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A MODEL STUDY OF PILE GROUP RELAXATION FOR PILES BEARING IN DISCONTINUOUS ROCK.

机译：间断岩体中桩基松弛的模型研究。

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摘要

This thesis investigates the relaxation of pile groups driven into bedrock using model simulation. Model piles were driven into a simulated discontinuous rock mass with an impact hammer. Relaxations were measured both as a loss of load capacity under static loading, and also as additional penetration during redriving. Similitude of the model experiments with the full-scale condition was verified using dimensional analysis and by comparison with actual field data.;The effects of several experimental parameters on the degree of relaxation were examined for pipe piles. Correlations with driving order, relative tip penetration, and vertical heave were developed. The degree of relaxation was found to be inversely proportional to pile spacing and group size. The maximum radius of influence for a five pile group was estimated by extrapolation to be 8 to 10 pile diameters. Group efficiencies were computed taking into account the observed relaxations. Up to 40% reductions in group load capacity were estimated for relaxed pile groups compared with unrelaxed groups.;A limited amount of testing was performed with model H-piles. H-piles were found to be much less susceptible to relaxation than pipe piles, but they exhibited significantly less ultimate load capacity.;The primary mechanisms of relaxation in the rock mass were identified as: (1) fracturing and pulverization; (2) lateral and vertical displacement; (3) reduction in lateral stress; and (4) vibration.;The model piles had nominal diameters of 1 inch and the simulated rock blocks had an average compressive strength of 3200 psi. Test measurements were made electronically and recorded on a microcomputer controlled data acquisition system.;The dynamic bearing capacity of the pipe piles during driving was evaluated using both force-velocity integrations and the wave equation. The observed dynamic capacity ranged between 2.0 and 3.0 times the unconfined compressive strength of the model rock mass.;Recommendations for detecting and remediating relaxation in the field are presented based on the case histories and the results of the experimental study. Suggestions are made for future research in the areas of pile group relaxation and rock bearing capacity.
机译：本文利用模型仿真研究了打入基岩的群桩的松弛。用冲击锤将模型桩打入模拟的不连续岩体中。松弛既可以作为静态载荷下的载荷能力损失来衡量，也可以作为重行期间的附加穿透来测量。通过尺寸分析并与实际数据进行比较，验证了在满量程条件下进行模型试验的相似性。；研究了多个试验参数对管桩松弛度的影响。与驱动顺序，相对尖端穿透和垂直起伏的相关性得到发展。发现松弛程度与桩间距和组大小成反比。通过推算得出，五个桩组的最大影响半径为8到10个桩直径。计算组效率时要考虑到观察到的松弛。与不放松的组相比，放松的桩组估计可减少多达40％的组承载能力。用H型桩进行有限量的测试。发现H桩比管桩对松弛的敏感性要低得多，但它们表现出的极限承载力却要低得多。岩体松弛的主要机理被确定为：（1）破碎和粉碎； （2）横向和纵向位移； （3）减少侧向应力； （4）振动。模型桩的公称直径为1英寸，模拟的岩石块的平均抗压强度为3200 psi。以电子方式进行测试测量，并将其记录在微机控制的数据采集系统上。使用力-速度积分和波动方程式评估驱动过程中管桩的动态承载能力。观测到的动态承载能力是模型岩体无侧限抗压强度的2.0到3.0倍。；基于实例历史和实验研究结果，提出了检测和补救野外松弛的建议。提出了在桩群松弛和承载力方面的未来研究建议。

著录项

  • 作者

    SCHURING, JOHN ROBERT, JR.;

  • 作者单位

    Stevens Institute of Technology.;

  • 授予单位 Stevens Institute of Technology.;
  • 学科 Ocean engineering.
  • 学位 Ph.D.
  • 年度 1987
  • 页码 248 p.
  • 总页数 248
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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