WO2020133729A1 - 真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法及系统 - Google Patents

真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法及系统 Download PDF

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WO2020133729A1
WO2020133729A1 PCT/CN2019/078443 CN2019078443W WO2020133729A1 WO 2020133729 A1 WO2020133729 A1 WO 2020133729A1 CN 2019078443 W CN2019078443 W CN 2019078443W WO 2020133729 A1 WO2020133729 A1 WO 2020133729A1
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Prior art keywords
valve
stress
coal
test
mining
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PCT/CN2019/078443
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English (en)
French (fr)
Inventor
高明忠
李聪
张茹
张泽天
谢晶
鲁义强
邓光迪
何志强
彭高友
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四川大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
    • G01N15/082—Investigating permeability by forcing a fluid through a sample
    • G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
    • G01N3/12—Pressure testing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0019—Compressive
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003—Generation of the force
    • G01N2203/0042—Pneumatic or hydraulic means
    • G01N2203/0044—Pneumatic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0075—Strain-stress relations or elastic constants

Definitions

  • the invention belongs to the field of geotechnical engineering, and relates to an in-situ test method and a test system for the mechanical behavior and seepage characteristics of coal rock mass under the influence of real mining stress.
  • coal and rock masses are not only affected by loading, but also by many factors such as fluid migration, temperature, biological or chemical substances, and the influencing factors are interrelated to form a complete multi-field coupling to coal and rock masses. Function, which in turn affects the mechanical response of coal and rock masses, so that coal and rock masses show significant differences in mechanical properties in different specific practices.
  • the initiation, expansion and evolution of mining fracture network in coal and rock mass have a crucial influence on the gas migration in it. Mining fracture network is always the main gas migration channel in coal and rock body. Therefore, the influence of in-situ stress state and the real disturbance path must be considered, and the disturbance of engineering activities such as mining or excavation should be combined with the seepage characteristics of coal and rock bodies to carry out research.
  • CN104374684A discloses a system for testing the permeability of unloaded coal and rock mass during mining, which mainly includes a gas source, a vacuum pump, a gas pressure stabilizing and temperature-increasing control device, an MTS confining pressure chamber with a test piece, and these components. Matching valves, pressure gauges and flow meters.
  • This test system can realize the application of external gas pressure constant temperature and seepage conditions based on the MTS rock mechanics test system accurately controlling coal rock loading and recording stress and deformation data.
  • the test system still has the following deficiencies that need to be improved :
  • test system can achieve stable and accurate test of permeability of unloaded coal rock mass during mining, in fact, the test system is still tested in the laboratory state, and its loading method It is ideal and can only approximate the process of mining stress change, but the actual mining stress change is very complicated. The test system does not consider and cannot combine the influence of the actual mining stress environment into the test process.
  • the permeability of coal and rock masses has significant stress and porosity sensitivity, so it is impossible to accurately test the permeability of coal and rock masses by using this test system only by ideally simulating the change process of mining stress. The accuracy and reference of the results still need to be improved.
  • the loading method of the test system is a single linear load.
  • the evolution process of mining stress is very complicated.
  • the test system cannot reflect the influence of the supporting pressure fluctuation characteristics on the permeability of coal and rock mass.
  • test process of the test system is completed in the laboratory, and it is not in the in-situ environment. It is necessary to design a gas heater and a heating controller to control the gas temperature in advance, and the temperature of the deep mining site varies with the geological conditions. The difference will be different, so the test system is difficult to accurately simulate the actual temperature conditions, because the temperature will affect the fluid movement in the coal and rock mass, and thus affect the mechanical response of the coal and rock mass, which is not conducive to the accuracy of the test results Improvement.
  • the test system is mainly based on the MTS rock mechanics test system, which is a laboratory device and cannot be directly applied in the underground environment of deep mining.
  • the existing linear loading simulation method for indoor experiments is only a research method for the properties of materials, and is not related to engineering disturbances.
  • the mechanical behavior and seepage characteristics of coal and rock masses under the real disturbance path at the site scale were developed The in-situ test equipment and related test methods are very necessary.
  • the purpose of the present invention is to overcome the deficiencies of the prior art and provide in-situ testing methods and systems for the mechanical behavior and seepage characteristics of coal and rock masses under the influence of real mining stress, so as to solve that the existing indoor test devices and methods cannot reflect the real mining stress Under the influence, the mechanical behavior and seepage characteristics of coal and rock masses are insufficient.
  • the in-situ test system for the mechanical behavior and seepage characteristics of coal and rock bodies under the influence of real mining stress includes a gas source, a vacuum pump, a test component, a signal acquisition and transmission component and a ground monitoring station,
  • the test assembly includes a top pressure plate, a loading piece, a test piece, a bottom pressure plate, an anchor cable stress gauge, a flat jack, an axial displacement gauge, a radial displacement gauge, and a gas isolation cavity.
  • the gas isolation cavity is a cylindrical body, and the One end is a cylindrical loading head, the outer diameter of the loading head matches the inner diameter of the gas isolation chamber, the loading head is provided with a sealing ring, and the loading member is provided with a gas guide through hole that is open to the end surface of the loading head and the sidewall of the loading member, There are air guide holes and cable holes on the bottom pressure plate;
  • the test assembly is installed in a cut provided on a coal rock body in front of the mining face, and a flat jack, an anchor cable stress gauge, a bottom pressure plate, a test piece, a loading piece, and a top pressure plate are sequentially installed from the bottom to the top, The flat jack and the top pressure plate are in contact with the bottom and top surfaces of the cut respectively.
  • the part where the cut is in contact with the flat jack and the top pressure plate is a horizontal plane.
  • the lower end of the gas isolation cavity is fixed on the bottom pressure plate, and the test piece is placed vertically in the gas isolation cavity ,
  • the end face of the loading head is in contact with the top of the test piece and is located in the gas isolation chamber, the axial displacement gauge and the radial displacement gauge are installed on the test piece, and the cables of the axial displacement gauge and the radial displacement gauge pass through the bottom pressure plate
  • the cable through hole on the top leads to the gas isolation cavity;
  • the signal acquisition and transmission component includes a displacement collector, a stress collector, and a downhole information collection station.
  • the stress collector is connected to the anchor cable stress gauge, and the displacement collector is connected to the axial displacement gauge and the radial displacement gauge, respectively.
  • the stress collector is connected to the underground information collection station through a cable;
  • the ground monitoring station includes a ground monitoring computer;
  • the gas source is connected to the gas isolation cavity through the intake line, and the gas isolation cavity is communicated with the gas outlet line through the air guide through hole on the bottom pressure plate, and the gas source is connected to one end of the first valve and the second valve respectively through the first pressure reducing valve ,
  • the other end of the first valve is connected to the vacuum pump, and the other end of the second valve is communicated through the second pressure reducing valve, the first flow meter and the air guide through hole on the loading member, between the first flow meter and the loading member
  • the pipeline is provided with a first pressure sensor
  • the intake pipeline is provided with branch pipelines connecting the two ends of the second pressure reducing valve
  • the branch pipeline is provided with a third valve
  • the air guide hole on the bottom pressure plate passes through the fourth valve and the second flowmeter Connected
  • a second pressure sensor is provided on the pipeline behind the second flowmeter
  • the first pressure sensor, the second pressure sensor, the first flowmeter and the second flowmeter are connected to the underground information collection station via a cable, and the underground information collection
  • the axis of the piston rod of the flat jack, the stress probe of the anchor cable stress gauge, the air guide through hole on the bottom pressure plate, the test piece and the loading piece are on the same straight line.
  • the diameter of the piston rod of the flat jack is larger than the diameter of the stress probe of the anchor cable stress gauge
  • the size of the bottom pressure plate is larger than the size of the stress probe of the anchor cable stress gauge
  • the size of the top pressure plate and the bottom pressure plate is larger than that of the gas
  • the top pressure plate and the bottom pressure plate are rectangular or square steel plates.
  • the side length of the square steel plate and the width of the rectangular steel plate are larger than the outer diameter of the gas isolation chamber.
  • the top pressing plate and the bottom pressing plate may be formed by overlapping and combining multiple steel plates.
  • the test piece is cylindrical, the surface of the test piece is wrapped and sealed by a plastic film, and the test piece is processed from coal and rock bodies collected from the mining face.
  • the cut is located at least 200m in front of the mining face.
  • a seal is provided between the lower end of the gas isolation chamber and the bottom pressure plate, and a seal is provided between the cable through hole on the bottom pressure plate and the cable passing through the cable through hole, and
  • the sealing ring on the loading part cooperates to increase the airtightness of the gas isolation cavity.
  • the flat jack is a flat jack with a pressure gauge.
  • the underground information collection station is a device that transmits the signals collected by the equipment connected to it to the surface monitoring station, and transmits the instructions issued by the surface monitoring station to the components connected to it. Specifically, the underground information collection station transmits the signals collected by the first pressure sensor, the second pressure sensor, the displacement collector, the stress collector, the first flow meter, and the second flow meter connected to the ground monitoring station. And transmit the instructions issued by the ground monitoring station to the connected first pressure reducing valve, second pressure reducing valve, first valve, second valve, third valve, fourth valve and vacuum pump equipment.
  • the underground information collection station can be a downhole ring network switch. By integrating the control bus of the test system with the information transmission bus, the cable is connected to the downhole ring network switch.
  • mine explosion-proof and intrinsically safe network switches It is preferable to use mine explosion-proof and intrinsically safe network switches.
  • This type of network switch is allowed to be installed in the dangerous gas environment with coal dust and gas explosions in coal mines.
  • the equipment used to connect the underground to the switch for data communication with the ground Exchange for remote control and remote monitoring.
  • the ground monitoring computer in the ground monitoring station can manage the equipment connected to the switch underground, and the network computer can obtain the data information and control management of the related underground equipment through the switch.
  • the first pressure reducing valve and the second pressure reducing valve are electric pressure reducing valves
  • the first valve, the second valve, the third valve and the fourth valve are electric ball valves
  • the valve, the second valve, the third valve, and the fourth valve are all connected to the ground monitoring computer through a cable, and are opened and closed remotely through the ground monitoring computer.
  • the vacuum pump is connected to the ground monitoring computer through a cable, and the ground pump is used to remotely control the state that the vacuum pump is running or stopped.
  • multiple cuts can be designed in different parts of the coal and rock body in front of the mining face and a test system can be installed, so as to realize the simultaneous determination of test pieces in different parts.
  • the present invention also provides an in-situ test method for the mechanical behavior and seepage characteristics of coal rock mass under the influence of real mining stress.
  • the method includes the following steps:
  • step 6 Through analysis of the data collected in step 5, the mechanical behavior and seepage characteristic data of coal and rock mass under the influence of real mining stress are obtained.
  • the confining pressure condition in step 4 is determined according to the actual test requirements.
  • the confining pressure can be kept constant at all times, and the confining pressure can also be changed in a manner of increasing or decreasing gradually.
  • the mechanical data of the coal and rock mass include rock mechanical parameters such as the leading bearing pressure distribution at different distances from the mining face, the stress-strain curve of the specimen, the elastic modulus of the specimen, and the Poisson's ratio.
  • the seepage characteristic data includes: stress-permeability relationship curve and so on.
  • the change of permeability of coal and rock mass affected by mining during the progress of mining face can be obtained, including peak strength, strain corresponding to peak strength, axial strain, hoop strain, body strain,
  • the mechanical property data of coal and rock masses including residual strength, secant elastic modulus, secant Poisson's ratio, etc., can also be used to obtain seepage characteristic data including changes in permeability of coal and rock masses that vary with stress state.
  • the in-situ test system for mechanical behavior and seepage characteristics of coal and rock mass provided by the present invention includes gas source, vacuum pump, test component, signal acquisition and transmission component and ground monitoring station.
  • the test system tests the mechanical behavior and seepage characteristics of the coal and rock body under the influence of real mining stress.
  • This structural feature is currently not available in indoor test equipment Therefore, the test system of the present invention solves the deficiency that the existing indoor test device cannot reflect the mechanical behavior and seepage characteristics of coal and rock bodies under the influence of real mining stress.
  • test results obtained by the test system of the present invention can more accurately and accurately reflect the seepage characteristics of coal and rock bodies during coal seam mining, and are safe and efficient for coal mines such as gas drainage, explosion-proof water sheds, and top coal pre-cracking in top coal mining. Production provides more reliable, more valuable data for reference and reference.
  • the test system provided by the present invention uses a displacement gauge and a stress gauge that are digitized and automatically collected.
  • the first pressure reducing valve and the second pressure reducing valve are electric pressure reducing valves, and the first valve, the second valve, the third valve and
  • the fourth valve is an electric ball valve.
  • Each pressure reducing valve, valve, and vacuum pump can be remotely controlled by the ground monitoring computer, which is beneficial to reduce manual control of each pressure reducing valve, the opening, closing, and opening degree of each valve, as well as the opening and closing of the vacuum pump. Closed labor intensity, shorten the response time of parameter adjustment, improve test efficiency, and reduce manual adjustment errors.
  • the test system provided by the present invention has a simple and compact structure, avoids the complexity of a complicated large loading system, saves manpower and material resources, and is beneficial to popularization and application.
  • the in-situ test method for the mechanical behavior and seepage characteristics of coal rock mass under the influence of real mining stress provided by the present invention, the test process is the real mining dynamics process under the influence of advanced bearing pressure, which is a non-linear loading method. Compared with the traditional indoor test method, it is more in line with the actual situation on site.
  • the method of the present invention breaks through the bottleneck of the laboratory scale test and is difficult to restore the bottlenecks of in-situ mechanical change characteristics such as on-site coal rock fracture evolution and seepage characteristics. Through the method of the present invention, the mechanical parameters of the coal rock body under the real disturbance stress path can be obtained.
  • rock mechanical parameters, stress-permeability relationship curves, etc. which can be obtained at different distances from the mining face, such as advance bearing pressure distribution, sample stress-strain curve, sample elastic modulus, Poisson's ratio, etc.
  • the determination of the location of the gas drainage borehole, the adjustment of the support strength (advance support, the spacing between the bolts and the arrangement of the anchor cables, etc.), and the study of the in-situ mechanical theory of rock provide test methods.
  • the coal mining stress change and seepage characteristics can be obtained, and the dynamic properties of in-situ disturbance in the geological environment of the coal seam can be obtained, which can provide test methods for the mining rock mechanics theory and in-situ disturbance rock mechanics , To provide new ideas for the evaluation of coal seam permeability enhancement in the joint mining of coal and gas, and to provide more accurate reference data for coal mine safety production.
  • FIG. 1 is a schematic structural view of the test system of the present invention
  • Figure 2 is a schematic diagram of the test component and its installation in the cutout
  • Figure 3 is a schematic diagram of the structure of the loading head
  • Figure 4 is a schematic diagram of the arrangement of cuts on the coal rock body, and the arrows in the figure refer to the direction of the face advancement;
  • the flat jack used is a flat jack with a pressure gauge
  • the anchor cable stress gauge used is the GPD450M mine intrinsically safe anchor (cable) stress sensor produced by Shandong Hengan Electronic Technology Co., Ltd. Standard number: MFB130447
  • the stress collector comes with a pressure acquisition device, which is mainly used to measure the stress change of the anchor rod (cable), and can be used for pressure measurement and automatic recording of pressure signals in the present invention
  • the axial displacement meter used is American Epsilon Model 3542 axial extensometer is suitable for the measurement of axial tensile and compressive deformation. In the present invention, it is used to measure the axial tensile and compressive deformation of the test piece.
  • the radial displacement meter used is the American Epsilon 3544 circumferential extensometer It is suitable for radial deformation measurement. In the present invention, it is used to measure the radial deformation of the test piece; the displacement collector used is an instrument that can be used to collect and record displacement signals, such as a digital signal conditioner.
  • the underground information collection station is a device that transmits the signals collected by the equipment connected to it to the surface monitoring station, and transmits the instructions issued by the surface monitoring station to the components connected to it. Specifically, the underground information collection station transmits the signals collected by the first pressure sensor, the second pressure sensor, the displacement collector, the stress collector, the first flow meter, and the second flow meter connected to the ground monitoring station. And transmit the instructions issued by the ground monitoring station to the connected first pressure reducing valve, second pressure reducing valve, first valve, second valve, third valve, fourth valve and vacuum pump equipment.
  • the underground information collection station specifically refers to the underground ring network switch.
  • the cable is connected to the underground ring network switch (for example, KJJ127 mine explosion-proof and intrinsically safe type) Network switch), KJJ127 mine explosion-proof and intrinsically safe network switch is allowed to be installed in the dangerous gas environment with coal dust and gas explosion under the coal mine. It is used to exchange data between the equipment that can be connected to the switch underground and the ground. Remote control and remote monitoring.
  • the ground monitoring computer in the ground monitoring station can manage the equipment connected underground to the switch, and the network computer can obtain the data information and control management of the related equipment underground through the switch.
  • FIG. 1 a schematic structural diagram of an in-situ test system for the mechanical behavior and seepage characteristics of coal and rock masses under the influence of real mining stress is shown in FIG. 1, including a gas source 1, a vacuum pump 2, a test component 3, a signal acquisition and transmission component and Ground monitoring station 4.
  • FIG. 2 The schematic diagram of the test assembly of the test assembly 3 and its installation in the cutout are shown in FIG. 2, including the top pressing plate 5, the loading member 6, the test piece 7, the bottom pressing plate 8, the anchor cable stress gauge 9, the flat jack 10, Axial displacement gauge, radial displacement gauge and gas isolation chamber 11.
  • the top pressure plate 5 and the bottom pressure plate 8 are square steel plates of the same shape, the gas isolation chamber 11 is a cylinder, and the schematic structural diagram of the loading member is shown in FIG.
  • the loading member 6 is loaded by a cylindrical body and a cylinder at one end of the body Composed of head 6-1, the outer diameter of the loading head matches the inner diameter of the gas isolation chamber, the loading head is provided with a sealing ring 12, the loading member is provided with a gas conducting hole 13 opening at the end face of the loading head and the side wall of the body, the bottom
  • the pressure plate is provided with a gas conduction through hole 13 and a cable through hole 14, the test piece 7 is cylindrical, the surface of the test piece is wrapped and sealed by a plastic film, and the test piece is processed from coal and rock bodies collected from the mining face.
  • the square steel plate with a side length of 300mm on the top and bottom platen, the thickness is determined according to the actual situation on site.
  • the diameter of the piston rod of the flat jack is larger than the diameter of the stress probe of the anchor cable stress gauge
  • the size of the bottom pressure plate is larger than the size of the stress probe of the anchor cable stress gauge
  • the side length of the top pressure plate and the bottom pressure plate is greater than the outer diameter of the gas isolation chamber of the test piece .
  • the test assembly 3 is installed in an undercut 15 provided on a coal rock body 200 meters in front of the mining face.
  • the undercut is composed of an outer groove and an inner groove that are connected to each other.
  • the outer groove is in an arch structure, and the inner groove is in a rectangular parallelepiped structure ,
  • the flat jack 10, the anchor cable stress gauge 9, the bottom pressure plate 8, the test piece 7, the loading piece 6 and the top pressure plate 5 are installed in the inner groove of the cut in order from the bottom to the top, the flat jack 10 and the top pressure plate 5 and the cut respectively
  • the bottom surface of the inner groove is in contact with the top surface.
  • the bottom surface and the top surface of the cut inner groove are horizontal.
  • the lower end of the gas isolation chamber 11 is fixed to the bottom pressure plate 8 by bolts; the piston rod of the flat jack, the stress probe of the anchor cable stress gauge, The axes of the air conduction holes, the test piece and the loading piece on the bottom pressure plate are on the same straight line, and the center of the top pressure plate and the center of the bottom pressure plate are on the same straight line with the axis of the test piece.
  • the test piece 7 is placed vertically in the gas isolation chamber 11 and the end face of the loading head 6-1 It is in contact with the top of the test piece 7 and is located in the gas isolation chamber 11.
  • Both the axial displacement gauge 16 and the radial displacement gauge 17 are installed on the test specimen 7, and the cables of the axial displacement gauge 16 and the radial displacement gauge 17 pass through
  • the cable through hole 14 on the bottom pressure plate leads out of the gas isolation cavity.
  • a seal is provided between the cable through hole on the bottom pressure plate and the cable passing through the cable through hole to increase the airtightness of the gas isolation cavity.
  • the signal acquisition and transmission assembly includes a displacement collector 18, a stress collector 19, and a downhole information collection station 20.
  • the stress collector 19 is connected to the anchor cable stress gauge 9, and the displacement collector 18 is connected to the axial displacement gauge 16 and the radial displacement, respectively.
  • the gauge 17 is connected, and the displacement collector 18 and the stress collector 19 are connected to the underground information collection station 20 through a cable;
  • the surface monitoring station 4 includes a surface monitoring computer.
  • the gas source 1 communicates with the gas isolation chamber 11 through the intake pipe, and the gas isolation chamber 11 communicates with the gas outlet pipe through the gas guide through hole 13 on the bottom pressure plate 8, and the gas source 1 passes through the first pressure reducing valve 21 and the first valve respectively 23 is connected to one end of the second valve 24, and the other end of the first valve 23 is connected to the vacuum pump 2.
  • the other end of the second valve 24 passes through the second pressure reducing valve 22, the first flow meter 27 and the gas guide on the loading member 6
  • the through hole 13 communicates, a first pressure sensor 29 is provided on the pipeline between the first flow meter 27 and the loading member 6, a branch pipeline connecting the two ends of the second pressure reducing valve 22 is provided on the intake pipeline, and a Three valves 25; the air guide hole 13 on the bottom pressure plate is connected to the second flow meter 28 through the fourth valve 26, and a second pressure sensor 30 is provided on the pipeline behind the second flow meter 28; the first pressure sensor 29, the first The two pressure sensors 30, the first flow meter 27 and the second flow meter 28 are connected to the underground information collection station 20 through a cable, and the underground information collection station 20 is connected to the surface monitoring computer through a cable.
  • the first pressure reducing valve and the second pressure reducing valve are electric pressure reducing valves
  • the first valve, the second valve, the third valve and the fourth valve are electric ball valves
  • the valve, the second valve, the third valve, and the fourth valve are all connected to the ground monitoring computer through a cable, and are opened and closed remotely through the ground monitoring computer.
  • the vacuum pump is connected to the ground monitoring computer through a cable, and the ground pump is used to remotely control the state that the vacuum pump is running or stopped.
  • this embodiment provides an in-situ test method for the mechanical behavior and seepage characteristics of coal and rock mass under the influence of real mining stress, including the following steps:
  • the average sulfur content (St,d) of the coal seam in this working face is between 2.22% and 2.39%, which is medium to high sulfur coal, low phosphorus, high volatile content and high calorific value, mainly semi-dark coal, bitumen Glossy, dense lumpy, partly with wire-like structure, with fine bands of mirror coal and bright coal, containing nodular pyrite nodules, the true density of each coal seam is generally about 1.6kg/L, and the apparent density is generally 1.45 kg/L.
  • the relevant provisions of the national standard "Measurement Methods for Physical and Mechanical Properties of Coal and Rock" processed into specimens with a diameter of 50 ⁇ 2mm and a height-to-diameter ratio of 2 ⁇ 0.2.
  • the non-parallelism of both ends of the specimen is not greater than 0.05mm.
  • the diameter deviation of the upper and lower ends is not more than 0.3mm, the surface of the test piece is smooth, to avoid the stress concentration caused by the irregular surface, and the sample is wrapped and sealed with plastic film after processing.
  • the fourth valve was adjusted during SF 6 to maintain this confining pressure condition.
  • the first pressure-reducing valve, the second pressure-reducing valve, the first valve, the second valve and the fourth valve are all opened and closed remotely by the monitoring computer of the ground monitoring station.
  • the ground pressure is adjusted by remotely adjusting the opening degree of the first pressure reducing valve, the second valve, the second pressure reducing valve, and the fourth valve through the ground monitoring computer of the ground monitoring station.
  • step 6 Through analysis of the data collected in step 5, the mechanical behavior and seepage characteristic data of coal and rock mass under the influence of real mining stress are obtained.
  • the method for acquiring seepage characteristic data of coal and rock bodies under the influence of real mining stress is described in the present invention. Assuming that the entire test process is an isothermal process and satisfies the ideal gas state equation, according to the compressible gas level linear stable flow Darcy formula, the permeability at different times can be calculated as follows:

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  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

一种真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统及以该测试系统为基础的原位测试方法，所述测试系统包括气源（1）、真空泵（2）、测试组件（3）、信号采集传输组件和地面监控站（4），所述测试组件（3）包括顶部压板（5）、加载件（6）、试件（7）、底部压板（8）、锚索应力计（9）、扁千斤顶（10）、轴向位移计（16）、径向位移计（17）和气体隔离腔（11），所述测试组件（3）安装于设置在采面前方的煤岩体上的掏槽（15）中，所述信号采集传输组件包括位移采集器（18）、应力采集器（19）和井下信息采集站（20），应力采集器（19）与锚索应力计（9）连接，位移采集器（18）分别与轴向位移计（16）和径向位移计（17）连接，位移采集器（18）和应力采集器（19）通过线缆与井下信息采集站（20）相连，井下信息采集站（20）通过线缆与地面监控站（4）连接。

Description

真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法及系统 技术领域
本发明属于岩土工程领域，涉及真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法及测试系统。
背景技术
进入深部开采阶段后，煤岩赋存应力和瓦斯压力显著增大，煤与瓦斯共采的实践也迎来了新的挑战。工程实践表明，煤岩体不仅受到荷载作用，还受到流体运移、温度、生物或化学物质作用等众多因素的影响，且各影响因素之间相互联系，形成对煤岩体完整的多场耦合作用，进而影响煤岩体的力学响应，使煤岩体在不同的具体实践中呈现出显著的力学性质差异。煤岩体采动裂隙网络的萌生、扩展和演化对瓦斯在其内的运移具有至关重要的影响，采动裂隙网络始终是煤岩体内最主要的瓦斯运移通道。因此，必须考虑原位应力状态和真实扰动路径的影响，将开采或开挖等工程活动的扰动与煤岩体的渗流特性相结合开展研究。
现有研究方法多为在室内尺度下开展的卸荷应力状态的煤岩体渗透率研究，仅局限于试验条件本身对渗透率的影响进行研究和阐述，尚无关于开采过程中真实采动应力环境影响下的煤岩体采动力学行为及渗流特性研究的报道。
例如，CN104374684A公开了用于测试采动过程卸荷煤岩体渗透率的系统，主要包括气源、真空泵、气体稳压增温控制装置、具有试件的MTS围压腔，还包括与这些部件配合的阀门、压力计和流量计等。该测试系统能在MTS岩石力学测试系统准确控制煤岩体加载、记录应力和变形数据的基础上，实现外部气体稳压恒温渗流条件的施加，但是，该测试系统仍然存在以下不足之处有待改进：
(1)虽然该文献中提到了该测试系统可以实现采动过程卸荷煤岩体渗透率的稳定准确测试，但实际上，该测试系统仍然是在实验室状态下进行测试的，其加载方式是理想性的，只能近似地模拟采动应力的变化过程，但实际的采动应力变化是非常复杂的，该测试系统未考虑也无法将真实采动应力环境的影响结合到测试过程中，而煤岩体的渗透率具有显著的应力和孔隙度敏感性，因此采用该测试系统仅通过理想化的模拟采动应力的变化过程是无法实现对煤岩体渗透率进行准确测试的，其测试结果的准确性和可借鉴性都还有待提高。
(2)该测试系统的加载方式为单一线性地加载，而实际上采动应力的演化过程是非常复杂的，该测试系统无法反应支承压力波动特性对于煤岩体渗透率的影响。
(3)该测试系统的测试过程在实验室内完成，并非处于原位环境，需要设计气体加热 器和加热控制器预先对气体温度进行调控，而深部开采所处地的温度随着地质条件的差异会有所不同，因此该测试系统难以精确模拟实际的温度条件，由于温度会影响煤岩体中的流体运移等，进而影响煤岩体的力学响应，这也不利于测试结果的准确性的提高。
(4)该测试系统主要是基于MTS岩石力学测试系统进行测试的，属于实验室装置，无法直接在深部开采的地下环境应用。
现有的室内试验线性加载模拟方法只是一种针对材料性质的研究方式，与工程扰动并不相关。为了突破室内尺度的测试系统及试验难以还原现场煤岩体裂隙演化以及渗流特性等原位力学变化特征的瓶颈，开发出能在现场尺度下开展真实扰动路径下煤岩体的力学行为及渗流特性的原位测试装置及相关的测试方法是十分必要的。
发明内容
本发明的目的在于克服现有技术的不足，提供真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法及系统，以解决现有室内试验装置及方法不能反映真实采动应力影响下煤岩体的力学行为和渗流特性不足。
本发明提供的真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，包括气源、真空泵，测试组件、信号采集传输组件和地面监控站，
所述测试组件包括顶部压板、加载件、试件、底部压板、锚索应力计、扁千斤顶、轴向位移计、径向位移计和气体隔离腔，气体隔离腔为圆筒体，加载件的一端为圆柱形的加载头，加载头的外径与气体隔离腔的内径匹配，加载头上设有密封圈，加载件上设有开口于加载头端面和加载件侧壁的导气通孔，底部压板上设有导气通孔和线缆通孔；
所述测试组件安装于设置在采面前方的煤岩体上的掏槽中，掏槽中从下到上依次安装扁千斤顶、锚索应力计、底部压板、试件、加载件和顶部压板，扁千斤顶和顶部压板分别与掏槽的底面和顶面接触，掏槽与扁千斤顶和顶部压板接触的部位为水平面，气体隔离腔的下端固定在底部压板上，试件竖放于气体隔离腔中，加载头的端面与试件的顶部接触并位于气体隔离腔中，轴向位移计和径向位移计均安装在试件上，轴向位移计和径向位移计的线缆穿过底部压板上的线缆通孔引出气体隔离腔；
所述信号采集传输组件包括位移采集器、应力采集器和井下信息采集站，应力采集器与锚索应力计连接，位移采集器分别与轴向位移计和径向位移计连接，位移采集器和应力采集器通过线缆与井下信息采集站相连；所述地面监控站包括地面监控计算机；
气源经进气管路与气体隔离腔连通，气体隔离腔经底部压板上的导气通孔与出气管路连通，气源经第一减压阀分别与第一阀门和第二阀门的一端连接，第一阀门的另一端与真空泵 连接，第二阀门的另一端经第二减压阀、第一流量计与加载件上的导气通孔连通，在第一流量计与加载件之间的管路上设有第一压力传感器，进气管路上设有连通第二减压阀两端的支管路，支管路上设有第三阀门；底部压板上的导气通孔经第四阀门与第二流量计连接，第二流量计之后的管路上设有第二压力传感器；第一压力传感器、第二压力传感器、第一流量计和第二流量计通过线缆与井下信息采集站连接，井下信息采集站通过线缆与地面监控计算机连接。
上述测试系统的技术方案中，扁千斤顶的活塞杆、锚索应力计的应力探头、底部压板上的导气通孔、试件以及加载件的轴线位于同一直线上。
上述测试系统的技术方案中，扁千斤顶的活塞杆的直径大于锚索应力计的应力探头的直径，底部压板的尺寸大于锚索应力计的应力探头的尺寸，顶部压板和底部压板的尺寸大于气体隔离腔的外径。所述的顶部压板和底部压板为矩形或正方形钢板，正方形钢板的边长、矩形钢板的宽度大于气体隔离腔的外径。为了方便测试组件在掏槽中的顺利安装，所述的顶部压板和底部压板可以由多块钢板重叠组合而成。
上述测试系统的技术方案中，试件呈圆柱形，试件表面由塑料膜包裹密封，试件由从采面采集的煤岩体加工而成。
上述测试系统的技术方案中，掏槽位于采面前方至少200m。
上述测试系统的技术方案中，气体隔离腔的下端与底部压板之间设有密封件，底部压板上的线缆通孔与穿过该线缆通孔的线缆之间设有密封件，与加载件上的密封圈配合增加气体隔离腔的密闭性。
上述测试系统的技术方案中，所述扁千斤顶为带压力表的扁千斤顶。
上述测试系统的技术方案中，井下信息采集站是把与之相连的设备采集到的信号传输给地面监控站，并把地面监控站发出的指令传输给与之相连的部件的设备。具体地，井下信息采集站是把与之相连的第一压力传感器、第二压力传感器、位移采集器、应力采集器、第一流量计、第二流量计采集到的信号传输给地面监控站，并把地面监控站发出的指令传输给与之相连的第一减压阀、第二减压阀、第一阀门、第二阀门、第三阀门、第四阀门和真空泵的设备。井下信息采集站可以为井下环网交换机，通过将测试系统的控制总线与信息传输总线整合，将电缆接至井下环网交换机上。优选采用矿用隔爆兼本安型网络交换机，这种类型的网络交换机允许安装在煤矿井下有煤尘和瓦斯爆炸的危险气体环境中，用来使井下可连接到交换机的设备与地面进行数据交换，实现远程控制和远程监测。地面监控站中的地面监控计算机就可以对井下连接到交换机的设备进行管理，通过交换机实现网络计算机对井下相关设 备获取数据信息和控制管理的工作。
为了减少人工操控各减压阀、各阀门的开启、关闭、开启程度，以及真空泵的开启和关闭的劳动强度、缩短参数调整的响应时间、提高测试效率，同时减小人工调整误差，上述测试系统的技术方案中，优选的技术方案为：
第一减压阀、第二减压阀为电动减压阀，第一阀门、第二阀门、第三阀门和第四阀门为电动球阀，第一减压阀、第二减压阀、第一阀门、第二阀门、第三阀门以及第四阀门均通过线缆与地面监控计算机连接，通过地面监控计算机远程控制开启与关闭。真空泵通过线缆与地面监控计算机连接，通过地面监控计算机远程控制真空泵处于运行或停止运行的状态。
上述测试系统的技术方案中，可在采面前方的煤岩体的不同部位设计多个掏槽并安装测试系统，以实现对不同部位的试件进行同时测定。
在上述测试系统的基础之上，本发明还提供了一种真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法，该方法包括以下步骤：
①从采面现场取芯制作试件，将试件表面用塑料膜包裹密封；
②在采面前方至少200m的采面轨道巷的采煤帮上开挖掏槽，将掏槽的顶面和底面用水泥糊成水平面，晾至水泥凝结；
③在掏槽中安装测试组件，将加载件的导气通孔与进气管路连通，将底部压板上的导气通孔与出气管路连通；
④用扁千斤顶对试件加载至初始应力状态并在后续测试过程中通过调整扁千斤顶使试件始终处于初始应力状态；关闭第四阀门、第一减压阀和第二减压阀，打开第一阀门、第二阀门和第三阀门，开启真空泵将管路及气体隔离腔中的气体抽出，然后关闭第一阀门、第三阀门、第四阀门，之后关闭真空泵，打开第一减压阀和第二减压阀向气体隔离腔中通入SF 6气体对试件施加围压，在通入SF 6气体的过程中调节第四阀门以保持围压条件；
⑤在采动过程中进行测试，通过应力采集器和位移采集器实时采集应力、轴向位移计与径向位移数据，实时传输给地面监控站并记录；
⑥通过分析步骤⑤采集的数据，获得真实采动应力影响下煤岩体的力学行为和渗流特性数据。
上述测试方法的技术方案中，之所以采用SF 6作为渗流气体，是因为SF 6是一种无色、无臭、无毒、不燃的惰性气体，具有优良的灭弧性能和绝缘性能，不会影响煤矿安全生产。
上述测试方法的技术方案中，步骤④中的围压条件根据实际测试需求进行确定，例如，可以始终保持恒定围压，围压也可以以逐步增大或减小的方式进行变化。
上述测试方法的技术方案中，所述煤岩体的力学行数据为包括：距离采面不同距离超前支承压力分布、试样应力-应变曲线、试件弹性模量及泊松比等岩石力学参数；所述的渗流特性数据包括：应力-渗透率关系曲线等。通过上述测试方法可以得到在采面推进过程中，受采动影响煤岩体渗透率的变化情况，还可以获得包括峰值强度、峰值强度对应的应变、轴向应变、环向应变、体应变、残余强度、割线弹性模量、割线泊松比等在内的煤岩体的力学特性数据，也可以获得包括随应力状态变化的煤岩体渗透率变化情况在内的渗流特性数据。
与现有技术相比，本发明产生了以下有益的技术效果：
1.本发明提供的煤岩体的力学行为和渗流特性原位测试系统括气源、真空泵、测试组件、信号采集传输组件和地面监控站，由于将包括试件在内的测试组件设置在位于采面前方的煤岩体上的掏槽中，因此该测试系统测试的是真实采动应力影响下的煤岩体的力学行为和渗流特性，这一结构特点现是有室内试验装置所不具备的，本发明的测试系统解决了现有室内试验装置不能反映真实采动应力影响下煤岩体的力学行为和渗流特性的不足。通过本发明的测试系统获取的测试结果，能更真实准确地反映煤层开采过程中煤岩体的渗流特性，为瓦斯抽采、防爆水棚、放顶煤开采中顶煤预裂等煤矿安全高效生产提供更可靠、参考和借鉴价值更高的数据。
2.本发明提供的测试系统采用的位移计、应力计为数字化、自动化采集，第一减压阀、第二减压阀为电动减压阀，第一阀门、第二阀门、第三阀门和第四阀门为电动球阀，各减压阀和阀门以及真空泵都可以通过地面监控计算机远程控制，这样有利于减少人工操控各减压阀、各阀门的开启、关闭、开启程度，以及真空泵的开启和关闭的劳动强度、缩短参数调整的响应时间、提高测试效率，减小人工调整误差。
3.本发明提供的测试系统的结构简单紧凑，避免了复杂大型加载系统的繁琐，节省人力与物力，有利于推广应用。
4.本发明提供的真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法，测试过程为超前支承压力影响下的真实采动力学过程，是一种非线性的加载方式，相比较于传统的室内试验方法，更符合现场实际。本发明的方法突破了室内尺度的测试试验难以还原现场煤岩体裂隙演化以及渗流特性等原位力学变化特征的瓶颈，通过本发明的方法可以获得真实扰动应力路径下的煤岩体力学参数。
5.通过本发明的测试方法可以获得距离采面不同距离超前支承压力分布、试样应力-应变曲线、试样弹性模量及泊松比等岩石力学参数、应力-渗透率关系曲线等，为瓦斯抽采钻孔位置的确定、支护强度(超前支护、锚杆锚索布置的间排距等)的调节、岩石原位力学理论的 研究等提供了试验手段。
6.通过本发明的测试方法可以获得煤岩采动应力变化与渗流特性，获得煤层所处地质环境中原位扰动力学性质，能够为采动岩体力学理论及原位扰动岩体力学提供试验方法，为煤与瓦斯共采工程中的煤层增透效果评价提供新的思路，为煤矿安全生产提供更准确的参考数据。
附图说明
图1是本发明所述测试系统的结构示意图；
图2是测试组件及其在掏槽中的安装示意图；
图3是加载头的结构示意图；
图4是掏槽在煤岩体上的布置示意图，图中箭头是指采面推进方向；
图中，1—气源、2—真空泵，3—测试组件、4—地面监控站、5—顶部压板、6—加载件、6-1—加载头、7—试件、8—底部压板、9—锚索应力计、10—扁千斤顶、11—气体隔离腔、12—密封圈、13—导气通孔、14—线缆通孔、15—掏槽、16—轴向位移计、17—径向位移计、18—位移采集器、19—应力采集器、20—井下信息采集站、21—第一减压阀、22—第二减压阀、23—第一阀门、24—第二阀门、25—第三阀门、26—第四阀门、27—第一流量计、28—第二流量计、29—第一压力传感器、30—第二压力传感器。
具体实施方式
以下通过实施例并结合附图对本发明提供的真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法及系统作进一步说明。有必要指出，以下实施例只用于对本发明作进一步说明，不能理解为对本发明保护范围的限制，所属领域技术人员根据上述发明内容，对本发明做出一些非本质的改进和调整进行具体实施，仍属于发明保护的范围。
下述各实施例中，采用的扁千斤顶为带压力表的扁千斤顶；采用的锚索应力计为山东恒安电子科技有限公司生产的GPD450M型矿用本安型锚杆(索)应力传感器，安标编号：MFB130447，该应力采集器自带压力采集装置，主要用于测量锚杆(索)应力变化，可用于本发明中的压力测量与压力信号自动记录；采用的轴向位移计为美国Epsilon 3542型轴向引伸计，适用于轴向拉伸、压缩的变形测量，在本发明中用于测量试件的轴向拉伸、压缩变形，采用的径向位移计为美国Epsilon3544型圆周引伸计，适用于径向的变形测量，在本发明中用于测量试件的径向变形；采用的位移采集器是可以用于采集和记录位移信号的仪器，例如可以是数字信号调节器。
井下信息采集站是把与之相连的设备采集到的信号传输给地面监控站，并把地面监控站 发出的指令传输给与之相连的部件的设备。具体地，井下信息采集站是把与之相连的第一压力传感器、第二压力传感器、位移采集器、应力采集器、第一流量计、第二流量计采集到的信号传输给地面监控站，并把地面监控站发出的指令传输给与之相连的第一减压阀、第二减压阀、第一阀门、第二阀门、第三阀门、第四阀门和真空泵的设备。以下实施例中，井下信息采集站具体是指井下环网交换机，通过将测试系统的控制总线与信息传输总线整合，将电缆接至井下环网交换机(例如，KJJ127矿用隔爆兼本安型网络交换机)上，KJJ127矿用隔爆兼本安型网络交换机允许安装在煤矿井下有煤尘和瓦斯爆炸的危险气体环境中，用来使井下可连接到交换机的设备与地面进行数据交换，实现远程控制和远程监测。地面监控站中的地面监控计算机就可以对井下连接到交换机的设备进行管理，通过交换机实现网络计算机对井下相关设备获取数据信息和控制管理的工作。
实施例1
本实施例中，真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统的结构示意图如图1所示，包括气源1、真空泵2、测试组件3、信号采集传输组件和地面监控站4。
所述测试组件3的测试组件及其在掏槽中的安装示意图如图2所示，包括顶部压板5、加载件6、试件7、底部压板8、锚索应力计9、扁千斤顶10、轴向位移计、径向位移计和气体隔离腔11。顶部压板5和底部压板8为形状相同的正方形钢板，气体隔离腔11为圆筒体，加载件的结构示意图如图3所示，加载件6由圆柱形的本体和本体一端的圆柱形的加载头6-1组成，加载头的外径与气体隔离腔的内径匹配，加载头上设有密封圈12，加载件上设有开口于加载头端面和本体侧壁的导气通孔13，底部压板上设有导气通孔13和线缆通孔14，试件7呈圆柱形，试件表面由塑料膜包裹密封，试件由从采面采集的煤岩体加工而成。顶部压板和底部压板边长为300mm的正方形钢板，厚度根据现场实际情况确定，为方便安装，可做1～3层。扁千斤顶的活塞杆的直径大于锚索应力计的应力探头的直径，底部压板的尺寸大于锚索应力计的应力探头的尺寸，顶部压板和底部压板的边长大于试件气体隔离腔的外径。
所述测试组件3安装于设置在采面前方200米的煤岩体上的掏槽15中，掏槽由相互连通的外槽和内槽组成，外槽呈拱形结构，内槽呈长方体结构，掏槽的内槽中从下到上依次安装扁千斤顶10、锚索应力计9、底部压板8、试件7、加载件6和顶部压板5，扁千斤顶10和顶部压板5分别与掏槽内槽的底面和顶面接触，掏槽内槽的底面和顶面为水平面，气体隔离腔11的下端通过螺栓固定在底部压板8上；扁千斤顶的活塞杆、锚索应力计的应力探头、底部压板上的导气通孔、试件以及加载件的轴线位于同一直线上，顶部压板的中心和底部压板的中心与试件的轴线在同一直线上。
气体隔离腔的下端与底部压板之间设有密封件，与加载件上的密封圈配合增加气体隔离腔的密闭性，试件7竖放于气体隔离腔11中，加载头6-1的端面与试件7的顶部接触并位于气体隔离腔11中，轴向位移计16和径向位移计17均安装在试件7上，轴向位移计16和径向位移计17的线缆穿过底部压板上的线缆通孔14引出气体隔离腔，底部压板上的线缆通孔与穿过该线缆通孔的线缆之间设有密封件，以增加气体隔离腔的密闭性。
所述信号采集传输组件包括位移采集器18、应力采集器19和井下信息采集站20，应力采集器19与锚索应力计9连接，位移采集器18分别与轴向位移计16和径向位移计17连接，位移采集器18和应力采集器19通过线缆与井下信息采集站20相连；所述地面监控站4包括地面监控计算机。
气源1经进气管路与气体隔离腔11连通，气体隔离腔11经底部压板8上的导气通孔13与出气管路连通，气源1经第一减压阀21分别与第一阀门23和第二阀门24的一端连接，第一阀门23的另一端与真空泵连接2，第二阀门24的另一端经第二减压阀22、第一流量计27与加载件6上的导气通孔13连通，在第一流量计27与加载件6之间的管路上设有第一压力传感器29，进气管路上设有连通第二减压阀22两端的支管路，支管路上设有第三阀门25；底部压板上的导气通孔13经第四阀门26与第二流量计28连接，第二流量计28之后的管路上设有第二压力传感器30；第一压力传感器29、第二压力传感器30、第一流量计27和第二流量计28通过线缆与井下信息采集站20连接，井下信息采集站20通过线缆与地面监控计算机连接。
第一减压阀、第二减压阀为电动减压阀，第一阀门、第二阀门、第三阀门和第四阀门为电动球阀，第一减压阀、第二减压阀、第一阀门、第二阀门、第三阀门以及第四阀门均通过线缆与地面监控计算机连接，通过地面监控计算机远程控制开启与关闭。真空泵通过线缆与地面监控计算机连接，通过地面监控计算机远程控制真空泵处于运行或停止运行的状态。
实施例2
本实施例在实施例1提供的测试系统的基础上，提供真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法，包括以下步骤：
①从山西省同煤国电同忻煤矿北三盘区8309综放工作面(地表以下600m)取芯，取芯后做好减震包装，送至地面加工成标准试件。该工作面的煤层硫分(St,d)平均值在2.22％～2.39％之间，为中高硫煤，低磷、挥发分较高、发热量较高，以半暗型煤为主，沥青光泽，致密块状，部分具线理状结构，夹有镜煤和亮煤细条带，含有星散状黄铁矿结核，各煤层煤的真密度一般在1.6kg/L左右，视密度一般为1.45kg/L。根据国家标准《煤和岩石物 理力学性质测定方法》中的有关规定，加工成直径50±2mm，高径比为2±0.2的试件，试件两端面不平行度不大于0.05mm，试件上下端直径偏差不大于0.3mm，试件表面光滑，避免因不规则表面而产生的应力集中现象，试件加工好之后用塑料膜包裹密封。
②在采面前方200m、距离底板1.5m处的采面轨道巷的采煤帮上开挖掏槽，先开挖一个尺寸约为高800mm×宽600mm的拱形结构的外槽，在外槽的基础上继续向煤岩体内壁开挖一个长方体形的内槽，内槽高600mm、宽500mm、深500mm，掏槽开挖完成后，对掏槽的壁面进行打磨，使其无明显棱角，特别是装载测试组件的部位，然后将掏槽的底面、掏槽内槽顶面用水泥糊成水平面，晾至水泥完全凝结。
③在掏槽的内槽中安装测试组件，将加载件的导气通孔与进气管路连通，将底部压板上的导气通孔与出气管路连通。
④用扁千斤顶对试件加载至初始应力状态(即当地垂向应力值，如果没有地应力测量值，则根据σ＝γz进行估算)，本实施例中采用扁千斤顶对试件加载至15MPa，扁千斤顶带有压力表，加载初始压力后，记录一次读数，封死阀门，以防卸压，每隔一段时间观测一次该压力表的读数变化，如果发现压力降低应及时补充至初始压力状态。关闭第四阀门、第一减压阀和第二减压阀，打开第一阀门、第二阀门和第三阀门，开启真空泵抽真空30min，将管路及气体隔离腔中的气体抽出，然后关闭第一阀门、第三阀门、第四阀门，之后关闭真空泵，打开第一减压阀和第二减压阀向气体隔离腔中通入SF 6气体对试件施加2MPa的围压，在通入SF 6的过程中调节第四阀门以保持该围压条件。第一减压阀、第二减压阀、第一阀门、第二阀门以及第四阀门均通过地面监控站的监控计算机远程控制开启与关闭。
⑤在采动过程中进行测试，通过应力采集器和位移采集器实时采集应力、轴向位移计与径向位移数据，实时传输给地面监控站并记录；在采动过程中，根据测试需要可通过地面监控站的地面监控计算机远程调整第一减压阀、第二阀门、第二减压阀及第四阀门的开启程度来调整围压。
待采面推至掏槽位置时，试件发生变形破坏，测试过程结束。
⑥通过分析步骤⑤采集的数据，获得真实采动应力影响下煤岩体的力学行为和渗流特性数据。
以根据步骤⑤中采集的数据计算获取不同时刻的渗透率为例，说明本发明获取真实采动应力影响下煤岩体的渗流特性数据的方法。假设整个测试过程为等温过程，并满足理想气体状态方程，根据可压缩气体水平线性稳定渗流达西公式，可以计算不同时刻的渗透率，如下：
Figure PCTCN2019078443-appb-000001
上式中，K为渗透率，m 2；q为SF 6气体的流量，m 3/s；p 0为试验地点的大气压，以当地实测为准；μ为SF 6在试验温度时的粘度系数；A为试件的横截面积，m 2；L为试件的长度，m；p 1、p 2分别为第一压力传感器和第二压力传感器测得的压力，MPa。

Claims (10)

  1. 真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，包括气源(1)、真空泵(2)，其特征在于，还包括测试组件(3)、信号采集传输组件和地面监控站(4)，
    所述测试组件(3)包括顶部压板(5)、加载件(6)、试件(7)、底部压板(8)、锚索应力计(9)、扁千斤顶(10)、轴向位移计(16)、径向位移计(17)和气体隔离腔(11)，气体隔离腔(11)为圆筒体，加载件(6)的一端为圆柱形的加载头(6-1)，加载头的外径与气体隔离腔的内径匹配，加载头上设有密封圈(12)，加载件上设有开口于加载头端面和加载件侧壁的导气通孔(13)，底部压板上设有导气通孔(13)和线缆通孔(14)；
    所述测试组件(3)安装于设置在采面前方的煤岩体上的掏槽(15)中，掏槽中从下到上依次安装扁千斤顶(10)、锚索应力计(9)、底部压板(8)、试件(7)、加载件(6)和顶部压板(5)，扁千斤顶(10)和顶部压板(5)分别与掏槽的底面和顶面接触，掏槽与扁千斤顶和顶部压板接触的部位为水平面，气体隔离腔(11)的下端固定在底部压板(8)上，试件(7)竖放于气体隔离腔(11)中，加载头(6-1)的端面与试件(7)的顶部接触并位于气体隔离腔(11)中，轴向位移计(16)和径向位移计(17)均安装在试件(7)上，轴向位移计(16)和径向位移计(17)的线缆穿过底部压板上的线缆通孔(14)引出气体隔离腔；
    所述信号采集传输组件包括位移采集器(18)、应力采集器(19)和井下信息采集站(20)，应力采集器(19)与锚索应力计(9)连接，位移采集器(18)分别与轴向位移计(16)和径向位移计(17)连接，位移采集器(18)和应力采集器(19)通过线缆与井下信息采集站(20)相连；所述地面监控站(4)包括地面监控计算机；
    气源(1)经进气管路与气体隔离腔(11)连通，气体隔离腔(11)经底部压板(8)上的导气通孔(13)与出气管路连通，气源(1)经第一减压阀(21)分别与第一阀门(23)和第二阀门(24)的一端连接，第一阀门(23)的另一端与真空泵连接(2)，第二阀门(24)的另一端经第二减压阀(22)、第一流量计(27)与加载件(6)上的导气通孔(13)连通，在第一流量计(27)与加载件(6)之间的管路上设有第一压力传感器(29)，进气管路上设有连通第二减压阀(22)两端的支管路，支管路上设有第三阀门(25)；底部压板上的导气通孔(13)经第四阀门(26)与第二流量计(28)连接，第二流量计(28)之后的管路上设有第二压力传感器(30)；第一压力传感器(29)、第二压力传感器(30)、第一流量计(27)和第二流量计(28)通过线缆与井下信息采集站(20)连接，井下信息采集站(20)通过线缆与地面监控计算机连接。
  2. 根据权利要求1所述真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，其特征在于，扁千斤顶的活塞杆、锚索应力计的应力探头、底部压板上的导气通孔、试件以及加载件的轴线位于同一直线上。
  3. 根据权利要求2所述真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，其特征在于，扁千斤顶的活塞杆的直径大于锚索应力计的应力探头的直径，底部压板的尺寸大于锚索应力计的应力探头的尺寸，顶部压板和底部压板的尺寸大于气体隔离腔的外径。
  4. 根据权利要求1至3中任一项权利要求所述真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，其特征在于，试件呈圆柱形，试件表面由塑料膜包裹密封，试件由从采面采集的煤岩体加工而成。
  5. 根据权利要求1至3中任一项权利要求所述真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，其特征在于，掏槽位于采面前方至少200m。
  6. 根据权利要求1至3中任一项权利要求所述真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，其特征在于，气体隔离腔的下端与底部压板之间设有密封件。
  7. 根据权利要求1至3中任一项权利要求所述真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，其特征在于，底部压板上的线缆通孔与穿过该线缆通孔的线缆之间设有密封件。
  8. 根据权利要求1至3中任一项权利要求所述真实采动应力影响下煤岩体的力学行为和 渗流特性原位测试系统，其特征在于，第一减压阀、第二减压阀为电动减压阀，第一阀门、第二阀门、第三阀门和第四阀门为电动球阀，第一减压阀、第二减压阀、第一阀门、第二阀门、第三阀门以及第四阀门均通过线缆与地面监控计算机连接，通过地面监控计算机远程控制开启与关闭。
  9. 根据权利要求8所述真实采动应力影响下煤岩体的力学行为和渗流特性原位测试系统，其特征在于，真空泵通过线缆与地面监控计算机连接，通过地面监控计算机远程控制真空泵处于运行或停止运行的状态。
  10. 真实采动应力影响下煤岩体的力学行为和渗流特性原位测试方法，其特征在于该方法在使用权利要求1至9之一所述测试系统的基础上进行测试，包括以下步骤：
    ①从采面现场取芯制作试件，将试件表面用塑料膜包裹密封；
    ②在采面前方至少200m的采面轨道巷的采煤帮上开挖掏槽，将掏槽的顶面和底面用水泥糊成水平面，晾至水泥凝结；
    ③在掏槽中安装测试组件，将加载件的导气通孔与进气管路连通，将底部压板上的导气通孔与出气管路连通；
    ④用扁千斤顶对试件加载至初始应力状态并在后续测试过程中通过调整扁千斤顶使试件始终处于初始应力状态；关闭第四阀门、第一减压阀和第二减压阀，打开第一阀门、第二阀门和第三阀门，开启真空泵将管路及气体隔离腔中的气体抽出，然后关闭第一阀门、第三阀门、第四阀门，之后关闭真空泵，打开第一减压阀和第二减压阀向气体隔离腔中通入SF 6气体对试件施加围压，在通入SF 6气体的过程中调节第四阀门以保持围压条件；
    ⑤在采动过程中进行测试，通过应力采集器和位移采集器实时采集应力、轴向位移计与径向位移数据，实时传输给地面监控站并记录；
    ⑥通过分析步骤⑤采集的数据，获得真实采动应力影响下煤岩体的力学行为和渗流特性数据。
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