A method for determining water pressure and total load of vertical shaft wall considering influence of grouting circle

Abstract

This invention discloses a method for determining the water pressure and total load of a vertical shaft wall considering the influence of the grouting ring, relating to the field of mining construction engineering. Considering the composite load-bearing structure of surrounding rock-grouting ring-shaft wall formed after deep surrounding rock grouting and water plugging, and combining the seepage and stress coupling effects in the composite structure, calculation formulas for the water pressure and total load of the shaft wall are established through laboratory and field parameter tests and simple algebraic calculations. The technical solution of this invention is carried out in the following steps: Step 1, sample property testing; Step 2, field parameter testing; Step 3, calculation of water pressure load on the outside of the shaft wall; Step 4, calculation of the total load on the outside of the shaft wall. This invention can provide a theoretical basis for the stress analysis and structural design of the shaft wall in grouting and water plugging reinforcement of strata, and has significant engineering application value.

Description

Technical Field

[0001] This invention relates to the field of mining construction engineering. Background Technology

[0002] my country possesses abundant reserves of mineral resources such as coal and metals. Vertical shafts, as vital passageways to underground spaces, are a crucial foundation and prerequisite for the efficient and safe extraction of these resources. The shaft wall structure is a key support component within the vertical shaft, bearing the pressure from external rock and groundwater; its safety directly impacts the long-term stable operation of the shaft. The load-structure method, an important approach to shaft wall design, requires the rational determination of the water pressure and total load on the shaft wall, thereby providing a reliable basis for the design of the shaft wall structure.

[0003] Traditional wellbore design typically uses ground pressure test values ​​as the external load on the wellbore, which can easily overestimate the actual load acting on the wellbore. In recent years, the concept of shared load-bearing between the surrounding rock and the wellbore has gained increasing attention, and related research has begun to analyze the external load characteristics of the wellbore from the perspective of shared stress. For water-bearing formations, grouting is a commonly used engineering measure. The grouting process not only achieves water stoppage but also reinforces the original surrounding rock, thus forming a multi-layered composite load-bearing structure of surrounding rock-grouting ring-wellbore. In this composite structure, the seepage process and mechanical deformation are coupled, and the reasonable determination of the water pressure and total load borne by the wellbore under these effects is the prerequisite and key to designing the wellbore structure for grouting-sealed formations. Summary of the Invention

[0004] To address the above problems, this invention proposes a method for determining the water pressure and total load of a vertical shaft wall that considers the influence of the grouting ring. It takes into account the composite bearing structure of the surrounding rock-grouting ring-well wall formed after deep surrounding rock grouting and water plugging, and combines the seepage and stress coupling effect in the composite structure. Through laboratory and field parameter tests and simple algebraic calculations, the calculation formulas for the water pressure and total load of the well wall are established.

[0005] The technical solution of this invention is as follows: It is carried out according to the following steps:

[0006] Step 1: Sample property testing;

[0007] Based on the grade of the well wall concrete used, find its mechanical parameters, including the elastic modulus. Poisson's ratio Effective stress coefficient Permeability coefficient k1;

[0008] Core samples were taken from both the original surrounding rock and the grouting-reinforced surrounding rock around the shaft to prepare standard specimens. Triaxial and permeability tests were then conducted in the laboratory to obtain some parameters required for subsequent calculations, including the elastic modulus of the grouting ring. Poisson's ratio Effective stress coefficient Permeability coefficient k2, original surrounding rock elastic modulus Poisson's ratio Effective stress coefficient Permeability coefficient k3;

[0009] Step 2: On-site parameter testing;

[0010] In-situ tests were conducted on the formation conditions around the shaft to obtain the formation porosity n and the effective stress of the original rock. Original water pressure ;

[0011] In the actual grouting and water plugging reinforcement process, grouting is carried out by perforation into the sidewall of the grouting pipe. The grout diffuses along a cylindrical surface. For a grouting section of height H, the actual grouting volume per hole is... Calculate the slurry diffusion radius R;

[0012] Step 3: Calculation of water pressure load on the outside of the well wall;

[0013] Based on the well wall geometry, determine the inner radius r1 and outer radius r2 of the well wall; based on the slurry diffusion radius R and the radius r of the grouting pipe... g Determine the grouting ring radius r3 = r g + R; the radius of the influence circle r4 is selected as 100m~200m; the total water resistance is calculated and determined. Total water flow q;

[0014] Further calculation of the water pressure load on the outside of the well wall And the dimensionless water pressure load on the outside of the well wall, i.e., the water pressure reduction factor. ;

[0015] Step 4: Calculation of total load on the outside of the well wall;

[0016] Calculate and determine plane strain parameters. ;

[0017] In the formula, the subscripts i = 1, 2, 3 represent the wellbore layer, the grouting layer, and the original rock layer, respectively;

[0018] Calculate coefficients , ;

[0019] Calculate coefficients :

[0020] ;

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] The displacement and effective stress forms in the three regions are as follows:

[0027] ;

[0028] ;

[0029] The boundary conditions for r=r1 and r = r4 are as follows:

[0030] ;

[0031] The continuity conditions for displacement and total stress at r=r2 and r=r3 are as follows:

[0032] ;

[0033] ;

[0034] Based on the above six conditions and the specific forms of displacement and effective stress, namely, based on the boundary conditions at r = r1, r4 and the continuity conditions of displacement and total pressure at r = r2, r3, the following six linear equations can be established, and solving them will yield the coefficients. , , , , , ;

[0035] ;

[0036] ;

[0037] ;

[0038] ;

[0039] ;

[0040] ;

[0041] Calculate the effective stress pressure on the outer side of the wellbore:

[0042] ;

[0043] Calculate the total load on the outer side of the well wall ;

[0044] Calculate the dimensionless total load on the outer side of the well wall, i.e., the total load reduction factor. , .

[0045] In step two, the slurry diffusion radius R is calculated using the following formula: ;

[0046] Among them, the slurry filling coefficient Slurry loss coefficient All are empirical coefficients, with values ​​taken from grouting reinforcement specifications such as the "Technical Specification for Building Foundation Treatment"; n is the porosity of the stratum obtained from in-situ testing.

[0047] In step three, the total water resistance is calculated using the following formula. :

[0048] ;

[0049] The total water flow q is calculated using the following formula. .

[0050] In step three of the calculation, using , , Let represent the functions of water pressure in the wellbore, grouting ring, and original rock strata as a function of radius r, respectively. Then, their specific forms are as follows:

[0051] ;

[0052] ;

[0053] ;

[0054] Calculate the water pressure load outside the well wall using the following formula. , ;

[0055] The dimensionless water pressure load on the outside of the well wall, i.e., the water pressure reduction factor, is calculated using the following formula. , .

[0056] Vertical shaft construction is of great significance for the mining of deep coal, metals, and other mineral resources in my country. Accurately determining the water pressure and total load on the shaft wall is a crucial prerequisite for shaft wall design. For water-bearing strata, grouting is a common reinforcement measure when the water inflow may exceed the shaft's allowable standard. After grouting, a composite load-bearing structure of surrounding rock, grouting ring, and shaft wall is formed. However, for this composite structure, there is still a lack of methods to rationally determine the water pressure and total load on the shaft wall from the perspectives of seepage-stress coupling and the shared load-bearing capacity of the surrounding rock and shaft wall.

[0057] This invention addresses the multi-layered composite load-bearing structure of surrounding rock, grouting ring, and well wall formed after grouting and water plugging of surrounding rock. Considering the coupling effect of seepage and stress under well wall seepage conditions, it establishes calculation formulas for the water pressure and total load on the well wall. This invention provides a theoretical basis for the stress analysis and structural design of well walls in grouting and water plugging reinforcement of formations, and has significant engineering application value. Attached Figure Description

[0058] Figure 1 This is a calculation model diagram of the original surrounding rock, grouting ring, and well wall.

[0059] Figure 2 It is the influence of grouting ring parameters on the water pressure reduction coefficient.

[0060] Figure 3 It is the influence of the grouting ring parameters on the total load reduction factor;

[0061] In the diagram: 1-Well wall concrete; 2-Grouting ring; 3-Original surrounding rock. Detailed Implementation

[0062] To clearly illustrate the technical features of the present invention, the present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0063] In vertical shaft engineering, the water pressure and total load on the shaft wall are crucial prerequisites for conducting stress analysis and related design. In aquifers, grouting is a commonly used method for controlling water inflow, and it also reinforces the surrounding rock. However, for vertical shafts reinforced by grouting, there is currently a lack of methods for determining the water pressure and total external load borne by the shaft wall when considering seepage-stress coupling and the combined load-bearing capacity of the surrounding rock, grouting ring, and shaft wall.

[0064] This invention creates a method for calculating the water pressure and total load on a well wall in a formation after grouting and water plugging reinforcement. This method involves steps such as sample parameter testing, field parameter testing, calculation of water pressure outside the well wall, and calculation of the total external load on the well wall.

[0065] The method for calculating the water pressure and total load on the well wall established in this invention comprehensively considers the joint bearing capacity of the surrounding rock, grouting ring, and well wall, as well as the seepage-stress response of the composite structure. It has the advantages of simple process, simple formula, convenient operation, and close application to engineering, and can lay the foundation for the stress analysis and well wall design of well walls in grouting and reinforced formations.

[0066] For example, regarding the stress on the wall of the auxiliary shaft of the Menkeqing Coal Mine, the method of this invention was used to determine the water pressure and total load on the outer side of the shaft wall. There are few published documents on the field stress measurements of shaft walls after grouting and water plugging. While the auxiliary shaft of the Menkeqing Coal Mine did not undergo grouting and water plugging, complete field load test results are available. The inner radius of the shaft wall is r1 = 5m, the outer radius is r2 = 1.8m, and the influence zone is r4 = 150m; the elastic modulus of the surrounding rock is E3 = 9.925 GPa, the Poisson's ratio is μ3 = 0.35, and the permeability coefficient is k3 = 8.33 × 10⁻⁶. −9 m / s, effective stress coefficient of surrounding rock α3=0.75; wellbore elastic modulus E1=36.5 GPa, wellbore Poisson's ratio μ1 = 0.15, wellbore permeability coefficient k1=4.02×10 −10 The effective stress coefficient of the well wall is α3 = 0.122, and the actual parameters of the grouting ring in area 2 are the same as those of the surrounding rock in area 3 since there is no grouting. The depth of the calculation location is 670m, the original water pressure is 6.7MPa, and the original effective stress pressure is 2.25MPa. Using the method of this invention, the water pressure on the well wall at the test point is 4.03MPa, and the total load is 4.41MPa. The actual measured pore water pressure on the well wall is 4.12MPa, and the total load is 4.02MPa. The calculation method of this invention matches the actual measured value on the engineering site well.

[0067] The calculation method in this invention can also be used to analyze the influence of grouting ring parameters on the water pressure and total load on the well wall. The inner and outer radii of the well wall are r1=4.5m and r2=5.4m, respectively, and the radius of the surrounding rock influence zone is r4=150m; the elastic modulus, Poisson's ratio, permeability coefficient, and effective stress coefficient of the well wall are E1=32.01GPa, μ1=0.15, and k1=5.1×10, respectively. −15 m / s, α1=0.15. The elastic modulus, Poisson's ratio, permeability coefficient, and effective stress coefficient of the surrounding rock are E3=10.55GPa, μ3=0.35, k3=1.0×10 m / s, α1=0.15. −12 m / s, α3=0.75; initial formation water pressure and effective stress pressure are respectively P w0 =20 MPa, P sb =12 MPa. The parameters in the grouting ring can be set based on the original surrounding rock parameters. The elastic modulus, Poisson's ratio, permeability coefficient, effective stress coefficient, and thickness of the grouting ring are determined according to E2 / E3=2, μ3 / μ2=1.8, k3 / k2=200, α3 / α2=1.8, r3-r2 =15m. These grouting ring parameters are baseline parameters. When studying the influence of a certain grouting ring parameter, that parameter varies within the set range, while the other parameters remain set according to the baseline parameters. The calculation is performed using the method of this invention. Figure 2 The image shows the contour map results of the water pressure reduction coefficient distribution at different r3-r2 and k3 / k2. Figure 3 The figure shows the contour map results of the total load factor distribution at different r3-r2 and E2 / E3.

[0068] There are many specific ways to implement this invention. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A method for determining the wall water pressure and total load of a vertical shaft considering the influence of the grouting ring, characterized in that, Follow these steps: Step 1: Sample property testing; Based on the grade of the well wall concrete used, find its mechanical parameters, including the elastic modulus. Poisson's ratio Effective stress coefficient Permeability coefficient k1; Core samples were taken from both the original surrounding rock and the grouting-reinforced surrounding rock around the shaft to prepare standard specimens. Triaxial and permeability tests were then conducted in the laboratory to obtain some parameters required for subsequent calculations, including the elastic modulus of the grouting ring. Poisson's ratio Effective stress coefficient Permeability coefficient k2, original surrounding rock elastic modulus Poisson's ratio Effective stress coefficient Permeability coefficient k3; Step 2: On-site parameter testing; In-situ tests were conducted on the formation conditions around the shaft to obtain the formation porosity n and the effective stress of the original rock. Original water pressure ; In the actual grouting and water plugging reinforcement process, grouting is carried out by perforation into the sidewall of the grouting pipe. The grout diffuses along a cylindrical surface. For a grouting section of height H, the actual grouting volume per hole is... Calculate the slurry diffusion radius R; Step 3: Calculation of water pressure load on the outside of the well wall; Based on the well wall geometry, determine the inner radius r1 and outer radius r2 of the well wall; based on the slurry diffusion radius R and the radius r of the grouting pipe... g Determine the grouting ring radius r3 = r g + R; The radius of the influence circle r4 is selected to be 100m~200m; Calculate and determine total water resistance Total water flow q; Further calculation of the water pressure load on the outside of the well wall And the dimensionless water pressure load on the outside of the well wall, i.e., the water pressure reduction factor. ; Step 4: Calculation of total load on the outside of the well wall; Calculate and determine plane strain parameters. ; In the formula, the subscripts i = 1, 2, 3 represent the wellbore layer, the grouting layer, and the original rock layer, respectively; Calculate coefficients , ; Calculate coefficients : ； ； ； ； ； ； Based on the boundary conditions at r = r1, r4 and the continuity conditions for displacement and total pressure at r = r2, r3, the following six linear equations can be established, and the coefficients can be obtained by solving them. , , , , , ; ； ； ； ； ； ； Calculate the effective stress pressure on the outer side of the wellbore: ； Calculate the total load on the outer side of the well wall ; Calculate the dimensionless total load on the outer side of the well wall, i.e., the total load reduction factor. , .

2. The method for determining the wall water pressure and total load of a vertical shaft considering the influence of the grouting ring, as described in claim 1, is characterized in that... In step two, the slurry diffusion radius R is calculated using the following formula: ; Among them, the slurry filling coefficient Slurry loss coefficient All are empirical coefficients, with values ​​taken from grouting reinforcement specifications such as the "Technical Specification for Building Foundation Treatment"; n is the porosity of the stratum obtained from in-situ testing.

3. The method for determining the wall water pressure and total load of a vertical shaft considering the influence of the grouting ring, as described in claim 1, is characterized in that... In step three, the total water resistance is calculated using the following formula. : ； The total water flow q is calculated using the following formula. .

4. The method for determining the wall water pressure and total load of a vertical shaft considering the influence of the grouting ring, as described in claim 2, is characterized in that... In step three of the calculation, using , , Let represent the functions of water pressure in the wellbore, grouting ring, and original rock strata as a function of radius r, respectively. Then, their specific forms are as follows: ； ； ； Calculate the water pressure load outside the well wall using the following formula. , ; The dimensionless water pressure load on the outside of the well wall, i.e., the water pressure reduction factor, is calculated using the following formula. , .

Images