长期受荷桩极限承载力的预测

doi:10.16183/j.cnki.jsjtu.2019.348

摘要/Abstract

摘要：

为准确预测长期受荷桩的极限承载力,对桩基承载力时间效应经验公式的不足进行了探讨,并基于天然饱和黏土地基静压桩承载力时效性研究的理论成果,对经历长期受荷的旧桩承载力的影响因素进行了分析.在此基础上,采用相关研究机构的桩基承载试验数据开展分析,提出了考虑桩基承载力时间效应的静压桩极限承载力计算公式;提出了桩侧阻力时效系数γ,探讨了影响γ的一些关键因素,并基于试验数据提出了采用土体性质参数计算γ的方法.通过现场试验对本文方法的准确性进行了验证.研究结果表明:采用γ可对现行规范中单桩承载力计算公式进行修正,在保证安全性的前提下,获得更高的旧桩单桩承载力设计值;而γ则可采用不排水抗剪强度S_u 及塑性指数I_P进行预测.

关键词: 旧桩, 极限承载力, 时效系数, 不排水抗剪强度, 现场试验

Abstract:

To predict the ultimate bearing capacity of long-term loaded piles, the shortcomings of current empirical formulas of pile bearing capacity considering time effect are discussed. Based on the current research of the bearing capacity of static bearing piles in natural saturated clay, factors for the bearing capacity of long-term loaded old piles are analyzed. Then, based on analysis of the data from pile foundation bearing tests, the formula for calculating the ultimate bearing capacity of jacked piles considering the time effect and the current pile foundation technical code is proposed, in which the pile side resistance aging coefficient of pile side resistance is proposed, and some factors for the aging coefficient are discussed. Based on the experimental data, a method for calculating the parameters in the formula by using soil properties is proposed. The accuracy of the proposed method is verified by a field test. The results show that this pile side resistance aging coefficient can predict the bearing capacity of single pile under current code, increase the design value of the bearing capacity of old piles while ensuring safety. By using the undrained shear strength and plasticity index, the pile side resistance aging coefficient can be predicted.

Key words: old pile, ultimate bearing capacity, aging coefficient, undrained shear strength, field test

中图分类号:

TU473

李镜培, 徐子涵. 长期受荷桩极限承载力的预测[J]. 上海交通大学学报, 2021, 55(4): 380-386.

LI Jingpei, XU Zihan. Prediction of Ultimate Bearing Capacity of Long-Term Loaded Piles[J]. Journal of Shanghai Jiao Tong University, 2021, 55(4): 380-386.

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土的类别	休止时间/d
砂土	7
粉土	10
非饱和黏性土	15
饱和黏性土	25

土层名称	H/m	γ/ (kN·m^-3)	e	c/kPa	φ/(°)	E_s/ MPa
杂填土	1.53	-	-	-	-	-
浜土	1.60	-	-	-	-	-
粉质黏土	1.75	18.9	1.052	25	31.7	5.46
淤泥质粉黏土	1.71	17.6	1.187	16	27.5	3.67
砂质粉土	2.38	18.7	1.003	2	32.5	10.94
淤泥质黏土	9.39	16.6	1.485	14	24.8	2.17
黏土	10.03	17.4	1.219	16	28.4	3.14
粉质黏土	8.93	17.8	1.065	16	31.9	4.07
砂质粉土	10.04	18.5	0.988	4	31.8	9.12
粉质黏土夹砂	10.97	17.5	0.980	17	31.7	4.10