桩基础施工新技术专题讲座(十二)泵吸反循环钻成孔灌注桩

反循环钻成孔灌注桩基本原理反循环钻成孔施工法是在桩顶处设置护筒（护简直径应比桩径大15%左右）,护筒内的水位要高出自然地下水位2 m以上,保持孔壁的静水压力在0.02 MPa以上,以保护孔壁不坍塌,省去切削套管。钻机工作时,旋转盘带动钻杆端部的钻头切削破碎岩土;钻进冲洗液（又称循环液,指水或泥浆）从钻杆与孔壁间的环状空间中流入孔底,冷却钻头,并携带岩土钻渣,混合液在负压作用下从钻杆内腔上升到地面溢进沉淀池后返回泥浆池中净化,净化后的冲洗液又返回孔内形成循环,这种钻进方法称为反循环钻进。     

桩基础施工新技术专题讲座(二十八) 冲击反循环钻成孔灌注桩(上)

基本原理冲击反循环钻进工艺如下,是使用2根钢丝绳通过提引盘对称地提引冲击钻头,提引盘可在钻头中心管体上相对转动。在冲击液压缸的作用下,通过同步卷筒的自动调节机构,2根钢丝绳在工作状态时始终受力相等,在2根钢丝绳中空处设置排渣管,通过钻头中心管下入孔底,在钻头上下往复运动冲击破碎岩石时,用地表的砂石泵实现泵吸反循环。这样,钻头在孔底进行冲击钻进的同时,通过泵吸反循环将钻渣由孔底经排渣管、砂石泵排到地表的泥浆池中,钻渣沉淀完成渣浆分离后泥浆经过泥浆     

凿岩机械与气动工具

GJ20064149贯通式潜孔钻头钻进复杂地层防卡堵试验研究[刊,中]/王如生…//煤矿机械.—2005,(7).—40～43贯通式潜孔锤反循环连续取心(样)钻进技术作为一项高新技术,在实际施工中经常遇到复杂地层(如坚硬破碎地层、卵砾石地层和溶洞地层),尤其在我国西部,钻进过程中经常发生一些     

径向水平井自进式旋转射流钻头流场特性分析

为解决径向水平井钻进过程中破岩效率和自进能力的问题,设计了一种自进式旋转射流钻头。运用数值模拟方法,采用RNG k-ε湍流模型对所设计射流钻头的内外流场进行了三维流动特性分析,并分析了射流钻头结构参数对喷嘴流场特性的影响规律,进一步优化了自进式旋转射流钻头。结果表明,自进式旋转射流喷嘴外流场的轴心速度在喷嘴中心线上的速度最大,随着径向半径的增大,轴向速度迅速减小;切向速度沿喷嘴径向呈现出经典的"N"形分布,有利于增大射流破碎岩石的深度和破碎面积;径向速度呈轴对称分布,存在明显的漫流层,有助于岩屑的脱离;自进式旋转射流钻头导向叶轮的螺距和导叶数量,对射流速度有着重要的影响;喷嘴直径对射流流场特性的影响较大。经过优化,得到射流钻头的叶轮螺距16mm,导叶数为2,喷嘴直径为1mm。     

煤层取心钻进用钻头的优选与实践应用

设计和加工3种类型的煤层取心用钻头,并将设计的取心钻头在山西潞安集团左权阜生煤业进行了实践应用。现场应用效果表明:当钻进遇煤层夹矸时,选用先导式PDC钻头,能可明显提高钻进效率,并保证煤层取心质量;煤层中取心钻进时,选用平底型硬质合金钻头,采用干钻取心钻进,可以提高煤心采取率和煤心质量。其中选择压力为7～10 kN、转速为80 r/min以内、冲洗液量为80 L/min以内的钻进工艺参数。     

牙轮钻头用深穴空心滚子轴承的数值研究

牙轮钻头中轴承系统与硬质合金镶齿钻头牙齿的寿命不匹配,成为制约其使用寿命的一个重要因素。为此,在牙轮钻头用空心圆柱滚子轴承的基础上,设计了一种深穴空心滚子轴承,除了具备空心结构滚子的优点外,避免了在滚子端部出现应力集中现象。同时,建立了不同结构滚子轴承的有限元模型,进行了应力分析,并研究了深穴深度和深穴直径对滚子力学性能的影响。结果表明:深穴空心滚子的力学性能优于实心滚子、空心滚子和深穴滚子;随着深穴深度和深穴直径的增大,滚子两端的等效应力和接触应力逐渐减小,而中间部位的应力却逐渐增大;以Ф215.9 mm牙轮钻头滚动轴承为例,建议其深穴直径为7 mm,深穴深度为2 mm较为适宜。最后,设计了一种填充式复合滚子轴承,可以有效地提高轴承的疲劳寿命,建议在钻进过程中可以根据不同地层合理选择轴承滚子结构。     

桩基础施工新技术专题讲座（二十二）气动潜孔锤反循环钻孔灌注桩（下）

（接上期） 气动潜孔锤反循环钻孔灌注桩钻进工艺 大直径潜孔锤钻进技术是解决嵌岩桩孔尤其是硬地层极有效的钻进方法，美国、日本、英国及韩国等国也都开展了这方面的研究工作，并已形成产品，在工程实际应用中均取得了理想效果。     

一种新型旋流萃取器的研究

介绍了一种用旋流器进行液液萃取--旋流萃取的新型旋流萃取器的结构、原理、理论分析及初步试验结果.与传统的离心萃取器相比,旋流式离心萃取器没有运动部件,结构紧凑,制造维护方便.研究结果表明,直径为20mm的旋流萃取器可以在数秒时间内达到某些物料萃取平衡的95%以上.     

仿生多瓣式锥型月壤钻采机构研究

针对月球表面钻孔勘探的需求,基于竹象虫钻食竹笋和蚯蚓在土壤中蠕动前进的机理,设计了一种集钻探、采样和储样功能于一体的可开闭、蠕动进给的仿生多瓣式钻采机构。钻采机构采用分段式设计,由分瓣式锥形钻头、主机架和副机架3个部分组成。针对分瓣式锥形钻头的不同部位进行力学和钻进排屑性能分析,建立了钻头与月壤相互作用力学模型,并以此为基础对钻头结构参数进行优化设计。研究结果表明,锥形基体所受的径向挤压力与半锥角成反比。     

轴流压气机进气旋流畸变实验与仿真研究

为深入分析旋流畸变问题,发现叶片式旋流畸变发生器产生旋流流场的机理和旋流畸变对压气机稳定性的影响机制,本文开展了旋流畸变发生器与压气机的耦合数值仿真。分析计算结果,认为叶尖脱落涡的叠加效应是产生旋流的主要机理,旋流结构对转子叶尖区域的扰流作用是造成转子提前失速的重要原因。建立了S弯进气道仿真模型,通过对S弯进气道与高亚声速压气机进行耦合仿真计算,研究了S弯进气道出口旋流流场的形成机制,初步探讨了S弯进气道出口旋流流场对压气机稳定性的影响。S弯进气道出口形成的对涡结构靠近压气机机匣,这种局部的涡结构会影响部分转子叶片叶顶区域的流动结构,从而导致压气机失速边界右移。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.