桩基负摩阻力沿桩长变化的试验研究
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摘要
结合中国移动甘肃定西分公司新城区移动通信综合楼项目,在大厚度自重湿陷性黄土场地上进行长时间的桩基浸水载荷试验(试桩直径为800 mm,桩长26 m,试坑深度为2 m),对不同深度下、不同范围内的桩侧负摩阻力的变化特征以及土体的沉降过程进行分析。试验结果表明,特殊浸水条件下桩侧负摩阻力沿桩身出现多个峰值,并且正、负摩阻力出现交错分布的现象,无法给出建筑桩基技术规范[1]规定的平均负摩阻力值;桩周土体沉降量亦沿桩身出现多个峰值,并且其变化趋势直接影响桩侧正、负摩阻力沿桩身交替变化的走势;中性点位置并未得出建筑桩基技术规范[1]所提供的单一参考值而是沿桩身出现了多个中性点;黄土的实际湿陷情况是分段发生湿陷的,而不是如传统观点所述在单一中性点以上突然出现整段湿陷。
Combined with the project of mobile communication comprehensive building,Gansu Dingxi branch,China mobile in Dingxi new city,a lasting pile immersion test was made in the site of collapsible loess with large thickness;while the changing characteristics of pile negative friction and settlement process of soil were analyzed for different depths and limits(the diameter and length of test pile were 800 mm and 26 m respectively with 2 m pit in depth).The test results show that under the special immersion condition mentioned above,there appear multiple peak values along the pile,and positive and negative frictions presented staggered distribution phenomenon;so that the value of average negative friction couldn't be given by Technical code for building pile foundation[1];then with multimodal distribution of soil settlement amount,its changing tendency directly affects its trend in positive and negative friction along the pile;also,in the neutral point location,the single reference value provided by Technical code for building pile foundation wasn't given;but several neutral points appeared along the pile;and the actual collapsible condition of loess is in sections,but not is sudden collapsible in the whole section above a certain neutral point as the traditional view states.
Combined with the project of mobile communication comprehensive building,Gansu Dingxi branch,China mobile in Dingxi new city,a lasting pile immersion test was made in the site of collapsible loess with large thickness;while the changing characteristics of pile negative friction and settlement process of soil were analyzed for different depths and limits(the diameter and length of test pile were 800 mm and 26 m respectively with 2 m pit in depth).The test results show that under the special immersion condition mentioned above,there appear multiple peak values along the pile,and positive and negative frictions presented staggered distribution phenomenon;so that the value of average negative friction couldn't be given by Technical code for building pile foundation[1];then with multimodal distribution of soil settlement amount,its changing tendency directly affects its trend in positive and negative friction along the pile;also,in the neutral point location,the single reference value provided by Technical code for building pile foundation wasn't given;but several neutral points appeared along the pile;and the actual collapsible condition of loess is in sections,but not is sudden collapsible in the whole section above a certain neutral point as the traditional view states.
引文
[1]中国建筑科学研究院.JGJ94-2008建筑桩基技术规范[S].北京:中国建筑出版社,2008.
[2]刘祖典.黄土力学与工程[M].西安:科学技术出版社,1997.
[3]肖俊华,袁聚云,赵锡宏.桩基负摩擦力的试验模拟和计算应用[M].北京:科学出版社,2009.
[4]苗天德.黄土湿陷变形机理的研究现状[C]//湿陷性黄土研究与工程.北京:中国建筑工业出版社,2001:73-82.MIAO Tian-de.Present status of collapse deformation mechanism of loess[C]//Engineering and Research on Collapsible Loess.Beijing:China Architecture and Building Press,2001:73-82.
[5]高国瑞.黄土显微结构与湿陷性[J].中国科学,1980,31(12):1203-1208.GAO Guo-rui,Classification of loess microstructure and its collapsibility[J].Science in China,1980,31(12):1203-1208.
[6]杨运来.黄土湿陷机理的研究[J].中国科学(B辑),1988,39(7):754-766.YANG Yun-lai.Study on collapse mechanism of loess[J].Science in China(Series B),1988,39(7):754-766.
[7]ROGERS C D F,DIJKSTRA T A,SMALLEY I J.Hydroconsolidation and subsidence of loess:Studies from China,Russia,North America and Europe[J].Engineering Geology,1994,37(2):83-113.
[8]FEDA J.Structural stability of subsident loess soils from Praha-Dejvice[J].Engineering Geology,1966,1:201219.
[9]黄雪峰,陈正汉,哈双,等.大厚度自重湿陷性黄土中灌注桩承载性状与负摩阻力的试验研究[J].岩土工程学报,2007,29(3):338-346.HUANG Xue-feng,CHEN Zheng-han,HA Shuang,et al.Research on bearing behaviors and negative friction force for filling piles in the site of collapsible loess with big thickness[J].Chinese Journal of Geotechnical Engineering,2007,29(3):338-346.
[10]王兰民,孙军杰,黄雪峰,等.黄土场地震陷时桩基负摩阻力的现场试验研究[J].岩土工程学报,2008,30(3):341-348.WANG Lan-min,SUN Jun-jie,HUANG Xue-feng,et al.Field tests on negative skin friction along piles caused by seismic settlement of loess[J].Chinese Journal of Geotechnical Engineering,2008,30(3):341-348.
[11]齐静静,徐日庆,龚维明.湿陷性黄土地区桩侧负摩阻力问题的试验研究[J].岩土力学,2006,27(增刊):881-884.QI Jing-jing,XU Ri-qing,GONG Wei-ming.Experimental study on negative skin friction resistance on piles in collapsible loess area[J].Rock and Soil Mechanics,2006,27(Supp.):881-884.
[12]魏进,李哲,郝忙利,等.自重湿陷性黄土场地的桩基浸水载荷试验[J].长安大学学报,2011,31(5):63-67.WEI Jin,LI Zhe,HAO Mang-li,et al.Submerged static load test of pile foundation in collapsible loess area[J].Journal of Chang’an University,2011,31(5):63-67.
[13]夏力农,雷鸣,聂重军.桩顶荷载对负摩阻力性状影响的现场试验[J].岩土力学,2009,30(3):664-668.XIA Li-nong,LEI Ming,NIE Chong-jun.Field test of influences of load at pile top on negative skin friction behaviors[J].Rock and Soil Mechanics,2009,30(3):664-668.
[14]李大展,滕延京,何颐华,等.湿陷性黄土中大直径扩底桩垂直承载性状的试验研究[J].岩土工程学报,1994,16(2):11-21.LI Da-zhan,TENG Yan-jing,HE Yi-hua,et al.Vertical bearing behaviour of lager diameter belled pile in collapse loess[J].Chinese Journal of Geotechnical Engineering,1994,16(2):11-21.
[15]姚志华,黄雪峰,陈正汉,等.兰州地区大厚度自重湿陷性黄土场地浸水试验综合观测研究[J].岩土工程学报,2012,34(1):65-74.YAO Zhi-hua,HUANG Xue-feng,CHEN Zheng-han,et al.Comprehensive soaking tests on self-weight collapse loess with heavy section in Lanzhou region[J].Chinese Journal of Geotechnical Engineering,2012,34(1):65-74.
[2]刘祖典.黄土力学与工程[M].西安:科学技术出版社,1997.
[3]肖俊华,袁聚云,赵锡宏.桩基负摩擦力的试验模拟和计算应用[M].北京:科学出版社,2009.
[4]苗天德.黄土湿陷变形机理的研究现状[C]//湿陷性黄土研究与工程.北京:中国建筑工业出版社,2001:73-82.MIAO Tian-de.Present status of collapse deformation mechanism of loess[C]//Engineering and Research on Collapsible Loess.Beijing:China Architecture and Building Press,2001:73-82.
[5]高国瑞.黄土显微结构与湿陷性[J].中国科学,1980,31(12):1203-1208.GAO Guo-rui,Classification of loess microstructure and its collapsibility[J].Science in China,1980,31(12):1203-1208.
[6]杨运来.黄土湿陷机理的研究[J].中国科学(B辑),1988,39(7):754-766.YANG Yun-lai.Study on collapse mechanism of loess[J].Science in China(Series B),1988,39(7):754-766.
[7]ROGERS C D F,DIJKSTRA T A,SMALLEY I J.Hydroconsolidation and subsidence of loess:Studies from China,Russia,North America and Europe[J].Engineering Geology,1994,37(2):83-113.
[8]FEDA J.Structural stability of subsident loess soils from Praha-Dejvice[J].Engineering Geology,1966,1:201219.
[9]黄雪峰,陈正汉,哈双,等.大厚度自重湿陷性黄土中灌注桩承载性状与负摩阻力的试验研究[J].岩土工程学报,2007,29(3):338-346.HUANG Xue-feng,CHEN Zheng-han,HA Shuang,et al.Research on bearing behaviors and negative friction force for filling piles in the site of collapsible loess with big thickness[J].Chinese Journal of Geotechnical Engineering,2007,29(3):338-346.
[10]王兰民,孙军杰,黄雪峰,等.黄土场地震陷时桩基负摩阻力的现场试验研究[J].岩土工程学报,2008,30(3):341-348.WANG Lan-min,SUN Jun-jie,HUANG Xue-feng,et al.Field tests on negative skin friction along piles caused by seismic settlement of loess[J].Chinese Journal of Geotechnical Engineering,2008,30(3):341-348.
[11]齐静静,徐日庆,龚维明.湿陷性黄土地区桩侧负摩阻力问题的试验研究[J].岩土力学,2006,27(增刊):881-884.QI Jing-jing,XU Ri-qing,GONG Wei-ming.Experimental study on negative skin friction resistance on piles in collapsible loess area[J].Rock and Soil Mechanics,2006,27(Supp.):881-884.
[12]魏进,李哲,郝忙利,等.自重湿陷性黄土场地的桩基浸水载荷试验[J].长安大学学报,2011,31(5):63-67.WEI Jin,LI Zhe,HAO Mang-li,et al.Submerged static load test of pile foundation in collapsible loess area[J].Journal of Chang’an University,2011,31(5):63-67.
[13]夏力农,雷鸣,聂重军.桩顶荷载对负摩阻力性状影响的现场试验[J].岩土力学,2009,30(3):664-668.XIA Li-nong,LEI Ming,NIE Chong-jun.Field test of influences of load at pile top on negative skin friction behaviors[J].Rock and Soil Mechanics,2009,30(3):664-668.
[14]李大展,滕延京,何颐华,等.湿陷性黄土中大直径扩底桩垂直承载性状的试验研究[J].岩土工程学报,1994,16(2):11-21.LI Da-zhan,TENG Yan-jing,HE Yi-hua,et al.Vertical bearing behaviour of lager diameter belled pile in collapse loess[J].Chinese Journal of Geotechnical Engineering,1994,16(2):11-21.
[15]姚志华,黄雪峰,陈正汉,等.兰州地区大厚度自重湿陷性黄土场地浸水试验综合观测研究[J].岩土工程学报,2012,34(1):65-74.YAO Zhi-hua,HUANG Xue-feng,CHEN Zheng-han,et al.Comprehensive soaking tests on self-weight collapse loess with heavy section in Lanzhou region[J].Chinese Journal of Geotechnical Engineering,2012,34(1):65-74.
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