Investigation of Changes to Triaxial Shear Strength Parameters and Microstructure of Yili Loess with Drying–Wetting Cycles

This research examined the drying–wetting cycles induced changes in undrained triaxial shear strength parameters and microstructural changes of Yili loess. The drying–wetting cycles were selected as 0, 1, 3, 5, 10, 20 and 30. Then, we collected Yili loess samples and performed unconsolidated-undrained (U-U) triaxial shearing tests to ascertain the variation in shear strength parameters with drying–wetting cycles. Additionally, we investigated the microstructural changes of Yili loess samples under drying–wetting cycles simultaneously via nuclear magnetic resonance (NMR) and scanning electron electroscopy (SEM). Finally, we established a grey correlation model between shear strength and microstructural parameters. Under U-U conditions, the prime finding was that the loess’s shear strength parameters changed overall after drying–wetting cycles; in particular, the internal friction angle φ dropped significantly while the cohesion c changed only slightly during cycles. For all the cycles, the first cycle gave the highest change. Soil morphology deterioration was evident at the initial stage of cycles. During the entire drying–wetting cyclic process, pore size distribution showed progressive variance from two-peak to a single-peak pattern, while both porosity and the fractal dimension of pores increased gradually towards stability. Soil particle morphology became slowly simple and reached the equilibrium state after 20 drying–wetting cycles. Under cyclic drying–wetting stress, the shear strength parameter changes were significantly correlated to microstructural modifications. This investigation was related to loess in the westerly region. The findings were expected to provide new insight into establishment of the connection between microstructure and macro stress–strain state of loess. To some extent, it provided a theoretical basis for the prevention and control of loess engineering geological disasters in Yili, Xinjiang and other areas with similar climate and soil types.

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Influence of vetiver root on strength of expansive soil-experimental study

PLoS ONE ◽

10.1371/journal.pone.0244818 ◽

2020 ◽

Vol 15 (12) ◽

pp. e0244818

Author(s):

Gui-yao Wang ◽

Yong-gang Huang ◽

Run-fa Li ◽

Jing-mei Chang ◽

Jin-liang Fu

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Root System ◽

Shear Test ◽

Expansive Soil ◽

Friction Angle ◽

Internal Friction Angle ◽

Strength Parameter ◽

Shear Strength Parameters ◽

Strength Parameters

Grassroots have received more attention than the traditional method as soil reinforcement materials, especially the use of vetiver and other vegetation protection methods to treat expansive soil slope, have been tried and applied. To study the influence of grassroots on the strength properties of expansive soil, the laws of vetiver root growth over time and its vertical distribution of root content(δ) were firstly investigated by the experiment of planting vetiver. Then different δ and depth of planted soil were obtained. Simultaneously different δ and water content(ω) of grafted soil were made. With the direct shear test, the shear strength parameters of root-soil with different δ were analyzed. The shear test on root-soil composites with different δ was carried out to compare the strength characteristics of planted and grafted soil. The results showed that the δ of vetiver decreased with the increase of depth, and the δ of each layer increased with the growth period. The δ of 180d was 70.5% higher than that of 90d. The cohesion(c) of root-soil can be increased by more than 97%, and internal friction angle(φ) can be increased by more than 15.4% after 180 days. The c of 90 d vetiver root system can be increased by more than 18%, and the φ can be increased by more than 1.5%. At each depth, the c and φ of composite soil increases with the increase of δ, and the increment of cohesion (Δc) and the increment of internal friction angle (Δφ) increase with the increment of δ. But the increase in the ω will weaken the shear strength parameters of root-soil. Under the condition of the planted root system and grafted root system, the influence degree of δ on strength parameter of root-soil is different, and the law of strength parameters versus δ of grafted soil of 365d is similar to that of planted soil of 90d. And the root reinforcement of grafted soil is weaker than planted soil. Hence the grafted soil can´t accurately reflect the root-soil interaction of the existing root system.

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Study on the Granular Shear Strength Parameters of Dumping Site

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.256-259.358 ◽

2012 ◽

Vol 256-259 ◽

pp. 358-361

Author(s):

Xiang Yun Kong ◽

Guang Jin Wang ◽

Xiao Chao Zhou

Keyword(s):

Particle Size ◽

Grain Size ◽

Shear Strength ◽

Internal Friction ◽

Friction Angle ◽

Internal Friction Angle ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Dumping Site ◽

Size Grading

Apparent particle size grading is the important characteristic of super-high bench dumping site, and the critical factors with the impact of its stability and disaster prevention are the fragmentation distribution and shear strength parameters of granular. With the copper mine dumping site which had the feature of apparent particle size grading, the thesis carried out the study of on-site particle size investigation and indoor laboratory. The particle-size distribution law with the changing of dumping-site height was analyzed and quantitative relationship between the fragmentation distribution and shear strength parameters of granular was discussed. The research results indicated that coarse-grain contents and maximum grain size were increased significantly according to the decreasing of dumping-site height, which showed that the dumping-site had the feature of apparent particle size grading. The coarse particle content in the grain size composition and internal friction angle φ of shear strength parameters increased with the obvious increment of the distribution value B. The relationship between distribution value B and the internal friction angle φ could be expressed by exponential function curve.

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Improving Shear Strength Parameters of Sandy Soil using Enzyme-Mediated Calcite Precipitation Technique

Civil Engineering Dimension ◽

10.9744/ced.20.2.91-95 ◽

2018 ◽

Vol 20 (2) ◽

pp. 91 ◽

Cited By ~ 4

Author(s):

Heriansyah Putra ◽

Hideaki Yasuhara ◽

Naoki Kinoshita ◽

Erizal . ◽

Tri Sudibyo

Keyword(s):

Shear Strength ◽

Sandy Soil ◽

Friction Angle ◽

Soil Improvement ◽

Soil Mass ◽

Shear Strength Parameters ◽

Calcite Precipitation ◽

Strength Parameters ◽

Direct Shear Tests ◽

Potential Applications

Several methods have been established for their various potential applications as soil improvement technique, and recently the application of grouting technique using biological process have been proposed. This study discussed the applicability of enzyme-mediated calcite precipitation (EMCP) in improving the shear strength parameters of sandy soil. In this study, soil specimens were prepared and treated with the grouting solutions composed of urea, calcium chloride, magnesium sulfate and enzyme of urease. Evolutions in the cohesion and internal friction angle of the improved soil were examined through the direct shear tests. The presence of the precipitated materials, comprising 4.1 percent of the soil mass of the treated sand, generated a cohesion of 53 kPa. However, contrary to the improvement of cohesion, the friction angle is relatively constant. It indicated that the application of the EMCP technique has no significant impact on the friction angle

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UNDRAINED SHEAR STRENGTH PARAMETERS OF SAPROCK FROM A WEATHERING PROFILE OVER PORPHYRITIC BIOTITE GRANITE AT KM 31 OF THE KUALA LUMPUR - KARAK HIGHWAY, PENINSULAR MALAYSIA

Malaysian Journal of Civil Engineering ◽

10.11113/mjce.v33.16400 ◽

2021 ◽

Vol 33 (2) ◽

Author(s):

John Kuna Raj

Keyword(s):

Shear Strength ◽

Friction Angle ◽

Undrained Shear Strength ◽

Triaxial Tests ◽

Regression Analyses ◽

Shear Strength Parameters ◽

Weathering Profile ◽

Strength Parameters ◽

Zone Ii ◽

Undrained Shear

Three broad zones can be differentiated at the weathering profile; an upper, 9.4 m thick, pedological soil (zone I), an intermediate, 31.7 m thick, saprock (zone II) and the bottom bedrock (zone III). The saprock (zone II) comprises gravelly silty sands that distinctly preserve the minerals, textures and structures of the original granite and can be separated into sub-zones II A, II B, II C, and II D, based on differences in preservation of relict structures and content of litho-relicts (core-boulders). To characterize the undrained strength of saprock, samples were collected from sub-zones II A, II B, II C and II D and their physical and soil index properties determined before unconsolidated undrained triaxial tests were carried out on remolded samples. Three to four individual samples from each sub-zone were compressed under confining pressures of 138 kPa, 207 kPa, 276 kPa and/or 345 kPa. Plots of pf = [(σ1 + σ3)/2] versus qf = [(σ1 - σ3)/2] were then used to calculate apparent cohesions of 41.9 kPa, 100.3 kPa, 76.1 kPa and 73.9 kPa, and friction angles of 32.2o, 28.1o, 26.6o and 27.8o, for the samples from sub-zones II A, II B, II C, and II D, respectively. Regression analyses show apparent cohesions to decrease with increasing clay contents, and degrees of saturation; features indicating the influence of negative pore water (or suction) pressures. Regression analyses also show apparent friction angle to increase with increasing sand contents; a feature attributed to greater inter-locking and resistance to displacement of these particles. It is concluded that the undrained shear strength parameters of saprock are characterized by an average apparent cohesion of 54.6 kPa, and friction angle of 30.5o; the parameters influenced by the degree of saturation as well as clay and sand contents.

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The Influence of Compaction and Water Conditions on Shear Strength and Friction Resistance between Geotextiles and Ash-Slag Mixture

Energies ◽

10.3390/en13051086 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1086

Author(s):

Andrzej Gruchot ◽

Tymoteusz Zydroń ◽

Agata Michalska

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Water Saturation ◽

Friction Angle ◽

Interaction Coefficient ◽

Interfacial Friction ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Angle Of Internal Friction ◽

Friction Resistance

The paper presents the results of tests of the shear strength of the ash–slag mixture taken from the landfill located in Kraków (Poland) and the interfacial friction resistance at the contact between the ash–slag mixture and woven or nonwoven geotextiles. The tests were carried out in a direct shear apparatus on samples with and without water saturation. The samples for testing were formed in the apparatus box at the optimum moisture by compacting them to IS = 0.90 and 1.00. The test results reveal that the shear strength parameters of the ash-slag mixture were large. It was stated the significant influence of the compaction, the growth of which has resulted in an increase in the angle of internal friction (from 7% to 9%) and cohesion (from 60% to 97%). Whereas the saturation of the samples reduced the shear strength parameters (from 4% to 6%, of the internal friction angle and 30% to 43% of cohesion). The values of the interfacial friction resistance at the contact between the ash–slag mixture and the geotextiles were large as well, but slightly smaller than the values of the shear strength parameters of the mixture itself. The compaction caused an increase in the angle of interfacial friction (from 1% to 5%) and adhesion (from 31% to 127%). The water-saturation of the samples caused a change in the angle of interfacial friction (from −6% to 3%) and decline in the adhesion (from 22% to 69%). Values of the interaction coefficient were about 0.8–1.0 and they tended to rise with increasing the normal stress. Higher values of this parameter were obtained in tests with water saturation and for non-woven geotextiles.

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Measuring shear strength parameters of polymer-added bentonite-sand mixtures in laboratory experiments

E3S Web of Conferences ◽

10.1051/e3sconf/20199211014 ◽

2019 ◽

Vol 92 ◽

pp. 11014

Author(s):

Hakki O. Ozhan

Keyword(s):

Shear Strength ◽

Tap Water ◽

Friction Angle ◽

Unit Weight ◽

Polymer Content ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Anionic Polymer ◽

Sand Mixture ◽

Polymer Addition

In order to evaluate the shear strength parameters of an anionic polymer-added bentonite-sand mixture that was permeated with tap water, Proctor compaction tests and direct shear tests were performed on the mixture with a bentonite content of 15% by mass. The polymer content in the polymer-bentonite mixture was chosen as 0.5, 1, 2, 5, 10, 15 and 20% by mass, respectively. According to the results, maximum dry unit weight (Vdmax) first decreased as the polymer content was increased to 1% and then, increased. Vdmax of 20% polymer-added mixture and the mixture without polymer addition was measured as 17.55 and 17.28 kN/m3, respectively. Test results indicated that cohesion (c) increased and internal friction angle (ø) decreased due to polymer addition. 2% polymer addition caused an increase of 42 kPa in c but a decrease of 4.2° in ø. As the polymer content increased, maximum shear strength of the mixture (τmax) increased. τmax increased from 171.8 to 197.8 kPa as the polymer content was increased from 0 to 2%. As a result, 2% anionic polymer-added bentonite-sand mixture provided sufficient increase in the shear strength of the mixture.

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Strength Characteristics and Slope Stability of Expansive Soil from Pingdingshan, China

Advances in Materials Science and Engineering ◽

10.1155/2018/3293619 ◽

2018 ◽

Vol 2018 ◽

pp. 1-7 ◽

Cited By ~ 2

Author(s):

Ju-yun Zhai ◽

Xiang-yong Cai

Keyword(s):

Shear Strength ◽

Slope Stability ◽

Expansive Soil ◽

Friction Angle ◽

Natural Soil ◽

Soil Slope ◽

The Finite Element Method ◽

Shear Strength Parameters ◽

Strength Parameters ◽

The Stability

By analyzing the characteristics of expansive soil from Pingdingshan, China, the shear strength parameters at different water contents, dry densities, and dry-wet cycles of expansive soil are obtained. It is found that, at higher soil-water content, the internal friction angle is 0° and the shallow layer of expansive soil slope will collapse and destroy; this has nothing to do with the height of the slope and the size of the slope. The parameters of soil influenced by atmosphere are the ones which have gone through dry-wet cycles, and the parameters of soil without atmospheric influence are the same as those of natural soil. In the analysis of slope stability, the shear strength parameters of soil can be determined by using the finite element method, and the stability coefficient of the expansive soil slope can be calculated.

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Influence of lime stabilization on shear strength parameters of silty clay soil

Glasnik Sumarskog fakulteta ◽

10.2298/gsf1817143s ◽

2018 ◽

pp. 143-156

Author(s):

Marko Spasic ◽

Nikola Zivanovic ◽

Grozdana Gajic

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Clay Soil ◽

Friction Angle ◽

Internal Friction Angle ◽

Silty Clay ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Lime Stabilization ◽

Silty Clay Soil

Lime soil stabilization is a well-known and often used method. One of the methods of landslide stability improvement is changing soil with materials that have better physical and mechanical characteristics. In most of the methods for determining slope stability, the main input data are internal friction angle and cohesion. The main objective of this paper was to find out if the sampled silty clay soil was suitable for lime stabilization, and to get the values of shear strength parameters from soil samples with and without added lime. The results showed that by increasing lime content, internal friction angle rises, while cohesion values decrease, as well as deformations, all the way to 15% of lime by mass. The changes in internal friction angle, cohesion and deformations were most noticeable between 0 and 5% of added lime. Samples that endured the largest pressures were those containing 10% of lime.

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Study on Shear Strength Experiments Base on the Modified Direct Shear Apparatus for Unsaturated Soils

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.438-439.1176 ◽

2013 ◽

Vol 438-439 ◽

pp. 1176-1180 ◽

Cited By ~ 1

Author(s):

Gao Feng Chen ◽

Ying Fa Lv ◽

Zhi Huai Huang ◽

Yan Chang

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Moisture Content ◽

Friction Angle ◽

Soil Samples ◽

Direct Shear ◽

Shear Strength Parameters ◽

Strength Parameters ◽

General Internal ◽

Direct Shear Apparatus

The unconsolidated-undrained fast shear tests of saturated-unsaturated remolded soil samples under different moisture content which is 1.1%, 10.1%, 14.9%, 19.9%, 24.2%, 29.9%, 37.7% respectively, and normal stress which is 50kPa, 100kPa, 200kPa, 300kPa, 400kPa respectively, were studied by the modified SDJ-1-type strain direct shear apparatus and U.S. Lab VIEW data acquisition system. The shear strength parameters of unsaturated soil samples, i.e. general cohesion and general internal friction angle were obtained based on Mohr-Coulomb strength theory. The test results showed that the general cohesion firstly increased and then reduced with the moisture content increasing, and the general internal friction angle increased with the moisture content decreasing. The function between the general shear strength parameters and the moisture content was studied. The concept of general shear strength parameters was proposed in the paper, and would provide a simple and practical method to obtain the strength parameters for engineering practice.

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Experimental Investigation on Shear Strength Parameters of Lime Stabilized Loess

Sustainability ◽

10.3390/su11195397 ◽

2019 ◽

Vol 11 (19) ◽

pp. 5397 ◽

Cited By ~ 1

Author(s):

Liang Jia ◽

Jian Guo ◽

Yanbin Jiang ◽

Yong Fu ◽

Zhidong Zhou ◽

...

Keyword(s):

Shear Strength ◽

Yellow River ◽

Friction Angle ◽

Experimental Results ◽

Triaxial Tests ◽

Curing Time ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Lime Content ◽

Coulomb Failure

Loess is a typical collapsible soil, which is widely distributed in the upper and middle areas around the Yellow River of China. The stabilization of loess with lime provides a significant improvement in the physical and the mechanical characteristics of the loess and is therefore widely used in the pavement base and subgrade. Therefore, a systematic investigation of Mohr-Coulomb failure envelope of lime stabilized loess needs to be conducted. In this pursuit, the present research envisages the investigation of the effects of the lime content, porosity and curing time on the strength parameters (friction angle (φ) and cohesion (c)), using a series of triaxial tests performed on lime stabilized loess specimens. The experimental results revealed that the friction angle (φ) was independent of the lime content, the porosity and the curing time of the specimen for a given lime stabilized loess, while the factors mentioned above had a significant effect on the cohesion (c) of the lime stabilized loess. For a relatively short curing time (7 days), the change in the lime content did not present an obvious effect on the cohesion (c) of the stabilized loess. However, when the curing time (28, 90 and 180 days) was longer, the increase of the lime content significantly enhanced the cohesion of the stabilized loess. When the lime content was constant, the cohesion (c) of the stabilized loess increased linearly with the decrease in the void ratio. A power function equation was proposed to assess the comprehensive influences of the factors like the lime content, porosity and curing time on cohesion (c). Finally, the Mohr-Coulomb failure envelopes were drawn based on the triaxial test for 47 specimens with various curing time and confining pressure, and the shear strength parameters obtained by the proposed equation were also compared with the experimental results.

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