不同填料土工织物散体桩桩体单轴压缩试验
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摘要
选用碎石、圆砾和砂3种填料,以及5种不同强度的聚丙烯土工编织布套筒,制备成15组尺寸为?300 mm×600mm,填料压实度?=0.9的土工织物散体桩,对桩体进行单轴压缩试验,以研究不同填料土工织物散体桩在轴向荷载作用下的强度特性。研究结果表明:不同填料桩体在单轴压缩下具有不同的破坏模式,碎石填料局部刺破编织布套筒形成较大破口,圆砾填料致套筒横向筋丝断裂、纵向筋丝分离,而砂填料致套筒横向筋丝断裂较均匀且无明显破口。桩体强度与筋材和填料强度均呈正相关关系,3种填料桩体轴向应力–应变曲线在加载初期因填料受到初始压密而略有上凹,而后近似线性增长至桩体强度,峰值强度后呈现应变软化现象;综合本文试验数据及前期所做的单轴、三轴压缩试验数据,修正了桩体强度理论计算公式,得到的桩体强度修正值与试验值吻合较好。
15 samples of geosynthetic-encased stone columns(GESCs) with a dimension of ?300 mm×600 mm and degree of compaction of 0.9 are made using three types of fills of crushed stone, pebble and sand and five different strength woven sleeves made of polypropylene geotextiles. The uniaxial compression tests are performed on the samples to investigate the characteristics of strength of GESCs. The results show that different failure modes happen to the GESC body with different fills under uniaxial compression. The crushed stone can partly puncture the woven sleeves to produce obvious holes and pebble is extruded to break the transverse polypropylene slices, while the longitudinal slices are separated. The sand evenly breaks the transverse slices with no obvious holes on sleeves. The strength of the GESC body has a positive relationship with the strength of the sleeves and the fills. The stress-strain curve of GESC body at preliminary loading stage is mildly concave down due to the initial densification, then increases linearly up to the peak stress, and subsequently decreases, showing strain-softening characteristics. Based on the present data and those of uniaxial and triaxial compression tests carried out by the authors before, the theoretical formula for the strength of the GESC body is amended, and the results of the modified formulas are proved to be in good agreement with the experimental ones.
15 samples of geosynthetic-encased stone columns(GESCs) with a dimension of ?300 mm×600 mm and degree of compaction of 0.9 are made using three types of fills of crushed stone, pebble and sand and five different strength woven sleeves made of polypropylene geotextiles. The uniaxial compression tests are performed on the samples to investigate the characteristics of strength of GESCs. The results show that different failure modes happen to the GESC body with different fills under uniaxial compression. The crushed stone can partly puncture the woven sleeves to produce obvious holes and pebble is extruded to break the transverse polypropylene slices, while the longitudinal slices are separated. The sand evenly breaks the transverse slices with no obvious holes on sleeves. The strength of the GESC body has a positive relationship with the strength of the sleeves and the fills. The stress-strain curve of GESC body at preliminary loading stage is mildly concave down due to the initial densification, then increases linearly up to the peak stress, and subsequently decreases, showing strain-softening characteristics. Based on the present data and those of uniaxial and triaxial compression tests carried out by the authors before, the theoretical formula for the strength of the GESC body is amended, and the results of the modified formulas are proved to be in good agreement with the experimental ones.
引文
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[4]赵明华,顾美湘,张玲,等.竖向土工加筋体对碎石桩承载变形影响的模型试验研究[J].岩土工程学报,2014,36(9):1587-1593.((ZHAO Ming-hua,GU Mei-xiang,ZHANG Ling,et al.Model tests on influence of vertical geosynthetic-encasement on performance of stone columns[J].Chinese Journal of Geotechnical Engineering,2014,36(9):1587-1593.(in Chinese))
[5]陈建峰,王波,魏静,等.加筋碎石桩复合地基路堤模型试验[J].中国公路学报,2015,28(9):1-8.(CHENJian-feng,WANG Bo,WEI Jing,et al.Model tests of embankments on soft foundation reinforced with geosynthetic-encased stone columns[J].China Journal of Highway and Transport,2015,28(9):1-8.(in Chinese))
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[7]LEE D Y,YOO C,PARK S,et al.Field load tests of geogrid encased stone columns in soft ground[C]//Proceedings of the Eighteenth International Offshore and Polar Engineering Conference.Vancouver,2008:521-524.
[8]GNIEL J,BOUAZZA A.Improvement of soft soils using geogrid encased stone columns[J].Geotextiles and Geomembranes,2009,27(3):167-175.
[9]ARAUJO G L S,PALMEIRA E M,CUNHA R P.Behaviour of geosynthetic-encased granular columns in porous collapsible soil[J].Geosynthetics International,2009,16(6):433-451.
[10]CHEN J F,LI L Y,XUE J F,et al.Failure mechanism of geosynthetic-encased stone columns in soft soils under embankment[J].Geotextiles and Geomembranes,2015,43(5):424-431.
[11]WU C S,HONG Y S.A simplified approach for evaluating the bearing performance of encased granular columns[J].Geotextiles and Geomembranes,2014,42(4):339-347.
[12]GNIEL J,BOUAZZA A.Construction of geogrid encased stone columns:a new proposal based on laboratory testing[J].Geotextiles and Geomembranes,2010,28(1):108-118.
[13]MIRANDA M,COSTA A D.Laboratory analysis of encased stone columns[J].Geotextiles and Geomembranes,2016,44(3):269-277.
[14]陈建峰,曾岳,冯守中,等.土工织物散体桩单轴压缩试验研究[J].中国公路学报,2018,31(6):181-187.(CHEN Jian-feng,ZENG Yue,FENG Shou-zhong,et al.Uniaxial compression test of geosynthetic-encased stone columns[J].China Journal of Highway and Transport,2018,31(6):181-187.(in Chinese))
[15]陈建峰,王兴涛,曾岳,等.土工织物散体桩桩体大三轴试验研究[J].岩土工程学报,2017,39(12):2212-2118.(CHEN Jian-feng,WANG Xing-tao,ZENG Yue,et al.Study on large triaxial compression tests of geosynthetic-encased stone column body[J].Chinese Journal of Geotechnical Engineering,2017,39(12):2212-2118.(in Chinese))
[16]BATHURST R J,ALLEN T M,WALTERS D L.Reinforcement loads in geosynthetic walls and the case for a new working stress design method[J].Geotextiles and Geomembranes,2005,23(4):287-322.
[2]MURUGESAN S,RAJAGOPAL K.Studies on the behavior of single and group of geosynthetic encased stone columns[J].Journal of Geotechnical and Geoenvironmental Engineering,2009,136(1):129-139.
[3]GNIEL J,BOUAZZA A.Construction of geogrid encased stone columns:a new proposal based on laboratory testing[J].Geotextiles and Geomembranes,2010,28(1):108-118.
[4]赵明华,顾美湘,张玲,等.竖向土工加筋体对碎石桩承载变形影响的模型试验研究[J].岩土工程学报,2014,36(9):1587-1593.((ZHAO Ming-hua,GU Mei-xiang,ZHANG Ling,et al.Model tests on influence of vertical geosynthetic-encasement on performance of stone columns[J].Chinese Journal of Geotechnical Engineering,2014,36(9):1587-1593.(in Chinese))
[5]陈建峰,王波,魏静,等.加筋碎石桩复合地基路堤模型试验[J].中国公路学报,2015,28(9):1-8.(CHENJian-feng,WANG Bo,WEI Jing,et al.Model tests of embankments on soft foundation reinforced with geosynthetic-encased stone columns[J].China Journal of Highway and Transport,2015,28(9):1-8.(in Chinese))
[6]RAITHEL M,KIRCHNER A,SCHADE C,et al.Foundation of constructions on very soft soils with geotextile encased columns-state of the art[C]//Proceedings of GeoFrontiers.Reston,2005:1-11.
[7]LEE D Y,YOO C,PARK S,et al.Field load tests of geogrid encased stone columns in soft ground[C]//Proceedings of the Eighteenth International Offshore and Polar Engineering Conference.Vancouver,2008:521-524.
[8]GNIEL J,BOUAZZA A.Improvement of soft soils using geogrid encased stone columns[J].Geotextiles and Geomembranes,2009,27(3):167-175.
[9]ARAUJO G L S,PALMEIRA E M,CUNHA R P.Behaviour of geosynthetic-encased granular columns in porous collapsible soil[J].Geosynthetics International,2009,16(6):433-451.
[10]CHEN J F,LI L Y,XUE J F,et al.Failure mechanism of geosynthetic-encased stone columns in soft soils under embankment[J].Geotextiles and Geomembranes,2015,43(5):424-431.
[11]WU C S,HONG Y S.A simplified approach for evaluating the bearing performance of encased granular columns[J].Geotextiles and Geomembranes,2014,42(4):339-347.
[12]GNIEL J,BOUAZZA A.Construction of geogrid encased stone columns:a new proposal based on laboratory testing[J].Geotextiles and Geomembranes,2010,28(1):108-118.
[13]MIRANDA M,COSTA A D.Laboratory analysis of encased stone columns[J].Geotextiles and Geomembranes,2016,44(3):269-277.
[14]陈建峰,曾岳,冯守中,等.土工织物散体桩单轴压缩试验研究[J].中国公路学报,2018,31(6):181-187.(CHEN Jian-feng,ZENG Yue,FENG Shou-zhong,et al.Uniaxial compression test of geosynthetic-encased stone columns[J].China Journal of Highway and Transport,2018,31(6):181-187.(in Chinese))
[15]陈建峰,王兴涛,曾岳,等.土工织物散体桩桩体大三轴试验研究[J].岩土工程学报,2017,39(12):2212-2118.(CHEN Jian-feng,WANG Xing-tao,ZENG Yue,et al.Study on large triaxial compression tests of geosynthetic-encased stone column body[J].Chinese Journal of Geotechnical Engineering,2017,39(12):2212-2118.(in Chinese))
[16]BATHURST R J,ALLEN T M,WALTERS D L.Reinforcement loads in geosynthetic walls and the case for a new working stress design method[J].Geotextiles and Geomembranes,2005,23(4):287-322.