Progressive yielding/softening of soil–cement columns under embankment loading: a case study

IF 5.6 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL Acta Geotechnica Pub Date : 2024-05-13 DOI:10.1007/s11440-024-02346-4
Jin-chun Chai, Takenori Hino, Yafei Qiao, Wenqi Ding
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Abstract

An embankment with a fill thickness of 7.5 m was built on a soil–cement column-slab system improved about 15.8 m thick soft subsoil. The embankment was stable for about 5 months after construction, and then, its settlement rate increased rapidly. To avoid the failure of the embankment, 1.0 m thick fill was removed and the embankment was stabilized again. The results of field investigation using all-core boring through a cement deep mixing (CDM) column under the central of the embankment and 3D finite element analysis (FEA) indicate that the most likely mechanism for the observed field behavior is progressive yielding/softening of the upper part of the columns. In FEA, the yielding/softening of the upper part of columns was simulated using strength reduction option and the start of the softening was triggered manually at the time of observed rapid increase in the settlement rate. This case history indicates that in field quality control of CDM columns, identifying local weak part(s) by continuous measuring the strength of the column samples retrieved from all-core boring is important. It is suggested that combination of unconfined compression test as well as needle penetration tests for the cores retrieved can be an economic and practical way to do this.

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路堤荷载下土灰柱的渐进屈服/软化:案例研究
在土-水泥柱-板系统上修建了填土厚度为 7.5 米的堤坝,改良了约 15.8 米厚的软基土。堤坝在建成后约 5 个月内保持稳定,随后沉降速度迅速加快。为了避免路堤坍塌,我们清除了 1.0 米厚的填土,并重新稳固了路堤。通过对堤坝中央下方的水泥深层搅拌(CDM)柱进行全芯钻孔实地调查和三维有限元分析(FEA)的结果表明,实地观察到的行为最可能的机制是柱子上部的逐渐屈服/软化。在有限元分析中,使用强度降低选项模拟了支柱上部的屈服/软化,并在观察到沉降速度快速增加时手动触发软化开始。这一案例表明,在对 CDM 柱进行现场质量控制时,通过连续测量从全岩心钻孔取回的柱样本的强度来识别局部薄弱部分非常重要。建议对取回的岩心结合进行无约束压缩试验和针入度试验,这是一种经济实用的方法。
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来源期刊
Acta Geotechnica
Acta Geotechnica ENGINEERING, GEOLOGICAL-
CiteScore
9.90
自引率
17.50%
发文量
297
审稿时长
4 months
期刊介绍: Acta Geotechnica is an international journal devoted to the publication and dissemination of basic and applied research in geoengineering – an interdisciplinary field dealing with geomaterials such as soils and rocks. Coverage emphasizes the interplay between geomechanical models and their engineering applications. The journal presents original research papers on fundamental concepts in geomechanics and their novel applications in geoengineering based on experimental, analytical and/or numerical approaches. The main purpose of the journal is to foster understanding of the fundamental mechanisms behind the phenomena and processes in geomaterials, from kilometer-scale problems as they occur in geoscience, and down to the nano-scale, with their potential impact on geoengineering. The journal strives to report and archive progress in the field in a timely manner, presenting research papers, review articles, short notes and letters to the editors.
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