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Journal of Zhejiang University-SCIENCE A

, Volume 19, Issue 4, pp 277–288 | Cite as

Non-monotonic piezocone dissipation curves of backfills in a soil-bentonite slurry trench cutoff wall

  • Yu-chao Li
  • Xing Tong
  • Yun Chen
  • Han Ke
  • Yun-min Chen
  • Yi-duo Wen
  • Qian Pan
Article
  • 35 Downloads

Abstract

Pore pressure dissipation during piezocone testing provides a unique tool for estimating the hydraulic properties of in-situ backfills in soil-bentonite (SB) slurry trench cutoff walls. Six tests were performed in an SB slurry trench cutoff wall located in Jiangsu Province, China. The pore pressure dissipation curves obtained are non-monotonic, which, as far as the authors are aware, is reported for the first time in SB cutoff walls. The non-monotonic dissipation curves are attributed to the redistribution of excess pore pressures between the base soil clods and the rest of the backfill around the cone. Four existing interpretation methods are adopted to analyze the measured non-monotonic piezocone dissipation curves. The horizontal coefficients of consolidation (ch) of the backfills obtained by three methods are close to each other and in agreement with the results of fixed-ring consolidometer tests, while the other method gives a high overestimate. The hydraulic conductivities (kh) of the backfills are also estimated by four methods, three based on dissipation test results and one based on piezocone penetration data. kh estimated by consolidation theory are close to the results of flexible wall permeameter tests. Two empirical expressions for dissipation tests give relatively low kh, but the method based on penetration gives kh much larger than the laboratory test results.

Keywords

Piezocone Dissipation test Soil-bentonite cutoff wall Coefficient of consolidation Hydraulic conductivity 

土-膨润土隔离墙孔压静力触探非单调消散曲线 研究

概要

目的

土-膨润土隔离墙的水力特性可通过孔压静力触 探试验进行评价。本文旨在研究土-膨润土隔离墙 中孔压消散试验产生非单调孔压消散曲线的原 因,并对现有计算固结系数与渗透系数的方法在 土-膨润土隔离墙中的适用性进行分析。

创新点

1. 首次在土-膨润土隔离墙中测得非单调的孔压消 散曲线;2. 本文认为在土-膨润土隔离墙中测得非 单调孔压消散曲线是由于探头贯入过程中在填 料及其包裹的土块中产生的超孔压不一致引起 的,并且由于填料的低渗透性,孔压上升的时间 较长;3. 比较不同方法的分析结果,并推荐结果 与实测相近的计算方法作为工程应用。

方法

1. 通过室内一维固结试验和柔性壁渗透试验,分 别获得墙体材料的固结系数和渗透系数;2. 通过 现场土-膨润土隔离墙的孔压静力触探试验与孔 压消散试验,获得相应的力学参数与孔压消散曲 线; 3. 分别采用不同方法对墙体材料的固结系数 和渗透系数进行计算,并将计算结果与室内试验 结果进行比较。

结论

1. 填料的非均质性导致探头贯入过程中产生的超 孔压存在重分布,这使得土-膨润土隔离墙中产生 了非单调孔压消散曲线,并且由于填料的低渗透 性,测得孔压上升的时间较长;2. 四种计算固结 系数的方法中,有三种结果与室内一维固结试验 结果相近,另一种结果则明显偏大;3. 四种计算 渗透系数的方法中,基于太沙基固结理论的关系 式得到的结果与室内柔壁渗透试验结果相近,另 两种经验公式得到的结果偏小,而基于探头贯入 数据计算的渗透系数则偏大。

关键词

孔压静力触探 消散试验 土-膨润土隔离墙 固 结系数 渗透系数 

CLC number

TU45 

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Copyright information

© Zhejiang University and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.MOE Key Laboratory of Soft Soils and Geoenvironmental EngineeringZhejiang UniversityHangzhouChina
  2. 2.Architectural Design and Research Institute of Zhejiang University Co., Ltd.HangzhouChina
  3. 3.College of Civil Engineering and ArchitectureZhejiang University of Water Resources and Electric PowerHangzhouChina

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