西北地质2026，Vol.59Issue(2)：20-31,12.DOI:10.12401/j.nwg.2025138
延安地区典型黄土的物理力学特性及微观结构演化机制
Physical-Mechanical Properties and Microstructural Evolution Mechanisms of Typical Loess in the Yan'an Area
摘要
Abstract
To elucidate the mechanical and seepage properties of typical Yan'an loess at different burial depths and its microstructural evolution patterns,this study systematically investigates four in situ loess layers(L1-L4)from a representative profile in Fuxian County,Yan'an.The objective is to clarify the synergistic mechanism of"structural densification-strength enhancement-permeability reduction,"providing scientific basis for region-al loess stratum stability assessment and impermeability reinforcement design.Systematic investigations were conducted on the four loess layers using direct shear tests,permeability tests,and scanning electron microscopy(SEM)analysis.Pore parameters were quantitatively extracted using Avizo software.Data coupling analysis was performed via Pearson correlation analysis and principal component analysis(PCA).Results indicate:① Shear strength exhibits a layered pattern with burial depth,showing significantly increased cohesion and a slight de-crease in internal friction angle.② The permeability coefficient decreases significantly with depth,exhibiting a"permeable upper layer,dense lower layer"characteristic,plummeting from 17.79×10-5 cm/s in Layer L1 to 7.55×10-5 cm/s in Layer L4.③ At the microstructural level,particle contact patterns change from point contact and weak cementation in shallow layers to surface contact and strong cementation in deeper layers.Pores evolved from large pores(＞35 μm)to medium-small pores(＜30 μm),with shapes tending toward roundness.The orientation shifted from vertical dominance to uniform distribution.④ Pearson analysis indicates a signifi-cant positive correlation between dry density and cohesion,while showing significant negative correlations with total pore area and permeability coefficient.PCA analysis reveals PC1(contribution rate 70.8％)as the primary factor governing"structural densification-strength enhancement,"clearly distinguishing sample distributions between L1(loose,high permeability)and L4(dense,low permeability)layers.Conclusions indicate that the evo-lution of physical and mechanical properties in Yan'an loess is jointly governed by compaction and microstruc-tural remodeling.With increasing burial depth,loess undergoes a"compaction-remodeling-densification"process:particles become more tightly packed,contact modes shift to surface contact,and large pores are com-pressed and destroyed,replaced by medium and small pores.Macro-scale manifestations include increased cohe-sion and significantly reduced permeability.Dry density,cohesion,and pore characteristics collectively govern the overall evolutionary trend of loess from loose and highly permeable to dense and low-permeability.关键词
延安黄土/抗剪强度/渗透特性/微观结构/数据分析Key words
Yan'an loess/shear strength/permeability/microstructure/data analysis分类
天文与地球科学引用本文复制引用
张勇,张法智,谢婉丽,纪成亮,高炫宇,苑康泽,李仁杰,吴至怡,屈鹏鑫,曲晨飞..延安地区典型黄土的物理力学特性及微观结构演化机制[J].西北地质,2026,59(2):20-31,12.基金项目
国家自然科学基金项目(42372320、41972292),陕西省创新能力支撑计划项目(2021TD-54),陕西省重点研发计划项目(2022ZDLSF06-03)联合资助. （42372320、41972292）
