CN220621952U - Mining overburden composite curtain for improving 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

Mining overburden composite curtain for improving overburden separation layer grouting effect

Technical Field

The utility model relates to the technical field of coal mine filling exploitation, in particular to a mining overburden composite curtain for improving overburden separation layer grouting effect

Background

The large-scale exploitation of coal resources causes overlying strata to destroy and the development of a separation layer to be transferred to the ground surface to be expressed as subsidence and crack development of the ground surface, and the damage of building (construction) of the ground surface, water body, railway and the like is directly caused. Along with the later mining of the mine, recycling the coal pillar resources left by the influences of mining layout, geological structure, three-lower coal pressing and the like becomes an effective way for improving the mining rate of the coal resources and realizing the green sustainable development of the mine.

Coal pillar face mining generally has the following characteristics: the working face is surrounded by a pre-mining goaf, which is influenced by multiple mining, the roof strata is seriously damaged, and the earth surface is sunk to a certain extent; secondly, most of working surfaces are surface building (construction) buildings, water bodies, railway and other coal resource exploitation, and the requirement on surface movement deformation is high; thirdly, the working face is mostly protected coal pillars reserved under the influence of mining layout, geological structures and the like, a roadway and a mining space exist around the working face even in the working face of the coal pillars, and geological mining conditions of working face mining are quite complex due to the existence of geological structures such as faults and the like. These have a serious impact on the safe exploitation of the working face of the legacy coal pillar.

The green mining technology of the mine provides a method path for recycling the residual coal pillars, but the adaptability of various mining technologies is different. If the mining cost of the strip is low, the ground subsidence control effect is good, but the problems of low mining efficiency of the working face and serious waste of coal resources exist; and the subsidence control effect of the ground surface of filling mining is good, but the problems of complex mining process, high cost and low efficiency exist.

Disclosure of Invention

The utility model aims to provide the mining overburden composite curtain for improving the overburden separation layer grouting effect, and the mining overburden composite curtain for improving the overburden separation layer grouting effect and the accurate grouting subsidence reducing method are adopted on the basis of analyzing the mining characteristics of the working face of the legacy coal pillar, so that the grouting effect can be improved, the accurate grouting of the working face separation layer is ensured, and the aim of safe and efficient recycling of the legacy coal resources is further realized.

In order to achieve the above object, the technical scheme of the present utility model is as follows: bending deformation layer

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.

As an improvement to the above technical solution, the isolation curtain or the protection curtain is composed of a plurality of curtain layers.

As an improvement to the technical scheme, the fly ash slurry injected into the separation layer space of the multi-separation layer grouting section is solidified to form a fly ash layer.

The utility model relates to a mining overburden composite curtain for improving overburden separation layer grouting effect, which is formed by the following overburden multi-separation layer accurate grouting and sinking reducing method, and comprises the following steps:

s1, determining a cover rock layer above a goaf as a multi-separation-layer grouting section and a bedrock reinforcement section from bottom to top according to the condition of a geological structure;

s2, drilling grouting holes above the goaf, drilling loose intervals, and setting a sleeve after finishing drilling; then drilling a bedrock reinforcement section, injecting cement slurry into a multi-layer thick hard rock stratum with a geological structure weak face in the drilling process to form a protective curtain, and setting a sleeve after drilling is finished; finally drilling a multi-separation layer grouting section, wherein cement slurry is injected into the multi-layer thick hard rock stratum with damaged or existing cracks to fill the cracks in the drilling process, so as to form an isolation curtain, and a sleeve is arranged after drilling is finished, wherein the sleeve is a flower pipe;

s3, injecting pulverized coal mortar into the separation layer space between the rock strata affected by mining in the multi-separation layer grouting section to form a pulverized coal mortar body filling layer, limiting upward transmission of the separation layer space between the mining rock strata, and further achieving the purpose of reducing ground subsidence.

The grouting pipe is of a three-section sleeve structure, and comprises a flower pipe extending into a multi-separation-layer horizon grouting section as a multi-separation-layer horizon grouting section wall protecting pipe, a bedrock reinforcing section wall protecting pipe sleeved on the periphery of the multi-separation-layer horizon grouting section wall protecting pipe and only extending into a bedrock reinforcing section, and a loose layer section wall protecting pipe sleeved on the periphery of the bedrock reinforcing section wall protecting pipe and only extending into a loose layer section; the straw is evenly provided with a plurality of slurry outlets in the height direction.

In practice, the more specific operation steps are

(1) And (5) data and investigation analysis. Collecting and analyzing geological mining data of coal pillar working surfaces, mining data of adjacent working surfaces, distribution data of earth surface building (construction), geological drilling holes and water wells, and plugging the geological drilling holes, abandoned water wells and the like;

(2) And (5) determining the drilling grouting amount. According to the coal yield of the working face and the ground subsidence control requirement, determining the injection ratio, and further determining the drilling grouting quantity;

(3) The number of drill hole arrangements is determined. Determining the number of drill holes according to the mining layout and the size of the working face and combining the grouting diffusion radius of the overlying strata separation layer drill holes;

(4) And determining each horizon of drilling grouting and drilling grouting pressure. Calculating the development height of the mining water-guiding fracture zone, analyzing the mining overlying strata separation layer development horizon, determining the positions of all the horizons of the drilling grouting under the condition that enough isolated rock columns are reserved between the development height of the water-guiding fracture zone and the grouting horizon, and calculating the drilling length and drilling grouting pressure of the grouting sections of the multiple separation strata;

(5) And determining the arrangement position of the drilling holes. According to the working face mining mode, the coal seam inclination angle and the drilling grouting layer position (the lowest part), calculating to obtain the maximum sinking main section position of the drilling grouting layer position along the working face advancing direction, and further determining the surface drilling position;

(6) And determining a drilling structure. According to drilling slip casting horizon, combine the formation column, the drilling sets up three section structures from top to bottom: loose layer section, bedrock reinforcement section, multi-layer horizon grouting section, and calculate the total depth of drilling;

(7) The composite curtain top is arranged. During the drilling of a base rock reinforcing section of a drilling hole, by analyzing the geological structure distribution such as overburden damage, faults and the like, the formation column and the like of adjacent working surfaces, and combining the actual formation conditions in the drilling hole, grouting thick hard rock stratum with deformation damage and crack development, pre-plugging the crack of the rock stratum and reinforcing weak surfaces, and forming a multilayer protective curtain at the top of a grouting layer to prevent slurry overflow and slurry stringing accidents during grouting.

(8) Grouting layer pre-grouting. During the drilling of a multi-layer grouting section of a drilling hole, grouting cement paste is injected into the section of rock stratum, rock stratum cracks and reinforcing weak surfaces are plugged in advance, an isolation curtain is formed, rock stratum crack channels formed by mining adjacent working surfaces are isolated, the occurrence of slurry-mixing accidents during grouting is prevented, multi-layer and accurate grouting of the rock-covering layer of the mining working surfaces is realized, and grouting and sinking reducing effects are improved;

(9) And (5) monitoring drilling water pressure. After drilling, pre-grouting cement slurry and sleeve setting are completed, a grouting orifice device and a pipeline system are installed, water pressing monitoring is carried out in advance, and grouting time is mastered.

(10) Drilling and grouting operation. By observing the water pressure change condition, the primary grouting time is judged according to the water leakage amount in the drilled hole, when the water leakage amount in the drilled hole is suddenly increased, primary trial grouting can be performed, and then normal grouting operation is started.

In the above steps, specific operations such as data and investigation analysis, the number of structural positions of drilling, grouting amount and grouting ratio are all determined according to the on-site geological condition in combination with the existing prior art in the field, and the focus of the application is to provide a mining overburden composite curtain for improving the overburden grouting effect and a overburden multi-delamination accurate grouting and subsidence reducing method.

The method for accurately grouting and reducing the sedimentation of the multi-layer horizon of the overlying strata has the technical principle that: grouting drilling holes are drilled on the ground surface, thick hard rock layers (including grouting layer rock layers) with broken or weak surfaces are subjected to grouting in the drilling process, rock layer cracks and reinforcing weak surfaces are plugged in advance, grouting layer top plate protection curtains, working surface grouting layers and isolation curtains adjacent to goaf are formed, and grouting accidents are prevented during grouting; analyzing the formation horizon and the characteristics of the overburden separation layer on the basis of grasping the deformation and destruction rule of the mining overburden, and setting the sleeve pipe of the drilling grouting section as a flower pipe; when the overlying strata is generated due to underground coal seam exploitation, slurry materials such as fly ash are injected into the strata space through drilling holes, so that accurate and multi-layer grouting of the overlying strata on the working face under the protection of the composite curtain roof is realized, the grouting effect is improved, the transmission development of the strata to the ground surface is limited, and the ground surface deformation and settlement caused by exploitation are controlled, so that the aim of safely recycling coal resources such as 'three-lower' pressed coal is realized.

Compared with the prior art, the utility model has the advantages and positive effects that:

the main characteristics of the utility model are as follows: firstly, arranging a composite curtain top on the top of a grouting layer to form an isolation protection curtain; grouting is carried out on multiple layers; and thirdly, cement paste is pre-injected into the rock stratum of the multi-layer horizon grouting section in advance to form an isolation curtain adjacent to the goaf, so that accurate grouting of the overlying strata of the working face mining is ensured.

More specifically, the utility model has the following advantages:

(1) Effectively preventing slurry overflow and slurry mixing accidents during grouting. The thick hard rock stratum with deformation damage and crack development on the base rock reinforcement section is injected with cement paste, so that the rock stratum cracks and reinforcement weak surfaces can be plugged in advance, a plurality of layers of isolation protection curtains are formed at the top of the grouting layer, and slurry is prevented from flowing along the rock stratum cracks or weak surfaces during grouting, so that ground slurry burst or slurry stringing accidents between drilling holes are prevented. In addition, the method can also carry out grouting reinforcement and plugging in advance on poor-plugging geological drilling holes, non-investigation plugging water wells and the like, and prevent slurry leakage accidents.

(2) And the overlying strata separation grouting efficiency is high. Through become the multilayer position slip casting with individual layer position slip casting, can catch a plurality of absciss layers in the certain time quantum and carry out the multilayer position slip casting, better assurance slip casting opportunity avoids the quick back thick liquid slip casting phenomenon of upwards developing of absciss layer when single layer position slip casting, and strong adaptability to geology and stratum condition, overburden absciss layer slip casting is efficient.

(3) Accurate grouting of the working face mining separation layer is achieved. By grouting cement paste into the rock stratum of the multi-separation-layer grouting section, rock stratum cracks and reinforcing weak surfaces are plugged in advance, an isolation curtain is formed, rock stratum crack channels formed by mining adjacent working surfaces are isolated, outflow of slurry during grouting is prevented, accurate grouting of the mining overlying strata of the working surfaces is realized, and grouting and sinking reduction effects are improved

Drawings

In order to more clearly illustrate the embodiments of the utility model or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the utility model, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.

FIG. 1 is a schematic diagram of a multi-layer composite roof of an inventive overburden delamination;

FIG. 2 is a schematic sectional view of a grouting pipe according to the present utility model;

FIG. 3 is a schematic view of the structure of the present utility model in actual operation;

FIG. 4 is a schematic representation of the subsidence as monitored by the surface station during actual operation of the present utility model.

Description of the embodiments

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Fig. 1 is a structural diagram of a mining overburden composite curtain for improving overburden separation grouting effect, as shown in fig. 1, after mining on a working face, 1 is a goaf, rock strata above the goaf 1 are determined to be a multi-separation-layer grouting section 4 and a bedrock reinforcement section 7 according to a rock stratum column and multi-separation-layer grouting layers, and a soil layer above the bedrock reinforcement section 7 is determined to be a loose layer section 9.

Before mining of a working face coal seam, the multi-separation-layer horizon grouting section 4 and the bedrock reinforcement section 7 are composed of multiple layers of thick hard rock layers 5, cracks or geological structure weaknesses are generated among the multiple layers of thick hard rock layers 5, and separation layers are avoided; however, after the working face coal seam is mined, the working face forms the goaf 1, multiple layers of thick hard rock layers close to the goaf 1 form separation layers, multiple layers of thick hard rock layers 5 are divided into a separation layer grouting section 4 and a bedrock reinforcing section 7 according to the presence or absence of the separation layers, wherein the rock layer section with the separation layers is called a multi-separation layer grouting section 4, and the rock layer section without the separation layers is called a bedrock reinforcing section 7.

The parting line of the multi-separation layer grouting section 4 and the bedrock reinforcement section 7 is a separation layer 3 at the highest position, the multi-separation layer grouting section 4 (comprising the separation layer 3 at the highest position) is arranged below the highest separation layer 3, the multi-separation layer grouting section is positioned above the goaf 1 and consists of multi-layer thick hard rock layers 5 with broken or cracked cracks, the multi-layer thick hard rock layers 5 above the highest separation layer 3 form the bedrock reinforcement section 7, and the soil layer above the bedrock reinforcement section 7 is determined to be a loose layer section 9.

Before mining a working face coal seam, a multi-layer horizon grouting section 4 and a multi-layer thick hard rock layer 5 at two sections of a bedrock reinforcement section 7 are provided with cracks or geological structure weaknesses, cement slurry is firstly injected to form a plurality of curtain layers so as to reinforce the cracks or geological structure weaknesses; after mining a working face coal seam, generating a separation layer 3 between a plurality of layers of thick hard rock layers 5 close to a goaf in the vertical direction, and injecting fly ash slurry into a space of the separation layer 3 to form a pulverized coal slurry body filling layer so as to limit the upward transmission of the separation layer 3; the curtain layer formed by the solidification of the cement paste of the multi-separation-layer grouting section 4 is an isolation curtain 2, so that the fly ash slurry injected into the separation layer space is prevented from flowing to the goaf of the adjacent working face; the curtain layer formed by solidification of cement slurry injected into the bedrock reinforcement section is a protective curtain 6 for preventing the fly ash slurry from overflowing from the ground. Of course, both the cement slurry and the pulverized coal slurry are injected downward through the injection holes 8. During the injection, the existing well 11 needs to be plugged.

Referring to fig. 1, the mining overburden composite curtain for improving overburden separation grouting effect comprises a plurality of curtain layers for reinforcing cracks or geological structure weak surfaces, wherein the curtain layers are formed by injecting cement slurry into a plurality of thick hard rock layers with cracks or geological structure weak surfaces, and the cracks or geological structure weak surfaces are formed before mining of coal seams of working surfaces;

after mining the coal seam of the working face, generating a separation layer between multiple layers of thick hard rock layers close to the goaf in the vertical direction, and injecting fly ash slurry into a space of the separation layer to form a pulverized coal slurry filling layer so as to limit upward transmission of the separation layer;

the rock layer section with the separation layers is called a multi-separation layer grouting section, and curtain layers of the multi-separation layer grouting section form isolation curtains to prevent coal ash slurry injected in the separation layer space from flowing to the goaf of the adjacent working face; the section of the rock where no delamination layer is formed is called a bedrock reinforcement section, and the curtain layer of the bedrock reinforcement section forms a protective curtain to prevent the fly ash slurry injected into the delamination space from conducting to the ground along a crack or a weak surface.

The protection curtain is arranged on a bedrock reinforcement section, the bedrock reinforcement section is arranged above a multi-separation-layer horizon grouting section and consists of a plurality of rock strata which are subjected to bending deformation under the influence of the coal seam mining of the current working face, and the protection curtain is formed by injecting cement slurry into a plurality of layers of thick hard rock strata with cracks or geological structure weak faces to reinforce the cracks or the weak faces so as to prevent the coal ash slurry injected into the mining overburden separation layer space from being conducted to the ground along the cracks or the weak faces.

The isolation curtain is arranged at the multi-separation-layer grouting section, is formed by injecting cement slurry into a multi-layer rock stratum with cracks or geological structure weak surfaces to strengthen the cracks or the weak surfaces, and is used for isolating adjacent working surfaces to mine and form goaf so as to prevent slurry outflow and slurry string accidents during grouting.

The isolation curtain and the protection curtain are composed of a plurality of curtain layers. And the separation layers of the multi-separation layer grouting section are injected with pulverized coal mortar to form a pulverized coal mortar body filling layer so as to limit upward transmission of separation layer spaces among mining rock layers. The bed rock reinforcement section is also provided with a loose layer section, and the loose layer section is a soil layer positioned on the bed rock reinforcement section.

The grouting pipe is of a three-section sleeve structure, and comprises a flower pipe extending into a multi-separation-layer horizon grouting section as a multi-separation-layer horizon grouting section wall protecting pipe, a bedrock reinforcing section wall protecting pipe sleeved on the periphery of the multi-separation-layer horizon grouting section wall protecting pipe and extending into a bedrock reinforcing section only, and a loose layer section wall protecting pipe sleeved on the periphery of the bedrock reinforcing section wall protecting pipe and extending into a loose layer section only; the straw is evenly provided with a plurality of slurry outlets in the height direction.

The utility model relates to a precise grouting and sinking reducing method for a multi-layer composite roof of a overlying strata separation layer, which comprises the following steps:

s1, determining a cover rock layer above a goaf as a multi-separation-layer grouting section and a bedrock reinforcement section from bottom to top according to the condition of a geological structure;

s2, drilling grouting holes above the goaf, drilling loose intervals, and setting a sleeve after finishing drilling; then drilling a bedrock reinforcement section, injecting cement slurry into a multi-layer thick hard rock stratum with a geological structure weak face in the drilling process to form a protective curtain, and setting a sleeve after drilling is finished; finally drilling a multi-separation layer grouting section, wherein cement slurry is injected into the multi-layer thick hard rock stratum with damaged or existing cracks to fill the cracks in the drilling process, so as to form an isolation curtain, and a sleeve is arranged after drilling is finished, wherein the sleeve is a flower pipe;

s3, injecting pulverized coal mortar into the separation layer space between the rock strata affected by mining in the multi-separation layer grouting section to form a pulverized coal mortar body filling layer, limiting upward transmission of the separation layer space between the mining rock strata, and further achieving the purpose of reducing ground subsidence.

The grouting pipe is of a three-section sleeve structure, comprises a flower pipe extending into a multi-separation-layer horizon grouting section as a multi-separation-layer horizon grouting section wall protecting pipe 12, a bedrock reinforcing section wall protecting pipe 13 sleeved on the periphery of the multi-separation-layer horizon grouting section wall protecting pipe 12 and extending into a bedrock reinforcing section only, and a loose layer section wall protecting pipe 14 sleeved on the periphery of the bedrock reinforcing section wall protecting pipe 13 and extending into a loose layer section only; the straw is provided with a plurality of pulp outlets 15 uniformly in the height direction.

The technical scheme of the utility model is tried in Pei ditch ore of Yang He coal industry company, and the following description is presented in terms of the degree of Pei ditch ore of Yang He coal industry company:

yang He coal industry Pei ditch ore is located in the southeast of Xinmi city of Henan province, and administrative affiliation is governed by Xinmi city as a town, liu Zhai town and Dafei town. The main mining coal layer of the mine is two 1 coals of the two-fold system Shanxi group, and the current mine enters the later mining, and mainly recovers the resources of the mining geological condition complex and the legacy coal pillar. The mine 22151 working face is a test application working face and is positioned in the southeast part of the Pei Goujing field 22 mining area. The working surface runs about 280m long, tending to be about 106m long. The elevation of the surface of the working surface is +220.1 to +226.4m, the elevation of the working surface is-60.5 to-97 m, and the average burial depth of the working surface 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 degrees.

The fault of the oil separation mill in the south of the working face is adjacent to the 32 mining areas, the north is adjacent to the 22111 working face goaf, the east is the central four downhill tunnels, and the west is the 220021 working face goaf; the lower part of the working face is provided with a horizontal roadway-110, a permanent refuge chamber of 32 mining areas, a water sump-110 and other rock roadways, the upper surface is a provincial road Wang Guanlu, and a large number of civil house buildings are distributed on two sides of the road, wherein the important building protection is provided with gas stations, hospitals, tax offices and the like; the work surface has 220031, 220041 and 220051 strip goafs and 22111 work surface partial goafs. The geological mining conditions of the working face are quite complex, and the method belongs to typical exploitation of the resources of the coal pillars which are difficult to be exploited, and does not have the conditions of adopting the conventional exploitation method. And because the working face has large peripheral and internal mining ranges, the regional overlying strata are seriously damaged, the surface building has high protection level requirements and the like, the ground subsidence reducing requirements are difficult to realize by adopting the conventional overlying strata separation layer grouting technology. Therefore, the multi-layer accurate grouting and subsidence reducing technology of the overlying strata under the composite roof is specially adopted during the mining of the working face.

The application conditions are as follows:

22151 working face is mined by adopting a composite roof under-roof overlying strata multi-layer accurate grouting and sinking reducing technology, grouting process and parameters are analyzed and determined according to technical requirements and steps, and as shown in fig. 3 (grouting analysis is taking a 1# grouting hole as an example).

(1) Data and investigation analysis

Through data analysis, the conditions of working face and four-neighbor exploitation, overlying rock lithology and columnar distribution, distribution of the surface (building) on the well, protection requirements and the like are mastered. The surface survey searches for 6 geological holes and 15 water wells, and the poorly blocked holes and the water wells are re-blocked and reinforced by concrete,

(2) Drilling grouting amount determination

According to the protection requirement of the ground building (structure), the daily grouting amount of the drilling holes is 1200 t-1500 t and the daily coal yield is 2500t according to the injection ratio of 48% -60%.

(3) Determination of the number of drill holes

The running direction of the working face is 280m in advancing length and 106m in inclined length, the drilling spacing is 65m according to the drilling grouting diffusion radius of the overlying strata separation layer and the distribution and protection requirements of the ground building, and 4 grouting holes are distributed in total.

(4) Determination of drill grouting pressure and each horizon of drill grouting

(1) Development height of water-guiding fracture zone

According to the columnar and lithology of the rock stratum, the mining mode of the working face and the mining thickness condition, adopting a calculation formula in a building, water body, railway and main roadway coal pillar reserving and pressed coal mining guide to obtain the development height of a mining water guide fracture zone of the working face as 81.4-152 m; calculating according to the actual measured fracture mining ratio of the mine to be 14.5, wherein the development height of the water guide fracture zone is 103m; the average mining thickness of the working face is comprehensively determined to be 7.1m, and the development height of the water diversion fracture zone is 103m.

(2) Borehole grouting horizon determination

22151 the face coal overburden has a total of 14 layers of hard rock, of which 3 layers are thick hard control layers. The first layer of thick hard control layer is fine sand, 4.46m from the roof of the coal seam. The second layer of hard control layer was fine grain sandstone, 69.42m from the roof of the coal seam. The third layer of hard control layer is fine sand rock and is located at a distance of 170.05m (126.51 m from the depth of burial) from the roof of the coal seam. According to the calculation result of the development height of the water guiding fracture zone, the first and second hard control layers of the overlying strata are positioned in the water guiding fracture zone, and no separation layer is formed below the first and second hard control layers. The third layer thick hard control layer is higher than the development height of the water guiding fracture zone, and is 66.88m away from the top of the water guiding fracture zone, and the distance is far greater than the thickness of the overlying strata separation layer grouting protection isolation rock column (5M, M is the mining thickness). And 2 layers of hard rock layer still exist above the third layer of hard control layer, the burial depths are 95.57m and 106.13m respectively, and the separation layer forming conditions are provided below the third layer of hard control layer and the upper layer of hard rock layer. Therefore, the grouting layer is selected as the third layer thick hard control layer and the lower separation layer of the hard rock layer covered by the third layer thick hard control layer, three-layer grouting is realized, the length of the grouting section is 30.9m, and the depth of the grouting layer of the bottommost layer thick hard control layer is 126.5m.

(3) Borehole grouting pressure determination

According to the depth (126.5 m) of the bottom grouting layer of the drilling grouting, the pre-grouting pressure is as follows: the early grouting pressure is not lower than the natural pressure of the stratum at the grouting layer, namely not lower than 1.4Mpa; and then grouting continuously for the duration of the delamination. Grouting medium period: after the pressure drop, a pressure grouting, i.e. an orifice pressure P > 0, is maintained. Grouting later-stage pressure: the final grouting pressure is 1.2-1.5 times of the natural pressure of the stratum at the grouting layer, and the grouting pressure interval is 1.7-2.1 MPa.

(5) Borehole placement position determination

According to the working face mining mode, the coal seam inclination angle and the drilling grouting layer (bottommost), the maximum sinking main section position of the drilling grouting layer along the working face is calculated to be 75.7m away from the air drift on the working face, and the ground surface drilling position is determined by combining the drilling arrangement interval, the number and the ground building protection requirements, as shown in figure 3. Wherein the grouting holes 1# and 2# are positioned on two sides of the road, and the construction (construction) of the two sides of the road is emphasized to be protected, as shown in fig. 3.

(6) Borehole structure determination

According to the A10/CK9 drilling columnar data in the working surface, the depth of the loose layer section of the drilling is 0-16 m, the depth of the bed rock reinforcing section is 16-95 m, the depth of the multi-separation layer grouting section is 30m, and the total depth of the construction drilling is 125m. A three-section structure is arranged from top to bottom in the drilling, namely, a phi 244.5 multiplied by 8.94mm sleeve is arranged in one-open phi 311mm drilling as a loose layer section wall protection pipe; drilling with a diameter of 216mm on the second opening and setting a diameter of 177.8X8.05 mm sleeve as a wall protection pipe of the bedrock reinforcement section; three-hole phi 152mm drilling down into phi 139.7x9.17 mm flowtube as multi-layer horizon grouting section wall protecting tube is shown in figure 2.

(7) Composite roof arrangement

During the drilling of a base rock reinforcement section of a drilling hole, cement slurry is injected into four layers of hard rock layers of a sandy mud layer (thickness 8.3 m) with a depth of burial of 33.4m, a mud layer (thickness 10.0 m) with a depth of burial of 43.4m, a medium-grain sand layer (thickness 11.6 m) with a depth of 68.1m and a mud layer (thickness 13.8 m) with a depth of 81.9m respectively by analyzing the situation of four adjacent blank mining, overburden damage and fault distribution of a working face and combining with the situation of an actual rock layer in the drilling hole drilling process, so that isolation protection curtains are formed, slurry leakage and slurry-mixing accidents during grouting are prevented, and grouting effect is improved. The cement paste is pre-injected into the thick and hard rock stratum at the top of the grouting layer, the rock stratum cracks and the weak surfaces are reinforced, the poor-landfill water well is plugged again, when the cement paste is pre-injected into the rock stratum, the weak surfaces of the activated stratum are plugged under the influence of multiple mining, and a linear slurry overflow point appears on the earth surface. The cement slurry overflows from the periphery of the well wall due to the influence of multiple mining operations and the gap between the well wall of the well which is buried before and the stratum is blocked.

(8) Grouting layer pre-grouting

During the drilling of a multi-separation-layer grouting section of a drilling hole, grouting cement slurry is injected into mudstone, fine sand rock and sandy mudstone within the range of 30.9m of the section, rock stratum cracks and reinforcing weak surfaces are plugged in advance, rock stratum crack channels formed by mining adjacent working surfaces are isolated, slurry-string accidents are prevented, multi-layer accurate grouting of the overlying strata of the mining working surfaces is realized, and grouting and sinking reducing effects are improved, as shown in figure 3.

(9) Drilling water pressure monitoring

After the drilling, the pre-grouting of cement paste and the sleeve are arranged, a grouting orifice device and a pipeline system are installed, the water pressure monitoring is carried out on the drilling, the grouting time is controlled,

(10) Drilling grouting operation

The grouting and coal exploitation operation is carried out strictly according to the principle of 'fixed exploitation and main exploitation matching', the daily working face feeding rule is about 2m, the coal output is about 2500t/d, and the grouting amount is about 1300 t/d.

During working face mining, the surface observation line and important building observation points are observed regularly, and the result shows 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 maximum sinking value of the station measuring point of the gas station is 368.9mm, the gas station is well protected, only 1-2mm cracks appear on the wall of the office building, and the ground surface cracks are about 2 mm; the maximum sinking value of the measuring point of the hospital is 95.3mm, and no obvious deformation and damage exists. The multi-layer and accurate grouting of the mining separation layer of the 22151 working face is realized under the protection of the composite curtain top, the safety and high-efficiency recovery of the left-over coal pillar resources are also realized, and the economic and social benefits are obvious.

According to the test, the overburden separation layer grouting mining technology is used, the problems of low mining efficiency and serious coal resource waste are solved compared with the strip mining, and the problems of complex mining technology, high cost and low efficiency are solved compared with the filling mining, so that the method is an effective way for recycling the mine residual coal pillars. The key point of the work implementation of the technology is to accurately grasp and control various parameters of separation layer grouting, including grouting hole positions and intervals, grouting layers, grouting pressure, grouting amount, grouting time and the like.

All other embodiments, modifications, equivalents, improvements, etc., which are apparent to those skilled in the art without the benefit of this disclosure, are intended to be included within the scope of this utility model.

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.