盐风化作用下黄土结构的破坏特征与机理  

Damage characteristics and mechanisms of soil structures under salt weathering

作　　者：段钊[1] 李瑞怡 宋昆 闫旭升 郑立才 贺子光 DUAN Zhao;LI Ruiyi;SONG Kun;YAN Xusheng;ZHENG Licai;HE Ziguang(College of Geology and Environment,Xi’an University of Science and Technology,Xi’an 710054,Shaanxi,China;Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Tongji University,Shanghai 200092,China;Sanying Precision Instruments Co.,Ltd,Tianjin 300399,China;College of Architecture and Civil Engineering,Huanghuai University,Zhumadian 463000,Henan,China)

机构地区：[1]西安科技大学地质与环境学院,陕西西安710054 [2]同济大学岩土及地下工程教育部重点实验室,上海200092 [3]天津三英精密仪器股份有限公司,天津300399 [4]黄淮学院建筑工程学院,河南驻马店463000

出　　处：《干旱区地理》2024年第12期2041-2050,共10页Arid Land Geography

基　　金：国家自然科学基金(42177155,41702298);河南省科技攻关计划项目(232102321016);河南省教育厅高校重点科研项目(23A410003)资助。

摘　　要：探究盐风化作用下(单向脱湿条件)黄土结构的破坏特征和黄土强度的劣化效应,为黄土高原地区的水土保持和灾害防治提供参考依据。选取陕西省府谷县的Q2黄土,对其开展了不同硫酸钠含量下的宏-微观尺度观测和剪切强度测试。结果表明:(1)在宏观尺度上,含盐量的增加会显著加剧试样表观的破坏程度和膨胀位移。1.0%~2.5%含盐量试样均表现出轮廓结垢的破坏特征,从不均匀的表面结皮逐渐过渡到大面积的盐斑和膨胀裂纹,但未观察到0.5%较低含盐量的试样表现出盐胀、盐斑和结皮现象。并且整个盐风化过程经历了萌芽期、生长期和平稳期3个阶段。(2)在微观尺度上,盐风化作用造成黄土中的团聚体和孔隙增多,此外,明显观察到十水合硫酸钠结晶的存在,这是盐风化过程的直接产物。(3)试样经历盐风化后,剪切特征从应变软化型转变为应变硬化型,并且盐风化作用能显著劣化试样的峰值强度,使内聚力明显降低。随着硫酸钠含量的增加,盐风化作用会加剧黄土发生“结晶膨胀”和“干燥聚沉”,并在其表面和内部形成大量膨胀裂纹和孔隙,最终造成黄土结构和强度的显著破坏。This study investigates the damage characteristics of loess structures and the deterioration of loess strength under the influence of salt weathering,with a focus on unidirectional dehumidification conditions.The findings provide valuable references for soil and water conservation,as well as disaster prevention strategies in the Loess Plateau.Q2 loess from Fugu County,Shaanxi Province,China was selected for macro-and micro-scale observations and shear strength tests under varying sodium sulfate contents.The results indicate the following:(1)Macroscopic effects:An increase in salt content significantly impacts the apparent damage degree and expansion displacement of the samples.Samples with salt contents ranging from 1.0% to 2.5% exhibited contour scaling damage characteristics,transitioning from uneven surface crusts to extensive salt spots and expansion cracks.In contrast,samples with a lower salt content of 0.5% did not show salt swelling,salt spots,or crust formation.The salt weathering process progresses through three stages:germination,growth,and stability.(2)Microscopic effects:Salt weathering leads to the formation of agglomerates and expansive pores within loess.Sodium sulfate decahydrate crystals were observed as a direct result of the salt weathering process.(3)Shear characteristics:The shear behavior of the samples transitioned from strain softening to strain hardening after salt weathering,with significant degradation in peak strength and reduced cohesion.As sodium sulfate content increased,salt weathering intensified the effects of“salt crystallization-induced expansion”and“soil drying-induced coagulation”in loess.This process generated numerous expansion cracks and pores both on the surface and within the loess,ultimately causing severe structural and strength deterioration.

关 键 词：黄土 硫酸钠 盐风化 抗剪强度 损伤 

分 类 号：TU444[建筑科学—岩土工程]