摘要
针对螺旋挤土桩钻具成孔过程对地基土产生的影响,利用自行设计的可视化模型装置,在均质砂土地基中,进行螺旋挤扩钻具下旋成孔过程模型试验探讨成孔机制。从宏观上分析螺旋挤扩钻具掘进过程中孔侧土体径向位移和环向剪切位移规律,以及土体应力场的变化规律;在细观层面,通过分析与钻具作用的土体组构演化规律,探讨钻具挤扩土体的细观机制。试验结果表明:螺旋挤扩钻具下旋挤扩对土体的影响与竖向应力相关,竖向应力越大,土体径向位移传递得更远,土体的径向位移主要产生在2.5倍钻径范围内,孔壁附近土体产生显著环向剪切位移,孔侧土体应力变化过程表现为加载-卸载-加载的过程,与钻具接触宽度约为5倍平均颗粒粒径区域的颗粒发生显著旋转,砂土颗粒与钻具接触由点面接触逐渐发展为面面接触,细观组构向同向性趋势演化。研究成果对进一步研究螺旋挤土钻具挤土扩孔机制以及螺旋挤土桩桩侧土体的宏细观力学特性都具有一定意义。
Aiming at the impact of augered piling on ground soil, model tests on augered piling of screw displacement auger in homogeneous sand are conducted by self-designed visualization model device. The mechanism for development of borehole is discussed. The displacement behaviors and stress development of soil nearby the borehole are analyzed in macro-scale during augered piling. The mesomechanism of interaction between auger and soil is studied by evolution of sand micro-fabric parameters. The model test results show that impact of augered piling on ground soil depends on vertical stress. The higher the vertical stress is, further the radial displacement in the soil transfers. Radial displacement of soil is mainly within 2.5 times of the auger diameter, accompanying with the significant hoop shear displacement of soil nearby the borehole. The soil nearby the borehole experiences the process of loading-unloading-loading. The sand particles in the area that auger contact width is approximately 5 times of the average particle diameters occur significant rotation. The point contact between sand particles and auger develops gradually surface contact with the evolution of isotropy on micro structure. The study results have some significance to disclose the mechanism of augered piling and macro-meso mechanical properties of soil nearby the borehole for the soil displacement screw pile.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2011年第12期2558-2566,共9页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51078228)
上海海事大学校基金项目(20100074)
上海高校选拔培养优秀青年教师科研专项基金(shs10074)
关键词
桩基工程
螺旋挤土桩
下旋成孔
模型试验
细观机制
pile foundations
soil displacementscrewpile
augeredpiling
model test
mesomechanism
