分级加卸载下南海珊瑚泥一维固结长期变形试验及模型研究  

Long-term deformation test and model study of one-dimensional consolidation of South China Sea coral mud under graded loading and unloading

作　　者：沈扬[1] 邓珏 翁禾 阳龙 SHEN Yang;DENG Jue;WENG He;YANG Long(Key Laboratory of Geomechanics and Embankment Engineering of Ministry of Education,Hohai University,Nanjing,Jiangsu 210098,China)

机构地区：[1]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210098

出　　处：《岩土力学》2023年第3期685-696,共12页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51979087)。

摘　　要：南海珊瑚泥是珊瑚群体死后的骨胳、碎屑聚积形成的海洋岩土体钙质软泥,具有特殊的工程性状,研究其在荷载作用下与时间相关的长期非线性变形对吹填岛礁建设和长期稳定分析具有重要意义。对珊瑚泥进行了3组不同加卸载方案的一维固结压缩试验,通过改变加载时间与加卸载循环圈数探究应力历史对其长期变形性质的影响,并针对珊瑚泥在加卸载试验条件下呈现出的瞬时变形、延时衰减与延时稳定变形3阶段规律,采用改进的Burgers模型拟合不同竖向应力作用下的ε-t(应变-时间)曲线,具有较高拟合精度。同时分析模型参数后发现,随着分级加载时间提高,瞬时应变增量及其增长率下降,最终荷载下的延时衰减时间缩短,延时稳定应变速率及最终荷载下的总应变增量减小。同一加卸载循环圈数中,同竖向应力下卸载阶段的瞬时应变增量小于加载阶段。随着加卸载循环圈数的增加,加、卸载各阶段瞬时应变增量均减小且二者相近,延时衰减时间缩短,延时稳定应变速率及最终荷载下的总应变增量减小。研究了分级加载时间与加卸载循环圈数对珊瑚泥长期变形性质的影响,旨在为岛礁建设中的堆载预压方案提供理论依据。South China Sea coral mud is a calcareous ooze of marine rock and soil formed by the accumulation of bones and debris after the death of coral groups,which has special engineering properties.It is significant to investigate its time dependent long-term nonlinear deformation under load for the construction and long-term stability analysis of dredger fill islands and reefs.Three groups of one-dimensional consolidation compression tests of coral mud with different loading and unloading schemes were carried out,and the influence of stress history on its long-term deformation properties was explored by changing the loading time and loading-unloading loops.According to the three-stage law of coral mud’s instantaneous deformation,delayed attenuation deformation and delayed stable deformation under loading and unloading test conditions,the improved Burgers model was used to fitε-t curves under different vertical stresses,which has high fitting accuracy.Meanwhile,after analyzing the model parameters,it was found that the instantaneous strain increment and its growth rate decrease with the increase of graded loading time,the duration of delayed attenuation under the final load decreases,and the delayed stable strain rate and the total strain increment under the final load decrease.In the same loading-unloading loops,the instantaneous strain increment in the unloading stage is smaller than that in the loading stage under the same vertical stresses.With the increase of loading-unloading loops,the instantaneous strain increment in each stage of loading and unloading decreases and is close to each other,the duration of delayed attenuation deformation,the delayed stable strain rate and total strain increment under the final load decrease.The effects of graded loading time and loading and unloading cycles on the long-term deformation properties of coral mud were studied to provide theoretical basis for surcharge preloading scheme in island reef construction.

关 键 词：南海珊瑚泥 分级加卸载 长期非线性变形 改进Burgers模型 模型参数 

分 类 号：TU411[建筑科学—岩土工程]