摘要
近年来，矿产资源的勘探深度越来越大，硬岩地层越来越多，各国学者将解决硬岩钻进的基本问题集中在声波振动碎岩，超声波振动碎岩以其所需轴向力小，大体积破碎，设备轻便，有利降低钻进成本等优点深受各国喜爱。超声波振动碎岩运用超声波碎岩装置将放大后的机械振幅沿着钻杆、钻头，施加到岩石上。当岩石固有频率和施加给岩石的机械振动频率相等时发生共振，使岩样发生破坏，最终达到超声波振动碎岩的目的。但岩石由于自身材料的特殊性，包括节理、裂隙、孔洞等不可预见的损伤，岩石成为人工利用的天然材料中最为复杂的一种材料，随着超声波振动碎岩时间的延长，岩石内部孔隙开裂扩展，其内部进一步发育大量不规则、多尺寸的孔隙，进而影响岩石的物理力学性质。因此本文采用理论分析、有限元数值模拟与试验相结合的方法，探寻随着时间延长超声波振动对花岗岩孔隙结构及强度的损伤规律。目前对超声波振动碎岩做了大量试验，但超声波振动时间对碎岩效果的研究几乎是空白，所以超声波振动碎岩振动时间的研究，对进一步提高超声波碎岩效果具有重要参考意义。
橙色系研究岩石在超声波不同振动时间下，强度下降的规律、岩石损伤规律（孔隙大小、多少变化规律），为下步将超声波振动器应用于硬岩钻进，深部探测，研发超声波振动碎岩钻机提供理论指导。
采用岩石的疲劳破坏、损伤力学和格里菲斯理论对超声波振动时间对碎岩损伤影响规律的问题进行研究，得出超声波振动下岩石损伤机理：超声波振动随着振动时间的延长，疲劳碎岩存在最小阈值时间，
栈房只有当超声波振动时间大于该最小阈值时间时，加载能量使花岗岩内部微裂纹开裂汇聚为中裂纹，低于时间阈值时超声波振动能量导致花岗岩内部损伤累积，花岗岩发发育微裂纹。
广告软文采用ANSYS有限元进行数据模拟关于超声波振动时间对碎岩损伤影响规律的问题进行研究。建立了符合实际的非均质岩石模型，通过计算机强大的运算能力得出随着时间延长超声波振动对花岗岩不同的损伤程度，并提出超声波振动时间阈值（仿真分析得到时间阈值在15-20分钟之间），对于进一步提高超声波振动碎岩，为试验提供理论指导。
采用核磁共振试验和单轴抗压强度测试对超声波振动时间对碎岩损伤影响规律进行研究，得出：1.超声波频率作用下不同时间对脆性材料破坏规律，强度
形容雾
下降，孔隙变化情况，为定量分析岩体结构的破坏形式打下试验方面的基础。2.超声波频率振动下非均匀岩样中包含了从微观到宏观的各种尺寸的缺陷，岩样从原始状态直到最终破坏的整个过程中，裂纹扩展汇合微小裂纹在数目增多的状况下逐渐发育为大尺寸裂纹。
机器人足球超声波振动碎岩一般经历四个阶段：第一阶段（0-10分钟）：岩石在疲劳作用下内部初始损伤发育，振动对岩石内部裂纹的影响较小主要集中在岩石浅层部分；第二阶段（15-20分钟）：微裂纹开裂扩展，岩石初始损伤开始进一步加剧，岩石经过损伤累积阶段此时超声波振动能量用于微裂纹开裂，裂纹在低应力状态下进入裂纹开裂临界值；第三阶段（20-25分钟）：裂纹处于平稳发展阶段，时间的
延长能够对超声波振动下岩石破碎效率的提高起到促进作用，但递增幅度平缓，疲劳碎岩过程岩样裂纹以稳定速度扩展开裂；第四阶段（25-30分钟）：岩石进入损伤快速累积阶段，岩石发生裂纹的扩展速度加快，内部大裂纹汇合贯通，岩石的强度下降速率大幅度升高，从而出现岩石损伤和破坏导致岩样断裂。
关键词：超声波振动时间；岩石损伤；时间阈值煎饺
钱学森精神Abstract
In recent years,the exploration depth of mineral resources is increasing,and there are more and more hard rock strata.The scholars of every country will solve the basic problems of hard rock drilling in the acoustic vibration of rock.Ultrasonic vibrating rock is loved by all countries becau of its small required axial force,large volume broken,portable equipment and helping reduce drilling cost and other advantages. Ultrasonic vibrating rock u the ultrasonic vibrating rock device to apply the magnified mechanical amplitude to the rock along the drill pipe and drill bit.When the natural frequency of the rock and the mechanical vibration frequency applied to the rock are equal,the resonance occurs,so that the rock samples are destroyed,and ultimately to achieve the purpo of ultrasonic vibration of rock.However,due to the particularity of its own materials,including unpredictab
le damagesof joints,cracks, holes and so on,the rock becomes the most complicated material in the natural material ud for artificial u.With the prolongation of the time of ultrasonic vibration,the pore expansion of the rock is expanded,and a large number of irregular and multi-sized pores are developed in the interior,which affect the physical and mechanical properties of the rock.Therefore,this paper us the methods of theoretical analysis,finite element numerical simulation and experiment to explore the law of damage to granite pore structure and strength with prolonged ultrasonic vibration.At prent,a large number of tests have been done on ultrasonic vibrating rock,but the study of the effect of ultrasonic vibration time on the rock is almost blank.Hence,the study of vibrating time of ultrasonic vibration has important reference significance to further improve the effect of ultrasonic cutting.
This paper studies the law of rock descending under different vibration time and the law of rock damage(pore size,how many change laws),and provides the theoretical guidance for the application of ultrasonic vibrator to hard rock drilling,deep exploration and development of ultrasonic vibration rock drilling rig.
Bad on the fatigue damage,damage mechanics and Griffith theory of rock,the influence of ultrasonic vibration time on the damage of rock is studied,and the mechanism of rock damage under
ultrasonic vibration is obtained:Ultrasonic
vibration increas with the vibration time and there is a minimum threshold time for fatigue lithotripsy.Only when the ultrasonic vibration time is greater than the minimum threshold time,the loading energy caus the microcracks in the granite to crack into the middle crack,and the ultrasonic vibration energy leads to the accumulation of granite internal damage and the microcracks of the granite.
The finite element of ANSYS is ud to simulate the influence of ultrasonic vibration time on the damage law of rock.A reasonable model of heterogeneous rock is established,and the damage degree of the granite is obtained with the time of prolonged ultrasonic vibration,and the ultrasonic vibration time threshold(the time threshold for the simulation analysis is between15and20minutes)is obtained by simulation,which will further improve the ultrasonic vibration of rock to provide theoretical guidance for the test.
The effects of ultrasonic vibration time on the damage of crushed rock are studied by using NMR and uniaxial compressive strength tests.The results are reached as follows:1.Under the action of ultrasonic frequency,the failure law of brittle materials is studied at different time.The decrea in stre
不买社保承诺书ngth and the change of porosity are the basis for quantitative analysis of the failure mode of rock mass structure.2.Under the ultrasonic frequency vibration,the nonuniform rock samples contain defects from microscopic to macroscopic dimensions.In the whole process from the original state to the final failure,the crack propagation confluence of small cracks gradually develops into large-size cracks in the increasing number of cas.
Ultrasonic vibrating rock generally undergoes four stages:The first stage(0-10 minutes):under the action of fatigue,the initial damage within the rock develops and the effect of vibration on the internal cracks of the rock is mainly concentrated in the shallow part of the rock.The cond stage(15-20minutes):the microcracks crack and the initial damage begins to intensify.The rock is subjected to the damage accumulation stage.At this time,the ultrasonic vibration energy is ud for microcrack cracking,and the crack enters the critical value of crack cracking under low stress.The third stage(20-25minutes):the crack is in the stage of steady development,and the extension of time can promote the improvement of the crushing
efficiency of the rock under the ultrasonic vibration.However,the increment of the crack is smooth and the crack is cracked at the steady speed.The fourth stage(25-30 minutes):when the rock enters the rapid accumulation stage of the damage,the crack propagation speed of the rock is accelerated,t
he internal large cracks converge and the rate of decrea in the strength of the rock is greatly incread,which results in rock damage and destruction leading to rock fracture.
Key words:ultrasonic vibration time;rock damage;time threshold
