岩石声发射的Kaiser效应研究进展

简要介绍了声发射技术的原理、发展史,从Kaiser效应应用方面,还介绍了声发射技术的研究成果.还介绍了岩石的Kaiser效应及声发射技术在岩土工程中的应用.最后讨论了声发射技术未来的研究方向.     

含层理岩石的AE特征分析及基于Kaiser效应的地应力测试研究

 针对煤矿沉积岩系地应力测试需要,通过单轴压缩声发射实验,分析顶板含层理沉积岩系岩石试件的破坏特征、声发射特征,研究Kaiser效应点的综合判断方法及基于声发射Kaiser效应的地应力计算方法。研究表明：(1) 单轴荷载作用下,无层理岩石试件破坏过程为：加载→完全破坏,表现出脆性破坏特征;含层理构造的岩石试件的破坏过程为：加载→局部滑移剪切破坏→加载→剪切带失稳、岩石试件破坏。(2) 无层理岩石试件的AE总计数随时间的增长趋势表现为“缓慢增长→急剧飙升”型,而含层理岩石则呈现出“台阶状”上升趋势,分析认为产生这种不同规律的根源在于岩石内部损伤破坏过程的差异性。(3) 通过研究AE特征提出Kaiser效应点综合判断方法,并完善Kaiser效应法地应力计算方法,最终得到测点地应力为： = 25.06 MPa, = 13.75 MPa, = 8.07 MPa,验证表明：计算结果在大小及方向上均具有一定的可信度。故提出的Kaiser效应点判断方法和地应力计算方法可用于Kaiser效应法地应力测试,该实验研究方法和结果可为工程实践或类似研究提供借鉴和参考。     

基桩声波透射法比对检测试验结果的分析和启示

本文通过对14家检测单位所做的基桩声波透射法检测试验结果的比对,提出了各检测单位提供的声速参数存在的问题,分析了产生这些问题的原因;最后,通过数值实例,阐明了在计算声速临界值时,还应充分考虑"大值异常"数据的影响.     

饱水对花岗岩声发射平静期影响的实验研究

通过对干燥和饱水花岗岩进行单轴加载声发射实验和扫描电镜实验,研究饱水对花岗岩破坏前声发射平静期的影响。结果表明:干燥和饱水花岗岩破裂前声发射事件率均出现平静期,干燥花岗岩在峰值载荷的54.89%时进入声发射平静期,饱水花岗岩约为峰值载荷的89.87%;干燥花岗岩平静期内AE事件率小且恒定,AE能率较高,饱水后平静期内AE事件率增大,AE能率减小;干燥花岗岩平静期内声发射波形信号的熵值为1.5~2.5,饱水花岗岩为0.5~1.5;饱水改变了花岗岩的微观破裂模式,这为水是如何影响岩石的声发射特征提供了理论依据。实验结果丰富了对岩石声发射平静期的认识,这对岩石破裂声发射监测中前兆现象的识别具有重要意义。     

不同围压下页岩声发射及破裂前兆信息研究

对页岩进行常规三轴压缩下的声发射试验,并以时间为参考变量,得到力学与声发射参数之间的耦合关系,对其进行分析,以研究常规三轴压缩下页岩声发射特征的围压效应及其破裂前兆信息,并进一步揭示岩石破坏的微观机制,结果表明:(1)页岩声发射信号可分为4个阶段,即:原生裂纹压密阶段、平静阶段、爆发阶段、破坏阶段。(2)随着围压的升高,页岩的峰值强度随之升高,损伤强度σcd也随之升高,并且其数值约为峰值强度的91%。(3)随着围压的升高,由于破裂后的岩块之间的破裂面在凹凸处存在相互啮合啃断,岩样声发射信号在峰后残余强度阶段出现多个峰值。(4)页岩声发射RA值在主破裂发生前都有突然增大,并达到峰值的现象,预示着主破裂即将发生,因此可以将声发射RA值的突然增加作为页岩主破裂前兆信息。     

Comparison of different sampling techniques for the evaluation of pesticide spray drift in apple orchards

An analytical method using gas chromatography-mass spectrometry has been developed for the evaluation of different sampling techniques to characterise spray drift in a commercial apple orchard. Eleven pesticides were studied (fungicides, insecticides and herbicides). A collection of airborne spray-drift pesticides released from a low-profile air-blast orchard sprayer was investigated using six types of samplers: (1) a Perkin-Elmer low volume automatic air sampler using with glass tube packed with Supelpak-2; (2) a high volume air sampler: (3, 4) an impinger containing cyclohexane that could be preceded by a glass fibre filter; and (5, 6) glass cartridges packed with Supelpak-2 that could be preceded by a glass fibre filter. Retention efficiencies of the different sampling techniques are compared, and physical forms of the retained pesticides are discussed. These techniques have allowed us to evaluate pesticide spray-drift in the orchard. Results have shown that the molecules' properties (k(H) and vapour pressure) and weather conditions (temperature and relative humidity) strongly influence pesticide gas and particles distribution. However, in the studied orchard, it is difficult to differentiate pesticide spray-drift and post-application transfers since treatment duration was > 2 days.     

The field comparison of three measuring techniques for evaluation of the surface dust level in ventilation ducts

This paper reports the comparison of three measuring methods for quantifying the amount of dust on the inner surface of ventilation ducts: 1) a vacuum test method; 2) a gravimetric tape method; and 3) an optical method. Thirteen recently constructed buildings were selected for the field test in the Helsinki metropolitan area. The dust samples in each method were all taken from the same location in the duct. Most of the ducts sampled had no residual oil originating from the manufacturing process. The mean amount of dust measured with the vacuum test method was 1.3 g/m2 and the range was < 0.1-8.4 g/m2. The mean surface dust level measured using the gravimetric tape method was slightly lower, i.e. 1.2 g/m2 (< 0.1-5.0 g/m2). The mean cleanliness level of the ducts was 15% (2-41%) using the optical method. The wide variations and differences in the results of the different methods were caused by the unequal distribution of dust on the duct surfaces.     

基于声发射的RT轨道机疲劳加载信号特征提取与分析

本文在不同应力条件下对RT轨道机进行疲劳加载,采集RT轨道机从加载到断裂时的信号,对信号进行时域和频域分析观察信号特征对RT轨道机断裂原因进行探讨。     

矿山开采应用混装乳化炸药技术钻孔直径变化对技术参数与成本的影响分析

利用混装乳化炸药技术的耦合装药优势,对不同孔径下爆破技术参数的对比和综合成本进行了分析比较。根据不同孔径下的爆破效果分析,在新白马矿进行矿山开采时选用大孔径钻机钻孔配合混装乳化炸药技术具有很高的综合经济效益,对于其他大型矿山具有借鉴意义。     

Quantifying stresses and support requirements in the undercut and production level drifts of block and panel caving mines

A numerical modelling strategy has been developed in order to quantify the magnitude of induced stresses at the boundaries of production level and undercut level drifts for various in situ stress environments and undercut scenarios. The results of the stress modelling were in line with qualitative experiential guidelines and a limited number of induced stress measurements documented from caving sites.A number of stress charts were developed which quantify the maximum boundary stresses in drift roofs for varying in situ stress regimes, depths and undercut scenarios. This enabled many of the experiential guidelines to be quantified and bounded.A limited number of case histories of support and support performance in cave mine drifts were compared to support recommendations using the NGI classification system. The stress charts were used to estimate the Stress Reduction Factor for this system. The back-analyses suggested that the NGI classification system might be able to give preliminary estimates of support requirements in caving mines with modifications relating to rock bolt length and the support of production level intersections.     

侧压对巷道岩爆声发射及损伤特性影响试验研究

采用双轴刚性伺服控制系统进行花岗岩岩爆模拟试验,采用美国物理声学公司生产的PCI-2型声发射系统同步采集岩爆过程中的声发射数据,研究了不同水平构造应力对巷道岩爆的影响。研究结果表明:随着侧压的升高,花岗岩峰值强度随之增加,并且孔洞内壁初次弹射岩屑的时间提前;轴向载荷达到峰值荷载的80%～88%时,声发射进入平静期。随着侧压的增大,峰值载荷前的声发射平静期延长,振铃计数率突增点出现的时间提前;随着侧压的增大,岩样出现初始损伤的时间相对滞后。花岗岩孔洞内出现碎片弹射时,声发射b值下降到最低值,这一现象可作为发生岩爆的前兆特征。     

从某砌块厂生产与管理过程得到的启示

通过实践,笔者认为生产优质空心砌块最基本前提条件是:一应有精良的设备;二应具备先进的生产技术,三应有完善的质保体系。     

欧盟国家的"紧凑"策略:以英国和荷兰为例

文章围绕欧盟国家的"紧凑"策略展开,分别介绍了英国在可持续思潮引导下的"紧凑"策略和荷兰不同时期"紧凑"策略的侧重点.在经历了城市的迅速扩张和城市中心衰败的历史时期后,这些国家选择以一种更为"紧凑"的城市发展模式应对不断出现的城市问题成为欧盟国家共同的趋势.     

欧盟国家的“紧凑”策略:以英国和荷兰为例

文章围绕欧盟国家的“紧凑”策略展开,分别介绍了英国在可持续思潮引导下的“紧凑”策略和荷兰不同时期“紧凑”策略的侧重点。在经历了城市的迅速扩张和城市中心衰败的历史时期后,这些国家选择以一种更为“紧凑”的城市发展模式应对不断出现的城市问题成为欧盟国家共同的趋势。     

填石路基的压实机理、影响因素及质量控制初探

从分析填石路基压实机理及影响填石路基压实和石料级配等对填石路基压实的影响,提出了填石路基层厚、填料最大粒径要求、填石路基密实度检测方法和沉降量控制。     

刨花板端面和平面甲醛散发的分布

通过实验分析了刨花板端面和平面甲醛散发的分布特征，给出了数学模型。作者认为，注意甲醛散发试件的取样位置是必要的。     

Immobilization of slimes obtained during the magnetic and sorption water treatment from radionuclides

A process flow diagram for the magnetic and sorption treatment of water from radionuclides has been proposed. Basic technology concepts were developed for the conditioning of water treatment radioactive slimes aimed at immobilization of radionuclides. A new type of matrices (glass-ceramic matrices) was used for processing slimes produced during the magnetic and sorption treatment of ⁹⁰Sr-containing water. Optimal conditions were determined for reliable immobilization of radionuclides in the proposed matrices. A comparative technical and economic analysis of technologies for immobilization of radioactive wastes has been made.     

Concise formula for the critical buckling stresses of an elastic plate under biaxial compression and shear

This study aims to develop a concise formula for the critical buckling stresses of a simply supported plate under biaxial compression and shear. The critical stresses are obtained for different aspect ratios using classical plate theory and the Ritz method. The four-dimensional critical stress formula, which is expressed in terms of the three in-plane stresses and the aspect ratio, is developed empirically according to the two-dimensional relationships between the in-plane stresses. The findings that are of interest are: (1) the critical stress relationship is linear for the aspect ratios within the range 1 to and nonlinear for the aspect ratios within the range to 5; and (2) as shear stress approaches its critical value, the critical stress relationship becomes increasingly linear and less dependent on aspect ratio.