基于EMD的粉砂岩单轴压缩破裂损伤分析

通过RMT-150C岩石力学测试系统与SAEU2S型声发射仪器,对粉砂岩进行了单轴压缩声发射试验。运用荷载—时间—振铃累计计数关系对岩样损伤阶段进行划分,利用经验模态分解法(EMD)对不同损伤阶段的典型信号源进行了分解,并结合EMD能量熵分析声发射信号能量分布,进而对岩体损伤阶段进行描述。结果表明,粉砂岩单轴压缩破裂可分为起始损伤期、损伤发展期、损伤加剧期、试件屈服期及试件断裂层剥离期五个阶段,其EMD能量熵主要能量所占优势频率分布情况呈现先往高频发展、再往低频发展的趋势。利用EMD能量熵能有效分辨岩样损伤过程中的声发射源信号特征,为评估岩体损伤变化奠定了基础。     

Experimental investigations on effects of gas pressure on mechanical behaviors and failure characteristic of coals

The mechanical behavior of coal is the key factor affecting underground coal mining and coalbed methane extraction. In this study, triaxial compression and seepage tests were carried out on coal at different gas pressures. The mechanical properties and failure process of coal were studied, as well as the acoustic emission (AE) and strain energy. The influence of gas pressure on the mechanical parameters of this coal was analyzed. Based on the conventional energy calculation formula, the pore pressure was introduced through the effective stress formula, and each energy component of coal containing gas was refined innovatively. The contribution of gas pressure to the total energy input and dissipation during loading was quantitatively described. Finally, the influence of gas pressure on coal strength was theoretically analyzed from the perspectives of Mohr–Coulomb criterion and fracture mechanics. The results show that the total absorbed energy comprises the absorbed energy in the axial pressure direction (positive) and in the confining pressure direction (negative), as well as that induced by the pore pressure (initially negative and then positive). The absorbed energy in the axial pressure direction accounts for the main proportion of the total energy absorbed by coal. The quiet period of AE in the initial stage shortens, and AE activity increases during the pre-peak stage under high gas pressure. The fractal characteristics of AE in three stages are studied using the correlation dimension. The AE process has different forms of self-similarity in various deformation stages.     

河北地区土水特性曲线试验及数据库研究

非饱和土土水特性试验是获取非饱和土力学参数的重要途径,但由于耗时过长,严重影响着非饱和土理论的实际应用。本文利用新型土水特性曲线压力板仪,对河北省范围内三处典型地区的土质进行了土水特性曲线室内试验,分析研究了土质、埋深与孔隙率对土水特性曲线的影响。在此基础上构建了河北地区土水特性曲线数据库,通过数据库可以快捷地得到相应地区同类土层的土水特性曲线参数,为快速获取非饱和土力学参数提供了途径。     

The coal cleat system： A new approach to its study

After a general analysis regarding the concept of coal ＂cleat system＂, its genetic origin and practical applications to coalbed methane （CBM） commercial production and to C02 geological sequestration projects, the authors have developed a method to answer, quickly and accurately in accordance with the industrial practice and needs, the following yet unanswered questions： （1） how to define the spatial orientation of the different classes of cleats presented in a coal seam and （2） how to determine the frequency of their connectivites. The new available and presented techniques to answer these questions have a strong computer based tool （geographic information system, GIS）, able to build a complete georeferentiated database, which will allow to three-dimensionally locate the laboratory samples in the coalfield. It will also allow to better understand the coal cleat system and consequently to recognize the best pathways to gas flow through the coal seam. Such knowledge is considered crucial for understanding what is likely to be the most efficient opening of cleat network, then allowing the injection with the right spatial orientation, of pressurized fluids in order to directly drain the maximum amount of gas flow to a CBM exploitation well. The method is also applicable to the CO2 geological sequestration technologies and operations corresponding to the injection of CO2 sequestered from industrial plants in coal seams of abandoned coal mines or deep coal seams.     

混凝土力学参数与声发射参数之关系研究

通过对混凝土和钢纤维混凝土进行单轴压缩试验和声发射试验研究,首先应用Dai公式分析了声发射事件数与应力之间的关系,验证了其适用性和有效性;其次提出了声发射概率密度函数的概念,并且将其应用到混凝土材料的损伤评估,分析了不同荷载水平的损伤过程。     

混凝土梁破坏机制的声发射特性实验研究

记录了钢纤维混凝土,素混凝土和砂浆试件断裂过程中的声发射（AE）信号,并对其进行了分析和处理,通过对声发射信号持续时间设置滤值,以声发射信号的振幅分布特性为判据,并依据事件峰值对应的振幅大小,将它们的声发射信号持续时间分别划分为9个,7个和5个区段,并通过细胞细观层次上破坏机制的分析,分析得到了各破坏机制所对应的声发射参数特征。     

光纤到户技术的组网与设计

本文概述了光纤到户（FTTH）接入方式的优点,阐述了基于EPON（Ethernet Passive Optical Network以太网无源光网络）的光纤到户方案的系统架构、传输原理,光配线网络（ODN）基本结构、组网原则和模式。最后以工程实例介绍了基于EPON技术的光线到户接入技术在住宅小区中的应用。     

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.     

Acoustic emission characterization of microcracking in laboratory-scale hydraulic fracturing tests

Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces (i.e. damage). Acoustic emission (AE) monitoring and analysis provide unique information regarding the microcracking process temporally, and information concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of understanding the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. It was quantitatively observed that the recorded AE signals provided sufficient information to generalize the damage radiating spatially away from the injection wellbore.     

多向压复合应力状态下A-E-C的强度性能研究

为准确认识引气混凝土(A-E-C)在多向压复合应力状态下的强度性能,通过试验对立方体强度为C30的A-E-C进行了单向压、双向压(应力比α=σ2∶σ3=0.25∶1.0,0.50∶1.0,0.75∶1.0,1.0∶1.0)以及三向压(应力比α=σ1∶σ2∶σ3=0.1∶0.25∶1,0.1∶0.5∶1,0.1∶0.75∶1,0.1∶1∶1)加载状态下的强度特性研究.对试件的破坏形态以及6个面上裂缝的走向进行了观察描述,根据试验结果,分析了应力比对多向压复合状态下A-E-C的极限强度的影响规律;并与在单向压、多向压(双向压以及三向压)复杂荷载作用下普通混凝土的研究内容进行了比较分析.在此基础上,建立了相应的破坏准则,为A-E-C结构的有限元分析提供了试验、理论依据.     

Microcrack fracturing of coal specimens under quasi-static combined compression-shear loading

Coal pillars are usually loaded under combined compression-shear stresses at underground coal mines. Their long-term stability is critical to the utilization of underground structures, such as underground reservoirs at coal mines. In this study, a modified rock property testing system was used to explore the mechanical properties of coal specimens under quasi-static combined compression-shear loading conditions. The acoustic emission technique was applied to investigating the microcrack fracturing of coal specimens at various inclination angles. The experimental results show that specimen inclination has remarkable effects on the microcrack initiation, microcrack damage and ultimate failure of the coal specimen. The failure mode of the coal specimen tends to transit from axial splitting to shear failure with increasing specimen inclination, and its peak strength is closely associated with the microcrack damage threshold. In practice, it is recommended to consider coal strength under combined compression-shear loading when using empirical pillar strength formulae so that the effect of pillar inclination can be included.     

基于4D-BIM的施工进度-资源均衡模型自动构建与应用

针对工程项目施工进度与资源均衡的关键需求,研究基于清华大学4D-BIM模型建立了基于4D-BIM模型解决进度-资源均衡问题的技术路线。研究通过4D-BIM模型进度及资源信息与离散事件仿真模型的转化机制,实现了进度-资源均衡模型的自动构建。同时,论文对基于模拟退火算法求解进度-资源均衡模型的过程进行了分析和讨论。上述整体方案应用于工程实际数据,取得了较好的结果。研究成果表明,进度-资源均衡模型的自动构建及智能仿真、求解极大地减少了建模工作量,提高了工作效率,为工程管理者方便快捷地制定工程进度计划与资源配置方案提供了切实可行的工具。     

声发射监测煤矿动力灾害工艺技术研究

声发射监测工艺技术是能否准确监测煤矿动力灾害的关键技术。通过数值模拟和实验室实验的方法对波导器的直径和长度进行了优化,同时利用现场考察的方式对不同长度、直径波导器接收AE信号的效果进行了考察,确定波导器的直径为20 mm、长度应大于巷道破碎圈宽度。利用现场考察的方式对波导器的安装工艺进行了确定,波导器距离掘进工作面的距离应保持在6～25 m范围内;波导器迎向巷道掘进方向,安装仰角处于3～20°之间较为合理;波导器接收AE信号端位于破碎圈以外的原始应力区、波导器用软性材料穿套及传感器用弹性套筒保护等可以起到良好的阻噪作用。     

接触面滑坡滑带土吸力的滤纸法测试

吸力是控制非饱和土状态的一个决定性因素,滤纸法就是一种间接测量吸力的方法,具有成本低、测量范围大、测量精度高等优点。滤纸法测试土样取自甘肃省天水市一黄土–泥岩接触面滑坡的滑带土,该土样的强度对含水率变化非常敏感,因此对该滑带土的非饱和特性的研究至关重要。试验中首先测定了该滤纸干湿两种状态下的平衡时间,然后对试样分别采用干湿两种状态下的双圈牌203和WhatmanNo.42型滤纸进行了对比试验,运用接触式和非接触式方法分别测定试样的基质吸力和全吸力。通过分析对比低吸力段滤纸含水率,确定了滤纸法测试该类土的下限吸力值。采用Oringin软件对试样全阶段基质吸力曲线拟合,确定了相应的拟合参数和合适的拟合方程。为进一步研究和治理该滑坡提供了参考价值。     

基于透明土技术土岩边坡滑移机理的模型试验研究

随着工程技术的飞速发展,土岩边坡滑移机理的研究具有重要的意义和工程应用价值。通过透明土模型试验研究坡顶荷载作用下土岩界面接触滑移机理和规律,实现了土岩边坡内部滑移变形的可视化。考虑了岩体Barton节理粗糙度系数、坡体角度和坡体高度等因素对土岩边坡稳定性的影响。利用粒子图像测速(PIV)和激光散斑技术,获得了土岩边坡在坡顶荷载作用下内部变形的特征。试验分析表明,土岩边坡的滑动可分为3个阶段:初始阶段、匀速阶段和加速阶段;在土岩边坡滑移过程中减小岩体Barton节理粗糙度系数、增大坡体高度、增大坡趾角度将引起边坡土体内部较大的位移,进而引发土岩边坡的失稳。采用双排抗滑桩的边坡防护措施后,有效地延缓边坡土体内部位移的发展,提高土岩边坡的稳定性。文中研究成果为揭示土岩边坡滑移机理及其工程防护的有效性提供了重要的理论依据,通过跟踪透明土颗粒的运动轨迹实现土体内部变形可视化的土岩边坡滑移提供了试验依据。     

探讨分子印迹电化学传感器对双酚A的检测

利用分子印迹技术(MIT),以双酚A(BPA)为模板分子,邻氨基苯硫酚(ATP)为功能单体,通过自组装和电聚合方法制备双酚A分子印迹聚合膜电化学传感器,采用循环伏安法和交流阻抗法进行表征,并用于双酚A的检测,该研究结果为电化学聚合法制备分子印迹聚合膜,根据功能单体与模板分子的相互作用正确选择功能单体提供了理论基础。     

基于数字化技术的上海市燃气调度应急指挥系统平台

文章以上海市燃气调度中心近年来构建的数字化燃气调度应急指挥系统平台为背景,阐述了平台架构、平台各系统及运作方式与技术特征,并对平台未来建设作了展望。     

Numerical study on static and dynamic fracture evolution around rock cavities

In this paper, a numerical code, RFPA^2D (rock failure process analysis), was used to simulate the initiation and propagation of fractures around a pre-existing single cavity and multiple cavities in brittle rocks. Both static and dynamic loads were applied to the rock specimens to investigate the mechanism of fracture evolution around the cavities for different lateral pressure coefficients. In addition, characteristics of acoustic emission (AE) associated with fracture evolution were simulated. Finally, the evolution and interaction of fractures between multiple cavities were investigated with consideration of stress redistribution and transference in compressive and tensile stress fields. The numerically simulated results reproduced primary tensile, remote, and shear crack fractures, which are in agreement with the experimental results. Moreover, numerical results suggested that both compressive and tensile waves could influence the propagation of tensile cracks; in particular, the reflected tensile wave accelerated the propagation of tensile cracks.     

高锰酸钾-粉末活性炭联用去除原水中的嗅味

针对常规处理工艺难以解决东江原水发臭的问题,考察了高锰酸钾-粉末活性炭联用技术对水中嗅味的去除效果。结果表明,高锰酸钾一粉末活性炭联用对水中嗅味具有较好的去除效果,当氧化吸附时间为30min,高锰酸钾投加量为1．5mg/L,粉末活性炭投加量为40mg／L时,经混凝沉淀后水中的嗅味可由5级降至0级。此外,高锰酸钾和粉末活性炭联用对水中的有机物、浊度及锰也有明显的去除效果。