diameter of the well wall is b, the design depth of the wellbore is H, and the allowable flow rate of the wellbore is Q; b. Based on Darcy's seepage principle, a shaft-surrounding rock seepage field model of the vertical shaft is established, and the water pressure foundation reduction coefficient β1 when the concrete material seeps when the shaft wall is intact is calculated; c. When simulating shaft damage, the permeability coefficient of the concrete shaft wall structure increases after damage, and the shaft seepage volume increases. The shaft allowable flow Q is used to reversely calculate the equivalent permeability coefficient k of the shaft wall concrete. c , establish the damaged shaft-surrounding rock seepage field model, and calculate the wellbore water pressure reduction coefficient β2 when the shaft wall is damaged based on Darcy's seepage principle; d. When the wall is used to simulate the surrounding rock grouting method to improve the seepage of the wellbore, the grouting increases the surrounding rock permeability coefficient; a damaged wellbore-grouting surrounding rock permeability field model is established, and based on the Darcy seepage principle, the water pressure reduction coefficient β3 of the vertical shaft wall after confining pressure grouting is calculated; e. Calculate the water pressure P at the maximum design depth of the wellbore based on the water pressure reduction coefficient β1 when the wellbore is intact, the water pressure reduction coefficient β2 when the wellbore is damaged, and the water pressure reduction coefficient β3 of the wellbore after confining pressure grouting. w ; f. According to the water pressure P at the maximum design depth of the wellbore w Reverse the minimum value of the outer diameter of the wellbore b min and compared with the design value b of the wellbore outer diameter; g. Such as the design value of the wellbore outer diameter b and the minimum value of the wellbore outer diameter b min Satisfy 0≤bb min ≤Tol, then the corresponding water pressure P w is the calculated value of the water pressure on the shaft wall based on the seepage rate, where Tol represents the optimization error; if the condition is not met, the design value b of the shaft wall outer diameter is re-optimized, when bb min <0, increase b; bb min >Tol, reduce b by 0.1m each time and redesign until the optimized wellbore outer diameter design value b' that meets the conditions is obtained.

2. A method for calculating shaft wall water pressure based on seepage volume according to claim 1, characterized in that: In step b, when the well wall is intact and the concrete material seepage occurs, the water pressure foundation reduction coefficient β1 is:

3. The method for calculating the water pressure of a vertical shaft wall based on seepage volume according to claim 1 is characterized in that: In step c, the equivalent permeability coefficient of the wellbore k c for: Using the equivalent permeability coefficient k of the wellbore c Calculate the water pressure reduction factor β2 related to wellbore rupture:

4. A method for calculating shaft wall water pressure based on seepage volume according to claim 1, characterized in that: In step d, the surrounding rock grouting permeability coefficient k g for: k g =ξk w (4) Using the surrounding rock grouting permeability coefficient k g Calculate the water pressure reduction factor β3 related to surrounding rock grouting:

5. The method for calculating the water pressure of a vertical shaft wall based on seepage volume according to claim 1 is characterized in that: The water pressure P at the maximum design depth of the wellbore in step e w The calculation method is: P w = 0.01·β1·β2·β3·H (6).

6. A method for calculating shaft wall water pressure based on seepage volume according to claim 1, characterized in that According to the water pressure P at the maximum design depth of the wellbore w Reverse the minimum value of the outer diameter of the wellbore b min The process is:

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