卵石地基大直径灌注桩大吨位载荷试验与承载特性分析
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摘要
结合某高速公路黑河特大桥重点工程项目,进行了两根大直径、大吨位灌注桩的静载荷试验,通过预先在试桩中埋设的测试元件,求解桩身轴力和桩侧摩阻力,进一步探讨了卵石土地基中挖孔和钻孔灌注桩承载特性的差异.试验结果表明:两种施工方法的基桩承载力特征值均能够满足设计要求;当挖孔和钻孔灌注桩试桩分别加载至18 000 kN和18 163 kN时,沉降量分别为4.32 mm和4.49 mm,且挖孔成桩可明显缩短工期;测试过程中同时关注到西部干旱地区温差较大,需对基准梁进行必要的防护,避免基准梁受太阳直射,影响测试结果.该试验结果对类似工程具有指导作用,积累了该地区的试桩资料.
In this paper,the static load test of two large diameter and large scale bored piles is carried out based on the key project of Heihe Expressway Bridge.The axial force of the pile body and the side friction of the pile are obtained by the test elements embedded in the test pile in advance.The difference of bearing capacity between bored piles and excavated piles on pebble soil foundation is further discussed.The test results show that the characteristic values of the bearing capacity of the two construction methods can meet the design requirements.When the excavated cast-in-place pile and bored cast-in-place pile are loaded to 18 000 kN and 18 163 kN respectively,the settlement is 4.32 mm and 4.49 mm respectively,and the excavated cast-in-place pile construction period can be shortened obviously.Since the temperature difference in the arid region of western China is quite large,so the reference beam should be well protected from the direct sunlight,otherwise the test results will be affected inevitably.The test results can be used as guidance for similar projects,and the test pile data in this area have been accumulated.
In this paper,the static load test of two large diameter and large scale bored piles is carried out based on the key project of Heihe Expressway Bridge.The axial force of the pile body and the side friction of the pile are obtained by the test elements embedded in the test pile in advance.The difference of bearing capacity between bored piles and excavated piles on pebble soil foundation is further discussed.The test results show that the characteristic values of the bearing capacity of the two construction methods can meet the design requirements.When the excavated cast-in-place pile and bored cast-in-place pile are loaded to 18 000 kN and 18 163 kN respectively,the settlement is 4.32 mm and 4.49 mm respectively,and the excavated cast-in-place pile construction period can be shortened obviously.Since the temperature difference in the arid region of western China is quite large,so the reference beam should be well protected from the direct sunlight,otherwise the test results will be affected inevitably.The test results can be used as guidance for similar projects,and the test pile data in this area have been accumulated.
引文
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[14] 程晔,龚维明,戴国亮,等.软岩桩基承载性能试验研究[J].岩石力学与工程学报,2009,28(1):165-172.
[15] 李素华,周健,杨位,等.复杂地基中桩基承载机理计算研究[J].岩石力学与工程学报,2003(9):1571-1577.
[2] 史佩栋.桩基工程设计手册[M].北京:中国建筑工业出版社,2008.
[3] 洪毓康,陈强华.钻孔灌注桩的荷载传递性能[J].岩土工程学报,1985,7(5):22-35.
[4] 董金荣,林胜天,戴一鸣.大口径钻孔灌注桩荷载传递性状[J].岩土工程学报,1994,16(6):123-131.
[5] 赵春风,鲁嘉,孙其超,等.大直径深长钻孔灌注桩分层荷载传递特性试验研究[J].岩石力学与工程学报,2009,28(5):1020-1026.
[6] 吴炜.饱和黄土地区桩基托换基桩承载力变异行为研究[J].兰州交通大学学报,2016,36(3):29-34.
[7] 中华人民共和国住房和城乡建设部.建筑桩基技术规范:JGJ 94-2008[S].北京:中国建筑工业出版社,2008.
[8] 中华人民共和国住房和城乡建设部.建筑基桩检测技术规范:JGJ 106-2003[S].北京:中国建筑工业出版社,2014.
[9] 朱彦鹏,杨校辉,马天忠,等.黄土塬地区大直径长桩承载性状与优化设计研究[J].岩石力学与工程学报,2017,36(4):1012-1023.
[10] 周宏磊,陶连金,王法.非均质土层中钻孔灌注长桩竖向荷载传递模型及应用研究[J].土木工程学报,2011,44(增刊1):142-146.
[11] 王博林,马学宁,王旭.大直径嵌岩桥梁钻孔灌注基桩承载力自平衡法试验研究[J].兰州交通大学学报,2012,31(1):52-57.
[12] 中交公路规划设计院有限公司.公路桥涵地基与基础设计规范:JTG 063-2007[S].北京:人民交通出版社,2007.
[13] 赵翔,柳祖亭,骆英.加载反力装置对桩基静载荷试验精度的影响[J].江苏理工大学学报(自然科学版),2001(5):77-81.
[14] 程晔,龚维明,戴国亮,等.软岩桩基承载性能试验研究[J].岩石力学与工程学报,2009,28(1):165-172.
[15] 李素华,周健,杨位,等.复杂地基中桩基承载机理计算研究[J].岩石力学与工程学报,2003(9):1571-1577.