A series of well-designed full-scale destructive load tests were conducted on six bored piles to investigate the influence of loose debris at the pile tip on end resistance. The results show that soft debris below the...A series of well-designed full-scale destructive load tests were conducted on six bored piles to investigate the influence of loose debris at the pile tip on end resistance. The results show that soft debris below the pile tip will weaken the mobilization of end resistance. The ultimate tip resistance of post-grouted pile is 2.05 times that of the pile without post-grouting and the ultimate tip resistance in the second load cycle is 2.31 times that of pile in the first load cycle. The relationship between unit end resistance and displacement follows a linear model and a bilinear mode in the first load cycle and the second load cycle, respectively, whereas the unit end resistance-displacement response of post-grouted bored pile can be simulated using a bilinear mode. The critical end resistance ranges between 2 000 kN and 3 000 kN and the critical displacement ranges between 2.5 mm and 4.5 mm in the bilinear mode. As for piles rested on moderately-weathered peliticsiltstone, the socketed length has no effect on the end resistance because of the existence of loose debris.展开更多
This study presents a laser-sheet imaging technique to measure the water surface of free overfalls with plunge pool. Varying the plunge pool length of a constant approach discharge created skimming, periodic oscillato...This study presents a laser-sheet imaging technique to measure the water surface of free overfalls with plunge pool. Varying the plunge pool length of a constant approach discharge created skimming, periodic oscillatory, and nappe flows. This study analyzes the resulting oscillating water surfaces and temporal variations of water stages at particular positions in the periodic oscillatory flow condition. The oscillation period and amplitude of temporal water stage variation were determined by directly measuring the time interval and water stage differences in water stage variations, respectively. The plunge pool length and air pocket characteristics seriously affected the periodic oscillatory flow. The oscillation period increased as the plunge pool length increased. On the other hand, the water stage amplitude decreased sharply when the plunge pool exceeded a specific length. The absence of an air pocket beneath the falling nappe significantly increased the oscillation period and decreased the water stage amplitude. This study investigates water surface oscillation in the plunge pool and the upstream side of the drop. However, the mean end depth of a periodic oscillatory flow with an air pocket is also applicable to discharge estimation using the end depth method.展开更多
A deduced cutting force prediction model for circular end milling process is presented in this paper. Traditional researches on cutting force model usually focus on linear milling process which does not meet other cut...A deduced cutting force prediction model for circular end milling process is presented in this paper. Traditional researches on cutting force model usually focus on linear milling process which does not meet other cutting conditions, especially for circular milling process. This paper presents an improved cutting force model for circular end milling process based on the typical linear milling force model. The curvature effects of tool path on chip thickness as well as entry and exit angles are analyzed, and the cutting force model of linear milling process is then corrected to fit circular end milling processes. Instantaneous cutting forces during circular end milling process are predicted according to the proposed model. The deduced cutting force model can be used for both linear and circular end milling processes. Finally, circular end milling experiments with constant and variable radial depth were carried out to verify the availability of the proposed method. Experiment results show that measured results and simulated results corresponds well with each other.展开更多
为了研究VSM沉井井壁受力变化规律,结合施工工艺特点对VSM沉井的下沉过程及受力特性进行了分析。首先,依据VSM沉井下沉特点对其施工过程中所受荷载进行梳理,同时划分了沉井一个下沉循环中的典型运动状态;之后以G. G. Meyerhoff公式和规...为了研究VSM沉井井壁受力变化规律,结合施工工艺特点对VSM沉井的下沉过程及受力特性进行了分析。首先,依据VSM沉井下沉特点对其施工过程中所受荷载进行梳理,同时划分了沉井一个下沉循环中的典型运动状态;之后以G. G. Meyerhoff公式和规范为基础,对沉井下沉阻力进行分析计算,提出了考虑井内淹水的刃脚端阻力计算公式,并建立了井壁典型状态施工力学模型;最后,以矿山竖井工程为算例计算得出沉井几何参数、下沉阻力、下沉深度以及悬吊力之间的关系。结果表明:VSM沉井悬吊力大小随着下沉深度的增加并不是一直增大的,而是先增大后减小,存在极大值;井壁厚度直接影响着刃脚端阻力大小和侧壁摩阻力变化规律,进而间接影响沉井的下沉深度;沉井悬吊力大小随着施工条件的变化而变化,对于沉井设备悬吊能力的设计应根据实际情况进行综合考虑;对于内径6m,厚度0.5m的矿山沉井井壁,在f=8kPa条件下,其最大下沉深度为56m;根据下沉深度设计减阻泥浆性能是控制下沉阻力、实现系统优化的重要手段。展开更多
基金Project(51078330) supported by the National Natural Science Foundation of ChinaProject(2012MS21339) supported by China Postdoctoral Science FoundationProject(2012GN012) supported by the Independent Innovation Foundation of Shandong University, China
文摘A series of well-designed full-scale destructive load tests were conducted on six bored piles to investigate the influence of loose debris at the pile tip on end resistance. The results show that soft debris below the pile tip will weaken the mobilization of end resistance. The ultimate tip resistance of post-grouted pile is 2.05 times that of the pile without post-grouting and the ultimate tip resistance in the second load cycle is 2.31 times that of pile in the first load cycle. The relationship between unit end resistance and displacement follows a linear model and a bilinear mode in the first load cycle and the second load cycle, respectively, whereas the unit end resistance-displacement response of post-grouted bored pile can be simulated using a bilinear mode. The critical end resistance ranges between 2 000 kN and 3 000 kN and the critical displacement ranges between 2.5 mm and 4.5 mm in the bilinear mode. As for piles rested on moderately-weathered peliticsiltstone, the socketed length has no effect on the end resistance because of the existence of loose debris.
文摘This study presents a laser-sheet imaging technique to measure the water surface of free overfalls with plunge pool. Varying the plunge pool length of a constant approach discharge created skimming, periodic oscillatory, and nappe flows. This study analyzes the resulting oscillating water surfaces and temporal variations of water stages at particular positions in the periodic oscillatory flow condition. The oscillation period and amplitude of temporal water stage variation were determined by directly measuring the time interval and water stage differences in water stage variations, respectively. The plunge pool length and air pocket characteristics seriously affected the periodic oscillatory flow. The oscillation period increased as the plunge pool length increased. On the other hand, the water stage amplitude decreased sharply when the plunge pool exceeded a specific length. The absence of an air pocket beneath the falling nappe significantly increased the oscillation period and decreased the water stage amplitude. This study investigates water surface oscillation in the plunge pool and the upstream side of the drop. However, the mean end depth of a periodic oscillatory flow with an air pocket is also applicable to discharge estimation using the end depth method.
基金co-supported by Open National Natural Science Foundation of China(No.51005183)National Science and Technology Major Project(No.2011ZX04016031)China Postdoctoral Science Foundation(No.2012M521804)
文摘A deduced cutting force prediction model for circular end milling process is presented in this paper. Traditional researches on cutting force model usually focus on linear milling process which does not meet other cutting conditions, especially for circular milling process. This paper presents an improved cutting force model for circular end milling process based on the typical linear milling force model. The curvature effects of tool path on chip thickness as well as entry and exit angles are analyzed, and the cutting force model of linear milling process is then corrected to fit circular end milling processes. Instantaneous cutting forces during circular end milling process are predicted according to the proposed model. The deduced cutting force model can be used for both linear and circular end milling processes. Finally, circular end milling experiments with constant and variable radial depth were carried out to verify the availability of the proposed method. Experiment results show that measured results and simulated results corresponds well with each other.
文摘为了研究VSM沉井井壁受力变化规律,结合施工工艺特点对VSM沉井的下沉过程及受力特性进行了分析。首先,依据VSM沉井下沉特点对其施工过程中所受荷载进行梳理,同时划分了沉井一个下沉循环中的典型运动状态;之后以G. G. Meyerhoff公式和规范为基础,对沉井下沉阻力进行分析计算,提出了考虑井内淹水的刃脚端阻力计算公式,并建立了井壁典型状态施工力学模型;最后,以矿山竖井工程为算例计算得出沉井几何参数、下沉阻力、下沉深度以及悬吊力之间的关系。结果表明:VSM沉井悬吊力大小随着下沉深度的增加并不是一直增大的,而是先增大后减小,存在极大值;井壁厚度直接影响着刃脚端阻力大小和侧壁摩阻力变化规律,进而间接影响沉井的下沉深度;沉井悬吊力大小随着施工条件的变化而变化,对于沉井设备悬吊能力的设计应根据实际情况进行综合考虑;对于内径6m,厚度0.5m的矿山沉井井壁,在f=8kPa条件下,其最大下沉深度为56m;根据下沉深度设计减阻泥浆性能是控制下沉阻力、实现系统优化的重要手段。
