Low permeability coal rock medium impermeability test test method

Abstract

This invention discloses a method for testing the impermeability of low-permeability coal and rock media, comprising: preparing a coal and rock sample and placing the sample into a seepage tank; filling the sealing membrane with water to ensure that the tank wall and bottom plate are in contact with the sample surface; adding test water and setting the inlet and outlet water heads and the tilt angle of the transparent tank base; starting the water pump to supply water; water flowing from the circulating water supply system through the inlet system and the test tank system; adjusting the inlet water head; until water enters the outlet tank of the test tank system; reading the data from the outlet flow meter, calculating the sample permeability coefficient, and using the bisection method to find the maximum impermeable head difference of the sample; analyzing the influence of constant water pressure and water immersion on the sample's impermeability; preparing another sample and repeating the process, adjusting the inlet water head at short time intervals to analyze the influence of short-term water pressure changes on the sample's impermeability; preparing another sample and repeating the process, adjusting the inlet water head at longer time intervals to analyze the influence of long-term water pressure changes and water immersion on the sample's impermeability; this invention can be used to test the impermeability of coal and rock media.

Description

Technical Field

[0001] This invention relates to the field of indoor coal and rock testing technology, and in particular to a test method for permeability resistance testing of low-permeability coal and rock media. Background Technology

[0002] my country possesses relatively abundant coal resources, but due to significant differences in the geological characteristics of coal seams and exceptionally complex hydrogeological conditions, coal mining faces enormous technical challenges. During coal mine construction and mining, the excavation and modification of surface and underground rock strata alter the surface runoff and groundwater flow fields of the surrounding area. In water-rich strata and aquifer geological structures such as aquifer faults, water permeability may occur. Excavating coal seams can thin or eliminate the relative aquitard between the coal mining area and the aquifer, reducing the distance between them. Especially in underwater coal mining, when the hydraulic head difference and hydraulic gradient increase, the coal seam can ultimately undergo seepage failure under varying water pressure and immersion, leading to groundwater influx into the mining area and causing casualties and property damage. Therefore, determining the permeability coefficient and permeability of coal and rock, exploring their impermeability strength, and studying how seepage failure occurs under water pressure and immersion conditions have become urgent problems to be solved. Summary of the Invention

[0003] To address the problems existing in the prior art, the purpose of this invention is to provide a test method for the permeability resistance of low-permeability coal and rock media. This invention can test the permeability resistance of coal and rock media.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a test method for permeability resistance of low-permeability coal and rock media, comprising the following steps:

[0005] S1: Cut coal and rock with a volume larger than the length and width of the seepage trough (43) of the test device according to the length and width of the seepage trough (43) or prepare test samples by uniformly mixing small coal blocks and coal powder. According to the minimum diameter of the sample particles, select the mesh aperture of the inlet mesh partition (13) and the outlet mesh partition (15). Insert the inlet mesh partition (13) and the outlet mesh partition (15) into the transparent box (14) and put the sample into the seepage trough (43).

[0006] S2: Fill the sealing membrane water inlet (18) on the side of the seepage tank (43) and the sealing membrane water inlet (21) on the bottom plate of the seepage tank with water so that the surface of the sealing membrane always adheres to the sample surface.

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

[0008] S4: If the water head is higher than the top height of the water tank, a water tank sealing strip (12) needs to be installed on the top of the water tank (40), and a cover plate (9) needs to be installed on the top of the seepage tank (43). Water is filled through the water filling port (10) of the cover plate sealing film. Similarly, the surface of the sealing film is attached to the sample surface, and weights are evenly placed on the cover plate to ensure that the cover plate (9) is always attached to the sample.

[0009] S5: Start the water pump (36) to send water from the circulating water supply tank (33) through the pre-filter (34) to filter out particulate matter in the water and then send it to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is equipped 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 run, and stops running after filling the first water inlet tank (1). The process of the water pump (36) supplying water to the first water inlet tank (1) is repeated.

[0010] S6: Water from the first water tank (1) enters the second water 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 inlet valve (7) and the outlet valve (28) of the transparent box. Water enters the inlet tank (40) through the inlet hose (6) from the second inlet tank (2). Water seeps into the sample through the mesh partition (13) of the inlet tank. Observe the inlet flow meter (42). If the flow meter reading at a certain moment is no different from the flow meter reading before the preset time, adjust the height of the second inlet tank (2) by 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 outlet tank (41). When water first flows into the outlet tank (41), the inlet head is defined as H1 and the outlet head is defined as H2. Water enters the outlet tank (29) through the outlet hose (27) of the transparent box. When the water level reaches the outlet (32), it flows out to the circulating water supply tank (33) to complete the recycling of the test water. The water volume of the outlet is measured and recorded by the outlet flow meter (31).

[0013] S9: Read the outflow meter data Q1 and Q2 at times t1 and t2, where t2>t1. The flow meter reading is the total flow from the start of the experiment 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] In the formula: K is the permeability coefficient of the sample; t1 and t2 are the times when the flow meter data is read, Q1 is the flow meter data at time t1; Q2 is the flow meter data at time t2; L is the distance between the mesh partition (13) of the inlet tank and the mesh partition (15) of the outlet tank; A is the area of ​​the outlet cross section; H1 is the inlet water head; H2 is the outlet water 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 gravitational acceleration.

[0016] S10: Define the water level change as Δh. Initially, Δh = (H1 - H2) / 2. Measure the maximum impermeable head difference of the sample using the bisection method. As the influent head H1 decreases by Δh / 2, the new head change value Δh is determined. 新 =Δh / 2, after the inlet water head H1 drops to the set value, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the inlet flow meter (42) changes within the preset time, proceed to step S12;

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

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

[0019] S13: After steps S10-S12, in order to make the maximum impermeable head difference accurate to centimeters, when Δh≦0.01m, if the reading of the 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 inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within a preset time, the difference between H1 and H2 at this time is the maximum impermeable head difference of the sample.

[0020] S14: Adjust the height of the second water inlet tank (2) by using the hydraulic rod (5) and the first laser rangefinder (37), set H1 to the height of H2 plus the maximum impermeable head difference of the sample, and continue the test for N days. Observe whether water can penetrate through the sample into the outlet tank (41). The flow rate is continuously recorded by the outlet flow meter (31). Every M hours, perform step S9 to calculate the permeability coefficient and permeability of the sample, observe whether the permeability coefficient and permeability change, and analyze the effect of constant water pressure and water soaking on the sample's impermeability. Repeat steps S10-S13 after N days to find the new maximum impermeable head difference of the sample under constant water pressure and water soaking.

[0021] S15: Prepare the sample again, and perform steps S1-S13, setting H1 to the height of H2 plus the maximum impermeability head difference of the sample.

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

[0024] S18: The experiment consists of one cycle of steps S16 and S17, repeated multiple times, and lasts for several hours. Then, proceed to step 9 to calculate the permeability coefficient and permeability of the sample and observe their changes. Repeat steps S10-S13 to find the new maximum impermeable head difference of the sample under the action of short-term water pressure changes and analyze the effect of short-term water pressure changes on the sample's impermeability.

[0025] S19: Re-prepare the sample, and perform steps S1-S13, setting H1 to the height of H2 plus the maximum impermeability head difference of the sample.

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

[0028] S22: The experiment consists of one cycle of steps S20 and S21, repeated multiple times, lasting for several days. 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 impermeability head difference of the sample under long-term changes in water pressure and water immersion. The effects of long-term changes in water pressure and water immersion on the sample's impermeability are analyzed.

[0029] As a further improvement of the present invention, in step S1, the test device includes a circulating water system, an inlet water system, a test chamber system, and an outlet water system. The four systems are set on a steel frame support (25). Two casters (26) are installed at the bottom of the steel frame support (25). The circulating water system is connected to the water pump (36) through a pre-filter (34) and a circulating water supply hose (35). The water pump (36) is connected to the first inlet water tank (1) of the inlet water system. The water level controller (39) is located on the side wall of the first inlet water tank (1). The first inlet water tank (1) is connected to the water supply hose (3). 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), and 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 trough (40) of the transparent box (14) of the test box system through the water inlet hose (6). The water inlet hose (6) is equipped with the water inlet valve (7) and the water inlet flow meter (42). The top of the water inlet trough (40) has a water inlet trough sealing strip (12). The water inlet trough (40) is connected to the seepage through the water inlet mesh partition (13). The trough (43) is separated, and 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 pivot (24). The transparent box base hydraulic rod (22) is connected to the slide rail (23). The top of the seepage trough (43) is provided with a cover plate (9). The cover plate (9) has a cover plate handle (8), a cover plate sealing water inlet (10) and a cover plate sealing film (11). The front and rear side walls of the seepage trough (43) have seepage trough side water inlets (18) and sealing films. The bottom plate of the seepage trough (43) has a seepage trough bottom plate. The sealing membrane filling port (21) and the sealing membrane, the transparent box (14) are separated from the water outlet tank (41) by the water outlet mesh partition (15), the top of the water outlet tank (41) has a water outlet tank sealing strip (16), the water outlet tank (41) is connected to the water outlet tank (29) of the water outlet system through the transparent box water outlet hose (27), the transparent box water outlet hose (27) is equipped with a transparent box water outlet valve (28), the bottom of the water outlet tank (29) is connected to the water outlet tank hydraulic rod (30), the water outlet (32) is connected to the circulating water supply tank, and the water outlet (32) is equipped with a water flow meter (31).

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

[0031] As a further improvement of the present invention, in 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, the binary search method mentioned in steps S10-S13 involves dividing the ordered array into two halves, comparing the middle element with the target value each time, and deciding whether to continue searching in the first half or the second half based on the comparison result, until the target value is found or it is determined that it does not exist.

[0033] In step S2, the sealing membrane is elastic. After water is filled into the sealing membrane, the sealing membrane can deform so that its outer surface always adheres to the sample surface, preventing water from flowing along the gaps between the sample and the side wall, bottom plate, and cover plate of the permeation tank (43).

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

[0035] In step S3, the hydraulic rods (5, 30) and laser rangefinders (37, 38) can accurately, flexibly, and effortlessly set the heights of the second inlet tank (2) and outlet tank (29), ensuring that the head difference can be maintained at the set value. By setting the tilt angle of the transparent box base using the hydraulic rod (22) and slide rail (23), different tilt angles of the sample and different infiltration angles of water can be simulated, increasing the applicable conditions for the experiment.

[0036] In step S4, the inlet tank sealing strip (12), the cover plate (9), and the outlet tank sealing strip (16) are all easy to install and remove, so as to be suitable for two different test conditions: non-pressure and pressure. The cover plate sealing film (11) is elastic. After water is filled into the sealing film, the sealing film can deform. By evenly placing weights on the cover plate (9), the cover plate (9) can be evenly stressed, so that the outer surface of the sealing film always adheres to the sample surface.

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

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

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

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

[0041] In steps S10-S13, the binary search method mentioned divides the ordered array into two halves. Each time, the middle element is compared with the target value, and the search continues in the first or second half based on the comparison result until the target value is found or it is determined that it does not exist. The time complexity of this method is O(log n). This invention uses a variant of the binary search method. This method can reduce the time required to find the maximum impermeability head difference, reduce the impact of water pressure and water soaking on the sample's impermeability during the process, and prevent the original maximum impermeability head difference of the sample from changing too much.

[0042] In steps S15-S18, the inlet water head is increased by 0.1m every 10 minutes for 120 minutes, and then decreased by 0.1m every 10 minutes for 120 minutes, repeated 3 times. This is used to analyze the effect of short-term water pressure changes on the sample's impermeability. The interval time and water head increase / decrease can also be adjusted according to the actual situation of the experiment.

[0043] In steps S19-S22, the inlet water head is increased by 0.1m every hour for 12 hours, and then decreased by 0.1m 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 water immersion on the sample's impermeability are analyzed. The interval time and water head increase / decrease can also be adjusted according to the actual conditions of the experiment.

[0044] This invention studies the effects of changes in water head, media, and the duration of immersion of coal and rock in water on their impermeability, permeability coefficient, and permeability, providing technical support for the scientific and safe construction and mining of coal seams.

[0045] This invention can monitor, record, and acquire the permeability coefficient in real time; it can find the maximum impermeability head difference of a sample in a short time, with high time efficiency; it has many adjustable parameters, and can analyze the influence of single or combined factors of three factors—long-term or short-term, changing or constant water pressure, and water immersion effect—on the sample's impermeability, making it widely applicable; the test water can be recycled, and the water pump can be controlled to start and stop, saving resources; the entire testing method has strong logical flow and flexibility.

[0046] The beneficial effects of this invention are:

[0047] 1. In this invention, “S1: Coal and rock with a volume larger than the length and width of the seepage tank (43) of the test device are cut according to the length and width of the seepage tank (43) or small coal blocks and coal powder are uniformly mixed to prepare test samples. According to the minimum diameter of the sample particles, the mesh aperture of the inlet mesh partition (13) and the outlet mesh partition (15) is selected. The mesh partitions (13, 15) are inserted into the transparent box (14) and the sample is placed in the seepage tank (43). Compared with the existing technology method of using permeable stone to separate the sample and the inlet and outlet parts, this invention modularizes the mesh partition, which can more flexibly select the mesh with a suitable aperture. While separating the sample and preventing the sample particles from flowing into the inlet, outlet and circulation system, it better ensures the flowability of water and reduces the impact on the measurement of the sample permeability coefficient and permeability.

[0048] 2. In this invention, “S2: Water is filled into the sealing membrane water inlets (18, 21) on the front and rear side walls and the bottom plate of the seepage tank (43) so that the surface of the sealing membrane always adheres to the sample surface, preventing water from flowing from the gap between the sample and the transparent box (14). Compared with the existing technology, the design of the sealing membrane can flexibly adjust the water pressure in the sealing membrane during the test, ensuring that its outer surface always adheres to the sample surface, ensuring that water does not flow along the gap between the sample and the side wall and bottom plate of the seepage tank, while not excessively squeezing the sample, thus reducing test error.

[0049] 3. In this invention, test water is added to the water supply tank (33) of the circulating water system, the inlet valve (7) and the outlet valve (28) of the transparent box are closed, and the height of the outlet tank (29) is adjusted by the hydraulic rod (30) and the second laser rangefinder (38) so that the height of the outlet (32) and the sample at the position of the mesh partition (15) of the water outlet tank are at the same level, which is set as the water level of the outlet tank (29), that is, the water head. The height of the second inlet tank (2) is adjusted by the hydraulic rod (5) and the first laser rangefinder (37) so that the float valve (4) The water level of the float is 0.1m higher than the water level of the outlet tank (29), which is set as the water level of the second inlet tank (2), i.e., the water head. The tilt 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 fixed horizontal flow, the combination of hydraulic rod and slide rail can flexibly adjust the tilt 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. In this invention, “S4: If the water head is higher than the top height of the water inlet tank, a water inlet tank sealing strip (12) needs to be installed on the top of the water inlet tank (40), and a cover plate (9) needs to be installed on the top of the seepage tank (43). Water is filled 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 sample surface, and weights are evenly placed on the cover plate to ensure that the cover plate (9) is always in contact with the sample. If it is a pressure test condition, a water outlet tank sealing strip (16) needs to be installed on the top of the water outlet tank (41).” The detachable sealing strip can flexibly change the non-pressure and pressure test conditions and expand the scope of application of the test method.

[0051] 5. In this invention, “S7: Open the inlet valve (7) and the outlet valve (28) of the transparent box. Water enters the inlet tank (40) through the inlet hose (6) from the second inlet tank (2). The water seeps into the sample through the mesh partition (13) of the inlet tank. Observe the inlet flow meter (42). If the flow meter reading at a certain moment is no different from the flow meter reading 1 minute ago, adjust the height of the second inlet tank (2) by 0.1m through the hydraulic rod (5) and the first laser rangefinder (37). Reading the inlet flow meter data allows observation of the water seeping into the sample at the inlet end, reducing the waiting time caused by the inability or difficulty of water to seep into the sample due to unreasonable head difference settings, and improving the time efficiency of the test.

[0052] 6. In this invention, "S10: The water level change value is defined as Δh, initially Δh = (H1 - H2) / 2. The maximum impermeable head difference of the sample is measured by the bisection method. The influent head H1 decreases by Δh / 2, and the new head change value Δh..." 新=Δh / 2, after the inlet water head H1 drops to the set value, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the inlet flow meter (42) changes within 1 minute, proceed to step S12; S11: The inlet water head H1 increases by Δh 新 / 2, Δh is assigned the value Δh 新 / 2, new head change value Δh 新 =Δh / 2, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, repeat step S11; if the reading of the inlet flow meter (42) changes within 1 minute, proceed to step S12; S12: the inlet head H1 decreases by Δh 新 / 2, Δh is assigned the value Δh 新 / 2, new head change value Δh 新 =Δh / 2, if the reading of the influent flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the influent flow meter (42) changes within 1 minute, repeat step S12; S13: After steps S10-S12, in order to accurately measure the maximum impermeable head difference to the centimeter, when Δh≦0.01m, if the reading of the influent flow meter (42) remains unchanged 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 sample value. The maximum impermeable head difference of the sample is determined by the change in the reading of the inlet flow meter (42) within one minute, indicating that water has infiltrated into the sample within one minute. The difference between H1 and H2 minus 0.01m is the maximum impermeable head difference of the sample. S14: Adjust the height of the second inlet tank (2) using the hydraulic rod (5) and the first laser rangefinder (37) to set H1 to the height of H2 plus the maximum impermeable head difference of the sample. The test continues for 7 days to observe whether the water can penetrate the sample. The sample permeates into the outlet tank (41), and the flow rate is continuously recorded by the outlet flow meter (31). Every hour, step S9 is performed to calculate the permeability coefficient and permeability of the sample. The permeability coefficient and permeability are observed to see if there are any changes. The influence of constant water pressure and water immersion on the sample's impermeability is analyzed. Steps S10-S13 are repeated after 7 days to find the new maximum impermeable head difference of the sample under constant water pressure and water immersion. Compared with the existing methods, the bisection method can find the maximum impermeable head difference of the sample with higher time efficiency, reduce the influence of water pressure and water immersion on the sample's impermeability during the test, and prevent the original maximum impermeable head difference of the sample from changing too much. At the same time, the same sample is used to continue the test, and the permeability coefficient, permeability, and the new maximum impermeable head difference of the sample under constant water pressure and water immersion are measured to analyze the influence of constant water pressure and immersion on the sample's impermeability.

[0053] 7. In this invention, S18 and S22 also utilize the dichotomy method, which can improve the time efficiency of finding the original maximum impermeable head difference of the sample, the new maximum impermeable head difference of the sample under the action of short-term changing water pressure, and the new maximum impermeable head difference of the sample under the action of long-term changing water pressure and water immersion. Attached Figure Description

[0054] Figure 1 This is a front view of the test apparatus in an embodiment of the present invention;

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

[0056] Figure label:

[0057] 1-First inlet tank, 2-Second inlet tank, 3-Water supply hose, 4-Float valve, 5-Hydraulic rod, 6-Inlet hose, 7-Inlet valve, 8-Cover handle, 9-Cover, 10-Cover sealing membrane filling port, 11-Cover sealing membrane, 12-Inlet trough sealing strip, 13-Inlet trough mesh partition, 14-Transparent box body, 15-Outlet trough mesh partition, 16-Outlet trough sealing strip, 17-Outlet trough handle, 18-Side sealing membrane filling port of seepage trough, 19-Inlet handle, 20-Transparent box body base, 21-Seepage trough bottom plate sealing membrane filling port, 22-Transparent 23-Hydraulic rod for the base of the transparent enclosure; 24-Slide rail; 25-Rotating shaft for the base of the transparent enclosure; 26-Steel frame support; 27-Wheel caster; 28-Outlet hose for the transparent enclosure; 29-Outlet tank; 30-Hydraulic rod for the outlet tank; 31-Outlet flow meter; 32-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-Inlet tank; 41-Outlet tank; 42-Inlet flow meter; 43-Seepage tank. Detailed Implementation

[0058] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0059] Example 1:

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

[0061] S1: Cut coal and rock with a volume larger than the length and width of the seepage trough (43) of the test device according to the length and width of the seepage trough (43) or prepare test samples by uniformly mixing small coal blocks and coal powder. According to the minimum diameter of the sample particles, select the mesh aperture of the inlet mesh partition (13) and the outlet mesh partition (15). Insert the mesh partition (13, 15) into the transparent box (14) and put the sample into the seepage trough (43).

[0062] S2: Fill the sealing membrane water inlets (18, 21) on the front and rear side walls and bottom plate of the seepage tank (43) with water so that the surface of the sealing membrane always adheres to the sample surface and prevents water from flowing from 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 inlet valve (7) and the outlet valve (28) of the transparent box, adjust the height of the outlet tank (29) by means of the hydraulic rod (30) and the second laser rangefinder (38) so that the height of the outlet (32) and the sample at the position of the mesh partition (15) of the water outlet tank are at the same level, and set the water level of the outlet tank (29) as the water head. Adjust the height of the second inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37) so that the level of the float of the float valve (4) is 0.1m higher than the water level of the outlet tank (29), and set the water level of the second inlet tank (2) as the water head. Set the tilt angle of the transparent box base by means of the hydraulic rod (22) and the slide rail (23).

[0064] S4: If the water head is higher than the top of the water tank, a water tank sealing strip (12) needs to be installed on the top of the water tank (40), and a cover plate (9) needs to be installed on the top of the seepage tank (43). Water is filled through the water filling port (10) of the cover plate sealing film. Similarly, the surface of the sealing film is attached to the sample surface, and weights are evenly placed on the cover plate to ensure that the cover plate (9) is always attached to the sample. If it is a pressure test condition, a water tank sealing strip (16) needs to be installed on the top of the water tank (41).

[0065] S5: Start the water pump (36) to send water from the circulating water supply tank (33) through the pre-filter (34) to filter out particulate matter in the water and then send it to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is equipped 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 run, and stops running after filling the first water inlet tank (1). The process of the water pump (36) supplying water to the first water inlet tank (1) is repeated.

[0066] S6: Water from the first water tank (1) enters the second water 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 inlet valve (7) and the outlet valve (28) of the transparent box. Water enters the inlet tank (40) through the inlet hose (6) from the second inlet tank (2). Water seeps into the sample through the mesh partition (13) of the inlet tank. Observe the inlet flow meter (42). If the flow meter reading at a certain moment is no different from the flow meter reading 1 minute ago, adjust the height of the second inlet tank (2) by 0.1m using the hydraulic rod (5) and the first laser rangefinder (37).

[0068] S8: Repeat the test process of S4-S7 until water enters the outlet tank (41). When water first flows into the outlet tank (41), the inlet head is defined as H1 and the outlet head is defined as H2. Water enters the outlet tank (29) through the outlet hose (27) of the transparent box. When the water level reaches the outlet (32), it flows out to the circulating water supply tank (33) to complete the recycling of the test water. The water volume of the outlet is measured and recorded by the outlet flow meter (31).

[0069] S9: Read the flow meter data Q1 and Q2 at times 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] In the formula: K is the permeability coefficient of the sample, in m / s; t1 and t2 are the times when the flow meter data is read, and Q1 is the flow meter data at time t1, in m³ / s. 3 Q2 represents the flow meter data at time t2, in meters per second (m³). 3 L is the distance between the inlet screen partition (13) and the outlet screen partition (15), in meters; A is the area of ​​the outlet cross-section, in square meters. 2 H1 is the inlet water head, in meters; H2 is the outlet water head, in meters; k is the permeability of the sample, in meters. 2 η is the dynamic viscosity coefficient of water, measured in Pa·s; ρ is the density of the sample, measured in kg / m³. 3 g is the acceleration due to gravity, in m / s². 2 .

[0072] S10: Define the water level change as Δh. Initially, Δh = (H1 - H2) / 2. Measure the maximum impermeable head difference of the sample using the bisection method. As the influent head H1 decreases by Δh / 2, the new head change value Δh is determined. 新 =Δh / 2, after the inlet water head H1 drops to the set value, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the inlet flow meter (42) changes within 1 minute, proceed to step S12.

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

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

[0075] S13: After steps S10-S12, in order to make the maximum impermeable head difference accurate to centimeters, when Δh≦0.01m, if the reading of the inlet flow meter (42) remains unchanged 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 inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within 1 minute, the difference between H1 and H2 at this time minus 0.01m is the maximum impermeable head difference of the sample.

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

[0077] S15: Every 10 minutes, adjust the height of the second water tank (2) by 0.1m using the hydraulic rod (5) and the first laser rangefinder (37) for 120 minutes;

[0078] S16: Every 10 minutes, adjust the height of the second water inlet tank (2) by 0.1m using the hydraulic rod (5) and the first laser rangefinder (37) for 120 minutes;

[0079] S17: The experiment consists of one cycle of steps S15 and S16, with 3 cycles in total. The experiment lasts for 12 hours. 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 to analyze the effect of short-term water pressure changes on the sample's impermeability.

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

[0081] Example 2:

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

[0083] S1: Cut coal and rock with a volume larger than the length and width of the seepage trough (43) of the test device according to the length and width of the seepage trough (43) or prepare test samples by uniformly mixing small coal blocks and coal powder. According to the minimum diameter of the sample particles, select the mesh aperture of the inlet mesh partition (13) and the outlet mesh partition (15). Insert the mesh partition (13, 15) into the transparent box (14) and put the sample into the seepage trough (43).

[0084] S2: Fill the sealing membrane water inlets (18, 21) on the front and rear side walls and bottom plate of the seepage tank (43) with water so that the surface of the sealing membrane always adheres to the sample surface and prevents water from flowing from 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 inlet valve (7) and the outlet valve (28) of the transparent box, adjust the height of the outlet tank (29) by means of the hydraulic rod (30) and the second laser rangefinder (38) so that the height of the outlet (32) and the sample at the position of the mesh partition (15) of the water outlet tank are at the same level, and set the water level of the outlet tank (29) as the water head. Adjust the height of the second inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37) so that the level of the float of the float valve (4) is 0.1m higher than the water level of the outlet tank (29), and set the water level of the second inlet tank (2) as the water head. Set the tilt angle of the transparent box base by means of the hydraulic rod (22) and the slide rail (23).

[0086] S4: If the water head is higher than the top of the water tank, a water tank sealing strip (12) needs to be installed on the top of the water tank (40), and a cover plate (9) needs to be installed on the top of the seepage tank (43). Water is filled through the water filling port (10) of the cover plate sealing film. Similarly, the surface of the sealing film is attached to the sample surface, and weights are evenly placed on the cover plate to ensure that the cover plate (9) is always attached to the sample. If it is a pressure test condition, a water tank sealing strip (16) needs to be installed on the top of the water tank (41).

[0087] S5: Start the water pump (36) to send water from the circulating water supply tank (33) through the pre-filter (34) to filter out particulate matter in the water and then send it to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is equipped 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 run, and stops running after filling the first water inlet tank (1). The process of the water pump (36) supplying water to the first water inlet tank (1) is repeated.

[0088] S6: Water from the first water tank (1) enters the second water 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 inlet valve (7) and the outlet valve (28) of the transparent box. Water enters the inlet tank (40) through the inlet hose (6) from the second inlet tank (2). Water seeps into the sample through the mesh partition (13) of the inlet tank. Observe the inlet flow meter (42). If the flow meter reading at a certain moment is no different from the flow meter reading 1 minute ago, adjust the height of the second inlet tank (2) by 0.1m using the hydraulic rod (5) and the first laser rangefinder (37).

[0090] S8: Repeat the test process of S4-S7 until water enters the outlet tank (41). When water first flows into the outlet tank (41), the inlet head is defined as H1 and the outlet head is defined as H2. Water enters the outlet tank (29) through the outlet hose (27) of the transparent box. When the water level reaches the outlet (32), it flows out to the circulating water supply tank (33) to complete the recycling of the test water. The water volume of the outlet is measured and recorded by the outlet flow meter (31).

[0091] S9: Read the flow meter data Q1 and Q2 at times 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] In the formula: K is the permeability coefficient of the sample, in m / s; t1 and t2 are the times when the flow meter data is read, and Q1 is the flow meter data at time t1, in m³ / s. 3 Q2 represents the flow meter data at time t2, in meters per second (m³). 3 L is the distance between the inlet screen partition (13) and the outlet screen partition (15), in meters; A is the area of ​​the outlet cross-section, in square meters. 2 H1 is the inlet water head, in meters; H2 is the outlet water head, in meters; k is the permeability of the sample, in meters. 2 η is the dynamic viscosity coefficient of water, measured in Pa·s; ρ is the density of the sample, measured in kg / m³. 3 g is the acceleration due to gravity, in m / s². 2 .

[0094] S10: Define the water level change as Δh. Initially, Δh = (H1 - H2) / 2. Measure the maximum impermeable head difference of the sample using the bisection method. As the influent head H1 decreases by Δh / 2, the new head change value Δh is determined. 新 =Δh / 2, after the inlet water head H1 drops to the set value, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the inlet flow meter (42) changes within 1 minute, proceed to step S12.

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

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

[0097] S13: After steps S10-S12, in order to make the maximum impermeable head difference accurate to centimeters, when Δh≦0.01m, if the reading of the inlet flow meter (42) remains unchanged 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 inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within 1 minute, the difference between H1 and H2 at this time minus 0.01m is the maximum impermeable head difference of the sample.

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

[0099] S15: Every hour, adjust the height of the second water tank (2) by 0.1m using the hydraulic rod (5) and the first laser rangefinder (37) for 12 hours;

[0100] S16: Every hour, adjust the height of the second water inlet tank (2) by 0.1m using the hydraulic rod (5) and the first laser rangefinder (37), for 12 hours;

[0101] S17: The experiment consists of one cycle of steps S56 and S16, with 7 cycles in total. The experiment lasts for 7 days. Then, proceed to step 9 to calculate the permeability coefficient and permeability of the sample and observe their changes. Repeat steps S10-S13 to find the new maximum impermeability head difference of the sample under long-term changes in water pressure and water immersion. Analyze the effects of long-term changes in water pressure and water immersion on the sample's impermeability.

[0102] This embodiment describes an implementation method for analyzing the effects of long-term changes in water pressure and water softening on the permeability of a sample. The method involves increasing and decreasing the head difference over a relatively long period, repeating this cycle, calculating the sample's permeability coefficient and permeability, analyzing the changes in the sample's original maximum impermeable head difference and the new maximum impermeable head difference under long-term changes in water pressure and water immersion, and exploring the effects of long-term changes in water pressure and water immersion on the sample's permeability.

[0103] Example 3:

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

[0105] S1: Cut coal and rock with a volume larger than the length and width of the seepage trough (43) of the test device according to the length and width of the seepage trough (43) or prepare test samples by uniformly mixing small coal blocks and coal powder. According to the minimum diameter of the sample particles, select the mesh aperture of the inlet mesh partition (13) and the outlet mesh partition (15). Insert the mesh partition (13, 15) into the transparent box (14) and put the sample into the seepage trough (43).

[0106] S2: Fill the sealing membrane water inlets (18, 21) on the front and rear side walls and bottom plate of the seepage tank (43) with water so that the surface of the sealing membrane always adheres to the sample surface and prevents water from flowing from 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 inlet valve (7) and the outlet valve (28) of the transparent box, adjust the height of the outlet tank (29) by means of the hydraulic rod (30) and the second laser rangefinder (38) so that the height of the outlet (32) and the sample at the position of the mesh partition (15) of the water outlet tank are at the same level, and set the water level of the outlet tank (29) as the water head. Adjust the height of the second inlet tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37) so that the level of the float of the float valve (4) is 0.1m higher than the water level of the outlet tank (29), and set the water level of the second inlet tank (2) as the water head. Set the tilt angle of the transparent box base by means of the hydraulic rod (22) and the slide rail (23).

[0108] S4: If the water head is higher than the top height of the water tank, a water tank sealing strip (12) needs to be installed on the top of the water tank (40), and a cover plate (9) needs to be installed on the top of the seepage tank (43). Water is filled through the water filling port (10) of the cover plate sealing film. Similarly, the surface of the sealing film is attached to the sample surface, and weights are evenly placed on the cover plate to ensure that the cover plate (9) is always attached to the sample.

[0109] S5: Start the water pump (36) to send water from the circulating water supply tank (33) through the pre-filter (34) to filter out particulate matter in the water and then send it to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is equipped 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 run, and stops running after filling the first water inlet tank (1). The process of the water pump (36) supplying water to the first water inlet tank (1) is repeated.

[0110] S6: Water from the first water tank (1) enters the second water 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 inlet valve (7) and the outlet valve (28) of the transparent box. Water enters the inlet tank (40) through the inlet hose (6) from the second inlet tank (2). Water seeps into the sample through the mesh partition (13) of the inlet tank. Observe the inlet flow meter (42). If the flow meter reading at a certain moment is no different from the flow meter reading 1 minute ago, adjust the height of the second inlet tank (2) by 0.1m using the hydraulic rod (5) and the first laser rangefinder (37).

[0112] S8: Repeat the test process of S4-S7 until water enters the outlet tank (41). When water first flows into the outlet tank (41), the inlet head is defined as H1 and the outlet head is defined as H2. Water enters the outlet tank (29) through the outlet hose (27) of the transparent box. When the water level reaches the outlet (32), it flows out to the circulating water supply tank (33) to complete the recycling of the test water. The water volume of the outlet is measured and recorded by the outlet flow meter (31).

[0113] S9: Read the flow meter data Q1 and Q2 at times 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]

[0116] In the formula: K is the permeability coefficient of the sample, in m / s; t1 and t2 are the times when the flow meter data is read, and Q1 is the flow meter data at time t1, in m³ / s. 3 Q2 represents the flow meter data at time t2, in meters per second (m³). 3 L is the distance between the inlet screen partition (13) and the outlet screen partition (15), in meters; A is the area of ​​the outlet cross-section, in square meters. 2 H1 is the inlet water head, in meters; H2 is the outlet water head, in meters; k is the permeability of the sample, in meters. 2 η is the dynamic viscosity coefficient of water, measured in Pa·s; ρ is the density of the sample, measured in kg / m³. 3 g is the acceleration due to gravity, in m / s².2 .

[0117] S10: Define the water level change as Δh. Initially, Δh = (H1 - H2) / 2. Measure the maximum impermeable head difference of the sample using the bisection method. As the influent head H1 decreases by Δh / 2, the new head change value Δh is determined. 新 =Δh / 2, after the inlet water head H1 drops to the set value, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the inlet flow meter (42) changes within 1 minute, proceed to step S12.

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

[0119] S12: Inlet water head H1 decreases by Δh 新 / 2, Δh is assigned the value Δh 新 / 2, new head change value Δh 新 =Δh / 2, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the inlet flow meter (42) changes within 1 minute, repeat step S12.

[0120] S13: After steps S10-S12, in order to make the maximum impermeable head difference accurate to centimeters, when Δh≦0.01m, if the reading of the inlet flow meter (42) remains unchanged 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 inlet flow meter (42) changes within 1 minute, that is, water infiltrates into the sample within 1 minute, the difference between H1 and H2 at this time minus 0.01m is the maximum impermeable head difference of the sample.

[0121] S14: Adjust the height of the second water inlet tank (2) using the hydraulic rod (5) and the first laser rangefinder (37), set H1 to the height of H2 plus the maximum impermeable head difference of the sample, and continue the test for 7 days. Observe whether water can penetrate through the sample into the outlet tank (41). The flow rate is continuously recorded by the outlet flow meter (31). Perform step S9 every 1 hour to calculate the permeability coefficient and permeability of the sample, observe whether the permeability coefficient and permeability change, and analyze the effect of constant water pressure and water soaking on the sample's impermeability. Repeat steps S10-S13 after 7 days to find the new maximum impermeable head difference of the sample under constant water pressure and water soaking.

[0122] This embodiment describes an implementation method for analyzing the effects of constant water pressure and water immersion on the permeability of a sample. The water head difference is kept constant over a relatively long time period. The sample's permeability coefficient and permeability are calculated. The changes in the sample's original maximum impermeable water head difference, constant water pressure, and new maximum impermeable water head difference under water immersion are analyzed to explore the influence of constant water pressure and water immersion on the sample's permeability.

[0123] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A test method for permeability resistance of low-permeability coal and rock media, characterized in that: Includes the following steps: S1: Cut coal and rock with a volume larger than the length and width of the seepage trough (43) of the test device according to the length and width of the seepage trough (43) or prepare test samples by uniformly mixing small coal blocks and coal powder. According to the minimum diameter of the sample particles, select the mesh aperture of the inlet mesh partition (13) and the outlet mesh partition (15). Insert the inlet mesh partition (13) and the outlet mesh partition (15) into the transparent box (14) and put the sample into the seepage trough (43). S2: Fill the sealing membrane with water at the side sealing membrane water inlet (18) and the bottom sealing membrane water inlet (21) of the seepage tank with water so that the surface of the sealing membrane always adheres to the sample surface. S3: Add test water to the water supply tank (33) of the circulating water system, close the inlet valve (7) and outlet valve (28) of the transparent box (14), adjust the height of the outlet tank (29) by the hydraulic rod (30) of the outlet tank and the second laser rangefinder (38) so that the height of the outlet (32) and the sample at the position of the mesh partition (15) of the outlet tank are at the same level, and set the water level of the outlet tank (29) as the water head. Adjust the height of the second inlet tank (2) by the hydraulic rod (5) and the first laser rangefinder (37) so that the level of the float of the float valve (4) is higher than the water level of the outlet tank (29), and set the water level of the second inlet tank (2) as the water head. Set the tilt angle of the transparent box base by the hydraulic rod (22) of the transparent box base and the slide rail (23). S4: If the water head is higher than the top height of the water tank, a water tank sealing strip (12) needs to be installed on the top of the water tank (40), and a cover plate (9) needs to be installed on the top of the seepage tank (43). Water is filled through the water filling port (10) of the cover plate sealing film. Similarly, the surface of the sealing film is attached to the sample surface, and weights are evenly placed on the cover plate to ensure that the cover plate (9) is always attached to the sample. S5: Start the water pump (36) to send water from the circulating water supply tank (33) through the pre-filter (34) to filter out particulate matter in the water and then send it to the first water inlet tank (1) of the water inlet system. The first water inlet tank (1) is equipped 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 run, and stops running after filling the first water inlet tank (1). The process of the water pump (36) supplying water to the first water inlet tank (1) is repeated. S6: Water from the first water tank (1) enters the second water 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 inlet valve (7) and the outlet valve (28) of the transparent box. Water enters the inlet tank (40) through the inlet hose (6) from the second inlet tank (2). Water seeps into the sample through the mesh partition (13) of the inlet tank. Observe the inlet flow meter (42). If the flow meter reading at a certain moment is no different from the flow meter reading before the preset time, adjust the height of the second inlet tank (2) by 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 outlet tank (41). When water first flows into the outlet tank (41), the inlet head is defined as H1 and the outlet head is defined as H2. Water enters the outlet tank (29) through the outlet hose (27) of the transparent box. When the water level reaches the outlet (32), it flows out to the circulating water supply tank (33) to complete the recycling of the test water. The water volume of the outlet is measured and recorded by the outlet flow meter (31). S9: Read the outflow meter data Q1 and Q2 at times t1 and t2, where t2>t1. The flow meter reading is the total flow from the start of the experiment 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: In the formula: K is the permeability coefficient of the sample; t1 and t2 are the times when the flow meter data is read, Q1 is the flow meter data at time t1; Q2 is the flow meter data at time t2; L is the distance between the mesh partition (13) of the inlet tank and the mesh partition (15) of the outlet tank; A is the area of ​​the outlet cross section; H1 is the inlet water head; H2 is the outlet water 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 gravitational acceleration. S10: Define the water level change as Δh. Initially, Δh = (H1 - H2) / 2. Measure the maximum impermeable head difference of the sample using the bisection method. As the influent head H1 decreases by Δh / 2, the new head change value Δh is determined. 新 =Δh / 2, after the inlet water head H1 drops to the set value, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, proceed to step S11; if the reading of the inlet flow meter (42) changes within the preset time, proceed to step S12; S11: Inlet water head H1 increases by Δh 新 / 2, Δh is assigned the value Δh 新 / 2, new head change value Δh 新 =Δh / 2, if the reading of the inlet flow meter (42) remains unchanged for 1 minute, repeat step S11; if the reading of the inlet flow meter (42) changes within a preset time, proceed to step S12; S12: Inlet water head H1 decreases by Δh 新 / 2, Δh is assigned the value Δh 新 / 2, new head change value Δh 新 =Δh / 2, if the reading of the inlet flow meter (42) does not change within a continuous preset time, proceed to step S11; if the reading of the inlet flow meter (42) changes within a preset time, repeat step S12. S13: After steps S10-S12, in order to make the maximum impermeable head difference accurate to centimeters, when Δh≦0.01m, if the reading of the 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 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 minus 0.01m is the maximum impermeable head difference of the sample. S14: Adjust the height of the second water inlet tank (2) by using the hydraulic rod (5) and the first laser rangefinder (37), set H1 to the height of H2 plus the maximum impermeable head difference of the sample, and continue the test for N days. Observe whether water can penetrate through the sample into the outlet tank (41). The flow rate is continuously recorded by the outlet flow meter (31). Every M hours, perform step S9 to calculate the permeability coefficient and permeability of the sample, observe whether the permeability coefficient and permeability change, and analyze the effect of constant water pressure and water soaking on the sample's impermeability. Repeat steps S10-S13 after N days to find the new maximum impermeable head difference of the sample under constant water pressure and water soaking. S15: Re-prepare the sample, and perform steps S1-S13, setting H1 to the height of H2 plus the maximum impermeability head difference of the sample. S16: Every K minutes, adjust the height of the second water tank (2) by means of 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, adjust the height of the second water tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37) to reduce the preset height for a certain period of time; S18: The experiment consists of one cycle of steps S16 and S17, repeated multiple times, and lasts for several hours. Then, proceed to step 9 to calculate the permeability coefficient and permeability of the sample and observe their changes. Repeat steps S10-S13 to find the new maximum impermeable head difference of the sample under the action of short-term water pressure changes and analyze the effect of short-term water pressure changes on the sample's impermeability. S19: Re-prepare the sample, and perform steps S1-S13, setting H1 to the height of H2 plus the maximum impermeability head difference of the sample. S20: Every M hours, adjust the height of the second water tank (2) by means of 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, adjust the height of the second water tank (2) by means of the hydraulic rod (5) and the first laser rangefinder (37) to reduce the preset height for a certain period of time; S22: The experiment consists of one cycle of steps S20 and S21, repeated multiple times, lasting for several days. 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 impermeability head difference of the sample under long-term changes in water pressure and water immersion. The effects of long-term changes in water pressure and water immersion on the sample's impermeability are analyzed.

2. The test method for permeability resistance of low-permeability coal and rock media according to claim 1, characterized in that: In step S1, the test apparatus includes a circulating water system, an inlet water system, a test chamber system, and an outlet water system. The four systems are mounted on a steel frame support (25). Two casters (26) are installed at the bottom of the steel frame support (25). The circulating water system is connected to the water pump (36) through a pre-filter (34) and a circulating water supply hose (35). The water pump (36) is connected to the first inlet water tank (1) of the inlet water system. The water level controller (39) is located on the side wall of the first inlet water tank (1). The first inlet water tank (1) is connected to the second inlet water tank (2) through a water supply hose (3). 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 trough (40) of the transparent box (14) of the test box system through the water inlet hose (6), the water inlet hose (6) is equipped with the water inlet valve (7) and the water inlet flow meter (42), the top of the water inlet trough (40) has a water inlet trough sealing strip (12), the water inlet trough (40) is separated from the seepage trough (43) by the water inlet trough mesh partition (13). Open, 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 pivot (24), the transparent box base hydraulic rod (22) is connected to the slide rail (23), the top of the seepage tank (43) is provided with a cover plate (9), the cover plate (9) has a cover plate handle (8), a cover plate sealing water inlet (10) and a cover plate sealing film (11), the front and rear side walls of the seepage tank (43) have seepage tank side water inlets (18) and sealing films, the bottom plate of the seepage tank (43) has a seepage tank bottom plate sealing film. The water inlet (21) and sealing membrane, the transparent box (14) is separated from the water outlet (41) by the water outlet mesh partition (15), the top of the water outlet (41) has a water outlet sealing strip (16), the water outlet (41) is connected to the water outlet tank (29) of the water outlet system through the water outlet hose (27) of the transparent box, the water outlet hose (27) of the transparent box is equipped with a water outlet valve (28) of the transparent box, the bottom of the water outlet tank (29) is connected to the water outlet tank hydraulic rod (30), the water outlet (32) is connected to the circulating water supply tank, and the water outlet (32) is equipped with a water flow meter (31).

3. The test method for permeability resistance of low-permeability coal and rock media according to claim 1, characterized in that: In step S1, the mesh size of the mesh partition (13) of the inlet tank and the mesh partition (15) of the outlet tank can be replaced to ensure that the seepage tank (43), the inlet tank (40) and the outlet tank (41) are separated. Particles in the sample cannot enter the inlet tank (40) and the outlet tank (41), so that water can flow into the sample in a surface manner and flow out to the outlet tank (41).

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

5. The test method for permeability resistance of low-permeability coal and rock media according to claim 1, characterized in that: In steps S10-S13, the binary search method mentioned involves dividing the ordered array into two halves, comparing the middle element with the target value each time, and deciding whether to continue searching in the first or second half based on the comparison result, until the target value is found or it is determined that it does not exist.

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