Journal of South China University of Technology(Natural Science) >

2024 , Vol. 52 >Issue 11: 55 - 68

DOI: https://doi.org/10.12141/j.issn.1000-565X.230470

Architecture & Civil Engineering

Analysis on Shear Characteristics and Shear Strength of Unsaturated Granite Residual Soil

  • MA Qinguo ,
  • GUO Haogong ,
  • LUO Xiaoxiao
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  • 1.State Key Laboratory of Subtropical Building and Urban Science，South China University of Technology，Guangzhou 510640，Guangdong，China
    2.School of Intelligent Transportation and Engineering，Guangzhou Maritime University，Guangzhou 510725，Guangdong，China
马勤国（1988—），男，副研究员，主要从事特殊土的工程性质研究。E-mail:maqg@scut.edu.cn

Received date: 2023-10-10

  Online published: 2024-05-11

Supported by

the National Natural Science Foundation of China(52208392);the State Key Laboratory of Subtropical Building and Urban Science(2023ZB13);the Guangdong Basic and Applied Basic Research Foundation(2021A1515110408)

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Abstract

This study carried out triaxial undrained consolidation tests on undisturbed and remolded granite residual soil with different water contents and comparatively analyzed the effect of saturation on shear deformation characteristics of undisturbed and remodeled soils.Firstly, it obtained the relationship between matric suction and shear strength index by measuring the soil-water characteristic curve and established the unsaturated shear strength expression of the granite residual soil. The results show that the degree of strain-hardening of the undisturbed and remodeled soils increases with the increase of water content and confining pressure. The stress-strain curves of the undisturbed soils are softening and the remodeled soils are hardening under low water content and confining pressure. The change pattern of stress path with water content is basically the same in undisturbed soil and remodeled soil. With the decrease of water content, pore water pressure gradually decreases during shearing process, and the effective stress path gradually approaches the total stress path. The soil-water characteristic curve of granite residual soil can be divided into three stages: saturation, transition and residual. During the dehumidification process, the residual suction of undisturbed soil is larger than that of remolded soil, and the transition area is larger than that of remolded soil. In the state of high saturation, the water contents of undisturbed and remodeled soils change little with the increase of matric suction and begin to decrease significantly with matric suction reaching the air-entry value, and the water contents change slowly in the residual stage. The influence of matric suction on the internal friction angle of soil is very small; the cohesion increases with the increase of matric suction; the adsorption internal friction angle decreases gradually; and the contribution of matric suction to the soil shear strength decreases gradually. The influence of matric suction on the effective cohesion of undisturbed soil and remodeled soil is much greater than the effective internal friction angle. The unsaturated hyperbolic model established by the regression relationship between matric suction and suction strength has a good applicability for predicting the unsaturated shear strength of residual granite soil.

Key words： unsaturated granite residual soil; triaxial test; shear strength; soil-water characteristic curve; matric suction

Cite this article

MA Qinguo , GUO Haogong , LUO Xiaoxiao . Analysis on Shear Characteristics and Shear Strength of Unsaturated Granite Residual Soil[J]. Journal of South China University of Technology(Natural Science), 2024 , 52(11) : 55 -68 . DOI: 10.12141/j.issn.1000-565X.230470

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