Layer position positioning method for separation grouting of large buried depth coal seam

Abstract

The present application discloses a large buried depth coal seam delamination grouting horizon positioning method, characterized in that it comprises the following steps: step 1, collecting delamination grouting working face information and collecting different lithology cores of different strata for rock mechanics test, respectively as a basic data set and an operation data set; step 2, judging the key layer horizon based on the basic data set and the operation data set, and calculating the deflection w of the rock plate through the thin plate theory on the Winkler elastic foundation; step 3, calculating the delamination horizon and its opening degree based on the deflection w of the rock plate, and dividing the grade of the delamination space; step 4, judging the relationship between the key layer horizon and the grade of the delamination space, and determining the best horizon of the delamination grouting. The present application can reliably determine the appropriate delamination grouting horizon, effectively preventing the occurrence of delamination water damage.

Description

Technical Field

[0001] This invention belongs to the field of mine water hazard prevention and control technology, specifically relating to a method for locating the separation grouting layer in deep coal seams. Background Technology

[0002] Deep coal seam mining alters the original stress conditions of the overlying strata, accompanied by deformation and damage. During mining operations, the overlying strata continuously collapse and deform due to mining activity, and fissures gradually develop upwards, including horizontal and vertical fissures. The vertical fissures interconnect to form water-conducting fracture zones, which can guide water from the upper aquifer to the working face. Delamination can be considered a large horizontal fissure caused by differences in lithology and mechanical properties between the upper and lower strata. The fundamental cause of delamination water hazards lies in the fact that fissures below the delamination penetrate the protective layer, guiding water from the delamination space to the working face. To prevent delamination water hazards, delamination grouting can be used. During the delamination formation process, grout is used to fill the delamination space, reducing the volume of water-bearing space and thus preventing delamination water.

[0003] The primary challenge in current delamination grouting methods lies in determining the location and size of the delamination layer and designing a suitable grouting scheme accordingly. Currently, the prediction of delamination grouting layers often relies on the "composite beam" theory to identify key layers. However, multiple key layers exist within the overburden, and the size of the delamination space beneath these layers remains unclear, making the selection of grouting layers a significant challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a method for locating the grouting layer in deep coal seams, which can reliably determine the appropriate grouting layer and effectively prevent the occurrence of water damage caused by delamination.

[0005] The technical solution adopted in this invention is a method for locating the separation grouting layer in deep coal seams, comprising the following steps:

[0006] Step 1: Collect information on the delamination grouting working face and collect rock cores of different lithologies from different strata for rock mechanics testing, which will serve as the basic dataset and the computational dataset, respectively.

[0007] Step 2: Determine the key layer position based on the basic dataset and the computational dataset, and calculate the deflection w of the rock slab using the thin plate theory on the Winkler elastic foundation;

[0008] Step 3: Based on the deflection w of the rock slab, calculate the delamination horizon and its opening, and classify the delamination space into levels;

[0009] Step 4: Determine the relationship between the key layer level and the separation space level to determine the optimal layer for separation grouting.

[0010] The invention is further characterized in that,

[0011] In step 1, the information of the grouting working face is the formation thickness h of the grouting working face and the surrounding boreholes. The formation thickness h is recorded to form the basic dataset.

[0012] The unit weight r, elastic modulus E, and Poisson's ratio v of rock cores of different lithologies in different strata were obtained through rock mechanics tests in step 1. The unit weight r, elastic modulus E, and Poisson's ratio v were recorded to form a computational dataset.

[0013] In step 2, the critical layer is determined using the following formula:

[0014] (q i+1 )1<(q i )1

[0015] Where i represents any rock layer above the top boundary of the water-conducting fracture zone, and when the formula holds true, the i-th layer is the key layer.

[0016] Where (q) i )1. The specific formula is shown below:

[0017]

[0018] Where E is the elastic modulus, h is the formation thickness, and r is the unit weight.

[0019] The deflection w of the rock slab is shown in the following formula:

[0020]

[0021] Where w is the deflection of the rock slab in meters (m); q0 is the upper load on the rock slab in MPa; a is the strike length of the rock slab in meters; L0 is the advance of the working face in meters; b is the dip length of the rock slab in meters; b1 is the dip length of the working face in meters; v is Poisson's ratio; k is the elastic foundation coefficient; and D is the bending stiffness of the rock slab.

[0022] The strike length 'a' of the rock slab is given by the following formula:

[0023]

[0024] Where L0 is the advance of the working face in meters; H is the distance between the coal seam roof and the rock slab in meters; and θ is the rock stratum fracture angle.

[0025] The dip length b of the rock slab is given by the following formula:

[0026]

[0027] Where b1 is the dip length of the working face, in meters; H is the distance between the coal seam roof and the rock slab, in meters; and θ is the rock strata fracture angle.

[0028] The elastic subgrade coefficient k is shown in the following formula:

[0029]

[0030] Where E is the elastic modulus; h is the stratum thickness; i is the current stratum number; and m is the number of strata between the coal seam roof and the rock slab.

[0031] The bending stiffness D of the slab is shown in the following formula:

[0032]

[0033] Where E is the elastic modulus; h is the formation thickness; and v is Poisson's ratio.

[0034] Step 3 shows the calculation of the delamination horizon and its opening, and the delamination space is divided into levels, specifically numbered 1 to i from the top boundary of the water-conducting fracture zone upwards. The ratio Z of the deflection of the i-th rock layer to that of the (i-1)-th rock layer is shown in the following formula:

[0035] Z = w i / w i-1

[0036] When Z≥1, the i-th layer and the (i-1)-th layer will not separate; when Z<1, the i-th layer and the (i-1)-th layer will separate.

[0037] Delamination H n As shown in the following formula:

[0038] H n =w n-1 -w n

[0039] Where n is the number of key rock plates;

[0040] Based on the opening degree H of the delamination n The separation layer is divided into three levels, when H n When the depth is ≤0.1m, the separation level is III; when 0.1 <H n When ≤0.5m, the separation level is II; when H n When the depth is greater than 0.5m, the separation level is I.

[0041] In step 4, determining the relationship between the key layer and the separation space level specifically involves determining whether the key layer coincides with the Class I separation. If they coincide, then the key layer is the optimal layer for separation grouting.

[0042] The beneficial effects of this invention are that the method for locating the grouting layer in deep coal seams uses the surrounding borehole stratigraphic data as the basic dataset and the mechanical test results of different lithologies as the calculation dataset. Based on the "composite beam" theory and combined with the thin plate theory on Winkler's elastic foundation, the method calculates the layer position and opening of the grouting space and classifies the grouting space. When the key layer position of the "composite beam" theory coincides with the Class I grouting layer, it can be determined that the layer position is the optimal layer position for grouting, providing a more accurate layer position selection for grouting projects and effectively preventing the occurrence of grouting water hazards. Attached Figure Description

[0043] Figure 1 This is a flowchart illustrating the method for locating the separation grouting layer in deep coal seams according to the present invention.

[0044] Figure 2 This is a schematic diagram of the separation level determination process in the separation grouting layer location method for deep coal seams of the present invention;

[0045] Figure 3 This is a data comparison chart of the identification of key layers and the spatial classification of delamination in Example 3;

[0046] Figure 4 This is a schematic diagram of the deflection curve of the key rock slab in Example 3;

[0047] Figure 5 This is a schematic diagram of the deflection curve of the key rock slab in Example 3;

[0048] Figure 6 This is a comparison chart of the accuracy verification data of the delamination grouting layer determined through Example 3. Detailed Implementation

[0049] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0050] Example 1

[0051] like Figure 1 As shown, the method for locating the separation grouting layer in deep coal seams disclosed in this invention includes the following steps:

[0052] Step 1: Collect the formation thickness h of the grouting working face and surrounding boreholes, and record the formation thickness h to form a basic dataset; then collect rock cores of different lithologies from different strata for rock mechanics testing, and obtain the unit weight r, elastic modulus E and Poisson's ratio v of the rock cores of different lithologies from different strata, and record the unit weight r, elastic modulus E and Poisson's ratio v to form a computational dataset.

[0053] Step 2: Determine the key layer position based on the basic dataset and the computational dataset. The key layer position is determined using the following formula:

[0054] (q i+1 )1<(q i )1

[0055] Where i represents any rock layer above the top boundary of the water-conducting fracture zone, and when the formula holds true, the i-th layer is the key layer.

[0056] Where (q) i )1. The specific formula is shown below:

[0057]

[0058] Where E is the elastic modulus, h is the formation thickness, and r is the unit weight.

[0059] The deflection w of the rock slab was calculated using Winkler's thin-plate theory on elastic foundations, as shown in the following formula:

[0060]

[0061] Where w is the deflection of the rock slab in meters (m); q0 is the upper load on the rock slab in MPa; a is the strike length of the rock slab in meters; L0 is the advance of the working face in meters; b is the dip length of the rock slab in meters; b1 is the dip length of the working face in meters; v is Poisson's ratio; k is the elastic foundation coefficient; and D is the bending stiffness of the rock slab.

[0062] The Winkler elastic foundation is a model theory concept proposed by Czech engineer E. Winkler in 1876.

[0063] Step 3: Based on the deflection w of the rock slab, calculate the delamination layer and its opening. Specifically, starting from the top boundary of the water-conducting fracture zone, number the layers from 1 to i upwards. The ratio Z of the deflection of the i-th rock slab to that of the (i-1)-th rock slab is shown in the following formula:

[0064] Z = w i / w i-1

[0065] When Z≥1, the i-th layer and the (i-1)-th layer will not separate; when Z<1, the i-th layer and the (i-1)-th layer will separate.

[0066] Delamination H n As shown in the following formula:

[0067] H n =w n-1 -w n

[0068] Where n is the number of key rock plates;

[0069] Then, the hierarchy of the separation space is divided into three levels: I, II, and III;

[0070] Step 4: Determine the relationship between the key layer and the separation space level. When the key layer coincides with the Class I separation, the key layer is determined to be the optimal layer for separation grouting.

[0071] Example 2

[0072] The method for locating the separation grouting layer in deep coal seams disclosed in this invention includes the following steps:

[0073] Step 1: Collect the formation thickness h of the grouting working face and surrounding boreholes, and record the formation thickness h to form a basic dataset; then collect rock cores of different lithologies from different strata for rock mechanics testing, and obtain the unit weight r, elastic modulus E and Poisson's ratio v of the rock cores of different lithologies from different strata, and record the unit weight r, elastic modulus E and Poisson's ratio v to form a computational dataset.

[0074] Step 2: Determine the key layer position based on the basic dataset and the computational dataset. The key layer position is determined using the following formula:

[0075] (q i+1 )1<(q i )1

[0076] Where i represents any rock layer above the top boundary of the water-conducting fracture zone, and when the formula holds true, the i-th layer is the key layer.

[0077] Where (q) i )1. The specific formula is shown below:

[0078]

[0079] Where E is the elastic modulus, h is the formation thickness, and r is the unit weight.

[0080] The deflection w of the rock slab was calculated using Winkler's thin-plate theory on an elastic foundation, as shown in the following formula:

[0081]

[0082] Where w is the deflection of the rock slab in meters (m); q0 is the upper load on the rock slab in MPa; a is the strike length of the rock slab in meters; L0 is the advance of the working face in meters; b is the dip length of the rock slab in meters; b1 is the dip length of the working face in meters; v is Poisson's ratio; k is the elastic foundation coefficient; and D is the bending stiffness of the rock slab.

[0083] The strike length 'a' of the rock slab is given by the following formula:

[0084]

[0085] Where L0 is the advance of the working face in meters; H is the distance between the coal seam roof and the rock slab in meters; and θ is the rock stratum fracture angle.

[0086] The dip length b of the rock slab is given by the following formula:

[0087]

[0088] Where b1 is the dip length of the working face, in meters; H is the distance between the coal seam roof and the rock slab, in meters; and θ is the rock strata fracture angle.

[0089] The elastic subgrade coefficient k is shown in the following formula:

[0090]

[0091] Where E is the elastic modulus; h is the stratum thickness; i is the current stratum number; and m is the number of strata between the coal seam roof and the rock slab.

[0092] The bending stiffness D of the slab is shown in the following formula:

[0093]

[0094] Where E is the elastic modulus; h is the formation thickness; and v is Poisson's ratio.

[0095] Step 3: Based on the deflection w of the rock slab, calculate the delamination layer and its opening. Specifically, starting from the top boundary of the water-conducting fracture zone, number the layers from 1 to i upwards. The ratio Z of the deflection of the i-th rock slab to that of the (i-1)-th rock slab is shown in the following formula:

[0096] Z = w i / w i-1

[0097] When Z≥1, the i-th layer and the (i-1)-th layer will not separate; when Z<1, the i-th layer and the (i-1)-th layer will separate.

[0098] Delamination H n As shown in the following formula:

[0099] H n =w n-1 -w n

[0100] Where n is the number of key rock plates;

[0101] Based on the opening degree H of the delamination n The separation layer is divided into three levels, when H nWhen the delamination depth is ≤0.1m, the delamination level is III, meaning the delamination opening is very small and will not exist stably during overburden movement; this is an unstable delamination. When 0.1 < H n When the depth is ≤0.5m, the delamination grade is II, meaning the delamination opening is moderate and can persist for a relatively long time during overburden movement; when H n When the depth is greater than 0.5m, the delamination level is I, which means that the delamination opening is relatively large and can exist for a long time during the overburden movement.

[0102] Step 4: Determine the relationship between the key layer and the separation space level. When the key layer coincides with the Class I separation, the key layer is determined to be the optimal layer for separation grouting.

[0103] Example 3

[0104] This embodiment uses geological and mechanical parameter data from a mine in Inner Mongolia and Shaanxi provinces for calculation, specifically including the following steps:

[0105] Step 1: Collect the formation thickness h of the grouting working face and surrounding boreholes, and record the formation thickness h to form a basic dataset, as shown in Table 1 below;

[0106]

[0107]

[0108] Then, rock mechanics tests were conducted on rock cores of different lithologies from different strata to obtain the unit weight r, elastic modulus E, and Poisson's ratio v of the rock cores of different lithologies from different strata. The unit weight r, elastic modulus E, and Poisson's ratio v were recorded to form a computational dataset, as shown in Table 2 below.

[0109]

[0110] like Figures 3-5 As shown, in step 2, the key layer position is determined based on the basic dataset and the computational dataset. The calculation results show that a total of four key layers are developed above the water-conducting fracture zone. Since the separation space below the key layer is unclear, it is still difficult to select which layer as the grouting layer position.

[0111] Then, using Winkler's thin-plate theory on elastic foundations, the deflection w of the rock slab was calculated.

[0112] Step 3: Based on the deflection w of the rock slab, calculate the delamination layer and its opening. Specifically, starting from the top boundary of the water-conducting fracture zone, number the layers from 1 to i upwards. The ratio Z of the deflection of the i-th rock slab to that of the (i-1)-th rock slab is shown in the following formula:

[0113] Z = w i / w i-1

[0114] When Z≥1, the i-th layer and the (i-1)-th layer will not separate; when Z<1, the i-th layer and the (i-1)-th layer will separate.

[0115] Delamination H n As shown in the following formula:

[0116] H n =w n-1 -w n

[0117] Where n is the number of key rock plates; and the delamination space is classified.

[0118] Step 4: Determine the relationship between the key layer and the separation space level. When the key layer coincides with the Class I separation, the key layer is determined to be the optimal layer for separation grouting.

[0119] pass Figure 3 It can be seen that the No. 14 sandstone is a key layer in the "composite beam" theory. The calculation results in the thin plate theory on Winkler elastic foundation show that it forms a Class I delamination with the No. 15 sandy mudstone below it, and the delamination opening is the largest. Therefore, No. 14 is the best choice for the delamination grouting layer.

[0120] like Figure 6 As shown, the accuracy of the grouting layer determination results in Example 3 was verified. Based on the flushing fluid consumption of the grouting holes on the working surface and the borehole television observation results, the theoretical prediction of the delamination showed good consistency with the actual measurement. Delamination spaces were developed in both the Anding Formation and the Zhidan Group above the water-conducting fracture zone. In the Zhidan Group, the delamination mainly developed in the middle and lower sections. When the key layer coincided with the first-order delamination development layer, the probability and space of the delamination space were relatively large. In this case, flushing fluid leakage occurred in most boreholes, and large fractures were also found on the borehole color television.

[0121] In summary, the positioning method of the present invention can accurately locate the optimal layer for delamination grouting, further improving the accuracy of delamination grouting layer selection, and also has important reference value for establishing other delamination grouting layer selection models.

Claims

1. A method for locating the separation grouting layer in deep coal seams, characterized in that, Includes the following steps: Step 1: Collect information on the delamination grouting working face and collect rock cores of different lithologies from different strata for rock mechanics testing, which will serve as the basic dataset and the computational dataset, respectively. Step 2: Determine the key layer position based on the basic dataset and the computational dataset, and calculate the deflection w of the rock slab using the thin plate theory on the Winkler elastic foundation; Step 3: Based on the deflection w of the rock slab, calculate the delamination horizon and its opening, and classify the delamination space into levels; Step 4: Determine the relationship between the key layer and the separation space level to determine the optimal layer for separation grouting; Step 3 shows the calculation of the delamination horizon and its opening, and the delamination space is divided into levels, specifically numbered 1 to i from the top boundary of the water-conducting fracture zone upwards. The ratio Z of the deflection of the i-th rock layer to that of the (i-1)-th rock layer is shown in the following formula: With=in i / In i-1 When Z≥1, the i-th layer and the (i-1)-th layer will not separate; when Z<1, the i-th layer and the (i-1)-th layer will separate. Delamination H n As shown in the following formula: Where n is the number of key rock plates; Based on the opening degree H of the delamination n The separation layer is divided into three levels, when H n When the depth is ≤0.1m, the separation level is III; when 0.1 <H n When ≤0.5m, the separation level is II; when H n When the depth is greater than 0.5m, the separation level is I; In step 4, determining the relationship between the key layer and the separation space level specifically involves determining whether the key layer coincides with the Class I separation. If they coincide, then the key layer is the optimal layer for separation grouting.

2. The method for locating the separation grouting layer in deep coal seams according to claim 1, characterized in that, The information on the grouting working face mentioned in step 1 is the formation thickness h of the grouting working face and the surrounding boreholes. The formation thickness h is recorded to form a basic dataset.

3. The method for locating the separation grouting layer in deep coal seams according to claim 1, characterized in that, The unit weight r, elastic modulus E, and Poisson's ratio v of rock cores of different lithologies in different strata are obtained through the rock mechanics test described in step 1. The unit weight r, elastic modulus E, and Poisson's ratio v are recorded to form a computational dataset.

4. The method for locating the separation grouting layer in deep coal seams according to claim 1, characterized in that, In step 2, the key layer position is determined using the following formula: Where i represents any rock layer above the top boundary of the water-conducting fracture zone, and when the formula holds true, the i-th layer is the key layer. Where (q) i 1. The specific formula is shown below: Where E is the elastic modulus, h is the formation thickness, and r is the unit weight.

5. The method for locating the separation grouting layer in deep coal seams according to claim 1, characterized in that, The deflection w of the rock slab is shown in the following formula: Where w is the deflection of the rock slab in meters (m); q0 is the upper load on the rock slab in MPa; a is the strike length of the rock slab in meters; L0 is the advance of the working face in meters; b is the dip length of the rock slab in meters; b1 is the dip length of the working face in meters; v is Poisson's ratio; k is the elastic foundation coefficient; and D is the bending stiffness of the rock slab.

6. The method for locating the separation grouting layer in deep coal seams according to claim 5, characterized in that, The strike length 'a' of the rock slab is shown in the following formula: ； Where L0 is the advance of the working face in meters; H is the distance between the coal seam roof and the rock slab in meters; and θ is the rock stratum fracture angle. The dip length b of the rock slab is shown in the following formula: Where b1 is the dip length of the working face, in meters; H is the distance between the coal seam roof and the rock slab, in meters; and θ is the rock strata fracture angle. The elastic foundation coefficient k is shown in the following formula: Where E is the elastic modulus; h is the stratum thickness; i is the current stratum number; and m is the number of strata between the coal seam roof and the rock slab. The bending stiffness D of the rock slab is shown in the following formula: Where E is the elastic modulus; h is the formation thickness; and v is Poisson's ratio.

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