scholarly journals Pore Damage Properties and Permeability Change of Coal Caused by Freeze-Thaw Action of Liquid Nitrogen

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Bo Li ◽  
Lulu Zhang ◽  
Jianping Wei ◽  
Yongjie Ren
Keyword(s):  
Pore Structure ◽  
Liquid Nitrogen ◽  
Cold Shock ◽  
Water Saturation ◽  
Temperature Drop ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Before And After ◽  
Porosity And Permeability ◽  
Coal Rock

A laboratory test was conducted to investigate the effect of the freeze-thaw action of liquid nitrogen on the pore structure and permeability of coal rock. First, coal rock samples with similar sound velocities and permeabilities were selected. These samples were prepared in different water saturation levels and subjected to nuclear magnetic resonance (NMR) test before and after the freeze-thaw action. Furthermore, the freeze-thaw cycle of liquid nitrogen, freezing time, and water saturation of coal rocks were controlled in permeability test. Results showed that the pore diameter, porosity, and permeability of the coal rocks increase after the freeze-thaw action of liquid nitrogen. These characteristics increase further with the increase of water saturation. The fracturing mechanisms of the freeze-thaw action of liquid nitrogen were summarized in two aspects, phase change of pore water and cold shock, and cold shock was mainly discussed. The results indicate that the effect of cold shock is still crucial at low water saturation, but it is limited by the degree of temperature drop. In general, freeze-thaw action of liquid nitrogen can cause damage to pore structure, promote the formation of fracture networks, and consequently improve the permeability of coal rock.

scholarly journals Study on Application Effect of Sand Consolidating Agent for the Slope of Highway Subgrade in Season Frozen Zone

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Dongliang Zhang ◽  
Guangqing Yang ◽  
Xiaodi Niu ◽  
Lu Zhang ◽  
Zhijie Wang
Keyword(s):  
Compressive Strength ◽  
Friction Angle ◽  
Freeze Thaw ◽  
Direct Shear Tests ◽  
Thaw Cycle ◽  
Sand Body ◽  
Before And After ◽  
Freeze Thaw Cycle ◽  
Sandy Slope ◽  
Sand Particles

In deep season frozen areas, the solidified layer is easy to be destroyed due to the influence of freeze-thaw cycles after the surface layer of the sandy slope is solidified by chemical methods. In order to study the application effect of the new sand consolidating agent after solidifying sand body, the mechanism of strength formation was analyzed by scanning electron microscopy (SEM). The freeze-thaw cycle tests were carried out on sand consolidating samples. The direct shear tests and unconfined compressive strength tests were carried out before and after freeze-thaw cycles to analyze the freeze-thaw resistance of sand consolidating samples. The sand consolidation agent was tested on-site, and its strength was tested to observe its effect. The results showed that the adhesive membranes on the surface of sand particles were formed by the sand consolidating agent, which increased the cohesion and strength of sand particles. After freeze-thaw cycle tests, the cohesion, internal friction angle, and compressive strength of the solidified sand gradually decreased with increasing freeze-thaw cycles. The decreasing rate reduced from fast to slow and then tends to be stable. The failure mode of samples changed from brittle failure to plastic failure. The sand consolidating layer can effectively prevent collapse of the sandy slope. Combining with the external-soil spray seeding, the sand consolidation layer is beneficial to the growth of plants.

Low Temperature Performance of Fiberglass Geogrid

2012 ◽  
Vol 443-444 ◽  
pp. 632-636
Author(s):  
Yong Li Xu ◽  
Bai Zhen Ming Zhang ◽  
Le Tao ◽  
Zhen Zhen Xing
Keyword(s):  
Tensile Strength ◽  
Low Temperature ◽  
Water Immersion ◽  
Temperature Drop ◽  
Freeze Thaw ◽  
Temperature Performance ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Shearing Strength ◽  
Low Temperature Performance

The tensile test to the fiberglass geogrid had been carried on, in the normal temperature, the low temperature, the water immersion, the freezing and the freeze-thaw cycle and so on conditions. The results indicated, the fiberglass geogrid had achieved saturated after been immersed 12h, the water absorption was about 20%, the tensile strength reduced approximately 80%; the tensile strength was dropped slightly on the next freezing test and the freeze-thaw cycle test. So it could be stated that the fiberglass geogrid had the good low temperature performance. Then the interlaminar shearing test had been conducted in the different temperature to the composite structure in which the fiberglass geogrid was laid or not. The result showed that the interlaminar shearing strength had weaken about 20% when laid down the fiberglass geogrid, and along with temperature drop, the shearing strength increased gradually. This research provide the reference for used the fiberglass geogrid correctly in the cold region, had great practical value.

scholarly journals Mechanical Properties and Micro Structure of Cement Concrete in Freeze-Thaw Environment

2021 ◽  
Vol 233 ◽  
pp. 01011
Author(s):  
Xin jian Lv ◽  
Lei Yu ◽  
Ming ming Chai
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Pore Structure ◽  
Fresh Water ◽  
Pore Diameter ◽  
Dynamic Elastic Modulus ◽  
Freeze Thaw ◽  
Salty Water ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

In order to find the declay law of mechanical property and the performance difference after salty water and fresh water freeze-thaw cycle, freeze-thaw cycle environments under the salty water and fresh water are simulated. The compressive strength, dynamic elastic modulus and the mass lost are tested. The pore structure parameters are also tested by MIP. Plot the pore diameter distribution curve. The result shows that the compressive strength and dynamic elastic modulus are all decreased. The degree of these two properties decreasing under salty water freeze and thaw recycle is more than the one under fresh water. The parameters of porosity and critical pore diameter become larger. The amount of pores whose diameter is between 100nm and 1000nm increase. The amount of pores whose diameter is under 100nm decrease. The deteriorate degree of pore structure is deeper in salty water than in fresh water.

70 REFREEZING POST-THAWED GOAT SEMEN

2011 ◽  
Vol 23 (1) ◽  
pp. 140
Author(s):  
D. B. Carwell ◽  
B. R. Scott ◽  
G. T. Gentry ◽  
K. R. Bondioli ◽  
R. A. Godke
Keyword(s):  
Liquid Nitrogen ◽  
Sperm Morphology ◽  
Membrane Integrity ◽  
Egg Yolk ◽  
Slow Cool ◽  
Semen Parameters ◽  
Slow Cooling ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Frozen Semen

The ability to successfully refreeze caprine sperm could provide a means of salvaging semen that was mistakenly thawed. The objective of this study was to compare treatment post-thaw semen parameters of twice-frozen caprine semen. Frozen semen from six mature Boer bucks (range in age from 2 to 6 years) was utilised for this experiment. Semen from each buck was extended in an egg yolk-based extender and packaged in 0.5-mL plastic straws before freezing and stored in liquid nitrogen. Three units of frozen semen from each buck was randomly allotted to each of four treatments as follows: (A) thaw and evaluate (control), (B) thaw, then plunge into liquid nitrogen, thaw, and evaluate, (C) thaw, incubate for 3 min at 37°C, slow cool and freeze, thaw, and evaluate, and (D) thaw, incubate for 5 min at 37°C, slow cool and freeze, thaw, and evaluate. Post-thaw parameters included total motility (TM), progressive motility (PM), membrane integrity (MI), and sperm abnormalities (AB). To obtain MI and AB, samples were stained with an eosin-nigrosin stain. A computerized programmable freezer was used to refreeze semen samples in treatment (Trt) C and Trt D. During the slow cooling portion of the protocol, samples were allowed to equilibrate at 38°C, then cooled to 4°C at a rate of 0.30°C min–1, and then held for 5 min. Samples were then cooled to –8°C at a rate of 15°C min–1, seeded, and cooled to –10°C at 15°C min–1, samples were then ramped to –80°C at 30°C min–1 before plunging into liquid nitrogen. Results indicate that post-thaw TM was significantly greater for Trt A (60%) when compared with Trt B, C, and D (0.05, 35, and 39%, respectively). Mean TM were not different between Trt C (35%) and Trt D (39%) but were greater than that for Trt B (0.05%). The PM for post-thaw semen in Trt A was also significantly greater (P < 0.05) when compared with that for Trt B and C (0.05 and 25%); however, no difference was found for mean PM for Trt A (47%) and Trt D (30%), nor were differences found between Trt C (25%) or Trt D (30%). Membrane integrity was higher in Trt A (27%) when compared to Trt B (2.2%). No differences in membrane integrity where found between Trt A, C, and D (27, 13, and 14%, respectively). Additionally, no differences were found between Trt B, C, and D for membrane integrity. Sperm morphology were not different were found with across all treatment groups. These results (i.e. Trt C and D) indicate that semen from mature Boer bucks can undergo a second freeze thaw cycle and still retain motility without dramatically affecting sperm morphology and membrane integrity. These findings indicate that directly plunging recently thawed semen back into liquid nitrogen should not be used for artificial insemination.

Numerical Modeling of the Tissue Freezing-Thaw Cycle During Cutaneous Cryosurgery Using Liquid Nitrogen Spray

2005 ◽  
Author(s):  
Feng Sun ◽  
G.-X. Wang ◽  
K. M. Kelly ◽  
G. Aguilar
Keyword(s):  
Liquid Nitrogen ◽  
Human Skin ◽  
Thermal History ◽  
Tissue Temperature ◽  
Freezing Process ◽  
Target Tissue ◽  
Freeze Thaw ◽  
Membrane Rupture ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

It is common in some cryosurgical procedures to rely on freeze-thaw cycle(s) to destroy undesirable tissues. Most research in cryosurgery focuses on the freezing process and much less attention has been paid to thawing or re-warming. However, as ice melts during thawing, the extracellular solution can become locally hypotonic, driving water into cells, resulting in cell expansion and ultimately, membrane rupture. Therefore, the thermal history of the target tissue during both the freezing and thawing processes is critical for cell viability. To better understand and predict the thermal history during cryosurgery, we developed a two-dimensional numerical model to describe the complete freeze-thaw cycle during liquid nitrogen cutaneous cryosurgery. A stratified anatomical structure of human skin is considered in the model. The numerical simulation applies temperature-dependent thermal and physical properties for human skin tissue and considers the typical thermal boundary conditions for clinical practice. Parametric studies are performed to explore the influence of spray cooling, spray duration and surface heating. Results are discussed concentrating on iceball front propagation, lethal temperature isotherm evolution, tissue temperature variation and cooling rates. These results are expected to provide both quantitative and graphical support to cutaneous cryosurgery and suggest approaches to optimize current cryosurgical protocols.

scholarly journals The Influence of Regional Freeze–Thaw Cycles on Loess Landslides: Analysis of Strength Deterioration of Loess with Changes in Pore Structure

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3047
Author(s):  
Zuyong Li ◽  
Gengshe Yang ◽  
Hui Liu
Keyword(s):  
Pore Structure ◽  
Triaxial Compression ◽  
Strength Loss ◽  
Loess Landslide ◽  
Strength Deterioration ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Loess Landslides ◽  
The Stability

The loess landslide in Gaoling District of Xi’an, Shaanxi in China is closely related to the seasonal freeze–thaw cycle, which is manifested by the destruction of pore structure and strength deterioration of the loess body under freeze–thaw conditions. In order to study the relationship between macro-strength damage and pore structure deterioration of saturated loess under freeze–thaw conditions and its influence on the stability of landslides, this paper explores the effect of freeze–thaw cycles on the strength of saturated undisturbed loess through triaxial compression test, and explores the micro-microstructure changes of saturated undisturbed loess through scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). This is to analyze the evolution of the pore structure and strength loss evolution of saturated loess during the freeze–thaw process, and to describe the freeze–thaw damage of saturated undisturbed loess through the change of porosity and strength deterioration. Then, the internal correlation expression between the porosity change and the strength degradation is established to realize the verification analysis of the test data based on the correlation model. The research results show that: (1) As the number of freeze–thaw cycles increases, the peak strength loss rate gradually increases, and the strength deterioration of saturated loess becomes more and more obvious. (2) The freeze–thaw cycle will lead to the development of pores and cracks in the sample, accompanied by the generation of new cracks, which will cause the deterioration of the pore structure of the sample as a whole. (3) The response of strength damage and porosity deterioration of saturated undisturbed loess is roughly similar under the freeze–thaw cycle. The change in porosity can be measured to better reflect the strength deterioration of saturated loess. Therefore, the change of pore structure of undisturbed loess under freeze–thaw cycle conditions is tested by field sampling and indoor tests to reflect the phenomenon of strength deterioration, thereby analyzing the stability of loess slopes.

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