沉井接高过程中砂桩复合地基固结承载特性

doi:10.16183/j.cnki.jsjtu.2020.058

摘要/Abstract

摘要：

为分析沉井接高过程中固结对复合地基承载力的影响,以某大型陆上沉井基础的砂桩复合地基工程为背景,探讨了沉井接高过程中砂桩复合地基的固结特性,分析了加荷历时和砂桩置换率等因素的影响.基于桩土面积比法和桩土应力比法推导了考虑固结影响的砂桩复合地基极限承载力公式,并与复合地基实测承载力进行对比.结果表明:两种分析方法得到的复合地基承载力时程曲线较为接近,且初始承载力均小于复合地基实测承载力,而固结完成后的承载力比复合地基天然强度分别提高了68%和80%.该方法考虑了沉井接高过程中地基固结对其承载力的影响,避免了因低估地基的实际承载力而导致沉井滞沉问题,可为考虑固结影响的复合地基极限承载力计算和制定合理的沉井施工方案提供参考.

关键词: 砂桩, 复合地基, 固结, 承载力, 面积比, 应力比

Abstract:

To study the influence of consolidation on the bearing capacity of the composite foundation in the process of caisson heightening, the consolidation characteristics of the sand pile composite foundation in the process of caisson heightening are discussed based on the sand pile composite foundation engineering of a large-scale onshore caisson foundation. The influence of loading duration and replacement rate of the sand pile are analyzed. Based on the area ratio method of pile-soil and the pile-soil stress ratio method, the formula of the ultimate bearing capacity of the sand pile composite foundation considering the consolidation effect is derived, which is compared with the measured value of the ultimate bearing capacity of the foundation. The results show that the time history curves of the bearing capacity of the composite foundation based on the two methods are close, and the initial bearing capacity is less than the measured value of bearing capacity, while the bearing capacity after consolidation is 68% and 80% higher than the natural strength of the composite foundation. This method considers the influence of consolidation on the bearing capacity of the foundation in the process of caisson heightening. It can avoid the problem of stagnant sinking of open caisson as it underestimates the actual bearing capacity of the foundation, and provides suggestions for calculation of ultimate bearing capacity of the composite foundation considering the influence of consolidation and formulating the reasonable construction scheme of open caisson.

Key words: sand pile, composite foundation, consolidation, bearing capacity, area ratio, stress ratio

中图分类号:

TD752.1

陈培帅, 潘亚洲, 梁发云, 李德杰. 沉井接高过程中砂桩复合地基固结承载特性[J]. 上海交通大学学报, 2021, 55(6): 707-715.

CHEN Peishuai, PAN Yazhou, LIANG Fayun, LI Dejie. Consolidation Characteristics and Bearing Behavior of Sand Pile Composite Foundation in Caisson Heightening[J]. Journal of Shanghai Jiao Tong University, 2021, 55(6): 707-715.

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编号	土层	h/m	c/kPa	φ/(°)	ρ/(g·cm^-3)	P/kPa
1	淤泥质黏土(砂桩加固)	9.32	8.8	3.3	1.74	402.2
2	淤泥质黏土夹粉砂(砂桩加固)	3.41	8.7	3.6	1.72	413.8
3	淤泥(砂桩加固)	15	7.4	2.5	1.64	354.2
4	淤泥质黏土(砂桩加固)	4.88	13.2	7.1	1.71	381.1
5	黏土	5.74	17.1	8.3	1.76	240
6	黏土夹粉砂	5.12	26.2	8.6	1.78	300

工况	x	P_T/kPa	P_B/kPa	t_c/d
1	1	57.7	19.1	26
2	2	110.7	36.6	52
3	3	142.3	47.1	78
4	4	181.8	60.1	104

工况	实测值	P₀/kPa		P_0.4/kPa				P_0.7/kPa				P₁/kPa
工况	实测值	面积比法	应力比法	面积比法		应力比法		面积比法		应力比法		面积比法		应力比法
1	402	140	225	203	251		272		304		357		383
2				244	274		364		375		517		528
3				261	288		406		417		596		615
4				275	305		446		471		675		724

m	实测值	P'₀/kPa		P'_0.4/kPa		P'_0.7/kPa		P'₁/kPa
m	实测值	面积比法	应力比法	面积比法	应力比法	面积比法	应力比法	面积比法	应力比法
10%	-	243	183	385	344	491	465	598	586
20%	-	266	200	404	375	508	508	612	640
36%	402	346	226	477	424	576	574	675	724
50%	-	416	250	541	466	635	630	730	794