CN220621952U - Mined overburden composite curtain to improve overburden separation layer grouting effect - Google Patents

Abstract

The utility model discloses a mining overburden composite curtain for improving overburden separation grouting effect, which comprises a plurality of layers of hard rock layers, wherein the layers of hard rock layers are provided with cracks or geological structure weaknesses before mining of a working face coal seam, and separation layers are formed after mining of the working face coal seam; the rock layer section with the separation layers is called a multi-separation layer grouting section, and the rock layer section without the separation layers is called a bedrock reinforcement section; before mining the coal seam of the working face, injecting cement slurry into the cracks or the weak face of the geological structure to solidify and form a curtain layer; the curtain layers of the multi-separation-layer grouting section form an isolation curtain to prevent the fly ash slurry injected in the separation layer space from flowing to the goaf of the adjacent working face; the curtain layer of the bedrock reinforcement section forms a protective curtain to prevent the pulverized fuel ash slurry injected into the separation layer space from being conducted to the ground along cracks or weak surfaces. The utility model has strong adaptability to geological and stratum conditions, high grouting efficiency of the overlying strata separation layer and good grouting and sinking reducing effects.

Description

Mined overburden composite curtain to improve overburden separation layer grouting effect

Technical field

The utility model relates to the technical field of coal mine filling and mining, specifically a mining overburden composite curtain that improves the overburden separation layer grouting effect.

Background technique

Large-scale mining of coal resources has caused overlying rock damage and separation layer development, which has been transmitted to the surface as surface subsidence and crack development, directly causing damage to surface buildings (structures), water bodies, railways, etc. As the mine enters the later stage of mining, recovering the coal pillar resources left behind due to the impact of mining layout, geological structure and "three lower" coal pressure has become an effective way to improve the coal resource recovery rate and achieve green and sustainable development of the mine.

Usually coal pillar working face mining has the following characteristics: first, the working face is surrounded by early mining goafs, which have been affected by multiple mining operations, the roof rock layer is seriously damaged, and the ground surface has also subsided to a certain extent; second, the working face is mostly on the surface of the ground. The mining of pressure coal resources such as buildings (structures), water bodies, and railways has higher requirements for surface movement and deformation; third, the working face is mostly a protective coal pillar set up due to the influence of mining layout, geological structure, etc., and even around the working face There are lanes and goafs inside the coal pillar working face, and the existence of geological structures such as faults makes the geological and mining conditions of the working face quite complex. These have had a serious impact on the safe mining of the remaining coal pillar working face.

Green mining technology in mines provides methods for recovering leftover coal pillars, but the adaptability of various mining technologies is different. For example, strip mining has low cost and good surface subsidence control effect, but there are problems such as low working surface mining efficiency and serious waste of coal resources; another example is backfill mining, which has good surface subsidence control effect, but has the problems of complex mining technology, high cost, and low efficiency. question.

Utility model content

The purpose of this utility model is to provide a mining overburden composite curtain that improves the overlying rock separation layer grouting effect. Based on the analysis of the mining characteristics of the left coal pillar working face, the utility model is used to improve the overlying rock separation layer grouting effect. The mining of overlying rock composite curtains and precise grouting subsidence reduction methods can improve the grouting effect and ensure precise grouting of the separation layer on the working face, thereby achieving the purpose of safe and efficient recovery of legacy coal resources.

In order to achieve the above purpose, the technical solution of the present utility model is: bending deformation layer

A mining overburden composite curtain that improves the grouting effect of the overburden separation layer, including multiple thick hard rock layers located above the coal seam at the working face. The multiple thick hard rock layers are formed with cracks or geological conditions before the coal seam is mined at the working face. Structural weak surface, a separation layer is formed after coal seam mining in the working face; the rock layer section with separation layer is called multi-separation layer grouting section, and the rock layer section without separation layer is called bedrock reinforcement section; It is characterized in that, before the coal seam is mined on the working face, cement slurry is injected into the fissures or weak surfaces of the geological structure and solidifies to form a curtain layer; after the coal seam is mined on the working face, the fly ash slurry injected into the space of the separation layer ; Among them, the curtain layer of the multi-separation layer grouting section forms an isolation curtain to prevent the fly ash slurry injected in the separation layer space from flowing to the goaf area of the adjacent working face; the curtain layer of the bedrock reinforcement section forms a protective curtain to prevent The fly ash slurry injected into the separation space leads to the ground along the cracks or weak surfaces.

As an improvement to the above technical solution, the isolation curtain or protective curtain is composed of multiple curtain layers.

As an improvement to the above technical solution, the fly ash slurry injected into the separation space of the multi-separation layer grouting section solidifies to form a fly ash layer.

The utility model's mining overburden composite curtain that improves the overburden separation layer grouting effect is formed by the following precise grouting and subsidence reduction method for multiple overburden separation layer layers, including the following steps:

S1. Determine the overlying rock layer above the goaf from bottom to top into a multi-separation layer grouting section and a bedrock reinforcement section based on the geological structure;

S2. Drill a grouting hole above the goaf. The hole is first drilled into the loose section. After drilling is completed, the casing is installed. Then the bedrock reinforcement section is drilled. During the drilling process, many weak surfaces in the geological structure are drilled. Cement slurry is injected into the thick hard rock layers to form a protective curtain, and casing is installed after drilling. Finally, the grouting section of the multi-separation layer layer is drilled. During the drilling process, the multi-layer thick hard rock layers that have been damaged or have cracks are drilled. Inject cement slurry to fill the cracks to form an isolation curtain. After drilling, set up casing. The casing in this section is a flower tube;

S3. In the grouting section of the multi-separation layer, inject fly ash slurry into the space between the rock strata affected by mining to form a filling layer of fly ash slurry, which limits the upward transmission of the space between the mining rock strata, thereby minimizing the purpose of land subsidence.

The grouting pipe is a three-section casing structure, including a flower tube extending into the grouting section of the multi-separation layer layer as a wall-protecting pipe for the grouting section of the multi-separation layer layer, and is sleeved in the grouting section of the multi-separation layer layer. The outer periphery of the section wall protection pipe only extends into the bedrock reinforcement section wall protection pipe of the bedrock reinforcement section and the outer circumference of the bedrock reinforcement section wall protection pipe only extends into the loose layer section wall protection pipe; the flower tube is at a height of Multiple slurry outlets are arranged evenly in the direction.

In actual operation, the more specific steps are

(1) Data and investigation analysis. Collect and analyze geological mining data of coal pillar working faces, mining data of adjacent working faces, surface buildings (structures), geological boreholes, and water well distribution data, and seal geological boreholes and abandoned water wells;

(2) Determine the amount of grouting for the borehole. According to the amount of coal extracted from the working face and the ground subsidence control requirements, the injection-production ratio is determined, and then the drilling grouting amount is determined;

(3) The number of drilling holes is determined. Determine the number of borehole arrangements based on the mining layout and size of the working face and the grouting diffusion radius of boreholes in the overlying rock separation layer;

(4) Determine each layer of borehole grouting and the borehole grouting pressure. Calculate the development height of the water-conducting fracture zone during mining, analyze the development layers of the mining-induced overlying rock separation layer, and determine the drilling injection while ensuring that sufficient isolation rock columns are left between the development height of the water-conducting fracture zone and the grouting layer. The position of each grouting layer is determined, and the drilling length and drilling grouting pressure of the grouting section of the multi-separation layer layer are calculated;

(5) Determine the drilling layout location. According to the working face mining method, coal seam inclination angle and borehole grouting layer (lowermost), the maximum subsidence main section position at the borehole grouting layer along the working face advancement direction is calculated, and then the surface drilling position is determined;

(6) The drilling structure is determined. According to the grouting layer of the borehole and the columnar shape of the rock layer, the borehole is set up with three sections from top to bottom: loose layer section, bedrock reinforcement section, multi-separated layer grouting section, and the total depth of the borehole is calculated;

(7) Composite curtain top setting. During the drilling of the bedrock reinforcement section of the borehole, by analyzing the overlying rock damage, distribution of faults and other geological structures, and the columnar shape of the rock strata near the working face, combined with the actual rock formation conditions during the drilling process, the deformation, damage, and crack development were analyzed. Thick and hard rock layers are injected with grout to pre-block rock formation fissures and strengthen weak surfaces. A multi-layer protective curtain is formed on the top of the grouting layer to prevent grouting and grouting accidents during grouting.

(8) Pre-grouting of grouting layers. During the drilling of the grouting section of the multi-separation layer of the borehole, grout is injected into the rock formation in this section to pre-block the rock formation fissures and strengthen the weak surfaces, and form an isolation curtain to isolate the rock formation fissure channels formed by mining on the adjacent working face to prevent injection. When grouting accidents occur during grouting, multi-layer and precise grouting of the overlying rock separation layer in this working face can be realized to improve the grouting subsidence reduction effect;

(9) Borehole pressure water monitoring. After the drilling, pre-grouting and casing setting are completed, the grouting orifice device and pipeline system are installed, and the water pressure is monitored in advance to grasp the timing of grouting.

(10) Drilling and grouting operations. By observing changes in water pressure, the initial grouting timing can be determined based on the water loss in the borehole. When the water loss in the borehole suddenly increases, the initial trial grouting can be carried out, and then normal grouting operations can be started.

In the above steps, specific operations such as data and survey analysis, the number of structural positions of the boreholes, the grouting amount and the grouting ratio are all determined based on the on-site geological conditions and the existing technology in this field. The focus of this application The aim is to propose a method of mining the overburden composite curtain and overburden multi-separation layer layers to improve the grouting effect.

The technical principle of the precise grouting and subsidence reduction method for multi-separated layers of overlying rock is as follows: setting grouting boreholes on the surface, and during the drilling process, the thick hard rock layers (including grouting layers) that have been damaged or have weak surfaces are (rock layer) by injecting grout to pre-block rock formation fissures and strengthen weak surfaces to form a protective curtain for the roof of the grouting layer and an isolation curtain between the grouting layer on the working surface and the adjacent goaf to prevent grouting and cross-grout accidents during grouting. occurs; on the basis of understanding the deformation and destruction laws of the overlying rock during mining, the development layers and characteristics of the overlying rock separation layer are analyzed, and the casing of the grouting section of the borehole is set as a floral tube; when underground coal seam mining causes overlying rock separation layer, , inject fly ash and other slurry materials into the separation space through drilling holes to achieve precise and multi-layer grouting of the overlying rock separation layer in the mining face under the protection of the composite curtain roof, improve the grouting effect, and limit the separation layer from moving to the surface Transfer development, and then control the surface deformation and settlement caused by mining, so as to achieve the purpose of safe recovery of coal resources such as "three-down" coal pressing.

Compared with the existing technology, the advantages and positive effects of this utility model are:

The main features of this utility model are shown in three aspects: first, a composite curtain top is set on the top of the grouting layer to form an isolation and protective curtain; second, the grouting is multi-layer; third, the rock layers in the grouting section of the multi-separation layer layer are advanced Cement slurry is pre-injected to form an isolation curtain from the adjacent goaf area to ensure precise grouting of the overlying rock separation layer in the mining face.

More specifically, this utility model has the following advantages:

(1) Effectively prevent grouting and grouting accidents during grouting. By injecting cement slurry into thick and hard rock layers where the bedrock reinforcement section has deformed, damaged, and developed cracks, the cracks in the rock formation can be blocked in advance and the weak surfaces can be reinforced. A multi-layer isolation and protection curtain can be formed on the top of the grouting layer to prevent the slurry from flowing along the rock layer during grouting. Flow in cracks or weak surfaces may cause slurry on the ground or slurry accidents between boreholes. In addition, grouting reinforcement and sealing can be carried out in advance to prevent slurry accidents such as plugging poor geological boreholes and uninvestigated plugged water wells.

(2) The grouting efficiency of the overlying rock separation layer is high. By changing single-layer grouting into multi-layer grouting, multiple detachment layers can be captured within a certain period of time for multi-layer grouting, and the timing of grouting can be better grasped to avoid layer detachment during single-layer grouting. The grout cannot be injected after rapid upward development, and it has strong adaptability to geological and stratigraphic conditions, and the overlying rock separation layer grouting efficiency is high.

(3) Achieve precise grouting of the mining separation layer in the working face. By injecting grout into the rock strata in the grouting section of the multi-separation layer layer, the rock strata fissures are blocked in advance and the weak surfaces are strengthened to form an isolation curtain, which isolates the rock stratum fissure channels formed by mining in the adjacent working face and prevents the outflow of slurry during grouting. This working face is realized Precise grouting of mining overlying rock separation layer to improve grouting subsidence reduction effect

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description These are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting any creative effort.

Figure 1 is a schematic structural diagram of a utility model multi-layer composite curtain roof with overlying rock separation layer;

Figure 2 is a schematic diagram of the segmented structure of the grouting pipe of the present invention;

Figure 3 is a schematic structural diagram of the utility model in actual operation;

Figure 4 is a schematic diagram of the subsidence detected by the surface measuring station during actual operation of the utility model.

Implementation

The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only part of the embodiments of the present utility model, not all implementations. example. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present utility model.

Figure 1 is a structural diagram of the utility model's mining overburden composite curtain that improves the overburden separation layer grouting effect. As shown in Figure 1, after the working face is mined, 1 is the goaf area, and the rock layer above the goaf area 1 According to the columnar shape of the rock layer and the multi-separated layer grouting layer, it is determined as the multi-separated layer grouting section 4 and the bedrock reinforcement section 7. The soil layer above the bedrock reinforcement section 7 is determined as the loose layer section 9.

Before coal seam mining in the working face, the multi-separation layer grouting section 4 and the bedrock reinforcement section 7 are composed of multiple layers of thick hard rock layers 5, and cracks or weak geological structures will occur between the multiple layers of thick hard rock layers 5. , there is no separation layer; but after the coal seam mining at the working face, the working face forms a goaf 1, then the multi-layer thick hard rock layer close to the goaf 1 will form a separation layer, then the multi-layer thick hard rock layer 5 will form a separation layer according to the existence of a separation layer The or non-separated layer is divided into a separation layer grouting section 4 and a bedrock reinforcement section 7. The rock layer section with a separation layer is called a multi-separation layer grouting section 4, and the rock layer section without a separation layer is called a multi-separation layer grouting section 4. This is bedrock reinforcement section 7.

The dividing line between the multi-separation layer grouting section 4 and the bedrock reinforcement section 7 is the highest separation layer 3, and below the highest separation layer 3 is the multi-separation layer grouting section 4 (including the highest separation layer 3 ), located above the goaf 1, consists of multiple thick hard rock layers 5 that are damaged or have cracks. The multiple thick hard rock layers 5 above the highest separation layer 3 form the bedrock reinforcement section 7, and the bedrock reinforcement section 7 above The soil layer is identified as loose layer 9.

Before coal seam mining at the working face, there are cracks or weak geological structures in the multi-layer thick hard rock layer 5 at the multi-separation layer grouting section 4 and the bedrock reinforcement section 7. First, cement slurry is injected to form a multi-layer curtain. layer to reinforce fissures or weak surfaces of geological structures; after mining of coal seams at the working face, separation layers 3 are generated between multiple thick hard rock layers 5 close to the goaf area in the vertical direction, and injection into the space of the separation layer 3 The fly ash slurry forms a filling layer of fly ash slurry to limit the upward transmission of the separation layer 3; the curtain layer formed by the solidification of the cement slurry in the multi-separation layer layer grouting section 4 is the isolation curtain 2 to prevent the pulverized coal injected in the separation layer space. The ash slurry flows to the goaf area of the adjacent working face; the curtain layer formed by the solidification of the cement slurry injected in the bedrock reinforcement section is the protective curtain 6 to prevent the fly ash slurry from emerging from the ground. Of course, these cement slurries and fly ash slurries are all injected downwardly through the grouting holes 8. During the injection process, the existing well 11 needs to be plugged.

Seen in conjunction with Figure 1, the mining overburden composite curtain of the present invention for improving the overburden separation layer grouting effect includes a multi-layer curtain layer used to reinforce cracks or weak surfaces of geological structures. The curtain layer is caused by the existence of cracks or geological structures. The structural weak surface is formed by injecting cement slurry into multiple thick hard rock layers. The fissures or geological structural weak surface are formed before coal seam mining in the working face;

After the coal seam is mined at the working face, in the vertical direction, separation layers occur between multiple thick hard rock layers close to the goaf. Fly ash slurry is injected into the space of the separation layer to form a fly ash slurry filling layer to limit the separation layer. pass upward;

The rock formation section with the separation layer is called the multi-separation layer grouting section. The curtain layer of the multi-separation layer grouting section forms an isolation curtain to prevent the fly ash slurry injected in the separation layer space from flowing to adjacent work. Surface goaf area; the rock section without formation of separation layer is called bedrock reinforcement section. The curtain layer of this bedrock reinforcement section forms a protective curtain to prevent the fly ash slurry injected in the separation layer space from conducting along the cracks or weak surfaces. ground.

The protective curtain is arranged in the bedrock reinforcement section. The bedrock reinforcement section is located above the grouting section of the multi-separation layer layer. It is composed of several rock layers that are bent and deformed due to the influence of coal seam mining on the current working face. The protective curtain is composed of existing Cement slurry is injected into multi-layered thick hard rock layers in fissures or weak planes of geological structures to strengthen the fissures or weak planes to prevent the fly ash slurry injected in the separation space of the overlying rock from being mined from leading to the ground along the fissures or weak planes.

The isolation curtain is set in the grouting section of the multi-separation layer. It is formed by injecting cement slurry into the multi-layer rock strata with cracks or weak surfaces in the geological structure to strengthen the cracks or weak surfaces. It isolates the goaf area formed by mining on the adjacent working face and prevents During grouting, grout outflow and grout accidents occurred.

The isolation curtain and protective curtain are composed of multiple curtain layers. Fly ash slurry is injected into the separation layer of the multi-separation layer grouting section to form a fly ash slurry filling layer to limit the upward transmission of the separation layer space between the mined rock layers. There is also a loose layer section on the bedrock reinforcement section, and the loose layer section is the soil layer located on the bedrock reinforcement section.

The grouting pipe is a three-section casing structure, including a flower tube extending into the grouting section of the multi-abstraction layer layer as a wall protection pipe for the grouting section of the multi-abstraction layer layer, and is sleeved in the grouting section of the multi-abstraction layer layer. The outer periphery of the protective wall pipe only extends into the bedrock reinforced section protective pipe of the bedrock reinforced section and the outer circumference of the protective wall pipe set in the bedrock reinforced section only extends into the loose layer section; the flower tube is in the height direction Arrange multiple pulp outlets evenly.

The utility model's precise grouting and subsidence reduction method for the multi-level composite curtain roof of the overlying rock separation layer includes the following steps:

S1. Determine the overlying rock layer above the goaf from bottom to top into a multi-separation layer grouting section and a bedrock reinforcement section based on the geological structure;

S2. Drill a grouting hole above the goaf. The hole first drills into the loose layer. After the drilling is completed, the casing is installed. Then the bedrock reinforcement section is drilled. During the drilling process, many weak surfaces in the geological structure are drilled. Cement slurry is injected into the thick hard rock layers to form a protective curtain, and casing is installed after drilling. Finally, the grouting section with multiple separation layers is drilled. During the drilling process, the multi-layered thick hard rock layers that have been damaged or have cracks are drilled. Inject cement slurry to fill the cracks to form an isolation curtain. After drilling, set up casing. The casing in this section is a flower tube;

S3. In the grouting section of the multi-separation layer, inject fly ash slurry into the space between the rock strata affected by mining to form a filling layer of fly ash slurry, which limits the upward transmission of the space between the mining rock strata, thereby minimizing the purpose of land subsidence.

The grouting pipe is a three-section casing structure, including a flower tube extending into the grouting section of the multi-separation layer layer as the wall-protecting pipe 12 of the grouting section of the multi-separation layer layer, which is sleeved on the grouting section of the multi-separation layer layer. The outer circumference of the section protection pipe 12 only extends into the bedrock reinforcement section, the bedrock reinforcement section protection pipe 13 and the outer circumference of the bedrock reinforcement section protection pipe 13 only extends into the loose section protection pipe 14; The flower tube is evenly provided with a plurality of pulp outlets 15 in the height direction.

The technical solution of this utility model has been tried in the Peigou Mine of Yanghe Coal Company. The application situation of the Peigou Mine of Yanghe Coal Company is introduced below:

Peigou Mine of Yanghe Coal Mining Company is located in the southeast of Xinmi City, Henan Province. It is administratively under the jurisdiction of Laiji Town, Liuzhai Town and Dakai Town of Xinmi City. The main coal seam mined in the mine is Permian Shanxi Formation 21 coal. The mine is currently in the later stage of mining and mainly recovers the mining geological conditions and the remaining coal pillar resources. Mine 22151 working face is a test application working face, located in the southeast of Peigou mine field 22 mining area. The working face is about 280m long in direction and 106m long in tendency. The surface elevation of the working face is +220.1~+226.4m, the working face elevation is -60.5~-97m, the average burial depth of the working face is 302m; the average thickness of the coal seam is about 7.1m, and the average inclination angle of the coal seam is about 12°.

The Gyoufanggou fault in the south of the working face is adjacent to the 32 mining area, the north is adjacent to the goaf of the 22111 working face, the east is the central four downhill roadways, and the west is the goaf of the 220021 working face; the lower part of the working face is -110 horizontal road, 32 There are permanent refuge chambers and rock tunnels such as -110 water warehouse in the mining area. The upper surface is the provincial road Wangguan Road. There are a large number of residential buildings on both sides of the road. Among them, the key protected buildings include gas stations, hospitals, tax offices, etc.; the working surface is within In the 220031, 220041, 220051 strip goaf areas and part of the 22111 working face goaf area. The geological mining conditions of the working face are very complex, which is a typical mining of legacy difficult-to-mine coal pillar resources and does not meet the conditions for using conventional mining methods. Moreover, due to the large goaf range outside and inside the working face, the severe damage to the overlying rock strata in the area, and the high level of protection required for surface buildings, it is difficult to achieve the ground subsidence reduction requirements using conventional overlying rock separation layer grouting technology. Therefore, during the mining of the working face, the multi-layer precision grouting and subsidence reduction technology of the overlying rock separation layer under the composite curtain roof was adopted.

Application:

The 22151 working face is mined using the multi-layer precision grouting and subsidence reduction technology of the overlying rock separation layer under the composite curtain roof. The grouting process and various parameters were analyzed and determined in accordance with the technical requirements and steps, as shown in Figure 3 (where grouting The analysis takes the 1# grouting hole as an example).

(1) Data and survey analysis

Through data analysis, we learned about the working face and adjacent mining, overlying rock lithology and columnar distribution, and the distribution and protection requirements of surface buildings (structures) above the well. The surface survey found 6 geological boreholes and 15 water wells, and the poorly plugged boreholes and water wells were resealed and reinforced with concrete.

(2) Determine the amount of grouting for drilling holes

According to the protection requirements of ground buildings (structures) and calculated based on the injection-to-production ratio of 48% to 60%, the daily grouting volume of drilling is 1,200t to 1,500t, and the daily coal output is 2,500t.

(3) Determine the number of drilling layouts

The advancing length of the working face is about 280m, and the inclination length is about 106m. According to the grouting diffusion radius of the overlying rock separation layer drilling holes and the distribution and protection requirements of the ground buildings, the drilling spacing is determined to be 65m, and a total of 4 grouting holes are arranged.

(4) Determination of each layer of borehole grouting and borehole grouting pressure

①Development height of water-conducting fissure zone

According to the columnar shape and lithology of the rock formation, the mining method and mining thickness of the working face, the calculation formula in the "Guidelines for Coal Pillar Retention and Coal Pressure Mining in Buildings, Water Bodies, Railways and Main Tunnels" is used to obtain the water diversion for working face mining. The development height of the fissure zone is 81.4~152m; based on calculations based on the actual measured cracking ratio of 14.5 in the mine, the development height of the water-conducting fissure zone is 103m. It is comprehensively determined that the average mining thickness of the working face is 7.1m, and the development height of the water-conducting fissure zone is 103m.

② Determination of drilling grouting layers

There are 14 thick hard rock layers in the overlying rock layer of the coal seam in the 22151 working face, of which 3 thick hard rock layers are thick and hard control layers. The first thick hard control layer is fine-grained sandstone, 4.46m away from the coal seam roof. The second thick hard control layer is fine-grained sandstone, 69.42m away from the coal seam roof. The third thick hard control layer is fine-grained sandstone, 170.05m away from the coal seam roof (burial depth 126.51m). According to the calculation results of the development height of the water-conducting fracture zone, the first and second thick hard control layers of the overlying rock are located within the water-conducting fracture zone, and no separation layer will be formed below it. The position of the third thick hard control layer is higher than the development height of the water-conducting fracture zone, and is 66.88m away from the top of the water-conducting fracture zone. This distance is much greater than the thickness of the overlying rock separation layer grouting protection isolation rock column (5M, M is the mining thickness). And there are still two thick hard rock layers above the third thick hard control layer, with burial depths of 95.57m and 106.13m respectively. There are conditions for the formation of separation layers below the third thick hard control layer and its upper thick hard rock layer. . Therefore, the grouting layer is selected as the third thick and hard control layer and the lower separation layer of the overlying hard rock layer to achieve three-layer grouting. The length of the grouting section is 30.9m, and the bottom thick and hard control layer is the grouting layer. Depth is 126.5m.

③ Determination of drilling grouting pressure

According to the depth of the bottom grouting layer of borehole grouting (126.5m), the early grouting pressure: the early grouting pressure is not lower than the natural pressure of the grouting layer, that is, not less than 1.4Mpa; subsequently, within the duration of the separation layer Continuous grouting. Mid-stage grouting: After the pressure is reduced, pressure grouting is maintained, that is, the orifice pressure P>0. Post-grouting pressure: The final grouting pressure is equal to 1.2 to 1.5 times the natural pressure of the formation at the grouting layer, and the grouting pressure range is 1.7 to 2.1MPa.

(5) Determine the drilling layout location

According to the mining method of the working face, the inclination angle of the coal seam and the drilling and grouting layer (the bottom), it is calculated that the maximum sinking main section position along the direction of the working face at the drilling and grouting layer is 75.7m away from the wind tunnel on the working surface. Combined with the drilling The layout spacing, quantity and protection requirements for ground buildings (structures) are then determined, as shown in Figure 3. The 1# and 2# grouting holes are located on both sides of the road, focusing on protecting the buildings (structures) on both sides of the road, as shown in Figure 3.

(6) Determination of drilling structure

According to the columnar data of the A10/CK9 borehole in the working face, combined with the borehole grouting layer and depth, it is determined that the depth of the loose section of the borehole is 0~16m, the depth of the bedrock reinforced section is 16~95m, and the depth of the multi-separation layer layer is determined to be 0~16m. The depth of the slurry section is 30m, and the total depth of the construction drilling is 125m. A three-section structure is set up from top to bottom of the borehole, that is, a Φ244.5×8.94mm casing is installed as a loose section wall protection pipe for the first opening of Φ311mm drilling; a Φ177.8×8.05mm casing is installed for bedrock reinforcement during the second opening of Φ216mm drilling. Segment retaining pipe; three-opening Φ152mm drilling and lowering Φ139.7×9.17mm floral tube as a segmented retaining pipe for grouting in multiple detachment layers, as shown in Figure 2.

(7) Composite screen top setting

During the drilling of the bedrock reinforcement section of the borehole, by analyzing the goaf conditions around the working face, overlying rock damage and fault distribution, combined with the actual rock formation conditions during the drilling process, the sandy mudstone with a burial depth of 33.4m was analyzed. layer (thickness 8.3m), a mudstone layer (thickness 10.0m) with a burial depth of 43.4m, a medium-grained sandstone layer (thickness 11.6m) with a burial depth of 68.1m, and a mudstone layer (thickness 13.8m) with a burial depth of 81.9m, four layers thick The hard rock layer is injected with grout to seal the damage cracks and weak surfaces of the rock layer, forming an isolation and protection curtain to prevent grouting and grouting accidents during grouting, and improve the grouting effect. By pre-injecting cement slurry into the thick hard rock layer at the top of the grouting layer, the cracks and weak surfaces of the rock layer were reinforced, and the poorly filled water wells were re-blocked. When pre-injecting cement slurry into the rock layer, the formation was affected by multiple mining operations. The activation weak surface was blocked, and a linear slurry overflow point appeared on the surface. Affected by repeated mining, the cracks between the well wall and the stratum of the previously filled water well were blocked, and cement slurry overflowed from around the well wall.

(8) Pre-grouting of grouting layers

During the drilling of the multi-separation layer grouting section of the borehole, grout was injected into the mudstone, fine-grained sandstone and sandy mudstone within 30.9m of the section to pre-block rock formation fissures and strengthen weak surfaces to isolate adjacent working faces for mining. The formation of rock fissure channels prevents grouting accidents, enables precise grouting at multiple layers of the overlying rock separation layer in the working face, and improves the grouting subsidence effect, as shown in Figure 3.

(9) Borehole pressure water monitoring

After the drilling of the borehole, pre-injection of cement slurry and casing setting are completed, the grouting orifice device and pipeline system are installed, and the pressure water of the borehole is monitored to grasp the timing of grouting.

(10) Drilling and grouting operations

Grouting and coal mining operations are carried out strictly in accordance with the principle of "matching predetermined mining and main mining". The daily footage of the working face is about 2m, the coal output is about 2500t/d, and the grouting volume is about 1300t/d.

During the mining period of the working face, through regular observations of the surface observation lines and important building observation points, the results show that the maximum subsidence value of the ground surface is 374.1mm, and the subsidence coefficient is 0.053, as shown in Figure 4; the gas station measurement point has the largest The subsidence value is 368.9mm. The gas station is well protected. There are only 1-2mm cracks in the office building walls and about 2mm cracks on the ground surface. The maximum subsidence value at the hospital measuring point is 95.3mm, with no obvious deformation or damage. Under the protection of the composite curtain roof, multi-layer and precise grouting of the mining separation layer of the 22151 working face was realized, and the remaining coal pillar resources were also safely and efficiently recovered, with significant economic and social benefits.

In this test, the overlying rock separation layer grouting mining technology was used. Compared with strip mining, it solved the problems of low mining efficiency and serious waste of coal resources. Compared with fill mining, it solved the problems of complex mining technology, high cost and low efficiency. , is an effective way to recycle coal pillars left in mines. The key to the successful implementation of this technology is to accurately grasp and control various parameters of separation layer grouting, including the location and spacing of grouting holes, grouting layer, grouting pressure, grouting amount and grouting timing.

Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts, and any modifications, equivalent substitutions, improvements, etc. shall be included in the protection of the present utility model. within the range.

Claims (3)

1. A mining overburden composite curtain for improving overburden separation grouting effect comprises a plurality of layers of thick hard rock layers positioned on a working face coal layer, wherein the thick hard rock layers are provided with cracks or geological structure weaknesses before the working face coal layer is mined, and separation layers are formed after the working face coal layer is mined; the rock layer section with the separation layers is called a multi-separation layer grouting section, and the rock layer section without the separation layers is called a bedrock reinforcement section; before mining a working face coal bed, injecting cement slurry into the fracture or the weak face of the geological structure to solidify and form a curtain layer; after mining the working face coal seam, injecting pulverized fuel ash slurry into the space of the separation layer; the curtain layers of the multi-separation-layer grouting section form isolation curtains to prevent the fly ash slurry injected in the separation layer space from flowing to the goaf of the adjacent working face; the curtain layer of the bedrock reinforcement section forms a protective curtain to prevent the pulverized fuel ash slurry injected into the separation layer space from being conducted to the ground along cracks or weak surfaces.

2. The mining-induced overburden composite curtain for improving overburden separation grouting effect according to claim 1, wherein the isolation curtain or the protection curtain is composed of a plurality of curtain layers.

3. The mining-induced overburden composite curtain for improving overburden separation grouting effect according to claim 1 or 2, wherein fly ash slurry injected in separation space of multi-separation-layer grouting section is solidified to form fly ash layer.