干湿循环下花岗岩残积土胶结物溶蚀-微结构演化规律与力学行为  

Cement-microstructure Evolution Law and Mechanical Behavior of Granite Residual Soils under Multiple Drying-wetting Cycles

作　　者：康馨 赵士成 刘鹏[1,2,3] KANG Xin;ZHAO Shicheng;LIU Peng(Research Center for Advanced Underground Space Technologies of Hunan University,Changsha 410082,China;Key Laboratory of Building Safety and Energy Efficiency of Ministry of Education(Hunan University),Changsha 410082,China;College of Civil Engineering,Hunan University,Changsha 410082,China)

机构地区：[1]湖南大学地下空间先进技术研究中心,湖南长沙410082 [2]建筑安全与节能教育部重点实验室(湖南大学),湖南长沙410082 [3]湖南大学土木工程学院,湖南长沙410082

出　　处：《湖南大学学报（自然科学版）》2024年第1期159-169,共11页Journal of Hunan University:Natural Sciences

基　　金：国家自然科学基金重点项目(52090082);国家自然科学基金资助项目(51938005,51808207)。

摘　　要：花岗岩残积土中的游离氧化铁粒间胶结作用使其具有高结构性和水敏性.因此,在干湿循环过程中,粒间胶结氧化物被溶蚀,残积土表现出结构崩解重组和复杂的剪切变形特性.为进一步研究干湿循环过程中花岗岩残积土中游离氧化铁溶蚀造成的土体组构变化及其对力学性能弱化的影响,进行一系列的宏微观试验以揭示不同干湿循环次数(0、1、2、4)下残积土的复杂力学特性.研究结果表明,随着干湿循环次数的增加,花岗岩残积土的应力-应变关系将由弱应变硬化型逐渐转变为应变软化状态.微观分析表明游离氧化铁会促使黏土颗粒胶结形成团聚体,随着干湿循环的进行其含量逐渐降低最终趋于稳定.此外,原状残积土粒度分布(PSD)曲线呈现明显的双峰,然后在干湿循环或去除氧化铁后转变为单峰曲线.反复干湿循环会削弱残积土的胶结结构特性,进而导致土体出现明显的软化特征.在剪切过程中,残积土首先表现出剪切收缩特性,随后出现明显的扩张趋势.随着干湿循环次数增加,残积土的有效黏聚力逐渐减小,但有效内摩擦角呈现逐渐增加的趋势.干湿循环过程中花岗岩残积土复杂的力学性能特点是不可逆的体积收缩和胶粒含量的变化以及微裂缝发展之间的耦合效应.Due to the intergranular cementation of free iron oxides(FIOs),granite residual soils(GRS)are highly structural and water-sensitive.Therefore GRS exhibits structural disintegration and reorganization and complex shear deformation properties when subjected to dissolution of the intergranular cemented oxides under repeated drying and wetting(D-W)cycles.In order to further investigate the structural changes caused by the dissolution of the cement FIOs under D-W cycles and its effect on the weakness in mechanical properties of GRS,a series of macroscopic tests were carried out to reveal the complex mechanical behaviors of GRS under different numbers of D-W cycles(0,1,2,4).The experimental results show that the stress-strain relationship of GRS gradually transforms from a weak strain-hardening type into a strain-softened state with the increase in the number of D-W cycles.The microscopic analysis indicates that the FIOs lead to the cementation of soil particles into soil aggregates.However,the content of FIOs shows a decreasing trend but finally tends to be a stable value after the D-W cycles.In addition,the particle size distribution(PSD)curve exhibits an evident bimodal peak,then changes to a single peak curve after the D-W cycles or the removal of FIOs.The repeated D-W cycles weaken the cementation structural properties of the GRS,resulting in the obvious softening characteristics of the soil.During the shear process,GRS first displays shear shrinkage properties,followed by the trend of dilatancy.With an increasing number of D-W cycles,the effective cohesion of the GRS gradually decreases,but the effective internal friction angle shows a trend of increase.The complicated mechanical properties of GRS are characterized by coupling effects among the irreversible volume shrinkage,the variation of collodion content,and the development of microcracks.

关 键 词：花岗岩残积土 干湿循环 结构特性 游离氧化铁 剪切行为 

分 类 号：TU411[建筑科学—岩土工程]