摘要
游离氧化铁的胶结作用及其与土颗粒形成的特殊结构与红黏土力学性能密切相关。为了研究原位状态下游离氧化铁对红黏土力学性质的影响,采用连二亚硫酸钠−柠檬酸钠−重碳酸钠(dithionite-citrate-bicarbonate,简称DCB)溶液对红黏土中的游离氧化铁进行选择性溶解,再结合孔内剪切试验(borehole shear test,简称BST)获得了不同除铁效果下各深度处的红黏土抗剪强度指标。结果表明,游离氧化铁含量FIOC(free iron oxide content)与DCB溶液浸泡时间具有较好的相关性,其特点是除铁速度前期快、后期慢。由BST试验得到红黏土应力−位移关系曲线呈应变硬化变形特征;在同一测试深度下,红黏土抗剪强度随着浸泡时间的递增而降低,浸泡4 d的抗剪强度降幅已达整个试验降低幅度的79.0%左右,再继续浸泡其抗剪强度降低幅度逐渐趋缓;在同一浸泡时间和测试深度下,红黏土的抗剪强度随着法向应力的增大而增大;在同一浸泡时间和法向应力下,红黏土的抗剪强度随着深度的增加而增加;随着浸泡时间的增加,以“包膜”、“桥”或“单粒”的形式赋存的游离氧化铁逐渐被去除,微观上表现为红黏土结构性被破坏,原本致密、紧凑结构出现孔隙、裂隙、疏松的情况,宏观上表现为红黏土力学强度的降低。
The cementation formed by free iron oxide and its special structural connections between particles are closely related to the mechanical properties of laterite.To investigate the effect of free iron oxide on the mechanical properties of laterite in situ,selective dissolution of free iron oxide in laterite was carried out using a Dithionite-Citrate-Bicarbonate solution.The shear strength indexes of laterite at various depths under different iron removal conditions were determined through borehole shear testing(BST).The results indicated a significant correlation between the content of free iron oxide and the duration of DCB solution immersion,with a rapid removal rate in the initial stages followed by a slower rate in the later stages.The stress-strain curve of laterite exhibits strain hardening and deformation in BST testing.At the same depth,the shear strength of laterite decreases as soaking time increases,with a reduction of up to approximately 79.0%within the initial four days of testing.For the same soaking time and depth,the shear strength of laterite increases with increasing normal stress.Similarly,at the same soaking time and normal stress,the shear strength of laterite increases with the increase of depth.As soaking time increases,free iron oxide in the forms of“envelope”,“bridge”or“single particle”is progressively eliminated,leading to damage in the microstructure of laterite.The original dense structure develops pores,cracks,and becomes loose,resulting in a macro-level reduction in the mechanical strength of laterite.
作者
冉宇玲
张文博
柏巍
孔令伟
周丽娜
樊恒辉
RAN Yu-ling;ZHANG Wen-bo;BAI Wei;KONG Ling-wei;ZHOU Li-na;FAN Heng-hui(State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Wuhan,Hubei 430071,China;College of Water Resources and Architectural Engineering,Northwest Agriculture and Forestry University,Yangling,Shaanxi 712100,China;School of Civil Engineering,Wuhan University,Wuhan,Hubei 430072,China;China Nuclear Engineering Consulting Co.,Ltd.,Beijing 100032,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2024年第9期2573-2582,共10页
Rock and Soil Mechanics
基金
国家自然科学基金面上项目(No.41772339,No.41877281)。
关键词
孔内剪切试验
游离氧化铁
红黏土
抗剪强度
borehole shear test(BST)
free iron oxide
lateritic
shear strength
