摘要
为了探究水化学作用下膨胀土裂隙面力学特性的变化,选取引江济淮工程菜子湖C003 标段膨胀土,通过特定的制样方式赋予试样预设裂隙面,采用连二亚硫酸钠-柠檬酸钠-碳酸氢钠(DCB)溶液对含裂隙土样进行淋滤,并对淋滤后的试样进行抗剪强度试验研究,探究裂隙面强度变化与淋滤时间的关系,揭示淋滤后膨胀土裂隙面强度变化的微观机理.试验结果表明:DCB溶液沿着预设裂隙面和试样内部淋滤不同天数后,试样形貌特征出现了不同的变化;裂隙面抗剪强度降低速率随着淋滤时间的增加先变快后变慢,在淋滤28d后裂隙面抗剪强度指标下降明显,黏聚力和内摩擦角分别下降51.5%和45.9%;对淋滤后试样表面灰绿土样和直剪试验后剪切面土样进行微细观研究发现,淋滤后灰绿土和剪切面Fe2O3 含量下降明显,且黏土矿物衍射峰强度有一定程度的升高.微观机理分析可知,DCB溶液通过氧化还原作用对土中游离氧化铁进行去除,使试样外观形貌出现较大变化,破坏了土中大的团聚体与颗粒之间的黏结力,从而导致土体力学特性劣化.
Abstract
In order to explore the changes of mechanical characteristics of expansive soil fissure-surface under action of hydro-chemistry,we collected expansive soil in section C003 of Yangtze-to-Huaihe Water Diversion Project.Through a specific sam-ple preparation method,we prepared fissure soil samples with prefabricated fissure-surface that was leached with dithionite-cit-rate-bicarbonate(DCB)solution.The relationship between fissure-surface strength and leaching time was investigated by shearing test,and the microscopic mechanism of the fissure-surface strength was revealed.The results show that after DCB solu-tion leached along the preset fissure-surface for different days,the sample appearances changed differently.With the leaching time increasing,the deteriorating rate of shear strength of fissure-surface decreased fast at first and then slowly.After 28d leac-hing,the cohesion and internal friction angle decreased significantly by 51.5%and 45.9%.The microscopic study on gray-green soil sample after leaching test and sheared surface soil after direct shear test found that the content of Fe2O3 decreased obvi-ously and the intensity of clay mineral diffraction peak increased to a certain extent.It is supposed that DCB solution removed free iron oxide in soil through REDOX action,resulting in a great change in the appearance of the samples and damages to the adhe-sion between large aggregates and particles in soil,so the mechanical properties deteriorated.
基金项目
国家自然科学基金项目(52208329)
中央级公益性科研院所基本科研项目(CKSF2023327/YT)
安徽省引江济淮集团有限公司科技项目(YJJH-ZT-ZX-20191031216)
安徽省引江济淮集团有限公司科技项目(YJJH-ZT-ZX-20230118528)
维普
万方数据