CN111396050B - Grid-shaped drilling site actual measurement method for shallow single-key-layer stope overlying strata structure - Google Patents
Grid-shaped drilling site actual measurement method for shallow single-key-layer stope overlying strata structure Download PDFInfo
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Abstract
The invention discloses a grid-shaped drilling site actual measurement method for a shallow single-key-layer stope overburden rock structure, and belongs to the technical field of coal mining. The actual measurement method comprises the steps that a plurality of fixed measurement stations are arranged in an auxiliary transportation crossheading; the drilling hole in the return air crossheading is divided into displacement inclined holes AnDisplacement vertical hole BnAnd peep inclined hole Cn: displacement vertical hole BnAnd the displacement inclined hole AnLocated in the same plane and displaced vertical holes BnAnd a displacement inclined hole AnCrossing to form a net shape; peep inclined hole CnArranged parallel to the maximum displacement inclined hole; and (3) actually measuring the broken movement track and the displacement change rule of the roof rock stratum by using the drilling fields arranged in the auxiliary transportation crossheading and the return air crossheading. The auxiliary transportation crossheading drilling system can realize real-time monitoring of the whole process from the front of mining to the rear of mining of a working face, and meets the existing observation requirements on roof overlying strata caving zones and fissure zones; the advanced drilling of the return air crossheading is used for monitoring the information of the overtime breakage or movement of the top plate, and can meet the important information source of early warning and forecast of the pressure of the working face in the prior art.
Description
Technical Field
The invention relates to the technical field of coal mining, in particular to a grid-shaped drill site actual measurement method for a shallow single-key-layer stope overburden rock structure.
Background
In the process of mining underground coal resources, how to control the activities of overlying strata is a primary problem. Only by mastering the structure possibly formed after the rock mass is damaged and the activity rule of the structure, the 'support-surrounding rock' relationship can be reasonably utilized, the safety of a stope is economically controlled, and the safety of personnel and equipment is guaranteed. The stope overburden rock structure is not a manual structure, local observation, borehole peeking and advanced testing means such as acoustic emission, microseismic and optical fiber are adopted on site, and the morphological characteristics of overburden rock damage are expected to be obtained. Physical simulation or numerical calculation is adopted in the laboratory, stope movement is simulated and restored, and the overlying strata structure is analyzed and deduced by acquiring, analyzing and processing characteristic data.
The working surface pressure is the expression of the roof structure movement. The method is characterized in that the movement rule of the top plate structure is mastered, and a mechanical model of the top plate structure is established, so that the method is an important basis for revealing the mechanism and determining reasonable supporting resistance. The "masonry beam" theory for stope formation control proposed by the qiang high courier comes from the borehole measurements of roof fracture motions. In the field of shallow coal seams, the yellow celebration professor proposes the definition of the shallow coal seams with key layers, a base-load ratio and burial depth as indexes in 2000, and proposes a top plate structure model of a step rock beam to be generally applied. According to actual measurement and theoretical analysis, shallow coal seams can be divided into 2 types: (1) a typical shallow coal seam is characterized by: shallow buried, small base load ratio and single key layer structure. (2) The shallow coal seam with large bedrock thickness and small loose load layer thickness is near the shallow coal seam and generally shows two groups of key layers, and slight step sinking phenomenon exists. However, the top plate structure of the shallow-buried working face is mainly based on theoretical models provided by bracket load actual measurement, physical simulation and numerical calculation, and no systematic top plate structure actual measurement research exists. The actual measurement of roof rock stratum movement at home and abroad is mostly vertical drilling observation constructed on the ground of a working face, the vertical drilling cost is high, the observation period is long, and the heights of a separation zone and a caving zone are mainly observed; the indirect observation method can really master the fracture space position and strength of the working face, but is difficult to master the real conditions of roof fracture and structure movement.
The Shenfu mining area is provided with 2-2 coal beds widely, the 2-2 coal beds are buried shallow and have large mining thickness, the general mining height is 3-8 m, the dip angle of the coal bed is 1-3 degrees, overlying rock bedrock is thin, the thickness of a loose layer is large, and the Shenfu mining area is of a single key layer structure. With the continuous development of 2-2 coal seams, the stope safety of a shallow single-key-layer coal seam becomes a technical problem to be solved urgently in a mining area. Therefore, the actual measurement of the shallow single-key-layer roof structure has great theoretical and practical guiding significance, roof safety accidents caused by large-range pressure of the working face are avoided, and the safe stoping of the working face is guaranteed.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a grid-shaped drill site actual measurement analysis method for a shallow-buried single-key-layer stope overburden rock structure.
The invention provides a grid-shaped drilling site actual measurement method for a shallow-buried single-key-layer stope overburden rock structure, which comprises the following steps of: s1, respectively arranging a plurality of groups of drill holes on an auxiliary transportation crossheading and a return air crossheading of a working face, wherein the specific arrangement method is as follows;
a plurality of fixed measuring stations are arranged in the auxiliary transportation crossheading, and the drill holes of the fixed measuring stations comprise displacement drill holes Dn,En,FnAnd a peep bore parallel to the displacement bore FnSetting;
the drill holes in the return air crossheading are divided into vertical holes and inclined holes according to the inclination angles of the drill holes and the working surface, and the vertical holes and the inclined holes are divided into displacement inclined holes A according to functionsnDisplacement vertical hole BnAnd peep inclined hole CnWherein n is 1, 2, 3 … … i: the displacement vertical hole BnAnd the displacement inclined hole AnLocated in the same plane and displaced vertical holes BnAnd a displacement inclined hole AnCrossing to form a net shape; peep inclined hole CnIs arranged parallel to the maximum displacement inclined hole and is used for peeping the inclined hole CnThe horizontal spacing from the corresponding maximum displacement inclined hole is a:
displacement drilling D for fixing measuring station in auxiliary transportation crossheadingn,En,FnAnd displacement inclined hole A in peeping hole and return air crossheadingnDisplacement vertical hole BnAnd peep inclined hole CnTogether forming a grid-like drill site borehole, wherein n is 1, 2, 3 … … i;
and S2, actually measuring the broken movement track and the displacement change rule of the roof rock stratum by using the drilling field arranged by the auxiliary transportation crossheading and the return air crossheading.
Preferably, the method for designing the grid-shaped drill site drilling holes comprises the following steps:
1) determining the horizon of the roof structure to be studied, i.e. determining the vertical height of the borehole, and equally dividing the vertical height to obtain the height H of the horizon of the roofnWhich isWhere n is 1, 2, 3 … … i: and H2=2H1、H3=3H1......Hi=iH1The unit m;
2) determining the distance L between the initial drilling hole or the initial fixed station position and the working surface open-off hole0The unit m; l is0The pressure step is smaller than the first pressure step of the working surface; l of the initial drilling of the auxiliary transportation crossheading and the return air crossheading0The values should remain consistent;
3) determining the horizontal distance l of adjacent drill holes of the return air crossheading, wherein the unit m and l are not more than the periodic collapse step l of the top plateZThe unit m is that for the auxiliary transportation crossheading fixed stations, the distance between two adjacent stations is nl, and the unit m is generally 1-3;
4) drilling D for auxiliary transportation crossheading fixed survey stationn,En,FnThe included angle between the axial direction of the tunnel and the axial direction of the tunnel is 90 degrees, and the elevation angle is theta; the determination formula of θ:the unit degree is 1, 2 and 3 … … i, wherein L is the horizontal distance of the drill hole in the solid coal in an overhanging mode, m is the unit, L is larger than the end overhanging distance of the working face, d is the width sum of the section coal pillar and the rubber transportation chute, m and H are the unitsnThe height of the top plate layer is taken as the height of the top plate layer;
5) displacement inclined hole A of return air crossheadingnThe included angle between the axial direction of the tunnel and the axial direction of the tunnel is alpha, unit degree, and the elevation angle is beta1Unit degree; displacement vertical hole BnThe included angle between the axial direction of the tunnel and the axial direction of the tunnel is 90 degrees;
displacement vertical hole BnElevation angle beta of0Unit degree according to the height H of observed roof layernThe unit m and the overhanging distance L of the drill hole in the solid coal are determined, the value of the unit m is larger than the inclined overhanging length of the working face, and the elevation angle of the vertical hole is displaced
Displacement inclined hole AnThe included angle alpha and unit degree with the axial direction of the roadway are determined according to the spacing L of adjacent displacement drill holes, the unit m and the overhanging distance L of the drill holes in the solid coal, wherein the value of L is larger than that of the unit mThe working face inclines to the length of the suspended roof, and the included angle between the displacement inclined hole and the axial direction of the roadwayOr
Displacement inclined hole AnElevation angle beta1Unit degree according to the height H of observed roof layernThe unit m and the overhanging distance L of the drill hole in the solid coal, the unit m and the interval L of the adjacent displacement drill holes are determined, the value of L is larger than the inclined overhanging length of the working face, and the elevation angle of the displacement inclined holen=1~3。
Preferably, the displacement bore hole in step S1 is determined according to the observed roof strata structure horizon; the peeping drill holes are arranged one by one and are consistent with the hole positions of the maximum displacement drill holes.
Preferably, in step S2, the fracture depth is obtained by observing the fracture condition of the rock strata in each borehole and performing data acquisition, the vertical horizon height and the lateral overhanging distance of the fracture roof, that is, the horizontal distance from the coal pillar side, are calculated, and the fracture roof structure in the working face heading direction and the fracture roof structure in the inclination direction are obtained by comprehensive analysis;
and a displacement monitoring device is arranged in each displacement drill hole in the drill field in which the auxiliary transportation crossheading and the return air crossheading are arranged, so that the change of rock stratum displacement in the drill hole is monitored.
Preferably, in step S2, the borehole peeper is used to observe the fracture of the rock formation in the borehole.
Compared with the prior art, the invention has the beneficial effects that: (1) the invention provides a method for actually measuring a shallow-buried single-key-layer net drilling field, which is a coupling analysis method combining field drilling displacement monitoring, drilling peeping and physical simulation. Compared with the prior art, the acquired characteristic data volume of the top plate movement is large, the data area is wide, and the characteristic data volume not only comprises the space position of the top plate breakage and the displacement of the top plate sinking, but also comprises the strength and the range of the breakage. The structural characteristics of the motion of the top plate of the shallow buried single key layer can be more comprehensively disclosed.
(2) In the invention, the drilling of the auxiliary transportation crossheading can realize real-time monitoring of the whole process from before mining to after mining of a working face, and the existing observation requirements on roof overlying strata caving zones and fissure zones are met; the advanced drilling of the return air crossheading is used for monitoring the information of the overtime breakage or movement of the top plate, and can meet the important information source of early warning and forecast of the pressure of the working face in the prior art.
Drawings
FIG. 1 is a schematic view of a drilling arrangement trend section of a working face return air gateway grid-shaped drilling site of the invention;
FIG. 2 is a schematic view of the arrangement section of the fixed measuring station in the invention;
FIG. 3 is a schematic representation of the borehole inclination profile of the stationary survey station of the present invention;
FIG. 4a is a schematic perspective view of a displaced vertical hole top plate drilling arrangement of the present invention;
FIG. 4b is a schematic perspective view of a displaced angled hole roof drilling arrangement of the present invention;
FIG. 5 is a diagram of the layout of the boreholes in a grid-like drill site of the example 22201 work surface;
FIG. 6a shows three station positions in an exemplary embodiment of an auxiliary transport crossheading profile;
FIG. 6b is a schematic cross-sectional view of an exemplary embodiment of an auxiliary running gate hole inclination measurement;
FIG. 7a is a sectional view of the return air crossheading hole profile of the embodiment;
FIG. 7b is a cross-sectional view of an exemplary return air channeling hole profile;
FIG. 7c is a schematic view of the displacement slant holes of examples A3 to A8;
FIG. 7d is a schematic view of the displaced vertical bores of examples B1-B6;
FIG. 8 shows the results of a borehole peeping at station I according to the embodiment;
FIG. 9 is a schematic view of an embodiment of top plate failure along a trend;
FIG. 10a is a schematic view of a top plate before first pressing according to an embodiment;
FIG. 10b is a schematic diagram of the top plate structure during initial pressing according to the embodiment;
FIG. 11a is the top plate structure of the embodiment in the 1 st cycle of pressing;
FIG. 11b shows the structure of the top plate in the 2 nd cycle of pressing according to the embodiment.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying fig. 1-11b, but it should be understood that the scope of the present invention is not limited to the specific embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The grid-shaped drilling site actual measurement analysis method for the shallow-buried single-key-layer stope overlying strata structure is reliable in data source and analysis result and good in effect. The invention adopts the following technical scheme:
in order to systematically master the breaking motion process of a top plate of a working face of a shallow-buried single key layer, a plurality of groups of drill holes are designed and constructed in advance in an auxiliary transportation crossheading and a return air crossheading of the working face respectively (the working face of a shallow-buried coal layer adopts three-lane arrangement, namely a transportation crossheading, an auxiliary transportation crossheading and a return air crossheading respectively), and a grid-shaped distributed drill site is formed in space (figure 1). Due to the limitation of underground working face mining and working environment, factors such as engineering construction cost and observation engineering quantity are considered, the selection of the number of latticed drill holes is not limited, the construction site and the number are determined according to the observation purpose, and a latticed drill site schematic diagram of the return air crossheading is shown in figure 1.
(2) Design principle of latticed drilling holes:
1) the method comprises the steps of determining the structural position of a top plate to be researched, namely determining the vertical height of a drill hole, and determining by combining a comprehensive drilling histogram of a working face to be researched, wherein the principle is that the maximum vertical height of the drill hole needs to exceed the top boundary (generally 4-6 times of mining height) of an old top key layer capable of forming a hinged structure, and the position of each top plate is determined according to 3 equal parts.
Such as H in FIG. 11,H2,H3...HnWherein n is 1, 2, 3 … … i. General selection of H2=2H1、H3=3H1...Hi=iH1The unit m.
The determination principle mainly considers the following aspects: the buried depth of the working face, the mining height, the thickness of the direct roof and the old roof and the lithology. These conditions can be obtained from the measured basic data such as a comprehensive drilling histogram on the working face. Secondly, combining engineering practice analogy and theoretical analysis to determine the height of the observed horizon of the roof structure.
According to the research experience of the professor in Huang Qing Xiang on shallow coal seam stopes, the vertical height of a drill hole is generally 4-6 times of the mining height. Wherein, 2-3 times are equivalent direct tops, 3-6 times are old tops, and the observation layer can be generally divided into 2-3 layers.
2) Distance L between initial drilling hole or measuring station position and working surface open-off hole0The unit m is used for obtaining the range of the step pitch of the first pressure of the working face, L according to the existing methods such as theoretical research results, engineering practice analogy and the like0Should be smaller than the first press step of the working surface. Also, L of the primary drillings of the auxiliary and return air chutes0The values are as consistent as possible.
3) The horizontal distance l, in m, of the adjacent boreholes in the return air gateway is shown in fig. 1. Referring to engineering analogy and theoretical research results, the period collapse step length l is not more than that of the top platezThe unit m. For the auxiliary transportation crossheading fixed stations, the distance between two adjacent stations is nl, the unit m is m, generally n is 1-3, and 3l is given in fig. 2. The fixed survey station must be placed in the secondary transport crossheading because the secondary transport crossheading can satisfy the overall process monitoring and cannot be observed when the working face pushes through the return air crossheading. The drilling holes of the fixed measuring station comprise a displacement drilling hole and a peeping drilling hole, and the displacement drilling hole is determined according to the structural position of the observed roof rock stratum; however, the peep hole is typically arranged one in line with the maximum displacement hole position. The schematic view of the bore hole of the fixed station running along the working surface is shown in fig. 2.
4) Displacement drilling D of auxiliary transportation crossheading fixed measuring stationn,En,FnThe included angle between the axial direction of the roadway and the axial direction of the roadway is 90 degrees, and the elevation angle is theta and unit degrees. The determination formula of θ:the unit ° where n is 1, 2, 3 … … i, L is the horizontal distance that the bore hole overhangs in the solid coal, m is the unit generally greater than the face end overhang, and d is the sum of the widths of the section coal pillar and the glue-transporting chute, m. If there are three boreholes in each station, the trend diagram is shown in fig. 3.
5) The drill holes designed in the return air crossheading are divided into vertical holes and inclined holes according to the inclination angles of the drill holes and a working surface, and are divided into vertical (inclined) displacement holes and vertical (inclined) peeping holes according to functions, the vertical holes and the inclined holes are on the same surface, the three-dimensional schematic diagram of the drill holes is shown in figure 4, and the vertical holes and the inclined holes are crossed to form a net. Inclined hole (A)1,A2,A3...Ai) The included angle between the axial direction of the tunnel and the axial direction of the tunnel is alpha and unit degrees, and the elevation angle is beta and unit degrees; vertical hole (B)1,B2,B3...Bi) The included angle between the axial direction of the peeping inclined hole and the axial direction of the roadway is 90 degrees, the horizontal distance between the peeping inclined hole and the displacement inclined hole is a, and the a is generally 0.5m by combining engineering practice and construction safety conditions; and in the same way, calculating to obtain the elevation angle of the vertical hole and the horizontal plane. The location of the bore A, B and the C opening from the floor is determined by the particular roadway section size and the drilling conditions.
6) Displacement vertical hole BnElevation angle beta of0Unit degree according to the height H of observed top layernThe overhanging distance L (unit, m) of the drill hole and the (unit, m) in the solid coal are determined, and similarly, the L is generally larger than the inclined overhanging length of the working face and the elevation angle of the vertical hole
7) Displacement inclined hole AnThe included angle alpha (unit, degree) with the axial direction of the roadway can be determined according to the distance L (unit, m) between adjacent displacement drill holes and the overhanging distance L (unit, m) of the drill holes in solid coal, and similarly, the value of L is generally larger than the inclined overhanging length of the working face, and the included angle alpha (unit, degree) between the displacement inclined holes and the axial direction of the roadway is shown in the schematic diagram of FIG. 4
8) Displacement inclined hole AnElevation angle beta1(unit ofAnd degree) can be determined according to the height H of the observed top plate layernThe overhanging distance L (unit, m) of the drill hole and the adjacent displacement drill hole in the solid coal and the distance L (unit, m) of the adjacent displacement drill hole are determined, and similarly, the value of L is generally larger than the inclined overhanging length of the working face, and the elevation angle of the displacement inclined hole shown in the schematic diagram of FIG. 4In this case, n is 3.
(3) The method for determining the top plate breaking position comprises the following steps: actually measuring the displacement change rule and the breaking motion track of the top plate rock stratum by using an observation drill site arranged by an auxiliary transportation crossheading and a return air crossheading; and observing the breakage condition of the rock stratum in the drill hole by using a drill hole peeping instrument. The YCJ90/360 type mining borehole logging analyzer is selected for peeping observation, the instrument can realize one-time acquisition of video, borehole azimuth angle and inclination angle data, the fracture depth is obtained by utilizing post-processing software, and the vertical horizon height and the lateral overhanging distance (the horizontal distance from the coal pillar side) of the fracture roof are calculated; and comprehensively analyzing to obtain the broken roof structure in the working face trend direction and the broken roof structure in the inclination direction.
(4) The top plate displacement actual measurement method comprises the following steps: in the displacement drilling hole of the design scheme, a mechanical top plate multipoint displacement meter is arranged to observe the rock mass displacement of each layer. The displacement of different levels of the top plate takes a bottom plate fixed point corresponding to a heavy hammer of the displacement meter as an initial value, a purchased measuring rod is adopted for reading, a positive value indicates that the steel wire is pulled in, and a negative value indicates that the steel wire is spitted out.
The innovation points of the invention are as follows:
(1) the actual measurement technology of the latticed drilling site of the top plate structure form and the movement process of the shallow buried single key layer is developed. The roof structure form and the motion rule are important scientific bases for building the roof structure and determining the working resistance of the support, but the field actual measurement of the roof structure and the form characteristics of the shallow coal seam at home and abroad is blank. The invention provides a shallow buried single key layer grid-shaped drilling site actual measurement technology, which is characterized in that a plurality of groups of drill holes are constructed on an auxiliary transportation roadway and an air return roadway in advance of a working surface, the drill holes are distributed in a grid shape in space, and a multi-point displacement meter is arranged in each drill hole by adopting drill hole peeping and mounting to obtain characteristic data and phenomena, so that the structural form and the motion process of a top plate are analyzed.
(2) The drill sites proposed by the patent of the invention are distributed in a grid shape in space, wherein: the auxiliary transportation roadway can realize real-time monitoring of the whole process of working face stoping (the whole process from before mining to after mining of the working face), reveal the space-time relation between stope roof structure motion and incoming pressure, and verify the size and form of the head area of the working face tending to break; the advanced drilling of the return air crossheading is to obtain the monitoring of the overtime breakage or movement information of the top plate and use the monitoring as the information of early warning and forecast of the pressure of the working face.
Engineering examples
According to the design content of the invention patent, the field construction and observation are carried out on the working surface of the hilly loess coal mine 22201 in the southern Shen mining area. 22201 the average thickness of the coal seam of the working face is 8.0m, the mining height is 6m, the inclination angle of the coal seam is 1-2 degrees, and the average buried depth is 76 m. The actual measurement of the downhole data is carried out for about 60 days, and the initial pressure of the 22201 working face and the data of the multipoint displacement meter with 6 times of periodic pressure are recorded together with the peeping video of the drill hole. The roof sinking rule of the initial pressure and the periodic pressure is obtained by analyzing the field measured data. Since the movement of the top plate is mainly reflected by the displacement in the vertical direction, the multi-point displacement counting data in the drill hole is mainly based on the vertical displacement.
(1) Latticed borehole design
The drilling arrangement of the secondary transport gateway fig. 6a is a cross-section along the direction of advancement of the working surface (secondary transport gateway) and fig. 6b is a cross-section along the direction of advancement of the working surface (open eye).
The return air channeling is provided with 19 drill holes in total, wherein the drill holes comprise 11 inclined holes (containing 3 peepholes) and 8 vertical holes, and the vertical holes and the inclined holes are on the same surface, as shown in fig. 7 a. The vertical holes and the inclined holes are positioned on the same measuring surface, the inclination angle of the measuring surface is 56 degrees (figure 7b), the vertical holes and the inclined holes are crossed to form a net shape, and the horizontal displacement and the vertical displacement of the measuring points are calculated. Inclined hole (A)1~A8) The included angle between the axial direction of the tunnel and the axial direction of the tunnel is 34 degrees, and the elevation angle is 40 degrees; the horizontal distance between the peeping inclined hole and the displacement inclined hole is 0.5m (see figure 7 b); vertical hole (B)1~B8) The elevation angle to the horizontal is 56 (see fig. 7 d). Distance between the location of the bore A, B and the opening of the CThe position of the hole C is determined according to specific construction conditions, the hole C is parallel to the hole A, and the horizontal distance is 0.5 m. The specific parameters are shown in Table 1.
Table 122201 table of drilling information for face placement
(2) Roof fracture characteristic borehole peeping
Through the drilling peeking analysis of the I measuring station and the II measuring station, the breaking motion rules of the top plates at different positions are as follows:
(1) when the working face is pushed to 32m, the top plate is pressed for the first time, and the position below 10m in the position 5m in front of the coal wall is subjected to forward displacement motion, which indicates that the movement of the top plate is ahead of the pressure of the working face. When the working surface is advanced to 36.6m, the initial pressing is finished, and the pressing duration is 4.6 m. At this point, a roof break occurred at a level of 24.4m above the coal wall (side overhang 19m), see FIG. 8 (a). The drill hole peeking shows that the top plate breaking motion is 4.6m ahead of the coal wall (namely the top plate breaking motion is 4.6m behind the incoming pressure) during the initial incoming pressure of the top plate, the support is pushed to the breaking line and then moves stably, and the incoming pressure is finished.
(2) The working face is pushed to 45.4-46.6 m, and during the 1 st period of pressure coming, the top plate 8.4m and 6m behind the coal wall of the working face (6.5 m in lateral suspension) collapses, as shown in fig. 8 (b); the 22.1m horizon (15 m lateral overhang) formation broke, see fig. 8 (c). The working face top plate is hysteretic. From D1And (4) continuously and actually measuring the drilled holes to obtain the caving step of the suspended ceiling of the horizon end head below 10m by about 8 m.
(3) During the 3 rd cycle of pressure, the roof completely collapsed at the 4.8m level (fig. 8(d)), the 9.3m level (fig. 8(e)) and the 16.2m level (fig. 8(f)) behind the working face coal wall at 33 m.
(4) The working face top plate tendency breaking rule is obtained by counting the positions of cracks, separation layers or collapse in the holes D, E and F of the fixed measuring station, as shown in fig. 9. The 10m, 20m and 30m layers of the top plate are gradually collapsed from bottom to top, and an arc-shaped breaking form is formed in the end area.
And (3) comprehensively observing the result to obtain the height of the overlying strata caving zone of about 16m, wherein the position of the hinged rock stratum is 16-30 m, the top plate has step sinking, a step rock beam structure can be formed, and the step sinking amount is about 1.7 m. The end suspended roof generally collapses about 8m behind the suspended coal wall, the step distance of roof collapse is about 8m, and the roof collapse from bottom to top forms an arc-shaped fracture along the trend.
(2) Top plate structure forming and moving process
And obtaining the structural formation and motion process of the top plate during the initial pressure and the periodic pressure of the working surface according to the displacement and peeking of the latticed drilling top plate.
1) Formation and motion process of primary top plate pressing structure
Before the initial pressing, the top plate 10m in front of the working surface is subjected to advanced overall deflection deformation, but is not broken. During the initial pressure, the top plate 10m in the position 5m in front of the coal wall sinks and is obviously increased (to 0.8m), and the advanced breakage occurs. The formation and movement process of the top plate 'asymmetric three-hinged arch' structure during the initial pressing is shown in figure 10.
2) Periodic coming pressure top plate structure forming and motion process
According to the actual measurement of a drill hole, the working face is pressed for the 1 st period, the top plate is broken 5-8 m ahead of the coal wall, the top plate at the position of 16-20 m behind the working face moves in a large range, and the movement of the top plate at the high position has certain hysteresis, as shown in fig. 11 a. When the working face is pressed for the 2 nd period, a larger crack is generated at the position of 25m in the position 4m in front of the working face (from the return air crossheading C)1Advanced peephole), the broken layer of the top plate reaches 25-30 m, as shown in FIG. 11 b. The hinged position of the top plate is gradually moved upwards to 16-30 m from 10-20 m.
(3) Temporal-spatial relationship between movement of top plate structure and pressure
The roof displacement and the drilling peeking of the auxiliary transportation crossheading and the return air crossheading are carried out, and the time-space relation between the roof structure rotary motion formed by periodically breaking the old roof and the pressure of the working face is as follows:
1) before coming to press: along with the advance of the working face, the bending moment of the old roof at the position 5-8 m ahead of the coal wall reaches the limit state, and the old roof is broken (obvious cracks are observed by drilling holes). At the moment, the working surface equivalent direct roof is not broken, the upper old roof can be supported, the working surface can be pressed in the future, and the old roof is stable.
2) Starting to press: when the working face is pushed to a position 3-4 m away from the advanced fracture line, the old top structure block starts to perform rotary motion, the stability of the direct top is reduced, the supporting capacity of the old top is reduced, the stability of the old top structure is reduced, and the pressure starts to be applied.
3) When pressure is applied: when the working face is pushed to the position near the lower part of the old top fracture line, the old top fracture is intensified, large rotary sinking old top structure steps sink, the dynamic load is increased, and the working face is pressed.
After the pressure is applied: and after the working face pushes the position of the fracture line to be about 4-6 m, the working face bracket enters the position below the new overhanging equivalent direct roof, the pressure of the top plate is reduced, and the pressing of the working face is finished.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (4)
1. A grid-shaped actual measurement method for a shallow-buried single-key-layer stope overlying rock structure is characterized by comprising the following steps:
s1, respectively arranging a plurality of groups of drill holes on an auxiliary transportation crossheading and a return air crossheading of a working face, wherein the specific arrangement method is as follows;
a plurality of fixed measuring stations are arranged in the auxiliary transportation crossheading, and the drill holes of the fixed measuring stations comprise displacement drill holes Dn,En,FnAnd a peep bore parallel to the displacement bore FnSetting;
the drill holes in the return air crossheading are divided into vertical holes and inclined holes according to the inclination angles of the drill holes and the working surface, and the vertical holes and the inclined holes are divided into displacement inclined holes A according to functionsnDisplacement vertical hole BnAnd peep inclined hole CnWherein n is 1, 2, 3 … … i: what is needed isThe displacement vertical hole BnAnd the displacement inclined hole AnLocated in the same plane and displaced vertical holes BnAnd a displacement inclined hole AnCrossing to form a net shape; peep inclined hole CnIs arranged parallel to the maximum displacement inclined hole and is used for peeping the inclined hole CnThe horizontal spacing from the corresponding maximum displacement inclined hole is a, unit m;
displacement drilling D for fixing measuring station in auxiliary transportation crossheadingn,En,FnAnd displacement inclined hole A in peeping hole and return air crossheadingnDisplacement vertical hole BnAnd peep inclined hole CnTogether forming a grid-like drill site borehole, wherein n is 1, 2, 3 … … i;
the design method of the grid-shaped drilling site comprises the following steps:
1) determining the horizon of the roof structure to be studied, i.e. determining the vertical height of the borehole, and equally dividing the vertical height to obtain the height H of the horizon of the roofnWherein n is 1, 2, 3 … … i: and H2=2H1、H3=3H1......Hi=iH1The unit m;
2) determining the distance L between the initial drilling hole or the initial fixed station position and the working surface open-off hole0The unit m; l is0The pressure step is smaller than the first pressure step of the working surface; l of the initial drilling of the auxiliary transportation crossheading and the return air crossheading0The values should remain consistent;
3) determining the horizontal distance l of adjacent drill holes of the return air crossheading, wherein the unit m and l are not more than the periodic collapse step l of the top plateZUnit m, for the fixed stations of the auxiliary transport crossheading, the distance between two adjacent stations is nlZ,n=1-3,lZThe number is the periodic pressure step distance of the working face, and the unit is m;
4) drilling D for auxiliary transportation crossheading fixed survey stationn,En,FnThe included angle between the axial direction of the tunnel and the axial direction of the tunnel is 90 degrees, and the elevation angle is theta; the determination formula of θ:the unit degree is n is 1, 2 and 3 … … i, wherein L is the horizontal distance of the drill hole in the solid coal in an overhanging mode, and the unit m is larger than the end overhang distance of the working faceD is the sum of the widths of the sectional coal pillar and the rubber transportation crossheading in the unit of m and HnThe height of the top plate layer is taken as the height of the top plate layer;
5) displacement inclined hole A of return air crossheadingnThe included angle between the axial direction of the tunnel and the axial direction of the tunnel is alpha, unit degree, and the elevation angle is beta1Unit degree; displacement vertical hole BnThe included angle between the axial direction of the tunnel and the axial direction of the tunnel is 90 degrees;
displacement vertical hole BnElevation angle beta of0Unit degree according to the height H of observed roof layernThe unit m and the overhanging distance L of the drill hole in the solid coal are determined, the value of the unit m is larger than the inclined overhanging length of the working face, and the elevation angle of the vertical hole is displaced
Displacement inclined hole AnThe included angle alpha and unit degree with the axial direction of the roadway are determined according to the spacing L of adjacent displacement drill holes, the unit m and the overhanging distance L of the drill holes in the solid coal, the unit m is determined, the value of L is larger than the inclined overhanging length of the working face, and the included angle between the displacement inclined holes and the axial direction of the roadwayOr
Displacement inclined hole AnElevation angle beta1Unit degree according to the height H of observed roof layernThe unit m and the overhanging distance L of the drill hole in the solid coal, the unit m and the interval L of the adjacent displacement drill holes are determined, the value of L is larger than the inclined overhanging length of the working face, and the elevation angle of the displacement inclined hole
And S2, actually measuring the broken movement track and the displacement change rule of the roof rock stratum by using the drilling field arranged by the auxiliary transportation crossheading and the return air crossheading.
2. The method for actually measuring the grid-shaped drill site of the shallow-buried single-key-layer stope overburden rock structure as claimed in claim 1, wherein the displacement drill hole in the step S1 is determined according to the observed roof rock structure horizon; the peeping drill holes are arranged one by one and are consistent with the hole positions of the maximum displacement drill holes.
3. The method for actually measuring the grid-shaped drill site of the shallow-buried single-key-layer stope overburden rock structure as claimed in claim 1, wherein in the step S2, the breaking depth is obtained by observing the breaking condition of rock strata in each drill hole and acquiring data, the vertical layer height and the lateral overhanging distance of a broken roof, namely the horizontal distance from the side of a coal pillar, are calculated, and the broken roof structure in the working face trend direction and the broken roof structure in the inclined direction are obtained by comprehensive analysis;
and a displacement monitoring device is arranged in each displacement drill hole in the drill field in which the auxiliary transportation crossheading and the return air crossheading are arranged, so that the change of rock stratum displacement in the drill hole is monitored.
4. The method for actually measuring a grid-shaped drill site of a shallow-buried single-key-layer stope overburden rock structure as claimed in claim 1, wherein a borehole peeping instrument is adopted to observe the fracture condition of a rock stratum in a borehole in the step S2.
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