(1. School of Highway，Chang?an University，Xi?an，Shaanxi 710064，China；2. School of Architecture and Civil Engineering，Xihua University，Chengdu，Sichuan 610039，China；3. Fujian Transportation Construction Quality and Safety Center，Fuzhou，Fujian 350001，China；4. Sanming Puyan Highway Limited Liability Company，Sanming，Fujian 353000，China；
5. Wenshan Guangna Expressway Investment Construction Development Company Limited，Kunming，Yunnan 663000，China)
Abstract：The field test of bridge pile foundation passing through the cave 25.5 m in height were carried out to explore the load transfer mechanism of the pile foundation of highway bridge passing through the super-large cave. The vertical bearing characteristics and load transfer mechanism of the pile foundations passing through the caves with different height were studied when the backfilling method was used to treat the karst cave. The maximum value of negative friction caused by consolidation settlement of the backfill materials and the proportion of its distribution range were proposed. The results show that：when the load is small，the axial force of the pile foundation passing through the super-large cave increases in a certain range，and the negative friction resistance of pile foundation is generated after the cave is backfilled. The vertical ultimate bearing capacity of the pile foundation decreases with the increasing height of karst cave. When the height of the cave increases from 5 m to 30 m，the maximum negative friction resistance under ultimate load increases by 102.7%，and the proportion of its range increases from 0% to 24%. When the height of the cave exceeds 25 m，the negative friction range accounts for more than 20%. If the backfill method is used to treat the cave，it was recommended that when the height of the cave was 5 m to 10 m，the influence of negative friction resistance could be ignored. When the cavern is very large，the adverse effect of negative friction resistance on vertical bearing characteristics of pile foundation should be considered. When the cavern height is 15，20，25，30 m，it is recommended to calculate the bearing capacity of the piles according to negative friction resistance within 0.092 H，0.145 H，0.213 H，0.240 H(cavern height) from the cavern top.
[1] FENG Z J，CHEN H Y，XIA C M，et al. Prediction of bearing capacity of pile foundation in karst area based on model of metabolic GM (1，1)[J]. IOP Conference Series Earth Environmental Science，2018，189：042012.
[2] FENG Z J，HU H B，DONG Y X，et al. Effect of steel casing on vertical bearing characteristics of steel tube-reinforced concrete piles in loess area[J]. Applied Sciences，2019，9(14)：2 874.
[3] JIANG C，LIU L，WU J. A new method determining safe thickness of karst cave roof under pile tip[J]. Journal of Central South University，2014，21(3)：1 190–1 196.
[4] 冯忠居，张永清，李 晋. 堆载引起桥梁墩台与基础的偏移及防治技术研究[J]. 中国公路学报，2004，(3)：77–80.(FENG Zhongju，ZHANG Yongqing，LI Jin. Study of displacement of bridge pier and abutment foundation caused by earth piling load and its prevention technique[J]. China Journal of Highway and Transport，2004，(3)：77–80.(in Chinese))
[5] WANG P，DING H，ZHANG P. Influence of karst caves at pile side on the bearing capacity of super-long pile foundation[J]. Mathematical Problems in Engineering，2020，2020(2)：1–13.
[6] CHEN H Y，FENG Z J，LI T，et al. Study on the vertical bearing performance of pile across cave and sensitivity of three parameters[J]. Scientific Reports，2021，11：17 342.
[7] 何春林，龚成中，吉德广. 岩溶地区溶洞特性对桩基承载性能的影响分析[J]. 淮阴工学院学报，2006，(1)：78–81.(HE Chunlin，GONG Chengzhong，JI Deguang. The influence of the cave characteristics on pile bearing capacity in karst area[J]. Journal of Huaiyin Institute of Technology，2006，(1)：78–81.(in Chinese))
[8] 谢书萌. 基于有限差分法的下伏岩溶对桩基承载特性的影响[J]. 长江科学院院报，2019，36(4)：77–81.(XIE Shumeng. Investigation on influence of underlying karst on bearing capacity of pile foundation by finite difference method[J]. Journal of Yangtze River Scientific Research Institute，2019，36(4)：77–81.(in Chinese))
[9] 黄 明，张冰淇，陈福全，等. 串珠状溶洞地层中桩基荷载传递特征的数值计算[J]. 工程地质学报，2017，25(6)：1 574–1 582. (HUANG Ming，ZHANG Bingqi，CHEN Fuquan，et al. Numerical calculation on load transfer progress of pile foundation in beaded barst cave stratum[J]. Journal of Engineering Geology，2017，25(6)：1 574– 1 582.(in Chinese))
[10] 赵明华，蒋 冲，曹文贵. 岩溶区嵌岩桩承载力及其下伏溶洞顶板安全厚度的研究[J]. 岩土工程学报，2007，29(11)：1 618–1 622. (ZHAO Minghua，JIANG Chong，CAO Wengui. Study on bearing capacity of rock-socked piles and safe thickness of cave roofs in karst region[J]. Chinese Journal of Geotechnical Engineering，2007，29(11)：1 618–1 622.(in Chinese))
[11] 苏冠峰. 多层岩溶区桥梁基桩竖向承载性状试验研究[硕士学位论文][D].长沙：中南林业科技大学，2015.(SU Guanfeng. Experimental study on vertical bearing behavior of bridge foundation pile in multilayer karst region[M. S. Thesis][D]. Changsha：Central South University of Forestry and Technology，2015.(in Chinese))
[12] 董芸秀，冯忠居，郝宇萌，等. 岩溶区桥梁桩基承载力试验与合理嵌岩深度[J]. 交通运输工程学报，2018，18(6)：27–36.(DONG Yunxiu，FENG Zhongju，HAO Yumeng，et al. Experiment on bearing capacity of bridge pile foundations in karst area sand reasonable rock-socketed depth[J]. Journal of Traffic and Transportation Engineering，2018，18(6)：27–36.(in Chinese))
[13] WONG C T，YIM K P，LEUNG M K，et al. Rock-socketed large diameter bored pile and geophysical survey in cavernous karst area：Tin Shuiwai public library cum indoor recreation center[J]. Procedia Engineering，2011，14：1 744–1 751.
[14] 冯忠居. 特殊地区基础工程[M]. 北京：人民交通出版社，2010：25–30.(FENG Zhongju. Foundation engineering in special areas[M]. Beijing：China Communications Press，2010：25–30.(in Chinese))
[15] 冯忠居，陈慧芸，袁枫斌，等. 桩–土–断层耦合作用下桥梁桩基竖向承载特性[J]. 交通运输工程学报，2019，19(2)：36–48.(FENG Zhongju，CHEN Huiyun，YUAN Fengbin，et al. Vertical bearing characteristics of bridge pile foundation under pile-soil-fault coupling action[J]. Journal of Traffic and Transportation Engineering，2019，19(2)：36–48.(in Chinese))
[16] BOZOZUK M. Downdrag measurements on a 160-Ft floating pipe test pile in marine clay[J]. Canadian Geotechnical Journal，1972，2：127–136.
[17] BOZOZUK M. Bearing capacity of pile preloaded by down drag[C]// Proceedings of the Tenth International Conference on Soil Mechanics and Foundation Engineering. Stockholm：[s. n.]，1981：631–636.
[18] 冯忠居，谢永利，张宏光，等. 地面水对黄土地区桥梁桩基承载力影响试验研究[J]. 岩石力学与工程学报，2005，24(10)：1 758– 1 765.(FENG Zhongju，XIE Yongli，ZHANG Hongguang，et al. Experimental study on effect of surface water on bearing capacity of bridge pile foundation in loess region[J]. Chinese Journal of Rock Mechanics and Engineering，2005，24(10)：1 758–1 765.(in Chinese))
[19] 孔纲强，杨 庆，郑鹏一，等. 考虑时间效应的群桩负摩阻力模型试验研究[J]. 岩土工程学报，2009，31(12)：1 913–1 919.(KONG Gangqiang，YANG Qing，DENG Pengyi，et al. Model test of negative friction resistance of pile group considering time effect[J]. Chinese Journal of Geotechnical Engineering，2009，31(12)：1 913–1 919.(in Chinese))
[20] 冯忠居，胡海波，董芸秀，等. 削减桩基负摩阻力的室内模拟试验[J]. 岩土工程学报，2019，41(增2)：45–48.(FENG Zhongju，HU Haibo，DONG Yunxiu，et al. Indoor simulation tests on reducing negative skin friction of pile foundation[J]. Chinese Journal of Geotechnical Engineering，2019，41(Supp.2)：45–48.(in Chinese))
[21] 戴国亮，黄 挺，龚维明，等. 边载作用下砂土桩基负摩阻力试验[J]. 中国公路学报，2015，137(1)：1–7.(DAI Guoliang，HUANG Ting，GONG Weiming，et al. Test of negative friction resistance of sand pile foundation under side load[J]. China Journal of Highway and Transport，2015，137(1)：1–7.(in Chinese))
[22] 中华人民共和国行业标准编写组. JTG 3363—2019公路桥涵地基与基础设计规范[S]. 北京：中国建筑工业出版社，2019.(The Professional Standards Compilation Group of People?s Republic of China. JTG 3363—2019 Code for design of ground base and building foundation[S]. Beijing：China Architecture and Building Press，2019.(in Chinese))
[23] 陈显新，徐新跃. 桩负摩阻力的若干问题[J]. 岩石力学与工程学报，2004，23(增1)：4 615–4 618.(CHEN Xianxin，XU Xinyue. Several issues about negative skin friction of piles[J]. Chinese Journal of Rock Mechanics and Engineering，2004，23(Supp.1)：4 615– 4 618.(in Chinese))
[24] 胡铖波，梅 岭，梅国雄，等. 桩土模型中土体边界选取的有限元分析[J]. 建筑科学，2009，25(9)：18–20.(HU Chengbo，MEI Ling，MEI Guoxiong，et al. Finite element method for selecting the soil boundary in the model of pile-soil[J]. Building Science，2009，25(9)：18–20.(in Chinese))
[25] 梁发云，贾亚杰，邓 航，等. 深基坑降水沉降计算土体弹性参数取值方法探讨[J]. 岩土工程学报，2017，39(增2)：29–32.(LIANG Fayun，JIA Yajie，DENG Hang，et al. Discussions on elastic parameters of soil for land subsidence caused by decompression of confined aquifer in deep excavation[J]. Chinese Journal of Geotechnical Engineering，2017，39(Supp.2)：29–32.(in Chinese))
2023, Vol. 42 
