Calculation Method of Uplift Capacity of Pile-Anchor Composite Foundation and Influence of Parameters

doi:10.16183/j.cnki.jsjtu.2021.366

Abstract

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

CLC Number:

TM753
TU470

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.

Figures/Tables 12

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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