| 多层砂土地基扩底桩单桩抗压模型试验及颗粒流模拟研究 |
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| 引用本文： | 李飞,杨俊杰,宋琦,孙涛.多层砂土地基扩底桩单桩抗压模型试验及颗粒流模拟研究[J].中国海洋大学学报(自然科学版),2020(2):116-125. |
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| 作者姓名： | 李飞 杨俊杰 宋琦 孙涛 |
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| 作者单位： | 中国海洋大学海洋环境与生态教育部重点实验室;中国海洋大学环境科学与工程学院;山东科技大学地球科学与工程学院 |
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| 基金项目： | 国家自然科学基金项目(51779235);国家自然科学基金青年项目(41602322);山东科技大学人才引进科研启动基金项目(2015RCJJ010)资助~~ |
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| 摘 要： | 利用室内半模试验和颗粒流数值模拟,揭示多层砂土地基扩底桩单桩抗压承载特性及变形特征。结果表明,通过对比分析极限承载力与H_h/D(持力层厚度与扩大头直径之比)的关系可以看出,单桩的抗压极限承载力随H_h/D逐渐增加,当H_h/D超过2.0时,极限承载力基本不再增加,此时的单桩抗压极限承载力稳定在300.01~303.25 N,是H_h/D=0.5时极限承载力(183.83 N)的1.65倍。扩大头下部土体发生局部压缩-剪切破坏,破坏面从扩大头底面边缘向斜下方扩展,在水平方向影响范围达到最大后逐渐向桩内侧收缩;荷载作用越大,地基破坏区域越大,相应的极限抗压承载力也越大;持力层厚度增加,扩大头分担的荷载比例增大,分担的荷载达到稳定需要的桩顶位移也越大,H_h=0.5 D试验扩大头分担的荷载比例稳定时为60%,对应的桩顶位移约为29 mm;桩顶位移达到33 mm后,H_h=1.0~3.0 D试验稳定在63%~65%之间;通过细观颗粒流理论对砂土移动特性的研究发现,持力层厚度从0.5 D增大至2.0 D,破坏面的起始扩展角度从31°增大至42°。数值模拟研究结果与模型试验数据吻合效果良好,证明该方法分析多层砂土地基扩底桩单桩抗压荷载传递机理是可行的。
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| 关 键 词： | 砂土地基 桩顶位移 持力层厚度 扩底桩 颗粒流理论 半模试验 承载特性 单桩 |
Compressive Model Test and Particle Flow Simulation of Single Pile in Multi-Layer Sand Foundation |
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| LI Fei,YANG Jun-Jie,SONG Qi,SUN Tao.Compressive Model Test and Particle Flow Simulation of Single Pile in Multi-Layer Sand Foundation[J].Periodical of Ocean University of China,2020(2):116-125. |
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| Authors: | LI Fei YANG Jun-Jie SONG Qi SUN Tao |
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| Institution: | (Key Laboratory of Marine Environment and Ecology,Ministry of Education,Ocean University of China,Qingdao 266100,China;College of Environmental Science and Engineering,Ocean University of China,Qingdao 266100,China;College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China) |
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| Abstract: | The indoor semi-mould test and numerical simulation of particle flow are used to reveal the compressive bearing characteristics and deformation characteristics of single piles in multi-layer sand foundation. The results show that by comparing the ultimate bearing capacity with H_h/D(the ratio of the thickness of the bearing layer to the diameter of the enlarged head), it can be seen that the compressive ultimate bearing capacity of a single pile increases with H_h/D, when H_h/D When it exceeds 2.0, the ultimate bearing capacity will not increase any more. At this time, the ultimate bearing capacity of single pile is stable at 300.01~303.25 N, which is 1.65 times of the ultimate bearing capacity(183.83 N) when H_h/D=0.5. The local compression-shear failure occurs in the soil below the head, and the failure surface expands from the edge of the enlarged head to the obliquely downward direction. After the maximum influence range in the horizontal direction reaches the maximum, it gradually contracts to the inside of the pile. The larger the load, the larger the damage area of the foundation. The corresponding ultimate compressive bearing capacity is also increased;the thickness of the bearing layer is increased, the proportion of the load shared by the enlarged head is increased, and the displacement of the pile top required for the shared load to be stabilized is also larger. The load ratio of the head shared by the H_h=0.5 D. test is expanded. When it is stable, it is 60%, the corresponding pile top displacement is about 29 mm;after the pile top displacement reaches 33 mm, H_h=1.0~3.0 D is stable between 63%~65%;the sand movement is moved by the mesoscopic particle flow theory. The characteristics of the study found that the thickness of the bearing layer increased from 0.5 D to 2.0 D, and the initial expansion angle of the failure surface increased from 31° to 42°. The numerical simulation results agree well with the model test data, which proves that it is feasible to analyze the compressive load transfer mechanism of single piles in multi-layer sand. |
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| Keywords: | expanded single pile vertical bearing characteristics multi-layered soil foundation particle flow code |
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