scholarly journals Shear Properties and Mechanism of Freeze-Thaw Interface in Unsaturated Coarse-Grained Soil from Qinghai-Tibet Plateau

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yonglong Qu ◽  
Wankui Ni ◽  
Fujun Niu ◽  
Yanhu Mu ◽  
Jing Luo ◽  
...  
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Coarse Grained ◽  
Tibet Plateau ◽  
Dry Density ◽  
Direct Shear ◽  
Shear Properties ◽  
Freeze Thaw ◽  
Qinghai Tibet Plateau ◽  
Coarse Grained Soil

Freeze-thaw interface in unsaturated coarse-grained soil (CGS) is a weak plane which can cause slope failures in cold regions. This study presents a series of large-scale direct shear tests on freeze-thaw interface in CGS through a temperature control system. The tested soil was taken from a high slope in the Qinghai-Tibet Plateau. It was remolded with three dry densities (1.9, 2.0, and 2.15 g/cm3) and three moisture contents (9.0%, 11.5%, and 14.0%). With testing results, direct shear curves mainly performed as hardening deformation, and they were affected considerably by specimen conditions. The shear strength increased with both the increasing dry density and normal stress, but it was opposite with moisture content changed. The cohesion and internal friction angle increased with the increase in dry density but decreased with the moisture content. The particle movement and water migration of freeze-thaw interface in CGS during the test were significant, and they had close relations with the shear properties of specimens. And, an empirical model was produced to express the effect of pore ice on the shear strength of interface during the shear test. The tests and analysis in this study may provide useful references for CGS slope stability analysis in high cold regions.

scholarly journals Physical and Mechanical Characteristics of Shallow Expansive Soil due to Freeze-Thaw Effect with Water Supplement

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yanlong Li ◽  
Zili Wang ◽  
Yang Luo
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Expansive Soil ◽  
Freezing Temperature ◽  
Strength Reduction ◽  
Dry Density ◽  
Direct Shear ◽  
Soil Columns ◽  
Freeze Thaw ◽  
Shear Strength Reduction

Shear strength of shallow expansive soil varies along with the depth under the freeze-thaw effect. This work investigates shear strength characteristics of shallow expansive soil by simulating the actual freeze boundary conditions of seasonal frozen areas with water supplement. An integrated approach incorporating the freeze-thaw test and direct shear test was adopted. Firstly, unidirectional freezing tests for expansive soil columns under three different freezing temperature gradients were carried out. Secondly, direct shear tests under low vertical stress were performed on the standard samples, which were prepared by using cutting rings cut the thawed expansive soil columns into nine segments along with the depth. Temperature, water content, and dry density at different depths were also investigated after the freeze-thaw process. The test results showed that, after the freeze-thaw process, the shear strength of expansive soil columns showed significant differences along with the depth and highly correlated with water content, specifically the higher water content and the lower shear strength. The minimum shear strength in the expansive soil columns occurred at the soil layer below the frozen and unfrozen zones interface. The expansive soil column’s shear strength changed most under the moderate freezing temperature gradient corresponding to the most considerable shear strength reduction. Moreover, the significant decrease in cohesion was the main reason for the shear strength reduction of expansive soil after the freeze-thaw process. These results indicate significant depth variability in shear strength of expansive soil under the freeze-thaw effect.

scholarly journals A GEOTECHNICAL ASSESSMENT OF USABILITY OF A ROCKSOIL MIXTURE FOR EARTH STRUCTURES

AGROFOR ◽  
2018 ◽  
Vol 2 (3) ◽  
Author(s):  
Eugeniusz ZAWISZA ◽  
Andrzej GRUCHOT
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Solid Particles ◽  
Coarse Grained ◽  
Dry Density ◽  
Maximum Dry Density ◽  
Angle Of Internal Friction ◽  
Natural Moisture Content ◽  
Geotechnical Characteristics ◽  
Geotechnical Assessment

The subject-matter of the work is a mixture of rock and soil from the LafargeDubie mine in Rudawa, southern Poland. The conducted tests aimed at thedetermination of the geotechnical characteristics of this mixture and the evaluationof its suitability for the construction of earth embankments, in particular road ones.The range of the tests comprised determination of parameters characterisingphysical properties, such as granulometric composition, natural moisture content,density of solid particles, optimum moisture content and maximum dry density ofsolid particles, as well as mechanical ones, like shear strength. The obtained resultsshow that the tested mixture is suitable for the construction of road embankments,since as coarse-grained soil, it has a high value of the uniformity coefficient (Cu =1913). Therefore, this is very well graded soil, which provides a good compactionwhen it is built into the embankment. The natural moisture content (on average wn= 9.5%) is close to the optimum one (wopt = 8.5%). The maximum dry density ofsolid particles (ds = 2.16 gcm-3) is much higher than the minimum required (d ≥1.6 gcm-3). The values of the angle of internal friction (on average  = 36) andcohesion (c = 42 kPa) indicate great shear strength, therefore this soil can besubjected to considerable mechanical stresses.

scholarly journals Effect of Sand Percentage on the Compaction Properties and Undrained Shear Strength of Low Plasticity Clay

2021 ◽  
Vol 9 (1) ◽  
pp. 16-20
Author(s):  
Iyad Alkroosh ◽  
Ali Al-Robay ◽  
Prabir Sarker ◽  
Saif Alzabeebee
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Undrained Shear Strength ◽  
Optimum Moisture Content ◽  
Dry Density ◽  
Sand Content ◽  
Compression Tests ◽  
Maximum Dry Density ◽  
Sand Mixture ◽  
Undrained Shear

This paper investigates the influence of sand content on the mechanical behavior of a low plasticity clay that collected from south of Iraq (Sumer town). Samples have been prepared with sand contents of 0%, 10%, 20%, 30%, and 40% of the clay weight. Standard Proctor and unconfined compression tests have been carried out and the optimum moisture content, maximum dry density, and undrained shear strength have been determined. The results show a gradual increasing trend of the maximum dry density with the increase of the sand content up to 30%. The highest dry density reaches 1.90 g/cm3 corresponding to an optimum moisture content of 12%. In addition, this paper shows that the undrained shear strength is inversely proportional to the increase of the percentage of sand. The results of this work provide a useful addition to the literature regarding the behaviour or low plasticity clay-sand mixture.

Mechanical and electrical properties of coarse-grained soil affected by cyclic freeze-thaw in high cold regions

2020 ◽  
Vol 27 (3) ◽  
pp. 853-866
Author(s):  
Yong-long Qu ◽  
Wan-kui Ni ◽  
Fu-jun Niu ◽  
Yan-hu Mu ◽  
Guo-liang Chen ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Coarse Grained ◽  
Cold Regions ◽  
Freeze Thaw ◽  
Mechanical And Electrical Properties ◽  
Coarse Grained Soil

scholarly journals Effects of Cyclic Freeze–Thaw on the Steel Bar Reinforced New-To-Old Concrete Interface

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1251
Author(s):  
Tao Luo ◽  
Chi Zhang ◽  
Xiangtian Xu ◽  
Yanjun Shen ◽  
Hailiang Jia ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Concrete Structures ◽  
Freezing Temperature ◽  
Frost Damage ◽  
Freezing And Thawing ◽  
Shear Properties ◽  
Freeze Thaw ◽  
Steel Bar ◽  
Concrete Interface

Frost damage of concrete has significant effects on the safety and durability of concrete structures in cold regions, and the concrete structures after repair and reinforcement are still threatened by cyclic freezing and thawing. In this study, the new-to-old concrete interface was reinforced by steel bar. The shear strength of the new-to-old concrete interface was tested after the new-to-old combination was subjected to cyclic freeze–thaw. The effects of the diameter of the steel bar, the compressive strength of new concrete, the number of freeze–thaw cycles and the freezing temperatures on the shear properties of new-to-old concrete interface were studied. The results showed that, in a certain range, the shear strength of the interface was proportional to the diameter of the steel bar and the strength of the new concrete. Meanwhile, the shear strength of the reinforced interface decreased with the decreasing of the freezing temperature and the increasing of the number of freeze–thaw cycles.

scholarly journals Determining the Shear Strength Properties of a Soil-geogrid Interface Using a Large-scale Direct Shear Test Apparatus

2020 ◽  
Author(s):  
Jakub Stacho ◽  
Monika Sulovska ◽  
Ivan Slavik
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Large Scale ◽  
Direct Shear Test ◽  
Shear Test ◽  
Strength Properties ◽  
Coarse Grained ◽  
Direct Shear ◽  
Test Apparatus ◽  
Fine Gravel

The paper deals with the laboratory testing of coarse-grained soils that are reinforced using a geogrid. The shear strength properties were determined using a large-scale direct shear test apparatus. The tests were executed on original as well as on reinforced soil, when the geogrid was placed on a sliding surface, which permitted determining the shear strength properties of the soil-geogrid interface. The aim of the tests was to determine the interface shear strength coefficient α, which represents the ratio of the shear strength of the soil-geogrid interface to the unreinforced soil. The tests were executed on 3 samples of coarse-grained materials, i.e., poorly graded sand, poorly graded fine gravel and poorly graded medium gravel. Two types of geogrids were tested, i.e., a woven polyester geogrid and a stiff polypropylene geogrid. The results of the laboratory tests on the medium gravel showed that the reduction coefficient α reached higher values in the case of the stiff polypropylene geogrid. In the cases of the fine gravel and sand, the values of the interface coefficient α were similar to each other. The shear strength of the interface was reduced or was similar to the shear strength of unreinforced soil in a peak shear stress state, but significantly increased with horizontal deformations, especially for the fine gravel and sand. The largest value of the coefficient α was measured in the critical shear stress state. Based on the results of the testing, a correlation which allows for determining the optimal grain size distribution was obtained.

Influences of soil moisture and salt content on loess shear strength in the Xining Basin, northeastern Qinghai-Tibet Plateau

2019 ◽  
Vol 16 (5) ◽  
pp. 1184-1197 ◽  
Author(s):  
Jiang-tao Fu ◽  
Xia-song Hu ◽  
Xi-lai Li ◽  
Dong-mei Yu ◽  
Ya-bin Liu ◽  
...  
Keyword(s):  
Shear Strength ◽  
Soil Moisture ◽  
Salt Content ◽  
Tibet Plateau ◽  
Xining Basin ◽  
Qinghai Tibet Plateau

scholarly journals Experimental Study on Cumulative Plastic Deformation of Coarse-Grained Soil High-Grade Roadbed under Long-Term Vehicle Load

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Zhongming He ◽  
Yaxin Liu ◽  
Haolong Tang ◽  
Yihang Xing ◽  
Hanbing Bian
Keyword(s):  
Moisture Content ◽  
Permanent Deformation ◽  
Correlation Coefficients ◽  
Summation Method ◽  
Coarse Grained ◽  
Test Scheme ◽  
Loading Frequency ◽  
Coarse Grained Soil ◽  
Compaction Degree ◽  
Coarse Soil

According to the change characteristics of the subgrade moisture content and the mechanical calculation of several typical highways, the test scheme of the permanent deformation of coarse soil was formulated. The relationship between the permanent deformation of coarse-grained soil and the stress level, compaction degree, moisture content, and loading frequency was studied by cyclic loading triaxle testing. The results show that the permanent deformation of coarse-grained soil increases with the increase in partial stress and moisture content and decreases with the increase in compaction degree. The experimental data were fitted by the Tseng-Lytton model, and the correlation coefficients were 92%, which indicated that the model could be used to predict the permanent deformation of coarse soil. The relationships between the model coefficient and the moisture content and spring back modulus were obtained by the multiple regression method. Finally, the permanent deformation of the subgrade soil was calculated by using the layered summation method and a typical subgrade pavement structure.

scholarly journals Experimental Study of the Composition and Structure of Granular Media in the Shear Bands Based on the HHC-Granular Model

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Guang-jin Wang ◽  
Xiang-yun Kong ◽  
Chun-he Yang
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Granular Media ◽  
Random Distribution ◽  
Shear Bands ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Coarse Grained ◽  
Composition And Structure ◽  
Coarse Grained Soil

The researchers cannot control the composition and structure of coarse grained soil in the indoor experiment because the granular particles of different size have the characteristics of random distribution and no sorting. Therefore, on the basis of the laboratory tests with the coarse grained soil, the HHC-Granular model, which could simulate the no sorting and random distribution of different size particles in the coarse-grained soil, was developed by use of cellular automata method. Meanwhile, the triaxial numerical simulation experiments of coarse grained soil were finished with the different composition and structure soil, and the variation of shear strength was discussed. The results showed that the internal friction angle was likely to reduce with the increasing of gravel contents in the coarse-grained soil, but the mean internal friction angle significantly increased with the increment of gravel contents. It indicated that the gravel contents of shear bands were the major factor affecting the shear strength.

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