Goaf rapid stabilization method based on mining area stratum stability investigation
Technical Field
The invention relates to the field of coal mining, in particular to a goaf rapid stabilization method based on mining area stratum stability investigation.
Background
The coal energy always occupies more than 60% of the energy consumption of China, is an important rear shield of various industries in China, the annual coal mining amount of China occupies half of the total world coal mining amount, the adopted mining mode mainly comprises underground mining and surface mining, wherein the underground mining occupies about 90% of the yield, the underground mining colloquially constructs a plurality of large-diameter shafts from the ground to directly reach the coal seam, then a long-wall working surface is arranged, and the coal seam is transported to the ground through the shafts after being mined by adopting the comprehensive mechanical coal mining technology. The overlying strata can be damaged and sunk after the coal seam is mined, a collapse zone, a fracture zone and a bending sinking zone are generally generated, wherein the collapse zone and the fracture zone are close to the coal seam, and when the coal seam is shallow in burial depth or large in mining height, only the collapse zone and the fracture zone are generally generated. The collapse zone refers to a rock zone in which rock blocks are randomly piled after roof rock layers in the goaf collapse, and the rock blocks are crushed; the rock stratum in the fracture zone basically maintains the original layered distribution state, but longitudinal fractures exist, the rock stratum is broken, a masonry beam structure can be formed by key layers in the rock stratum, a certain gap is formed in the rock stratum in the fracture zone under the influence of the masonry beam structure, and the rock stratum beyond the fracture interface of the rock stratum is not broken, so that all gravity of the overlying rock stratum is not beneficial to acting on the collapse zone and the fracture zone, and the goaf remains to sink for a long time; the strata of the bending sink zone remains substantially in its original layered distribution and remains intact, except for the deflection sink.
The damage generated by coal mining reaches the ground surface, and when the ground surface is greatly submerged, the damage is mostly abandoned into a subsidence area, and when the ground surface is relatively small in subsidence degree, the damage can be restored by some reclamation means to be reused. The existing treatment mode for the coal mine goaf mainly comprises two modes, namely, only backfilling the earth surface and transmitting the residual subsidence of the underground rock stratum to the earth surface without consideration, wherein the condition is suitable for reclamation of farmlands, the goaf exists for a long time, and the residual subsidence is small. Secondly, grouting cement and other slurry are injected into the goaf through a grouting drilling hole to strengthen and fill the goaf, but the grouting drilling hole is large in construction quantity due to small grouting diffusion radius of the grouting drilling hole, and the problem of drilling fluid leakage easily occurs when the grouting drilling hole is constructed to a fracture zone, the grouting drilling hole is difficult to construct to a collapse zone, the grouting slurry is unfavorable for entering the collapse zone, the collapse zone is the largest root cause of residual subsidence, and the scheme for grouting the goaf is generally used for the situation of building construction of a ground surface.
The existing goaf treatment method is not considered on the stability during treatment, the treatment mode is single, the reason that the goaf is left to sink is not considered, and therefore not all treatment effects can be expected.
Disclosure of Invention
Aiming at the problem that the stability condition of the existing goaf treatment method is not considered in treatment, the stability condition of the goaf is firstly judged through the stratum exploration of the mining area, and then the goaf rapid stabilization is achieved according to the three-zone/two-zone characteristics of overlying strata and the targeted treatment measures of the goaf residual subsidence mechanism, in particular, the invention provides a goaf rapid stabilization method based on the stratum stability investigation of the mining area, which comprises the following steps:
a. determining the plane range of the goaf and the stratum development condition of the mining area;
b. constructing a first exploration drilling hole to obtain a stratum column of a mining area, and obtaining a position of a key layer based on a key layer theory;
preferably, in the step b, the mining area stratum column comprises the position, thickness and lithology characteristics of each stratum, and the mechanical parameters of each stratum are obtained through a mechanical experiment.
c. Constructing a second exploration drilling hole above the goaf to obtain the range of a collapse zone, a fracture zone and a bending sinking zone, selecting a grouting key layer in the bending sinking zone, and taking the contact surface between the grouting key layer and a rock stratum below the key layer as a subsequent grouting layer;
preferably, in the step c, an isolating layer with a certain thickness is reserved between the grouting key layer and the fracture zone.
d. Calculating the original elevation of the rock stratum under the grouting key layer according to the development condition of the stratum in the mining area and the column shape of the stratum in the mining area, and obtaining the actual elevation of the rock stratum under the grouting key layer through a second exploration drilling hole, wherein the difference value between the original elevation and the actual elevation is a first difference value; observing the sinking speed of the rock stratum below the grouting key layer by a rock stratum movement observation means;
e. determining the residual crushing expansion coefficient of the stratum of the collapse zone, calculating the final height of the collapse zone, and obtaining a second difference value by subtracting the final height of the collapse zone from the height of the original stratum of the collapse zone; if the difference value of the first difference value and the second difference value is in the set threshold range, and the observed sinking speed of the rock stratum is in the set threshold range, the goaf stability is good, otherwise, the follow-up steps are executed;
f. constructing a plurality of cutting holes to the goaf at intervals above the goaf inclined boundary along the goaf trend, and sequentially and vertically cutting off the rock stratum in the fracture zone and the collapse zone through the cutting holes along the goaf trend;
preferably, in the step f, two rows of cutting holes can be constructed on each side of the inclined boundary, and the two rows of cutting holes are staggered.
g. Grouting holes are constructed at intervals along the goaf trend, the grouting holes are constructed to grouting horizons, and the cutting work of the delayed cutting holes is grouting into the separation layer through the grouting holes so as to cover the rock blocks in the lower caving zone and the fracture zone.
Preferably, in step g, the grouting holes are arranged in groups, and each group is respectively arranged at two sides of the goaf inclined to the middle and is positioned in the range of the fracture interface of the rock stratum.
Preferably, after grouting filling is finished, determining whether the subsidence zone rock mass reaches the residual expansion coefficient by testing the elevation of the rock stratum below the grouting key layer.
Preferably, for the two-zone development mining area stratum, the step c is that a second exploration drilling hole is constructed above the goaf to obtain a collapse zone, a fracture zone and a bending sinking zone range; step d, calculating the original elevation of a certain key layer in the fracture zone according to the development condition of the stratum in the mining area and the stratum column of the mining area, and obtaining the actual elevation of the key layer through a second exploration drilling hole, wherein the difference value between the original elevation and the actual elevation is a first difference value; observing the sinking speed of the key layer by a rock stratum movement observation means; and g, tamping construction is carried out on the ground by adopting a tamping method and/or a compacting method.
Further, after the compaction construction is finished, whether the crushed rock mass of the subsided zone reaches the residual crushing expansion coefficient is determined by measuring the elevation of the observed key layer.
The invention has the following advantages: 1. according to the invention, rock strata in the goaf and rock strata outside the boundary of the goaf are disconnected through construction cutting and drilling, so that a masonry beam structure between rock strata in the same rock stratum in a fracture zone is unstably dropped, the rock strata in the same rock stratum are uniformly sunk, and gaps/fractures of the rock strata in the fracture zone are eliminated; after the brickwork Liang Shiwen, all gravity of the fracture zone can act on the caving zone, so that compression of the rock mass of the caving zone is accelerated.
2. On the basis of the invention point 1, the crushed rock in the goaf is compressed as soon as possible by combining the traditional tamping construction for the two developed strata after mining so as to reach the residual crushing expansion coefficient as soon as possible and reach stability as soon as possible. For the three-zone development stratum after the mining, the space generated after the brickwork Liang Shiwen is transferred to the lower part of the grouting key layer, the asynchronous sinking of the grouting key layer and the stratum below the grouting key layer is generated, the time of capturing through grouting drilling and grouting is realized, and separation layer grouting is realized, so that the grouting pressure is beneficial to compressing broken rock blocks in a goaf as soon as possible to enable the broken rock blocks to reach the residual expansion coefficient as soon as possible, and the broken rock blocks are as fast as possible stable.
3. The invention also provides a mining area stratum stability investigation method, the underground rock stratum is explored by constructing a first exploration drilling hole and a second exploration drilling hole, the subsidence of the goaf is determined by combining the stratum development condition, and the problem that the actual subsidence amount cannot be determined through earth surface subsidence observation after mining (the earth surface is greatly influenced by external environment) is solved.
Drawings
The invention, together with a further understanding of the many of its attendant advantages, will be more fully appreciated by reference to the following detailed description, when considered in connection with the accompanying drawings, which are included to provide a further understanding of the invention, and the accompanying illustrative embodiments of the invention and description thereof serve to explain and do not constitute a limitation of the invention, wherein:
FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention in an exploration borehole arrangement;
FIG. 2 is a schematic cross-sectional view of a goaf rapid stabilization method according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of a second illustrative survey borehole arrangement;
FIG. 4 is a schematic cross-sectional view of a method for rapidly stabilizing goaf in accordance with an embodiment of the present invention;
description of the drawings: 1-coal seam; 2-goaf/caving zone; 3-a fracture zone; 4-bending the sinkage belt; 5-loosening layer; 6-a first survey borehole; 7-a second survey borehole; 8-cutting and drilling holes; 9-grouting and drilling; 10-grouting a key layer; 11-delamination/grouting layer; 12-isolating layer; 13-formation fracture interface.
Detailed Description
For a better understanding of the technical content of the present invention, specific examples are set forth below, along with the accompanying drawings. Aspects of the invention are described herein with reference to the drawings, in which there are shown many illustrative embodiments. The embodiments of the present invention are not limited to the embodiments described in the drawings. It is to be understood that this invention is capable of being carried out by any of the various concepts and embodiments described above and as such described in detail below, since the disclosed concepts and embodiments are not limited to any implementation. Additionally, some aspects of the disclosure may be used alone or in any suitable combination with other aspects of the disclosure.
Example 1
Aiming at the condition that rock stratum is broken until the ground surface after coal seam exploitation, namely the condition that the stratum after exploitation only comprises a collapse zone and a fracture zone but does not comprise a bending sinking zone, as shown in figures 1-2, the goaf rapid stabilization method based on mining area stratum stability investigation comprises the following steps:
determining the plane range of the goaf 2, namely the exploitation range of the original working surface, including the width and the stoping length, through original geological data and/or by adopting a geophysical prospecting method (including but not limited to a controllable source audio magnetotelluric method and a micro-motion detection method); simultaneously acquiring stratum development conditions such as extension, inclination and the like of stratum in mining area;
constructing a first exploration drilling 6 at an unaerated position (the coal seam 1 right below the goaf 2 is not mined and maintains an original elastic state) away from the goaf 2, and obtaining a mining area stratum column, wherein the mining area stratum column at least comprises the position, thickness and lithology characteristics of each rock stratum and the range of a loose layer 5, mechanical parameters of each rock stratum are obtained through a mechanical experiment, and the position of a key layer is obtained based on a key layer theory;
constructing a second exploration drilling 7 above the goaf through theoretical calculation or simulation means (physical simulation and numerical simulation) to obtain the ranges of the collapse zone 2 and the fracture zone 3;
according to stratum development conditions such as the extension and the inclination of stratum in a mining area, based on stratum columns acquired by a first exploration drilling hole 6, the original elevation of a certain key layer in a fracture zone (preferably the uppermost key layer in the fracture zone, namely a main key layer) is calculated, the actual elevation of the key layer is acquired by a second exploration drilling hole 7, and the difference value between the original elevation and the actual elevation is a first difference value; observing the sinking speed of the key layer by a rock stratum movement observation means;
determining a residual crushing expansion coefficient of the stratum of the collapse zone based on the characteristics of the stratum corresponding to the collapse zone 2, calculating the final height of the collapse zone (when the residual crushing expansion coefficient is reached), and subtracting the final height of the collapse zone from the original stratum of the collapse zone to obtain a second difference value; when the breaking expansion of the fracture zone is zero, namely the total thickness of the corresponding rock stratum of the fracture zone before and after the coal seam 1 is mined is unchanged, the whole mined stratum is stable when the sinking amount of the rock stratum in the fracture zone after the mining is the second difference value; if the difference value of the first difference value and the second difference value is in a set threshold range (30 cm is generally selected), and meanwhile, the observed sinking speed of the rock stratum is in the set threshold range (1 mm/d can be generally selected), the goaf has good stability, achieves an ideal stability level, and can be directly utilized on the ground; otherwise, executing the subsequent steps;
constructing a plurality of cutting holes 8 to the goaf 2 at intervals above the goaf inclined boundary along the goaf trend; two rows of cutting drilling holes 8 can be constructed on each side of the inclined boundary, and the two rows of cutting drilling holes 8 are staggered; sequentially and vertically cutting off rock strata in the collapse zone 2 and the fracture zone 3 along the trend through a cutting drilling hole 8 (by adopting hydraulic fracturing or blasting means), so that the rock strata in the goaf are disconnected from the rock strata outside the boundary of the goaf, and meanwhile, the masonry beam structure among the rock strata in the same rock stratum in the fracture zone 2 is instable and falls, and the rock strata in the same rock stratum are uniformly sunk;
the cutting work of the delayed cutting drilling hole 8 is about the distance of a direct bursting period breaking step distance, and tamping construction is carried out on the ground by adopting a tamping method and/or a compaction method, so that the rock blocks in the lower collapse zone 2 and the fracture zone 3 are pressed to enable the rock blocks in the collapse zone to reach the residual crushing expansion coefficient as soon as possible, the height direction of the rock blocks in the fracture zone is enabled to be free from crushing expansion as much as possible, and all rock layers are evenly sunk, namely, the goaf is enabled to be fast and stable.
After the compaction construction is finished, whether the crushed rock mass of the subsidence zone reaches the residual crushing expansion coefficient can be determined by measuring the elevation of the observed key layer.
According to the embodiment of the invention, the rock stratum in the goaf and the rock stratum outside the boundary of the goaf are disconnected by cutting off the rock stratum in the fracture zone and the rock stratum in the subsidence zone, so that the masonry beam structure among the rock masses in the same rock stratum in the fracture zone is instable and falls down, the rock masses in the same rock stratum are uniformly sunk, all gravity of the fracture zone can act on the subsidence zone after the masonry Liang Shiwen is conducted, compression of the rock masses in the subsidence zone is accelerated, meanwhile, the generated space can be transferred to the ground surface as soon as possible, the part of the space is prevented from being slowly transferred to the ground surface, and at the moment, the broken rock masses in the goaf can be compressed as soon as possible in combination with the traditional tamping construction so as to achieve residual expansion coefficients as soon as possible, and be stabilized as soon as possible, so that the ground utilization is conducted.
Example two
Aiming at the situation that rock stratum fracture does not reach the earth surface after coal seam exploitation, namely the situation that the stratum after exploitation comprises a collapse zone, a fracture zone and a bending subsidence zone, as shown in figures 3-4, the goaf rapid stabilization method based on mining area stratum stability investigation comprises the following steps:
determining the plane range of the goaf 2, namely the exploitation range of the original working surface, including the width and the stoping length of the original working surface, through original geological data and/or by adopting a geophysical prospecting method (including but not limited to a controllable source audio magnetotelluric method and a micro-motion detection method); simultaneously acquiring stratum development conditions such as extension, inclination and the like of stratum in mining area;
constructing a first exploration drilling 6 at an unaerated position (the coal seam 1 right below the goaf 2 is not mined and maintains an original elastic state) away from the goaf 2, and obtaining a mining area stratum column, wherein the mining area stratum column at least comprises the position, thickness and lithology characteristics of each rock stratum and the range of a loose layer 5, mechanical parameters of each rock stratum are obtained through a mechanical experiment, and a key layer position is obtained based on a key layer theory;
constructing a second exploration drilling 7 through theoretical calculation or simulation means (physical simulation and numerical simulation) or above a goaf, obtaining the ranges of a collapse zone 2, a fracture zone 3 and a bending subsidence zone 4, selecting a proper grouting key layer 10 in the bending subsidence zone 4, taking the contact surface between the grouting key layer 10 and a rock stratum below the grouting key layer as a subsequent grouting layer 11 (separation layer is generated after the contact surface is separated), and keeping an isolation layer 12 with a certain thickness between the grouting key layer 10 and the fracture zone;
according to stratum development conditions such as extension and inclination of stratum in a mining area, based on stratum columns acquired by a first exploration drilling hole 6, calculating an original elevation of the stratum under the grouting key layer 10, and acquiring an actual elevation of the stratum under the grouting key layer 10 through a second exploration drilling hole 7, wherein the difference value between the original elevation and the actual elevation is a first difference value; observing the sinking speed of the rock stratum under the grouting key layer 10 by a rock stratum movement observing means;
determining a residual crushing expansion coefficient of the stratum of the collapse zone based on the characteristics of the stratum corresponding to the collapse zone 2, calculating the final height of the collapse zone (when the residual crushing expansion coefficient is reached), and subtracting the final height of the collapse zone from the original stratum of the collapse zone to obtain a second difference value; when the broken expansion of the fracture zone and the bending subsidence zone is zero, namely the total thickness of the corresponding rock stratum of the fracture zone and the bending subsidence zone is unchanged before and after the coal seam 1 is mined, the whole mined stratum is stable when the rock stratum subsidence in the fracture zone and the bending subsidence zone after the mining is the second difference value; if the difference value of the first difference value and the second difference value is in a set threshold range (30 cm is generally selected), and meanwhile, the observed sinking speed of the rock stratum is in the set threshold range (1 mm/d is generally selected), the goaf has good stability, achieves an ideal stable level, and can be directly utilized on the ground; otherwise, executing the subsequent steps;
constructing a plurality of cutting holes 8 to the goaf 2 at intervals above the goaf inclined boundary along the goaf trend; two rows of cutting drilling holes 8 can be constructed on each side of the inclined boundary, and the two rows of cutting drilling holes 8 are staggered; sequentially and vertically cutting off rock strata in the collapse zone 2 and the fracture zone 3 along the trend through a cutting drilling hole 8 (by adopting hydraulic fracturing or blasting means), so that the rock strata in the goaf are disconnected from the rock strata outside the boundary of the goaf, and meanwhile, the masonry beam structure among the rock strata in the same rock stratum in the fracture zone 2 is instable and falls, and the rock strata in the same rock stratum are uniformly sunk;
constructing a plurality of groups of grouting drilling holes 9 along the trend of the goaf at intervals, wherein each group of grouting drilling holes 9 comprises two grouting drilling holes which are respectively arranged on two sides of the inclined middle part of the goaf and are positioned in the range of a rock stratum breaking interface 13, and the grouting drilling holes 9 are constructed to a grouting layer 11; the cutting work of the delayed cutting drilling holes 8 is about the distance of a direct bursting period breaking step distance, grouting is sequentially carried out in the separation layers 11 through each group of grouting drilling holes 9 along the trend, and the rock blocks in the lower caving zone 2 and the fracture zone 3 can be pressed and covered by grouting and filling so that the residual crushing expansion coefficient of the caving zone rock blocks is reached as soon as possible, the crushing expansion of the fracture zone rock blocks is avoided as much as possible in the height direction, and each rock layer is uniformly sunk, namely, the goaf is enabled to be fast and stable; and simultaneously, the grouting key layer 10 and the upper rock stratum thereof can be lifted by grouting filling.
After grouting filling is finished, whether the broken and expanded coefficients of the crushed zone rock blocks reach can be determined by testing the elevation of the rock stratum below the grouting key layer 10.
The separation layer grouting filling is generally suitable for the condition that the working face is filled while stoping, namely, filling is carried out while stoping. For old goaf conditions, goaf grouting is generally performed directly, because no delamination occurs, especially for a long time, unless extremely thick and hard rock formations are present in the formation. According to the embodiment of the invention, the rock stratum in the goaf and the rock stratum outside the boundary of the goaf are disconnected by cutting off the fracture zone and the rock stratum in the caving zone, so that the masonry beam structure between the rock masses in the same rock stratum in the fracture zone is instable and falls, the rock masses in the same rock stratum are uniformly sunk, a space (which can be regarded as exploitation of an extremely thin coal seam) generated after the masonry Liang Shiwen is transferred to the lower part of the grouting key layer, asynchronous sinking of the grouting key layer and the rock stratum below the grouting key layer is generated, grouting is realized by capturing the time of grouting through grouting drilling, and then the crushed rock masses in the goaf are compressed as soon as possible by grouting pressure to reach residual expansion coefficients as soon as possible, so that ground utilization is realized as soon as possible.
The foregoing description is, of course, merely illustrative of preferred embodiments of the present invention, and it should be understood that the present invention is not limited to the above-described embodiments, but is intended to cover all modifications, equivalents and obvious modifications falling within the spirit and scope of the present invention as defined by the appended claims.