Investigation on mechanical properties of structured soils subjected to axially loading-unloading under undrained conditions

HE Miao1,2 LIU Enlong1,2 CHEN Yajun3 TANG Yong1,2

(1.State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China 610065)
(2.College of Water Resource and Hydropower, Sichuan University, Chengdu, Sichuan, China 610065)
(3.Power China Kunming Engineering Corporation Limited, Kunming, Yunnan, China 650000)

【Abstract】To study the mechanical properties of structured soils under undrained conditions, the triaxial compression tests on reconstituted soils and two kinds of structured soils with initial stress-induced anisotropy and isotropy were carried out under axially loading-unloading-reloading. The soils were tested under consolidation undrained (CU) conditions at the confining pressures of 25 kPa, 50 kPa, 100 kPa, 200 kPa and 400 kPa, and the results of tests were analyzed with the binary-medium theory. It is found that the structured soils have stronger structures at lower consolidation stress. Meanwhile, Eave does not change significantly in different stress cycles. When the confining pressures are higher, the structures of soils are weakened, and their characteristics are similar to those of reconstituted soils. Because of the structure weakening and positive pore pressure, Eave decreases with the increase of εa. With the increase of the axial strain, the breakage rate of the bonded components and the soil particle spacing of friction components increase. In the meantime, the tendency of the volume contraction becomes more apparent when unloading.

【Keywords】 soil mechanics; structured soils; consolidation undrain conditions; axially loading-unloading tests; mechanical properties;

【DOI】

【Funds】 National Natural Science Foundation of China (51009103)

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(Translated by LIU T)

    References

    [1] SHEN Zhujiang. Engineering properties of soft soils and design of soft ground [J]. Chinese Journal of Geotechnical Engineering, 1998, 20 (1): 100–111 (in Chinese).

    [2] GONG Xiaonan, XIONG Chuanxiang, XIANG Kexiang, et al. The formation of clay structure and its influence on mechanical characteristics of clay [J]. Journal of Hydraulic Engineering, 2000, (10): 43–47 (in Chinese).

    [3] SCHMERTMANN J H. The mechanical aging of soils [J]. Journal of Geotechnical Engineering, 1991, 117 (9): 1288–1330.

    [4] KONG Lingwei, LU Haibo, WANG Ren, et al. Engineering properties and micromechanism of structural marine soil in Zhanjiang sea area [J]. Journal of Hydraulic Engineering, 2002, (9): 82–88 (in Chinese).

    [5] LU Haibo, WANG Ren, KONG Lingwei, et al. The influences of soil structure on compressibility of Qiongzhou strait soft marine clay [J]. Rock and Soil Mechanics, 2001, 22 (4): 467–469 (in Chinese).

    [6] CHEN Tielin, SHENZhujiang, YANG Daiquan. Numerical simulation on wetting deformation of collapsible loess ditch [J]. Journal of Hydraulic Engineering, 2005, 36 (3): 309–313, 320 (in Chinese).

    [7] CHENChanglu, SHAO Shengjun, SHE fangtao. Impact of structural change of soils on stability in slope excavation [J]. Chinese Journal of Geotechnical Engineering, 2011, 33 (12): 1938–1942 (in Chinese).

    [8] DESAI C S, TOTH J. Disturbed state constitutive modeling based on stress–strain and nondestructive behavior [J]. International Journal of Solids and Structures, 1996, 33 (11): 1619–1650.

    [9] LIU Weizheng, SHI Minglei, MIAO Linchang. Analysis of compressibility of structural soils based on disturbed state concept [J]. Rock and Soil Mechanics, 2010, 31 (11): 3475–3480 (in Chinese).

    [10] WANGChangming, KUANG Shaohua, WANG Gangcheng, et al. A method for describing consolidated-undrained shear behavior of structured soil [J]. Rock and Soil Mechanics, 2010, 31 (7): 2035–2039 (in Chinese).

    [11] SHEN Zhujiang. Mathematic model of structural soil-The key problem for soil mechanics in 21st century [J]. Chinese Journal of Geotechnical Engineering, 1996, 18 (1): 95–97 (in Chinese).

    [12] SHEN Zhujiang, LIU Enlong, CHEN Tielin. Generalized stress–strain relationship of binary medium model for geological materials [J]. Chinese Journal of Geotechnical Engineering, 2005, 27 (5): 489–494 (in Chinese).

    [13] LIU Enlong. Breakage mechanics for geomaterials: Breakage mechanism of structural blocks and binarymedium model [J]. Rock and Soil Mechanics, 2010, 31 (Supp. 1): 13–22 (in Chinese).

    [14] LEROUEIL S, VAUGHAN P. R. The general and congruent effects of structure in natural soils and week rocks [J]. Geotechnique, 1990, 40 (3): 467–488.

    [15] JIANG Mingjing, SHEN Zhujiang. A method of artificial preparation of structured clay samples [J]. Journal of Hydraulic Engineering, 1997, (1): 56–61 (in Chinese).

    [16] LIU Enlong, SHEN Zhujiang. Experimental study on mechanical properties of artificially structured soils [J]. Rock and Soil Mechanics, 2007, 28 (4): 679–683 (in Chinese).

    [17] LUO Kaitai, NIE Qing, ZHANG Shuyi, et al. Investigation on artificially structured soils with initial stress-induced anisotropy [J]. Rock and Soil Mechanics, 2013, 34 (10): 2815–2820 (in Chinese).

    [18] LI Guangxin, WU Shifeng. Experimental research on volume-contraction of soil under unloading and examination of its mechanism [J]. Chinese Journal of Geotechnical Engineering, 2002, 24 (1): 47–50 (in Chinese).

    [19] LIU Enlong, LUO Kaitai. Mechanical properties of artificially prepared structured soils subjected to axially cyclic loading [J]. Journal of Beijing University of Technology, 2012, 38 (2): 180–185 (in Chinese).

This Article

ISSN:1000-6915

CN: 42-1397/O3

Vol 36, No. 02, Pages 466-474

February 2017

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Article Outline

Abstract

  • 1 Introduction
  • 2 Overview of experiment
  • 3 Experimental results and analysis
  • 4 Conclusions
  • References