CN106990031A - Coal seam containing gas Percolation Law experimental study method under one kind vibration Excavation - Google Patents

Abstract

The invention provides a test and research method for gas-containing coal rock seepage law under vibration unloading conditions, which is realized by a test device including a triaxial pressure chamber, a loading device, a data measurement and acquisition device, and a gas injection device. The test device also includes A disturbance device, the disturbance device includes a disturbance rod, and the disturbance rod is connected to a vibration exciter; the research method includes: processing the coal-rock specimen so that its aspect ratio is 2:1; affixing the stress-strain sensor to the coal-rock Put the heat-shrinkable tube on the surface of the test piece and put it into the triaxial pressure chamber; turn on the gas injection device and fill the gas in the triaxial pressure chamber until the coal-rock test piece reaches adsorption equilibrium, so as to simulate the real on-site gas pressure of the coal-rock test piece. According to the set parameters, the axial load, radial load and axial disturbance are applied to the coal and rock specimens until the specimens are destroyed, and the stress and strain values and gas flow values in the process are monitored to obtain the results under different vibration unloading conditions. Seepage law of gas-bearing coal rock.

Description

A method for experimental research on seepage law of gas-containing coal and rock under vibration unloading condition

technical field

The invention relates to the technical field of coal mining, in particular to a test and research method for the seepage law of gas-containing coal rock under vibration unloading conditions.

Background technique

The geological environment of deep coal resources is complex, the permeability of coal seams is low, the ground stress and gas pressure are huge, and it is easy to cause gas power accidents during the mining of coal resources. Unmined original coal and rock are in a state of stress balance under the action of in-situ stress and tectonic stress. Engineering disturbances such as mining cause the load on the coal and rock mass to change in time and space, and the internal stress of the coal and rock mass is redistributed, resulting in The unrecoverable new cracks continue to expand, and finally form through cracks to make the whole lose its integrity, which is manifested as deformation, destruction, instability and other phenomena in the macroscopic view; the mining disturbance also changes the permeability characteristics of the coal and rock mass, and the coal The permeability characteristics of rock mass directly affect the migration and accumulation of gas, resulting in changes in gas pressure in local areas, and the strength of coal and rock mass also changes accordingly. The above process presents the characteristics of the coupling effect of stress field and seepage field of coal and rock mass. In the studies considering the influence of mining disturbance on the permeability characteristics of coal and rock mass, most of them assume that the coal and rock mass is in a uniaxial or triaxial stress-strain environment, and take unloading radial load as the test condition. Jiang Changbao et al. used a self-made heat-fluid-solid coupling three-axis servo seepage experimental device for gas-containing coal to conduct a gas seepage test of gas-containing coal and rock under unloading radial loads, and studied its deformation and gas seepage characteristics during the process of unloading radial loads. Yin Guangzhi et al. used the self-developed "gas-containing coal heat-fluid-solid coupling three-axis servo seepage test device" to test the effects of different initial radial loads and different gas pressure combinations, and different unloading radial load speeds on gas-containing coal rock mechanics and gas. Seepage characteristics affect experimental studies. Using the MTS815 mechanical testing machine, Huang Qixiang et al. used the MTS815 mechanical testing machine to study the briquette specimens prepared from the raw coal of the outburst coal seam of the Songzao Mining Bureau of a typical coal and gas outburst mine. Sun Guangzhong et al. aimed at the evolution law of gas-containing coal permeability under constant axial load and unloading radial load, taking the raw coal samples of Xindeng Coal Industry as the research object, and using the self-developed gas-containing coal-rock triaxial stress creep seepage test device, carried out different Seepage test under constant axial stress under radial load and unloading radial load.

In the above studies on the permeability characteristics of coal and rock mass, the influence of the combination of dynamic and static loads on the permeability characteristics of coal and rock mass has not been considered. In a real mining environment, coal and rock are not only affected by internal static loads, but also by dynamic loads such as roof fractures, as well as engineering disturbance dynamic loads such as blasting and excavation operations. After vibration operations such as excavators act on the coal body, the stress of the coal body will be increased and the stress state of the coal body will be changed, mainly because the stress state of the skeleton of the coal body will be changed. It moves irregularly, and directly squeezes the coal body skeleton, and then produces pore compression strain, adsorption expansion strain, and extrusion strain. Most of the existing studies have studied the macroscopic mechanical properties of coal and rock mass under dynamic and static combined loading, but there are few studies on the permeability characteristics of gas-bearing coal and rock under combined dynamic and static loading. In the above studies on the impact of mining disturbance on the permeability characteristics of coal and rock mass, the impact of mining methods was not considered. In fact, under different mining methods, the coal and rock mass in front of the working face has experienced a complete mining dynamic process from the increase of original rock stress and axial stress and the decrease of radial load to failure and unloading. Different mining methods correspond to different stress paths, resulting in different stress distribution and evolution of coal and rock mass, which in turn affects the development of fracture networks and changes in permeability. Simply unloading radial loads cannot simulate the real mining environment.

In the existing research, less consideration is given to the influence of mining methods and engineering disturbance on the permeability characteristics of coal and rock mass. Xie Heping analyzed the distribution of the support pressure of the working face under the three different mining methods of top-coal caving mining, coal pillar-free mining, and protective layer mining, and explored the fracture field, stress field, and seepage of gas-bearing coal and rock under real mining conditions. field characteristics. In the design of the test scheme, the axial pressure is used to simulate the support stress, the change of the radial load is used to simulate the horizontal stress, and three different mining methods are simulated by applying loads with different ratios of axial load and radial load. Although the above studies considered the influence of different mining methods on the permeability characteristics of gas-bearing coal rocks, the influence of vibration was not considered, and the test process was complicated. On the basis of the existing research results, this paper proposes a new gas-containing coal rock seepage test method under different mining methods, which is more close to the actual engineering situation, and the research results can effectively guide the joint mining of coal and gas.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides an experimental research method for the seepage law of gas-containing coal rock under vibration unloading conditions, which can simulate real mining conditions and lay a foundation for scientific analysis of the seepage characteristics of gas-containing coal rock. Technical scheme of the present invention is:

A test and research method for gas-containing coal rock seepage law under vibration unloading conditions is realized by a test device including a triaxial pressure chamber, a loading device, a data measurement and acquisition device, and a gas injection device. The test device also includes a disturbance device, The disturbance device comprises a disturbance rod, and the disturbance rod is connected with a vibrator; the research method comprises the following steps:

(1) Process the coal and rock specimens so that the ratio of height to diameter is 2:1;

(2) Stick the stress-strain sensor on the surface of the coal and rock specimen and put it on the heat-shrinkable tube and put it into the triaxial pressure chamber;

(3) Turn on the gas injection device and fill the triaxial pressure chamber with gas until the coal-rock specimen reaches adsorption equilibrium, so as to simulate the real on-site occurrence of the coal-rock specimen;

(4) Apply axial load, radial load and axial disturbance to the coal-rock specimen according to the set parameters until the specimen is destroyed, monitor the stress-strain value and gas flow value during the process, and obtain the results under different vibration unloading conditions. Seepage law of gas-bearing coal rock.

In the above method, the disturbing rod is arranged in the middle of the upper pressing head of the loading device.

A test and research method for gas-containing coal rock seepage law under vibration unloading conditions is realized by a test device including a triaxial pressure chamber, a loading device, a data measurement and acquisition device, and a gas injection device. The test device also includes a disturbance device, The disturbance device comprises a disturbance rod, and the disturbance rod is connected with a vibrator; the research method comprises the following steps:

(1) Process the coal and rock specimens so that the ratio of height to diameter is 2:1;

(2) Stick the stress-strain sensor on the surface of the coal and rock specimen and put it on the heat-shrinkable tube and put it into the triaxial pressure chamber;

(3) Turn on the gas injection device and fill the triaxial pressure chamber with gas until the coal-rock specimen reaches adsorption equilibrium;

(4) Apply axial load, radial load and axial disturbance to the coal and rock specimen according to the set parameters;

(5) According to the ratio of axial load loading rate and radial load unloading rate of 1.5:1, load and unload coal and rock specimens to simulate the initial disturbance stage of coal and rock specimens;

(6) According to the stress concentration coefficient ranges of the three mining methods of protective layer mining, top-coal caving mining and coal pillar mining, set the ratio between the axial load loading rate and the radial load unloading rate of the three mining methods respectively. Loading and unloading are applied to the specimen until the specimen is destroyed, and the stress-strain value and gas flow value of the process are monitored to obtain the seepage law of gas-containing coal and rock under different mining methods and different vibration unloading conditions.

In the above method, the disturbing rod is arranged in the middle of the upper pressing head of the loading device.

The beneficial effect of the present invention is that: the present invention can test the seepage rule of gas-containing coal and rock before and after the disturbance load and during the process, which is closer to real mining conditions and makes the test operation process more convenient. In addition, the present invention also considers the influence of mining methods on the permeability characteristics of gas-bearing coal rocks, and uses the ratio of the axial loading rate to the radial unloading rate to characterize the three different types of protection layer mining, top-coal mining, and coal pillar-free mining. The mining method can truly reflect the different stress distribution and permeability characteristics of coal and rock under different mining paths.

Description of drawings

Fig. 1 is the schematic structural diagram of the test system adopted in the embodiment of the present invention, wherein, 1-triaxial pressure chamber, 2-loading device main oil cylinder, 3-oil pump, 4-gas cylinder, 5-disturbance rod, 6-excitation Shaker, 7-coal rock specimen.

Fig. 2 is a double Y-X curve diagram of stress value/permeability versus strain value of group ① in Example 1 of the present invention.

Fig. 3 is a double Y-X curve diagram of stress value/permeability versus strain value of group ② in Example 1 of the present invention.

Fig. 4 is a double Y-X curve diagram of stress value/permeability versus strain value of group ③ in Example 1 of the present invention.

Fig. 5 is a double Y-X curve diagram of stress value/permeability versus strain value of group ④ in Example 1 of the present invention.

Fig. 6 is a double Y-X curve diagram of stress value/permeability versus strain value of group [1] in Example 2 of the present invention.

Fig. 7 is a double Y-X graph of stress value/permeability versus strain value of group [2] in Example 2 of the present invention.

Fig. 8 is a double Y-X graph of stress value/permeability versus strain value of group [3] in Example 2 of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments, which are explanations rather than limitations of the present invention.

Example 1

The present invention provides a test and research method for gas-containing coal rock seepage law under the condition of vibration unloading, which is realized on the test device as shown in Figure 1. The test device includes a triaxial pressure chamber 1, a loading device, and a data measuring device. The collection device and the gas injection device, the test device also includes a disturbance device, the disturbance device includes a disturbance rod 5, the disturbance rod 5 is located in the middle of the upper pressure head of the loading device, and the disturbance rod 5 is connected to the vibrator 6. The axial load and radial load are implemented by the loading device, the axial disturbance is implemented by the disturbance device, the gas is provided by the gas cylinder, and different gas supply pressures can be set artificially, and the gas flow rate is determined by the valve installed on the gas outlet pipeline. Digital electronic gas flow meter collection. The function of the data measurement and acquisition device is to use sensors to measure and collect test data; the function of the gas injection device is to provide gas for the test. The research method includes the following steps:

Step 1: Process the coal rock test piece, crush the original coal block taken from the coal mine site of a mining company in Shanxi with a pulverizer, screen out 40-100 mesh coal powder, mix it with pure water and place it in a 200t material test On the machine, apply a molding pressure of 100MPa to press into a standard briquette test piece of Φ50mm×100mm, bake the prepared briquette test piece at 80°C for 24 hours, and prepare four groups of 20 coal rock test pieces, 5 for each group, and Not ①, ②, ③, ④;

Step 2: Stick the stress-strain sensor on the surface of the coal-rock specimen and put it on the heat-shrinkable tube and put it into the triaxial pressure chamber;

Step 3: Open the gas opening valve, fill the triaxial pressure chamber with gas until the coal-rock specimen reaches adsorption equilibrium, so as to simulate the real on-site occurrence of the coal-rock specimen;

Step 4: Open the gas outlet valve, and after the gas flowmeter shows a stable value, start the loading program, apply axial load and radial load to the test piece at a loading rate of 0.001mm/s, and at the same time open the disturbance device, according to The vibration frequencies of groups ①~④ are 0 Hz, 10 Hz, 20 Hz, and 40 Hz, respectively, and axial disturbance is applied to the specimens until the specimens are destroyed. Five specimens in each group are tested once under the same test conditions, and the vibration in the process is monitored. Stress and strain values and gas flow values (permeation volume), take the average value of the 5 test data obtained in each group of tests after removing the failed test data, and regard this average value as the result data of each group of tests, and the stress and strain values can be obtained from the data The measurement and acquisition device can directly obtain the permeability. The permeability can be obtained from the permeability measured by the data measurement and acquisition device and the permeability calculation formula. The double Y-X curve is drawn with the strain value on the abscissa and the stress value and permeability on the ordinate, as shown in the figure 2~5 shown. From Figures 2 to 5, it can be seen that in the early stage of loading, that is, the stage when the slope of the stress-strain curve is a constant value, the cracks in the coal rock body are compacted and elastically deformed, and the permeability decreases with time; in the middle stage of loading, that is, In the stage where the slope of the stress-strain curve gradually decreases, the initial fractures inside the coal continue to be compacted, and the permeability continues to decrease, but the decreasing trend slows down. Internal new cracks form penetrating cracks, which make the whole lose its integrity, and the permeability continues to increase. At the end of the loading stage, that is, the stage where the stress gradually decreases with the increase of the strain, the increase trend of the permeability slows down, and the existence of the radial load restrains the destruction of the coal sample to a certain extent, so that the permeability of the coal sample tends to a constant value. Figures 2 to 5 also show that with a certain strain value, the permeability under vibration test conditions is greater than that under no vibration conditions, and the higher the vibration frequency, the greater the permeability. The reason is that the mechanical waves generated by mechanical vibration intensify the irregular movement of gas molecules, and the adsorption and desorption process is more intense. The extrusion force generated by attenuating vibration accelerates the development of internal cracks in coal and rock mass, and accelerates the evolution of permeability. The test results show that engineering disturbance affects the seepage evolution of coal and rock.

Example 2

The present invention also provides a kind of gas-containing coal rock vibration unloading test research method, also adopts the test device as shown in Figure 1, and described research method comprises the following steps:

Step 1: Step 1: Process the coal rock test piece, crush the original coal block taken from the coal mine site of a mining company in Shanxi with a pulverizer, screen out 40-100 mesh coal powder, mix it with pure water and place it in 200t On the material testing machine, apply a molding pressure of 100MPa to press into a standard briquette test piece of Φ50mm×100mm, bake the prepared briquette test piece at 80°C for 24 hours, and prepare three groups of 15 coal rock test pieces, each group 5 , and the groups are [1], [2], [3], corresponding to the three mining methods of protective layer, top-coal caving and no coal pillar respectively;

Step 2: Stick the stress-strain sensor on the surface of the coal-rock specimen and put it on the heat-shrinkable tube and put it into the triaxial pressure chamber;

Step 3: Open the gas opening valve, fill the triaxial pressure chamber with gas until the coal-rock specimen reaches adsorption equilibrium, so as to simulate the real on-site occurrence of the coal-rock specimen;

Step 4: Start the disturbance device, and apply an axial disturbance to the specimen according to the vibration frequency of [1]~[3] groups at 20 Hz; start the loading device, and apply an axial load and Radial load until it reaches 20MPa to simulate the hydrostatic pressure state under the natural occurrence conditions of coal rocks;

Step 5: Start the loading device, apply loading and unloading to the specimen according to the axial load loading rate of 0.0015mm/s and the radial load unloading rate of 0.0010mm/s until the axial load reaches 24MPa and the radial load reaches 18MPa, then Simulate the initial disturbance stage of the coal-rock specimen;

Step 6: According to the ranges of the measured stress concentration factors of the protective layer, top-coal caving and coal pillar-free mining methods are 1.4-2.4, 1.7-2.7 and 2.2-3.5 respectively, set the axial load loading rate and The ratio of radial load unloading rate is: protective layer mining 2.0 (axial load loading rate is 0.0015mm/s, radial load unloading rate is 0.00075mm/s), top-coal caving mining 2.5 (axial load loading rate is 0.0015 mm/s, the radial load unloading rate is 0.0006mm/s), coal pillarless mining 3.0 (the axial load loading rate is 0.0015mm/s, the radial load unloading rate is 0.0005mm/s), and the test piece is applied with Unload until the specimens are destroyed, test 5 specimens in each group according to the same test conditions for one time, monitor the stress and strain values and gas flow values in the process, and remove the failed test data from the 5 test data obtained in each group of tests Take the average value, and regard this average value as the result data of each group of tests. The stress and strain values can be directly obtained by the data measurement and acquisition device, and the permeability can be obtained from the permeability measured by the data measurement and acquisition device and the permeability calculation formula. The strain value is the abscissa, and the double Y-X curve is drawn with the stress value and permeability as the ordinate, as shown in Figures 6-8. It can be seen from Figures 6 to 8 that the changing law of permeability is the same as that in Example 1. In the early stage of loading and the middle stage of loading, the test conditions of the three groups of tests are the same, they all experienced loading axial load, radial load to a fixed value, and initial intermittent radial load at a fixed ratio, so the permeability in the three groups of tests is increasing The changes in the early stage and mid-loading stage are the same. When the test enters the stage of increasing axial load and unloading radial load to simulate different mining methods, under a certain strain value, the smaller the loading and unloading rate ratio, the greater the permeability. The test results show that the mining method affects the seepage evolution law of coal rock.

In step 6 of this embodiment, the mining method of the protective layer has the effect of pre-mining pressure relief on the protected layer, reducing the risk of gas outburst in the protected layer, and the longitudinal support pressure of the coal rock mass within the same loading time is lower than that of mining without coal pillars. 1. The top-coal mining method should be small, so the loading and unloading rate ratio is the smallest. According to the measured stress concentration factor range, the loading and unloading rate ratio under the protective layer mining method is set as 2.0; the top-coal mining has a large disturbance range on the roof. In the same loading time, compared with the protection layer mining, the bearing pressure caused by top-coal caving mining is larger. According to the measured stress concentration factor range, the loading rate ratio under the top-coal caving mining method is set as 2.5; in the non-coal pillar mining method In this case, due to the lack of effective support of the coal pillar to the roof, the support pressure increases, and the longitudinal support pressure in the coal rock body caused by mining without coal pillars in the same loading time is the largest. According to the measured stress concentration factor range, the coal without coal The loading rate ratio is set at 3.0 under the column mining method.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the protection scope of the present invention.

Claims (3)

1. A method for experimental research on gas-containing coal-rock seepage law under vibration unloading conditions, is realized by a test device comprising a triaxial pressure chamber, a loading device, a data measurement acquisition device and a gas injection device, and is characterized in that the test device It also includes a disturbance device, the disturbance device includes a disturbance rod, and the disturbance rod is connected to a vibrator; the research method includes the following steps: (1) Process the coal and rock specimens so that the ratio of height to diameter is 2:1; (2) Stick the stress-strain sensor on the surface of the coal and rock specimen and put it on the heat-shrinkable tube and put it into the triaxial pressure chamber; (3) Turn on the gas injection device and fill the triaxial pressure chamber with gas until the coal-rock specimen reaches adsorption equilibrium, so as to simulate the real on-site occurrence of the coal-rock specimen; (4) Apply axial load, radial load and axial disturbance to the coal-rock specimen according to the set parameters until the specimen is destroyed, monitor the stress-strain value and gas flow value during the process, and obtain the results under different vibration unloading conditions. Seepage law of gas-bearing coal rock. 2. A test and research method for gas-containing coal-rock seepage law under vibration and unloading conditions is realized by a test device comprising a triaxial pressure chamber, a loading device, a data measurement acquisition device and a gas injection device, and is characterized in that the test device It also includes a disturbance device, the disturbance device includes a disturbance rod, and the disturbance rod is connected to a vibrator; the research method includes the following steps: (1) Process the coal and rock specimens so that the ratio of height to diameter is 2:1; (2) Stick the stress-strain sensor on the surface of the coal and rock specimen and put it on the heat-shrinkable tube and put it into the triaxial pressure chamber; (3) Turn on the gas injection device and fill the triaxial pressure chamber with gas until the coal-rock specimen reaches adsorption equilibrium; (4) Apply axial load, radial load and axial disturbance to the coal and rock specimen according to the set parameters; (5) According to the ratio of axial load loading rate and radial load unloading rate of 1.5:1, load and unload coal and rock specimens to simulate the initial disturbance stage of coal and rock specimens; (6) According to the stress concentration coefficient ranges of the three mining methods of protective layer mining, top-coal caving mining and coal pillar mining, set the ratio between the axial load loading rate and the radial load unloading rate of the three mining methods respectively. Loading and unloading are applied to the specimen until the specimen is destroyed, and the stress-strain value and gas flow value of the process are monitored to obtain the seepage law of gas-containing coal and rock under different mining methods and different vibration unloading conditions. 3. A test and research method for gas-containing coal-rock seepage law under vibration and unloading conditions according to claim 1 or 2, characterized in that the disturbance rod is arranged in the middle of the upper pressure head of the loading device.