【作者】 王泽；

【导师】 康天合；

【作者基本信息】 太原理工大学 ， 资源与环境（专业学位）， 2024， 硕士

【摘要】 铁矿石作为我国的战略矿产资源,在国民经济发展中占据重要地位。由于其质地坚硬,无论采用常规钻爆法还是机械破碎法,其破碎效率都较低。因此,探讨其开采新技术、新理论就成为了振兴金属采矿业的必由之路。国内外学者发展了多种新兴方法,有激光破岩、高压泡沫、微波处理等。与其他方法相比,微波辅助机械破岩有高效、环保等优势。在近些年来,国内外学者对微波辅助破岩理论及技术的应用进行了研究,特别是针对坚硬岩石。证明了通过微波预处理弱化岩石的强度,可以显著提高破岩效率。本文以太钢集团袁家村露天铁矿的石英型赤铁矿石为研究对象,利用单模微波发生器组成的微波试验装置对赤铁矿石开展微波辐射及冷却方式试验,借助工业热成像仪、XRD衍射仪、工业显微CT、非金属探伤仪和声发射检测设备等手段,研究了微波辐射及不同冷却方式处理后的赤铁矿试样的升温速率、表面及内部裂隙扩展规律、力学特性及声发射特征等。论文主要的工作及取得的成果如下:(1)采用自行研制的单模微波辐射装置对赤铁矿石试样进行了微波辐射试验。具体试验方案为微波辐射功率为1、2、3 kW;辐射时间为1、2、3、4 min;将微波功率3 kW辐射时间3 min的试样进行自然冷却、泡水冷却、液氮冷却10 min、液氮冷却2 h四种冷却方式处理。采用红外成像仪对微波辐射后的试样进行了温度测定并拍摄其表面裂隙变化情况,分析了微波辐射对试样的表面温度变化情况及裂隙演化特征。结果表明,微波辐射后赤铁矿石试样出现了明显的热裂解现象,试样整体温度随微波辐射功率及辐射时间的增加而增大,呈线性增加的关系;试样温度越高的区域表面裂隙越发育。(2)采用CT检测技术对不同冷却方式处理后的试样的微裂隙演化情况进行了分析,并引入分形维数对不同冷却方式处理后的裂隙分布复杂度情况进行了定量表征,结果表明,随着冷却降温幅度的增大,试样的裂隙宽度、裂隙体积占比、裂隙分布复杂度的分形维数呈线性趋势增加。(3)采用非金属探伤仪对微波辐射及冷却方式处理后的试样纵波波速变化情况进行了分析,并将波速为损伤变量研究试样的损伤程度。结果表明,试样的纵波波速随微波辐射功率及辐射时间的增加下降明显,自然冷却、水冷却、液氮冷却10 min、液氮冷却2 h试样的波速分别下降了64.7%、73.9%、78.7%、83.9%,试样累计损伤因子分别为0.88、0.92、0.95、0.97。(4)通过对赤铁矿石试样进行常规力学试验,得到了其应力-应变曲线、抗压强度及抗拉强度与微波辐射参数及冷却方式之间的变化规律。得出试样的抗压强度、抗拉强度随辐射功率及时间的增加而下降,经泡水冷却、液氮冷却10 min、液氮冷却2h试样的抗压强度较自然冷却试样分别降低了12.4%、20.3%和25.6%,试样的抗拉强度较自然冷却试样分别降低了24.1%、61.2%、86.2%。(5)通过对赤铁矿试样单轴压缩试验过程进行声发射监测,微波辐射及冷却方式作用后试样会经历初始压密阶段、弹性变形阶段、裂纹稳定扩展阶段、裂纹剧烈发育阶段及破坏阶段,研究了各个阶段振铃撞击数以及全过程累计振铃数的变化关系,进一步揭示了微波辐射及冷却方式对赤铁矿石弱化效果的影响规律。得出试样的累计振铃数随着微波功率的增大而不断增长,单轴压缩时声发射信号的高频活动区大多集中在试样的峰值应力点处,经水和液氮两种冷却介质冷却处理后试样的声发射振铃数在各个阶段较自然冷却试样更为频繁。更多还原

【Abstract】 As a strategic mineral resource in China,iron ore occupies an important position in the development of the national economy.Due to its hard texture,its crushing efficiency is low regardless of whether it is a conventional drilling and blasting method or a mechanical crushing method.Therefore,it has become the only way to revitalize the metal mining industry by exploring new technologies and theories of mining.Scholars at home and abroad have developed a variety of emerging methods,including laser rock breaking,high-pressure foam,microwave processing,etc.Compared with other methods,microwave-assisted mechanical rock breaking has the advantages of high efficiency and environmental protection.In recent years,scholars at home and abroad have studied the application of microwave-assisted rock breaking theory and technology,especially for hard rock.It is proved that the strength of the weakened rock by microwave pretreatment can significantly improve the rock breaking efficiency.In this paper,the quartz-type hematite from the Yuanjiacun open-pit iron mine of TISCO Group was taken as the research object,and the microwave radiation and cooling method tests of the hematite were carried out by using a microwave test device composed of a single-mode microwave generator,and the heating rate,macro-microscopic fracture propagation law,mechanical properties and acoustic emission characteristics of the hematite samples treated with microwave radiation and different cooling methods were studied with the help of industrial thermal imager,XRD diffractometer,industrial micro-CT,non-metallic flaw detector and acoustic emission detection equipment.The main work and achievements of the paper are as follows:(1)A self-developed single-mode microwave radiation device was used to conduct microwave radiation tests on hematite samples.The specific experimental plan is for microwave radiation power of 1,2,and 3 kW;Radiation time is 1,2,3,and 4 minutes;The sample with a microwave power of 3 kW and a radiation time of 3 minutes was subjected to four cooling methods:natural cooling,water immersion cooling,liquid nitrogen cooling for10 minutes,and liquid nitrogen cooling for 2 hours.The temperature of the sample after microwave radiation was measured using an infrared imaging instrument,and the surface crack changes were photographed.The surface temperature changes and crack evolution characteristics of the sample under microwave radiation were analyzed.The results showed that there was a significant thermal cracking phenomenon in the hematite sample after microwave radiation,and the overall temperature of the sample increased linearly with the increase of microwave radiation power and radiation time;The higher the temperature of the sample,the more developed the surface cracks are.(2)The microscopic fracture evolution of the samples treated with different cooling methods was analyzed by CT detection technology,and the fractal dimension was introduced to quantitatively characterize the fracture distribution complexity after different cooling treatments,and the results showed that with the increase of cooling amplitude,the fractal dimension of the fracture width,the proportion of fracture volume and the complexity of fracture distribution of the sample increased linearly.(3)The longitudinal wave velocity of the specimen after microwave radiation and cooling treatment was analyzed by using a non-metallic flaw detector,and the wave velocity was used as a damage variable to study the damage degree of the specimen.The results show that the longitudinal wave velocity of the sample decreases significantly with the increase of microwave radiation power and radiation time,and the wave velocity of the sample decreases by 64.7%,73.9%,78.7%and 83.9%respectively for natural cooling,water cooling,liquid nitrogen cooling for 10 min and liquid nitrogen cooling for 2 h,and the cumulative damage factors of the sample are 0.88,0.92,0.95 and 0.97,respectively.(4)Through the conventional mechanical tests of hematite samples,the variation laws between the stress-strain curve,compressive strength and tensile strength and microwave radiation parameters and cooling mode of hematite samples are obtained.The compressive strength and tensile strength of the samples decreased with the increase of radiation power and time,and the compressive strength of the samples cooled by soaking water,liquid nitrogen for 10 min,and liquid nitrogen for 2h decreased by 12.4%,20.3%and 25.6%,respectively,and the tensile strength of the samples was reduced by 24.1%,61.2%and 86.2%compared with the naturally cooled samples.(5)Through the monitoring of the acoustic emission of the uniaxial compression test process of the hematite sample,the sample will go through the initial compaction stage,elastic deformation stage,crack stability and expansion stage,crack development stage and failure stage after the action of microwave radiation and cooling mode,and the relationship between the number of ringing impacts in each stage and the cumulative ringing number in the whole process is studied,and the influence of microwave radiation and cooling mode on the weakening effect of hematite is further revealed.It is concluded that the cumulative ringing number of the specimen increases with the increase of microwave power,and the high-frequency active region of the AE signal during uniaxial compression is mostly concentrated at the peak stress point of the specimen,and the AE ringing number of the specimen after cooling treatment by water and liquid nitrogen is more frequent in each stage than that of the naturally cooled specimen.更多还原