Calculation Method of Bearing Capacity of Screw Pile Based on Unified Strength Theory

doi:10.16183/j.cnki.jsjtu.2021.077

Abstract

Abstract:

Based on the unified strength theory and the Terzaghi limit equilibrium theory, the ultimate bearing capacity of screw pile has been deduced. The method to determine the critical pitch and calculate the ultimate bearing capacity of the screw pile in two failure modes including the independent bearing failure mode and the cylinder shear failure mode has been proposed. The influence of the unified strength theoretical parameter b and the key parameters of concrete screw pile on the ultimate bearing capacity has been analyzed. The results show that the ultimate bearing capacity of the screw pile is 1.5—2 times that of the round pile with the same outer diameter. The ultimate bearing capacity of the screw teeth is mainly determined by the cohesion, the internal friction angle, and the buried depth of the soil. As b increases from 0 to 1, the theoretical value of the ultimate bearing capacity of the screw pile increases by nearly 48%. As the influence of the medium principal stress on the soil strength is considered, the theoretical calculation results of the bearing capacity of the concrete screw pile will be more accurate. Of the parameters of the concrete screw pile, the screw height b_h has the greatest influence on the ultimate bearing capacity, while the screw thickness t has little influence on the bearing capacity. When designing threaded pile, the height of screw can be increased to some extent to improve the ultimate bearing capacity of the screw pile.

Key words: screw pile, unified strength theory, field monitoring, Terzaghi limit equilibrium principle, critical screw pitch

CLC Number:

TU470

MA Jiakuan, LUO Lijuan, REN Xiang, SHI Hang, YIN Yimo. Calculation Method of Bearing Capacity of Screw Pile Based on Unified Strength Theory[J]. Journal of Shanghai Jiao Tong University, 2022, 56(6): 754-763.

Figures/Tables 12

Fig.1

Fig.2

Fig.3

Fig.4

Fig.5

Fig.6

Fig.7

Fig.8

Tab.1

Tab.2

Fig.9

Fig.10

References 27

[1]	吴敏, 李波扬. 全螺旋灌注桩-螺纹桩竖向承载力初探[J]. 武汉大学学报(工学版), 2002, 35(5): 109-112.
	WU Min, LI Boyang. Primary discussion on vertical load bearing capacity of screwed filling piles[J]. Engineering Journal of Wuhan University, 2002, 35(5): 109-112.
[2]	徐春华, 张小冬, 徐学燕. 混凝土灌注螺纹桩设计参数的应用研究[J]. 工业建筑, 2010, 40(10): 91-94.
	XU Chunhua, ZHANG Xiaodong, XU Xueyan. Application study on design parameters of cast-in-place concrete screw pile[J]. Industrial Construction, 2010, 40(10): 91-94.
[3]	郑军锋, 范德全, 陈济熙, 等. 挤密螺纹桩复合地基桩土应力比现场试验研究[J]. 铁道科学与工程学报, 2019, 16(12): 3005-3012.
	ZHENG Junfeng, FAN Dequan, CHEN Jixi, et al. Field experimental study on pile-soil stress ratio of composite foundation under squeeze tightly threaded piles[J]. Journal of Railway Science and Engineering, 2019, 16(12): 3005-3012.
[4]	冷伍明, 魏广帅, 聂如松, 等. 螺纹桩竖向承载特性及承载机理研究[J]. 铁道工程学报, 2020, 37(5): 1-6.
	LENG Wuming, WEI Guangshuai, NIE Rusong, et al. Research on the vertical bearing characteristics and bearing mechanism of screw pile[J]. Journal of Railway Engineering Society, 2020, 37(5): 1-6.
[5]	李成巍, 陈锦剑, 吴琼, 等. 灌注螺纹桩承载机理与计算方法[J]. 上海交通大学学报, 2010, 44(6): 726-730.
	LI Chengwei, CHEN Jinjian, WU Qiong, et al. Bearing mechanism and calculation method of screw pile[J]. Journal of Shanghai Jiao Tong University, 2010, 44(6): 726-730.
[6]	王国才, 赵志明, 奚灵智, 等. 螺纹桩竖向承载特性研究[J]. 浙江工业大学学报, 2020, 48(1): 90-96.
	WANG Guocai, ZHAO Zhiming, XI Lingzhi, et al. Research on vertical load bearing characteristics of thread piles[J]. Journal of Zhejiang University of Technology, 2020, 48(1): 90-96.
[7]	孟振, 陈锦剑, 王建华, 等. 砂土中螺纹桩承载特性的模型试验研究[J]. 岩土力学, 2012, 33(Sup.1): 141-145.
	MENG Zhen, CHEN Jinjian, WANG Jianhua, et al. Study of model test on bearing capacity of screw piles in sand[J]. Rock and Soil Mechanics, 2012, 33(Sup.1): 141-145.
[8]	蒋鹏程. 粉土地基CFG桩与螺杆桩复合地基承载特性对比分析[J]. 铁道学报, 2019, 41(4): 125-132.
	JIANG Pengcheng. Comparative analysis of bearing behaviors of CFG pile and screw pile composite foundation in silt foundation[J]. Journal of the China Railway Society, 2019, 41(4): 125-132.
[9]	马文杰, 王博林, 王旭, 等. 螺纹桩承载特性的初步探讨[J]. 建筑结构, 2018, 48(Sup.1): 738-741.
	MA Wenjie, WANG Bolin, WANG Xu, et al. Preliminary study on load characteristics of thread pile[J]. Building Structure, 2018, 48(Sup.1): 738-741.
[10]	冯浙. 砂土地基中螺杆桩竖向承载特性的模型试验研究[J]. 建筑科学, 2019, 35(5): 97-102.
	FENG Zhe. Model test study on vertical bearing characteristics of screw pile in sandy soil[J]. Building Science, 2019, 35(5): 97-102.
[11]	王曙光, 冯浙, 唐建中, 等. 竖向荷载作用下螺杆灌注桩受压承载机理的试验研究[J]. 岩土工程学报, 2021, 43(2): 383-389.
	WANG Shuguang, FENG Zhe, TANG Jianzhong, et al. Experimental study on bearing mechanism of screw cast-in-place piles under vertical loads[J]. Chinese Journal of Geotechnical Engineering, 2021, 43(2): 383-389.
[12]	TROFIMENKOV J G, MARUIPOLSHII L G. Screw piles used for mast and tower foundations[C]∥Proceedings of the 6th International Conference on Soil Mechanics and Foundation Engineering. Toronto, Canada: University of Toronto Press, 1965: 328-351.
[13]	ZHANG D. Predicting capacity of helical screw piles in Alberta soils[D]. Edmonton, Canada: University of Alberta, 1999.
[14]	SAKR M. Lateral resistance of high capacity helical piles: Case study[C]∥Proceedings of the 63rd Canadian Geotechnical and 6th Canadian Permafrost Conference. Calgary, Canada: Canada Geotechnical Society, 2010: 402-412.
[15]	董天文, 梁力, 王明恕, 等. 极限荷载条件下螺旋桩的螺距设计与承载力计算[J]. 岩土工程学报, 2006, 28(11): 2031-2034.
	DONG Tianwen, LIANG Li, WANG Mingshu, et al. Pitch of screws and bearing capacity of screw piles under ultimate load[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(11): 2031-2034.
[16]	孟振. 全螺纹灌注挤土桩施工影响与承载特性研究[D]. 上海: 上海交通大学, 2017.
	MENG Zhen. Install effects and bearing capacity of drilled displacement piles with a screw-shaped shaft[D]. Shanghai: Shanghai Jiao Tong University, 2017.
[17]	高江平, 刘雯支, 杨继强. 基于三剪应力统一强度理论的硬壳层软土地基承载力公式[J]. 岩土工程学报, 2019, 41(12): 2331-2337.
	GAO Jiangping, LIU Wenzhi, YANG Jiqiang. Formulas for bearing capacity of soft soil foundations with hard crust based on three-shear stress unified strength theory[J]. Chinese Journal of Geotechnical Engineering, 2019, 41(12): 2331-2337.
[18]	俞茂宏, 武霞霞, 史俊, 等. 确定土体破坏准则的一个新方法[J]. 西安交通大学学报, 2020, 54(8): 1-10.
	YU Maohong, WU Xiaxia, SHI Jun, et al. A new strategy for determining failure criteria of soil[J]. Journal of Xi’an Jiaotong University, 2020, 54(8): 1-10.
[19]	张常光, 胡云世, 赵均海. 平面应变条件下非饱和土抗剪强度统一解及应用[J]. 岩土工程学报, 2011, 33(1): 32-37.
	ZHANG Changguang, HU Yunshi, ZHAO Junhai. Unified solution of shear strength for unsaturated soil under plane strain condition and its application[J]. Chinese Journal of Geotechnical Engineering, 2011, 33(1): 32-37.
[20]	杨继强, 孙昕, 崔向东. 基于双剪统一强度理论的地基承载力计算方法研究[J]. 岩石力学与工程学报, 2021, 40(9): 1923-1932.
	YANG Jiqiang, SUN Xin, CUI Xiangdong. Research on calculation method of foundation bearing capacity based on double shear unified strength theory[J]. Chinese Journal of Rock Mechanics and Engineering, 2021, 40(9): 1923-1932.
[21]	张常光, 晏青, 周菲, 等. 不同吸力分布下条形地基极限承载力解答[J]. 岩石力学与工程学报, 2018, 37(5): 1237-1251.
	ZHANG Changguang, YAN Qing, ZHOU Fei, et al. Formulas of ultimate bearing capacity for strip foundation on unsaturated soils with different suction distributions[J]. Chinese Journal of Rock Mechanics and Engineering, 2018, 37(5): 1237-1251.
[22]	高大钊, 袁聚云. 土质学与土力学[M]. 第3版. 北京: 人民交通出版社, 2001.
	GAO Dazhao, YUAN Juyun. Soil science and soil mechanics[M]. 3rd ed. Beijing: China Communications Press, 2001.
[23]	RAO S N, PRASAD Y V S N, SHETTY M D. The behaviour of model screw piles in cohesive soils[J]. Soils and Foundations, 1991, 31(2): 35-50. doi: 10.3208/sandf1972.31.2_35 URL
[24]	SAKR M. Performance of helical piles in oil sand[J]. Canadian Geotechnical Journal, 2009, 46(9): 1046-1061. doi: 10.1139/T09-044 URL
[25]	中华人民共和国住房和城乡建设部. 螺纹桩技术规程: JGJ/T 379—2016[S]. 北京: 中国建筑工业出版社, 2016.
	Ministry of Housing and Urban-Rural Development of the People’s Republic of China. Technical specification for screw concrete pile:JGJ/T 379—2016 [S]. Beijing: China Architecture and Building Press, 2016.
[26]	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.
	Ministry of Housing and Urban-Rural Development of the People’s Republic of China. Technical code for building pile foundations: JGJ 94—2008[S]. Beijing: China Architecture and Building Press, 2008.
[27]	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, 2016.
	Ministry of Housing and Urban-Rural Development of the People’s Republic of China. Technical code for testing of building foundation pile: JGJ 106—2014[S]. Beijing: China Architecture and Building Press, 2016.

层号	层厚/m	液性指数	φ/(°)	c/kPa
1	2.25	0.14	13.0	35.4
2	3.80	0.51	19.4	25.9
3	2.00	0.35	16.0	36.4
4	5.05	0.51	11.4	23.6

极限承载力	分项	分项承载力/kN	分项占比/%	总占比/%
Q_ul1	黏聚力	571.5	45.1	85.8
	埋深	685.1	54.2	-
	滑块自重	9.4	0.7	-
Q_ul2	-	83.6	-	5.7
Q_ul3	-	125.7	-	8.5
Q_ult	-	1475.3	-	100