Advertisement

Science China Technological Sciences

, Volume 61, Issue 8, pp 1127–1136 | Cite as

Influence of water content and shear rate on the mechanical behavior of soil-rock mixtures

  • HouZhen Wei
  • WenJie Xu
  • ChangFu Wei
  • QingShan Meng
Article
  • 49 Downloads

Abstract

Soil-rock mixtures (S-RMs) are widely distributed in the nature. The mesoscopic deformation and failure mechanisms as well as the macro-mechanical behaviors of the S-RMs depend largely upon the rate of deformation, water content and particle sizes. In this research, a series of large-scale direct shear tests with different water contents and different grain-size distributions were conducted to study the influence of the aforementioned factors on the mechanical properties of the S-RMs. Due to the effect of the rock blocks’ breakage in the S-RMs, the relationship between the shear strength and the vertical stress of S-RM follows a power law instead of a linear one. It is found that there exists a threshold value for the vertical stress during the shearing process, below which the soil strength is mainly determined by the inter-locking of particles and the re-arrangement of meso-structure, and otherwise large-sized rock blocks are gradually broken into smaller fragments, resulting in a decrease in the soil strength. The shear rate can also significantly influence the degree of particle breakage and the meso-structural rearrangement of the S-RMs, namely, under low shear rate, the particles of the samples are fully broken resulting in enhanced macro-strength. As a result, the lower the shear rate, the higher the macroscopic strength. So under unsaturated conditions, the water content will affect the strength of the S-RMs by reducing the strength of rock blocks. As the water content increases, the soil strength decreases gradually, and assumes a moderate value when the water content reaches 8%. At the same water content, the soil strength increases with the sizes of large rock blocks. For the occlusion, breakage and structure re-arrangement of the oversized rock blocks inside S-RM, which have a huge influence on the mechanical characteristics of the samples.

Keywords

soil-rock mixture (S-RM) direct shear test water content shear rate particle breakage 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Xu W J, Yue Z Q, Hu R L. Study on the mesostructure and mesomechanical characteristics of the soil-rock mixture using digital image processing based finite element method. Int J Rock Mech Min Sci, 2008, 45: 749–762CrossRefGoogle Scholar
  2. 2.
    Medley E W. The engineering characterization of melanges and similar block-in-matrix rocks (bimrocks). Doctoral Dissertation. Berkeley: University of California, 1994Google Scholar
  3. 3.
    Medley E W. Orderly characterization of chaotic Franciscan Melanges. Eng Geol, 2001, 4: 20–32Google Scholar
  4. 4.
    Casagli N, Ermini L, Rosati G. Determining grain size distribution of the material composing landslide dams in the Northern Apennines: Sampling and processing methods. Eng Geol, 2003, 69: 83–97CrossRefGoogle Scholar
  5. 5.
    Xu W J, Hu R L, Tan R J. Some geomechanical properties of soil-rock mixtures in the Hutiao Gorge area, China. Géotechnique, 2007, 57: 255–264CrossRefGoogle Scholar
  6. 6.
    Buffington J M, Dietrich W E, Kirchner J W. Friction angle measurements on a naturally formed gravel streambed: Implications for critical boundary shear stress. Water Resour Res, 1992, 28: 411–425CrossRefGoogle Scholar
  7. 7.
    Vallejo L E, Mawby R. Porosity influence on the shear strength of granular material-clay mixtures. Eng Geol, 2000, 58: 125–136CrossRefGoogle Scholar
  8. 8.
    Hamidi A, Alizadeh M, Soleimani S. Effect of particle crushing on shear strength and dilation characteristics of sand-gravel mixtures. Int J Civil Eng, 2009, 7: 61–72Google Scholar
  9. 9.
    Hampton D. Effect of rate of strain on the strength of remolded soil. JTRP Technical Reports. 1958Google Scholar
  10. 10.
    Farrag K. Effect of moisture content on the interaction properties of geosynthetics. In: Geosynthetics’95 Conference. Nashville, 1995. 1031–1041Google Scholar
  11. 11.
    Gregory G H. Mechanism of shallow slope failures in clay. In: ASCE Texas Section Fall Meeting, Geotechnical section. Dallas, 1998Google Scholar
  12. 12.
    Marsal R J. Mechanical Properties of Rockfill. 1973. Hoboken: John Wiley & SonsGoogle Scholar

Copyright information

© Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • HouZhen Wei
    • 1
  • WenJie Xu
    • 2
  • ChangFu Wei
    • 1
  • QingShan Meng
    • 1
  1. 1.State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhanChina
  2. 2.State Key Laboratory of Hydroscience and Hydraulic Engineering, Department of Hydraulic EngineeringTsinghua UniversityBeijingChina

Personalised recommendations