摘要
工程中多采用基础上拔静载试验中基础顶部荷载-位移曲线获取基础的承载力,忽略了基础周围土体的变形破坏过程,而实际工程中均是基础周围地基土体发生破坏。为研究扩底基础与其周围土体在抗拔承载特性方面的差异,以黄土地基中的9个扩底基础为研究对象,通过现场全尺寸基础的上拔静载试验,分别获得基础顶部与地表的上拔荷载-位移曲线,并进一步对基顶与地表处的荷载-位移曲线变化特征、抗拔承载力取值进行对比分析。结果表明,两处的荷载-位移曲线变化特征相似,相同上拔荷载作用下地表处的位移量均小于基础处位移量,差异以初始弹性阶段变形最为突出;两者在弹性极限荷载Q_(L1)取值方面,相差较大,但随着地基基础由弹性向塑性发展,差异逐渐减小,两者塑性极限荷载Q_(L2)取值基本相同。结合上拔扩底基础的破坏模式,分析出上述差异主要由于基础与周围土体之间变形不协调所致,加载初期基础顶部的上拔位移包括基础拔出量和上部土体压缩量,当上部土体压密后压缩变形消失,地基基础成为一个整体,上拔基础与周围土体的变形趋于协调。
The uplift bearing capacity of spread footing can be obtained through the footing uplift static loading test. At present, the load-displacement curves at the top of footing are usually used as the basis in this process. However, the deformation and failure behaviors of the soil around footing are ignored frequently, which often occurred in footing projects. Aiming at this problem, the difference of the uplift resistance characteristics between the spread footing and the foundation soil are studied. The uplift static loading tests of nine full-size spread footings are carried out. And the load-displacement curves at the top of footing and the ground surface are obtained. The comparative studies are carried out through analyzing the changing features of the load-displacement curves and the values of the uplift bearing capacity. The results show that both the load-displacement curves at the top of footing and the ground surface vary gradually. Under the same load, the displacement at the ground surface is less than that at the top of footing. And the difference between them is most significant at the elastic stage. Moreover, the values of the elastic limit load Q(L1) obtained from the curves at the two positions show the obvious difference. With the transition from the initial straight line to the final curve, the difference will decrease gradually. Finally, they get the same values of the plastic limit load Q(L2). Based on the analysis of the failure behavior of spread footing, the incompatible deformation between the footings and the ground soil is regarded as the main reason for this discrepancy. At the beginning of the tests, the footing displacement value is the sum of the soil compression quantity and the pulling out amount of the footing, and when the soil upon the enlarged head of the footing is compacted completely, the footing together the soil form a whole and the displacements for the footing and the ground soil tend to coordinate.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2016年第S2期476-482,共7页
Rock and Soil Mechanics
基金
国家电网公司科技项目(No.GCB17201400162)~~
关键词
上拔扩底基础
黄土地基
荷载位移规律
抗拔承载力
承载特性的差异性
uplift spread footing
loess foundation
load-displacement law
uplift bearing capacity
difference of uplift resistance characteristics
