Grouting test device and method for mining fractured rock mass with real-time synchronous permeability measurement

Abstract

This invention belongs to the field of grouting and filling technology for mining-induced fractured rock masses, and particularly relates to a testing device and method for real-time synchronous measurement of permeability in mining-induced fractured rock masses. The device includes a base placed inside a pressure-applying device, with a chamber for storing the sample; an air inlet located at the bottom of the chamber, with its exhaust end contacting the bottom of the sample and its inlet end located outside the base, for communicating with a gas source and providing high-pressure gas to the sample; an exhaust section located at the top of the chamber, with its inlet end contacting the top of the sample and located inside a piston, which slides within the chamber, with its exhaust end located outside the piston and its top mounted on the pressure-applying end of the pressure-applying device; a grouting section wrapped around the sidewall of the sample, with its bottom fixed to the base and its outlet end communicating with the chamber for injecting grout into the sample; and a displacement sensor for detecting the distance between the pressure-applying end of the pressure-applying device and the top of the chamber.

Description

Technical Field

[0001] This invention belongs to the field of grouting and filling technology for mining-induced fractured rock masses, and particularly relates to a test device and method for grouting mining-induced fractured rock masses with real-time synchronous measurement of permeability. Background Technology

[0002] During coal seam mining, mining activities cause the overlying strata to develop internal fractures, increasing porosity and permeability. When these fractures connect upwards to aquifers, water inrush accidents occur, resulting in casualties and property damage. Grouting technology can effectively fill these mining-induced fractures in the overlying strata, forming a water-resistant layer and preventing water inrush accidents. During this process, the permeability of the fractured rock mass continuously decreases under the filling effect of grout, a process that current methods cannot reproduce and measure in real time.

[0003] Therefore, there is an urgent need for a testing device and method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting to solve this problem. Summary of the Invention

[0004] The purpose of this invention is to provide a testing device and method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting, in order to solve the above-mentioned problems.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A real-time synchronous permeability measurement test device for grouting in mining-induced fractured rock masses includes:

[0007] A base is placed inside a pressure device, and the base has a chamber for storing the sample;

[0008] An air inlet is provided at the bottom of the chamber, the exhaust end of the air inlet is in contact with the bottom of the sample, the air inlet end of the air inlet is located outside the base, and the air inlet is used to communicate with a gas source and inject high-pressure gas into the chamber.

[0009] An exhaust section is disposed at the top of the chamber, with the air inlet end of the exhaust section contacting the top of the sample. The exhaust section is disposed inside the piston, which is slidably disposed within the chamber. The exhaust end of the exhaust section is located outside the piston, and the top of the piston is mounted on the pressure end of the pressure applying device.

[0010] The grouting section is wrapped around the side wall of the sample. The bottom of the grouting section is fixedly connected to the base. The liquid outlet of the grouting section is connected to the chamber and is used to inject grout into the chamber.

[0011] A displacement sensor is used to detect the height of the piston beyond the top of the chamber, thereby obtaining the sample height.

[0012] According to the above-mentioned real-time synchronous permeability measurement grouting test device for mining-induced fractured rock masses, the grouting unit includes:

[0013] An inner grouting cylinder is axially connected to the base at its bottom. The chamber is located inside the inner grouting cylinder, and a plurality of grouting holes for communicating with the chamber are evenly opened on the side wall of the inner grouting cylinder.

[0014] An outer cylinder is coaxially disposed outside the inner grouting cylinder. The bottom of the outer cylinder is fixedly connected to the top of the base, and the top of the outer cylinder is fixedly connected to the top of the inner grouting cylinder.

[0015] The inner wall of the outer cylinder and the outer wall of the inner grouting cylinder together form a grout temporary storage cavity, which is connected to the inlet end of a plurality of grouting holes;

[0016] The slurry storage chamber is connected to a slurry injection port, which is located on the outer cylinder.

[0017] According to the above-mentioned real-time synchronous permeability measurement grouting test device for mining-induced fractured rock masses, the air intake section includes:

[0018] A first honeycomb porous air chamber is disposed at the bottom of the chamber. The air inlet of the first honeycomb porous air chamber is connected to the exhaust end of the air inlet pipe. The air inlet pipe is embedded in the base. The air inlet of the air inlet pipe is disposed on the side wall of the base. The air inlet is used to connect to an air source.

[0019] A breathable fine gauze is laid between the exhaust end of the first honeycomb porous air cavity and the sample.

[0020] According to the above-mentioned real-time synchronous permeability measurement grouting test device for mining-induced fractured rock masses, the venting section includes:

[0021] The second honeycomb porous air chamber is slidably disposed in the chamber. The second honeycomb porous air chamber is fixed to the bottom of the piston. The air inlet end of the second honeycomb porous air chamber is in contact with and connected to the top of the sample. The air outlet end of the second honeycomb porous air chamber is connected to the air inlet end of an exhaust pipe. The exhaust pipe is embedded in the piston, and the air outlet of the exhaust pipe is opened on the side wall of the piston.

[0022] According to the above-mentioned real-time synchronous permeability measurement grouting test device for mining-induced fractured rock masses, the displacement sensor includes:

[0023] A linear variable differential transformer, wherein the fixed end of the linear variable differential transformer is fixed to the top of the inner grouting cylinder, and the movable end of the linear variable differential transformer is fixed to the pressure end of the pressure applying device.

[0024] According to the above-mentioned real-time synchronous permeability measurement grouting test device for mining-induced fractured rock masses, the pressure application device includes:

[0025] An axial displacement control device, wherein the base is placed inside the axial displacement control device, and the movable end of the axial displacement control device is fixedly connected to the top of the piston;

[0026] The movable end of the linear variable differential transformer is fixed to the movable end of the axial displacement control device.

[0027] A method for real-time synchronous permeability measurement grouting test in mining-induced fractured rock mass, based on the aforementioned real-time synchronous permeability measurement grouting test device, includes the following steps:

[0028] The sample is filled into the cavity, and the piston is controlled to contact the sample.

[0029] The pressure-applying end of the pressure-applying device drives the piston to press down on the sample, adjusting the porosity of the sample, and the displacement of the pressure-applying end of the pressure-applying device is detected by a displacement sensor;

[0030] After the target initial porosity is reached, the pressure is released to a stable value and the loading pressure at the pressure end of the pressure application device is kept constant. The air source and grouting mechanism are then turned on to inject grout into the chamber to start the seepage grouting test.

[0031] The grouting unit is controlled to inject grout into the grouting mechanism so that the grout is injected into the cavity;

[0032] Connect the gas source to the air inlet and control the gas source to inject high-pressure gas into the chamber through the air inlet;

[0033] Connect the gas collection device to the exhaust section;

[0034] The intake pressure data is obtained based on the intake volume of the intake section;

[0035] The exhaust pressure data is obtained based on the exhaust volume of the exhaust section;

[0036] Obtain the grouting pressure data of the grouting section;

[0037] The permeability and nonlinear seepage factor are obtained based on the air intake volume, air intake pressure data, exhaust volume, exhaust pressure data, and grouting pressure data.

[0038] Compared with the prior art, the present invention has the following advantages and technical effects:

[0039] In this invention, by providing axial stress to the sample, the initial porosity of the mining-induced fractured rock mass can be changed on the one hand, and it can also be used to provide axial stress on the other hand. Nitrogen gas can be used as the seepage fluid, which can reduce the mutual influence between the gas and the grout during the grouting process. The upward flow of gas can overcome the influence of the gas's own gravity. By monitoring parameters such as grout flow rate and gas flow rate during the grouting test, the permeability change law of the mining-induced fractured rock mass during the grouting process can be obtained after computer processing.

[0040] This invention, while ensuring that the grouting pressure and the gas pressure at the air inlet remain constant, can obtain the permeability variation characteristics of mining-induced fractured rock masses under different axial loading pressures by changing the axial load; while ensuring that the axial load and the grouting pressure remain constant, can obtain the permeability variation characteristics of mining-induced fractured rock masses under different pore pressures by changing the gas pressure at the air inlet; and while ensuring that the axial load and the gas pressure at the air inlet remain constant, can obtain the permeability variation characteristics of mining-induced fractured rock masses under different grouting pressures by changing the grouting pressure.

[0041] This invention can realize the permeability variation characteristics of mining fractured rock masses under different initial porosity, different continuous gradation conditions, and different slurry properties. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 It is a schematic diagram of the structure of the present invention;

[0044] Figure 2 This is a schematic diagram of the second honeycomb porous air cavity structure of the present invention;

[0045] Figure 3 This is a schematic diagram of the grouting section structure of the present invention;

[0046] Figure 4 This is a graph showing the change in permeability of the fractured rock mass over time during the grouting process of this invention.

[0047] Figure 5 This is a graph showing the variation of the nonlinear seepage factor of the mining-induced fractured rock mass over time during the grouting process of this invention.

[0048] Among them, 1. Axial displacement control device; 2. Piston; 3. Air outlet; 4. Linear variable differential transformer; 5. Bolt; 6. Second honeycomb porous air chamber; 7. Outer cylinder; 8. Inner grouting cylinder; 9. First honeycomb porous air chamber; 10. Grouting port; 11. Sealing ring; 12. Air inlet; 13. Base; 14. Breathable fine gauze. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Example 1:

[0052] Reference Figures 1 to 3 This embodiment discloses 1. a mining-induced fractured rock mass grouting test device for real-time synchronous measurement of permeability, comprising:

[0053] The base 13 is placed inside the pressure application device, and the base 13 has a chamber for storing the sample;

[0054] The air inlet is located at the bottom of the chamber. The exhaust end of the air inlet is in contact with the bottom of the sample. The air inlet is located outside the base 13. The air inlet is used to communicate with the gas source and inject high-pressure gas into the chamber.

[0055] The exhaust section is located at the top of the chamber. The air inlet of the exhaust section is in contact with the top of the sample. The exhaust section is located inside the piston 2. The piston 2 is slidably located inside the chamber. The exhaust end of the exhaust section is located outside the piston 2. The top of the piston 2 is mounted on the pressure end of the pressure application device.

[0056] The grouting section is wrapped around the side wall of the sample. The bottom of the grouting section is fixed to the base 13. The liquid outlet of the grouting section is connected to the chamber and is used to inject grout into the chamber.

[0057] A displacement sensor is used to detect the height of piston 2 above the top of the chamber, thus obtaining the sample height.

[0058] In use, the sample is filled into the chamber, and piston 2 is placed at the top of the chamber to contact the sample. Piston 2 is connected to the pressure end of the pressure application device. The grouting mechanism is connected to the grouting section, the gas source is connected to the air inlet, and the gas collection device is connected to the exhaust section. A data acquisition device and valves are installed. The pressure end of the pressure application device is driven to push piston 2 down to press down the sample to adjust the porosity of the sample. The loading pressure at the pressure end of the pressure application device is kept constant. The gas source and grouting mechanism are turned on to inject grout into the sample to start the seepage grouting test. The data acquired by the computer is analyzed and processed to obtain the permeability under the grouting conditions of the mining-induced fractured rock mass. In this invention, by providing axial stress to the sample, the initial porosity of the mining-induced fractured rock mass is changed on the one hand, and it can also be used to provide axial stress on the other hand. Nitrogen can be used as the seepage fluid, which can reduce the mutual influence between the gas and the grout during the grouting process. The upward flow of gas can overcome the influence of the gas's own gravity. By monitoring parameters such as grout flow rate and gas flow rate during the grouting test, the permeability change law during the grouting process of the mining-induced fractured rock mass can be obtained after computer processing.

[0059] This invention, while ensuring that the grouting pressure and the gas pressure at the air inlet remain constant, can obtain the permeability variation characteristics of mining-induced fractured rock masses under different axial loading pressures by changing the axial load; while ensuring that the axial load and the grouting pressure remain constant, can obtain the permeability variation characteristics of mining-induced fractured rock masses under different pore pressures by changing the gas pressure at the air inlet; and while ensuring that the axial load and the gas pressure at the air inlet remain constant, can obtain the permeability variation characteristics of mining-induced fractured rock masses under different grouting pressures by changing the grouting pressure.

[0060] This invention can realize the permeability variation characteristics of mining fractured rock masses under different initial porosity, different continuous gradation conditions, and different slurry properties.

[0061] As an optional implementation, the grouting unit includes:

[0062] The inner grouting cylinder 8 is axially connected to the base 13 at its bottom. The chamber is set inside the inner grouting cylinder 8. Several grouting holes for communicating with the chamber are evenly opened on the side wall of the inner grouting cylinder 8.

[0063] The outer cylinder 7 is coaxially arranged outside the inner grouting cylinder 8. The bottom of the outer cylinder 7 is fixedly connected to the top of the base 13, and the top of the outer cylinder 7 is fixedly connected to the top of the inner grouting cylinder 8.

[0064] The inner wall of the outer cylinder 7 and the outer wall of the inner grouting cylinder 8 together form a grout storage cavity, which is connected to the inlet end of several grouting holes.

[0065] The slurry storage chamber is connected to a grouting port 10, which is located on the outer cylinder 7.

[0066] Several grouting holes are evenly opened on the side wall of the inner grouting cylinder to ensure uniform injection of grout.

[0067] Sealing rings 11 are installed at the joint between the outer cylinder 7 and the inner grouting cylinder 8 to prevent grout leakage.

[0068] Grouting port 10 is connected to the grouting system, which includes a grouting tank, an air pump, a pressure stabilizing tank, a mud valve, an air inlet valve, a pressure reducing valve, an exhaust pipe, an exhaust valve, a grouting hose, a pressure gauge, a flow meter, and the grouting port. The air pump, pressure stabilizing tank, grouting tank, and grouting port 10 are connected sequentially. The grouting tank is equipped with a mixer. The pressure reducing valve is located at the outlet of the pressure stabilizing tank, and the air inlet valve is located at the inlet of the pressure stabilizing tank. An exhaust pipe with an exhaust valve is installed between the pressure reducing valve and the pressure stabilizing tank. The mud valve is located at the outlet of the grouting tank. A pressure gauge is installed at the inlet of the grouting tank, and a pressure gauge and a flow meter are sequentially installed at the grouting port. The grouting system is existing technology and will not be described in detail here.

[0069] As an optional implementation, the air intake includes:

[0070] The first honeycomb porous air chamber 9 is located at the bottom of the chamber. The air inlet of the first honeycomb porous air chamber 9 is connected to the exhaust end of the air inlet pipe. The air inlet pipe is embedded in the base 13. The air inlet 12 of the air inlet pipe is located on the side wall of the base 13. The air inlet 12 is used to connect to the air source.

[0071] A breathable fine gauze 14 is laid between the exhaust end of the first honeycomb porous air cavity 9 and the sample.

[0072] The first honeycomb porous air chamber 9 and the breathable fine gauze 14 are designed to ensure that the gas enters evenly.

[0073] As an optional implementation, the exhaust section includes:

[0074] The second honeycomb porous air chamber 6 is slidably disposed in the chamber and fixed to the bottom of the piston 2. The air inlet end of the second honeycomb porous air chamber 6 is in contact with and connected to the top of the sample. The air outlet end of the second honeycomb porous air chamber 6 is connected to the air inlet end of the exhaust pipe. The exhaust pipe is embedded in the piston 2 and the air outlet 3 of the exhaust pipe is opened on the side wall of the piston 2.

[0075] The second honeycomb porous air chamber 6 is designed to ensure uniform gas discharge.

[0076] Both the inlet 12 and the outlet 3 are connected to a gas permeation system, which consists of a high-pressure nitrogen cylinder, a pressure reducing valve, a flow meter, a pressure sensor, a gas collecting device, an inlet, an outlet, and a gas pipe. The inlet 12 is connected to the high-pressure nitrogen cylinder, and the outlet 3 is connected to the gas collecting device. A flow meter and a pressure reducing valve are installed near the inlet 12 to control the inlet flow and pressure. Pressure sensors are also installed at the inlet 12 and the outlet 3.

[0077] The first honeycomb porous air cavity 9 and the second honeycomb porous air cavity 6 have the same structure.

[0078] As an optional implementation, the displacement sensor includes:

[0079] The linear variable differential transformer 4 has its fixed end fixedly connected to the top of the inner grouting cylinder 8, and its movable end fixedly connected to the pressure end of the pressure applying device.

[0080] As an optional implementation, the pressure application device includes:

[0081] Axial displacement control device 1, base 13 is placed inside axial displacement control device 1, and the movable end of axial displacement control device 1 is fixedly connected to the top of piston 2.

[0082] The movable end of the linear variable differential transformer 4 is fixedly connected to the movable end of the axial displacement control device 1.

[0083] It also includes a data acquisition system, which consists of a data acquisition unit and a computer. One end of the data acquisition unit is electrically connected to the flow meter, pressure gauge, linear variable differential transformer 4, and axial displacement control device 1 of the entire test system, and the other end is connected to the computer.

[0084] A method for real-time synchronous permeability measurement grouting test in mining-induced fractured rock mass, based on the aforementioned real-time synchronous permeability measurement grouting test device, includes the following steps:

[0085] The sample is filled into the chamber, and the piston 2 is controlled to contact the sample.

[0086] The pressure-applying end of the driving pressure-applying device drives piston 2 to press down the sample, adjusts the porosity of the sample, and detects the displacement of the pressure-applying end of the pressure-applying device through a displacement sensor.

[0087] After the target initial porosity is reached, the pressure is released to a stable value and the loading pressure at the pressure end of the pressure application device is kept constant. The air source and grouting mechanism are then turned on to inject grout into the chamber to start the seepage grouting test.

[0088] The grouting unit is controlled to inject grout into the grouting mechanism so that the grout is injected into the cavity;

[0089] Connect the gas source to the air inlet and control the gas source to inject high-pressure gas into the chamber through the air inlet.

[0090] Connect the gas collection device to the exhaust section;

[0091] Intake pressure data is obtained based on the intake volume of the intake section;

[0092] Exhaust pressure data is obtained based on the exhaust volume of the exhaust section;

[0093] Obtain the grouting pressure data of the grouting section;

[0094] Permeability and nonlinear seepage factor are obtained based on air intake volume, air intake pressure data, exhaust volume, exhaust pressure data, and grouting pressure data.

[0095] Example 2:

[0096] refer to Figure 4 This embodiment describes the process of obtaining permeability using the apparatus and method of Embodiment 1:

[0097] Step 1: Set the particle size range and continuous gradation conditions of the sample and load the rock mass sample. Calculate the mass of crushed stone of different particle sizes according to the Talbot classification method, weigh it and load it into the chamber. Place piston 2 in the chamber above the sample and make piston 2 contact the pressure end of axial displacement control device 1.

[0098] Step 2: Connect the pipes and get them ready;

[0099] Step 3: Install data acquisition equipment such as flow meters and pressure gauges for detecting air intake volume, air intake pressure, exhaust volume, exhaust pressure, and grouting pressure.

[0100] Step 4, Adjusting the porosity of the sample: Install the linear variable differential transformer 4 on the test device, start the axial displacement control device 1 to load the piston 2, and control the height of the sample to adjust the porosity of the sample.

[0101] The calculation process for porosity is as follows:

[0102] The formula for calculating the initial porosity φ0 after axial pressure loading is as follows:

[0103]

[0104] Where V0 is the volume of the rock mass sample under natural conditions after axial pressure loading; V S This represents the absolute compacted volume of the rock mass sample.

[0105] Absolute compacted volume V of rock mass sample S The calculation formula is as follows:

[0106]

[0107] Where, m s ρ is the mass of the rock mass sample. s The mass density of the rock mass sample is given.

[0108] The height of the rock mass sample is h m :

[0109] h m =H1+H2-H3-H4-H5-H6

[0110] Wherein, H1 is the measured data of the linear variable differential transformer 4; H2 is the height of the inner grouting cylinder 8; H3 is the height of the piston 2; H4 is the height of the second honeycomb porous air chamber 6; H5 is the height of the first honeycomb porous air chamber 9; and H6 is the height of the breathable fine gauze. During the experiment, H1, H2, H3, H4, H5, and H6 are all known or measurable, and the height of the breathable fine gauze H6 is relatively small compared to the other values ​​and can be ignored. When the axial displacement control device 1 is activated to load the piston 2, the sample moves downward by Δh, and the measured data H1 of the linear variable differential transformer 4 changes.

[0111] From the above, the formula for calculating the volume V0 of a rock mass sample under natural conditions after axial pressure loading is as follows:

[0112] V0=πr 2 h m

[0113] Where r is the radius of the bottom surface of the inner grouting cylinder; h m The height of the rock mass sample after axial pressure loading.

[0114] The corrected formula for calculating the initial porosity φ0 after axial pressure loading is as follows:

[0115]

[0116] Step 5, begin the seepage grouting test:

[0117] First, open the gas injection line, keep the axial loading pressure constant, open the gas valve of the high-pressure nitrogen tank in the gas injection line, and adjust the gas injection pressure by connecting it to the pressure reducing valve. Adjust the pressure reducing valve until the gas pressure is stable and constant.

[0118] Subsequently, the grouting pipeline is opened. By setting a pressure reducing valve between the pressure stabilizing tank and the grouting tank, during the preparation stage, the pressure reducing valve between the pressure stabilizing tank and the grouting tank and the exhaust valve of the pressure stabilizing tank are closed, the air inlet valve of the pressure stabilizing tank is opened, the air pump is turned on until the pressure in the pressure stabilizing tank reaches the set pressure, the air pump is turned off, then the air inlet valve is closed, the pressure reducing valve and the mud valve are opened, and high-pressure gas is delivered from the pressure stabilizing tank to the grouting tank, and the grout is squeezed into the chamber through the mud valve. The grouting pressure is controlled to remain constant by adjusting the pressure reducing valve and the mud valve.

[0119] The changes in grout flow rate and gas flow rate during the grouting process are measured. During this process, flow meters installed at the grouting port and air inlet in the chamber, and pressure sensors installed at the air inlet and air outlet respectively monitor the grout flow rate, air inlet flow rate, air inlet gas pressure, and air outlet gas pressure and feed the data back to the data acquisition unit.

[0120] After grouting begins, the formula for calculating the porosity of the rock mass sample is:

[0121]

[0122] Where V0 is the volume of the rock mass sample under natural conditions after axial pressure loading; V S V is the absolute compacted volume of the rock mass sample; r This refers to the volume of grout injected into the rock mass sample.

[0123] Volume V of grout injected into the rock mass sample r The following relationship can be obtained from the flow meter at the grouting port:

[0124]

[0125] in, For T i The cumulative flow rate of the slurry pipeline at any given time.

[0126] Based on the measured gas flow rate data, the velocity of the seeping gas can be calculated as follows:

[0127]

[0128] in, ν is the gas flow rate at the air inlet; r is the bottom radius of the inner grouting cylinder; ν is the velocity of the seeping gas.

[0129] According to Forchheimer's theory, the fluid in a rock mass sample satisfies:

[0130]

[0131] Where μ is the fluid dynamic viscosity coefficient; k is the permeability of the mining-induced fractured rock mass; β is the non-Darcy factor; ρ ωυ is the fluid density; p is the fluid velocity; and ν is the fluid pressure.

[0132] Based on extensive experimental and simulation results, the empirical formula for the non-Darcy factor is as follows:

[0133]

[0134] Based on experimental measurement data:

[0135] -Δp=p in -p out

[0136] Where, p in p is the gas pressure at the air inlet. out This refers to the gas pressure at the outlet.

[0137] The corrected formula for calculating permeability is:

[0138]

[0139] Where, p in p is the gas pressure at the air inlet. out ρ is the gas pressure at the outlet. ω m is the fluid density. s ρ is the mass of the rock mass sample. s The mass density of the rock mass sample; The gas flow rate at the air inlet; r is the bottom radius of the inner grouting cylinder; h m The height of the rock mass sample after axial pressure loading; For T i The cumulative flow rate of the slurry pipeline at any given time.

[0140] After the test is completed, close the mud valve and pressure reducing valve, open the exhaust valve to purge the gas from the stabilizing tank, clean the grouting tank, and the test is complete.

[0141] Step 6, Data Analysis: The computer acquires the data stored in the recorder, and uploads data such as the gas flow rate at the air inlet, the gas pressure at the inlet and outlet, and the cumulative flow rate of the grout pipe to the computer. After analyzing and processing the data, the permeability of the mining-induced fractured rock mass at different times under grouting conditions is finally obtained.

[0142] Example 3:

[0143] Based on the permeability calculation process in Example 2, we provide a specific application example. Red sandstone is selected as the rock sample for testing. It is crushed into particles using a rock crusher and sieved using a screen. The particle sizes selected are: Particle size 1 (0-5 mm), Particle size 2 (5-10 mm), Particle size 3 (10-15 mm), Particle size 4 (15-20 mm), and Particle size 5 (20-25 mm). The Talbot index is set to 1. Based on the Talbot index, which characterizes particle size distribution, 1200 g of red sandstone with different particle sizes is mixed. Then, an axial load is applied to adjust the porosity of the sample. The initial porosity of the sample is set to 0.183, and the sample height is 130 mm. After starting the seepage grouting test, maintain the axial loading pressure at 3 MPa. Turn on the high-pressure nitrogen tank and adjust the pressure reducing valve to a stable pressure of 0.3 MPa, then keep the gas pressure constant. Close the pressure reducing valve and exhaust valve, open the air inlet valve, and turn on the air pump until the pressure in the pressure stabilizing tank reaches the set pressure, then turn off the air pump. Close the air inlet valve, open the pressure reducing valve and mud valve, and deliver high-pressure gas from the pressure stabilizing tank into the grouting tank. Control the grouting pressure to a stable value of 1 MPa by adjusting the air inlet valve and mud valve, then keep the grouting pressure constant.

[0144] The changes in grout flow rate and gas flow rate during the grouting process are measured. During this process, flow meters at the grouting port and air inlet, and pressure sensors at the grouting port, air inlet, and air outlet monitor the grout flow rate, air inlet flow rate, and air outlet gas pressure, respectively, and feed these data back to the data acquisition unit. The computer processes the data to obtain the following results: Figure 4 The permeability change graph shown is a broken line graph.

[0145] Example 4:

[0146] This embodiment describes the process of obtaining the nonlinear seepage factor using the apparatus and method of Embodiment 1: combined with the relationship satisfied by the fluid in the rock mass sample obtained in Embodiment 2:

[0147]

[0148] Based on this, the nonlinear seepage factor is defined to satisfy the following relationship:

[0149]

[0150] Where μ is the fluid dynamic viscosity coefficient; k is the permeability of the mining-induced fractured rock mass; β is the non-Darcy factor; ρ ω υ is the fluid density; p is the fluid velocity; and ν is the fluid pressure.

[0151] Substituting the empirical formula for the non-Darcy factor and the porosity formula, the corrected nonlinear seepage factor can be obtained as follows:

[0152]

[0153] Where, ρ ω m is the fluid density. s ρ is the mass of the rock mass sample; s The mass density of the rock mass sample; The gas flow rate at the air inlet; r is the bottom radius of the inner grouting cylinder; h m The height of the rock mass sample after axial pressure loading; For T i The cumulative flow rate of the slurry in the pipeline at any given time; μ is the fluid dynamic viscosity coefficient.

[0154] Example 5:

[0155] Based on the calculation process of the nonlinear seepage factor in Example 4, we provide a specific application example. Red sandstone is selected as the rock sample for testing. It is crushed into particles using a rock crusher and sieved. The particle sizes are selected as follows: Particle size 1 (0-5 mm), Particle size 2 (5-10 mm), Particle size 3 (10-15 mm), Particle size 4 (15-20 mm), and Particle size 5 (20-25 mm). The Talbot index is set to 1. Based on the Talbot index, which characterizes particle size distribution, 1200 g of red sandstone with different particle sizes is mixed. An axial load is then applied to adjust the porosity of the sample. The initial porosity of the sample is set to 0.242, and the sample height is 140 mm. After starting the seepage grouting test, maintain the axial loading pressure at 3 MPa. Turn on the high-pressure nitrogen tank and adjust the pressure reducing valve to a stable pressure of 0.3 MPa, then keep the gas pressure constant. Close the pressure reducing valve and exhaust valve, open the air inlet valve, and turn on the air pump until the pressure in the pressure stabilizing tank reaches the set pressure, then turn off the air pump. Close the air inlet valve, open the pressure reducing valve and mud valve, and deliver high-pressure gas from the pressure stabilizing tank to the grouting tank. Control the grouting pressure to a stable value of 2 MPa by adjusting the air inlet valve and mud valve, then keep the grouting pressure constant.

[0156] The changes in grout flow rate and gas flow rate during the grouting process are measured. During this process, flow meters at the grouting port and air inlet, and pressure sensors at the grouting port, air inlet, and air outlet monitor the grout flow rate, air inlet flow rate, and air outlet gas pressure, respectively, and feed these data back to the data acquisition unit. The computer processes the data to obtain the following results: Figure 5 The graph shown is a line graph illustrating the variation of the nonlinear seepage factor.

[0157] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0158] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting test, characterized in that, include: A real-time synchronous permeability measurement test device for grouting in mining-induced fractured rock masses includes: The base (13) is placed inside the pressure device, and the base (13) has a chamber for storing the sample; An air inlet is provided at the bottom of the chamber. The exhaust end of the air inlet is in contact with the bottom of the sample. The air inlet end of the air inlet is located outside the base (13). The air inlet is used to communicate with a gas source and inject high-pressure gas into the chamber. An exhaust section is provided at the top of the chamber. The air inlet of the exhaust section is in contact with the top of the sample. The exhaust section is provided inside the piston (2). The piston (2) is slidably provided in the chamber. The exhaust end of the exhaust section is located outside the piston (2). The top of the piston (2) is mounted on the pressure end of the pressure application device. The grouting part is wrapped around the side wall of the sample. The bottom of the grouting part is fixed to the base (13). The liquid outlet of the grouting part is connected to the chamber and is used to inject grout into the chamber. A displacement sensor is used to detect the height of the piston (2) above the top of the chamber to obtain the sample height; It also includes the following steps: The sample is filled into the cavity, and the piston (2) is controlled to contact the sample. The pressure end of the pressure application device drives the piston (2) to press down the sample, adjusts the porosity of the sample, and detects the displacement of the pressure end of the pressure application device by a displacement sensor; After the target initial porosity is reached, the pressure is released to a stable value and the loading pressure at the pressure end of the pressure application device is kept constant. The air source and grouting mechanism are then turned on to inject grout into the chamber to start the seepage grouting test. The grouting unit is controlled to inject grout into the grouting mechanism so that the grout is injected into the cavity; Connect the gas source to the air inlet and control the gas source to inject high-pressure gas into the chamber through the air inlet; Connect the gas collection device to the exhaust section; The intake pressure data is obtained based on the intake volume of the intake section; The exhaust pressure data is obtained based on the exhaust volume of the exhaust section; Obtain the grouting pressure data of the grouting section; Based on the air intake volume, air intake pressure data, exhaust volume, exhaust pressure data, and grouting pressure data, the permeability and nonlinear seepage factor are obtained. The revised formula for calculating permeability is: ； in, This refers to the gas pressure at the air inlet. This refers to the gas pressure at the outlet. For fluid density; The mass of the rock mass sample. The mass density of the rock mass sample; This refers to the gas flow rate at the air inlet. The radius of the bottom surface of the inner grouting cylinder; The height of the rock mass sample after axial pressure loading; for The cumulative flow rate of the slurry pipeline at any given time; The fluid dynamic viscosity coefficient; The corrected nonlinear seepage factor is: ； in, For fluid density; The mass of the rock mass sample; The mass density of the rock mass sample; This refers to the gas flow rate at the air inlet. The radius of the bottom surface of the inner grouting cylinder; The height of the rock mass sample after axial pressure loading; for The cumulative flow rate of the slurry pipeline at any given time; is the fluid dynamic viscosity coefficient.

2. The method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting test according to claim 1, characterized in that, The grouting section includes: The inner grouting cylinder (8) is axially connected to the base (13) at its bottom. The chamber is located inside the inner grouting cylinder (8). A plurality of grouting holes for communicating with the chamber are evenly opened on the side wall of the inner grouting cylinder (8). The outer cylinder (7) is coaxially arranged outside the inner grouting cylinder (8). The bottom of the outer cylinder (7) is fixedly connected to the top of the base (13), and the top of the outer cylinder (7) is fixedly connected to the top of the inner grouting cylinder (8). The inner wall of the outer cylinder (7) and the outer wall of the inner grouting cylinder (8) together form a grout storage cavity, and the grout storage cavity is connected to the inlet end of a plurality of grouting holes; The slurry storage chamber is connected to a grouting port (10), which is located on the outer cylinder (7).

3. The method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting test according to claim 1, characterized in that, The air intake includes: The first honeycomb porous air chamber (9) is located at the bottom of the chamber. The air inlet of the first honeycomb porous air chamber (9) is connected to the exhaust end of the air inlet pipe. The air inlet pipe is buried in the base (13). The air inlet (12) of the air inlet pipe is located on the side wall of the base (13). The air inlet (12) is used to connect to the air source. A breathable fine gauze (14) is laid between the exhaust end of the first honeycomb porous air cavity (9) and the sample.

4. The method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting test according to claim 1, characterized in that, The exhaust section includes: The second honeycomb porous air chamber (6) is slidably disposed in the chamber. The second honeycomb porous air chamber (6) is fixed to the bottom of the piston (2). The air inlet end of the second honeycomb porous air chamber (6) is in contact with and connected to the top of the sample. The air outlet end of the second honeycomb porous air chamber (6) is connected to the air inlet end of the exhaust pipe. The exhaust pipe is embedded in the piston (2). The air outlet (3) of the exhaust pipe is opened on the side wall of the piston (2).

5. The method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting test according to claim 2, characterized in that, The displacement sensor includes: A linear variable differential transformer (4) is provided, with its fixed end fixed to the top of the inner grouting cylinder (8) and its movable end fixed to the pressure end of the pressure applying device.

6. The method for real-time synchronous measurement of permeability in mining-induced fractured rock mass grouting test according to claim 5, characterized in that, The pressure application device includes: An axial displacement control device (1) is provided, wherein the base (13) is placed inside the axial displacement control device (1), and the movable end of the axial displacement control device (1) is fixedly connected to the top of the piston (2). The movable end of the linear variable differential transformer (4) is fixed to the movable end of the axial displacement control device (1).

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