一种煤岩样品液氮循环冻融增透模拟试验系统及方法System and method for simulating test of liquid nitrogen sample freeze-thaw and anti-penetration of coal rock sample
技术领域Technical field
本发明涉及一种冻融试验系统及方法,尤其是一种煤岩样品液氮循环冻融增透模拟试验系统及方法。The invention relates to a freeze-thaw test system and method, in particular to a liquid nitrogen sample liquid nitrogen circulation freeze-thaw anti-reflection simulation test system and method.
背景技术Background technique
据统计,我国高瓦斯矿井和有瓦斯突出危险的矿井占到了全国矿井总数量的30%左右,而重、特大恶性瓦斯事故的高发生频率并没有得到根本性的解决,这将严重阻碍着未来我国煤矿安全生产工作的顺利进行。因此,煤矿瓦斯抽采工作,势在必行。但我国煤层多为高瓦斯低透气性煤层,瓦斯抽采难度大,瓦斯抽采浓度较低,大部分低于20%。目前多采用水力压裂、水力割缝和预裂爆破等方法来增大煤层透气性,随着矿井深度和开采强度的不断增加,常规煤层增透抽采瓦斯方法致裂增透范围小,煤体无法形成大范围瓦斯抽采裂隙网,使得瓦斯抽采率低,瓦斯治理效果不理想。提出一种高效增透煤层抽采瓦斯方法是加快破解深部煤炭开采灾害防治的重点。According to statistics, China's high gas mines and mines with dangerous gas outbursts account for about 30% of the total number of mines in the country, and the high frequency of heavy and extremely malignant gas accidents has not been fundamentally resolved, which will seriously hinder the future. The safe production of coal mines in China has been carried out smoothly. Therefore, coal mine gas drainage work is imperative. However, most of China's coal seams are high-gas and low-breathing coal seams. Gas drainage is difficult, and gas drainage concentration is low, most of which is less than 20%. At present, hydraulic fracturing, hydraulic slitting and pre-cracking blasting are used to increase the permeability of coal seams. With the increasing depth and mining strength of conventional coal seams, the conventional coal seam gasification and gas extraction method has a small range of cracking and permeability, coal The body cannot form a large-scale gas drainage crack network, which makes the gas extraction rate low and the gas control effect is not ideal. It is proposed that a method for efficiently extracting gas from coal seams is the key to speeding up the prevention and control of deep coal mining disasters.
冻融现象是自然界中一种常见的物理地质作用和现象,尤其出现在温差变化比较大的物体构造中,如青藏高原、北方地区的公路和建筑物。冻融侵蚀是由于土壤及其母质孔隙中或岩石裂缝中的水分在冻结时,体积膨胀,使裂隙随之加大、增多所导致整块土体或岩石发生碎裂,消融后其抗蚀稳定性大为降低,在重力作用下岩土顺坡向下方产生位移的现象。结构件表面和内部所含水分的冻结和融化的交替出现,称为冻融循环。冻融循环的反复出现,造成物体构造的严重破坏。Freezing and thawing is a common physical geological phenomenon and phenomenon in nature, especially in the construction of objects with relatively large temperature differences, such as highways and buildings in the Qinghai-Tibet Plateau and the northern region. Freeze-thaw erosion is caused by the volume expansion of the water in the pores of the soil and its parent material or in the cracks of the rock. As the crack increases and increases, the whole soil or rock breaks up. The corrosion resistance is stabilized after ablation. The nature is greatly reduced, and the displacement of the rock and soil along the slope is caused by gravity. The alternating freezing and thawing of the moisture content on the surface of the structural member and the interior is called a freeze-thaw cycle. The recurrence of the freeze-thaw cycle causes serious damage to the structure of the object.
在常压下,液氮温度可达-196℃,汽化潜热为5.56kJ/mol,1m3的液氮可以膨胀为696m3的21℃纯气态氮,汽化时可吸收周围大量热量。液氮具有制备简单、原料来源广泛等优点,在煤体冻融循环中液氮可作为一种高效的制冷和增透介质。At atmospheric pressure, liquid nitrogen temperature up to -196 deg.] C, latent heat of vaporization 5.56kJ / mol, liquid nitrogen may be expanded in 1m 3 of pure gaseous nitrogen 21 ℃ 696m3 can absorb a large amount of heat around the vaporization. Liquid nitrogen has the advantages of simple preparation and wide source of raw materials. Liquid nitrogen can be used as an efficient refrigeration and anti-reflection medium in the freezing and thawing cycle of coal.
针对目前抽采瓦斯技术的不足,可以通过液氮的相变对煤层进行循环冻融致裂,为高瓦斯煤层提供一种更加高效的煤层增透方法,提出一种基于水平定向钻孔液氮循环冻融增透煤层抽采瓦斯方法,煤体在水相变冻胀力、液氮气化膨胀力以及微孔液体流动渗透压共同作用下,促使低渗透煤层中宏观裂隙和微观裂隙扩展联通,沟通瓦斯抽采裂隙网,增加煤层透气性。由于液氮循环冻融增透煤层抽采瓦斯方法受诸多因素影响,如何在实验室进行各种影响因素对煤岩体增透的规律的研究,为液氮循环冻融增透煤层抽采瓦斯工程应用提供科学依据和理论基础,以及确定各影响变量的最佳值是目前亟待解决的科学问题。In view of the shortcomings of the current gas extraction technology, the coal seam can be subjected to cyclic freeze-thaw cracking through the phase transition of liquid nitrogen, which provides a more efficient coal seam anti-filtration method for high gas coal seams, and proposes a horizontally oriented drilling liquid nitrogen. The method of extracting gas by circulating freeze-thaw and anti-permeability coal seam, the coal body promotes the expansion of macro-fracture and micro-crack in low-permeability coal seam under the action of water-phase freezing and expansion force, liquid nitrogenizing expansion force and microporous liquid flow osmotic pressure. Communicate the gas to extract the fracture network and increase the permeability of the coal seam. Due to the influence of many factors on the liquid-nitrogen cycle freeze-thaw and coal-enriched coal seam gas drainage, how to study the law of various factors affecting the permeability of coal and rock mass in the laboratory, for the liquid nitrogen circulation freeze-thaw hardening coal seam gas extraction The scientific basis and theoretical basis of engineering application, as well as the determination of the optimal value of each influencing variable are the scientific problems that need to be solved urgently.
发明内容Summary of the invention
发明目的:本发明的目的是提供一种煤岩样品液氮循环冻融增透模拟试验系统及方
法,旨在为液氮循环冻融增透煤层抽采瓦斯的工程应用提供科学依据和理论基础。OBJECT OF THE INVENTION: The object of the present invention is to provide a simulation test system for liquid nitrogen circulation freeze-thaw and anti-reflection of coal rock samples and a square
The law aims to provide scientific basis and theoretical basis for the engineering application of liquid nitrogen circulation freeze-thaw and coal seam gas extraction.
为了实现上述目的,本发明采用了如下的技术方案:一种煤岩样品液氮循环冻融增透模拟试验系统,包括冻融装置、数据采集系统和煤岩样品,所述冻融装置包括液氮冻融试验箱和自增压液氮罐,煤岩样品放置在液氮冻融试验箱内,液氮冻融试验箱内设有加热器和液位传感器,加热器通过温控器连接线连接温度控制器,温度控制器连接计算机,液位传感器与设置在液氮冻融试验箱外侧的液位显示器连接,液氮冻融试验箱顶部设有液氮冻融试验箱密封盖,液氮冻融试验箱密封盖上设有安全泄压阀、低温压力表和排空阀,液氮冻融试验箱底部通过液氮供给管路连接自增压液氮罐;In order to achieve the above object, the present invention adopts the following technical solution: a coal-rock sample liquid nitrogen circulation freeze-thaw anti-reflection simulation test system, including a freeze-thaw device, a data acquisition system and a coal rock sample, the freeze-thaw device including liquid Nitrogen freeze-thaw test chamber and self-pressurized liquid nitrogen tank. The coal rock sample is placed in the liquid nitrogen freeze-thaw test chamber. The liquid nitrogen freeze-thaw test chamber is equipped with a heater and a liquid level sensor. The heater passes through the thermostat connection line. The temperature controller is connected, the temperature controller is connected to the computer, the liquid level sensor is connected with the liquid level display disposed outside the liquid nitrogen freezing and thawing test box, and the liquid nitrogen freezing and thawing test box is provided with a liquid nitrogen freezing and thawing test box sealing cover, liquid nitrogen The safety and pressure relief valve, the low temperature pressure gauge and the emptying valve are arranged on the sealing cover of the freezing and thawing test box, and the bottom of the liquid nitrogen freezing and thawing test box is connected to the pressurized liquid nitrogen tank through the liquid nitrogen supply pipeline;
所述液氮供给管路包括三通接头,三通接头第一端连接液氮冻融试验箱底部,三通接头第二端设有进液阀/排液阀,三通接头第三端设有增压阀,自增压液氮罐设有液氮罐截止阀,液氮罐截止阀通过耐低温金属软管连接进液阀/排液阀,在液氮冻融试验箱外侧设有液氮增压管,液氮增压管上端与液氮冻融试验箱内部连通,液氮增压管下端连接增压阀;The liquid nitrogen supply pipeline includes a three-way joint, the first end of the three-way joint is connected to the bottom of the liquid nitrogen freeze-thaw test chamber, the second end of the three-way joint is provided with an inlet valve/drain valve, and the third end of the three-way joint is provided. There is a pressure increasing valve, the self-pressurizing liquid nitrogen tank is provided with a liquid nitrogen tank shut-off valve, and the liquid nitrogen tank shut-off valve is connected to the liquid inlet valve/drain valve through a low-temperature resistant metal hose, and is provided on the outside of the liquid nitrogen freezing and thawing test box. a nitrogen booster tube, the upper end of the liquid nitrogen booster tube is connected to the inside of the liquid nitrogen freezing and thawing test chamber, and the lower end of the liquid nitrogen booster tube is connected to the pressure increasing valve;
所述数据采集系统包括高频压力传感器、低温应变片和温度传感器探头,低温应变片和温度传感器探头分别布置在煤岩样品不同位置,低温应变片通过应变仪连接线连接应变仪,温度传感器探头通过温度传感器连接线连接温度传感器,应变仪和温度传感器均连接计算机,高频压力传感器布置在液氮冻融试验箱内侧,高频压力传感器通过USB数据线连接计算机。The data acquisition system comprises a high frequency pressure sensor, a low temperature strain gauge and a temperature sensor probe, wherein the low temperature strain gauge and the temperature sensor probe are respectively arranged at different positions of the coal rock sample, and the low temperature strain gauge is connected to the strain gauge through the strain gauge connection line, and the temperature sensor probe The temperature sensor is connected through a temperature sensor cable. The strain gauge and the temperature sensor are connected to the computer. The high frequency pressure sensor is arranged inside the liquid nitrogen freeze-thaw test chamber, and the high frequency pressure sensor is connected to the computer through the USB data line.
进一步的,所述液氮冻融试验箱密封盖一侧通过铰链与液氮冻融试验箱连接,液氮冻融试验箱密封盖另一侧设有密封盖把手和紧固螺栓,在液氮冻融试验箱密封盖底面与液氮冻融试验箱顶部相对应的位置设有密封槽。Further, one side of the sealing cover of the liquid nitrogen freeze-thaw test chamber is connected with a liquid nitrogen freeze-thaw test chamber through a hinge, and the seal cover handle and the fastening bolt are provided on the other side of the liquid nitrogen freeze-thaw test box seal cover in liquid nitrogen. The bottom surface of the sealing cover of the freeze-thaw test chamber is provided with a sealing groove at a position corresponding to the top of the liquid nitrogen freezing and thawing test box.
进一步的,所述液氮冻融试验箱含有聚氨酯绝热层。Further, the liquid nitrogen freeze-thaw test chamber contains a polyurethane insulation layer.
本发明的煤岩样品液氮循环冻融增透模拟试验方法:液氮冻融试验中,首先打开进液阀/排液阀和液氮罐截止阀,液氮由耐低温金属软管注入液氮冻融试验箱,通过液位显示器控制注入液氮量,当冻融冻融试验箱内压力超过额定压力时,安全泄压阀自动泄压,保证试验的安全性,煤岩样品在液氮中冻结一定时间后,打开进液阀/排液阀排出液氮,由温度控制器设定融化温度后经过加热器加热,煤岩样品开始融化,完成一次液氮冻融循环;随后多次重复上述液氮冻融循环,考察不同冻融变量条件下对煤岩样品的应变和温度影响规律,试验数据记录在计算机内处理分析。The coal-rock sample of the invention is subjected to a liquid-nitrogen cycle freeze-thaw anti-reflection simulation test method: in the liquid nitrogen freeze-thaw test, the liquid inlet valve/drain valve and the liquid nitrogen tank shut-off valve are first opened, and the liquid nitrogen is injected from the low-temperature resistant metal hose. The nitrogen freeze-thaw test chamber controls the injection of liquid nitrogen through the liquid level display. When the pressure in the freeze-thaw freeze-thaw test chamber exceeds the rated pressure, the safety relief valve automatically relieves pressure to ensure the safety of the test. The coal and rock samples are in liquid nitrogen. After freezing for a certain period of time, open the inlet valve/drain valve to discharge liquid nitrogen. After the melting temperature is set by the temperature controller and then heated by the heater, the coal rock sample begins to melt and complete a liquid nitrogen freeze-thaw cycle; The above-mentioned liquid nitrogen freeze-thaw cycles were used to investigate the effects of different freeze-thaw variables on the strain and temperature of coal-rock samples. The test data were recorded and analyzed in a computer.
进一步的,在考察不同冻融变量条件下对煤岩样品的应变和温度影响规律时,首先通过设置不同液氮冻结时间、不同融化温度、不同样品含水率、不同液氮膨胀压和不同循环次数,以获取多个不同冻融变量下增透致裂的煤岩样品,然后把各个煤岩样品进行编号,通过三轴/单轴压缩试验及扭剪试验测得各个煤岩样品的力学特征变化规律,通过
核磁共振技术、超声波技术、声发射技术、电镜扫描技术、CT扫描技术测试各个煤岩样品的岩体孔隙特征和微观形态变化规律,最后通过对各个煤岩样品的力学特征变化规律、岩体孔隙特征和微观形态变化规律定量分析,找出最佳的液氮冻结时间和融化温度以及样品含水率和液氮冻融循环次数对液氮冻融增透煤岩体过程中的影响规律。Further, when investigating the influence of different freeze-thaw variables on the strain and temperature of coal-rock samples, firstly set different liquid nitrogen freezing times, different melting temperatures, different sample moisture contents, different liquid nitrogen expansion pressures and different cycle times. In order to obtain the samples of coal and rock that have been cracked and cracked under different freezing and thawing variables, then each coal rock sample is numbered, and the mechanical characteristics of each coal rock sample are measured by triaxial/uniaxial compression test and torsional shear test. Law, through
Nuclear magnetic resonance technology, ultrasonic technology, acoustic emission technology, electron microscopy scanning technology and CT scanning technology were used to test the pore characteristics and microscopic morphology of rock mass samples. Finally, the mechanical characteristics of rock samples were analyzed. Quantitative analysis of characteristics and micromorphological changes, to find out the optimal liquid nitrogen freezing time and melting temperature and the influence of sample moisture content and liquid nitrogen freezing and thawing cycles on the process of liquid nitrogen freezing and thawing to enhance the permeability of coal and rock mass.
进一步的,试验过程中,液氮冻融试验箱内液氮膨胀压力由增压阀、液氮增压管和低温压力表联合控制,控制过程如下:首先打开增压阀,液氮冻融试验箱内的液氮进入液氮增压管,液氮增压管为单层导热铜管,液氮在其中吸热急速膨胀汽化为氮气,氮气进入液氮冻融试验箱,由低温压力表显示压力值联合控制增压阀的开关,来控制液氮冻融试验箱内的液氮膨胀压,液氮冻融试验箱内液氮膨胀压力通过液氮施加在煤岩样品上,即试验过程中煤岩样品所受围压大小。Further, during the test, the liquid nitrogen expansion pressure in the liquid nitrogen freeze-thaw test chamber is jointly controlled by a pressure increasing valve, a liquid nitrogen booster tube and a low temperature pressure gauge, and the control process is as follows: firstly, the pressure increasing valve is opened, and the liquid nitrogen freeze-thaw test is performed. The liquid nitrogen in the tank enters the liquid nitrogen booster tube, and the liquid nitrogen booster tube is a single-layer heat-conducting copper tube. The liquid nitrogen rapidly expands and vaporizes into nitrogen gas, and the nitrogen enters the liquid nitrogen freeze-thaw test chamber, which is displayed by the low temperature pressure gauge. The pressure value jointly controls the switch of the booster valve to control the liquid nitrogen expansion pressure in the liquid nitrogen freeze-thaw test chamber, and the liquid nitrogen expansion pressure in the liquid nitrogen freeze-thaw test chamber is applied to the coal rock sample through liquid nitrogen, that is, during the test. The size of the surrounding pressure of the coal rock sample.
有益效果:本发明可模拟液氮循环冻融增透煤体或岩体的过程,为液氮循环冻融增透煤岩体抽采瓦斯或页岩气提供了一种可实现的实验平台,可定量研究液氮冻融增透煤岩体的基本参数,为现场液氮冻融实验提供科学依据和理论基础。Beneficial effects: The invention can simulate the process of liquid nitrogen circulation freeze-thaw to increase the permeability of coal or rock mass, and provides an achievable experimental platform for liquid nitrogen circulation freeze-thaw and anti-filtration of coal rock body to extract gas or shale gas. The basic parameters of liquid nitrogen freezing and thawing to enhance the permeability of coal and rock mass can be quantitatively studied, which provides scientific basis and theoretical basis for on-site liquid nitrogen freezing and thawing experiments.
附图说明DRAWINGS
图1是煤岩样品液氮循环冻融增透模拟试验系统示意图;Figure 1 is a schematic diagram of a liquid nitrogen sample circulating nitrogen-free freeze-thaw simulation test system;
图2是液氮冻融箱立体图;Figure 2 is a perspective view of a liquid nitrogen freeze-thaw box;
图3是煤岩样品液氮循环冻融增透模拟试验方法流程图。Fig. 3 is a flow chart of a simulation test method for liquid nitrogen circulation freeze-thaw and anti-filtration of coal rock samples.
图中:1-计算机,2-温度控制器,21-加热器,22-温控器连接线,3-高频压力传感器,31-USB数据线,4-应变仪,41-低温应变片,42-应变仪连接线,5-温度传感器,51-温度传感器探头,52-温度传感器连接线,6-液氮冻融试验箱,61-安全卸压阀,62-低温压力表,63-排空阀,64-冻融箱密封盖,65-密封槽,66-密封盖把手,67-紧固螺栓,68-液位显示器,69-液位传感器,610-液氮增压管,611-增压阀,612-三通接头,613-进液阀/排液阀,7-自增压液氮罐,71-液氮罐截止阀,72-耐低温金属软管,8-煤岩试样。In the picture: 1-computer, 2-temperature controller, 21-heater, 22-therm controller cable, 3-high frequency pressure sensor, 31-USB data cable, 4-strain gauge, 41-low temperature strain gauge, 42- strain gauge cable, 5-temperature sensor, 51-temperature sensor probe, 52-temperature sensor cable, 6-liquid nitrogen freeze-thaw test chamber, 61-safe pressure relief valve, 62-low temperature gauge, 63-row Air valve, 64-freeze box sealing cover, 65-sealing groove, 66-sealing cover handle, 67-tightening bolt, 68-level indicator, 69-level sensor, 610-liquid nitrogen booster tube, 611- Booster valve, 612-three-way joint, 613-inlet valve/drain valve, 7-self-pressurized liquid nitrogen tank, 71-liquid nitrogen tank shut-off valve, 72-low temperature resistant metal hose, 8-coal rock test kind.
具体实施方式:detailed description:
下面结合附图对本发明做更进一步的解释。The invention will be further explained below in conjunction with the drawings.
如图1和2所示,本发明的煤岩样品液氮循环冻融增透模拟试验系统包括冻融装置、数据采集系统和煤岩样品8。As shown in Figures 1 and 2, the liquid nitrogen cycle freeze-thaw anti-reflection simulation test system of the coal rock sample of the present invention comprises a freeze-thaw device, a data acquisition system and a coal rock sample 8.
所述冻融装置包括液氮冻融试验箱6和自增压液氮罐7,煤岩样品8放置在液氮冻融试验箱6内。所述液氮冻融试验箱6含有聚氨酯绝热层,液氮冻融试验箱6内有加热器21和液位传感器69,加热器21通过温控器连接线22连接温度控制器2,温度控制器2连接计算机1,液位传感器69与设置在液氮冻融试验箱6外侧的液位显示器68连接。The freeze-thaw device includes a liquid nitrogen freeze-thaw test chamber 6 and a self-pressurized liquid nitrogen tank 7, and the coal rock sample 8 is placed in the liquid nitrogen freeze-thaw test chamber 6. The liquid nitrogen freeze-thaw test chamber 6 contains a polyurethane insulation layer. The liquid nitrogen freeze-thaw test chamber 6 has a heater 21 and a liquid level sensor 69. The heater 21 is connected to the temperature controller 2 through a thermostat connection line 22, and the temperature control is performed. The device 2 is connected to the computer 1, and the liquid level sensor 69 is connected to a liquid level display 68 provided outside the liquid nitrogen freeze-thaw test chamber 6.
液氮冻融试验箱6顶部设有液氮冻融试验箱密封盖64,液氮冻融试验箱密封盖64
上设有安全泄压阀61、低温压力表62和排空阀63,液氮冻融试验箱密封盖64一侧通过铰链与液氮冻融试验箱6连接,液氮冻融试验箱密封盖64另一侧设有密封盖把手66和紧固螺栓67,在液氮冻融试验箱密封盖64底面与液氮冻融试验箱6顶部相对应的位置设有密封槽65。通过紧固螺栓67闭合液氮冻融试验箱密封盖64,通过密封槽65保证试验环境绝热性,当液氮冻融试验箱6内压力超过额定压力时,安全泄压阀61自动泄压,保证试验的安全性,当需要带压取样时,先打开排空阀63卸载氮气压力后,方可取出样品。The liquid nitrogen freezing and thawing test chamber 6 is provided with a liquid nitrogen freezing and thawing test box sealing cover 64, and a liquid nitrogen freezing and thawing test box sealing cover 64.
There is a safety pressure relief valve 61, a low temperature pressure gauge 62 and an emptying valve 63. The liquid nitrogen freezing and thawing test chamber sealing cover 64 is connected to the liquid nitrogen freezing and thawing test box 6 through a hinge, and the liquid nitrogen freezing and thawing test box sealing cover is provided. The other side of the 64 is provided with a sealing cover handle 66 and a fastening bolt 67, and a sealing groove 65 is provided at a position corresponding to the top of the liquid nitrogen freezing and thawing test chamber 6 on the bottom surface of the liquid nitrogen freezing and freezing test chamber sealing cover 64. The liquid nitrogen freeze-thaw test box sealing cover 64 is closed by the fastening bolt 67, and the test environment is insulated by the sealing groove 65. When the pressure in the liquid nitrogen freeze-thaw test chamber 6 exceeds the rated pressure, the safety pressure relief valve 61 automatically releases pressure. To ensure the safety of the test, when the pressure sampling is required, the venting valve 63 is first opened to unload the nitrogen pressure before the sample can be taken out.
液氮冻融试验箱6底部通过液氮供给管路连接自增压液氮罐7,所述液氮供给管路包括三通接头612,三通接头612第一端连接液氮冻融试验箱6底部,三通接头612第二端设有进液阀/排液阀613,三通接头612第三端设有增压阀611,自增压液氮罐设有液氮罐截止阀71,液氮罐截止阀71通过耐低温金属软管72连接进液阀/排液阀613,在液氮冻融试验箱6外侧设有液氮增压管610,液氮增压管610上端与液氮冻融试验箱6内部连通,液氮增压管610下端连接增压阀611。打开增压阀611后,液氮冻融试验箱6内部的液氮进入液氮增压管610与外界进行换热并产生汽化,汽化后的氮气进入液氮冻融试验箱6实施加压,由低温压力表62显示压力值联合控制增压阀611的开关,来控制液氮冻融试验箱6内的液氮膨胀压力,液氮冻融试验箱6内液氮膨胀压力通过液氮施加在煤岩样品8上,即试验过程中煤岩样品8所受围压大小。The bottom of the liquid nitrogen freeze-thaw test chamber 6 is connected to the pressurized liquid nitrogen tank 7 through a liquid nitrogen supply line, the liquid nitrogen supply line includes a three-way joint 612, and the first end of the three-way joint 612 is connected to the liquid nitrogen freeze-thaw test chamber. 6 at the bottom, a third end of the three-way joint 612 is provided with an inlet valve/drain valve 613, a third end of the three-way joint 612 is provided with a pressure increasing valve 611, and a self-pressurizing liquid nitrogen tank is provided with a liquid nitrogen tank shut-off valve 71. The liquid nitrogen tank shut-off valve 71 is connected to the inlet valve/drain valve 613 through the low-temperature resistant metal hose 72, and the liquid nitrogen booster tube 610 is disposed outside the liquid nitrogen freeze-thaw test chamber 6, and the upper end of the liquid nitrogen booster tube 610 is liquid. The nitrogen freeze-thaw test chamber 6 is internally connected, and the lower end of the liquid nitrogen booster tube 610 is connected to the pressure increasing valve 611. After the pressure increasing valve 611 is opened, the liquid nitrogen inside the liquid nitrogen freezing and thawing test chamber 6 enters the liquid nitrogen boosting tube 610 to exchange heat with the outside and vaporizes, and the vaporized nitrogen enters the liquid nitrogen freezing and thawing test chamber 6 to perform pressurization. The pressure value is combined with the switch of the pressure control valve 611 by the low temperature pressure gauge 62 to control the liquid nitrogen expansion pressure in the liquid nitrogen freeze-thaw test chamber 6, and the liquid nitrogen expansion pressure in the liquid nitrogen freeze-thaw test chamber 6 is applied through the liquid nitrogen. On the coal rock sample 8, the size of the surrounding pressure of the coal rock sample 8 during the test.
所述数据采集系统包括高频压力传感器3、低温应变片41和温度传感器探头51,低温应变片41和温度传感器探头51分别布置在煤岩样品8不同位置,低温应变片41通过应变仪连接线42连接应变仪4,温度传感器探头51通过温度传感器连接线52连接温度传感器5,应变仪4和温度传感器5均连接计算机1,高频压力传感器3布置在液氮冻融试验箱6内侧,高频压力传感器3通过USB数据线31连接计算机1。高频压力传感器3用于记录液氮冻融试验箱6内部压力变化,即煤岩样品8所受围压变化变化,应变仪4用于记录煤岩样品8在冻融循环过程中的横向和纵向应变的变化数据,温度传感器5用于记录煤岩样品8表面和内部温度变化的数据。The data acquisition system includes a high frequency pressure sensor 3, a low temperature strain gauge 41 and a temperature sensor probe 51. The low temperature strain gauge 41 and the temperature sensor probe 51 are respectively arranged at different positions of the coal rock sample 8, and the low temperature strain gauge 41 passes through the strain gauge connection line. 42 is connected to the strain gauge 4, the temperature sensor probe 51 is connected to the temperature sensor 5 through the temperature sensor connecting line 52, the strain gauge 4 and the temperature sensor 5 are connected to the computer 1, and the high frequency pressure sensor 3 is arranged inside the liquid nitrogen freezing and freezing test chamber 6, high The frequency pressure sensor 3 is connected to the computer 1 via a USB data line 31. The high-frequency pressure sensor 3 is used to record the internal pressure change of the liquid nitrogen freeze-thaw test chamber 6, that is, the variation of the confining pressure of the coal rock sample 8, and the strain gauge 4 is used to record the transverse direction of the coal rock sample 8 during the freeze-thaw cycle. The longitudinal strain change data, the temperature sensor 5 is used to record the data of the surface and internal temperature changes of the coal rock sample 8.
如图3所示,本发明的采用上述试验系统的煤岩样品液氮循环冻融增透模拟试验方法:液氮冻融试验中,首先打开进液阀/排液阀613和液氮罐截止阀71,液氮由耐低温金属软管72注入液氮冻融试验箱6,通过液位显示器68控制注入液氮量,试验过程中,液氮冻融试验箱6内液氮膨胀压力由增压阀611、液氮增压管610和低温压力表62联合控制,控制过程如下:首先打开增压阀611,液氮冻融试验箱6内的液氮进入液氮增压管610,液氮增压管610为单层导热铜管,液氮在其中吸热急速膨胀汽化为氮气,氮气进入液氮冻融试验箱6,由低温压力表62显示压力值联合控制增压阀611的开关,来控制液氮冻融试验箱6内的液氮膨胀压,液氮冻融试验箱6内液氮膨胀压力通过液氮施加在煤
岩样品8上,即试验过程中煤岩样品8所受围压大小。当冻融冻融试验箱6内压力超过额定压力时,安全泄压阀61自动泄压,保证试验的安全性,煤岩样品8在液氮中冻结一定时间后,打开进液阀/排液阀613排出液氮,由温度控制器2设定融化温度后经过加热器21加热,煤岩样品8开始融化,完成一次液氮冻融循环;随后多次重复上述液氮冻融循环,考察不同冻融变量条件下对煤岩样品8的应变和温度影响规律,试验数据记录在计算机1内处理分析。As shown in FIG. 3, in the coal rock sample using the above test system, the liquid nitrogen circulation freeze-thaw anti-reflection simulation test method: in the liquid nitrogen freeze-thaw test, firstly, the inlet valve/drain valve 613 and the liquid nitrogen tank are opened. The valve 71, the liquid nitrogen is injected into the liquid nitrogen freezing and thawing test chamber 6 by the low temperature resistant metal hose 72, and the liquid nitrogen amount is controlled by the liquid level display 68. During the test, the liquid nitrogen expansion pressure in the liquid nitrogen freezing and thawing test chamber 6 is increased. The pressure valve 611, the liquid nitrogen booster tube 610 and the low temperature pressure gauge 62 are jointly controlled. The control process is as follows: firstly, the pressure increasing valve 611 is opened, and the liquid nitrogen in the liquid nitrogen freezing and thawing test chamber 6 enters the liquid nitrogen boosting tube 610, liquid nitrogen. The booster tube 610 is a single-layer heat-conducting copper tube, in which the liquid nitrogen rapidly expands and vaporizes into nitrogen gas, and the nitrogen gas enters the liquid nitrogen freeze-thaw test chamber 6, and the low-temperature pressure gauge 62 displays the pressure value to jointly control the switch of the pressure-increasing valve 611. To control the liquid nitrogen expansion pressure in the liquid nitrogen freeze-thaw test chamber 6, the liquid nitrogen expansion pressure in the liquid nitrogen freeze-thaw test chamber 6 is applied to the coal through liquid nitrogen
On the rock sample 8, the size of the confining pressure of the coal rock sample 8 during the test. When the pressure in the freeze-thaw freeze-thaw test chamber 6 exceeds the rated pressure, the safety relief valve 61 automatically relieves pressure to ensure the safety of the test. After the coal rock sample 8 is frozen in the liquid nitrogen for a certain period of time, the inlet valve/discharge is opened. The valve 613 discharges the liquid nitrogen, and after the melting temperature is set by the temperature controller 2, it is heated by the heater 21, and the coal rock sample 8 starts to melt, and a liquid nitrogen freezing and thawing cycle is completed; then the liquid nitrogen freezing and thawing cycle is repeated several times to examine different The influence of the strain and temperature on the coal rock sample 8 under the condition of freezing and thawing variables, the test data was recorded and processed in the computer 1.
在考察不同冻融变量条件下对煤岩样品8的应变和温度影响规律时,首先通过设置不同液氮冻结时间、不同融化温度、不同含水率、不同液氮膨胀压和不同循环次数,以获取多个不同冻融变量下增透致裂的煤岩样品8,然后把各个煤岩样品8进行编号,通过三轴/单轴压缩试验及扭剪试验测得各个煤岩样品8的力学特征变化规律,通过核磁共振技术、超声波技术、声发射技术、电镜扫描技术、CT扫描技术测试各个煤岩样品8的岩体孔隙特征和微观形态变化规律,最后通过对各个煤岩样品8的力学特征变化规律、岩体孔隙特征和微观形态变化规律定量分析,找出最佳的液氮冻结时间和融化温度以及煤岩样品8含水率和液氮冻融循环次数对液氮冻融增透煤岩体过程中的影响规律。When investigating the influence of different freezing and thawing variables on the strain and temperature of coal rock sample 8, firstly, by setting different liquid nitrogen freezing time, different melting temperature, different water content, different liquid nitrogen expansion pressure and different cycle times, Several kinds of coal-rock samples 8 were obtained by different freeze-thaw variables, and then each coal sample 8 was numbered. The mechanical characteristics of each coal sample 8 were measured by triaxial/uniaxial compression test and torsional shear test. Regularity, the nuclear pore characteristics and microscopic morphology of each coal-rock sample 8 were tested by NMR, ultrasonic, acoustic emission, electron microscopy and CT scanning techniques. Finally, the mechanical characteristics of each coal sample 8 were changed. Quantitative analysis of regularity, pore characteristics and microscopic morphology of rock mass, find out the best freezing time and melting temperature of liquid nitrogen, and the moisture content of coal rock sample 8 and the number of freezing and thawing cycles of liquid nitrogen for liquid nitrogen freezing and thawing to strengthen coal rock mass The law of influence in the process.
以上所述仅是本发明的优选实施方式,应当指出,对于本技术领域的普通技术人员来说,在不脱离本发明原理的前提下,还可以做出若干改进和润饰,这些改进和润饰也应视为本发明的保护范围。
The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.