矩形与圆形截面抗滑桩离心模型试验及颗粒流数值模拟研究

发布时间：2018-05-28 23:29

  本文选题：抗滑桩 + 桩土相互作用　； 参考：《西南交通大学》2017年硕士论文

【摘要】：抗滑桩作为一种非连续性支挡结构,依靠桩身及桩间土拱实现连续支挡作用。根据施工工艺不同,桩身有矩形、圆形等多种截面形式。其中矩形截面形式简单,受力性能较好,在实际工程中较为常用。近几年来,随着对施工效率的要求提高和施工机械性能发展,与机械成孔工艺相配套的圆形抗滑桩也开始得到广泛应用,但目前对圆形桩的受力变形特性、桩土相互作用特征等工作机理尚不明确。在总结分析已有桩土相互作用理论、试验和数值模拟研究成果的基础上,分别采用等抗弯刚度条件下矩形与圆形抗滑桩土工离心模型试验,研究比较了两类桩型的荷载响应及桩土传力特征差异;并通过二维颗粒流数值计算,分析了桩间距的影响,讨论了抗滑桩的桩土整体承载力、桩间土拱效应及桩土荷载分担比,初步得到了以下结论:(1)在土工离心模型试验中,随滑坡推力逐级加载,相对于圆形桩,矩形桩桩间土体整体移动较更小,桩间土先整体块状后呈散碎状剥落形成土拱,依靠土体与桩迎土面相互挤压形成拱脚,剥落掉的桩间土整体呈块状,侧面光滑并呈上宽下窄倒梯形;圆形桩周围土体整体移动较矩形桩大,桩间土呈大量散碎状剥落,桩周土沿桩身侧面出现绕流现象,土拱现象相对不明显。(2)在离心场逐级加载的滑坡推力作用下,通过元器件测试出圆形桩的桩顶位移约为等截面抗弯刚度矩形桩的71%～91%,两者最大桩顶位移与悬臂段长度之比分别为4.1‰和4.5‰;两者滑坡推力和截面弯矩沿悬臂段均呈梯形分布;相同高度处圆形桩的滑坡推力约为矩形的44%～98%;截面弯矩约为矩形桩43%～114%。(3)在颗粒流模拟中,随加载墙位移增大,桩前土应力集中,桩间土依靠桩侧摩擦支撑。矩形桩的桩间土被整体挤出但未出现绕流;随桩间距增大,桩间土拱矢高降低,桩身承担荷载比例上升。圆形桩绕流趋势明显且易发生荷载偏移,桩间土拱对抗滑桩的荷载分担比例影响较小。(4)计算模型中,随加载墙位移增大桩土承担总荷载和各桩阻滑力达到峰值后递减,土拱承担的荷载呈波动上升趋势。矩形桩最大承载力在桩间净距比为1.5～3.0时下降迅速;在3.0～4.0时逐渐变缓;随后又急速下降;圆形桩模型呈缓慢下降趋势。相同桩间净距比时,圆形桩的桩土总承载力约为矩形桩83%～98%,而圆形桩的荷载分担比为矩形桩的92%～97%;两者间差异随桩间净距比增大而减小。
[Abstract]:As a discontinuous retaining structure, anti-slide pile relies on pile body and soil arch between piles to achieve continuous retaining action. According to the different construction technology, the pile body has rectangular, circular and other cross-section forms. The rectangular section is simple in form and good in mechanical performance. It is commonly used in practical engineering. In recent years, with the improvement of construction efficiency and the development of construction mechanical properties, circular anti-slide pile, which is matched with mechanical hole forming technology, has been widely used. The working mechanism of pile-soil interaction is unclear. On the basis of summarizing and analyzing the existing pile-soil interaction theory, experimental results and numerical simulation results, the centrifuge model tests of rectangular and circular anti-slide piles under the condition of equal bending stiffness are adopted, respectively. The load response and load transfer characteristics of two types of piles are studied and compared, and the influence of pile spacing is analyzed through two-dimensional particle flow numerical calculation, and the overall bearing capacity of pile and soil, the soil arch effect between piles and the load-sharing ratio between piles and soil are discussed. The following conclusions are obtained preliminarily: in the geotechnical centrifuge model test, with the gradual loading of the landslide thrust, the overall movement of soil between the rectangular piles is smaller than that of the circular pile, and the soil between the piles is first bulk and then disintegrated and spalling to form a soil arch. Depending on the soil and the face of the pile forming arch foot, the spalling soil of the pile is block, the side is smooth, and the soil around the circular pile is larger than that of the rectangular pile, and the soil between the piles is spalling in a large amount of scattered shape, and the soil around the circular pile is larger than that of the rectangular pile, and the soil between the piles is spalling off in a large amount. The soil around the pile appears the flow around the side of the pile, but the soil arch phenomenon is relatively not obvious. (2) under the action of the landslide thrust loading step by step in the centrifugal field, The results show that the top displacement of circular pile is about 71% of rectangular pile with constant section flexural stiffness, the ratio of the maximum top displacement to the length of cantilever section is 4.1 鈥，

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