CN112377193B - Deep well small coal pillar gob-side entry retaining method based on top breaking and pressure relief of lower key layer of top plate - Google Patents

Abstract

The invention provides a deep well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of a lower key layer of a roof, relates to the technical field of coal mining, and improves ventilation and support in deep well gob-side entry retaining. The method comprises the following steps: determining a roof geological condition, determining blasting parameters according to the roof geological condition, numerically simulating the top breaking and pressure relief effects of lower key layers with different thicknesses, and determining top breaking parameters of a roadway; then, constructing and blasting in the test roadway, and arranging a displacement monitoring station, an anchor rod and an anchor cable stress monitoring station on surrounding rock in the roadway; and correcting support parameters, constructing and blasting in the roadway of the gob-side entry retaining, and supporting according to the corrected support parameters. According to the method, blasting is carried out on one side of the coal seam roof, which is deviated from solid coal, and the stress transfer of the key layer is cut off on the lower key layer of the pre-cracked coal seam roof, so that high stress acting on the small coal pillars and the gob-side entry retaining is transferred, the roadway environment is improved, and the maintenance of the roadway is facilitated.

Description

Gob-side entry retaining method for small coal pillars in deep wells based on pressure relief from fault roof in key strata under roof

technical field

The invention relates to the technical field of coal mining, in particular to a pressure relief and support method for gob-side entry retaining with small coal pillars in deep wells.

Background technique

With the depletion of resources in the shallow part of the coal mine, the mining depth of the mine is increasing year by year, and the occurrence conditions of the coal seam are becoming more and more complicated. It is also increasingly prominent, especially for old mines and mines with complex conditions, which seriously restrict the safe and efficient production of mines. The currently commonly used gob-side roadway arrangement has the contradiction between the tight excavation continuity and the series ventilation of the high-gas mine working face; although the wide coal pillar roadway protection method can solve the above problems, it will cause a large coal loss on the one hand. , and more importantly, a high degree of stress concentration must be formed on the coal pillars of deep wells, which can easily induce rock burst disasters.

Gob-side entry retention is to use certain technical means to reserve the mining roadway of the previous section for the next section. Gas accumulation and other advantages. However, the currently adopted support methods (wood stacks, dense pillars, gangue strips, concrete blocks, paste, etc.) that do not leave coal pillars completely gob-side entry retaining roadway, due to the high pressure in deep mines, the existing support methods None of them can effectively solve the technical problems such as difficulty in ventilation in deep thick coal seam and high gas mines, natural air leakage in goaf, and difficulty in support. In addition, the roof-cutting and pressure-relieving automatic roadway-free mining technology has also been applied. The roof-cutting and pressure-relieving automatic roadway-free mining technology uses the roof directional pre-splitting and cutting seam, and strongly supports the roof of the mining roadway. Under the action of the mine pressure of the roof stratum, the roof part of the rock mass is cut off along the pre-split slits to realize automatic road formation and coal pillar-free mining. However, the technology of roof cutting self-formed roadway requires super support for gob-side entry retention, which is difficult and costly, and the roadside gangue retaining system is difficult to block the infiltration of harmful gases; in addition, roof cutting and pressure relief self-formed roadway has no Coal pillar mining technology is seriously affected by high ground pressure, so it is less used in deep mine mining.

Therefore, in order to solve the contradiction between the gob-side entry retaining mining and the roadway ventilation and roadway support in deep mine mining, it is not only necessary to solve the difficult problem of deep well ventilation, especially for high gas mines, but also to ensure small coal pillars. It plays the role of isolating the harmful gas, water and gangue in the goaf of the upper working face; on the other hand, it is necessary to solve the problem of continuous mining and ensure the balanced and efficient production of the mine. Due to the high in-situ stress of gob-side entry retention in deep wells and the influence of two mining dynamic pressures on the upper working face and this working face, small coal pillars and gob-side entry retention are affected by high support pressure and mining action, and normal It is very difficult to keep the roadway under the mining conditions.

SUMMARY OF THE INVENTION

In order to improve the ventilation and support conditions in the gob-side entry retaining of the deep well, ensure the stability of the small coal pillars, and effectively isolate the harmful gas in the upper working face, the present invention provides a deep well small coal mine based on the roof pressure relief of the key layer under the roof. The specific technical scheme of the coal pillar gob-side entry retaining method is as follows.

The gob-side entry retaining method for small coal pillars in deep wells based on the pressure relief of fault roof in key layers below the roof, the steps include:

A. Determine the geological conditions of the coal seam roof;

B. Determine the fault roof parameters of blasting according to the geological conditions of the coal seam roof, and the fault roof parameters of the blasting include the position and thickness of the fault roof of the lower key layer;

C. Numerical simulation of the relationship between the thickness of the fault roof, the deformation of the surrounding rock after the pressure relief of the fault roof, and the surrounding rock stress of the roadway;

D. Determine the roof fault parameters of the roadway according to the deformation of the surrounding rock and the stress distribution of the roadway;

E. Carry out blasting in the test roadway according to the parameters of the broken roof, and arrange displacement monitoring stations, anchor rods and anchor cable force monitoring stations in the surrounding rock in the test roadway;

F. Correct the support parameters according to the surface displacement curve of the test roadway, the monitoring curve of the force of the bolt and the monitoring curve of the force of the anchor cable;

G. Carry out blasting and broken roof in the roadway of gob-side entry retention, and support the gob-side entry-retention roadway according to the revised support parameters.

Preferably, the geological conditions of the roof include roof lithology and roof thickness, and the underlying critical layer transmits stress from the overburden.

Preferably, the top breaking parameters include drilling parameters and explosive parameters, wherein the drilling parameters include the distance of the drilling ahead of the working face, the drilling diameter, the drilling angle, the drilling depth and the drilling spacing, and the explosive parameters Including blast radius, charge and seal length.

It is also preferred that in the drilling parameters, the distance between the drilling and the roadway on one side of the solid coal is greater than 200 mm, and the diameter of the drilling is 48-50 mm; the inclination angle of the drilling in the thin coal seam is 20°, and the inclination angle of the drilling in the medium-thick coal seam or the thick coal seam is 20°. is 10°-15°; the drilling depth is greater than the thickness of the lower key layer; the spacing of drilling holes in hard rock is 500mm, and the spacing between drilling holes in soft rock is 1000mm.

It is also preferred that, in the blasting parameters of the explosive, the radius of the drill hole is R ₀ with the drill hole as the center, the radius of the crushing zone is R ₁ , the radius of the rupture zone is R ₂ , the radius of the vibration zone is R ₃ , and the radius of the rupture zone is R 3 . The radius is the blasting radius; blasting the traditional Chinese medicine roll to the position of the lower key layer.

Further preferably, the value of the blast radius R ₂ is:

r_b为钻孔半径，S_T为岩石的单轴抗拉强度，μ为泊松比，ρ₀为炸药密度，D为爆炸速度，r_c为装药半径；n为应力增大倍数，取8-11。where α is the stress wave attenuation coefficient, and α=2-b; b is the ratio of radial stress to tangential stress, and b=μ/(1-μ), P ₂ is the shock wave stress without coupling charge coefficient peak, and

r _b is the borehole radius, S _T is the uniaxial tensile strength of the rock, μ is the Poisson’s ratio, ρ ₀ is the explosive density, D is the explosion velocity, _rc is the charge radius; n is the stress increase multiple, take 8-11.

It is further preferred that an energy collecting pipe is installed in the blasted borehole, and the energy collecting direction is parallel to the direction of the roadway.

It is further preferred that, in the numerical simulation, UDEC is used to simulate the pressure relief of the key layer under the roof in the gob-side entry retention of the small coal pillar in the deep well, or FLAC3D is used to simulate the gob-side entry retention of the small coal pillar in the deep well. The key layer in the lower part of the mid-roof plate is fractured and the roof is relieved.

It is further preferred that the top fault parameters corresponding to the minimum value of the deformation of the surrounding rock and the minimum value of the stress distribution of the roadway are selected.

Further preferably, the support parameters include the length of the anchor rod, the length of the anchor cable, the row spacing between the anchor rods and the row spacing between the anchor cables.

The beneficial effects of the gob-side entry retaining method for small coal pillars in deep wells based on the pressure relief of fault roofs in key layers below the roof provided by the present invention are:

(1) By cutting off the key layer below the coal seam roof of the "transfer rock beam" in advance, the high stress acting on the small coal pillar and gob-side entry retaining is effectively transferred to the coal layer farther away, so that the small coal pillar and Gob-side entry retention is affected by lower stress and mining dynamic pressure, which is beneficial to the bearing stability of small coal pillars and greatly reduces the support difficulty of gob-side entry retention.

(2) The stability of the small coal pillar can not only isolate the harmful gas in the goaf of the previous working face, but also have the function of retaining gangue and water; The mine is produced efficiently, and large coal pillars are avoided to ensure the recovery rate;

(3) Use numerical simulation to select appropriate blasting parameters for roof breaking, and monitor the effect of support in the test roadway, and determine reasonable support parameters through analysis to ensure the roadway safety of gob-side entry retention; in addition, this method also The roof is broken by construction blasting, and drilling parameters and explosive parameters are set to ensure the effect of pressure relief on the lower key layer; avoid stress concentration, control the deformation of the roadway, and ensure ventilation safety.

Description of drawings

Fig. 1 is the schematic diagram of gob-side entry retaining arrangement of small coal pillars in deep wells;

Fig. 2 is the schematic diagram of gob-side entry retaining after the working face is mined;

Figure 3 is a side view towards the solid coal side;

Figure 4 is a schematic diagram of the stress distribution before the pressure relief of the lower key layer fault top;

Figure 5 is a schematic diagram of the stress distribution of the lower key layer after the fault top is relieved;

Fig. 6 is a schematic diagram of blasting area division;

Figure 7 is a schematic diagram of monitoring in the test roadway;

Figure 8 is a graph of the subsidence amount of the roof before and after breaking the roof and releasing pressure;

Fig. 9 is a curve diagram of the approaching amount of the solid coal side roadway before and after the roof breaking and pressure relief;

Fig. 10 is a curve diagram of the approaching amount of the roadway on the side of the coal pillar before and after the roof is broken and the pressure is relieved;

Fig. 11 is the change diagram of the working resistance of the bolt before and after the top is broken and the pressure is relieved;

Figure 12 is a graph of the distance between the working face of the station and the working resistance of the roof bolt.

In the picture: 1-upper key layer, 2-sand mudstone, 3-lower key layer, 4-direct roof, 5-face to be mined, 6-gob retaining entry, 7-return airway at coal mining face, 8- Coal working face, 9-preset drilling, 10-pre-splitting slit, 11-small coal pillar; 12-bolt force monitoring, 13-anchor cable force monitoring.

Detailed ways

With reference to FIGS. 1 to 12 , the specific implementation of the method for gob-side entry retaining for small coal pillars in deep wells based on the pressure relief of the key layer under the roof provided by the present invention will be described.

Example 1

Due to the deep coal seam in deep mines, especially in high gas mines, there are problems such as difficulty in ventilation of mining tunnels and tight mining continuity, so gob-side entry retention must be adopted. Influence, small coal pillars need to bear high bearing pressure and mining pressure, and it is difficult for small coal pillars to maintain stability. In addition, in the process of gob-side entry retaining of small coal pillars, the parameters of construction breaking roof pressure relief and support parameters are difficult to determine. Therefore, a deep well small coal pillar gob-side entry retaining method based on roof pressure relief of key layers under the roof is provided. method, the specific steps include:

Step A. Determine the geological conditions of the roof of the coal seam; wherein the geological conditions of the roof include roof lithology and roof thickness, and also include the joint structure, degree of cementation, structural development (faults, folds, etc.) and stability of the roof. The measurement and mine geological exploration data are determined, and the actual exploration can also be performed at the working face position.

Step B. According to the geological conditions of the coal seam roof, theoretical calculation is used to determine the parameters of the fault roof for blasting. The fault roof parameters for blasting include the position and thickness of the fault roof of the lower key layer, and the lower key layer transmits the stress from the overlying rock layer.

Generally, the buried depth of coal seams in deep mines is more than 600m, which is affected by high in-situ stress; among them, the lower key layer is the rock layer that is closest to the direct roof above the direct roof, has large thickness and hard rock, and can transmit the stress of the overlying layer; as shown in Figure 1 and As shown in Figure 2, the first hard rock layer above the mudstone is the lower key layer, and the upper key layer is above the lower key layer. According to the theory of "transfer rock beam", the direct roof cannot transfer stress.

Step C. Numerically simulate the relationship between the thickness of the fault roof, the deformation of the surrounding rock after the pressure relief of the fault roof, and the surrounding rock stress of the roadway. In the numerical simulation, UDEC (Universal Distinct Element Code, a calculation and analysis program based on the discrete element method theory) is used to simulate the pressure relief of the key layer under the roof in the middle roof of the gob-side entry retaining of small coal pillars in deep wells, and the working face is determined according to the mining design parameters. parameters and roadway parameters, determine the thickness and position of the top of the fault, and then use the software to simulate the relationship between the thickness of the top of the fault and the deformation of the surrounding rock and the stress of the roadway after the pressure relief of the top of the fault; or use FLAC3D (three-dimensional finite difference program to carry out Three-dimensional structural stress characteristics simulation and plastic flow analysis) simulation of small coal pillar gob-side entry retention in deep wells for the pressure relief of the key layer under the roof of the roof, combined with the mining design parameters to determine the working face parameters and roadway parameters, determine the thickness and location of the fault roof, Then the software is used to simulate the relationship between the thickness of the fault roof, the deformation of the surrounding rock after the pressure relief of the fault roof and the surrounding rock stress of the roadway.

Step D. Determine the parameters of the broken roof of the roadway according to the deformation amount of the surrounding rock and the stress distribution of the roadway. Specifically, the fault roof parameters corresponding to the minimum value of the deformation of the surrounding rock and the minimum value of the stress distribution of the roadway are selected.

Among them, its top parameters include drilling parameters and explosive parameters. The drilling parameters include the distance of the drilling ahead of the working surface (the position of the drilling), the diameter of the drilling, the angle of drilling, the depth of the drilling and the spacing between the drillings, etc., and the parameters of the explosive Including blasting radius, charge amount, sealing method and sealing length, etc.

In the drilling parameters, the distance between the drilled hole and the roadway on the side of the solid coal is greater than 200mm, and the drill hole for blasting is arranged on the roof of the return air roadway (gob-side entry) in the first mining face, and is biased to the side of the solid coal; the diameter of the drill hole is Take 48-50mm; drill holes are arranged obliquely upward on the roof of the roadway, the inclination angle of the drill holes in the thin coal seam is 20°, and the inclination angle of the drill holes in the medium-thick coal seam or thick coal seam is 10°-15°; the drill hole depth is greater than that of the lower key layer. Thickness, so as to ensure that the lower key layer can be cut off after blasting; the spacing of drilling holes in hard rock is 500mm, and the spacing between drilling holes in soft rock is 1000mm.

In the blasting parameters of the explosive, the radius of the drill hole is R ₀ , the radius of the crushing area is R ₁ , the radius of the rupture area is R ₂ , the radius of the vibration area is R ₃ , and the radius of the rupture area is the blasting radius. ; Blasting the traditional Chinese medicine roll to the position of the lower key layer. The value of the blast radius R ₂ is:

r_b为钻孔半径，S_T为岩石的单轴抗拉强度，μ为泊松比，ρ₀为炸药密度，D为爆炸速度，r_c为装药半径；n为应力增大倍数，取8-11。where α is the stress wave attenuation coefficient, and α=2-b; b is the ratio of radial stress to tangential stress, and b=μ/(1-μ), P ₂ is the shock wave stress without coupling charge coefficient peak, and

r _b is the borehole radius, S _T is the uniaxial tensile strength of the rock, μ is the Poisson’s ratio, ρ ₀ is the explosive density, D is the explosion velocity, _rc is the charge radius; n is the stress increase multiple, take 8-11.

In addition, pre-splitting can be achieved by pre-drilling and drilling and blasting, and energy-gathering pipes can also be installed in the blasting holes, and the direction of energy-concentration is parallel to the direction of the roadway, so that the slit can be better formed and the lower position can be realized. Cracking of critical layers.

Step E. Carry out blasting in the test roadway according to the parameters of the broken roof. The roadway in the test section is the roadway with a length of about 60m in the coal mining face of the gob-retained roadway for testing, and the surrounding rock in the test roadway is arranged with displacement monitoring stations, Bolt and anchor cable force monitoring station, through the monitoring station to determine the roadway surface displacement curve, bolt force monitoring curve and anchor cable force monitoring curve under the current support.

Step F. Amend the support parameters according to the test roadway surface displacement curve, the anchor force monitoring curve and the anchor cable force monitoring curve. The support parameters include the length of the anchor rod, the length of the anchor cable, the row spacing between the anchor rods and the row spacing between the anchor cables. When the surface displacement of the roadway is too large, it is necessary to adjust the support parameters and strengthen the support; The force is within the set effective support range.

Step G. Continue mining, construct blasting and break the roof in the roadway of the gob-side entry retention, and support the gob-side entry-retention roadway according to the revised support parameters.

Example 2

On the basis of Example 1, taking the working face of a mine adopting the method of gob-side entry retaining in deep wells with small coal pillars based on the pressure relief of the key layer under the roof as an example, the support effect of this method is further explained by monitoring the situation. .

Combining with Fig. 7 to Fig. 10, comparing the roof subsidence amount, the moving amount of solid coal side roadway, the moving amount of roadway and the working resistance of the bolt before and after the pressure relief of the broken roof can be seen. The key layer under the roof of the coal seam with "beam" effectively transfers the high stress acting on the small coal pillars and gob-side entry retention to the coal strata farther away, so that the small coal pillars and gob-side entry retention are subject to lower stress. Therefore, it is beneficial to the bearing stability of the small coal pillar and greatly reduces the support difficulty of gob-side entry retaining; in addition, the stability of the small coal pillar can not only isolate the harmful gas in the gob of the previous working face, but also It also has the functions of retaining gangue and water; in addition, leaving small coal pillars solves the problem of tight mining continuity in deep mining, which can ensure efficient mine production, and avoid leaving large coal pillars to ensure recovery rate; this method It can also effectively avoid stress concentration, control the deformation of the roadway, and ensure ventilation safety. After the working face starts to advance, the concentration area of the leading bearing pressure and the lateral bearing pressure is transferred from the unfractured rock layer (upper key layer) overlying the basic top to the center of the next working face, and the stress at the gob-side entry retaining position is relatively small; This method can effectively transfer the stress concentration area at the position of gob-side entry retention, and the deformation of gob-side entry retention is small.

Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present invention should also belong to the present invention. the scope of protection of the invention.

Claims (10)

1. A deep well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of a lower key layer of a roof is characterized by comprising the following steps:

A. determining the geological condition of a coal seam roof;

B. determining blasting top breaking parameters according to geological conditions of a coal seam roof, wherein the blasting top breaking parameters comprise the position and the thickness of a lower key layer top breaking;

C. numerically simulating the relation between the broken top thickness and the deformation of the surrounding rock after breaking the top and relieving pressure and the stress of the surrounding rock of the roadway;

D. determining top breaking parameters of the roadway according to the surrounding rock deformation and the roadway stress distribution;

E. constructing blasting in a test roadway according to the top breaking parameters, and arranging a displacement monitoring station, an anchor rod and an anchor cable stress monitoring station on surrounding rocks in the test roadway;

F. correcting support parameters according to the test roadway surface displacement curve, the anchor rod stress monitoring curve and the anchor cable stress monitoring curve;

G. and constructing a blasting roof in the roadway of the gob-side entry retaining, and supporting the roadway of the gob-side entry retaining according to the corrected supporting parameters.

2. The deep well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of a roof lower key layer according to claim 1, wherein the geological conditions of the roof include roof lithology and roof thickness, and the lower key layer transmits stress from an overlying rock layer.

3. The deep well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of the lower key layer of the roof, according to claim 1, is characterized in that the roof breaking parameters comprise drilling parameters and explosive parameters, wherein the drilling parameters comprise a distance of a drilling advance working face, a drilling diameter, a drilling angle, a drilling depth and a drilling interval, and the explosive parameters comprise a blasting radius, a charging amount and a seal length.

4. The deep-well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of the lower key layer of the roof, according to claim 3, is characterized in that the distance between a drill hole and a side entry wall of solid coal is greater than 200mm in the drilling parameters, and the diameter of the drill hole is 48-50 mm; the inclination angle between the drill hole in the thin coal seam and the vertical direction is 20 degrees, the inclination angle between the drill hole in the medium-thickness coal seam or the thick coal seam and the vertical direction is 10-15 degrees, and the drill hole is deviated to one side of the solid coal; the drilling depth is greater than the thickness of the lower key layer; the distance between the drill holes in the hard rock is 500mm, and the distance between the drill holes in the soft rock is 1000 mm.

5. The deep well small coal pillar gob-side entry retaining method based on top breaking and pressure relief of the top plate lower key layer according to claim 3, wherein in the explosive parameters, the radius of a drill hole with the drill hole as a center is R₀The radius of the crushing zone is R₁Radius of the cracking zone being R₂Radius of vibration region is R₃Wherein the radius of the rupture zone is the burst radius; and (4) blasting the traditional Chinese medicine rolls to the position of the lower key layer.

6. The deep-well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of the roof lower key layer as claimed in claim 5, wherein the blasting radius R is₂The values of (A) are as follows:

wherein α is the stress wave attenuation coefficient, and α is 2-b; b is the ratio of radial stress to tangential stress, and b is μ/(1- μ), P₂Is the peak stress of the shock wave at the uncoupled charge coefficient, an

r_bIs the borehole radius, S_TIs the uniaxial tensile strength of the rock, mu is the Poisson's ratio, ρ₀Is the density of the explosive, D is the detonation velocity, r_cIs the charge radius; and n is the stress increase multiple and is 8-11.

7. The deep-well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of the lower key layer of the roof as claimed in claim 5, wherein an energy-gathering pipe is installed in a blasting borehole, and the energy-gathering direction is parallel to the direction of the roadway.

8. The deep-well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of the lower key layer of the roof is characterized in that in numerical simulation, UDEC is used for simulating roof breaking and pressure relief of the lower key layer of the roof in the deep-well small coal pillar gob-side entry retaining, or FLAC3D is used for simulating roof breaking and pressure relief of the lower key layer of the roof in the deep-well small coal pillar gob-side entry retaining.

9. The deep-well small coal pillar gob-side entry retaining method based on top breaking and pressure relief of the top plate lower key layer according to claim 1, characterized by selecting top breaking parameters corresponding to a minimum value of deformation of surrounding rocks and a minimum value of stress distribution of a roadway.

10. The deep-well small coal pillar gob-side entry retaining method based on roof breaking and pressure relief of the lower key layer of the roof, according to claim 1, is characterized in that the support parameters comprise anchor rod length, anchor cable length, inter-anchor rod row spacing and inter-anchor cable row spacing.

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