锚杆锚固体系中的固结波速研究

 采用理论分析、数值模拟和实验室测试对不同锚固质量锚杆中的应力波在锚固段的传播速度进行分析。模拟试验中采用不同龄期的混凝土模拟不同锚固强度,数值模拟中通过改变弹性模量和泊松比实现改变锚固强度。数值模拟和试验模拟结果定性吻合;都显示锚杆中锚固段的应力波波速(固结波速)和锚固介质的强度直接相关,固结波速和锚固介质强度之间成抛物线关系。起初固结波速随锚固介质强度的增加而减少,到达最底点后随着锚固介质强度的增加而增加。用数值模拟结果对产生这种现象的本质原因进行分析讨论。模拟显示固结波速随锚固介质强度的变化是由锚杆中的P波以及锚杆和锚固介质界面处产生的界面波此消彼长而引起的。     

应力波法检测锚杆锚固质量的试验研究

对不同位置、不同缺陷长度锚杆锚固体系模型进行了室内试验,探讨了检测锚杆锚固质量时波的传播规律,指出对于有缺陷的锚杆锚固体系,波形在缺陷位置处出现畸形,变得不规则,并呈现出缓慢衰减态势;对于缺陷位置不同的锚杆,测试曲线表现出不同的波形特征。     

应力波法锚杆加固无损检测的数值模拟分析研究

应力波法锚杆加固无损检测是一种快速、有效的无损检测方法。将锚固体中锚杆和砂浆近似看作各向同性体，应用复合材料的观点，建立砂浆锚杆在力学和物理上等效的一维匀质杆件模型，并确定了等效的工程常数。在一维杆纵向波动理论的基础上给出应力波在锚固体中传播的控制方程，对锚固体缺陷进行数值模拟，通过对控制方程的系数调整，模拟分析了不同缺陷的锚固体在冲击荷载作用下的动力响应。通过实际工程中模型锚杆的实测波形和数值模拟动测曲线进行比较分析表明，采用所建模型的理论分析结果能较好地反映实际锚杆瞬态纵向动力作用特征，激振力函数、等效参数、对锚杆纵向振动特征的模拟是有效的，对提高检测结果的准确性有较重要的意义。     

锚固质量的无损检测技术

基于锚固体系的锚杆动力学及应力波运动学理论,研究了锚固体系的振动特征和锚固体系中声频应力波传播的能量衰减规律,进而提出快速普查检测锚杆锚固状态的声频应力波法：介绍了依据拉拔曲线转折段两边割线的交点法确定锚杆锚固力的无损拉拔检测技术原理,并实际应用于潘集第一煤矿巷道锚杆支护施工质量的检测。     

完整锚杆横向动力响应问题的求解与分析

锚杆锚固质量两个主要衡量指标是锚固状态和锚固力。锚固状态是指锚杆施工后的锚固段长度、自由段长度、密实度和施工缺陷等;锚固力指现场拉拔试验过程中临界破坏点的拉拔力,又称极限抗拔力。利用振动波传播具有的许多独特性质,可以在锚杆表面人工激发应力波来探测锚杆体系内部的结构和性质,以此来判断锚杆的锚固状态。锚杆的无损检测研究已提出多年,但研究方向主要为纵向振动,有关锚杆系统的横向动力响应很少有人提及。建立了锚杆体系横向动力响应的理论模型,推导了完整锚杆的理论半解析计算公式,在此基础探讨了锚杆系统横向振动随锚杆长度、激振力作用时间等变化的一些规律。     

基于小波分析的砂浆锚杆锚固质量缺陷评价

对深基坑支护中常用的岩土锚杆进行锚固质量无损检测的关键是对采集的动态加速度曲线进行合理的分析。为此,分别设计了三种不同工况模型:无缺陷、一个缺陷和两个缺陷的锚杆模型。通过敲击试验,采集到加速度响应曲线后,利用Matlab程序在计算机上实现波形重现,然后采用小波分析等方法对振动波形进行对比分析,建立振动波形与各工况之间的内在联系,以反映锚杆锚固质量的三个度量参数,亦即一次行波周期、时频谱中的频率值和能量衰减程度。结果发现:通过时域波形和时频谱可正确反映不同锚固状态下的动力响应规律,即锚固质量越好,锚杆中应力波衰减就越快。     

锚杆-围岩结构系统低应变动力响应理论与应用研究

建立锚杆一围岩结构系统低应变纵向动力响应的数学力学模型，为研究锚杆结构系统的无损探伤原理及方法提供理论依据。通过理论研究、实验室模型试验和数值模拟试验等技术，研究不同损伤锚杆应力波的传播规律、特性。锚杆系统动力参数的变化可准确反映锚杆的损伤程度，而动力参数的识别是衡量锚杆锚固质量的一条途径，同时提出一种对锚杆-围岩结构系统进行参数反演的遗传算法。利用现代信号分析理论，通过神经网络等现代人工智能手段，探讨锚杆系统损伤位置的确定方法和锚杆-围岩结构系统的识别方法，提出一种锚杆锚固质量定量分析的方法，建立锚杆系统无损探伤的智能诊断系统，并进行现场测试应用。     

锚固体系无损检测的研究(英文)

基于锚固体系中的声频应力波的动力学和衰减特征的室内和现场试验研究与分析 ,提出了快速无损检测锚固体系锚固状态的声频应力波法和无损测定拉拔力的新方法 ,建立了锚固质量检测的分级标准 ,并实际应用于潘一矿锚杆支护施工质量检测 ,结果表明此检测方法是可行的和有效的。     

螺纹钢锚杆楔形端部搅拌树脂锚固剂运移特征及锚固实验

锚固施工时在钻孔内搅拌树脂锚固剂属于隐蔽性工作,不易掌握搅拌后锚固剂的分布情况.采用理论分析、数值模拟及实验室实验相结合的方法,分析螺纹钢锚杆楔形端部形态对锚固剂搅拌效果的影响规律.理论分析表明,锚杆楔形搅拌端的切削角对锚固剂上的作用力及搅拌效果影响较大.锚杆楔形搅拌端会使锚固剂封袋顶部产生凹陷,在锚杆转动时增加了锚固...     

爆炸荷载下锚杆动态响应试验研究

 通过物理模型试验,研究集中装药爆炸荷载作用下临近工作面端锚锚杆的动态响应。利用黏贴在锚杆上的应变片,测得动载期间不同锚杆断面处和距工作面不同距离锚杆上的应变波,并对数据进行分析研究。模型试验结果表明：爆破引起锚杆的振动时间约为5 ms,初始应变波可以是拉伸波,也可以是压缩波;爆破过后锚杆存在残余变形,最大残余应变发生在锚尾的自由段,最大动态拉应变发生在锚杆中部的锚固段。将锚杆的总应变分解为轴向应变和弯曲应变后,发现临近工作面的锚杆在爆炸动载作用下的主要变形为弯曲变形,轴向变形相对较小;动载过后锚杆处于弯曲状态,随锚杆至工作面距离的增加弯曲应变波的频率和幅值下降明显。采用小波包理论分析爆破引起锚杆振动的频率分布,进一步证明弯曲应变波的频率与锚杆至工作面距离的增加而衰减的规律。与以往现场测试结果的比较表明,物理模型试验测得的应变波总体上反映了工程锚杆的动态响应。     

Effects of frequency and grouted length on the behavior of guided ultrasonic waves in rock bolts

Experiments were conducted to study the behavior of guided waves in free and grouted rock bolts. Ultrasonic waves with frequencies from 25 to 100 kHz were used as excitation inputs. Tests were first conducted on free bolts to help understand the behavior of guided waves in non-grouted bolts. The effects of wave frequency and grouted length on the group velocity and attenuation of the guided ultrasonic waves were then evaluated. The test results indicated clear but different trends for the group velocity in the free and the grouted bolts. The attenuation in free bolts was not affected by bolt length and frequency. However, in grouted bolts it increased with frequency and grouted length. It was also found that the two main sources of attenuation are the setup energy loss, which has a fixed quantity for a specific type of test setup, and the dispersive and spreading energy loss which varies with frequency and bolt length.     

锚杆锚固质量无损检测几个关键问题的研究

对近年来有关锚杆无损检测的研究工作进行总结.通过理论分析和实验研究,对锚杆锚固质量无损检测中的几个关键问题进行较为深入的探讨研究:通过逐渐改变锚杆自由段和锚固段相对长度的方法,研究底端反射的变化规律,得出锚固长度小于3/4首波波长时底端反射不明显的结论;通过对锚固体控制体积的力学分析,用水泥砂浆在不同养护时间内的固化程度和对杆体的握裹强度模拟锚固介质的黏结强度,得出固结波速与锚杆杆体、锚固介质及围岩之间的黏结强度有关的结论;通过对承载条件下锚杆动态响应的分析和实验研究,得出锚固体系的基频和动刚度与荷载呈幂函数增长的规律,以及锚杆的动态响应与锚杆的工作荷载与极限承载能力的相对大小显著相关的结论.研究结果可用于锚杆无损检测的工程实践.     

端锚锚杆工作载荷的导波确定法

 使用纵向导波对端锚锚杆的工作载荷进行无损检测。首先分析端锚锚杆工作载荷在锚杆自由段及锚固段的不同分布特征,然后计算纵向导波在锚杆自由段(承受拉应力)中的传播速度。当锚杆变形在弹性范围内时,随着自由段承受拉应力的增大,同一频率纵向导波在锚杆中传播的群速度逐渐减小,并且群速度与拉应力大小呈线性递减关系;对纵向导波在端锚锚杆锚固段上界面的反射情况进行试验研究,结果表明,45～75 kHz频率范围纵向导波在锚固段上界面有明显的反射回波;提出使用纵向导波在锚固段上界面的反射回波及在锚杆自由段的传播时间来确定锚杆工作载荷的大小,由理论分析得到的工作载荷与导波传播时间的关系曲线与试验结果具有相同的趋势。     

Laboratory testing of a new type of energy absorbing rock bolt

Energy absorbing rock bolts are used as part of rock support systems in underground constructions that are exposed to e.g., rock bursts and detonating explosives. A rock bolt capable of absorbing kinetic energy from these loads must be able to yield with the ground movements and also deform plastically over large distances, at high displacement rates. A new type of energy absorbing rock bolt has been developed and tested in laboratory. The bolt is without a casing and consists of a steel bar that has an inner ribbed-like anchorage section and an outer nut that transfers the load from the rock via a circular disc. When subjected to a dynamic load, the lengthening of the steel bar leads to a decrease in diameter whereby the adhesive bond between bar and grout is lost and the outer end of the bolt is free to yield. The rock bolt is given a very good protection from corrosion when fully grouted in cement. In a laboratory, rock bolts in concrete cylinders were subjected to free fall tests to achieve a loading velocity of 10 m/s. The tests demonstrated that the distribution of plastic strain along the length of a grouted rock bolt is not constant when dynamically loaded. The sections where plastic yielding was allowed were not fully utilized in any of the cases, opposite to that in previous static tests which show almost constant elongation of the bolts. The tests also verified that the load-carrying components of the bolt, the nut and the anchorage, are reliable when dynamically loaded. Elastic and plastic waves will start to propagate through the rock bolt as it is suddenly loaded, resulting in permanent deformation along a section of the bolt. This yield process is demonstrated through a combined graphical and numerical method.     

A new analytical solution for the displacement of fully grouted rock bolt in rock joints and experimental and numerical verifications

This study proposes a new analytical solution to predict displacement of a fully grouted rock bolt intersected by single rock joint. The main characteristics of the analytical model, consider the bolt profile and joint movement under pull test condition. The anchorage capacity of fully grouted bolts has been studied for many years; however, the bolt profile and its effect on bolt shear resistance are poorly understood. Investigations of load transfer between the bolt and grout indicate that the bolt profile shape and spacing play an important role in improving the shear strength between the bolt and the surrounding strata. Rock displacement is a sum of elastic part and a jump part due to the presence of joints planes. The performance of the proposed analytical model is validated by experimental method and comparison with numerical modeling. The results showed that there is a promising agreement between analytical and numerical methods. Studies indicate that the displacement rate between the bolt and the rock declines exponentially. Which is dependent on the bolt characteristics such as: rib height, rib spacing, rib width and thickness grout, material and joint properties.     

全长黏结型锚杆高频超声导波检测应用研究

分析高频纵向轴对称超声导波在全长黏结型锚杆中传播的特性。在不同频率范围内,锚杆中同一模态的衰减特性及速度差别较大。理论上,在1 MHz以上,高阶纵向轴对称模态在特定频率下的轴向位移集中于杆中心,衰减最小,且能量速度最大,可用于全长黏结型锚杆的质量检测。同时建立实验系统,在1.13～2.85 MHz频率范围内对直径φ22 mm、长度1 m的埋于水泥中的无缺陷锚杆进行了频率扫描,并根据实验结果做出第一次端面回波速度和幅值随频率变化曲线,分别与理论能量速度频散曲线和衰减频散曲线相吻合,并且对埋于水泥中带单缺陷锚杆进行导波检测。研究结果表明导波可用于锚杆长度检测及缺陷定位。最后,将此规律应用于在直径为φ18 mm,长度为2 m的锚杆工程现场检测,检测结果较为理想,验证高频超声导波可以应用于全长黏结型锚杆的无损检测。     

地下爆炸作用下节理岩体力学响应的离散元法模拟

To verify the capability of DEM in modeling the dynamic response of rock masses to blasting loads, two underground explosion tests are numerically investigated. Results show that rock joints can significantly affect the transmission and the attenuation of shock waves, and can therefore influence the stability of the adjacent underground structures. Rock joints act as a kind of filters through which only low-frequency components of the shock waves are allowed to pass, and the high-frequency components of the shock waves do no harm to far-field tunnels if a predominant joint set exists in between. The spacing of joint set can also remarkably affect the propagation process. It indicates that as a discontinuum-based numerical approach, DEM is good at simulating the propagation and attenuation of blasting wave in jointed rock masses, and in modeling the stability of underground structures subjected to blasting loads.