Water infiltration in loess is one of the most significant processes that can lead to geological disasters on the Loess Plateau in China.However,the spatiotemporal characteristics of infiltration in intact loess,parti...Water infiltration in loess is one of the most significant processes that can lead to geological disasters on the Loess Plateau in China.However,the spatiotemporal characteristics of infiltration in intact loess,particularly the heterogeneity of three-dimensional(3D)seepage and its relationship with soil properties,remain poorly understood.This study conducted field infiltration tests on a 3 m×3 m loess column,instrumented with 48 moisture sensors to monitor 3D seepage and infiltration rates.Both horizontal and vertical infiltration behaviors were analyzed,alongside a detailed characterization of soil physical properties.The results demonstrated that the water infiltration process was significantly heterogeneous in intact loess,with wetting front velocities varying considerably across profiles and depths,despite relatively uniform physical properties.The infiltration process also exhibited pronounced anisotropy,with vertical wetting front velocities at least 10 times higher than those of the horizontal velocities.The in situ tests indicated that the physical properties were not the primary factors influencing infiltration.However,the microfeatures that facilitated the formation of preferential pathways exerted the most significant influence on the water infiltration process in thick unsaturated loess.Additionally,prior infiltration events negatively impacted subsequent infiltration in thick unsaturated loess.These findings enhance the understanding of loess infiltration dynamics,providing insights into unsaturated flow processes and their implications for geological stability in loess regions.展开更多
Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the li...Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the likelihood of landslides.Therefore,investigating the shear behavior and microstructural evolution of loess under climate-induced W-D cycles is crucial to understanding the mechanisms of loess landslides.In this study,Malan loess is analyzed using unsaturated triaxial tests,resistivity tests,scanning electron microscopy,and mercury intrusion porosimetry.The test results show that shear strength decreases with increased W-D cycles,and the degradation effect is more pronounced under lower confining pressure.The variations in conductive pathways indicate that electrical resistivity can effectively reflect the structural damage of loess during W-D cycles,which is associated with increased direct point contacts and spaced pores.Aggregation of clay particles and growth of cracks during the W-D cycles can further destabilize the loess microstructure.As the confining pressure increases,crushed particles rearrange and convert spaced pores into intergranular pores.The number and peak intensity of dominant spaced pores decrease,resulting in a more stable structure.This study clarifies the mechanisms of loess landslides under W-D cycles and provides theoretical support for landslide prevention and control in the CLP.展开更多
This paper uses a complete washing and sieving method and accurately determines the clay mass contents in the loess deposits at the eight regions of Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou ...This paper uses a complete washing and sieving method and accurately determines the clay mass contents in the loess deposits at the eight regions of Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou in China.The method uses nylon cloth sieves with apertures from 0.0008 mm to 0.048 mm and standard steel sieves with apertures from 0.063 mm to 28 mm.It uses a rotary vibration machine to wash and sieve the loess into many clay,silt,sand,and gravel subgroups.The masses of the separated materials construct the complete mass-based particle size distribution(PSD)curves for the tested loesses.The results show that the Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou loesses contain 65.28%,56.73%,56.76%,38.7%,31.78%,30.55%,30.1%,and 26.29%clay in mass.These clay contents are 1.3-14.9 times higher than the clay contents from the past publications for the eight types of loess.On the other hand,the plasticity data in past publications show that loess belongs to the clay type of soil.The clay contents in the publications are underestimated,which is caused by the inseparability of fine soils(or clay and silt mixture)from the existing PSD test methods.Macro-photographs,micro-photographs and SEM photographs present the separated materials of individual clay,silt,sand,and gravel particles.Particle sizes measured from the SEM photographs confirm their particle sizes within their size limits.The clay particles exhibit strong internal cohesion,while the silt,sand,and gravel particles are individual and non-cohesive.Atterberg limits test results further demonstrate the clay particles'high plasticity features and the silt particles'non-plasticity features.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42372307)the Natural Science Basic Research Program of Shaanxi Province(Grant No.2020JC-07)the SCEGC-XJTU Joint Research Center for Future City Construction and Management Innovation,Shaanxi Provincial Land Engineering Construction Group,and Xi’an Jiaotong University(Grant No.20221220).
文摘Water infiltration in loess is one of the most significant processes that can lead to geological disasters on the Loess Plateau in China.However,the spatiotemporal characteristics of infiltration in intact loess,particularly the heterogeneity of three-dimensional(3D)seepage and its relationship with soil properties,remain poorly understood.This study conducted field infiltration tests on a 3 m×3 m loess column,instrumented with 48 moisture sensors to monitor 3D seepage and infiltration rates.Both horizontal and vertical infiltration behaviors were analyzed,alongside a detailed characterization of soil physical properties.The results demonstrated that the water infiltration process was significantly heterogeneous in intact loess,with wetting front velocities varying considerably across profiles and depths,despite relatively uniform physical properties.The infiltration process also exhibited pronounced anisotropy,with vertical wetting front velocities at least 10 times higher than those of the horizontal velocities.The in situ tests indicated that the physical properties were not the primary factors influencing infiltration.However,the microfeatures that facilitated the formation of preferential pathways exerted the most significant influence on the water infiltration process in thick unsaturated loess.Additionally,prior infiltration events negatively impacted subsequent infiltration in thick unsaturated loess.These findings enhance the understanding of loess infiltration dynamics,providing insights into unsaturated flow processes and their implications for geological stability in loess regions.
基金supported by the National Natural Science Foundation of China(Grant Nos.42177138 and 41907239)the Central Guidance Funds for Local Science and Technology Development of China(Grant No.YDZJSX2025D031).
文摘Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the likelihood of landslides.Therefore,investigating the shear behavior and microstructural evolution of loess under climate-induced W-D cycles is crucial to understanding the mechanisms of loess landslides.In this study,Malan loess is analyzed using unsaturated triaxial tests,resistivity tests,scanning electron microscopy,and mercury intrusion porosimetry.The test results show that shear strength decreases with increased W-D cycles,and the degradation effect is more pronounced under lower confining pressure.The variations in conductive pathways indicate that electrical resistivity can effectively reflect the structural damage of loess during W-D cycles,which is associated with increased direct point contacts and spaced pores.Aggregation of clay particles and growth of cracks during the W-D cycles can further destabilize the loess microstructure.As the confining pressure increases,crushed particles rearrange and convert spaced pores into intergranular pores.The number and peak intensity of dominant spaced pores decrease,resulting in a more stable structure.This study clarifies the mechanisms of loess landslides under W-D cycles and provides theoretical support for landslide prevention and control in the CLP.
基金supported by grants from the Research Grant Council of the Hong Kong Special Administra-tive Region,China(Project Nos.HKU 17207518 and R5037-18).
文摘This paper uses a complete washing and sieving method and accurately determines the clay mass contents in the loess deposits at the eight regions of Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou in China.The method uses nylon cloth sieves with apertures from 0.0008 mm to 0.048 mm and standard steel sieves with apertures from 0.063 mm to 28 mm.It uses a rotary vibration machine to wash and sieve the loess into many clay,silt,sand,and gravel subgroups.The masses of the separated materials construct the complete mass-based particle size distribution(PSD)curves for the tested loesses.The results show that the Xianyang,Ili,Xi'an,Yan'an,Lvliang,Linfen,Xining,and Lanzhou loesses contain 65.28%,56.73%,56.76%,38.7%,31.78%,30.55%,30.1%,and 26.29%clay in mass.These clay contents are 1.3-14.9 times higher than the clay contents from the past publications for the eight types of loess.On the other hand,the plasticity data in past publications show that loess belongs to the clay type of soil.The clay contents in the publications are underestimated,which is caused by the inseparability of fine soils(or clay and silt mixture)from the existing PSD test methods.Macro-photographs,micro-photographs and SEM photographs present the separated materials of individual clay,silt,sand,and gravel particles.Particle sizes measured from the SEM photographs confirm their particle sizes within their size limits.The clay particles exhibit strong internal cohesion,while the silt,sand,and gravel particles are individual and non-cohesive.Atterberg limits test results further demonstrate the clay particles'high plasticity features and the silt particles'non-plasticity features.
