Method for determining parameters of precise protection of ground surface target in mining area by bed separation grouting

Abstract

The application discloses a kind of determination methods of precision protection separation layer grouting parameters of surface target in mining area, and the application is finally obtained grouting drilling depth, grouting pressure, grouting drilling position according to the mining geological conditions of working face, surface and overburden movement and deformation parameters, surface protection target grade and the relative position relationship of surface protection target and working face.Through the grouting drilling of surface protection target construction, separation layer grouting is carried out, the change from yes to no of mining influence from far to near surface protection target is realized, the normal mining of longwall working face is not affected, and the surface movement and deformation near surface protection target is eliminated, so as to realize the precision protection of surface protection target facilities in the mining influence range of longwall mining working face.The precision protection of surface (only protection arrangement is carried out to surface protection target) is realized, the double purposes of safe and efficient recovery of working face and the stability of surface protection target are ensured.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, specifically to a method for determining the parameters of grouting for precise protection of surface targets within a mining area. By performing grouting near the surface protection target, precise protection of the surface protection target can be achieved. Background Technology

[0002] After coal seam mining, free space is created at the bottom of the overlying strata. Under the immense pressure from the upper strata, the bottom strata begin to bend and deform. The larger the unsupported area, the more severe the bending deformation. When the unsupported area reaches a certain size, it eventually breaks and becomes unstable. After the bottom strata break, new free space forms beneath the upper strata, and bending deformation, breaking, and instability begin to occur – a process of upward transmission of damage. As the mining area continues to expand, the damage and upward transmission process continues, eventually reaching the surface, causing surface movement and deformation, resulting in ground fissures and subsidence areas. This also damages surface structures, water bodies, railways, and other facilities within the mining impact zone.

[0003] During coal mining, the stability of surface structures, water bodies, railways, and other facilities affects numerous issues, including the safe and efficient recovery of the working face, coal resource extraction rate, environmental protection, and mine cluster relationships. Therefore, researching protection technologies for surface facilities within the mining impact area is of great significance for achieving safe and efficient mine recovery, improving coal extraction rate, protecting the environment, and mitigating mine cluster relationships.

[0004] For the protection of surface buildings, water bodies, railways, and other facilities within the mining area, underground technical solutions mainly include retaining protective coal pillars, strip mining, backfilling mining, and room-and-pillar mining. These solutions share the common advantage of effectively reducing the impact of underground coal seam mining on surface facilities; however, they each also have significant drawbacks. Retaining protective coal pillars and strip mining will reduce coal recovery rates, waste coal resources, and hinder the sustainable development of the mine. Backfilling mining requires specialized technology and equipment, places high demands on the management of the working face, increases production costs, and the interaction between backfilling and mining results in low production efficiency, hindering high-efficiency mine production. Room-and-pillar mining has high requirements for coal seam occurrence conditions, poor applicability, and poor ventilation, resulting in low coal recovery rates and hindering green and safe mine production. Furthermore, once the working face mining plan is determined, the same plan is used from the opening cut to the stopping line, making it impossible to change the mining plan for specific surface protection targets. Therefore, its applicability for achieving localized and precise protection of surface protection targets within the mining impact area is poor.

[0005] For the protection of surface buildings, water bodies, railways, and other facilities within the mining area, surface technical solutions can be divided into two categories. One category aims to reduce the impact of surface movement and deformation on protective facilities, while the other aims to strengthen the strength and rigidity of protective facilities to resist movement and deformation, thus achieving precise protection of surface targets. The first category mainly includes measures such as excavating deformation trenches, setting deformation joints, and horizontal sliding layers. The second category mainly involves installing steel tie rods, reinforced concrete ring beams, reinforcing foundations, and subsequent maintenance. In some cases, both underground and surface measures can be used simultaneously to protect surface buildings, water bodies, railways, and other facilities within the mining area. While surface technical solutions can protect surface targets, they are applicable only when the impact of coal seam mining on surface facilities is within a controllable range. When the impact of mining on the working face is significant, surface technical solutions will become ineffective.

[0006] In addition to the aforementioned protection technologies, there is another technique for controlling surface movement: traditional delamination grouting. Its principle involves high-pressure grouting within the overburden delamination, filling it with grout. As the fluid in the delamination decreases, the fluid is transferred upwards, thus reducing surface movement and deformation. This grouting process does not affect the underground working face's mining operations. Traditional delamination grouting is performed on the overburden delamination before the mining impact reaches the surface (i.e., before surface movement or deformation). The traditional delamination grouting process spans the entire mining cycle from start to finish, resulting in a long grouting period, but it does control the entire mining-affected area. However, when only surface protection targets within the mining area require protection, the investment in traditional delamination grouting is partially wasted. Therefore, traditional delamination grouting is not suitable for the precise protection of surface protection targets.

[0007] For the protection of surface buildings, water bodies, railways, and other facilities within mining areas, underground protection technology can fundamentally reduce the impact of coal seam mining on surface facilities. However, it has drawbacks, such as being detrimental to the production requirements of safe, efficient, green, and sustainable development of mines, and being unsuitable for protecting surface protection targets within the mining impact area. Surface protection technology has a narrow scope of application and cannot be used in areas severely affected by mining, failing to achieve the goal of protecting surface protection targets at any location within the mining impact area. Traditional delamination grouting technology has a long filling cycle and a wide control range (resulting in significant ineffective investment when only surface protection targets need to be protected), failing to achieve precise protection of surface protection targets. Therefore, to achieve the goal of ensuring safe, efficient, green, and sustainable development of mines while also protecting surface protection targets at any location within the mining impact area, a method for determining delamination grouting parameters for precise protection of surface targets within mining areas is proposed. Summary of the Invention

[0008] To address the shortcomings of existing protection technologies and to achieve both safe, efficient, and green coal seam mining, as well as precise protection of surface targets within the mining area, this invention provides a method for determining the grouting parameters for precise protection of surface targets within the mining area. This method is highly applicable and easy to operate.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A method for determining the grouting parameters for precise protection of surface targets within a mining area includes the following steps:

[0011] S1. Based on the collected mining geological data, determine the structure and lithology of the overlying strata on the working face, and the strike and boundary angle of the working face. σ 0 Maximum subsidence angle of the working face θ Coal seam burial depth near surface protection target H 0 The characteristics of the surface protection targets and their relative positional relationship with the working face;

[0012] S2. Determine the width of the maintenance zone for the surface protection targets based on their protection levels. l b ;

[0013] S3. Based on the structure and lithology of the overlying strata on the working face, the water-conducting fracture zone and the stratigraphic position of the hard rock layer in the overlying strata are obtained. Finally, the stratigraphic position for overlying strata separation grouting is determined, and the height of the grouting position from the coal seam is obtained. H Z ;

[0014] S4. Based on the orientation and boundary angle of the working face. σ 0 Determine the impact distance of mining at the working face. l c :

[0015] ;

[0016] In the formula, l c The influence distance of the working face mining is expressed in meters. H 0 The depth of coal seams near surface protection targets, in meters; σ 0 The working face's boundary angle, in degrees;

[0017] S5. Based on the fracture angle of the overlying strata The distance from the working face when the rock strata fractures is obtained by considering the height of the grouting layer.

[0018] ;

[0019] In the formula, l p The distance of delayed fracture of the rock strata at the grouting site is expressed in meters. H Z This refers to the height of the grouting layer from the coal seam, in meters (m). The fracture angle of the overlying strata, in degrees;

[0020] S6. Based on the grouting layer, obtain the location, lithology, and load-bearing characteristics of the adjacent hard rock layer below the grouting layer, and calculate the periodic fracture distance of the rock layer. l z ;

[0021] S7. Based on the width of the maintenance zone of the surface protection target, the impact distance of the working face mining, the delayed fracture distance of the rock strata at the grouting layer, and the periodic fracture distance of the rock strata, the minimum distance between the boundary grouting borehole and the surface protection target is finally determined. l :

[0022] ;

[0023] In the formula, l The minimum distance between the boundary grouting borehole and the surface protection target, in meters;

[0024] S8. Calculate the grouting pressure based on the borehole depth from the ground surface to the grouting layer, the comprehensive unit weight of the strata above the grouting layer, and the unit weight of the grouting fluid. P Z :

[0025] ;

[0026] In the formula, P Z This refers to the grouting pressure at the orifice, expressed in MPa. H g The depth of the borehole from the ground surface to the grouting filling layer is expressed in meters (m). γ The unit weight of the strata above the grouting filling layer is expressed in kN / m³. 3 ; γ 1 The density of the filling grout, expressed in kN / m³. 3 ;

[0027] S9. Based on the maximum sinking angle of the working surface θ and the height of the grouting layer from the coal seam H ZThe main subsidence section of the subsidence grouting layer was obtained. Due to the dip angle of the coal seam, the main subsidence section shifted from the center of the goaf in the downward direction. The distance of this downward shift from the center of the goaf was determined. d :

[0028] ;

[0029] In the formula, d The unit is the distance the main subsidence section is offset from the center of the goaf in the downward direction, in meters; H z This refers to the height of the grouting layer from the coal seam, in meters (m). θ The maximum downward angle of the working face, in degrees;

[0030] S10. Based on the relative positional relationship between the surface protection target and the coal seam mining area, the distance between the boundary grouting borehole and the surface protection target, the grouting borehole pressure and the diffusion radius of the grout, the distance between the grouting boreholes is comprehensively determined to obtain the position of the separation grouting borehole on the main cross section of the subsidence direction.

[0031] As an improvement to the above technical solution, in step S1, the overburden lithology is determined using the overburden comprehensive evaluation coefficient. P X The evaluation and analysis were conducted, and the calculation method is as follows:

[0032] ;

[0033] In the formula, m i Overlying rock i The normal thickness of the layer, in meters (m). Q i Overlying rock i Layered lithology evaluation coefficient.

[0034] As an improvement to the above technical solution, in step S1, the orientation boundary angle of the working surface... σ 0 Maximum subsidence angle of the working face θ The selection is based on the analysis parameters of the measured data of the mining area; for mining areas without measured data, the selection is based on the lithological conditions obtained in step S1.

[0035] As an improvement to the above technical solution, in step S2, when determining the width of the maintenance zone for the surface protection target, the selection shall be made in accordance with the relevant provisions of the "Specifications for the Retention of Coal Pillars and Coal Mining for Buildings, Water Bodies, Railways and Main Shafts".

[0036] As an improvement to the above technical solution, in step S3, when selecting the grouting layer, the height of the water-conducting fracture zone can be analyzed based on the measured data of the mining area. For mining areas without measured data, the height can be selected based on the lithological conditions obtained in step S1, according to empirical formulas.

[0037] As an improvement to the above technical solution, in step S3, when selecting the grouting layer, the calculation method for determining the hard rock layer in the overburden is as follows:

[0038] ;

[0039] ;

[0040] In the formula: i Numbering of hard rock strata from bottom to top; q n ) i For the first i No. 1 hard rock layer bears the upper part n The load on the rock strata, in kPa; E Here is the elastic modulus of each rock layer, in MPa; h The thickness of each rock layer is given in meters (m). γ The unit weight of the strata above the grouting filling layer is expressed in kN / m³. 3 .

[0041] As an improvement to the above technical solution, in step S6, the periodic fracture distance of the rock strata is calculated as follows:

[0042] ;

[0043] In the formula: l z The periodic fracture distance of the rock strata is expressed in meters. h z The thickness of the rock strata at the grouting site is in meters (m). q z The load borne by the rock strata at the grouting site is expressed in MPa. R T The tensile strength of the rock strata in the grouting zone is expressed in MPa.

[0044] As an improvement to the above technical solution, in step S10, the grouting boreholes are arranged on the sinking main cross-section of the grouting layer, and straight holes or inclined holes are used for delamination grouting.

[0045] Compared with the prior art, the advantages and positive effects of this invention are:

[0046] This invention addresses the problem of damage to surface protection facilities caused by coal seam mining, achieving the goals of safe and efficient mining of the working face while ensuring the stability of surface protection facilities. Based on the mining geological conditions of the working face, surface and overlying rock movement and deformation parameters, the level of surface protection targets, and the relative positional relationship between the surface protection targets and the working face, this invention ultimately determines the grouting borehole depth, grouting pressure, and grouting borehole location. By performing ex-layer grouting through the grouting boreholes used for surface protection target construction, the impact of mining on the surface protection targets is reduced from present to absent, achieving the goal of eliminating surface movement and deformation near the surface protection targets without affecting the normal mining of the longwall face. This provides precise protection for surface protection facilities within the mining impact range of the longwall mining face. Precise protection of surface protection targets (protection arrangements only for surface protection targets) achieves the dual objectives of safe and efficient mining of the working face and ensuring the stability of surface protection targets. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 The surface protection target is located in the middle of the working face;

[0049] Figure 2 The surface protection target is located near the opening of the working face;

[0050] Figure 3 The surface protection target is located near the working face's stop-mining line;

[0051] Figure 4 This is a diagram showing the location of the main subsidence section;

[0052] Figure 5 Diagram showing the grouting hole layout for precise protection technology of delamination grouting;

[0053] Figure 6 Contour map of surface subsidence in the river and surrounding area for direct mining at the working face;

[0054] Figure 7 Contour map showing the direction and slope of the river and nearby land surface for direct mining at the working face;

[0055] Figure 8 Contour map of the river and nearby surface dip and slope for direct mining at the working face;

[0056] Figure 9Contour map showing the horizontal movement of the river and nearby surface features for direct mining at the working face;

[0057] Figure 10 Contour map of the horizontal movement of the surface in and around the river where the working face is directly excavated;

[0058] Figure 11 Contour map of horizontal deformation along the river and nearby surface for direct mining at the working face;

[0059] Figure 12 Contour map of horizontal deformation of the river and nearby land surface in the working face for direct mining;

[0060] Figure 13 Contour map of surface subsidence in the river and surrounding area after the application of precise protection technology for delamination grouting;

[0061] Figure 14 This is a contour map showing the direction and slope of the river and nearby land surface after the application of the precise protection technology of delamination grouting;

[0062] Figure 15 Contour map of the river and surrounding land surface dip and tilt after the application of the delamination grouting precision protection technology;

[0063] Figure 16 This is a contour map showing the horizontal movement of the river and the surrounding land surface after the application of the precise protection technology of delamination grouting.

[0064] Figure 17 This is a contour map showing the horizontal movement of the river and nearby land surface after the application of the precise protection technology of delamination grouting;

[0065] Figure 18 This is a contour map of horizontal deformation along the river and nearby land surface after the application of the precise protection technology of delamination grouting.

[0066] Figure 19 This is a contour map of horizontal deformation of the river and nearby land surface after the application of the precise protection technology of delamination grouting. Detailed Implementation

[0067] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] like Figure 1-4 As shown, this invention provides a method for determining the grouting parameters for precise protection of surface targets within a mining area, comprising the following steps:

[0069] Step 1: Based on the collected mining geological data, determine the structure and lithology of the overlying strata on the working face, the mining range of the working face, and the boundary angle of the working face. σ 0 Maximum subsidence angle of the working face θ Coal seam burial depth near surface protection target H 0 The characteristics of the surface protection targets and their relative positional relationship with the working face;

[0070] Among them, the overlying lithology adopts the comprehensive evaluation coefficient of overlying lithology. P X The evaluation and analysis were conducted, and the calculation method is as follows:

[0071] ;

[0072] In the formula, m i Overlying rock i The normal thickness of the layer, in meters (m). Q i Overlying rock i Layered lithology evaluation coefficient.

[0073] Working face orientation boundary angle σ 0 Maximum subsidence angle of the working face θ The selection is based on the analysis parameters of the measured data of the mining area; for mining areas without measured data, the selection is based on the lithological conditions obtained in step S1.

[0074] Step 2: Determine the width of the maintenance zone for the surface protection targets based on their protection level. l b When determining the width of the maintenance zone for surface protection targets, the selection shall be made in accordance with the relevant provisions of the "Specifications for the Retention of Coal Pillars and Coal Mining under Pressure in Buildings, Water Bodies, Railways and Main Shafts".

[0075] Step 3: Based on the structure and lithology of the overlying strata on the working face, the water-conducting fracture zone and the stratigraphic position of the hard rock layer in the overlying strata are obtained. Finally, the stratigraphic position for overlying strata separation grouting is determined, and the height of the grouting position from the coal seam is obtained. H Z When selecting the grouting layer, the height of the water-conducting fracture zone can be determined based on the measured data of the mining area. For mining areas without measured data, the selection can be based on the lithological conditions obtained in step S1, using empirical formulas.

[0076] When selecting the grouting layer, the calculation method for determining the hard rock layer in the overburden is as follows:

[0077] ;

[0078] ;

[0079] In the formula: i Numbering of hard rock strata from bottom to top; q n ) i For the i-th hard rock layer to bear the upper part n The load on the rock strata, in kPa; E Here is the elastic modulus of each rock layer, in MPa; h The thickness of each rock layer is given in meters (m). γ The unit weight of the strata above the grouting filling layer is expressed in kN / m³. 3 .

[0080] Step 4: Determine the boundary angle based on the orientation of the working face. σ 0 Determine the impact distance of the working face mining l c :

[0081] ;

[0082] In the formula, l c The influence distance of the working face mining is expressed in meters. H 0 The depth of the coal seam near the surface protection structure, in meters; σ 0 The working face's boundary angle, in degrees.

[0083] Step 5: Based on the fracture angle of the overlying strata and the height of the grouting layer H Z This gives the distance from the rock strata to the working face when the rock strata fracture.

[0084] ;

[0085] In the formula, l p The distance of delayed fracture of the rock strata at the grouting site is expressed in meters. H Z The height of the grouting layer from the coal seam, in meters; The angle is the fracture angle of the overlying rock strata, measured in degrees.

[0086] Step 6: Based on the grouting layer, determine the location, lithology, and load-bearing capacity of the adjacent hard rock layer below the grouting layer, and calculate the periodic fracture distance of the rock layer. l z The periodic fracture distance of the rock strata is calculated as follows:

[0087] ;

[0088] In the formula: l z The periodic fracture distance of the rock strata is expressed in meters. h z The thickness of the rock strata at the grouting site is in meters (m). q z The load borne by the rock strata at the grouting site is expressed in MPa. R T The tensile strength of the rock strata in the grouting zone is expressed in MPa.

[0089] Step 7: Based on the width of the maintenance zone for the surface protection target, the impact distance of the working face mining, the delayed fracture distance of the rock strata at the grouting layer, and the periodic fracture distance of the rock strata, finally determine the minimum distance between the boundary grouting borehole and the surface protection object. l :

[0090] ;

[0091] In the formula, l The minimum distance between the boundary grouting borehole and the surface protection structure, in meters.

[0092] Step 8: Calculate the grouting pressure based on the borehole depth from the ground surface to the grouting layer, the overall unit weight of the strata above the grouting layer, and the unit weight of the grouting fluid. P Z :

[0093] ;

[0094] In the formula, P Z This refers to the grouting pressure at the orifice, expressed in MPa. H g The depth of the borehole from the ground surface to the grouting filling layer is expressed in meters (m). γ The unit weight of the strata above the grouting filling layer is expressed in kN / m³. 3 ; γ 1 The density of the filling grout, expressed in kN / m³. 3 .

[0095] Step 9: Based on the maximum sinking angle of the working face θ and the height of the grouting layer from the coal seam H z The main subsidence section of the subsidence grouting layer was obtained. Due to the dip angle of the coal seam, the main subsidence section shifted from the center of the goaf in the downward direction. The distance of this downward shift from the center of the goaf was determined. d :

[0096] ;

[0097] In the formula, d The unit is the distance the main subsidence section is offset from the center of the goaf in the downward direction, in meters; H z This refers to the height of the grouting layer from the coal seam, in meters (m). θ The maximum downward angle of the working face is expressed in degrees.

[0098] Step 10: Based on the relative position of the surface protection target and the coal seam mining area, the distance between the transition hole and the surface protection object, the grouting borehole pressure and the diffusion radius of the grout, the distance between the grouting boreholes is determined comprehensively to obtain the position of the separation grouting borehole on the main cross section of the subsidence direction.

[0099] exist Figure 1-4 In the attached diagram, 1 represents the hard rock layer in the overburden, 2 represents the thickness of the grouting protective layer, 3 represents the rock layer adjacent to the grouting location above, 4 represents the rock layer fracture angle, 5 represents the rock layer strike boundary angle, 6 represents the grouting borehole, and 7 represents the maximum subsidence angle of the working face.

[0100] The following is based on specific field conditions and Figure 5-19 This will explain the theoretical basis and origin of the present invention.

[0101] A certain mine used the probability integral method to calculate the river movement and deformation after coal seam mining in two scenarios: without overburden separation grouting (direct mining of longwall faces) and with precise protection technology using overburden separation grouting. The calculation was conducted under two schemes, as follows:

[0102] Option 1: No overburden separation grouting was used at the working face; surface movement and deformation are expected.

[0103] Option 2: The working face adopts the method of overburden separation grouting mining to predict surface movement and deformation.

[0104] Table 1. Parameter Selection Table for Probability Integration Method

[0105] ;

[0106] Based on the predicted parameters of different schemes in Table 1, surface movement and deformation calculations were performed for two schemes: one where the working face was not mined and the other where the overlying rock separation grouting method was adopted. The calculation results were visualized using MATLAB and Surfer, and surface subsidence contour maps, surface tilt contour maps, surface horizontal movement contour maps, and surface horizontal deformation contour maps were given.

[0107] According to Option 1, the surface movement and deformation near the river are as follows: Figures 6-12 As shown; according to Scheme 2, the surface movement and deformation near the river are as follows. Figures 13-19As shown.

[0108] Without using overburden separation grouting for mining, the maximum displacement and deformation values ​​at the river location are as follows: maximum surface subsidence of approximately 900 mm, maximum strike dip of approximately 1 mm / m, maximum dip tilt of approximately 9 mm / m, maximum horizontal strike displacement of approximately 40 mm, maximum horizontal dip displacement of approximately 550 mm, maximum horizontal strike deformation of approximately 0.1 mm / m, and maximum horizontal dip deformation of approximately 6 mm / m.

[0109] The working face adopts precise protection calculation mining with overburden separation grouting. The maximum surface movement and deformation values ​​at the river location are as follows: maximum surface subsidence is about 250 mm, maximum strike dip is about 0.5 mm / m, maximum dip tilt is about 1 mm / m, maximum strike horizontal movement is about 20 mm, maximum dip horizontal movement is about 150 mm, maximum strike horizontal deformation is about 0.6 mm / m, and maximum dip horizontal deformation is about 2 mm / m.

[0110] The maximum values ​​of surface movement and deformation at the river channel locations are summarized in Table 2;

[0111] Table 2. Maximum values ​​of surface movement and deformation near the river after mining operations.

[0112] ;

[0113] from Figure 6 and Figure 13 As can be seen, the subsidence values ​​of the two schemes differ significantly at the river channel location, while the surface subsidence values ​​outside the river channel are not significantly different, reflecting the concept of precision protection.

[0114] According to the calculations of Scheme 1, without overburden separation grouting, the maximum subsidence of the river channel after mining will reach approximately 0.9 m, and the maximum tensile horizontal deformation within the river channel will reach 6 mm / m. The damage to the river channel will primarily occur downhill from the working face. The river channel directly above the working face will experience a maximum subsidence of 0.9 m, causing subsidence in this section of the riverbed. This will result in some water accumulation in this section, increasing the local water depth and expanding the catchment area in certain areas. Furthermore, after mining, the maximum tensile horizontal deformation within the river channel will reach 6 mm / m, leading to ground fissures on the riverbanks and surface. The depth of these fissures will vary from several meters to tens of meters, depending on factors such as the magnitude of surface deformation and the mechanical properties of the surface soil and rock. In conclusion, if mining proceeds directly without intervention, significant surface subsidence will occur around the riverbed, cracks will appear in the riverbanks, and given the terrain conditions of the area, overflowing and water accumulation are possible.

[0115] According to the calculation results of Scheme 2, after adopting the precise protection of overburden separation grouting, the maximum subsidence of the river channel after mining will reach approximately 0.25 m, and the maximum tensile horizontal deformation within the river channel will reach 2 mm / m, located in the downhill direction of the working face. Referring to the allowable limit deformation value (horizontal deformation ε=2.5 mm / m) of concrete river dams in the "Guidelines for Coal Pillar Retention and Coal Mining in Buildings, Water Bodies, Railways and Main Shafts," it can be seen that after adopting the precise protection technology of separation grouting, the maximum horizontal deformation value of the river channel does not exceed the allowable limit deformation value of the dam body. Therefore, the precise protection technology of separation grouting can ensure the normal use of the river channel while ensuring safe underground mining.

[0116] Based on the embodiments of the present invention, any modifications, equivalent substitutions, improvements, etc., made by all other embodiments obtained by those skilled in the art without creative effort should be included within the protection scope of the present invention.

Claims

1. A method for determining the grouting parameters for precise protection of surface targets within a mining area, characterized in that, Includes the following steps: S1. Based on the collected mining geological data, determine the structure and lithology of the overlying strata on the working face, and the strike and boundary angle of the working face. σ 0 Maximum subsidence angle of the working face θ Coal seam burial depth near surface protection target H 0 The characteristics of the surface protection targets and their relative positional relationship with the working face; S2. Determine the width of the maintenance zone for the surface protection targets based on their protection levels. l b ; S3. Based on the structure and lithology of the overlying strata on the working face, the water-conducting fracture zone and the stratigraphic position of the hard rock layer in the overlying strata are obtained. Finally, the stratigraphic position for overlying strata separation grouting is determined, and the height of the grouting position from the coal seam is obtained. H Z ; S4. Based on the orientation and boundary angle of the working face. σ 0 Determine the impact distance of the working face mining l c : ； In the formula, l c The influence distance of the working face mining is expressed in meters. H 0 The depth of coal seams near surface protection targets, in meters; σ 0 The working face's boundary angle, in degrees; S5. Based on the fracture angle of the overlying strata The distance from the working face when the rock strata fractures is obtained by considering the height of the grouting layer. ； In the formula, l p The distance of delayed fracture of the rock strata at the grouting site is expressed in meters. H Z This refers to the height of the grouting layer from the coal seam, in meters (m). The fracture angle of the overlying strata, in degrees; S6. Based on the grouting layer, obtain the location, lithology, and load-bearing characteristics of the adjacent hard rock layer below the grouting layer, and calculate the periodic fracture distance of the rock layer. l z ; S7. Based on the width of the maintenance zone of the surface protection target, the impact distance of the working face mining, the delayed fracture distance of the rock strata at the grouting layer, and the periodic fracture distance of the rock strata, the minimum distance between the boundary grouting borehole and the surface protection target is finally determined. l : ； In the formula, l The minimum distance between the boundary grouting borehole and the surface protection target, in meters; S8. Calculate the grouting pressure based on the borehole depth from the ground surface to the grouting layer, the comprehensive unit weight of the strata above the grouting layer, and the unit weight of the grouting fluid. P Z : ； In the formula, P Z This refers to the grouting pressure at the orifice, expressed in MPa. H g The depth of the borehole from the ground surface to the grouting filling layer is expressed in meters (m). γ The unit weight of the strata above the grouting filling layer is expressed in kN / m³. 3 ; γ 1 The density of the filling grout, expressed in kN / m³. 3 ; S9. Based on the maximum sinking angle of the working surface θ and the height of the grouting layer from the coal seam H Z The main subsidence section of the subsidence grouting layer was obtained. Due to the dip angle of the coal seam, the main subsidence section shifted from the center of the goaf in the downward direction. The distance of this downward shift from the center of the goaf was determined. d : ； In the formula, d The unit is the distance the main subsidence section is offset from the center of the goaf in the downward direction, in meters; H z This refers to the height of the grouting layer from the coal seam, in meters (m). θ The maximum downward angle of the working face, in degrees; S10. Based on the relative positional relationship between the surface protection target and the coal seam mining area, the distance between the boundary grouting borehole and the surface protection target, the grouting borehole pressure and the diffusion radius of the grout, the distance between the grouting boreholes is comprehensively determined to obtain the position of the separation grouting borehole on the main cross section of the subsidence direction.

2. The determining method according to claim 1, characterized in that, In step S1, the overburden lithology is determined using the overburden comprehensive evaluation coefficient. P X The evaluation and analysis were conducted, and the calculation method is as follows: ； In the formula, m i Overlying rock i The normal thickness of the layer, in meters; Q i Overlying rock i Layered lithology evaluation coefficient.

3. The determining method according to claim 1, characterized in that, In step S1, the orientation boundary angle of the working surface σ 0 Maximum subsidence angle of the working face θ The selection is based on the analysis parameters of the measured data of the mining area; for mining areas without measured data, the selection is based on the lithological conditions obtained in step S1.

4. The determining method according to claim 1, characterized in that, In step S2, when determining the width of the maintenance zone for the surface protection target, it is selected in accordance with the provisions of the "Specifications for Coal Pillar Retention and Coal Mining for Buildings, Water Bodies, Railways and Main Shafts".

5. The determining method according to claim 1, characterized in that, In step S3, when selecting the grouting layer, the height of the water-conducting fracture zone can be analyzed based on the measured data of the mining area. For mining areas without measured data, the selection can be made based on the lithological conditions obtained in step S1, according to empirical formulas.

6. The determining method according to claim 1, characterized in that, In step S3, when selecting the grouting layer, the calculation method for determining the hard rock layer in the overburden is as follows: ； ； In the formula: i Numbering of hard rock strata from bottom to top; q n ) i For the first i No. 1 hard rock layer bears the upper part n The load on the rock strata, in kPa; E Here is the elastic modulus of each rock layer, in MPa; h The thickness of each rock layer is given in meters (m). γ The unit weight of the strata above the grouting filling layer is expressed in kN / m³. 3 .

7. The determining method according to claim 1, characterized in that, In step S6, the periodic fracture distance of the rock strata is calculated as follows: ； In the formula: l z The periodic fracture distance of the rock strata is expressed in meters. h z The thickness of the rock strata at the grouting site is in meters (m). q z The load borne by the rock strata at the grouting site is expressed in MPa. R T The tensile strength of the rock strata in the grouting zone is expressed in MPa.

8. The determining method according to claim 1, characterized in that, In step S10, grouting boreholes are arranged on the sinking main cross-section of the grouting layer, and straight or inclined holes are used for delamination grouting.

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