桩-锚复合基础上拔承载力计算和参数影响研究

doi:10.16183/j.cnki.jsjtu.2021.366

摘要/Abstract

摘要：

针对山区广泛存在的上覆土、下卧岩的地质条件,一种桩-锚复合基础被应用在输电线路杆塔工程中.为了揭示其上拔承载机理,完善抗拔承载力和承载力发挥系数k的计算方法,通过PLAXIS 3D有限元软件建立了现场试验案例的验证模型,在此基础上进行了参数研究,研究了岩土体弹性模量和黏聚力以及基础工况对k值的影响.结果表明,基础上部桩和下部锚杆部分的上拔承载极限状态不同步,基础桩、锚部分承载比和承载力发挥系数k与地质和基础构造相关.结合参数研究和上拔荷载与位移关系的相关解析解,提出了考虑基础自重的上拔承载力发挥系数k的理论计算方法,通过与现场试验和有限元结果的对比,验证了本方法的正确性,为该类新型基础的设计和应用提供了理论参考.

关键词: 桩-锚基础, 抗拔承载力, 数值分析, 参数研究, 承载力发挥系数

Abstract:

In view of the extensive geology of overlying soil and underlying rock in mountainous areas, a pile-anchor composite foundation has been used in transmission line tower engineering. To reveal the uplift bearing mechanism and supplement the calculation method of the uplift capacity and the bearing exertion coefficient k, the verification model of field test case was established by using the PLAXIS 3D finite element software to study this problem. Parameter studies were conducted on this foundation. The influence of elastic modulus and cohesion of rock and soil and foundation condition on coefficient k was studied. The results show that there is asynchronism of ultimate uplift limit state of upper and lower parts of the pile-anchor foundation. The bearing ratio and coefficient k of the upper and lower parts of the foundation are related to geology and foundation structure. In combination with the parameter study and the relevant analytical solution of the relationship between the uplift load and the displacement, a theoretical calculation method of the coefficient k considering the foundation weight was proposed. Three test cases were used to perform confirmatory calculations for this method. By comparing with field tests and numerical calculation results, the correctness of this method has been verified. This method provides a theoretical reference for the design and application of this type of new foundation.

Key words: pile-anchor foundation, uplift capacity, numerical analysis, parameter research, bearing exertion coefficient

中图分类号:

TM753
TU470

孙义舟, 孙宏磊, 蔡袁强. 桩-锚复合基础上拔承载力计算和参数影响研究[J]. 上海交通大学学报, 2022, 56(6): 701-709.

SUN Yizhou, SUN Honglei, CAI Yuanqiang. Calculation Method of Uplift Capacity of Pile-Anchor Composite Foundation and Influence of Parameters[J]. Journal of Shanghai Jiao Tong University, 2022, 56(6): 701-709.

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编号	地层	厚度/ m	ρ/ (kN·m^-3)	c/ kPa	φ/ (°)	E/ MPa
FH1-6	粉质黏土	4.8	19	20	16.65	80
	微风化石灰岩	>10	20	90	30	200

类型	编号	c_s/kPa	c_r/kPa	E_s/MPa	E_r/MPa
验证模型	FH1-6	20	90	80	200
土黏聚力	SC-1	15	90	80	200
	SC-2	25
	SC-3	30
岩黏聚力	RC-1	20	80	80	200
	RC-2		100
	RC-3		110
土弹性模量	SE-1	20	90	50	200
	SE-2			100
	SE-3			150
岩弹性模量	RE-1	20	90	80	100
	RE-2				150
	RE-3				250

类型	编号	h₁/m	e/m	h₂/m	n
验证模型	FH1-6	4.8	0	4	6
嵌岩长度	ER-1	4.8	0.2	4	6
	ER-2		0.4
	ER-3		0.6
锚长	AL-1	4.8	0	3.0	6
	AL-2			3.5
	AL-3			4.5
锚数	AN-1	4.8	0	4	4
	AN-2				8

基础	实测和数值			理论计算
基础	k₁	k₂	P_k/kN	k₁	k₂	P_k/kN
FH1-6	1.00	0.76	1500	1.00	0.83	1586
FH1-SB	0.98	1.00	1200	0.90	1.00	1166
FH2-SB	0.95	1.00	1300	0.84	1.00	1248