Citation: | REN Guangming, LI Haitao, WANG Biyang, FAN Rongquan, DONG Bin, LUO Yi. Bearing characteristics of variable diameter micropile based on the improvement of group pile foundation[J]. Hydrogeology & Engineering Geology, 2024, 51(2): 90-100. doi: 10.16030/j.cnki.issn.1000-3665.202304050 |
To improve the load-bearing of transmission tower micropile foundation and reduce the material cost, a modified variable diameter micropile foundation type based on group micropile is proposed in this study. The bearing characteristics and deformation mechanism of variable diameter miniature pile were revealed by simulation with three kinds of variable diameter miniature micropiles and comparison with the bearing effect of micropile group pile, using the prototype test and numerical inversion model of micropile group pile with equal section in the highland mountainous area. The results show that the compressive and pullout bearing capacities of micropile group foundation (2×2 single pile) are greater and less than the total of corresponding single pile bearing capacity, respectively, due to the effect of bearing platform and group pile effect. The ultimate pullout and compressive bearing capacities of double diameter-extended micropile (the diameter of the dilated part = 2 × the diameter of the equal) is approximately 3.8 times and 2.7 times of the equal section micropile. The soil deformation is concentrated in the dilated part with large deformation value, which presents the characteristics of multi-fulcrum friction-end bearing pile. The addition of cap can improve the downward pressure and horizontal bearing capacity of double-expanded micropile effectively, which increase 2.1 times and 2.2 times compared to that in the situation of no cap, respectively. This study indicates that improving the performance of single micropile to the level of equal section group micropiles by extending part of the pile diameter is feasible and has engineering significance for the transmission and substation construction.
[1] |
崔强,郭超溢,张楷,等. 薄壁锥端注浆微型钢管桩抗拔承载特性的现场试验[J]. 工程科学与技术,2021,53(5):21 − 31. [CUI Qiang,GUO Chaoyi,ZHANG Kai,et al. Field test on the uplift bearing characteristics of thin-walled cone-end grouting micro-steel pipe pile[J]. Advanced Engineering Sciences,2021,53(5):21 − 31. (in Chinese with English abstract)]
|
[2] | SHENG Mingqiang,QIAN Zengzhen,YANG Wenzhi ,et al. Field compression and uplift tests on micropiles in collapsible loess under completely-soaked and saturated conditions[J]. Chinese Journal of Geotechnical Engineering,2021,43(12):2258 − 2264. |
[3] | KIM D,KIM G,KIM I,et al. Assessment of load sharing behavior for micropiled rafts installed with inclined condition[J]. Engineering Structures,2018,172:780 − 788. doi: 10.1016/j.engstruct.2018.06.058 |
[4] | YANG Yongsen,QIU Liuchao. MPM simulation of uplift resistance of enlarged base piles in sand[J]. Soils and Foundations,2020,60(5):1322 − 1330. doi: 10.1016/j.sandf.2020.08.003 |
[5] |
常林越,王卫东,吴江斌. 基于极限承载力试验的扩底抗拔桩承载特性数值模拟分析[J]. 岩土力学,2015,36(增刊1):657 − 663. [CHANG Linyue,WANG Weidong,WU Jiangbin. Numerical simulation analysis of uplift behavior of enlarged base piles based on uplift ultimate bearing capacity tests[J]. Rock and Soil Mechanics,2015,36(Sup 1):657 − 663. (in Chinese with English abstract)]
|
[6] | KYUNG D,KIM D,KIM G,et al. Vertical load-carrying behavior and design models for micropiles considering foundation configuration conditions[J]. Canadian Geotechnical Journal,2017,54(2):234 − 247. doi: 10.1139/cgj-2015-0472 |
[7] | ZHANG Rui,LUO Hui,LIU Zhengnan,et al. Study on anti-uplift effect of micro-steel-pipe pile on red-bedded soft rock subgrade[J]. Sustainability,2022,14(19):1 − 22. |
[8] |
武玉萍,付红安,王佳佳,等. 黄土地基微型桩水平承载力及群桩效应研究[J]. 应用力学学报,2022,39(3):543 − 553. [WU Yuping,FU Hongan,WANG Jiajia,et al. Horizontal bearing capacity and pile group effect of micro-pile on loess ground[J]. Chinese Journal of Applied Mechanics,2022,39(3):543 − 553. (in Chinese with English abstract)]
|
[9] |
张爱军,付红安,王佳佳,等. 黄土地基微型群桩抗拔承载力及群桩效应研究[J]. 建筑结构,2022,52(24):120 − 125. [ZHANG Aijun,FU Hongan,WANG Jiajia,et al. Study on uplift bearing capacity and group pile effect of micro-pile group in loess foundation[J]. Building Structure,2022,52(24):120 − 125. (in Chinese with English abstract)]
|
[10] | YIN Lianzhong,FAN Xiaoguang,WANG Songjiang. A study on application of squeezed branch pile in clay soil foundation[J]. IOP Conference Series:Earth and Environmental Science,2017,61:012091. doi: 10.1088/1755-1315/61/1/012091 |
[11] | LIN J G,HSU S Y,LIN S S. The new method to evaluate the uplift capacity of belled piles in sandy soil[J]. Journal of Marine Science and Technology,2015,23(4):523 − 533. |
[12] |
李飞,杨俊杰,宋琦,等. 多层土地基扩底抗拔桩离散元颗粒流研究[J]. 中南大学学报(自然科学版),2019,50(11):2859 − 2869. [LI Fei,YANG Junjie,SONG Qi,et al. Study on discrete element particle flow of multi-layered groundbased expanded bottom uplift pile[J]. Journal of Central South University (Science and Technology),2019,50(11):2859 − 2869. (in Chinese with English abstract)] doi: 10.11817/j.issn.1672-7207.2019.11.025
|
[13] |
王钦科,马建林,陈文龙,等. 上覆土嵌岩扩底桩抗拔承载特性离心模型试验及计算方法研究[J]. 岩土力学,2019,40(9):3405 − 3415. [WANG Qinke,MA Jianlin,CHEN Wenlong,et al. Centrifugal model tests and calculation method of uplift bearing capacity of rock-socketed pedestal pile overburden soil[J]. Rock and Soil Mechanics,2019,40(9):3405 − 3415. (in Chinese with English abstract)]
|
[14] | WANG Chengcan,HAN J T,KIM S. A field study on the load sharing behavior of a micropiled raft underpinned by a waveform micropile[J]. Canadian Geotechnical Journal,2022,59(7):1175 − 1187. doi: 10.1139/cgj-2020-0547 |
[15] | JANG Y E,HAN J T. Analysis of the shape effect on the axial performance of a waveform micropile by centrifuge model tests[J]. Acta Geotechnica,2019,14(2):505 − 518. doi: 10.1007/s11440-018-0657-2 |
[16] |
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—2014[S]. 北京:中国建筑工业出版社,2014. [Ministry of Housing and Urban-Rural Development of the People’s Republic of China. Technical code for testing of building foundation piles:JGJ 106—2014[S]. Beijing:China Architecture and Building Press,2014. (in Chinese)]
|
[17] |
闫玉平,肖世国. 双排抗滑桩加固滑坡的前桩后侧推力算法[J]. 水文地质工程地质,2021,48(4):55 − 63. [YAN Yuping,XIAO Shiguo. A calculation method for thrust on the fore piles of double-row stabilizing piles used to reinforce landslides[J]. Hydrogeology & Engineering Geology,2021,48(4):55 − 63. (in Chinese with English abstract)]
|
[18] |
李龙起,邓小雪,张帅,等. 非均匀地基中倾斜群桩竖向承载特性及群桩效应研究[J]. 工程科学与技术,2020,52(4):97 − 107. [LI Longqi,DENG Xiaoxue,ZHANG Shuai,et al. Study on vertical bearing capacity and pile group effect of inclined pile foundation in inhomogeneous strata[J]. Advanced Engineering Sciences,2020,52(4):97 − 107. (in Chinese with English abstract)]
|
[19] |
董青青,梁小丛. 考虑桩-土非线性接触的自平衡桩基测试有限元分析[J]. 水文地质工程地质,2013,40(1):73 − 78. [DONG Qingqing,LIANG Xiaocong. Analysis of self-balance pile test based on finite element method considering pile-soil non-linear contact[J]. Hydrogeology & Engineering Geology,2013,40(1):73 − 78. (in Chinese with English abstract)]
|
[20] |
唐孟雄,凌造,刘春林,等. 桩端型式对嵌岩随钻跟管桩承载性能的影响[J]. 岩石力学与工程学报,2022,41(增刊1):3053-3062. [TANG Mengxiong,LING Zao,LIU Chunlin,et al. Influence of pile toe type on bearing capacity of rock-socketed DPC piles[J]. Chinese Journal of Rock Mechanics and Engineering,2022,41(Sup 1):3053-3062. (in Chinese with English abstract)]
|
[21] |
司壹恒,刘干斌,周晔,等. 静止土压力系数原位测试装置设计及应用研究[J]. 水文地质工程地质,2020,47(3):79 − 85. [SI Yiheng,LIU Ganbin,ZHOU Ye,et al. Design and application of an in situ test device for the static earth pressure coefficient[J]. Hydrogeology & Engineering Geology,2020,47(3):79 − 85. (in Chinese with English abstract)]
|
[22] | ILAMPARUTHI K,DICKIN E A. The influence of soil reinforcement on the uplift behaviour of belled piles embedded in sand[J]. Geotextiles and Geomembranes,2001,19(1):1 − 22. doi: 10.1016/S0266-1144(00)00010-8 |
[23] | WANG Le,ZHANG Puyang,DING Hongyan,et al. The uplift capacity of single-plate helical pile in shallow dense sand including the influence of installation[J]. Marine Structures,2020,71:102697. doi: 10.1016/j.marstruc.2019.102697 |
[24] | LEI Jiangtao,ZHOU Zhijun,HAN Dandan,et al. Centrifuge model tests and settlement calculation of belled and multi-belled piles in loess area[J]. Soil Dynamics and Earthquake Engineering,2022,161:107425. doi: 10.1016/j.soildyn.2022.107425 |
[25] | PETER J A,LAKSHMANAN N,DEVADAS MANOHARAN P. Investigations on the static behavior of self-compacting concrete under-reamed piles[J]. Journal of Materials in Civil Engineering,2006,18(3):408 − 414. doi: 10.1061/(ASCE)0899-1561(2006)18:3(408) |
Grain-size analysis
Stressometer layout
Test loading device and its layout
Development of soil fracture around the pile
Distribution of pile axial force and pile side friction resistance
Relationship between load and displacement
Models of foundation soil and micropile groups
Construction concept, construction effect, and bearing mechanism of variable diameter micropile
Schematic diagram of the variable diameter micropile model
Pull-out, compressive, and horizontal load bearing characteristics of variable diameter micropile
Double-expanded micropile and pile cap
Bearing characteristics of double-expanded micropile and pile cap
Comparison of ultimate bearing capacity in different micropiles