Measurement of the Shear Strength of an Expansive Soil by Combining a Filter Paper Method and Direct Shear Tests

Bai, Fuqing; Liu, S. H.

doi:10.1520/gtj103342

Cited by 29 publications

(10 citation statements)

References 22 publications

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“…In addition the apparent friction angle slightly reduced from 35.5°under unsaturated condition to 35.1°f or saturated condition. This tendency agrees very well with the results obtained by Bai and Atsumi [12,13]. Finally it can be concluded that the shear strength strongly depend on soil water content, within translate into suction force which contributed to the total shear strength of the soil.…”

Section: Static Shearing Behavioursupporting

confidence: 91%

Mechanical behaviour of unsaturated undisturbed black volcanic ash soil under static and cyclic loading

et al. 2019

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The mechanical behaviour of unsaturated undisturbed black volcanic ash soils was investigated using a constant volume direct shear apparatus. A series of static and cyclic tests were conducted under unsaturated and saturated samples. The cyclic test under two patterns were adopted. First type of pattern, cyclic one-sided shearing was applied. For the second type, two-sided shearing was conducted. For further understanding of the chemical content and microstructure, X-Ray Fluorescence analysis (XRF) and Scanning Electron Microscope (SEM) were evaluated. It was found that, under static shearing, the unsaturated sample exhibits a higher apparent cohesion and friction angle in comparison to the saturated sample. The normalized vertical stress under one-sided cyclic shearing in both overconsolidated and normally consolidated samples rapidly reduced at the beginning of shearing. This might be attributed to increase of the pore water pressure during shearing. Furthermore, there is a significant difference between the normalized shear stress under cyclic one-sided and two-sided shearing. For the two-sided cyclic shearing test, the normalized shear stress value is higher than the one-sided cyclic shearing test. In addition, the normalized shear stress under unsaturated condition is significantly larger. This can be related to the suction forces to the total strength of soils. The main chemical content of the black volcanic ash soil is allophane. Further, the microstructure of the black volcanic ash changes due to shearing. For the overconsolidated sample, particles of soil more severe damage than normally consolidated sample.

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Section: Static Shearing Behavioursupporting

confidence: 91%

Mechanical behaviour of unsaturated undisturbed black volcanic ash soil under static and cyclic loading

et al. 2019

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“…Taking the matric suction as 200 kPa as the demarcation point, the shear strength in the main transition zone increases rapidly with the matric suction comparing with the secondary transition zone. This is similar to the results of Çokça and Tilgen [44], Bai and Liu [45], Pandya et al [13], and Khalili et al [22].…”

Section: Relationship Between Shear Strength and Matricsupporting

confidence: 91%

Study on Water Characteristic Curve and Shear Characteristics of Typical Unsaturated Silty Clay in Shaoxing

Tang

et al. 2021

Geofluids

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In order to probe into one simplified method to predict the shear strength of Shaoxing unsaturated silty clay, the test method combining unsaturated soil consolidation instrument and conventional direct shear instrument is used to study the shear strength, and the method is compared and verified with the results of equal suction direct shear test. The research results show that the soil water characteristic curve fitted by the measured data points and VG model has obvious stage characteristics in the range of 0~38 kPa, 38~910 kPa, and 910~10000 kPa. The shear strength of unsaturated soil measured by consolidation meter combined with conventional direct shear test is in good agreement with that measured by equal suction direct shear test in the range of 0~500 kPa. The results show that the shear strength, total cohesion, and effective internal friction angle of soil increase slightly with the increase of matric suction in the range of 0~38 kPa. When the matric suction increases from 38 kPa to 500 kPa, the shear strength and total cohesion force of the soil have similar stage characteristics with the SWCC, which first increases and then tends to be stable, while the effective internal friction angle changes slightly. Finally, taking the air-entry value as the demarcation point, an improved model of unsaturated shear strength is proposed by analyzing the error value. Compared with the measured value, the absolute value of relative error is basically kept in the range of 5%~10%, which is close to the measured value.

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“…c hi has typically been described with soil suction [ Bishop , ; Fredlund et al ., ; Vanapalli et al ., ]. We empirically estimated c hi based on direct shear tests at different soil moisture levels and normal loads following methods developed by Matsushi and Matsukura [] (Figure a, Texts S1.2 and S2.2, and equation (S4)) and verified by others [ Bai and Liu , ; Zydron and Mietus , ; Zydron et al ., ]. Estimated matric potential using the highest observed moisture values at the most vulnerable depths for slope stability (−342 to −6 kPa) suggest positive pore pressures were unlikely at our sites (Text S1.2) [ Cosby et al ., ].…”

Section: Study Area and Methodsmentioning

confidence: 99%

Vegetation as a driver of temporal variations in slope stability: The impact of hydrological processes

Kim

Fourcaud

Jourdan

et al. 2017

Geophysical Research Letters

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Although vegetation is increasingly used to mitigate landslide risks, how vegetation affects the temporal variability of slope stability is poorly understood, especially in earthquake‐prone regions. We combined 3‐year long soil moisture monitoring, measurements of soil physical properties and plant functional traits, and numerical modeling to compare slope stability under paired land uses with and without trees in tropical, subtropical, and temperate landslide‐ and earthquake‐prone regions. Trees improved stability for 5–12 months per year from drawdown of soil moisture and resulted in less interannual variability in the duration of high‐stability periods compared to slopes without trees. Our meta‐analysis of published data also showed that slopes with woody vegetation were more stable and less sensitive to climate and soil factors than slopes with herbaceous vegetation. However, estimates of earthquake magnitude necessary to destabilize slopes at our sites suggest that large additional stabilization from trees is necessary for meaningful protection against external triggers.

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Measurement of the Shear Strength of an Expansive Soil by Combining a Filter Paper Method and Direct Shear Tests

Cited by 29 publications

References 22 publications

Mechanical behaviour of unsaturated undisturbed black volcanic ash soil under static and cyclic loading

Mechanical behaviour of unsaturated undisturbed black volcanic ash soil under static and cyclic loading

Study on Water Characteristic Curve and Shear Characteristics of Typical Unsaturated Silty Clay in Shaoxing

Vegetation as a driver of temporal variations in slope stability: The impact of hydrological processes

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