考虑转速比影响的砂土中螺旋挤扩钻具成孔特性宏细观模型试验  

Experimental study of the effect of drilling velocity ratio on the behavior of auger piling in sand

作　　者：史旦达 杨彦骋 邓益兵 刘文白 SHI Dan-da;YANG Yan-cheng;DENG Yi-bing;LIU Wen-bai(College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China;Shanghai Waterway Engineering Design and Consulting Co., Ltd., Shanghai 200120, China)

机构地区：[1]上海海事大学海洋科学与工程学院,上海201306 [2]中交上海航道勘察设计研究院有限公司,上海200120

出　　处：《岩土力学》2018年第6期1981-1990,1998,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.41772273;No.51609315;No.51208294)~~

摘　　要：以福建标准砂为材料,采用宏细观模型试验方法,分析了转速比对松砂和密砂地基中螺旋挤扩钻具成孔特性的影响。宏观上,研究了竖向阻力、扭矩和土体应力随贯入深度的变化规律;细观上,结合环氧树脂砂土固化方法与数字图像分析技术,探讨了孔周土体相对密实度变化及其组构演化规律。试验结果表明,无论松砂还是密砂,钻具贯入时的竖向阻力、扭矩及孔周土体最大径向应力均随着转速比的增加而减小;钻具贯入导致松砂地基中钻头深度和孔周土体均发生挤密,而对于密砂则均发生不同程度的体胀;无论松砂还是密砂,孔周砂土切块环向面上的接触法向各向异性程度均随着转速比的增加而减小,而转速比对其径向面上的接触法向各向异性分布影响不大。该试验结果有助于提升对螺旋挤土桩成孔过程宏细观机制的认识。The effect of drilling velocity ratio, the ratio between the rotation and the penetration velocity, on the boring mechanism of auger piling was investigated with a series of model tests on both loose and dense Fujian standard sands. The variation of reaction force and rotational moment of the auger with the penetration depth, and the induced vertical and radial stresses within the soils during auger penetration were analyzed at the macro level. The variation of sand relative density and the evolution of soil fabric due to auger penetration were microscopically examined using the epoxy resin solidifying method and the digital image analyzing technique. It is found that the reaction force, the rotational moment and the induced maximum radial stress decrease with the increment of drilling velocity ratio, independent on soil initial density. In loose sand, the soils at the auger tip and around the borehole exhibits contraction behavior, whilst the dilation behavior is captured in dense sand. The extent of contact normal anisotropy on the circumferential cutting face of the solidified sand block reduces with the increment of drilling velocity ratio, yet the distribution of contact normal on the radial cutting face is not significantly affected by the drilling velocity ratio. This regularity is independent of the soil＇s initial density.

关 键 词：螺旋挤土桩 挤扩钻具 转速比 砂土 室内模型试验 

分 类 号：TU473.1[建筑科学—结构工程]