CN113898410B - Deep coal seam mining floor rock stratum fracture distribution space-time evolution dynamic monitoring method - Google Patents
Deep coal seam mining floor rock stratum fracture distribution space-time evolution dynamic monitoring method Download PDFInfo
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- CN113898410B CN113898410B CN202111129836.8A CN202111129836A CN113898410B CN 113898410 B CN113898410 B CN 113898410B CN 202111129836 A CN202111129836 A CN 202111129836A CN 113898410 B CN113898410 B CN 113898410B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
- E21F17/18—Special adaptations of signalling or alarm devices
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices, or the like
- E21B33/138—Plastering the borehole wall; Injecting into the formation
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
Abstract
The invention provides a deep coal seam mining floor rock stratum fracture distribution space-time evolution dynamic monitoring method, which comprises the steps of firstly, according to regional engineering geology and hydrogeology conditions laid on a coal seam mining working face, designing a BOTDR system for mining the coal seam floor rock stratum fracture dynamic monitoring and testing site selection, and manufacturing and installing a metal cable-based distributed single-mode sensing optical cable; secondly, calibrating deformation consistency of the metal cable-based distributed single-mode sensing optical cable, the drilling filler and corresponding surrounding rocks, and respectively carrying out dynamic monitoring and data analysis on the strain data of the coal seam mining floor by adopting a BOTDR system and AV6419 ANALYER STANDARD analysis software; and finally, according to the judgment basis of the coal seam mining bottom plate rock stratum fracture, disclosing the time-space evolution characteristics of the mining bottom plate rock stratum damage distribution and the maximum damage depth of the mining bottom plate. The method can effectively and dynamically monitor the time-space evolution characteristics of the fracture of the mining coal seam floor rock stratum, and provides a basis for preventing and controlling the pressure-bearing water damage of the deep mining coal seam floor.
Description
Technical Field
The invention belongs to the field of coal mining, and particularly relates to a dynamic monitoring method for spatial and temporal evolution of deep coal seam mining floor rock stratum fracture distribution.
Background
At present, shallow resources in the middle and east mining areas of China are exhausted, and the deep mining mode is comprehensively entered. Deep mining is accompanied with high water pressure, high temperature, high ground pressure and under the condition of strong disturbance of deep mining, so that the deep coal seam mining faces huge safety challenge; particularly, high pressure-bearing water damage accidents frequently occur, and the safety exploitation of deep coal seams is seriously threatened. The essential condition for preventing and controlling the confined water of the deep coal seam floor is to scientifically and effectively find out the space-time distribution characteristics of the fracture of the rock stratum of the deep mining coal seam floor, thereby scientifically and effectively preventing and controlling the confined water damage. Therefore, the research on the time-space evolution characteristics of the fracture distribution of the deep coal seam mining floor rock stratum is necessary.
In the prior art, various methods based on analytical solutions, acquaintance material simulation, numerical simulation and the like are provided for the research of the time-space evolution characteristics of rock stratum fracture of a deep coal seam mining floor. However, research shows that the mining fracture process of the coal seam floor rock stratum is a 'pressure-tension-pressure' strain fracture process, and the strain magnitude scale of the coal seam floor rock stratum is small, so that the research method cannot realize dynamic measurement.
Disclosure of Invention
The invention aims to provide a dynamic monitoring method for the fracture distribution of a deep coal seam mining floor rock stratum through the spatial and temporal evolution, which can realize the dynamic monitoring of the fracture distribution of the deep coal seam mining floor rock stratum and provide basic parameters for the prevention and control of the pressure-bearing water damage of the deep coal seam mining floor. In order to realize the purpose, the invention adopts the following technical scheme:
a deep coal seam mining floor rock stratum fracture distribution space-time evolution dynamic monitoring method comprises the following steps:
(1) Drilling site selection and manufacturing of a distributed optical fiber sensor:
collecting engineering geological parameters and hydrogeological parameters of a project in a coal seam mining working face layout area, and then performing drilling site selection and manufacturing a distributed optical fiber sensor according to the geological parameters and the hydrogeological parameters;
(2) Obtaining core samples of each formation:
coring a bottom plate rock layer of a deep coal face to be monitored to obtain a coring sample of each rock layer, then determining the lithology of each rock layer of the bottom plate rock layer of the coal bed based on the coring samples of each rock layer, and measuring the rock physical mechanical parameters of different layers to obtain various physical mechanical parameters of different rock layers;
(3) Manufacturing a sample rock cylinder of each rock stratum:
determining the material proportion of the drilling filler corresponding to different rock stratums in the drilling process according to the lithology of each rock stratum and each physical and mechanical parameter of each rock stratum in the step (2), and then manufacturing sample rock cylinders corresponding to different rock stratums based on the proportion of the drilling filler;
(4) Calibrating the material ratio of the drilling filler corresponding to each rock stratum:
for the same rock stratum, checking the deformation consistency of the drilling filler and the surrounding rock based on the sample rock cylinder in the step (3) and the coring sample in the step (2) to adjust the material proportion of the drilling filler corresponding to different rock strata in the step (3), and finally obtaining the calibrated material proportion;
(5) Calibrating the distributed optical fiber sensor:
aiming at the same rock stratum, based on the sample rock cylinder with the ratio of the calibration materials in the step (4) and the distributed optical fiber sensor in the step (1), detecting the deformation consistency of the distributed optical fiber sensor and the surrounding rock, so as to adjust the distributed optical fiber sensor in the step (1) and finally obtain the calibrated distributed optical fiber sensor;
(6) Laying the distributed optical fiber sensor calibrated in the step (5):
(61) Selecting sites as required to form pores:
according to the drilling site selection scheme in the step (1), selecting two optical fiber monitoring distribution positions in a gas drainage roadway below a bottom plate of a working face of a research area, and then constructing a drill hole on a top plate of the gas drainage roadway, wherein the terminal of the drill hole keeps a preset distance from the bottom of a coal mining layer in the vertical direction;
(62) Manufacturing and laying a sensor embedded part:
respectively fixing the distributed optical fiber sensors calibrated in the step (5) on the outer walls of the mining high-pressure PVC pipes to obtain sensor embedded parts;
then pushing the sensor embedded part to the bottom of the hole from the hole opening, sealing the hole opening of the drilled hole, and embedding a plurality of layered grouting warning pipes in the hole opening of the drilled hole; wherein each layered grouting warning pipe is positioned in the drill hole; the liquid inlet end of each layered grouting warning pipe is positioned at the top of the corresponding rock stratum, and the liquid outlet end of each layered grouting warning pipe is positioned outside the drill hole;
(7) Layered filling (61) of the borehole:
based on the high-pressure PVC pipe, each layered grouting warning pipe and the drilling filler corresponding to each rock stratum calibrated in the step (4), performing layered filling on the drilling from bottom to top:
in the layered filling, when the liquid outlet end of the layered grouting warning pipe at the lower layer is full of the pipe for liquid outlet, the liquid outlet end is sealed, and then drilling filler corresponding to the next rock stratum is injected into the high-pressure PVC pipe;
(8) Dynamic monitoring and data analysis:
and (4) dynamically monitoring the strain data of the coal seam mining floor based on the distributed optical fiber sensor and the BOTDR system in the step (62), and analyzing the monitoring data based on AV6419 ANALYER STANDARD analysis software to obtain the damage distribution rule of the coal seam floor rock stratum and the maximum damage depth of the coal seam floor rock stratum under the mining influence.
Preferably, in the step (1), the engineering geological parameters comprise the thickness of the coal seam, the combination mode of the rock strata of the bottom plate of the coal seam and the burial depth of the coal seam; hydrogeological parameters include the distance of the coal seam from the floor aquifer, the physico-mechanical properties of the aquifer and the aquifer revealed by the borehole.
Preferably, the distributed fibre optic sensor is a metal cable based distributed single mode sensing optical cable.
Preferably, step (4) comprises:
(41) Respectively performing a uniaxial compression test and a uniaxial shear test on a core sample aiming at the same rock stratum; uniaxial compression test and uniaxial shear test of the sample rock cylinder;
(42) Comparing and analyzing test result data of the same type of test;
(43) Adjusting the material ratio of the drilling filler according to the comparative analysis data;
(44) And (5) repeating the steps (41) to (43) until the precision between the test result data of the sample rock pillar and the core sample reaches a preset value.
Preferably, step (5) specifically comprises:
(51) Manufacturing an optical cable-concrete test piece:
fixing the distributed optical fiber sensor in the step (1) at the central position of a PVC pipe fitting; injecting the drilling filler with the material ratio calibrated in the step (4) into the PVC pipe fitting and maintaining to obtain an optical cable-concrete test piece;
(52) Fixing two ends of the optical cable-concrete test piece on a test rack, loading the optical cable-concrete test piece step by a jack on the test rack, then acquiring test piece strain data of the optical cable-concrete test piece by a laser range finder, and recording the test piece strain data by a BOTDR system;
(53) Solving the strain data of the drilling filler based on the test loading data;
(54) Comparing the strain data of the test piece in the step (52) with the strain data of the filler in the step (53), and improving the distributed optical fiber sensor in the step (1) until the error is less than 10% when the error between the strain data of the test piece and the strain data of the filler in the drilled hole is more than 10%.
Preferably, in step (61), a fracture zone is formed in the bottom plate at a drill hole; the other borehole is a full floor formation location.
Preferably, in step (7), the hierarchical filling includes:
(71) Injecting the drilling filler with the material ratio calibrated in the step (4) into the high-pressure PVC pipe fitting, wherein the drilling filler corresponds to a rock stratum to be filled; the drilling filler flows from the inside of the high-pressure PVC pipe fitting to the top of the drilling hole and then returns slurry;
(72) When the hole layer corresponding to the lowest rock stratum is subjected to grouting and cross-layer grouting, the liquid outlet end of the layered grouting warning pipe corresponding to the lowest rock stratum is full of pipe liquid, the liquid outlet end is closed, and grouting is stopped; and (5) repeating the steps (71) to (72) until all hole layers corresponding to the rock stratum in the drill hole are filled.
Compared with the prior art, the invention has the advantages that: the method can be used for dynamically monitoring the fracture distribution of the deep coal seam mining floor rock stratum, and realizing the damage distribution rule of the coal seam floor rock stratum and the maximum damage depth of the coal seam floor rock stratum. Therefore, the method can accurately judge the thickness of the effective water-resisting layer of the coal seam mining bottom plate rock stratum, provides a basis for evaluating the water inrush danger of the deep coal seam mining bottom plate, and further develops a scientific and effective prevention and control scheme for water damage of the deep coal seam mining bottom plate, so that the safe mining of the deep coal seam is ensured.
Drawings
FIG. 1 is a flow chart of an embodiment of the method of the present invention;
FIG. 2 is a metal cable-based distributed single mode sensing optical cable;
FIG. 3 is a graph showing the relationship between frequency shift and strain of a metal cable-based distributed single-mode sensing optical cable;
FIG. 4 is a test chart of the deformation consistency of the optical cable and the filler;
FIG. 5 is a schematic diagram of monitoring coal seam floor strain using a BOTDR system;
FIG. 6 is complete floor strata mining fracture distribution spatiotemporal evolution monitoring data;
FIG. 7 is a graph of spatiotemporal evolution monitoring data of mining fracture distribution of a fault-containing floor rock formation;
FIG. 8 is a time-space evolution characteristic diagram of a coal seam mining floor strata strain fracture;
FIG. 9 is a schematic view of the maximum failure depth position of the completed baseplate;
FIG. 10 is a schematic view of the maximum failure depth position of the floor containing the fault zone;
FIG. 11 is a schematic view of monitoring borehole stratified grouting burying.
Detailed Description
The present invention will now be described in more detail with reference to the accompanying schematic drawings, in which preferred embodiments of the invention are shown, it being understood that one skilled in the art may modify the invention herein described while still achieving the advantageous effects of the invention. Accordingly, the following description should be construed as broadly as possible to those skilled in the art and not as limiting the invention.
As shown in fig. 1, the dynamic monitoring method for the fracture distribution spatiotemporal evolution of the deep coal seam mining floor rock stratum comprises the following steps (1) - (8), a mining process dynamic monitoring mode is carried out on a microstrain scale based on a distributed fiber bragg grating sensor, the extraction of the spatiotemporal evolution characteristics of the fracture of the deep coal seam mining floor rock stratum is effectively realized, and scientific and effective data support is provided for the prevention and control of the pressure-bearing water damage of the deep coal seam mining floor, and the method specifically comprises the following steps:
(1) And collecting geological and hydrogeological data of each mine in the mining area so as to carry out drilling site selection and manufacture the distributed optical fiber sensor.
The engineering geological parameters and the hydrogeological parameters of the coal seam mining working face layout area project are collected, then drilling site selection is carried out according to the geological parameters and the hydrogeological parameters, and the distributed optical fiber sensor is manufactured based on the Brillouin optical time domain reflection principle, the geological parameters and the hydrogeological parameters. The structure of the sensor is shown in fig. 2.
The engineering geological parameters comprise coal seam thickness, a combination mode of coal seam floor rock strata and coal seam burial depth; hydrogeological parameters include the distance of the coal seam from the floor aquifer, the physico-mechanical properties of the aquifer and the aquifer revealed by the borehole. The distributed optical fiber sensor adopts a metal cable-based distributed single-mode sensing optical cable.
The method comprises the following steps: the method comprises the steps of obtaining effective water-resisting layer thickness, coal seam burial depth, distance from the coal seam to an Ordovician limestone aquifer, thickness of a direct bottom plate of the coal seam, hardness degree of a rock layer of the direct bottom plate, information of a water-containing layer of a top bottom plate of the coal seam exposed by a drill hole and the like by adopting drilling, geophysical prospecting and in-situ monitoring methods, wherein the hardness degree of the rock layer of the bottom plate of the coal seam is obtained by an indoor rock mechanics experiment method.
The metal cable-based distributed single-mode sensing optical cable is composed of four parts, namely a high-strength PVC protective layer, six metal reinforcing ribs, an optical fiber protective coating and quartz optical fibers (shown in figure 2). In order to enhance the tensile property of the monitoring optical cable, six high-strength metal wires are used at the periphery of the optical fiber to protect the optical fiber in a ring-shaped weaving state, the distance between measuring points of the distributed optical fiber sensor is 0.005m, specifically, measuring points are recorded on the optical fiber, and the distance between the recorded measuring points is 0.005m on the optical fiber. The metal cable-based distributed single-mode sensing optical cable has a strain coefficient of 493MHz/%, which is a conventional G.652 single-mode optical fiber, at a detection wavelength of 1550 nm, and physical and mechanical parameters of the metal cable-based distributed single-mode sensing optical cable are shown in Table 1.
TABLE 1 metal cable-based distributed single-mode sensing optical cable physicomechanical parameters
| Diameter of optical cable (mm) | Optical fiber diameter (mm) | Tensile resistance (N) | Modulus of elasticity (GPa) | Basis weight (kg/km) | Working temperature (. Degree.C.) |
| 5.00 | 0.90 | 6500.00 | 42.00 | 38.00 | 0 ~ 80 |
The metal cable-based distributed single-mode sensing optical cable can be used under the condition of poor installation environment, and the calibration precision of the relationship between the frequency shift and the strain of the metal cable-based distributed single-mode sensing optical cable in a laboratory is shown in fig. 3.
And (5) calibrating the deformation consistency of the metal cable-based distributed single-mode sensing optical cable and the surrounding rock, which comprises the steps of (2) - (5).
(2) Core samples are obtained for each formation.
Coring a bottom rock layer of a deep coal face to be monitored to obtain a coring sample of each rock layer, then determining the lithology of each rock layer of the bottom rock layer of the coal layer (determining the combination property of the bottom rock layer of the coal layer) based on the coring samples of each rock layer, and measuring the rock physical mechanical parameters of different layers to obtain various physical mechanical parameters of different rock layers.
(3) Sample pillars of each rock layer were made.
And (3) determining the material proportion of the drilling filler corresponding to different rock stratums in the drilling process according to the lithology of each rock stratum and each physical and mechanical parameter of each rock stratum in the step (2), and then manufacturing sample rock cylinders corresponding to different rock stratums based on the proportion of the drilling filler. Namely, similar materials (drilling filling materials) are used for simulating and manufacturing a sample rock cylinder which is consistent with the lithology of each rock stratum and each physical and mechanical parameter. Wherein the tensile test sample is a cylinder with the diameter of 50mm and the height of 100 mm; the compression test sample is a cylinder with the diameter of 50mm and the height of 25 mm.
The specific process for determining the material ratio comprises the following steps: a, determining a filler material, and proportioning by mass proportion; b, preparing the drilling filler slurry in proportion, wherein the material curing time is more than 7 days.
(4) And (5) testing the deformation consistency of the drilling filler and the surrounding rock to calibrate the material proportion of the drilling filler corresponding to each rock stratum.
And (3) aiming at the same rock stratum, checking the deformation consistency of the drilling filler and the surrounding rock based on the sample rock cylinder in the step (3) and the core sample in the step (2), and comparing the stress-strain curves of the two samples to adjust the material proportion of the drilling filler corresponding to different rock strata in the step (3) so as to finally obtain the calibrated material proportion. The method comprises the following specific steps:
(41) Respectively carrying out a uniaxial compression test and a uniaxial shearing test on a core sample aiming at the same rock stratum; uniaxial compression test and uniaxial shear test of the sample rock cylinder.
(42) Comparing and analyzing test result data of the same type of test; i.e. the stress-strain curves of both were compared for the same type of test.
(43) And adjusting the material ratio of the drilling filler according to the comparative analysis data.
(44) And (5) repeating the steps (41) to (43) until the precision between the test result data of the sample rock cylinder and the core sample reaches a preset value.
(5) And (3) determining the deformation consistency between the metal cable-based distributed single-mode sensing optical cable and the borehole filler so as to calibrate the distributed optical fiber sensor, as shown in figure 4.
And (3) aiming at the same rock stratum, based on the sample rock cylinder with the ratio of the calibration materials in the step (4) and the distributed optical fiber sensor in the step (1), checking the deformation consistency of the distributed optical fiber sensor and the surrounding rock so as to adjust the distributed optical fiber sensor in the step (1) and finally obtain the calibrated distributed optical fiber sensor. The specific scheme is as follows:
(51) Manufacturing an optical cable-concrete test piece:
preparation of test materials: 2m of PVC pipe with the diameter of 180mm; a metal cable-based distributed single-mode sensing optical cable 3m; drilling fillers (Portland cement raw materials are P.O 32.5R, fine sand with the diameter of 0.25-0.35 mm, stones with the diameter of 10-20 mm, water, an early strength water reducing agent and the like); BOTDR optical cable strain monitoring system, laser range finder, hydraulic ram and test bench.
Fixing the distributed optical fiber sensor in the step (1) at the central position of a PVC pipe fitting; and (4) fully stirring the drilling filler with the material ratio calibrated in the step (4), injecting the drilling filler into the PVC pipe fitting, and maintaining to obtain the optical cable-concrete test piece.
(52) Fixing two ends of the optical cable-concrete test piece on a test stand, loading the optical cable-concrete test piece step by a jack on the test stand, then acquiring the test piece strain data of the optical cable-concrete test piece by a laser range finder, and recording the test piece strain data by a BOTDR system.
(53) And (3) obtaining the strain data of the filler according to the formula (1) after multiple times of loading data sampling.
In the formula:εin order for the amount of strain in the filler,hthe displacement for test loading is set manually, namely the displacement of the jack in the vertical direction;lthe distance from the initial position of the loading point (jack) (before moving towards the test piece) to the ends (both ends) of the test piece. In the step, the whole body consisting of the jack, the optical cable and the concrete test piece is simplified into a right-angled triangle; the optical cable-concrete test piece is simplified into a straight line.
(54) And (3) comparing the strain data of the test piece in the step (52) with the strain data of the filler in the step (53), and improving the distributed optical fiber sensor in the step (1) until the error is less than 10% when the error between the strain data of the test piece and the strain data of the filler in the drilled hole is more than 10%.
(6) And (6) laying the calibrated distributed optical fiber sensor in the step (5).
The scheme is suitable for working conditions of gas drainage roadways arranged under the coal seam floor, and if the coal seam floor of a research area does not have the gas drainage roadway which can be utilized, pre-buried drilling of construction optical fibers can be carried out in a working face auxiliary roadway, but attention needs to be paid to protection work of distributed optical fibers and auxiliary lines needing to extend the distributed optical fibers, and a measuring line is larger than 300m.
(61) Pore-forming by site selection according to requirement
According to the drilling site selection scheme in the step (1), two spreading positions for optical fiber monitoring are selected in the gas drainage roadway below the bottom plate of the working face of the research area, then, drilling is conducted on the top plate of the gas drainage roadway, and the terminal (top) of the drilling keeps a preset distance from the bottom of the coal mining push layer in the vertical direction. In the embodiment, a bottom plate containing fault fracture zone is arranged at one drilling hole; the other borehole is a full floor formation location. Wherein, the distance between the two monitoring drill holes is determined to be not less than 10L (m) according to the daily mining distance (L (m)) of the working face; the inclination of two drill holes is opposite to the coal seam mining direction (if: N), and the construction orientation of the drill holes is 180 degrees and 45 degrees; and the distance between the terminal of the two drill holes and the bottom of the push mining coal bed is kept within 0-5 m in the vertical direction.
Specifically, the position A is a position with a fault fracture zone in the bottom plate, the distributed optical fiber embedding drill hole penetrates through the fault fracture zone along the 45-degree angle of the top plate of the roadway, the position B is a position with a complete bottom plate rock stratum, and the distributed optical fiber embedding drill hole penetrates through the complete rock stratum along the 45-degree angle of the top plate of the roadway; A. and B, the distance between the openings of the two monitoring drill holes is not less than 10 times of the single-day mining length, and the directions and the lengths of the two drill holes are the same as shown in figure 5.
(62) Manufacturing and laying sensor embedded parts
And (4) respectively fixing the distributed optical fiber sensors calibrated in the step (5) on the outer walls of the mining high-pressure PVC pipes with the diameter of 54mm to obtain embedded parts of the sensors.
Then pushing the sensor embedded part to the bottom of the hole from the hole opening, sealing the hole opening of the drilled hole by an accelerator, embedding a plurality of layered grouting warning pipes in the hole opening of the drilled hole, and determining the number of the layered grouting warning pipes and the position of a liquid inlet end according to the number of layers of the rock stratum penetrated by the drilled hole; wherein each layered grouting warning pipe is positioned in the drill hole; the liquid inlet end of each layered grouting warning pipe is located at the top of the corresponding rock stratum, and the liquid outlet end of each layered grouting warning pipe is located outside the drill hole. Wherein, the top position parameter of the rock stratum is obtained in the step (1).
(7) The borehole in the (61) is filled from bottom to top in layers to secure the sensor embedment in the borehole. As shown in fig. 11. In fig. 11, the "optical cable monitoring line" is the "optical cable monitoring auxiliary line" in fig. 2. In fig. 2, "monitoring cable" means "distributed fiber optic sensor". In fig. 11, the connection manner between the distributed optical fiber sensor and the optical cable monitoring line is the prior art, and is not described herein again.
And (5) carrying out layered filling on the drilled hole from bottom to top based on the high-pressure PVC pipe, the layered grouting warning pipes and the drilled hole filler corresponding to the rock stratums calibrated in the step (4). Wherein the first layer is in a downward direction relative to the third layer.
In the layered filling, when the liquid outlet end of the layered grouting warning pipe at the lower layer is full of the pipe for liquid outlet, the liquid outlet end is sealed, and then drilling filler corresponding to the next rock stratum is injected into the high-pressure PVC pipe. Specifically, the layered filling comprises steps (71) - (72). Wherein, a high-pressure grouting pipeline with the inner diameter of 25mm and the length of 500mm is added during sealing, and separated grouting filling is carried out after hole sealing.
(71) And (4) injecting the drilling filler with the material ratio calibrated in the step (4) into the high-pressure PVC pipe fitting, wherein the drilling filler corresponds to the rock stratum to be filled, and the drilling filler flows to the top of the drilling hole from the inside of the high-pressure PVC pipe fitting and then returns slurry.
(72) When the hole layer corresponding to the lowest rock stratum is subjected to grouting and cross-layer grouting, the liquid outlet end of the layered grouting warning pipe corresponding to the lowest rock stratum is full of pipe liquid, the liquid outlet end is closed, and grouting is stopped; repeating the steps (71) to (72) until all hole layers corresponding to the rock stratum in the drill hole are filled. In this embodiment, when the first layer corresponding to the formation grouting cross the layer, the layered grouting warning pipe at the opening will immediately return the grouting to indicate that the formation grouting of the layer is completed. In this embodiment, the upward direction refers to a direction close to the coal seam.
In the slurry returning process, all the layered grouting warning pipes can enter slurry and flow out, but the outflow state at the moment is not full pipe liquid outlet, and only when the grouting of the hole layer corresponding to the rock stratum crosses the stratum, the liquid outlet end of the layered grouting warning pipe corresponding to the rock stratum is full pipe liquid outlet.
(8) Dynamic monitoring and data analysis
Dynamically monitoring the strain data of the mining floor of the coal bed based on the distributed optical fiber sensor and the BOTDR system in the step (62), and analyzing the monitoring data based on AV6419 ANALYER STANDARD analysis software to obtain the damage distribution rule of the rock stratum of the mining floor and the maximum damage depth of the rock stratum of the coal bed under the influence of mining.
Specifically, dynamic monitoring: using a BOTDR analyzer to collect data, wherein the equipment model is AV6419; according to a coal seam working face mining plan, data acquisition is carried out on the embedded sensor at a position which is about 150m away from the embedded sensor, and an initial background value (initial value) of a strain sensor of a coal seam floor rock stratum before mining is acquired; the difference is made between the data collected every day and the background value, and finally the coal seam floor strain data influenced by mining every day, namely the true strain value (epsilon) of the mining floor rock stratum every day x ). The data collection point is set starting at a distance of buried sensor 100m and ending after an overshoot point of 100 m. Specifically, after the distributed optical fiber sensor is buried in a coal seam bottom plate, the upper coal face is not mined; because of the disturbance in coal mining work, the coal mining and the measurement are started at a position 100 meters before the installation position of the mining line distance sensor, and the monitoring is stopped until the coal mining advances to a position 100 meters after the sensor embedding point passes. Because the coal face is generally continuous, the fiber optic sensor needs to go to the underground for testing when monitoring after installation.
The acquisition of the initial value of the optical fiber is specifically as follows: and connecting a BOTDR demodulator at the position of 150m from the top (terminal) of the pre-mining distance monitoring optical cable, and testing the strain initial value of the pre-mining distributed optical fiber. The fiber initiation value is the amount of strain that initially mobilizes the formation of the floor outside the zone of influence. Because the drilling holes are inclined holes when being arranged, the top (terminal) position of the drilling hole at the upper end is generally used as the monitoring length basis when monitoring.
And (3) data analysis:
(1) complete floor mining strain data: the stress fracture state of the coal seam floor rock stratum in the mining process of the working face is in a pulling-pressing strain alternative synergistic effect, the complete floor rock stratum is mainly in the pulling strain effect through the time and space transformation in the dynamic mining process, and the pulling-pressing strain numerical value is in a peak value state; as shown in fig. 6, the strain amount of the mining floor strata gradually decreases from the peak value until the floor strata tends to a steady state.
(2) And (3) mining strain data of the stratum containing the fault floor: the stress fracture state of the coal seam floor rock stratum is mainly expressed as a compressive strain action in the mining process of a working face, and the tensile-compressive strain values are subjected to a peak value state through the transformation of time and space in the dynamic mining process; as shown in fig. 7, the strain amount of the mining floor strata gradually decreases from the peak value until the floor strata approaches a steady state.
Mining floor rock stratum damage distribution space-time evolution characteristics and maximum damage depth:
processing is carried out based on Origin data analysis software, and data redundancy and smoothing processing are carried out on real-time data monitored by the metal cable-based distributed single-mode sensing optical cable; and synthesizing a space-time evolution diagram of the damage distribution of the mining floor rock stratum by using the monitoring time line and the corresponding monitoring point position, as shown in figures 6 and 7.
Judging the fracture of the mining floor rock layer according to the following steps: (1) the coal seam mining floor rock stratum mainly experiences compression-tension-compression states in sequence in the whole process of pushing and mining, so that the coal seam floor fracture has two states of compression limit fracture and tension limit fracture. (2) The metal cable-based distributed single-mode sensing optical cable has consistency with the deformation of the drilling filler and the surrounding rock, and the strain state of the corresponding rock stratum position is judged by utilizing real-time monitoring data of the metal cable-based distributed single-mode sensing optical cable. (3) The sampling interval distance of the metal cable-based distributed single-mode sensing optical cable is 0.05m, and strain data of different monitoring positions at different moments are obtained by taking the difference between the sampling data and the background value every day. (4) And processing based on Origin data analysis software, and performing data redundancy and smoothing on all effective data. (5) Comparing all effective data after sampling processing by using the metal cable-based distributed single-mode sensing optical cable with the extreme compressive fracture and the extreme tensile fracture strain values of different rock strata at corresponding positions (shown in table 1), and when the actual strain of the different rock strata is smaller than the extreme compressive fracture or the extreme tensile fracture strain, considering that the rock strata is in a plastic state; a formation is considered to be in a fractured condition when the actual strain of the corresponding formation is greater than its ultimate tensile or compressive fracture strain. An example is shown in fig. 8.
In summary, the ultimate tensile strain (. Epsilon.) of coring of the floor strata of the working face of the study zone is used s ) And ultimate compressive strain (. Epsilon.) c ) Measured strain (. Epsilon.) with distributed fiber x ) And comparing corresponding positions of the data to determine the area and the position of the deformation and breakage of the coal seam mining floor rock stratum. Wherein, coal seam floor mining influence is broken and is divided into tensile breaking and compression breaking, the criterion of rock mass rupture:
when in useε x <0 time,. Mu.gε s | >|ε c When the pressure is lower than the preset pressure, the coal seam floor rock stratum is in a compression fracture state;
when in useε x >At the time of 0, the number of the first,ε s > ε s when the coal seam floor rock stratum is in a tensile breaking state;
wherein:ε-amount of strain in the floor strata of the coal seam under the influence of mining;
ε c ultimate compressive fracture strain of the coal seam floor strata (each division);
ε s ultimate tensile failure strain of the coal seam floor formation (each component).
Judging the maximum damage depth of the coal seam mining floor rock stratum: according to the judgment basis of the fracture of the mining floor rock stratum and the combined state of the coal seam floor rock stratum, the maximum damage depth of the coal seam mining floor rock stratum can be judged, and examples are shown in fig. 9 and fig. 10. As will be appreciated by those skilled in the art: the effective water-resisting layer thickness value = the distance from the coal bed bottom plate to the top interface of the water-containing layer-the depth value of the bottom plate damage during coal bed mining. And the depth value of the damage of the bottom plate during coal seam mining can be obtained by the technical scheme adopted by the embodiment.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. Any person skilled in the art can make any equivalent substitutions or modifications on the technical solutions and technical contents disclosed in the present invention without departing from the scope of the technical solutions of the present invention, and still fall within the protection scope of the present invention without departing from the technical solutions of the present invention.
Claims (4)
1. A deep coal seam mining bottom plate rock stratum fracture distribution space-time evolution dynamic monitoring method is characterized by comprising the following steps:
(1) Drilling site selection and manufacturing of a distributed optical fiber sensor:
collecting engineering geological parameters and hydrogeological parameters of a project in a coal seam mining working face layout area, and then performing drilling site selection and manufacturing a distributed optical fiber sensor according to the engineering geological parameters and the hydrogeological parameters; the engineering geological parameters comprise the thickness of the coal bed, the combination mode of the rock layers of the bottom plate of the coal bed and the buried depth of the coal bed; the hydrogeological parameters comprise the distance between the coal bed and the bottom plate aquifer, the physical and mechanical properties of the aquifer and the aquifer revealed by drilling;
(2) Obtaining core samples of each formation:
coring a bottom plate rock layer of a deep coal face to be monitored to obtain a coring sample of each rock layer, then determining the lithology of each rock layer of the bottom plate rock layer of the coal bed based on the coring samples of each rock layer, and measuring the rock physical mechanical parameters of different layers to obtain various physical mechanical parameters of different rock layers;
(3) Manufacturing a sample rock cylinder of each rock stratum:
determining the material ratio of the drilling filler corresponding to different rock stratums of the drilling according to the lithology of each rock stratum and each physical and mechanical parameter of each rock stratum in the step (2), and then manufacturing sample rock cylinders corresponding to different rock stratums based on the ratio of the drilling filler;
(4) Calibrating the material ratio of the drilling filler corresponding to each rock stratum:
for the same rock stratum, checking the deformation consistency of the drilling filler and the surrounding rock based on the sample rock cylinder in the step (3) and the core sample in the step (2) to adjust the material proportion of the drilling filler corresponding to different rock strata in the step (3), and finally obtaining the calibrated material proportion;
(5) Calibrating the distributed optical fiber sensor:
aiming at the same rock stratum, based on the sample rock cylinder with the ratio of the calibration materials in the step (4) and the distributed optical fiber sensor in the step (1), detecting the deformation consistency of the distributed optical fiber sensor and the surrounding rock, so as to adjust the distributed optical fiber sensor in the step (1) and finally obtain the calibrated distributed optical fiber sensor;
the method comprises the following steps:
(51) Manufacturing an optical cable-concrete test piece:
fixing the distributed optical fiber sensor in the step (1) at the central position of a PVC pipe fitting; injecting the drilling filler with the material ratio calibrated in the step (4) into the PVC pipe fitting and maintaining to obtain an optical cable-concrete test piece;
(52) Fixing two ends of the optical cable-concrete test piece on a test rack, loading the optical cable-concrete test piece step by a jack on the test rack, then acquiring test piece strain data of the optical cable-concrete test piece by a laser range finder, and recording the test piece strain data by a BOTDR system;
(53) Solving the strain data of the drilling filler based on the test loading data;
(54) Comparing the strain data of the test piece in the step (52) with the strain data of the filler in the step (53), and improving the distributed optical fiber sensor in the step (1) until the error is less than 10% when the error between the strain data of the test piece and the strain data of the filler in the drilled hole is more than 10%;
(6) Laying the distributed optical fiber sensor calibrated in the step (5):
(61) Selecting sites according to requirements and forming holes:
according to the drilling site selection scheme in the step (1), selecting two optical fiber monitoring distribution positions in a gas drainage roadway below a bottom plate of a working face of a research area, and then constructing a drill hole on a top plate of the gas drainage roadway, wherein the terminal of the drill hole keeps a preset distance from the bottom of a coal mining layer in the vertical direction; if the coal seam floor of the research area has no available gas drainage roadway, performing optical fiber pre-buried drilling construction in the working face auxiliary roadway, paying attention to the protection work of the distributed optical fiber, timely prolonging the auxiliary line of the distributed optical fiber, and measuring the line to be larger than 300m;
(62) Manufacturing and laying a sensor embedded part:
respectively fixing the distributed optical fiber sensors calibrated in the step (5) on the outer walls of the mining high-pressure PVC pipes to obtain sensor embedded parts;
then pushing the sensor embedded part to the bottom of the hole from the hole opening, sealing the hole opening of the drilled hole, and embedding a plurality of layered grouting warning pipes in the hole opening of the drilled hole; wherein each layered grouting warning pipe is positioned in the drill hole; the liquid inlet end of each layered grouting warning pipe is positioned at the top of the corresponding rock stratum, and the liquid outlet end of each layered grouting warning pipe is positioned outside the drill hole;
(7) Drilling in the step of separate filling (61):
based on the high-pressure PVC pipe, each layered grouting warning pipe and the drilling filler corresponding to each rock stratum calibrated in the step (4), performing layered filling on the drilling from bottom to top:
in the layered filling, when the liquid outlet end of the layered grouting warning pipe at the lower layer is full of the pipe for liquid outlet, the liquid outlet end is sealed, and then drilling filler corresponding to the next rock stratum is injected into the high-pressure PVC pipe;
the layered filling comprises:
(71) Injecting the drilling filler with the material ratio calibrated in the step (4) into the high-pressure PVC pipe fitting, wherein the drilling filler corresponds to the rock stratum to be filled; the drilling filler flows from the inside of the high-pressure PVC pipe fitting to the top of the drilling hole and then returns slurry;
(72) When the hole layer corresponding to the lowest rock stratum is subjected to grouting and cross the stratum, the liquid outlet end of the layered grouting warning pipe corresponding to the lowest rock stratum is full of liquid, the liquid outlet end is sealed, and grouting is stopped; repeating the steps (71) - (72) until all hole layers corresponding to the rock stratum in the drill hole are filled completely;
(8) Dynamic monitoring and data analysis:
dynamically monitoring the strain data of the mining floor of the coal bed based on the distributed optical fiber sensor and the BOTDR system in the step (62), and analyzing the monitoring data based on AV6419 ANALYER STANDARD analysis software to obtain the damage distribution rule of the rock stratum of the mining floor and the maximum damage depth of the rock stratum of the coal bed under the influence of mining.
2. The deep coal seam mining floor rock fracture distribution spatiotemporal evolution dynamic monitoring method of claim 1, characterized in that the distributed optical fiber sensor is a metal cable-based distributed single-mode sensing optical cable.
3. The deep coal seam mining floor rock fracture distribution spatiotemporal evolution dynamic monitoring method of claim 1, wherein the step (4) comprises:
(41) Respectively performing a uniaxial compression test and a uniaxial shear test on a core sample aiming at the same rock stratum; uniaxial compression test and uniaxial shear test of the sample rock cylinder;
(42) Comparing and analyzing test result data of the same type of test;
(43) Adjusting the material ratio of the drilling filler according to the comparative analysis data;
(44) And (5) repeating the steps (41) to (43) until the precision between the test result data of the sample rock cylinder and the core sample reaches a preset value.
4. The deep coal seam mining floor rock stratum fracture distribution spatiotemporal evolution dynamic monitoring method according to claim 1, characterized in that in step (61), a floor fault fracture zone is formed at a drill hole; the other borehole is a full floor formation location.
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