Testing method for permeability resistance test of low-permeability coal rock medium

Abstract

The invention discloses a low-permeability coal rock medium anti-permeability test method which comprises the following steps: preparing a coal rock sample, and putting the sample into a seepage tank; filling the sealing film with water to ensure that the box wall and the bottom plate are attached to the surface of the sample; adding test water, and setting a water inlet and outlet head and a transparent box base inclination angle; starting a water pump to supply water; water flows through the water inlet system and the test box body system through the circulating water supply system; adjusting a water inlet head; water enters the water outlet groove of the test box body system; reading the data of the water outlet flow meter, calculating the permeability coefficient of the sample, and finding the maximum impermeable water head difference of the sample by using a bisection method; analyzing the influence of the invariable water pressure and the soaking effect of water on the permeability resistance of the sample; in addition, sample preparation is repeated, a water inlet head is adjusted at short time intervals, and the influence of short-time water pressure change on the permeability resistance of the sample is analyzed; in addition, sample preparation is repeated, a water inlet head is adjusted at a long time interval, and the influence of long-time changing water pressure and water soaking action change on the permeability resistance of the sample is analyzed; the device can be used for testing the permeability resistance of the coal rock medium.

Description

Technical Field

[0001] The invention relates to the technical field of coal rock indoor testing, in particular to a method for testing the anti-permeability of low-permeability coal rock media. Background Art

[0002] my country's coal resources are relatively rich, but due to the significant differences in the geological characteristics of coal seams and the extremely complex hydrogeological conditions, coal mining faces huge technical challenges. During the construction and mining of coal mines, the excavation and transformation of surface and underground rock formations will change the surface runoff and groundwater flow field in the surrounding areas. In geological environments such as water-rich formations and water-bearing geological structures such as water-bearing faults, water seepage may occur. Mining coal seams may cause the relative impermeable layer between the coal mining area and the aquifer to become thinner or disappear, and the distance between the aquifer and the coal mining area will be reduced. Especially in the case of underwater coal mining, when the head difference increases and the hydraulic gradient increases, the coal seam may eventually be damaged by penetration under the action of changing water pressure and water immersion, and groundwater will flow into the coal mining area, causing casualties and property losses. Therefore, it has become an urgent problem to determine the permeability coefficient and permeability of coal rock, explore the anti-seepage strength of coal rock, and study what kind of penetration damage will occur in coal rock under water pressure and water immersion conditions. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a method for testing the anti-permeability of low-permeability coal rock media. The present invention can test the anti-permeability of coal rock media.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a low permeability coal rock medium anti-permeability test method, comprising the following steps:

[0005] S1: Coal rock with a volume larger than the length and width of the seepage trough (43) of the test device is cut according to the length and width of the seepage trough (43) or small coal blocks and coal powder are uniformly mixed to prepare a test sample, and the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are selected according to the minimum diameter of the sample particles, and the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are inserted into the transparent box (14), and the sample is placed in the seepage trough (43);

[0006] S2: Filling water into the sealing film water filling port (18) on the side of the seepage trough (43) and the sealing film water filling port (21) on the bottom plate of the seepage trough so that the surface of the sealing film always fits the surface of the sample;

[0007] S3: Add test water to the water supply tank (33) of the circulating water system, close the water inlet valve (7) and the water outlet valve (28) of the transparent box (14), adjust the height of the water outlet box (29) by means of the water outlet box hydraulic rod (30) and the second laser rangefinder (38), so that the height of the water outlet (32) and the height of the sample at the position of the water outlet trough screen partition (15) are at the same horizontal plane, set to the water level of the water outlet box (29), i.e. the water outlet head, adjust the height of the second water inlet box (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), so that the horizontal plane where the float of the float valve (4) is located is higher than the water level of the water outlet box (29), set to the water level of the second water inlet box (2), i.e. the water inlet head, and set the inclination angle of the transparent box base by means of the transparent box base hydraulic rod (22) and the slide rail (23);

[0008] S4: If the water inlet head is higher than the height of the top of the water inlet tank, it is also necessary to install a water inlet tank sealing strip (12) on the top of the water inlet tank (40), cover the top of the seepage tank (43) with a cover plate (9), and fill water through the water filling port (10) of the cover plate sealing film, so that the surface of the sealing film is in contact with the surface of the sample, and evenly place weights on the cover plate to ensure that the cover plate (9) always fits the sample;

[0009] S5: starting the water pump (36), passing water from the circulating water supply tank (33) through the pre-filter (34), filtering the particles in the water, and then transporting the water to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is provided with a water level controller (39). When the water level in the first water inlet tank (1) is lower than half, the water level controller (39) controls the water pump (36) to operate, and stops operating after the first water inlet tank (1) is filled. The process of the water pump (36) supplying water to the first water inlet tank (1) is cyclically carried out;

[0010] S6: water from the first water inlet tank (1) enters the second water inlet tank (2) through the water supply hose (3). When the water reaches the height of the float valve (4), the float valve (4) controls the water supply hose (3) to stop supplying water. When the water level is lower than the set water level, the float valve (4) controls the water supply hose (3) to supply water. The process of the float valve (4) controlling the water supply hose (3) to supply water and stop supplying water is repeated;

[0011] S7: Open the water inlet valve (7) and the transparent box water outlet valve (28), and water enters the water inlet tank (40) from the second water inlet box (2) through the water inlet hose (6). The water infiltrates into the sample in a planar manner through the water inlet tank screen partition (13). Observe the water inlet flow meter (42). If the flow meter reading at a certain moment does not change compared with the flow meter reading before a preset time, adjust the height of the second water inlet tank (2) through the hydraulic rod (5) and the first laser rangefinder (37) to increase the preset height.

[0012] S8: Repeat the test process of S4-S7 until water enters the water outlet tank (41). The water inlet head set when water first flows into the water outlet tank (41) is defined as h1, and the water outlet head is defined as h2. Water enters the water outlet tank (29) through the transparent box water outlet hose (27). When the water level reaches the water outlet (32), it flows out to the circulating water supply tank (33), completing the recycling of the test water. The water volume of the outlet water is measured and recorded by the water outlet flow meter (31);

[0013] S9: Read the water outlet flow meter (31) data Q1 and Q2 at time t1 and t2, where t2>t1. The flow meter reading is the total flow from the start of the test to a certain time point. Therefore, the flow from t1 to t2 is the difference between the flow meter readings at the two time points (Q2-Q1). The permeability coefficient and permeability of the sample are obtained according to the following formula:

[0014]

[0015] Wherein: K is the permeability coefficient of the sample; t1 and t2 are the times for reading the flow meter data, Q1 is the flow meter data at time t1; Q2 is the flow meter data at time t2; L is the distance between the gauze partition (13) of the water inlet trough and the gauze partition (15) of the water outlet trough; A is the area of ​​the water outlet cross section; H1 is the water inlet head; H2 is the water outlet head; k is the permeability of the sample; η is the dynamic viscosity coefficient of water; ρ is the density of the sample; g is the acceleration of gravity;

[0016] S10: Define the water level change value as Δh, initial Δh = (h1-h2) / 2, measure the maximum impermeable head difference of the sample by dichotomy, the water head H1 is reduced by Δh / 2, and the new water head change value Δh 新 =Δh / 2, after the water inlet head H1 drops to the set value, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within the preset time, proceed to step S12;

[0017] S11: Inlet head H1 increases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, repeat step S11; if the reading of the water inlet flow meter (42) changes within the preset time, proceed to step S12;

[0018] S12: Inlet head H1 decreases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新=Δh / 2, if the reading of the water inlet flow meter (42) does not change within the continuous preset time, proceed to step S11; if the reading of the water inlet flow meter (42) changes within the preset time, repeat step S12;

[0019] S13: After steps S10-S12, in order to accurately calculate the maximum impermeable head difference to centimeters, when Δh≦0.01m, if the reading of the water inlet flow meter (42) does not change for a continuous preset time, that is, no water infiltrates into the sample for a continuous preset time, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample; if the reading of the water inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within the preset time, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample;

[0020] S14: adjusting the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), setting H1 to the height of H2 plus the maximum impermeable water head difference of the sample, and continuing the test for N days to observe whether water can penetrate through the sample into the water outlet tank (41), and continuously recording the flow rate by the water outlet flow meter (31), and performing step S9 to calculate the permeability coefficient and permeability of the sample every M hours, observing whether the permeability coefficient and permeability change, and analyzing the influence of the constant water pressure and water immersion on the anti-permeability of the sample, and repeating steps S10-S13 after N days to find the new maximum impermeable water head difference of the sample under the constant water pressure and water immersion;

[0021] S15: re-prepare the sample, perform steps S1-S13, and set H1 to the height of H2 plus the maximum impermeable head difference of the sample;

[0022] S16: Every K minutes, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to increase the preset height for a certain period of time;

[0023] S17: Every L minutes, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to reduce the preset height for a certain period of time;

[0024] S18: The test is performed by performing steps S16 and S17 once as one cycle, and the cycle is repeated multiple times. The test lasts for several hours in total, and step 9 is performed to calculate the permeability coefficient and permeability of the sample, and observe their changes. Steps S10-S13 are repeated to find the new maximum impermeable head difference of the sample under the action of short-term water pressure changes, and the influence of short-term water pressure changes on the sample's anti-permeability is analyzed;

[0025] S19: Re-prepare the sample, perform steps S1-S13, and set H1 to the height of H2 plus the maximum impermeable water head difference of the sample;

[0026] S20: Every M hours, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to increase the preset height for a certain period of time;

[0027] S21: Every M hours, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to reduce the preset height for a certain period of time;

[0028] S22: The test is carried out with steps S20 and S21 as one cycle. The cycle is repeated multiple times. The test lasts for several days. Step 9 is carried out to calculate the permeability coefficient and permeability of the sample and observe their changes. Steps S10-S13 are repeated to find the new maximum impermeable head difference of the sample under the long-term changing water pressure and water immersion, and the influence of the long-term changing water pressure and water immersion on the anti-permeability of the sample is analyzed.

[0029] As a further improvement of the present invention, in step S1, the test device comprises a circulating water system, a water inlet system, a test box system and a water outlet system, the four systems are arranged on a steel frame support (25), two universal wheels (26) are installed at the bottom of the steel frame support (25), the circulating water system is connected to a water pump (36) through a pre-filter (34) and a circulating water supply hose (35), the water pump (36) is connected to a first water inlet tank (1) of the water inlet system, a water level controller (39) is located on a side wall of the first water inlet tank (1), and the first water inlet tank (1) is connected to a water supply hose (35). The second water inlet tank (2) is connected to the second water inlet tank (2), the float valve (4) is located inside the second water inlet tank (2), the hydraulic rod (5) is located at the bottom of the second water inlet tank (2), the first laser rangefinder (37) is located at the bottom of the hydraulic rod (5), the second water inlet tank (2) is connected to the water inlet tank (40) of the transparent box (14) of the test box system through the water inlet hose (6), the water inlet hose (6) is provided with a water inlet valve (7) and a water inlet flow meter (42), the top of the water inlet tank (40) is provided with a water inlet tank sealing strip (12), and the water inlet tank (40) is connected to the seepage flow meter through the water inlet tank mesh partition (13). The transparent box (14) is separated from the transparent box base (20), the bottom of the transparent box base (20) is connected to the transparent box base hydraulic rod (22) and the transparent box base rotating shaft (24), the transparent box base hydraulic rod (22) is connected to the slide rail (23), the top of the seepage groove (43) is provided with a cover plate (9), the cover plate (9) has a cover plate handle (8), a cover plate sealing water filling port (10) and a cover plate sealing film (11), the front and rear side walls of the seepage groove (43) have a seepage groove side water filling port (18) and a sealing film, and the bottom plate of the seepage groove (43) has a seepage groove bottom plate The sealing film water filling port (21) and the sealing film, the transparent box (14) is separated from the water outlet trough (41) by a water outlet trough mesh partition (15), the top of the water outlet trough (41) is provided with a water outlet trough sealing strip (16), the water outlet trough (41) is connected to the water outlet box (29) of the water outlet system through a transparent box water outlet hose (27), the transparent box water outlet hose (27) is provided with a transparent box water outlet valve (28), the bottom of the water outlet box (29) is connected to the water outlet box hydraulic rod (30), the water outlet (32) is connected to the circulating water supply tank, and the water outlet (32) is provided with a water outlet flow meter (31).

[0030] As a further improvement of the present invention, in step S1, the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are replaceable to ensure that the seepage trough (43), the water inlet trough (40) and the water outlet trough (41) are separated, and particles in the sample cannot enter the water inlet trough (40) and the water outlet trough (41), so that water can flow into the sample in a planar manner and outflow to the water outlet trough (41).

[0031] As a further improvement of the present invention, in the step S3, the water supply tank (33) of the circulating water system is the replenishment point and starting point of the test water, which is connected to the water inlet system and the water outlet system to ensure the recycling of the test water.

[0032] As a further improvement of the present invention, in the steps S10-S13, the binary search method mentioned is to divide the ordered array into two halves, compare the middle element with the target value each time, and decide whether to continue searching in the first half or the second half according to the comparison result until the target value is found or determined not to exist.

[0033] In the step S2, the sealing film is elastic and can be deformed after water is filled into the sealing film so that its outer surface always fits the sample surface, thereby preventing water from flowing along the gaps between the sample and the side walls, bottom plate and cover plate of the seepage trough (43).

[0034] In the step S3, the water supply tank (33) of the circulating water system is the replenishment point and starting point of the test water, and is connected to the water inlet system and the water outlet system to ensure the recycling of the test water.

[0035] In the step S3, the hydraulic rods (5, 30) and the laser rangefinders (37, 38) can accurately, flexibly and labor-savingly set the heights of the second water inlet box (2) and the water outlet box (29), ensuring that the water head difference can be maintained at the set value. The inclination angle of the transparent box base is set by the hydraulic rods (22) and the slide rails (23), which can simulate different inclination angles of the sample and different infiltration angles of water, thereby increasing the conditions applicable to the test.

[0036] In the step S4, the water inlet trough sealing strip (12), the cover plate (9) and the water outlet trough sealing strip (16) are all conveniently installed and disassembled so as to be applicable to two different test conditions: non-pressure-bearing and pressure-bearing. The cover plate sealing film (11) is elastic and can be deformed after water is filled into the sealing film. Weights are evenly placed on the cover plate (9) to ensure that the cover plate (9) is evenly stressed, so that the outer surface of the sealing film always fits the sample surface.

[0037] In the step S5, the pre-filter (34) can filter the test water to ensure that the test water is clean and can smoothly pass through various hoses, water pumps, and samples; the water level controller (39) controls the start and stop of the water pump (36), thereby extending the service life of the water pump and saving electricity resources.

[0038] In step S6, the float valve (4) can be used to control whether the water inlet hose (3) supplies water to the second water inlet tank (2), thereby maintaining the water level of the second water inlet tank (2) at a fixed position.

[0039] In step S7, the water inlet flow meter (42) can continuously record the amount of water that seeps into the sample and store the data. When the reading of the water inlet flow meter (42) does not change within a certain period of time, it can be determined that under the currently set test conditions, water cannot flow in the sample and the test conditions need to be changed, thereby reducing the waiting time and improving the test efficiency.

[0040] In step S8, the water flow meter (31) can continuously record the amount of water seeping out of the sample and store the data, and the water volume data of any period can be queried at any time during or after the test to calculate the permeability coefficient of the period.

[0041] In the steps S10-S13, the binary search method mentioned is to divide the ordered array into two halves, compare the middle element with the target value each time, and decide whether to continue searching in the first half or the second half according to the comparison result until the target value is found or determined to be non-existent. The time complexity of this method is O (log n). The present invention uses a variant of the binary search method. This method can reduce the time required to find the maximum impermeable head difference, reduce the influence of water pressure and water immersion on the sample's impermeability during the process, and prevent the original maximum impermeable head difference of the sample from changing too much.

[0042] In the steps S15-S18, the water head is increased by 0.1 m every 10 minutes for 120 minutes, and the water head is reduced by 0.1 m every 10 minutes for 120 minutes, and the cycle is repeated 3 times to analyze the effect of short-term water pressure changes on the anti-permeability of the sample. The interval time and the water head increase or decrease value can also be adjusted according to the actual situation of the test;

[0043] In the steps S19-S22, the water head is increased by 0.1 m every hour for 12 hours, and the water head is reduced by 0.1 m every hour for 12 hours. This cycle is repeated 7 times for a total of 7 days. The effects of long-term changes in water pressure and changes in water immersion on the anti-penetration properties of the samples are analyzed. The interval time and the water head increase or decrease value may also be adjusted according to the actual situation of the test.

[0044] The present invention studies the influence of water head change, medium change and the soaking time of coal rock in water on the anti-seepage strength, permeability coefficient and permeability of coal rock, and provides technical support for scientific and safe coal mine construction and coal seam mining.

[0045] The invention can monitor, record and obtain the permeability coefficient in real time; can find the maximum impermeable head difference of the sample in a short time, and has high time efficiency; has many adjustable parameters, and can analyze the influence of single factors or combined factors of three items, namely, long-term or short-term period, changing or constant water pressure, and water immersion effect, on the anti-permeability of the sample, and has wide applicability; test water can be recycled, and the water pump can be controlled to start and stop, so as to save resources; the whole test method process is logical and flexible.

[0046] The beneficial effects of the present invention are:

[0047] 1. The present invention, "S1: Coal rock with a volume larger than the length and width of the seepage trough (43) of the test device is cut according to the length and width of the seepage trough (43) or small coal blocks and coal powder are uniformly mixed to prepare a test sample, and the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are selected according to the minimum diameter of the sample particles, and the mesh partitions (13, 15) are inserted into the transparent box (14), and the sample is placed in the seepage trough (43)". Compared with the prior art method that uses permeable stones to separate the sample and the water inlet and outlet parts, the present invention performs modular processing on the mesh partition, and can more flexibly select a mesh with a suitable aperture, while separating the sample and preventing the sample particles from flowing into the water inlet, water outlet, and circulation system, better ensure the fluidity of water and reduce the impact on the measurement of the sample permeability coefficient and permeability;

[0048] 2. In the present invention, "S2: filling water into the sealing film water filling ports (18, 21) of the front and rear side walls and the lower bottom plate of the seepage trough (43) so that the surface of the sealing film always fits the surface of the sample, preventing water from flowing through the gap between the sample and the transparent box (14)". Compared with the prior art method, the design of the sealing film can flexibly adjust the water pressure in the sealing film during the test, ensuring that its outer surface always fits the surface of the sample, ensuring that water does not flow along the gap between the sample and the side walls and bottom plate of the seepage trough, and not excessively squeezing the sample, thereby reducing the test error;

[0049] 3. The present invention, "add test water to the water supply tank (33) of the circulating water system, close the water inlet valve (7) and the transparent box water outlet valve (28), adjust the height of the water outlet tank (29) by means of the hydraulic rod (30) and the second laser rangefinder (38), make the height of the water outlet (32) and the height of the sample at the position of the water outlet trough screen partition (15) be at the same horizontal plane, set the water level of the water outlet tank (29) as the water outlet head, adjust the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), make the height of the float valve (4) The horizontal plane where the float is located is 0.1m higher than the water level of the water outlet tank (29), and is set to the water level of the second water inlet tank (2), that is, the water inlet head. The inclination angle of the transparent box base is set by the hydraulic rod (22) and the slide rail (23). The use of the hydraulic rod and the laser rangefinder can save manpower and improve the accuracy of setting the water level. Compared with the method of water flowing vertically upward from the bottom of the sample and the fixed horizontal flow method, the combination of the hydraulic rod and the slide rail can flexibly adjust the inclination angle of the transparent box base, which is suitable for different placement forms of coal and rock under natural conditions, and enhances the practicality of the test results.

[0050] 4. The present invention, "S4: if the water inlet head is higher than the height of the top of the water inlet tank, it is also necessary to install a water inlet tank sealing strip (12) on the top of the water inlet tank (40), add a cover plate (9) on the top of the seepage tank (43), and fill water through the water filling port (10) of the cover plate sealing film, so that the surface of the sealing film is also in contact with the surface of the sample, and weights are evenly placed on the cover plate to ensure that the cover plate (9) always fits the sample. If it is a pressure test condition, it is also necessary to install a water outlet tank sealing strip (16) on the top of the water outlet tank (41)". The detachable sealing strip can flexibly change the non-pressure and pressure test conditions, thereby expanding the scope of application of the test method;

[0051] 5. The present invention, "S7: open the water inlet valve (7) and the transparent box water outlet valve (28), water enters the water inlet tank (40) from the second water inlet box (2) through the water inlet hose (6), and the water infiltrates into the sample in a planar manner through the water inlet tank mesh partition (13), and observes the water inlet flow meter (42). If the flow meter reading at a certain moment is unchanged compared with the flow meter reading 1 minute ago, the height of the second water inlet box (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to increase by 0.1m", and the water infiltration into the sample can be observed at the water inlet end by reading the water inlet flow meter data, thereby reducing the waiting time caused by the inability or difficulty of water to infiltrate into the sample due to the unreasonable head difference, and improving the time efficiency of the test;

[0052] 6. In the present invention, “S10: define the water level change value as Δh, the initial Δh = (h1-h2) / 2, measure the maximum impermeable head difference of the sample by dichotomy, the water head H1 is reduced by Δh / 2, and the new water head change value Δh 新= Δh / 2, after the water inlet head H1 drops to the set value, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12; S11: the water inlet head H1 increases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 = Δh / 2, if the reading of the water inlet flow meter (42) does not change for 1 minute, repeat step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12; S12: the water inlet head H1 decreases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 = Δh / 2, if the reading of the water inlet flow meter (42) does not change for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, repeat step S12; S13: After steps S10-S12, in order to accurately calculate the maximum impermeable head difference to centimeters, when Δh≦0.01m, if the reading of the water inlet flow meter (42) does not change for 1 minute, that is, no water has infiltrated into the sample for 1 minute, the difference between H1 and H2 at this time is the sample The maximum impermeable head difference of the sample. If the reading of the water inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within one minute, the difference between H1 and H2 minus 0.01m at this time is the maximum impermeable head difference of the sample; S14: adjust the height of the second water inlet tank (2) by the hydraulic rod (5) and the first laser rangefinder (37), and set H1 to the height of H2 plus the maximum impermeable head difference of the sample. The test is continued for 7 days to observe whether the water can The permeate passes through the sample and enters the water outlet tank (41), and the flow rate is continuously recorded by the water outlet flow meter (31). Step S9 is performed every 1 hour to calculate the permeability coefficient and permeability of the sample, and whether the permeability coefficient and permeability change, and the influence of the constant water pressure and water immersion on the sample's anti-permeability is analyzed. After 7 days, steps S10-S13 are repeated to find the new maximum impermeable head difference of the sample under the constant water pressure and water immersion. Compared with the existing method, the binary design can find the maximum impermeable head difference of the sample with higher time efficiency, reduce the influence of the water pressure and water immersion on the sample's anti-permeability during the test, and reduce the original maximum impermeable head difference of the sample. Change too much; at the same time, continue to test with the same sample, measure the permeability coefficient, permeability, and the new maximum impermeable head difference of the sample under the constant water pressure and water immersion, and analyze the influence of the constant water pressure and immersion on the sample's anti-permeability.

[0053] 7. In the present invention, S18 and S22 also use the dichotomy method, which can improve the time efficiency of finding the original maximum impermeable water head difference of the sample, the new maximum impermeable water head difference of the sample under the action of short-term changing water pressure, and the new maximum impermeable water head difference of the sample under long-term changing water pressure and water immersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a front view of the experimental test device in the embodiment of the present invention;

[0055] Figure 2 It is a side view of the bottom plate or side wall of the seepage trough of the test device in the embodiment of the present invention.

[0056] Reference numerals:

[0057] 1-first water inlet tank, 2-second water inlet tank, 3-water supply hose, 4-float valve, 5-hydraulic rod, 6-water inlet hose, 7-water inlet valve, 8-cover handle, 9-cover, 10-cover sealing film filling port, 11-cover sealing film, 12-water inlet tank sealing strip, 13-water inlet tank mesh partition, 14-transparent box, 15-water outlet tank mesh partition, 16-water outlet tank sealing strip, 17-water outlet tank handle, 18-seepage tank side sealing film filling port, 19-water inlet tank handle, 20-transparent box base, 21-seepage tank bottom plate sealing film filling port, 22-transparent Hydraulic rod of the exposed box base, 23-slide rail, 24-transparent box base rotating shaft, 25-steel frame support, 26-universal wheel, 27-transparent box water outlet hose, 28-transparent box water outlet valve, 29-water outlet tank, 30-water outlet tank hydraulic rod, 31-water outlet flow meter, 32-water outlet, 33-circulating water supply tank, 34-pre-filter, 35-circulating water supply hose, 36-water pump, 37-first laser rangefinder, 38-second laser rangefinder, 39-water level controller, 40-water inlet trough, 41-water outlet trough, 42-water inlet flow meter, 43-seepage trough. DETAILED DESCRIPTION

[0058] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0059] Embodiment 1:

[0060] like Figure 1 and Figure 2 As shown, a method for testing the anti-permeability of low-permeability coal rock media includes the following steps:

[0061] S1: Coal rock with a volume larger than the length and width of the seepage trough (43) of the test device is cut according to the length and width of the seepage trough (43) or small coal blocks and coal powder are uniformly mixed to prepare a test sample, and the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are selected according to the minimum diameter of the sample particles, and the mesh partitions (13, 15) are inserted into the transparent box (14), and the sample is placed in the seepage trough (43);

[0062] S2: Filling water into the sealing film water filling ports (18, 21) on the front and rear side walls and the lower bottom plate of the seepage trough (43) so that the surface of the sealing film always fits the surface of the sample, thereby preventing water from flowing through the gap between the sample and the transparent box (14);

[0063] S3: Add test water to the water supply tank (33) of the circulating water system, close the water inlet valve (7) and the transparent box outlet valve (28), adjust the height of the water outlet tank (29) by means of the hydraulic rod (30) and the second laser rangefinder (38), so that the height of the water outlet (32) and the height of the sample at the position of the water outlet trough screen partition (15) are at the same horizontal plane, set as the water level of the water outlet tank (29), that is, the water outlet head, adjust the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), so that the horizontal plane where the float of the float valve (4) is located is 0.1m higher than the water level of the water outlet tank (29), set as the water level of the second water inlet tank (2), that is, the water inlet head, and set the inclination angle of the transparent box base by means of the hydraulic rod (22) and the slide rail (23);

[0064] S4: If the water inlet head is higher than the height of the top of the water inlet tank, it is also necessary to install a water inlet tank sealing strip (12) on the top of the water inlet tank (40), cover the top of the seepage tank (43) with a cover plate (9), and fill water through the water filling port (10) of the cover plate sealing film. Similarly, the surface of the sealing film is made to fit the surface of the sample, and weights are evenly placed on the cover plate to ensure that the cover plate (9) always fits the sample. If it is a pressure test condition, it is also necessary to install a water outlet tank sealing strip (16) on the top of the water outlet tank (41);

[0065] S5: starting the water pump (36), passing water from the circulating water supply tank (33) through the pre-filter (34), filtering the particles in the water, and then transporting the water to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is provided with a water level controller (39). When the water level in the first water inlet tank (1) is lower than half, the water level controller (39) controls the water pump (36) to operate, and stops operating after the first water inlet tank (1) is filled. The process of the water pump (36) supplying water to the first water inlet tank (1) is cyclically carried out;

[0066] S6: water from the first water inlet tank (1) enters the second water inlet tank (2) through the water supply hose (3). When the water reaches the height of the float valve (4), the float valve (4) controls the water supply hose (3) to stop supplying water. When the water level is lower than the set water level, the float valve (4) controls the water supply hose (3) to supply water. The process of the float valve (4) controlling the water supply hose (3) to supply water and stop supplying water is repeated;

[0067] S7: Open the water inlet valve (7) and the transparent box water outlet valve (28), and water enters the water inlet tank (40) from the second water inlet box (2) through the water inlet hose (6). The water infiltrates into the sample in a planar manner through the water inlet tank screen partition (13). Observe the water inlet flow meter (42). If the flow meter reading at a certain moment does not change compared with the flow meter reading 1 minute ago, adjust the height of the second water inlet tank (2) by the hydraulic rod (5) and the first laser rangefinder (37) to increase it by 0.1m.

[0068] S8: Repeat the test process of S4-S7 until water enters the water outlet tank (41). The water inlet head set when water first flows into the water outlet tank (41) is defined as h1, and the water outlet head is defined as h2. Water enters the water outlet tank (29) through the transparent box water outlet hose (27). When the water level reaches the water outlet (32), it flows out to the circulating water supply tank (33), completing the recycling of the test water. The water volume of the outlet water is measured and recorded by the water outlet flow meter (31);

[0069] S9: Read the water outlet flow meter (31) data Q1 and Q2 at time t1 and t2 (t2>t1). The flow meter reading is the total flow from the start of the test to a certain time point. Therefore, the flow from t1 to t2 is the difference between the flow meter readings at the two time points (Q2-Q1). The permeability coefficient and permeability of the sample are obtained according to the following formula:

[0070]

[0071] Where: K is the permeability coefficient of the sample, in m / s; t1 and t2 are the times for reading the flow meter data, Q1 is the flow meter data at t1, in m 3 ; Q2 is the flow meter data at time t2, unit: m 3 ; L is the distance between the inlet gauze partition (13) and the outlet gauze partition (15), in m; A is the area of ​​the outlet cross section, in m 2 ; H1 is the water inlet head, unit is m; H2 is the water outlet head, unit is m; k is the permeability of the sample, unit is m 2 ; η is the dynamic viscosity of water, unit is Pascal seconds (Pa·s); ρ is the density of the sample, unit is kg / m 3 ; g is the acceleration due to gravity, unit is m / s 2 .

[0072] S10: Define the water level change value as Δh, initial Δh = (h1-h2) / 2, measure the maximum impermeable head difference of the sample by dichotomy, the water head H1 is reduced by Δh / 2, and the new water head change value Δh 新 =Δh / 2, after the water inlet head H1 drops to the set value, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12;

[0073] S11: Inlet head H1 increases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, repeat step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12;

[0074] S12: Inlet head H1 decreases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, repeat step S12;

[0075] S13: After steps S10-S12, in order to accurately calculate the maximum impermeable head difference to centimeters, when Δh≦0.01m, if the reading of the water inlet flow meter (42) does not change for 1 minute, that is, no water infiltrates into the sample for 1 minute, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample; if the reading of the water inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within 1 minute, the difference between H1 and H2 minus 0.01m at this time is the maximum impermeable head difference of the sample;

[0076] S14: adjusting the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), and setting H1 to a height of H2 plus the maximum impermeable water head difference of the sample;

[0077] S15: Every 10 minutes, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to increase by 0.1 m, and this continues for 120 minutes;

[0078] S16: Every 10 minutes, the height of the second water inlet tank (2) is adjusted by reducing it by 0.1 m through the hydraulic rod (5) and the first laser rangefinder (37), and this continues for 120 minutes;

[0079] S17: The test is performed once in steps S15 and S16 as one cycle, and the cycle is repeated 3 times. The test lasts for a total of 12 hours. Step 9 is performed to calculate the permeability coefficient and permeability of the sample, and their changes are observed. Steps S10-S13 are repeated to find the new maximum impermeable head difference of the sample under the action of short-term water pressure changes, and the influence of short-term water pressure changes on the sample's anti-permeability is analyzed;

[0080] This embodiment is an implementation method for analyzing the effect of short-term water pressure changes on the sample's anti-permeability. Compared with the existing method, the dichotomy method can reduce the time required to find the maximum impermeable head difference, change the head difference in a short time, and minimize the effect of water immersion on the sample's anti-permeability. The sample's permeability coefficient and permeability are calculated, and the changes in the sample's original maximum impermeable head difference and the sample's new maximum impermeable head difference under the action of short-term water pressure changes are analyzed to explore the effect of water pressure changes caused by changes in the head difference on the sample's anti-permeability.

[0081] Embodiment 2:

[0082] like Figure 1 and Figure 2 As shown, a method for testing the anti-permeability of low-permeability coal rock media includes the following steps:

[0083] S1: Coal rock with a volume larger than the length and width of the seepage trough (43) of the test device is cut according to the length and width of the seepage trough (43) or small coal blocks and coal powder are uniformly mixed to prepare a test sample, and the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are selected according to the minimum diameter of the sample particles, and the mesh partitions (13, 15) are inserted into the transparent box (14), and the sample is placed in the seepage trough (43);

[0084] S2: Filling water into the sealing film water filling ports (18, 21) on the front and rear side walls and the lower bottom plate of the seepage trough (43) so that the surface of the sealing film always fits the surface of the sample, thereby preventing water from flowing through the gap between the sample and the transparent box (14);

[0085] S3: Add test water to the water supply tank (33) of the circulating water system, close the water inlet valve (7) and the transparent box outlet valve (28), adjust the height of the water outlet tank (29) by means of the hydraulic rod (30) and the second laser rangefinder (38), so that the height of the water outlet (32) and the height of the sample at the position of the water outlet trough screen partition (15) are at the same horizontal plane, set as the water level of the water outlet tank (29), that is, the water outlet head, adjust the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), so that the horizontal plane where the float of the float valve (4) is located is 0.1m higher than the water level of the water outlet tank (29), set as the water level of the second water inlet tank (2), that is, the water inlet head, and set the inclination angle of the transparent box base by means of the hydraulic rod (22) and the slide rail (23);

[0086] S4: If the water inlet head is higher than the height of the top of the water inlet tank, it is also necessary to install a water inlet tank sealing strip (12) on the top of the water inlet tank (40), cover the top of the seepage tank (43) with a cover plate (9), and fill water through the water filling port (10) of the cover plate sealing film. Similarly, the surface of the sealing film is made to fit the surface of the sample, and weights are evenly placed on the cover plate to ensure that the cover plate (9) always fits the sample. If it is a pressure test condition, it is also necessary to install a water outlet tank sealing strip (16) on the top of the water outlet tank (41);

[0087] S5: starting the water pump (36), passing water from the circulating water supply tank (33) through the pre-filter (34), filtering the particles in the water, and then transporting the water to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is provided with a water level controller (39). When the water level in the first water inlet tank (1) is lower than half, the water level controller (39) controls the water pump (36) to operate, and stops operating after the first water inlet tank (1) is filled. The process of the water pump (36) supplying water to the first water inlet tank (1) is cyclically carried out;

[0088] S6: water from the first water inlet tank (1) enters the second water inlet tank (2) through the water supply hose (3). When the water reaches the height of the float valve (4), the float valve (4) controls the water supply hose (3) to stop supplying water. When the water level is lower than the set water level, the float valve (4) controls the water supply hose (3) to supply water. The process of the float valve (4) controlling the water supply hose (3) to supply water and stop supplying water is repeated;

[0089] S7: Open the water inlet valve (7) and the transparent box water outlet valve (28), and water enters the water inlet tank (40) from the second water inlet box (2) through the water inlet hose (6). The water infiltrates into the sample in a planar manner through the water inlet tank screen partition (13). Observe the water inlet flow meter (42). If the flow meter reading at a certain moment does not change compared with the flow meter reading 1 minute ago, adjust the height of the second water inlet tank (2) by the hydraulic rod (5) and the first laser rangefinder (37) to increase it by 0.1m.

[0090] S8: Repeat the test process of S4-S7 until water enters the water outlet tank (41). The water inlet head set when water first flows into the water outlet tank (41) is defined as h1, and the water outlet head is defined as h2. Water enters the water outlet tank (29) through the transparent box water outlet hose (27). When the water level reaches the water outlet (32), it flows out to the circulating water supply tank (33), completing the recycling of the test water. The water volume of the outlet water is measured and recorded by the water outlet flow meter (31);

[0091] S9: Read the water outlet flow meter (31) data Q1 and Q2 at time t1 and t2 (t2>t1). The flow meter reading is the total flow from the start of the test to a certain time point. Therefore, the flow from t1 to t2 is the difference between the flow meter readings at the two time points (Q2-Q1). The permeability coefficient and permeability of the sample are obtained according to the following formula:

[0092]

[0093] Where: K is the permeability coefficient of the sample, in m / s; t1 and t2 are the times for reading the flow meter data, Q1 is the flow meter data at t1, in m 3 ; Q2 is the flow meter data at time t2, unit: m 3 ; L is the distance between the inlet gauze partition (13) and the outlet gauze partition (15), in m; A is the area of ​​the outlet cross section, in m 2 ; H1 is the water inlet head, unit is m; H2 is the water outlet head, unit is m; k is the permeability of the sample, unit is m 2 ; η is the dynamic viscosity of water, unit is Pascal seconds (Pa·s); ρ is the density of the sample, unit is kg / m 3 ; g is the acceleration due to gravity, unit is m / s 2 .

[0094] S10: Define the water level change value as Δh, initial Δh = (h1-h2) / 2, measure the maximum impermeable head difference of the sample by dichotomy, the water head H1 is reduced by Δh / 2, and the new water head change value Δh 新 =Δh / 2, after the water inlet head H1 drops to the set value, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12;

[0095] S11: Inlet head H1 increases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, repeat step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12;

[0096] S12: Inlet head H1 decreases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, repeat step S12;

[0097] S13: After steps S10-S12, in order to accurately calculate the maximum impermeable head difference to centimeters, when Δh≦0.01m, if the reading of the water inlet flow meter (42) does not change for 1 minute, that is, no water infiltrates into the sample for 1 minute, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample; if the reading of the water inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within 1 minute, the difference between H1 and H2 minus 0.01m at this time is the maximum impermeable head difference of the sample;

[0098] S14: adjusting the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), and setting H1 to a height of H2 plus the maximum impermeable water head difference of the sample;

[0099] S15: Every 1 hour, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to increase by 0.1 m, and this continues for 12 hours;

[0100] S16: Every 1 hour, the height of the second water inlet tank (2) is adjusted by reducing it by 0.1 m through the hydraulic rod (5) and the first laser rangefinder (37), and this is continued for 12 hours;

[0101] S17: The test is performed with steps S56 and S16 as one cycle, and the cycle is repeated 7 times. The test lasts for 7 days in total. Step 9 is performed to calculate the permeability coefficient and permeability of the sample and observe their changes. Steps S10-S13 are repeated to find the new maximum impermeable head difference of the sample under the long-term changing water pressure and water immersion, and the influence of the long-term changing water pressure and water immersion on the anti-permeability of the sample is analyzed.

[0102] This embodiment is an implementation method for analyzing the effects of long-term changes in water pressure and changes in the softening effect of water on the anti-permeability of the sample. The water head difference is increased and decreased over a long period of time, and this cycle is repeated to calculate the permeability coefficient and permeability of the sample. The original maximum impermeable water head difference of the sample, the long-term changes in water pressure, and the changes in the new maximum impermeable water head difference of the sample under water immersion are analyzed to explore the effects of long-term changes in water pressure and water immersion on the anti-permeability of the sample.

[0103] Embodiment 3:

[0104] like Figure 1 and Figure 2 As shown, a method for testing the anti-permeability of low-permeability coal rock media includes the following steps:

[0105] S1: Coal rock with a volume larger than the length and width of the seepage trough (43) of the test device is cut according to the length and width of the seepage trough (43) or small coal blocks and coal powder are uniformly mixed to prepare a test sample, and the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are selected according to the minimum diameter of the sample particles, and the mesh partitions (13, 15) are inserted into the transparent box (14), and the sample is placed in the seepage trough (43);

[0106] S2: Filling water into the sealing film water filling ports (18, 21) on the front and rear side walls and the lower bottom plate of the seepage trough (43) so that the surface of the sealing film always fits the surface of the sample, thereby preventing water from flowing through the gap between the sample and the transparent box (14);

[0107] S3: Add test water to the water supply tank (33) of the circulating water system, close the water inlet valve (7) and the transparent box outlet valve (28), adjust the height of the water outlet tank (29) by means of the hydraulic rod (30) and the second laser rangefinder (38), so that the height of the water outlet (32) and the height of the sample at the position of the water outlet trough screen partition (15) are at the same horizontal plane, set as the water level of the water outlet tank (29), that is, the water outlet head, adjust the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), so that the horizontal plane where the float of the float valve (4) is located is 0.1m higher than the water level of the water outlet tank (29), set as the water level of the second water inlet tank (2), that is, the water inlet head, and set the inclination angle of the transparent box base by means of the hydraulic rod (22) and the slide rail (23);

[0108] S4: If the water inlet head is higher than the height of the top of the water inlet tank, it is also necessary to install a water inlet tank sealing strip (12) on the top of the water inlet tank (40), cover the top of the seepage tank (43) with a cover plate (9), and fill water through the water filling port (10) of the cover plate sealing film, so that the surface of the sealing film is in contact with the surface of the sample, and evenly place weights on the cover plate to ensure that the cover plate (9) always fits the sample;

[0109] S5: starting the water pump (36), passing water from the circulating water supply tank (33) through the pre-filter (34), filtering the particles in the water, and then transporting the water to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is provided with a water level controller (39). When the water level in the first water inlet tank (1) is lower than half, the water level controller (39) controls the water pump (36) to operate, and stops operating after the first water inlet tank (1) is filled. The process of the water pump (36) supplying water to the first water inlet tank (1) is cyclically carried out;

[0110] S6: water from the first water inlet tank (1) enters the second water inlet tank (2) through the water supply hose (3). When the water reaches the height of the float valve (4), the float valve (4) controls the water supply hose (3) to stop supplying water. When the water level is lower than the set water level, the float valve (4) controls the water supply hose (3) to supply water. The process of the float valve (4) controlling the water supply hose (3) to supply water and stop supplying water is repeated;

[0111] S7: Open the water inlet valve (7) and the transparent box water outlet valve (28), and water enters the water inlet tank (40) from the second water inlet box (2) through the water inlet hose (6). The water infiltrates into the sample in a planar manner through the water inlet tank screen partition (13). Observe the water inlet flow meter (42). If the flow meter reading at a certain moment does not change compared with the flow meter reading 1 minute ago, adjust the height of the second water inlet tank (2) by the hydraulic rod (5) and the first laser rangefinder (37) to increase it by 0.1m.

[0112] S8: Repeat the test process of S4-S7 until water enters the water outlet tank (41). The water inlet head set when water first flows into the water outlet tank (41) is defined as h1, and the water outlet head is defined as h2. Water enters the water outlet tank (29) through the transparent box water outlet hose (27). When the water level reaches the water outlet (32), it flows out to the circulating water supply tank (33), completing the recycling of the test water. The water volume of the outlet water is measured and recorded by the water outlet flow meter (31);

[0113] S9: Read the water outlet flow meter (31) data Q1 and Q2 at time t1 and t2 (t2>t1). The flow meter reading is the total flow from the start of the test to a certain time point. Therefore, the flow from t1 to t2 is the difference between the flow meter readings at the two time points (Q2-Q1). The permeability coefficient and permeability of the sample are obtained according to the following formula:

[0114]

[0115] Where: K is the permeability coefficient of the sample, in m / s; t1 and t2 are the times for reading the flow meter data, Q1 is the flow meter data at t1, in m 3 ; Q2 is the flow meter data at time t2, unit: m 3 ; L is the distance between the inlet gauze partition (13) and the outlet gauze partition (15), in m; A is the area of ​​the outlet cross section, in m 2 ; H1 is the water inlet head, unit is m; H2 is the water outlet head, unit is m; k is the permeability of the sample, unit is m 2 ; η is the dynamic viscosity of water, unit is Pascal seconds (Pa·s); ρ is the density of the sample, unit is kg / m 3 ; g is the acceleration due to gravity, unit is m / s 2 .

[0116] S10: Define the water level change value as Δh, initial Δh = (h1-h2) / 2, measure the maximum impermeable head difference of the sample by dichotomy, the water head H1 is reduced by Δh / 2, and the new water head change value Δh 新 =Δh / 2, after the water inlet head H1 drops to the set value, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12;

[0117] S11: Inlet head H1 increases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, repeat step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, proceed to step S12;

[0118] S12: Inlet head H1 decreases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within 1 minute, repeat step S12;

[0119] S13: After steps S10-S12, in order to accurately calculate the maximum impermeable head difference to centimeters, when Δh≦0.01m, if the reading of the water inlet flow meter (42) does not change for 1 minute, that is, no water infiltrates into the sample for 1 minute, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample; if the reading of the water inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within 1 minute, the difference between H1 and H2 minus 0.01m at this time is the maximum impermeable head difference of the sample;

[0120] S14: The height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37), and H1 is set to the height of H2 plus the maximum impermeable water head difference of the sample. The test is continued for 7 days to observe whether water can penetrate through the sample into the water outlet tank (41). The water outlet flow meter (31) continuously records the flow rate. Step S9 is performed every 1 hour to calculate the permeability coefficient and permeability of the sample, and observe whether the permeability coefficient and permeability change. The influence of the constant water pressure and water immersion on the anti-permeability of the sample is analyzed. After 7 days, steps S10-S13 are repeated to find the new maximum impermeable water head difference of the sample under the constant water pressure and water immersion.

[0121] This embodiment is an implementation method for analyzing the effects of constant water pressure and water immersion on the anti-permeability of samples. The water head difference is fixed over a long period of time, the permeability coefficient and permeability of the sample are calculated, and the changes in the original maximum impermeable water head difference of the sample and the new maximum impermeable water head difference of the sample under the effects of constant water pressure and water immersion are analyzed to explore the effects of constant water pressure and water immersion on the anti-permeability of the sample.

[0122] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for testing the anti-permeability of low-permeability coal and rock media, characterized in that: The following steps are involved: S1: Coal rock with a volume larger than the length and width of the seepage trough (43) of the test device is cut according to the length and width of the seepage trough (43) or small coal blocks and coal powder are uniformly mixed to prepare a test sample, and the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are selected according to the minimum diameter of the sample particles, and the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are inserted into the transparent box (14), and the sample is placed in the seepage trough (43); S2: Filling water into the sealing film water filling port (18) on the side of the seepage trough and the sealing film water filling port (21) on the bottom plate of the seepage trough (43) so that the surface of the sealing film always fits the surface of the sample; S3: Add test water to the water supply tank (33) of the circulating water system, close the water inlet valve (7) and the water outlet valve (28) of the transparent box (14), adjust the height of the water outlet box (29) by means of the water outlet box hydraulic rod (30) and the second laser rangefinder (38), so that the height of the water outlet (32) and the height of the sample at the position of the water outlet trough screen partition (15) are at the same horizontal plane, set to the water level of the water outlet box (29), i.e. the water outlet head, adjust the height of the second water inlet box (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), so that the horizontal plane where the float of the float valve (4) is located is higher than the water level of the water outlet box (29), set to the water level of the second water inlet box (2), i.e. the water inlet head, and set the inclination angle of the transparent box base by means of the transparent box base hydraulic rod (22) and the slide rail (23); S4: If the water inlet head is higher than the height of the top of the water inlet tank, it is also necessary to install a water inlet tank sealing strip (12) on the top of the water inlet tank (40), cover the top of the seepage tank (43) with a cover plate (9), and fill water through the water filling port (10) of the cover plate sealing film, so that the surface of the sealing film is in contact with the surface of the sample, and evenly place weights on the cover plate to ensure that the cover plate (9) always fits the sample; S5: starting the water pump (36), passing water from the circulating water supply tank (33) through the pre-filter (34), filtering the particles in the water, and then transporting it to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is provided with a water level controller (39). When the water level in the first water inlet tank (1) is lower than half, the water level controller (39) controls the water pump (36) to operate, and stops operating after the first water inlet tank (1) is filled. The process of the water pump (36) supplying water to the first water inlet tank (1) is cyclically carried out; S6: water from the first water inlet tank (1) enters the second water inlet tank (2) through the water supply hose (3). When the water reaches the height of the float valve (4), the float valve (4) controls the water supply hose (3) to stop supplying water. When the water level is lower than the set water level, the float valve (4) controls the water supply hose (3) to supply water. The process of the float valve (4) controlling the water supply hose (3) to supply water and stop supplying water is repeated; S7: Open the water inlet valve (7) and the transparent box water outlet valve (28), and water enters the water inlet tank (40) from the second water inlet box (2) through the water inlet hose (6). The water infiltrates into the sample in a planar manner through the water inlet tank screen partition (13). Observe the water inlet flow meter (42). If the flow meter reading at a certain moment does not change compared with the flow meter reading before a preset time, adjust the height of the second water inlet tank (2) through the hydraulic rod (5) and the first laser rangefinder (37) to increase the preset height. S8: Repeat the test process of S4-S7 until water enters the water outlet tank (41). The water inlet head set when water first flows into the water outlet tank (41) is defined as h1, and the water outlet head is defined as h2. Water enters the water outlet tank (29) through the transparent box water outlet hose (27). When the water level reaches the water outlet (32), it flows out to the circulating water supply tank (33), completing the recycling of the test water. The water volume of the outlet water is measured and recorded by the water outlet flow meter (31); S9: Read the water outlet flow meter (31) data Q1 and Q2 at time t1 and t2, where t2>t1. The flow meter reading is the total flow from the start of the test to a certain time point. Therefore, the flow from t1 to t2 is the difference between the flow meter readings at the two time points (Q2-Q1). The permeability coefficient and permeability of the sample are obtained according to the following formula: Wherein: K is the permeability coefficient of the sample; t1 and t2 are the times for reading the flow meter data, Q1 is the flow meter data at time t1; Q2 is the flow meter data at time t2; L is the distance between the gauze partition (13) of the water inlet trough and the gauze partition (15) of the water outlet trough; A is the area of ​​the water outlet cross section; H1 is the water inlet head; H2 is the water outlet head; k is the permeability of the sample; η is the dynamic viscosity coefficient of water; ρ is the density of the sample; g is the acceleration of gravity; S10: Define the water level change value as Δh, initial Δh = (h1-h2) / 2, measure the maximum impermeable head difference of the sample by dichotomy, the water head H1 is reduced by Δh / 2, and the new water head change value Δh 新 =Δh / 2, after the water inlet head H1 drops to the set value, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the water inlet flow meter (42) changes within the preset time, proceed to step S12; S11: Inlet head H1 increases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) remains unchanged for 1 minute, repeat step S11; if the reading of the water inlet flow meter (42) changes within the preset time, proceed to step S12; S12: Inlet head H1 decreases by Δh 新 / 2, Δh is assigned to Δh 新 / 2, the new head change value Δh 新 =Δh / 2, if the reading of the water inlet flow meter (42) does not change within the continuous preset time, proceed to step S11; if the reading of the water inlet flow meter (42) changes within the preset time, repeat step S12; S13: After steps S10-S12, in order to accurately calculate the maximum impermeable head difference to centimeters, when Δh≤0.01m, if the reading of the water inlet flow meter (42) does not change for a continuous preset time, that is, no water infiltrates into the sample for a continuous preset time, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample; if the reading of the water inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within the preset time, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample; S14: adjusting the height of the second water inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37), setting H1 to the height of H2 plus the maximum impermeable water head difference of the sample, and continuing the test for N days to observe whether water can penetrate through the sample into the water outlet tank (41), and continuously recording the flow rate by the water outlet flow meter (31), and performing step S9 to calculate the permeability coefficient and permeability of the sample every M hours, observing whether the permeability coefficient and permeability change, and analyzing the influence of the constant water pressure and water immersion on the anti-permeability of the sample, and repeating steps S10-S13 after N days to find the new maximum impermeable water head difference of the sample under the constant water pressure and water immersion; S15: re-prepare the sample, perform steps S1-S13, and set H1 to the height of H2 plus the maximum impermeable head difference of the sample; S16: Every K minutes, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to increase the preset height for a certain period of time; S17: every K minutes, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to reduce the preset height for a certain period of time; S18: The test is performed by performing steps S16 and S17 once as one cycle, and the cycle is repeated multiple times. The test lasts for several hours in total, and step 9 is performed to calculate the permeability coefficient and permeability of the sample, and observe their changes. Steps S10-S13 are repeated to find the new maximum impermeable head difference of the sample under the action of short-term water pressure changes, and the influence of short-term water pressure changes on the sample's anti-permeability is analyzed; S19: Re-prepare the sample, perform steps S1-S13, and set H1 to the height of H2 plus the maximum impermeable water head difference of the sample; S20: Every M hours, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to increase the preset height for a certain period of time; S21: every M hours, the height of the second water inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) to reduce the preset height for a certain period of time; S22: The test is carried out with steps S20 and S21 as one cycle. The cycle is repeated multiple times. The test lasts for several days. Step 9 is carried out to calculate the permeability coefficient and permeability of the sample and observe their changes. Steps S10-S13 are repeated to find the new maximum impermeable head difference of the sample under the long-term changing water pressure and water immersion, and the influence of the long-term changing water pressure and water immersion on the anti-permeability of the sample is analyzed.

2. The low permeability coal rock medium anti-permeability test method according to claim 1 is characterized in that: In step S1, the test device comprises a circulating water system, a water inlet system, a test box system and a water outlet system. The four systems are arranged on a steel frame support (25). Two universal wheels (26) are installed at the bottom of the steel frame support (25). The circulating water system is connected to a water pump (36) through a pre-filter (34) and a circulating water supply hose (35). The water pump (36) is connected to a first water inlet tank (1) of the water inlet system. A water level controller (39) is located on a side wall of the first water inlet tank (1). The first water inlet tank (1) is connected to a second water inlet tank (2) through a water supply hose (3). The second water inlet tank (2) is connected to the water inlet tank (40) of the transparent box (14) of the test box system through a water inlet hose (6), a water inlet valve (7) and a water inlet flow meter (42) are arranged on the water inlet hose (6), a water inlet tank sealing strip (12) is arranged on the top of the water inlet tank (40), and the water inlet tank (40) is separated from the seepage tank (43) by a water inlet tank mesh partition plate (13). The transparent box (14) is placed on the transparent box base (20), the bottom of the transparent box base (20) is connected to the transparent box base hydraulic rod (22) and the transparent box base rotating shaft (24), the transparent box base hydraulic rod (22) is connected to the slide rail (23), the top of the seepage groove (43) is provided with a cover plate (9), the cover plate (9) has a cover plate handle (8), a cover plate sealing water filling port (10) and a cover plate sealing film (11), the front and rear side walls of the seepage groove (43) have a seepage groove side water filling port (18) and a sealing film, and the bottom plate of the seepage groove (43) has a seepage groove bottom plate sealing film The invention relates to a water filling port (21) and a sealing film, wherein the transparent box (14) is separated from the water outlet trough (41) by a water outlet trough mesh partition (15), the top of the water outlet trough (41) is provided with a water outlet trough sealing strip (16), the water outlet trough (41) is connected to a water outlet tank (29) of a water outlet system through a transparent box water outlet hose (27), the transparent box water outlet hose (27) is provided with a transparent box water outlet valve (28), the bottom of the water outlet tank (29) is connected to a water outlet tank hydraulic rod (30), the water outlet (32) is connected to a circulating water supply tank, and the water outlet (32) is provided with a water outlet flow meter (31).

3. The low permeability coal rock medium anti-permeability test method according to claim 1, characterized in that: In the step S1, the mesh apertures of the water inlet trough mesh partition (13) and the water outlet trough mesh partition (15) are replaceable, ensuring that the seepage trough (43), the water inlet trough (40) and the water outlet trough (41) are separated, and particles in the sample cannot enter the water inlet trough (40) and the water outlet trough (41), so that water can flow into the sample in a planar shape and flow out to the water outlet trough (41).

4. The low permeability coal rock medium anti-permeability test method according to claim 1, characterized in that: In the step S3, the water supply tank (33) of the circulating water system is the replenishment point and starting point of the test water, and is connected to the water inlet system and the water outlet system to ensure the recycling of the test water.

5. The low permeability coal rock medium anti-permeability test method according to claim 1, characterized in that: In the steps S10-S13, the binary search method mentioned is to divide the ordered array into two halves, compare the middle element with the target value each time, and decide whether to continue searching in the first half or the second half according to the comparison result, until the target value is found or determined not to exist.

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