Determination of the related strength parameters of unsaturated loess with conventional triaxial test

Xing, Xianli; Li, Tonglu; Fu, Yarong

doi:10.1007/s12665-015-4797-5

Cited by 23 publications

(10 citation statements)

References 11 publications

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“…The loess deposits from different sites exhibit very similar shear strength parameters and permeability coefficients, which is probably an effect of the highly consistent grain size distribution. These soils can be classified as silt and are characterised by medium permeability, relatively high internal friction angle values and very low cohesion, which are consistent with the results of loess studies from other regions (Xing et al 2016, Xu et al 2018.…”

Section: Lithology and Geotechnical Characteristics Of Slopessupporting

confidence: 85%

Precipitation Amounts Triggering Landslide Processes in the Western Part of the Nałęczów Plateau (Lublin Upland, Poland)

Demczuk

Zydroń

Szafran³

2022

Quaestiones Geographicae

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This study covers the western part of Poland’s loess Nałęczów Plateau (Kazimierz Dolny, Zbędowice). Mass movements in the Lublin Upland occur during periods of increased precipitation or after a snowy and cold winter. To date, there are no comprehensive studies on active (precipitation, hydrology, vegetation, land use, anthropogenic factors) or passive factors (lithology, slope angle) causing such geohazards in this region. This area’s formations are characterised by high sensitivity to even small changes in moisture content; thus, their geotechnical parameters deteriorate as a result of precipitation or rising groundwater levels. The calculations in this study were chosen to determine the time necessary for ground response to external factors, in addition to determining the impact of these factors on decreases in the factor of safety (FS). Based on calculations in GeoStudio software, the impacts of rainfall totals and duration on slope failure, interpreted as an event where the FS falls below 1.0, were analysed. Accordingly, the threshold rainfall value was determined as the total rainfall at the time of slope failure. The study’s results indicate that loess covers are characterised by average water permeability, relatively high internal friction angles and low cohesion, which, combined with high slope inclination, favour landslide formation even when the slope is only partially saturated. The most unfavourable stability conditions occur at the beginning of spring, indicating that loess stability is significantly affected by snowmelt and precipitation at the beginning of the vegetation season, as well as the occurrence of episodic intense precipitation during the summer.

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Section: Lithology and Geotechnical Characteristics Of Slopessupporting

confidence: 85%

Precipitation Amounts Triggering Landslide Processes in the Western Part of the Nałęczów Plateau (Lublin Upland, Poland)

Demczuk

Zydroń

Szafran³

2022

Quaestiones Geographicae

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“…Loess is extremely sensitive to water and its strength reduces rapidly upon wetting (Xing et al, 2016;Yan et al, 2018). Research has revealed that water sensitivity of loess is manifest by the collapse of the original soil structures and the decrease in the shear strength and stiffness after encountering water (Feda, 1988;Zhou et al, 2014b;Garakani et al, 2015); however, in terms of loess landslides, previous studies (Tu et al, 2009;Jin et al, 2012;Carey et al, 2017;Wang et al, 2020;Pu et al, 2021) usually evaluated stability of a loess slope by using the general theory of unsaturated soil mechanics, such as the Bishop's shear strength formula (Bishop et al, 1961) which considers pore-water and pore-air pressure in soils but does not consider the water sensitivity of mechanical parameters of the loess (Xu L. et al, 2018;Xu Y. et al, 2018).…”

Section: Consideration Of Water Sensitivity Of Loessmentioning

confidence: 99%

Deformation Development Mechanism in a Loess Slope With Seepage Fissures Subjected to Rainfall and Traffic Load

et al. 2021

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Loess landslides induced by rainfall and traffic load are significant hazards during the construction and operation of highways in many loess-covered areas. Studies of the deformation and stability of loess slopes with seepage fissures are limited. In the study, a case study of the Yangpoyao loess slope with seepage fissures in China’s Loess Plateau was conducted to reveal the deformation development mechanism and assess the landslide hazards of such fissured loess slopes. First, the hydraulic-mechanical properties of the Q2 loess were investigated through experiments, and the mathematical expressions of the relationships between various mechanical parameters and water content were fitted, indicating that the mechanical parameters, such as cohesion, angle of internal friction, and deformation modulus, vary in a quasi-linear manner with the water content. Then, a new numerical method was proposed to simulate the mechanical behaviours of the loess considering its water sensitivity and transverse isotropy, where the water sensitivity was considered through the implementation of the mathematical expressions of the hydraulic-mechanical relationships, and the transverse isotropy was considered by the modified constitutive model that combined the logics of transversely elastic model and a ubiquitous-joint model. Finally, the deformation development mechanism of the fissured loess slope under rainfall and traffic load was revealed by using the proposed method. The roles of the rainfall and traffic load in the fissure propagation and deformation development process of the slope were explored, and some stabilisation measures are recommended for the prevention of its failure. The proposed method and findings arising therefrom may provide references for future studies of the stability and landslide hazard assessment of fissured loess slopes.

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“…Irrigation can not only change the groundwater levels but the physical properties of the loess. Many scholars [22][23][24][25][26][27][28][29][30][31] have studied the physical and mechanical properties of loess under irrigation. ey obtained the soil-water characteristic curves and permeability properties of loess under different conditions, as well as the deformation and strength characteristics of loess under different stress paths.…”

Section: Introductionmentioning

confidence: 99%

An Experimental and Numerical Study of Landslides Triggered by Agricultural Irrigation in Northwestern China

Sun

Wang

et al. 2020

Advances in Civil Engineering

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Chinese Loess Plateau (CLP) has become one of the high-incidence areas of landslide disasters in China, especially at the edge of the tablelands where irrigation has been practiced at a large scale since the 1960s. Heifangtai tableland, located in the CLP in Yongjing County, Gansu Province, has been selected as a case, where more than 90 slidings occurred in the past three decades. Field monitoring and laboratory tests were conducted to obtain the soil-water characteristic curve, unsaturated soil shear strength, irrigation water infiltration, and the groundwater level change. Based on these results, a three-dimensional numerical model of the slope was established, and the change of seepage field and slope stability before and after irrigation was investigated using simulations and compared with the observed data. The results show that flood irrigation raised the water table, and the increase of soil moisture in the flooded area was more significant than that in the nonirrigated area. The rising speed of the groundwater level was about 0.25 m/yr, with an amplitude of 0.5 m. Near the slope, the hydraulic gradient of the concave slope was steeper than the convex slope. The shear strength of the loess decreased with increasing soil moisture, and the tensile strength was about 15% of the cohesion. Numerical results showed that after three years of continuous flood irrigation at the back of the slope, the slope stability coefficient decreased by 0.12. After irrigation, the potential slip zone slightly expanded. The reason why landslides often occurred at the back of the gully or the landslide was that the water table was shallower on concave slopes and the soil moisture of the concave slopes was more susceptible to irrigation.

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Determination of the related strength parameters of unsaturated loess with conventional triaxial test

Cited by 23 publications

References 11 publications

Precipitation Amounts Triggering Landslide Processes in the Western Part of the Nałęczów Plateau (Lublin Upland, Poland)

Precipitation Amounts Triggering Landslide Processes in the Western Part of the Nałęczów Plateau (Lublin Upland, Poland)

Deformation Development Mechanism in a Loess Slope With Seepage Fissures Subjected to Rainfall and Traffic Load

An Experimental and Numerical Study of Landslides Triggered by Agricultural Irrigation in Northwestern China

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