组合锤置换墩极限承载力计算方法

为研究组合锤置换法加固软土地基的承载性能,需建立置换墩的极限承载力计算模型并验证该计算方法的可行性.首先,进行室内模型试验,研究置换墩墩体形态和墩体破坏模式.其次,在模型试验的基础上,根据能量法建立置换墩极限承载力的计算模型,代入模型相关参数,基于GA_PSO优化算法在Matlab平台研究各参数对墩体极限承载力的影响.试验和计算结果表明:置换墩典型的墩体形态为一轴对称的旋转体,纵向剖面为上大下小的梯形截面;极限状态下墩体的破坏模式为鼓胀破坏;墩径和墩周土体强度对提高墩体极限承载力影响显著,此与组合锤置换法设计理念相吻合.最后,通过一工程案例,验证了该计算方法应用于组合锤置换法初步设计是可行的.     

复合变质处理高铬铸铁破碎机锤头的研制

介绍了复合变质处理高铬铸铁的化学成分、变质处理工艺、变质处理后高铬铸铁的组织和力学性能的变化以及采用复合变质处理高铬铸铁生产破碎机锤头的生产工艺和使用性能.工业实验表明,复合变质处理高铬铸铁锤头的耐磨性约是高锰钢锤头的4倍.     

Pile Driving Analysis for Top Hammering and Bottom Hammering

Piles are used for platform foundations and other offshore structures. Pile driving performance is predicted and analyzed using the wave equation analysis method. In general, the hammering point can be any part of the pile and the same analyses used for hammering at the top of the pile (top hammering) can be used for pile driving by hammering at the bottom of the pile (bottom hammering). Based on the numerical analyses in this research including residual stresses in the pile, there is little difference between the predictions of pile penetration per hammer blow by single- or multiple-blow analyses when soil resistance is low, such as 10 blows/m. The same is true for top hammering and bottom hammering when soil resistance is low. However, when soil resistance is high compared to that of the pile-hammer system, single-blow analysis predicts early refusal for top hammering and unrealistically high pile penetration for bottom hammering. Therefore, multiple-blow analysis, which considers residual stresses, should be used for better understanding of realistic pile driving performance and predictions. Additionally, this study shows that gravity is another controlling factor for pile driving in low-resistance soil.     

液压破碎锤高压胶管的仿真研究

取消液压破碎锤的高压蓄能器已经成为一种趋势。在无高压蓄能器的液压破碎锤中,进油高压胶管起到了高压蓄能器的作用。为了研究进油高压胶管对液压破碎锤工作性能的影响,提高液压破碎锤的使用寿命,对进油高压胶管的数学模型进行了分析,利用AMESim软件中的管道模型和液压元件设计库,搭建液压破碎锤的仿真模型,对进油高压胶管在液压破碎锤工作时的作用进行仿真分析。仿真结果表明：进油高压胶管是液压破碎锤前腔压力产生波动的原因之一,进油高压胶管的长度和内径对液压破碎锤的工作性能均有影响。     

高频振动打桩对邻近基桩影响分析

为解决在城市里桩基施工引起的环境问题,国外开发并推广应用了高频液压振动锤技术。通过有限元软件Abaqus对高频振动打桩对邻近桩基影响进行模拟。模拟中桩轴线处建立半径为1mm的管,管土接触设为光滑,打桩时土管分离,桩随着管向下贯入,形成打入桩和周围土体之间的接触关系。打入桩和圆管采用刚体模拟,土体单元则采用摩尔库伦本构模型,建立高频打桩的三维模型,很好的实现高频液压振动沉桩整个过程的数值分析。贯入模拟过程表明打入桩桩尖深度处有应力集中现象;离打入桩越远,受到的影响越小。且分析表明高频振动打桩对邻近桩基的影响很小。     

基于PLC的螺杆桩机立柱油缸的同步控制

针对原螺杆桩机立柱油缸开环控制系统性能不稳定、人工操作实时性差及油缸同步误差大等缺陷,设计基于PLC的立柱油缸同步闭环控制系统,并在新型螺杆桩机上得到应用。闭环控制系统的硬件组成有立柱油缸、磁致伸缩位移传感器及SIEMENS公司的S7-200可编程控制器等。现场调试实验表明:设计的立柱油缸闭环控制系统实现了桩机立柱的数字控制,举升与下落过程自动纠偏,同步控制精度达到±2 mm,控制系统性能稳定,安全便捷,具有工程实用价值。     

深孔液动潜孔锤钻进技术研究与应用

液动潜孔锤钻探以冲击动载和回转切削相结合的方式进行岩石破碎,在中硬以上的弹塑性岩石和脆性岩石中可有效地提高钻探效率、延长钻头的使用寿命、提高回次进尺、提高岩芯采取率、减少钻孔弯曲、节约生产成本.但传统的液动潜孔锤适用的钻孔口径小、钻孔浅以及存在着诸多弊端,不能满足越来越深的钻探工作需要.新型高效系列液动锤以创新工作原理...     

碟簧在锻锤基础隔振改造中的应用

通过对某厂锻锤隔振基础改造的工程实践，简要介绍了碟簧在锻锤隔振基础改造中的应用，并对碟簧有关参数选择、组合方式及反压限幅等问题进行了探讨。     

Cr12型模具钢成材工艺改进

本文从理论上分析了Cr12型冷作模具钢在加热和锻造过程中客易产生缺陷的原因，并结合其它钢种的联锻工艺特性，对Cr12型冷作模具钢的二火成材工艺进行了改进，改进后的工艺为“两锤联锻、一次成材”。工艺改进后，不但增加了锻材长度和提高了产品实物质量，而且降低了加工步骤费用和缓解了退火压力、为模具钢放量生产起到了显著的作用。     

The performance prediction of impact hammers from Schmidt hammer rebound values in Istanbul metro tunnel drivages

The construction of the first metro line in Istanbul was realized between Galata and Beyoglu by a French Engineer Henry Gavand in January 1875. Six different metro projects were submitted since then to the Turkish authorities. The construction of 7-km metro tunnels phase 1 started in 1992 and the metro line of the phase 1 is opened to the service in 2000. The tunnels of the phase 2 between Taksim and Yenikapi are under construction. This paper summarizes the construction methods of the Istanbul metro tunnels, the performance of the impact hammers, the factors effecting daily advance rates and the previous studies on Schmidt hammer test and performance prediction of impact hammers. At the end, a prediction model concerning instantaneous breaking rates of hydraulic impact hammers from Schmidt hammer rebound values is explained in detail.