静钻根植竹节桩是一种新型组合桩基础.大量试验研究表明，桩受到上拔荷载与压荷载时，桩侧极限摩阻力存在差异，并将抗拔桩与抗压桩极限侧摩阻力比值定义为抗拔侧摩阻力折减系数.为了研究静钻根植竹节桩在软土地基中抗拔与抗压条件下侧摩阻力大小的差异系数，通过一组现场试验得到了抗压桩与抗拔桩的荷载位移曲线，然后根据实测参数用有限元软件Abaqus对试桩进行模拟，并将现场试验与数值模拟的荷载位移曲线对比以验证模型的可靠性.研究结果表明：抗拔桩与抗压桩桩身轴力具有相似传递特性，静钻根植竹节桩在软土地基中的总侧摩阻力折减系数λ=0.5；桩端水泥土扩大头直径的增加对提高抗拔桩与抗压桩极限侧摩阻力作用不明显；静钻根植竹节桩的总侧摩阻力折减系数基本不随桩端扩大头直径的改变而改变.
The pre-bored grouting planted nodular (PGPN) pile is a new type of composite pile foundation. A large number of field test results have shown that the ultimate skin friction of piles under tension and compression has big differences. The total lateral friction reduction factor is defined as the ratio of shaft resistance between uplift pile and compressive pile. To investigate the differences of skin friction distribution of the PGPN piles under tension and compression in soft soils, a group of field tests were carried to obtain the load-displacement curves of piles under tension and compression, and then Abaqus was used to simulate test piles. The comparison between results of field tests and Abaqus simulation was used to validate finite element model. The results showed that the axial forces of piles under tension and compression have similar transfer characteristics; the uplift coefficient of the PGPN piles in soft soils is 0.5. The increase of diameter of enlarged pile tip has little effect on ultimate skin friction of piles under tension and compression. The total lateral friction reduction factor of the PGPN piles is a constant with the increase of the diameter of enlarged pile base.
［1］KIYA Y, KATO Y, KUWABARA F. Model tests on vertical bearing performance of enlarged base bulb of buried nodular piles［J］. Journal of Structural and Construction Engineering, 2008, 73(624): 267-273.
［2］周佳锦, 王奎华, 龚晓南, 等. 静钻根植竹节桩承载力及荷载传递机制研究［J］. 岩土力学, 2014, 35(5): 1367-1376.
ZHOU Jiajin, WANG Kuihua, GONG Xiaonan, et al. Bearing capacity and load transfer mechanism of static drill rooted nodular piles［J］. Rock and Soil Mechanics, 2014, 35(5): 1367-1376.
［3］周佳锦, 龚晓南, 王奎华, 等.静钻根植竹节桩荷载传递机理模型试验［J］. 浙江大学学报(工学版), 2015, 49(3): 531-537.
ZHOU Jiajin, GONG Xiaonan, WANG Kuihua, et al. Model test on load transfer mechanism of a static drill rooted nodular pile［J］. Journal of Zhejiang University (Engineering Science), 2015, 49(3): 531-537.
［4］杨淼, 张忠苗, 刘念武, 等.新型螺旋成孔根植注浆竹节管桩抗压性状数值模拟研究［J］. 岩土力学, 2013, 34(7): 2119-2126.
YANG Miao, ZHANG Zhongmiao, LIU Nianwu, et al. Numerical simulation of compressive mechanical characters of new bored grouting PHC nodular pile［J］. Rock and Soil Mechanics, 2013, 34(7): 2119-2126.
［5］LI S C, ZHANG Q, ZHANG Q Q, et al. Field and theoretical study of the response of super-long bored pile subjected to compressive load［J］. Marine Georesources & Geotechnology, 2016, 34(1): 71-78.
［6］邵光辉, 王武, 赵志峰. 无粘结钢绞线抗拔桩的承载性状和抗拔系数研究［J］. 地下空间与工程学报, 2016, 12(3): 656-661.
SHAO Guanghui, WANG Wu, ZHAO Zhifeng. Shaft capacity and tension coefficient of unbonded steel strand uplift pile［J］. Chinese Journal of Underground Space and Engineering, 2016, 12(3): 656-661.
［7］EISHERBINYZEYAD Z, HESHAM E N. Axial compressive capacity of helical piles from field tests and numerical study［J］. Canadian Geotechnical Journal, 2013, 50(12): 1191-1203.
［8］ZHANG Z M, ZHANG Q Q, YU F. A destructive field study on the behavior of piles under tension and compression［J］. Journal of Zhejiang University: Science A (Applied Physics and Engineering), 2011, 12(4): 291-300.
［9］马杰, 赵建, 赵延林. 抗压桩与抗拔桩受力特性的现场破坏性试验［J］. 西南交通大学学报, 2013, 48(2): 283-289.
MA Jie, ZHAO Jian, ZHAO Yanlin. Destructive field test on properties of uplift and compression piles［J］. Journal of Southwest Jiaotong University, 2013, 48(2): 283-289.
［10］欧阳芳, 张建经, 邓小宁, 等. 钢纤维混凝土桩承载特性模型试验［J］. 上海交通大学学报, 2016, 50(3): 364-369.
OUYANG Fang, ZHANG Jianjing, DENG Xiao-ning, et al. Analysis of load capacity behaviors of steel fiber reinforced concrete piles through model tests［J］. Journal of Shanghai Jiao Tong University, 2016, 50(3): 364-369.
［11］中国建筑科学研究院. 建筑地基基础设计规范: GB50007—2011［S］. 北京: 中国建筑工业出版社, 2011.
China Academy of Building Research. Code for design of building foundation: GB50007—2011［S］. Beijing: China Architecture and Building Press, 2011.
［12］中国建筑科学研究院. 建筑基桩检测技术规范: JGJ106—2014［S］. 北京: 中国建筑工业出版社, 2014.
China Academy of Building Research. Technical code for testing of building foundation piles: JGJ106—2014［S］. Beijing: China Architecture and Building Press, 2014.
［13］王睿, 张建民. 可液化地基中单桩基础的三维数值分析方法及应用［J］. 岩土工程学报, 2015, 37(11): 1979-1985.
WANG Rui, ZHANG Jianmin. Three-dimensional elastic-plastic analysis method for piles in liquefiable ground［J］. Chinese Journal of Geotechnical Engineering, 2015, 37(11): 1979-1985.
［14］贾强, 张鑫, 张琳. 既有建筑桩基础开挖过程中承载特性数值分析［J］. 地下空间与工程学报, 2016, 12(1): 114-118.
JIA Qiang, ZHANG Xin, ZHANG Lin. Numerical analysis on the bearing behavior of the existing building’s pile caused by excavation around piles［J］. Chinese Journal of Underground Space and Engineering, 2016, 12(1): 114-118.
［15］周杨, 肖世国, 徐骏, 等.变截面螺纹桩竖向承载特性试验研究［J］. 岩土力学, 2017, 38(3): 747-754.
ZHOU Yang, XIAO Shiguo, XU Jun, et al. Model test on vertical bearing capacity of variable cross-section thread piles［J］. Rock and Soil Mechanics, 2017, 38(3): 747-754.
［16］吴迈.砼芯水泥土桩单桩竖向承载性状研究与可靠度分析［D］. 天津: 天津大学, 2008.
WU Mai. Research on vertically bearing behavior and reliability analysis of concrete-cored DCM pile［D］.Tianjin: Tianjin University, 2008.
［17］张忠苗.桩基工程［M］. 北京: 中国建筑工业出版社, 2007.
ZHANG Zhongmiao.Pile foundation engineering［M］. Beijing: China Architecture and Building Press, 2007.
