土木建筑工程

非饱和花岗岩残积土的剪切特性与抗剪强度分析

  • 马勤国 ,
  • 郭皓公 ,
  • 罗晓晓
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  • 1.华南理工大学 亚热带建筑与城市科学全国重点实验室,广东 广州 510640
    2.广州航海学院 智能交通与工程学院,广东 广州 510725
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

收稿日期: 2023-10-10

  网络出版日期: 2024-05-11

基金资助

国家自然科学基金资助项目(52208392);亚热带建筑与城市科学全国重点实验室自主研究课题(2023ZB13);广东省基础与应用基础研究基金资助项目(2021A1515110408)

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)

摘要

对不同含水率的原状和重塑花岗岩残积土开展常规三轴固结不排水试验,对比分析饱和度对原状土和重塑土剪切变形特性的影响规律,并通过测定原状土和重塑土的土水特征曲线,给出基质吸力与抗剪强度指标之间的关系,建立花岗岩残积土非饱和抗剪强度表达式。结果表明:原状和重塑花岗岩残积土的应力-应变曲线的硬化程度随着含水率和围压的增加而上升,原状土的应力-应变曲线在低含水率、低围压条件下表现为软化型,重塑土均表现为硬化型;原状土和重塑土的应力路径随含水率的变化基本相同,随着含水率降低,剪切过程中产生的孔隙水压力逐渐减小,有效应力路径逐渐向总应力路径靠拢;花岗岩残积土土水特征曲线可分为饱和、过渡、残余3个阶段,脱湿过程中原状土的残余吸力大于重塑土,过渡区范围比重塑土大,在高饱和度状态下,原状土和重塑土的含水率随基质吸力的增加变化幅度很小,达到进气值后才随着基质吸力开始明显下降,进入到残余阶段含水率的变化逐渐缓慢;基质吸力对土体内摩擦角的影响很小,黏聚力随着基质吸力的增加不断增大,吸附内摩擦角逐渐减小,基质吸力对土体抗剪强度的贡献逐渐减弱,基质吸力对原状土与重塑土有效黏聚力的影响远大于有效内摩擦角,通过基质吸力与吸力强度之间的回归关系建立的非饱和双曲模型对预测花岗岩残积土的抗剪强度具有很好的适用性。

本文引用格式

马勤国 , 郭皓公 , 罗晓晓 . 非饱和花岗岩残积土的剪切特性与抗剪强度分析[J]. 华南理工大学学报(自然科学版), 2024 , 52(11) : 55 -68 . DOI: 10.12141/j.issn.1000-565X.230470

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.

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