A curtain grouting space and construction method suitable for composite roof of gob-side entry retention

Abstract

The present invention provides a curtain grouting space suitable for a composite roof retaining a gob-side entry. The curtain grouting space for the composite roof retaining a gob-side entry presents a confined space structure that is larger at the top and smaller at the bottom. The top surface of the curtain grouting space for the composite roof retaining a gob-side entry is the overlying rock stratum, and the four sides are the roof fracture-deficient zone on the side of the solid coal ridge to be mined, the gob-side grouting curtain, the front and rear side lateral grouting curtains for the composite roof retaining a gob-side entry, and a concrete stopper layer on the bottom surface of the composite roof. This curtain grouting space effectively prevents leakage of grouting slurry in the composite roof retaining a gob-side entry, significantly improving the grouting effect and overall strength of the composite roof, thereby ensuring the integrity, stability, and safety of the composite roof retaining a gob-side entry.

Description

Technical Field

[0001] The present invention relates to the field of mining engineering, and in particular to a curtain grouting space and a construction method suitable for a composite roof of a gob-side entry retention. Background Art

[0002] With the continuous improvement of coal mining methods and the advancement of mechanical equipment, gob-side entry retention has become one of the important scientific models and technological development directions for deep coal mining in my country. It is a key approach to achieving the co-mining of coal and gas in deep coal seams. It has rapidly developed in my country's coal industry and has been promoted and applied in many mining areas, occupying a prominent position. However, the deep gob-side entry retention mining model inevitably leads to a significant increase in the range and peak value of lateral bearing pressure in the stope, an intensification of the impact of mining, and aggravation of mine pressure. In addition, the wide distribution of soft rock in deep coal-bearing strata and the increase in roadway cross-sectional dimensions due to the construction and development of large-scale intensive mines have made it difficult or even impossible to adapt to the new deep mine mining production and production technical conditions and the development of the research focus on ensuring the safe and smooth operation of deep gob-side entry retention - roof deformation and failure control. This is especially true for gob-side entry retention under composite roofs, where composite roof collapse accidents account for a significant proportion and pose a serious threat to coal mine production safety.

[0003] In field engineering practice for gob-side entry retention under deep composite roof conditions, it was found that even after intense mining, the roof overburden, even with high-strength support, still developed cracks and was severely broken. Grouting was attempted at the construction site to reinforce the roof overburden, but grout leakage and slurry runaway at the edge of the goaf severely affected the grouting reinforcement of the gob-side entry composite roof. This resulted in poor density of the grouting consolidation body, making it difficult to form a complete load-bearing structure. This inability to effectively ensure the integrity, stability, and safety of the entry roof resulted in some mines failing to achieve the expected results or even failing to retain the entry, thus limiting its wider application in my country. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to solve the above problems, aiming to improve the grouting effect of the composite roof of the gob-side entry retention, ensure that the composite roof forms a solid and dense complete load-bearing structure, and safeguard the integrity, stability and safety of the composite roof of the gob-side entry retention. The present invention is achieved through the following technical solutions:

[0005] A curtain grouting space suitable for a composite roof of a goaf-retaining lane. The curtain grouting space of the composite roof of the goaf-retaining lane presents a closed space structure that is larger at the top and smaller at the bottom. The top surface of the curtain grouting space of the composite roof of the goaf-retaining lane is the overlying rock layer, and the four side surfaces are the roof crack underdevelopment area on the side of the solid coal ridge to be mined, the grouting curtain on the goaf side, the horizontal grouting curtains on the front and rear sides of the goaf-retaining lane, and the concrete stop-grouting layer on the surface of the bottom composite roof.

[0006] A curtain grouting space construction method suitable for composite roof of gob-side entry retention.

[0007] The first step is to spray grout the surrounding rock in the stable section of the gob-side entry retention to form a dense concrete stop layer on the surrounding rock surface;

[0008] The second step is to design the drilling parameters of the composite roof curtain for gob-side entry retention and carry out drilling construction;

[0009] The third step is to carry out curtain drilling and grouting construction of the composite roof along the goaf to form a curtain grouting space.

[0010] A curtain grouting space construction method suitable for gob-side entry retaining composite roof, the curtain drilling parameter setting of the gob-side entry retaining composite roof

[0011] Along the tunnel axis, on the composite roof 100-300 mm away from the filling wall, a row of multiple curtain drill holes A are arranged with a drill hole spacing of 800-1500 mm. The direction of the drill hole A is inclined 15°-30° toward the goaf.

[0012] The boreholes A are divided into multiple groups of equal number. Three boreholes B are arranged at the first borehole A in each group along the cross-sectional direction of the tunnel. Three boreholes B are arranged at the last borehole A in each group along the cross-sectional direction of the tunnel. The bottom spacing of the boreholes B is 800~1500mm. The diameters of boreholes A and boreholes B are both 32~48mm. The drilling depth L is greater than twice the thickness of the composite roof.

[0013] A further improvement of the present invention is that the construction sequence of composite roof curtain drilling and grouting is:

[0014] Grouting operations are performed one by one on the drill holes A arranged along the axis of the roadway on the composite roof to form a goaf side grouting curtain on the composite roof at the edge of the goaf;

[0015] Grouting operations are carried out on boreholes B one by one to form a transverse grouting curtain along the gob-side entry retention on the cross section of the composite roof.

[0016] A further improvement of the present invention is that, during the curtain drilling and grouting process, the effective grouting ranges of two adjacent curtain drilling holes have overlapping parts, which can ensure that the formed curtain does not have cavities and cracks, and ensure that the two ends of the side grouting curtain in the goaf are tightly connected to one end of the horizontal grouting curtain along the goaf, and the other end edge of the horizontal grouting curtain along the goaf is tightly connected to the roof crack-undeveloped area of ​​the solid coal seam to be mined.

[0017] A further improvement of the present invention is that the curtain grouting material is Marisan grouting material, and the volume ratio of Marisan resin and catalyst is 1:1 and the weight ratio is 1:1.17;

[0018] Grouting time: 10~20 minutes, curtain drilling grouting effective diffusion radius R=0.8m;

[0019] The calculation formula for the slurry injection volume of a single curtain drilling hole is:

[0020]

[0021] Where: Q 钻孔i — Curtain drilling grouting volume, m 3 ;

[0022] R —Effective diffusion radius of curtain drilling grouting, m;

[0023] L —Drilling depth of curtain, m;

[0024] η —Porosity percentage of rock mass;

[0025] β —Effective filling coefficient of slurry in rock cracks.

[0026] A further improvement of the present invention is that after the grouting construction of the first curtain grouting space of the composite roof of the gob-side entry retention is completed, the curtain grouting spaces of adjacent composite roofs can share the same cross section during construction.

[0027] A further improvement of the present invention is that the parameters of the concrete mortar are as follows: high-grade 425# cement is selected, the spray layer thickness is 70-100 mm, and the strength is C20; the material ratio is cement: yellow sand: gravel = 1:2:2, the water-cement ratio is 0.8-1.0, and the amount of the accelerator is 2.5-4% of the weight of the cement; and a concrete sprayer is used for construction.

[0028] A further improvement of the present invention is to design grouting parameters in the composite roof curtain grouting space and perform grouting construction.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. Grouting is carried out on the surrounding rock in the stable section of the goaf-retained tunnel, and a dense concrete stop layer of a certain thickness is formed on the surface of the surrounding rock, which can prevent the composite roof grouting slurry from leaking into the tunnel; the goaf-side grouting curtain of the curtain grouting space can prevent the composite roof grouting slurry from flowing into the goaf through the roof crack development area, and the horizontal grouting curtain along the goaf-retained tunnel can prevent the composite roof grouting slurry from flowing to other roof areas. In short, the curtain grouting space can effectively prevent the leakage of the broken composite roof grouting slurry, ensure the dense consolidation of the grouting of the fractured rock mass in the curtain grouting space, significantly improve the grouting effect and overall strength of the composite roof, and ensure the integrity, stability and safety of the roof of the goaf-retained tunnel.

[0031] 2. The curtain drilling grouting materials are selected with medium viscosity, good adhesion, excellent compressive resistance, high expansion rate, strong flexibility and small grouting diffusion radius. The price is relatively high but the usage is small. The grouting materials in the curtain grouting space are selected with low viscosity, large effective grouting diffusion radius and high consolidation strength. The price is low but the usage is large. The combination of the two can not only resist and adapt to the deformation and cracking of the composite roof of the goaf-retained tunnel caused by strong mining, achieve better top grouting effect, but also save the grouting cost of the composite roof of the goaf-retained tunnel.

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the plan of gob-side entry retention layout and composite roof curtain drilling;

[0034] Figure 2 yes Figure 1 Section II of the composite roof curtain drilling arrangement for the middle gob-side entry;

[0035] Figure 3 yes Figure 1 Cross-section of the composite roof of the middle gob-side entry retaining, curtain drilling arrangement II-II section;

[0036] Figure 4 This is a top view of the composite roof curtain grouting space along the gob-side entry retention;

[0037] Figure 5 yes Figure 4 Section III-III of the side grouting curtain in the goaf area of ​​the composite roof of the middle gob-side entry;

[0038] Figure 6 yes Figure 4 Section IV-IV of the horizontal grouting curtain of the gob-side entry retaining composite roof in the middle gob-side entry retaining;

[0039] Figure 7 It is a plan view of the arrangement of drilling holes in the curtain grouting space of the composite roof of the gob-side entry retention;

[0040] Figure 8 yes Figure 7 VV section of drilling arrangement in the curtain grouting space of composite roof in middle gob retaining entry;

[0041] Explanation of the accompanying symbols: 1. Solid coal seam; 2. Goaf-side tunnel; 3. Filling wall; 4. Goaf; 5. Filling area; 6. Sectional tunnel; 7. Mining area; 8. Coal mining face; 9. Borehole A; 10. Effective diffusion radius of grouting; 11. Side grouting curtain in the goaf; 12. Horizontal grouting curtain in the goaf-side tunnel; 13. Borehole B; 14. Grouting borehole in the curtain grouting space; 15. Composite roof; 16. Overlying rock strata; 17. Roof crack-undeveloped area of ​​the solid coal seam to be mined. DETAILED DESCRIPTION

[0042] like Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 As shown, a curtain grouting space suitable for a composite roof of a goaf-retaining lane is shown. The curtain grouting space of the composite roof of the goaf-retaining lane is a closed space structure with a larger upper portion and a smaller lower portion. The top surface of the curtain grouting space of the composite roof of the goaf-retaining lane is the overlying rock layer 16, and the four side surfaces are respectively the roof crack underdeveloped area 17 on the side of the solid coal seam to be mined, the goaf side grouting curtain 11, the front and rear side transverse grouting curtains 12 along the goaf-retaining lane, and the concrete stop-grouting layer on the surface of the bottom composite roof.

[0043] Specifically, grouting is carried out on the surrounding rock in the stable section of the goaf-retained tunnel, and a dense concrete grouting layer of a certain thickness is formed on the surface of the surrounding rock, which can prevent the composite roof grouting slurry from leaking into the tunnel; the goaf-side grouting curtain of the curtain grouting space can prevent the composite roof grouting slurry from flowing through the roof crack development area to the goaf area 4, and the transverse grouting curtain along the goaf-retained tunnel can prevent the composite roof grouting slurry from flowing to other roof areas. In short, the curtain grouting space can effectively prevent the leakage of the roof grouting slurry, ensure the dense consolidation of the grouting of the fractured rock mass in the curtain grouting space, significantly improve the grouting effect and overall strength of the composite roof, and ensure the integrity, stability and safety of the roof of the goaf-retained tunnel.

[0044] Combined with the specific implementation method, the curtain grouting space construction method of the composite roof of the gob-side entry is further explained.

[0045] The first step is to spray grout the surrounding rock in the stable section of the gob-side entry retention to form a dense concrete stop layer on the surrounding rock surface;

[0046] Specifically, the surrounding rock of the gob-side entry retention is sealed with shotcrete. To improve the effectiveness of the composite roof grouting for the gob-side entry retention and prevent grout leakage during grouting, concrete mortar is sprayed onto the surrounding rock within the stable section of the gob-side entry retention, forming a dense stop layer of a certain thickness. The concrete mortar parameters are as follows: high-grade 425# cement is used, the spray layer thickness is 70-100mm, and the strength is C20. The material ratio is cement: yellow sand: gravel = 1:2:2, the water-cement ratio is 0.8-1.0, and the accelerator dosage is 2.5-4% of the cement weight. A concrete sprayer is used for construction.

[0047] The second step is to design the drilling parameters of the composite roof curtain for gob-side entry retention and carry out drilling construction;

[0048] Here’s how: Along the tunnel axis, on the composite roof 100-300 mm away from the filling wall, a row of multiple curtain drill holes A9 are arranged with a drill hole spacing of 800-1500 mm. The direction of the drill hole A9 is inclined 15°-30° toward the side of the goaf 4.

[0049] The boreholes A9 are divided into multiple groups of equal number. Three boreholes B are arranged at the first borehole A in each group along the cross-sectional direction of the tunnel. Three boreholes B are arranged at the last borehole A in each group along the cross-sectional direction of the tunnel. The bottom spacing of the boreholes B is 800~1500mm. The diameters of boreholes A9 and borehole B13 are both 32~48mm. The drilling depth L is greater than twice the thickness of the composite roof.

[0050] Specifically, a row of ten curtain drill holes (A) were arranged along the roadway axis, 200 mm from the backfill wall, with a spacing of 1200 mm between the drill holes and an inclination of 15° to 30° toward goaf 4. The drill holes were numbered 1# to 10 as the first group. Then, along the roadway cross section, a second group of three drill holes (B)—numbered 11#, 12#, and 13#—were arranged in the roof cross section at drill hole 1. A third group of three drill holes (B)—numbered 14#, 15#, and 16#—were arranged in the roof cross section at drill hole 10. The drill holes were spaced 1000 mm apart and inclined at an angle of 15° to 30° to ensure uniform placement of the curtain drill holes. Curtain drill holes A and B had identical parameters: a diameter of 32 to 48 mm, and a depth (L) determined by twice the thickness of the composite roof. The drilling process can be performed using a ZQJJ120 / 2.3 column-supported drilling rig. After each curtain grouting drill is completed, a grouting tube is immediately installed to prevent blockage caused by hole collapse. The grouting tube has a diameter of 25-40mm and a length of L. A 350mm-long hole sealer is then placed over the end of the grouting tube and inserted 400mm into the curtain drill hole to seal the drill hole and prevent grout leakage.

[0051] The third step is to carry out curtain drilling and grouting construction of composite roof along the goaf to form curtain grouting space. The construction sequence of composite roof curtain drilling and grouting is as follows:

[0052] Grouting operations are performed one by one on the drill holes A set along the axis of the roadway on the composite roof to form a goaf side grouting curtain on the composite roof at the edge of the goaf 4;

[0053] Grouting operations are carried out on boreholes B one by one to form a transverse grouting curtain along the gob-side entry retention on the cross section of the composite roof.

[0054] During curtain drilling and grouting, the effective grouting ranges of two adjacent curtain boreholes overlap, ensuring that the resulting curtain is free of cavities and cracks. This ensures that both ends of the gob-side grouting curtain are tightly connected to one end of the horizontal grouting curtain along the gob-retaining entry, and that the edges of the horizontal grouting curtain along the gob-retaining entry are closely connected to the crack-free zone of the roof of the solid coal slab to be mined. After grouting is completed in the first curtain grouting space of the composite roof along the gob-retaining entry, the curtain grouting spaces of adjacent composite roofs can share the same cross-section.

[0055] Specifically, first, grouting operations were carried out one by one on the 1#~10# curtain boreholes A of the first group of composite roof to form the first curtain on the roof at the edge of goaf 4; then, grouting operations were carried out one by one on the 11#~13# curtain boreholes B of the second group to form the second curtain on the cross section of the roof; finally, grouting operations were carried out one by one on the 14#~16# curtain boreholes B of the third group to form the third curtain on the cross section of the roof.

[0056] It is important to note that the curtain drilling and grouting operation requires that during the curtain drilling and grouting process, the effective grouting ranges of the two adjacent curtain drilling holes overlap to a certain extent, ensuring that the formed curtain does not have cavities and cracks, and that the two ends of the first curtain are tightly connected to one end of the second and third curtains, respectively, and the other ends of the second and third curtains are tightly connected to the undeveloped areas of the roof cracks.

[0057] This creates a closed, trapezoidal-shaped grouting space on the upper portion of the composite roof of the gob-side entryway retention system. Its bottom surface is the concrete stop layer on the composite roof surface, three sides are grouting curtains, one side is the area where roof cracks are not developed, and the top is the overlying rock strata. This curtain grouting space prevents grouting slurry from leaking into the gob-side entryway retention composite roof, into the goaf, into the roadway, and other directions, ensuring the effectiveness of the composite roof grouting.

[0058] In addition, after the grouting construction of the first curtain grouting space of the composite roof of the gob-side tunnel is completed, when constructing the curtain grouting space of the adjacent composite roof, it is not necessary to construct the second curtain, only the first and third curtains are required.

[0059] Preferably, the curtain grouting material of the composite roof is required to have the following properties: Medium viscosity, able to penetrate into smaller rock cracks; Better bonding ability, forming stronger bonds with rock formations; Good flexibility, able to withstand the impact of subsequent strong mining on the working face; Good compressive performance; The expansion rate is high, reaching 5 to 10 times the original volume; It reacts quickly to water in fissures, and reacts within a dozen seconds after coming into contact with water, and can quickly block the water flow.

[0060] Taking Marisan grouting material as an example, the grouting parameters are: Marisan resin and catalyst ratio, volume ratio is 1:1, weight ratio is 1:1.17; grouting time: 10~20 minutes, curtain drilling grouting effective diffusion radius R=0.8m. The calculation formula for the slurry injection volume of a single curtain drilling hole is:

[0061]

[0062] Where: Q 钻孔i — Curtain drilling grouting volume, m 3 ; R —Effective diffusion radius of curtain drilling grouting, m; L —Drilling depth of curtain, m; η —Porosity of rock mass, %; β —Effective filling coefficient of slurry in rock cracks.

[0063] The process flow of Marisan grouting: Assemble the multi-functional grouting pump and its accessories and fix the injection gun → connect the high-pressure pipe on the injection gun to the tail end of the drilling grouting flower pipe → insert two straws into the barrel filled with Marisan resin and catalyst → start the pump for grouting → stop grouting → flush the equipment (flush the pipeline and mixing gun with resin) → change the hole for grouting (repeat the previous steps) → grouting is completed and stop the pump → clean the multi-functional pump and accessories with cleaning agent and disassemble the injection gun - grouting is completed.

[0064] The fourth step is to design the grouting parameters in the composite roof curtain grouting space and carry out grouting construction.

[0065] Generally, 2 to 4 grouting holes are arranged in each row on the concrete stop layer at the bottom of the curtain grouting space of the composite roof, with a row spacing of 1500 to 2000 mm, a drilling inclination of 10 to 30 degrees, a drilling diameter of 32 to 48 mm, and a drilling depth L determined based on twice the thickness of the composite roof.

[0066] Drilling was performed using a ZQJJ120 / 2.3 column-supported drilling rig. After each grouting hole was completed, a grouting tube was immediately installed to prevent blockage caused by hole collapse. The grouting tube had a diameter of 25-40 mm and a length of L. A 350 mm long hole sealer was then inserted into the end of the grouting tube and inserted 400 mm into the grouting hole to seal the hole and prevent leakage.

[0067] The grouting material used in the curtain grouting space should have low viscosity, high consolidation strength, and a large effective diffusion radius. Taking ultrafine cement grouting as an example, the grouting parameters are: high-grade 425# cement, a slurry water-cement ratio of 1:2, and ACZ-I grouting additive at 8% of the cement volume. Its main functions are water reduction, plasticization, reinforcement, and micro-expansion, overcoming the current problems of cement slurries with high water-cement ratios, low strength, hardening shrinkage, and high pumping resistance.

[0068] Grouting equipment operation process: Connect the grouting pipe of the grouting equipment to the grouting connector at the end of the grouting pipe, start the equipment and begin grouting. When the grouting volume in each borehole reaches the set value, the grouting of each borehole is completed. Then, grouting is carried out one by one according to the grouting sequence until all boreholes are grouted.

[0069] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

Claims

1. A curtain grouting space construction method suitable for composite roof of gob-side entry retention, characterized in that: The curtain grouting space of the composite roof of the gob-side entry retaining is a closed space structure with a larger top and a smaller bottom. The top surface of the curtain grouting space of the composite roof of the gob-side entry retaining is the overlying rock layer, and the four sides are the roof crack undeveloped area on the side of the solid coal seam to be mined, the grouting curtain on the gob area side, the horizontal grouting curtains on the front and rear sides of the gob-side entry retaining, and the concrete stop layer on the surface of the bottom composite roof. Construction methods, The first step is to spray grout the surrounding rock in the stable section of the gob-side entry retention to form a dense concrete stop layer on the surrounding rock surface; The second step is to design the curtain drilling parameters of the composite roof of the gob-side entry retention. The curtain drilling parameters of the composite roof of the gob-side entry retention are set as follows: along the roadway axis, on the composite roof 100~300mm away from the filling wall, a row of multiple curtain boreholes A are arranged, with a borehole spacing of 800~1500mm, and the direction of the borehole A is inclined 15°~30° toward the side of the goaf. The boreholes A are divided into multiple groups of equal number, and three boreholes B are arranged along the cross-section direction of the roadway at the first borehole A of each group, and three boreholes B are arranged along the cross-section direction of the roadway at the last borehole A of each group. The bottom spacing of the boreholes B is 800~1500mm, the diameters of the boreholes A and B are both 32~48mm, and the drilling depth L is greater than 2 times the thickness of the composite roof. Drilling construction is carried out; The third step is to carry out curtain drilling and grouting of the composite roof along the gob-side entry retention. The construction sequence is to grout the boreholes A set along the roadway axis on the composite roof one by one, forming a gob-side grouting curtain on the composite roof at the edge of the gob. Then, grouting is carried out one by one on the boreholes B, forming a transverse grouting curtain along the gob-side entry retention on the cross section of the composite roof, thus forming a curtain grouting space. Among them, during the curtain drilling and grouting process, the effective grouting ranges of the two adjacent curtain drilling holes have overlapping parts, which can ensure that the formed curtain does not have cavities and cracks, and ensure that the two ends of the side grouting curtain in the goaf are tightly connected with one end of the horizontal grouting curtain along the goaf, and the edge of the horizontal grouting curtain along the goaf is tightly connected with the roof crack-undeveloped area of ​​the solid coal seam to be mined.

2. The curtain grouting space construction method for composite roof of gob-side entry retention according to claim 1, characterized in that: The curtain grouting material is Marisan grouting material, with a volume ratio of Marisan resin and catalyst of 1:1 and a weight ratio of 1:1.

17. The grouting time is 10-20 minutes, and the effective diffusion radius of the curtain drilling grouting is R = 0.8m. The calculation formula for the slurry injection volume of a single curtain drilling hole is: , QDrilling i — Curtain drilling grouting volume, m 3 ; R —Effective diffusion radius of curtain drilling grouting, m; L —Drilling depth of curtain, m; η —Porosity percentage of rock mass; β —Effective filling coefficient of slurry in rock cracks.

3. The curtain grouting space construction method for composite roof of gob-side entry retention according to claim 1 is characterized in that: After the grouting construction of the first curtain grouting space of the composite roof of the gob-side entry is completed, the curtain grouting space of the adjacent composite roof can share the same cross-section during construction.

4. The curtain grouting space construction method for composite roof of gob-side entry retention according to claim 1 is characterized in that: The concrete mortar parameters are as follows: high-grade 425# cement is used, the spray layer thickness is 70~100mm, and the strength is C20; the material ratio is cement: yellow sand: gravel = 1:2:2, the water-cement ratio is 0.8~1.0, and the amount of accelerator is 2.5~4% of the cement weight; a concrete sprayer is used for construction.

5. The curtain grouting space construction method for composite roof of gob-side entry retention according to claim 1 is characterized in that: Design the grouting parameters in the composite roof curtain grouting space and carry out grouting construction.

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