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再生混凝土骨料包裹桩承载特性试验研究

王志佳 何旭 李胜民 黎洪磊 张建经 李良勇

王志佳, 何旭, 李胜民, 黎洪磊, 张建经, 李良勇. 再生混凝土骨料包裹桩承载特性试验研究[J]. 西南交通大学学报, 2023, 58(1): 244-252. doi: 10.3969/j.issn.0258-2724.20210109
引用本文: 王志佳, 何旭, 李胜民, 黎洪磊, 张建经, 李良勇. 再生混凝土骨料包裹桩承载特性试验研究[J]. 西南交通大学学报, 2023, 58(1): 244-252. doi: 10.3969/j.issn.0258-2724.20210109
WANG Zhijia, HE Xu, LI Shengmin, LI Honglei, ZHANG Jianjing, LI Liangyong. Experimental Study on Bearing Capacity of Geosynthetic-Encased Recycled Concrete Aggregate Column[J]. Journal of Southwest Jiaotong University, 2023, 58(1): 244-252. doi: 10.3969/j.issn.0258-2724.20210109
Citation: WANG Zhijia, HE Xu, LI Shengmin, LI Honglei, ZHANG Jianjing, LI Liangyong. Experimental Study on Bearing Capacity of Geosynthetic-Encased Recycled Concrete Aggregate Column[J]. Journal of Southwest Jiaotong University, 2023, 58(1): 244-252. doi: 10.3969/j.issn.0258-2724.20210109

再生混凝土骨料包裹桩承载特性试验研究

doi: 10.3969/j.issn.0258-2724.20210109
基金项目: 国家自然科学基金(51708163);海南省科协青年科技英才学术创新计划项目(QCXM201807)
详细信息
    作者简介:

    王志佳(1987—),男,讲师,博士,研究方向为地基处理和岩土地震工程学,E-mail:993041@hainanu.edu.cn

    通讯作者:

    张建经(1960—),男,教授,博士,研究方向为地基处理和岩土工程抗震, E-mail:jianzhang1102@126.com

  • 中图分类号: TU43

Experimental Study on Bearing Capacity of Geosynthetic-Encased Recycled Concrete Aggregate Column

  • 摘要:

    采用再生混凝土骨料替换包裹碎石桩碎石芯料,形成一种新型地基处理方式——再生混凝土骨料包裹桩,以改善采用包裹碎石桩处理液化及软弱土地基时碎石强度未能充分发挥的问题. 开展了模型试验,研究包裹长度、刚度及长径比对再生混凝土骨料包裹桩单桩承载特性和骨料破碎度的影响. 研究结果表明:包裹长度为1倍~6倍桩径时,延长包裹长度可显著提高桩体承载力,包裹长度小于1倍或大于6倍桩径时,包裹长度对承载力改善不明显;包裹材料的临界刚度约为100 kN/m,当小于临界刚度时,增加包裹刚度能显著提高桩体承载力,大于临界刚度时,增加包裹刚度不再明显改善桩体承载力;再生混凝土骨料包裹桩桩长不变时,长径比大于10的桩体承载力较低,桩体主要在10~30 cm深度内产生不同程度的局部弯曲,长径比小于7的桩体承载力较高,桩体主要发生轻微鼓胀变形,无局部弯曲;混凝土骨料的破碎度与桩体能承受的极限荷载呈正相关,增加包裹长度、刚度及桩径均会增加芯料的破碎度. 因此,进行再生混凝土骨料包裹桩单桩设计时应充分考虑包裹长度、刚度和长径比与芯料破碎度之间的关系,以获取最优设计方案.

     

  • 图 1  土体和混凝土骨料级配曲线

    Figure 1.  Grading curves of sand and concrete aggregate

    图 2  土工包裹材料拉伸试验结果

    Figure 2.  Tensile behavior of geosynthetics samples

    图 3  试验装置示意(单位:cm)

    Figure 3.  Schematic of test device (unit: cm)

    图 4  拉线位移计的布置

    Figure 4.  Arrangement of stay wire displacement meter

    图 5  包裹长度的荷载沉降曲线

    Figure 5.  Load-settlement (F-S) curves of column top for different encased lengths

    图 6  极限荷载随包裹长度的变化

    Figure 6.  Variation of ultimate load with encased length

    图 7  再生混凝土骨料包裹桩与包裹碎石桩的桩顶荷载沉降曲线对比

    Figure 7.  Comparison of column top load-settlement curves between recycled concrete aggregate encased column and encased stone column

    图 8  不同包裹刚度下的荷载沉降曲线

    Figure 8.  Load-settlement (F-S) curves of column top for different encasement stiffnesses

    图 9  极限荷载随包裹刚度的变化

    Figure 9.  Variation of ultimate load with encasement stiffness

    图 10  不同长径比下的荷载沉降曲线

    Figure 10.  Load-settlement (F-S) curves of column top for columns with different diameters

    图 11  不同长径比的桩体变形示意

    Figure 11.  Schematic of column deformation with different length-to-diameter ratios

    图 12  试验后混凝土骨料的粒径级配曲线

    Figure 12.  Grading curves of concrete aggregate after test

    表  1  试验模型相似比

    Table  1.   Similarity ratio for model test

    无量纲因子参数原型模型相似比
    ${\pi _1} = \dfrac{l}{L}$l/cm7007010
    ${\pi _2} = \dfrac{d}{L}$d/cm1001010
    ${\pi _3} = \dfrac{F}{{\rho g L A}}$F/kN5 00051 000
    $ {\pi _3} = \dfrac{{{T_{\rm{g}}}}}{{\rho g L {t_{\rm{g}}}}} $Tg/ (kN·m−11301310
    ${\pi _4} = \dfrac{{{J_{\rm{g}}}}}{{\rho g L {t_{\rm{g}}}}}$Jg/ (kN·m−11 40014010
    下载: 导出CSV

    表  2  砂土及混凝土骨料参数

    Table  2.   Properties of soil layers and concrete aggregate

    材料密度/(kg•m−3相对密度/%含水率/%颗粒密度/(g•cm−3内摩擦角/(º)
    土体(GP)1 664.15532.6539.12
    再生混凝土骨料(SP)1 528.07002.8342.00
    下载: 导出CSV

    表  3  包裹材料拉伸强度指标

    Table  3.   Tensile strength indices of geosynthetics

    名称 极限强度/
    (kN•m−1
    最大延伸率/% 延伸率 5% 的拉应力/
    (kN•m−1
    包裹材料刚度/
    (kN•m−1
    材料Ⅰ 2.58 15.42 1.24 24.80
    材料Ⅱ 5.21 14.40 2.45 49.00
    材料Ⅲ 7.51 16.70 3.69 73.80
    材料Ⅳ 10.04 15.33 5.11 102.20
    下载: 导出CSV

    表  4  试验分组

    Table  4.   Details of group tests

    组号试验工况d/mmL/mm包裹长度L1/mm
    1 土体
    2 无包裹 100 700 0
    3 3d- Ⅰ 100 700 300
    4 4d- Ⅰ 100 700 400
    5 5d- Ⅰ 100 700 500
    6 7d- Ⅰ 100 700 700
    7 7d- Ⅱ 100 700 700
    8 7d- Ⅲ 100 700 700
    9 7d- Ⅳ 100 700 700
    10 长径比 12.5- Ⅰ 56 700 700
    11 长径比 10.0- Ⅰ 70 700 700
    12 长径比 6.0- Ⅰ 117 700 700
    下载: 导出CSV

    表  5  包裹桩极限承载力取值

    Table  5.   Values of ultimate bearing capacity of encased columns

    来源取值方法取值标准
    文献[6]第 1 种P-S 曲线转折点
    文献[19]第 2 种S=30 mm → Fu
    文献[18]第 2 种S=40 mm → Fu
    文献[20]第 3 种S=20%dcFu
    文献[9]第 4 种S=10%dcFu
    下载: 导出CSV

    表  6  不同包裹长度下桩的极限荷载

    Table  6.   Ultimate load of columns with different encased lengths

    编号试验工况Jg/(kN▪m−1Fu/kN
    1土体1.37
    2再生骨料桩02.58
    33d- Ⅰ24.83.13
    44d- Ⅰ24.83.24
    55d- Ⅰ24.83.69
    67d- Ⅰ24.83.76
    下载: 导出CSV

    表  7  不同包裹刚度下桩体承载力

    Table  7.   Bearing capacity of columns with different stiffnesses

    编号试验工况Jg/(kN·m−1Fu/kN
    1 土体 1.37
    2 再生骨料桩 0 2.58
    3 7d- Ⅰ 24.8 3.76
    4 7d- Ⅱ 49.0 4.09
    5 7d- Ⅲ 73.8 4.48
    6 7d-Ⅳ 102.2 4.82
    下载: 导出CSV

    表  8  混凝土骨料破碎度

    Table  8.   Degree of fragmentation of concrete aggregate

    试验工况Fu/ kNBr/%
    土体 1.36
    无包裹桩 2.63 2.48
    3d- Ⅰ 3.13 2.37
    4d- Ⅰ 3.24 4.14
    5d- Ⅰ 3.73 4.87
    7d- Ⅰ 3.76 6.27
    7d- Ⅱ 4.18 10.33
    7d- Ⅲ 4.53 15.41
    7d- Ⅳ 4.80 18.22
    长径比 12.5- Ⅰ 2.57 0.36
    长径比 10.0- Ⅰ 2.60 0
    长径比 7.0- Ⅰ 3.76 6.27
    长径比 6.0- Ⅰ 4.52 10.38
    下载: 导出CSV
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出版历程
  • 收稿日期:  2021-02-02
  • 修回日期:  2021-05-21
  • 网络出版日期:  2022-10-14
  • 刊出日期:  2021-06-11

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