冷却塔爆破拆除失稳机制与变形破坏特征研究

冷却塔为高耸薄壁结构,爆破拆除失稳机制复杂。依托H 70 m钢筋混凝土冷却塔爆破拆工程,通过多点无线高清摄像观测、支撑区动应变监测等手段,研究了冷却塔爆破拆除失稳过程中塔体的变形破坏特征和支撑区人字柱的应力演变机制。研究结果表明:切口区人字柱爆破时,首先产生向上的脉冲荷载,脉冲荷载沿塔壁传向支撑区人字柱,使其首先承受动态拉伸荷载;随后,支撑区人字柱首先整体向下压缩,然后发生回弹震荡;重力矩重新分配后,靠近切口区的人字柱承受应变率为10~(-3)/s~10~(-2)/s量级的动态附加压应力,人字柱与圈梁连接点产生压剪破坏;随着人字柱破坏范围的扩大,塔体转动轴逐渐后移,支撑区后部人字柱最终在圈梁节点处发生弯折破坏。     

2座45 m高冷却塔爆破拆除失败原因分析及排险处理

某发电厂2座45 m高冷却塔爆破拆除施工中,冷却塔未按照爆破设计倒塌形成危险倾斜体。通过爆后现场勘查认为人字柱与圈梁拉结筋过少过细、开设减荷槽面积过小、爆破切口长度过大、人字柱本身强度较低,在爆破瞬间其支撑强度不够,造成冷却塔整体下座,未能按照设计倾倒。事后采用机械拆除成功排除了冷却塔危险倾斜体,并分析了此次冷却塔爆破拆除失败原因。     

复杂环境下110 m冷却塔控制爆破拆除

介绍了一座高110 m的薄壁钢筋混凝土冷却塔的定向控制爆破拆除。针对冷却塔高度大、塔壁薄以及底部直径大的特点,采用“开窗口、断钢筋、预留支撑板块”爆破方案,预拆除中通过对冷却塔爆破缺口进行优化设计,在爆破边沿开设2个简化的定向窗。在爆破区域仅对冷却塔人字柱底部和顶部进行布孔爆破,将爆破切口分为5个起爆区域采用分区分段的非电毫秒延期起爆技术。为了有效控制爆破危害效应,在冷却塔倒塌方向铺设缓冲土层及钢板进行双重防护有效地降低了塌落冲击振动,在爆破切口处采用密目网和土工格栅覆盖相结合的防护措施有效地控制了飞石,未对周围建(构)筑物造成损害。爆破效果表明：在爆破切口边沿开设2个简化的定向窗窗口,不仅减少了钻孔及相关工作量,降低了安全隐患和防护难度,而且提高了预处理部分的结构稳定性,防止爆破切口处下坐;通过对定向窗的简化设计,使得冷却塔在倾倒过程中发生扭曲充分解体,爆堆较为集中,触地振动较小,爆破效果良好。     

复杂环境61 m高双曲线冷却塔拆除爆破

为成功拆除复杂环境下1座61 m高的冷却塔,根据其周边环境及结构特点,采用定向倒塌方案。首先采用机械方法开设定向窗和减荷槽,随后对19对人字柱进行爆破,使用毫秒延时爆破技术,控制单段起爆药量,成功完成拆除爆破。对拆除爆破后冷却塔的倒塌情况进行分析,冷却塔按照设计方向倒塌,解体完全,爆破振动以及触地振动控制在合理范围之内。爆破后周边民房、办公室等设施未损坏,证明本次拆除爆破效果良好,达到了预期效果,可为类似工程提供参考。     

冷却塔高卸荷槽切口爆破拆除倒塌受力破坏过程研究

结合数值仿真结果和大量工程实践摄影资料,对冷却塔高卸荷槽切口爆破拆除倒塌受力破坏机理进行了分析。研究结果表明:冷却塔高卸荷槽切口爆破拆除倒塌过程可分为爆破切口形成、定向偏转下坐切口闭合、塔体初始触地高卸荷槽切口变形破坏、塔体二次变形破坏和塔体随机解体塌落触地5个阶段。爆破切口形成后,保留支撑人字柱临时中性轴形成,在冷却塔定向偏转过程中中性轴逐渐后移,人字柱在轴力、弯矩、剪力和扭矩的共同作用下发生稳定失效、破坏且各对人字柱左右柱受力存在明显差异。塔体的变形破坏由高卸荷槽切口压屈剪切破坏向塔体拉伸挤压力与触地冲击作用反力共同作用破坏或塔体拉伸挤压破坏转变,这与冷却塔结构质量优劣、卸荷槽高度、结构不对称受力等因素有着重要关系。     

复杂环境61m高双曲线冷却塔拆除爆破

为成功拆除复杂环境下1座61 m高的冷却塔,根据其周边环境及结构特点,采用定向倒塌方案.首先采用机械方法开设定向窗和减荷槽,随后对19对人字柱进行爆破,使用毫秒延时爆破技术,控制单段起爆药量,成功完成拆除爆破.对拆除爆破后冷却塔的倒塌情况进行分析,冷却塔按照设计方向倒塌,解体完全,爆破振动以及触地振动控制在合理范围之内.爆破后周边民房、办公室等设施未损坏,证明本次拆除爆破效果良好,达到了预期效果,可为类似工程提供参考.     

2座90m高的双曲线冷却塔爆破拆除

介绍了2座高90.0m、底部直径73.6m、顶部直径43.0m的钢筋混凝土冷却塔的定向控制爆破拆除。针对冷却塔高度大、自下而上筒壁由厚变薄,整体性强,冷却循环水淋水装置支柱基础呈分离布置的特点,对设计的减荷槽进行结构校核确保稳定后,采用开凿减荷槽的方法,将倾倒方向上炸高以上的筒壁由连续薄壁结构转变成独立薄壁结构,对淋水装置支柱基础进行预拆除;采用计算机软件模拟人字柱的受力分析,选择合理的开口角度和合适的钻孔布置。对人字柱钻孔装药位置使用炮被和竹跳板进行爆破飞石近体防护,收集淋水平台预拆除时的淋水格栅,并利用其多层多孔的特点,用作爆破防护和隔音吸能,使用多段毫秒延时导爆管雷管起爆网路,逐渐对称地形成爆破切口,确保冷却塔在下坐前和下坐的过程中按预定的倾倒方向倒塌并解体,由此实现了2座冷却塔的定向爆破拆除。     

110m高冷却塔爆破拆除

介绍了复杂环境下110 m高钢筋混凝土冷却塔的爆破拆除。对塔体倒向侧21对X型支撑柱进行重点布孔,对圈梁、塔壁进行局部布孔,在塔壁开设矩形减荷槽及三角形定向窗,形成上下2个正梯形爆破切口。上切口上、下沿对应圆心角分别为216°、223°,下切口上、下沿对应圆心角分别为180°、198°,倒向中心线处切口高度为20.5 m,两侧切口高度为18.5 m。爆破后塔体沿西北向定向倾倒、坍塌,塌落物最远处距塔体倒向下沿47.5 m,塔体破碎效果良好。     

预拆除对薄壁双曲型冷却塔爆破拆除的影响

针对贵阳发电厂内冷却塔是由钢筋混凝土构成的薄壁双曲型圆筒,具有底部直径大,垂直高度高,塔壁外部没有施工条件且周边环境较为复杂的特点,采用预拆除技术,以确保冷却塔爆破拆除顺利实施并取得良好的效果。预拆除技术主要由3个部分组成:冷却塔内部支撑、倒塌方向薄壁的减荷槽以及倒塌反向的泄压窗。通过理论计算设计出正梯形爆破切口的参数,在人字形柱上同时采用开设减荷槽(13个)的方法,来保证冷却塔筒壁在倒塌过程中的屈服破碎效果,为了进一步减小爆炸冲击波对冷却塔筒壁的破坏作用,在倒塌方向的反方向开出一个2m×4m的矩形泄压窗。根据现场实验结果和冷却塔整体爆破效果,预拆除技术对薄壁双曲型冷却塔爆破起到了良好的作用,达到了冷却塔整体失稳倒塌,精确定向以及整体不下坐的效果。     

两座90m高冷却塔控制爆破拆除

介绍了复杂环境下采用控制爆破拆除技术成功爆破拆除两座90m高冷却塔的工程实例。通过在倒塌方向塔身布置10m高卸荷槽和三角形定向窗组成的复合切口,并对预处理后冷却塔稳定性进行校核,确定合理的爆破参数和起爆网路,仅对24对人字柱实施爆破拆除,实现了冷却塔边倾倒边解体。同时采取开挖减振沟和铺设缓冲垫层等安全防护措施,使冷却塔倒塌触地振动得到有效控制,取得了理想的爆破效果,可为同类工程提供参考。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.