scholarly journals Effect of Freeze-Thaw Cycles on the Mechanical Properties of Polyacrylamide- and Lignocellulose-Stabilized Clay in Tibet

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Haiping Shi ◽  
Zhongyao Li ◽  
Wenwei Li ◽  
Shaopeng Wang ◽  
Baotian Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Internal Friction ◽  
Unconfined Compressive Strength ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Test Results ◽  
Freeze Thaw ◽  
Original Strength ◽  
Compressive Tests

Laboratory freezing experiments were conducted to evaluate the effect of polyacrylamide (PAM) and lignocellulose on the mechanical properties and microstructural characteristics of Tibetan clay. Direct shear and unconfined compressive tests and field emission scanning electron microscopy analyses were performed on clay samples with different contents of stabilizers. The test results show that the addition of PAM can improve the unconfined compressive strength and cohesion of Tibetan clay, but an excessive amount of PAM reduces the internal friction angle. After several freeze-thaw cycles, the unconfined compressive strength and cohesion of samples stabilized by PAM decrease significantly, while the internal friction angle increases. Samples stabilized by PAM and lignocellulose have higher internal friction angles, cohesion, and unconfined compressive strength and can retain about 80% of the original strength after 10 freeze-thaw cycles. PAM fills the pores between soil particles and provides adhesion. The addition of lignocellulose can form a network, restrict the expansion of pores caused by freeze-thaw cycles, and improve the integrity of PAM colloids. It is postulated that the addition of a composite stabilizer with a PAM content of 0.4% and a lignocellulose content of 2% may be a technically feasible method to increase the strength of Tibetan clay.

scholarly journals Sensitivity Analysis of Factors Affecting Time-Dependent Slope Stability under Freeze-Thaw Cycles

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Zhiguo Chang ◽  
Qingxiang Cai ◽  
Li Ma ◽  
Liu Han
Keyword(s):  
Internal Friction ◽  
Slope Stability ◽  
Mass Density ◽  
Control Variable ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Open Pit ◽  
Test Results ◽  
Factors Affecting ◽  
Freeze Thaw

With open-pit mines excavated, the slopes will be exposed to the natural environment for a long time. Affected by factors like temperature, seepage, mining, freeze-thaw, etc., slope structural integrity and strength will gradually decline as slope exposure time extends. Besides, the development of defect structure within the rocks is closely correlated with time. In this paper, freeze-thaw cycle tests were conducted on the saturated sandstones collected from a certain open-pit mine. According to the test results, the mass density and longitudinal wave velocity gradually increased with more times of freeze-thaw cycles while mechanical properties such as internal friction angle, cohesion, elastic modulus, and uniaxial compressive strength decreased instead. The constitutive model of saturated rock deterioration was established by taking the volume of phase transition of water in microcracks as a variable. Based on the tests results and theoretical analysis, the sensitivity of the factors affecting slope stability under freeze-thaw damage was studied by Control Variable Method (CVM) and Orthogonal Design Method (ODM). It was determined that the internal friction angle and cohesion had a highly significant effect on the test results, while the mass density had a significant effect. The conclusions may play a certain role in guiding slope construction and protection.

scholarly journals Improvement of the Salinized Soil Properties of Fly Ash by Freeze-Thaw Cycles: An Impact Test Study

2021 ◽  
Vol 13 (5) ◽  
pp. 2908
Author(s):  
Zhuo Cheng ◽  
Gaohang Cui ◽  
Zheng Yang ◽  
Haohang Gang ◽  
Zening Gao ◽  
...  
Keyword(s):  
Shear Strength ◽  
Fly Ash ◽  
Internal Friction ◽  
Unconfined Compressive Strength ◽  
Saline Soil ◽  
Friction Angle ◽  
Ash Content ◽  
Internal Friction Angle ◽  
Freeze Thaw ◽  
Salinized Soil

To explore the mechanism of the microstructural change in salinized soil under freeze-thaw cycles and the strength characteristics of subgrade salinized soil improved by fly ash, an unconfined compressive test, a triaxial shear test, and a scanning electron microscopy test were carried out using salinized soil samples with different fly ash contents along the Suihua to Daqing expressway in China. The results showed that after several freeze-thaw cycles, the unconfined compressive strength, triaxial shear strength, cohesion, and internal friction angle of saline soil showed a decreasing trend. With an increase in the fly ash content, the internal friction angle, cohesion, unconfined compressive strength, and shear strength of the improved saline soil first increased and then decreased. When the fly ash content was 15%, the mechanical indexes, such as cohesion and the internal friction angle, reached the maximum value. Microscopic test results showed that the freeze-thaw cycle will lead to an increase in the proportion of pores and cracks, an increase in the average pore size, and a loosening of the soil structure. The addition of fly ash can fill the soil pores, improve the microstructure of the soil, increase the cohesive force of the soil particles, and improve the overall strength of the soil. Fly ash (15%) can be added to subgrade soil in the process of subgrade construction in the Suihua-Daqing expressway area to improve the shear strength and the resistance to freezing and thawing cycles. These research results are conducive to promoting the comprehensive utilization of fly ash, improving the utilization rate of resources, and promoting sustainable development, thus providing a reference for the design and construction of saline soil roadbed engineering in seasonal frozen areas and the development and construction of saline land belts in seasonal and winter areas.

scholarly journals Influences of Curing Environment on Strength Performances of Shanghai Clayey Soil Reinforced with Palm Fiber

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jili Qu ◽  
Kun Xiong
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Internal Friction ◽  
Shear Modulus ◽  
Unconfined Compressive Strength ◽  
Clayey Soil ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Curing Conditions ◽  
Palm Fiber

Owing to its environment-friendly, economically available, and sustainable property, the palm fiber was attempted to improve the quality of Shanghai clayey soil together with lime. The direct shear tests (DST), ultrasonic pulse velocity tests (UPV), and the unconfined compressive tests (UCT) have been carried out on soils mixed with palm fiber and lime under 3 curing conditions of immersion in water, cyclic wetting-drying, and air curing at a series of contents of additives. The corresponding indexes of shear strength (τ), cohesion (c), internal friction angle (φ), initial shear modulus (G0), and unconfined compressive strength (qu) were obtained and analyzed. Results show that immersed-in-water environment is optimum for the formation of shear strength, initial shear modulus, cohesion, and unconfined compressive strength (UCS), while the air curing condition is the worst for admixture treated soil. Lime can increase G0, but palm fiber can slightly reduce G0. Lime has significant effect on increase of internal friction angle; on the contrary, palm fiber has only limited effect. c/G0 for any type of sample remains almost constant under different curing conditions. It demonstrates that c and G0 possess the comparative development trend under different curing environment.

scholarly journals Microscopic Mechanism of the Macroscopic Mechanical Properties of Cement Modified Subgrade Silty Soil Subjected to Freeze-Thaw Cycles

2020 ◽  
Vol 10 (6) ◽  
pp. 2182
Author(s):  
Hanbing Liu ◽  
Shuang Sun ◽  
Lixia Wang ◽  
Yunlong Zhang ◽  
Jing Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Internal Friction ◽  
Particle Diameter ◽  
Morphological Characteristics ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Average Particle ◽  
Freeze Thaw ◽  
Silty Soil

In order to study the effects of the microstructure parameters of cement modified subgrade silty soil (CMSS) in a frozen area under freeze-thaw (F-T) cycles on the macroscopic mechanical properties, the static triaxial test, scanning electron microscopy (SEM), and grey relation analysis (GRA) were implemented on silty soil modified with 0% and 2% cement at optimum moisture content from the northwest in Jilin Province in China. The results showed that the shear strength, the cohesion of 0% and 2% CMSS, decreased with the increase of F-T cycles, while the internal friction angle was not obviously changed. The shear strength and its parameters of 2% CMSS doubled compared to that of 0% CMSS. The micro-parameters, representing the particle morphological characteristics, particle arrangement, and pore characteristics of CMSS, changed differently under F-T cycles. If the cement was not added, the cohesion and the internal friction angle were most sensitive to the average particle diameter (Dp) and the average particle abundance (C), respectively. When the cement content was 2%, the cohesion was chiefly affected by the particle size fractal dimension (Dps), while the internal friction angle was mainly related to the average pore diameter (Dh). The main principle of cement improvement was to decrease Dh of soil under F-T cycles.

Experimental Study of the Relationship between Matric Suction and Strength of Unsaturated Residual Clay in Xiamen under Different Drying-Wetting Cycle Paths

2013 ◽  
Vol 838-841 ◽  
pp. 680-684
Author(s):  
Dong Xia Chen ◽  
Ming Xin Meng ◽  
Ji Wei Luo
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Internal Friction ◽  
Unconfined Compressive Strength ◽  
Characteristic Curve ◽  
Friction Angle ◽  
Matric Suction ◽  
Internal Friction Angle ◽  
The Relationship ◽  
Cycle Path

To discuss the relationship between matric suction and strength under different drying-wetting cycle paths of residual clay, soil water characteristic curve was determined by the filter paper method. The shear strength, unconfined compressive strength and matric suction were obtained during desorption and adsorption at the drying and wetting cycle. The experimental results show that the matric suction of soil specimens subjected to different drying and wetting cycle paths are different although at the same water content. Contributions of internal friction angle and cohesion to shear strength are different at different matric suction. In the low matric suction stage, matric suction mainly contribute to shear strength by affecting the cohesion, yet in the high matric suction stage by increasing both the internal friction angle and cohesion; in the transition matric suction stage, the contribution of cohesion decreases while the contribution of internal friction angle increases. Furthermore, the unconfined compressive strength of specimens subjected to the drying and wetting cycle path of desorption first and then adsorption is reduced and increase with the opposite path.

Seafloor Polymetallic Sulfides Mechanical Property Test

2014 ◽  
Vol 1015 ◽  
pp. 316-319
Author(s):  
Zhong Hua Huang ◽  
Shao Jun Liu ◽  
Ying Guang Xu ◽  
Wang Hu
Keyword(s):  
Compressive Strength ◽  
Internal Friction ◽  
Uniaxial Compressive Strength ◽  
Compression Strength ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Test Method ◽  
Dry Density ◽  
Average Value

Seafloor polymetallic sulfide specimens were developed according to engineering rock test method standard (GB/T 50266-2013). Seafloor polymetallic sulfide wet density and dry density were tested. Uniaxial compressive strength and triaxial compression strength of seafloor polymetallic sulfide were tested using rock mechanics test system MTS 815. Elasticity modulus and Poisson's ratio of seafloor polymetallic sulfide were calculated based on specimens stress-strain curves. Cohesion and internal friction angle were calculated based on specimens triaxial test Mohr stress circle. Test results show that seafloor polymetallic sulfide dry density average value is 2.6 g/cm3, wet density average value is 2.94 g/cm3. Uniaxial compressive strength and triaxial compression strength of seafloor polymetallic sulfide are unstable. Average value of the uniaxial compressive strength is 10.243MPa. Average value of triaxial compression strength test peak load is 47.166KN. Cohesion is 2.447MPa and internal friction angle is 38.04o.

Experimental Research on the Characteristics of Soil Strength Freeze-Thaw Weakening in Songhua River Songpu Bank

2014 ◽  
Vol 501-504 ◽  
pp. 403-409
Author(s):  
Xue Han ◽  
Zi Long Zhao ◽  
Zi Rui Gao
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Friction Angle ◽  
Soil Strength ◽  
Internal Friction Angle ◽  
Physical Parameters ◽  
Freezing And Thawing ◽  
Songhua River ◽  
Freeze Thaw ◽  
Soil Shear Strength

In order to study characteristics of soil strength freeze-thaw weakening in the Songhua River Songpu bank，basic physical parameters tests and triaxial compression tests were performed on that paragraph bank .The results showed that: after thawing the sample cohesion will drop substantially, the internal friction angle will increase greatly and soil shear strength will increase significantly; the cohesion of sample after repeated freezing and thawing will significantly decline，internal friction angle of soil will greatly increase，the soil shear strength will increase after the first freezing and thawing，with the increase in the number of freeze-thaw cycles, the soil shear strength will significantly decline. The results can provide Songhua slope stability analysis with a scientific basis.

scholarly journals Mechanical properties and damage mode of cemented tailings backfill in an acidic environment

2021 ◽  
Vol 121 (6) ◽  
Author(s):  
Y. Huang ◽  
G. Wang ◽  
Y. Rao ◽  
W. Liu
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Internal Friction ◽  
Sulphuric Acid ◽  
Damage Evolution ◽  
Acid Corrosion ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Acidic Environment ◽  
Corrosion Time

SYNOPSIS The properties and deterioration in strength of cemented tailings backfill (CTB )in the underground acidic environment under oxidizing conditions were studied. X-ray diffraction analysis and scanning electron microscopy of the surface of the CTB was carried out, and the sulphuric acid corrosion mechanism elucidated. The properties tested included compressive strength, elastic modulus, cohesion, internal friction angle, variation in the hydrogen ion concentration, and stress-strain relationship in different corrosion periods. The damage model of the CTB was established considering the effects of parameters such as corrosion time and strain on the damage evolution. It was found that the compressive strength, elastic modulus, cohesion (binder effect), and internal friction angle increased at first and then decreased with exposure time. In the long term, the peak stress decreased with corrosion time while the peak strain increased; elastic modulus, and deformation modulus also decreased. The damage caused by corrosion and by load were related by means of a mathematical model, which revealed the relationships between sulphuric attack, load, and damage to backfill in complex underground environments. During corrosion, the expansion of gypsum and ettringite caused microfractures in the CTB. With increasing corrosion time, micro-cracks developed and proliferated. The mechanism of corrosion damage was found to be the dissolution of hydrogen ions and a sulphate ion reaction that produces an expansive substance, resulting in deterioration of the strength of CTB. Keywords: underground environment, sulphuric acid corrosion, porosity, cemented tailings backfill, damage evolution model.

scholarly journals Degradation of Strength and Stiffness of Sandstones Caused by Wetting-Drying Cycles: The Role of Mineral Composition

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Lu Chen ◽  
Yichao Rui ◽  
Yihan Zhao
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Moisture Content ◽  
Mechanical Parameters ◽  
Test Results ◽  
Strength And Stiffness ◽  
Rock Mechanical Properties ◽  
Mineral Constituents ◽  
Compressive Tests

Rock mechanical parameters are of great importance for the construction and design of rock engineering. Rocks are usually subjected to the deteriorating effect of cyclic wetting-drying because of the change in moisture content. The main objective of this study is to reveal the degradation effects of wetting-drying cycles on strength and modulus on varying rocks. Three kinds of sandstones with different mineral constituents are selected for testing. Artificial treatments of cyclic wetting-drying are conducted on respective specimens of the three sandstones (0, 10, 20, 30, and 40 cycles) to simulate the damage of rocks exposed to natural weathering. Uniaxial compressive tests are carried out on sandstone specimens to obtain their strength and modulus. Test results show that, for the tested sandstones, both of the uniaxial compressive strength (UCS) and modulus are reduced as the cyclic number rises. In the first ten cycles, the losses of UCS and modulus are very significant. Subsequently the changes of UCS and modulus become much more placid against cyclic number. When the cyclic number is the same, the loss percentages of rock mechanical properties of the three sandstones are very different which mainly depends on the contents of expandable and soluble minerals.

Mechanical Properties of Metallic Closed Cellular Materials Containing Polymer Fabricated by Polymer Penetration

2010 ◽  
Vol 654-656 ◽  
pp. 2628-2631 ◽  
Author(s):  
Satoshi Kishimoto ◽  
Toru Shimizu ◽  
Fu Xing Yin ◽  
Kimiyoshi Naito ◽  
Yoshihisa Tanaka
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Compressive Strength ◽  
Internal Friction ◽  
Epoxy Resin ◽  
Metal Foam ◽  
Cellular Materials ◽  
Polyurethane Resin ◽  
The Many ◽  
Compressive Tests

Metallic closed cellular materials containing polymer were fabricated by the penetrating polymer into metal foam. The aluminum and stainless steel foams were selected for the metal foam and epoxy resin and polyurethane resin were selected for the penetrated polymer. The many kinds of mechanical properties of this material were measured. The results of the compressive tests show that these materials have different stress-strain curves among the specimens that containing different materials in the cells. Also, this metallic closed cellular materials containing polymer have higher compressive strength, higher Young’s modules, higher energy absorption and higher internal friction than that of metallic closed cellular material without any polymer.

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