scholarly journals Physical and Mechanical Performance of Frozen Rocks and Soil in Different Regions

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Junhao Chen ◽  
Lexiao Wang ◽  
Zhaoming Yao
Keyword(s):  
Mechanical Performance ◽  
Failure Strain ◽  
High Strength ◽  
Cohesive Soil ◽  
High Water ◽  
Curing Temperature ◽  
High Water Content ◽  
Jurassic Rocks ◽  
Frozen Wall ◽  
Rock And Soil

The artificial freezing method is extensively used in the reinforcement of engineering strata in various regions for shaft excavation and subway connection channels. In this study, representative rock and soil strata from different regions were subjected to low-temperature physical and mechanical performance tests. The results show that, compared with Cretaceous and Jurassic rock and soil strata, deep topsoil and shallow coastal topsoil have high water content, low thermal conductivities, high frost heave rates, and high freezing temperatures. In addition, the results show that, as the curing temperature decreases, the uniaxial compressive strengths and elastic moduli of deep topsoil and shallow coastal topsoil increase almost linearly. The strength of the sandy soil strata is the highest, followed by the cohesive soil strata, and the strength of the mucky soil and the calcareous clay is the lowest. The strength of the frozen wall and the waterproof requirements must both be taken into account in the freezing design. Deep Cretaceous and Jurassic rocks can have high strength of more than 5 MPa under normal temperature conditions. An increase in the uniaxial compressive strength and elastic modulus with decreasing curing temperature is mainly manifested within the range from the normal temperature to −10°C. The strength can reach more than 10 MPa at −10°C, and only the strength requirements of the frozen wall need to be considered in the freezing design. At low temperatures, deep topsoil and shallow coastal topsoil are dominated by the form of compression failure. The average failure strain at −10°C is typically greater than 5%. When excavating the strata, it is essential to pay attention to the effect of creep. The failure strain of deep Cretaceous and Jurassic rocks is between 1% and 2%, and the breaking and sudden collapse of surrounding rocks should be prevented.

scholarly journals Muscle-like fatigue-resistant hydrogels by mechanical training

2019 ◽  
Vol 116 (21) ◽  
pp. 10244-10249 ◽  
Author(s):  
Shaoting Lin ◽  
Ji Liu ◽  
Xinyue Liu ◽  
Xuanhe Zhao
Keyword(s):  
Fatigue Resistance ◽  
Skeletal Muscles ◽  
Amorphous Polymer ◽  
High Strength ◽  
High Water ◽  
Polymer Chains ◽  
High Water Content ◽  
High Fatigue ◽  
Synthetic Hydrogels ◽  
Crack Pinning

Skeletal muscles possess the combinational properties of high fatigue resistance (1,000 J/m2), high strength (1 MPa), low Young’s modulus (100 kPa), and high water content (70 to 80 wt %), which have not been achieved in synthetic hydrogels. The muscle-like properties are highly desirable for hydrogels’ nascent applications in load-bearing artificial tissues and soft devices. Here, we propose a strategy of mechanical training to achieve the aligned nanofibrillar architectures of skeletal muscles in synthetic hydrogels, resulting in the combinational muscle-like properties. These properties are obtained through the training-induced alignment of nanofibrils, without additional chemical modifications or additives. In situ confocal microscopy of the hydrogels’ fracturing processes reveals that the fatigue resistance results from the crack pinning by the aligned nanofibrils, which require much higher energy to fracture than the corresponding amorphous polymer chains. This strategy is particularly applicable for 3D-printed microstructures of hydrogels, in which we can achieve isotropically fatigue-resistant, strong yet compliant properties.

scholarly journals A universal method to easily design tough and stretchable hydrogels

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Chisa Norioka ◽  
Yuino Inamoto ◽  
Chika Hajime ◽  
Akifumi Kawamura ◽  
Takashi Miyata
Keyword(s):  
Energy Dissipation ◽  
Polymer Chain ◽  
Mechanical Performance ◽  
Monomer Concentration ◽  
High Water ◽  
High Water Content ◽  
Universal Method ◽  
Covalent Bonds ◽  
Physical And Chemical ◽  
Chain Entanglements

AbstractHydrogels are flexible materials that have high potential for use in various applications due to their unique properties. However, their applications are greatly restricted by the low mechanical performance caused by high water content and inhomogeneous networks. This paper reports a universal strategy for easily preparing hydrogels that are tough and stretchable without any special structures or complicated processes. Our strategy involves tuning the polymerization conditions to form networks with many polymer chain entanglements to achieve energy dissipation. Tough and stretchable hydrogels can be prepared by free radical polymerization with a high monomer concentration and low cross-linker content to optimize the balance between physical and chemical cross-links by entanglements and covalent bonds, respectively. The strategy of using polymer chain entanglements for energy dissipation allows us to overcome the limitation of low mechanical performance, which leads to the wide practical use of hydrogels.

scholarly journals Behavior of CFRP-Confined Sand-Based Material Columns under Axial Compression

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3994
Author(s):  
Guodong Li ◽  
Honglin Liu ◽  
Wentao Deng ◽  
Hongzhi Wang ◽  
Haitian Yan
Keyword(s):  
Mechanical Response ◽  
Mechanical Performance ◽  
High Strength ◽  
Experimental Tests ◽  
High Water ◽  
Underground Mines ◽  
Uniaxial Compression Test ◽  
The Novel ◽  
Axial Deformation ◽  
Cementing Material

This paper presents an innovative pumpable standing support designed for underground mines located in the arid and semi-arid deserts of the Gobi region with a shortage of water resources. The exterior shell of this pumpable standing support is made of carbon fiber-reinforced polymer (CFRP), while the infill material is a sand-based material (SBM). As the novel backfill material, SBM is the combination of high-water cementing material and desert sand. A series of experimental tests were conducted to obtain the mechanical response mechanism of this novel pumpable standing support under uniaxial compression. Test variables investigated in this research covered the water-to-powder ratio of the cementing material, the mixing amount of sand, and the thickness of the CFRP tube. Test results confirmed that the CFRP-confined SBM columns exhibited typical strain hardening behavior with the acceptable axial deformation. It was also demonstrated that using high-strength cementing material, a thicker CFRP tube, and a high mixing amount of sand effectively increased the bearing capacity of the CFRP-confined SBM column. Except for the exemplary structural behavior, the consumption of high-water cementing materials of the novel pumpable standing support is smaller than that of its counterparts made of pure cementing material, when specimens with the same mechanical performance are compared.

Influence of Water Content on the Strength of Silt Soil in Yellow River Alluvial Plain

2012 ◽  
Vol 256-259 ◽  
pp. 481-487
Author(s):  
Xiao Ming Yi ◽  
Song Gen Wang ◽  
Zhen Qing Liu ◽  
Gang Xu
Keyword(s):  
Elastic Modulus ◽  
Water Content ◽  
Yellow River ◽  
Friction Angle ◽  
Cohesive Soil ◽  
High Water ◽  
Alluvial Plain ◽  
High Water Content ◽  
Optimum Water Content ◽  
Influence Of Water

Hydrophilic characteristic of silt soil in Yellow River alluvial plain was studied in order to reveal the water content changes of silt. Then strength tests were used to research how engineering parameters such as elastic modulus, cohesion and friction angle change at different water content. The results show that high permeability coefficient and strong capillary are main factors to increase the water content, and the influence of capillary rising is greater than that of rainfall infiltration. The strength characteristic of silt soil is similar to the character of non-cohesive soil in low water content and that of clay in high water content. If the water content is greater than optimum water content, the elastic modulus and cohesion of silt shall decay obviously. Friction angle decreases dramatically as well, when the soil is saturated.

Features of spring feeding of sterlet of the middle course of the Northern Dvina river

2020 ◽  
pp. 8-17
Author(s):  
A. Bykov ◽  
D. Palatov ◽  
I. Studenov ◽  
D. Chupov
Keyword(s):  
Benthic Communities ◽  
High Water ◽  
Food Composition ◽  
Fish Growth ◽  
High Water Content ◽  
Feeding Intensity ◽  
Biting Midges ◽  
Size Groups ◽  
Main Components ◽  
A Minor

The article provides information about the features of spring feeding of sterlet in the spawning grounds of the middle course of the Northern Dvina river in may 2019. The main and secondary groups of forage objects in the diet of this species of sturgeon are characterized. The article considers the variability of the sterlet food composition with an increase in the size of fish from 30 to 60 cm. In the process of fish growth in the diet of the Severodvinsk sterlet, the main components in terms of occurrence and mass in all size groups are the larvae of Brooks and chironomids. A minor occurrence was the larvae of midges, biting midges, stoneflies, mayflies and small clams. To random and seasonal food are the larvae of water bugs, butterflies, flies, beetles and eggs of other fish. The feeding intensity of the smaller sterlet (30–40 cm) was significantly higher than that of the fish in the size groups 40–50 and 50–60 cm. Fundamental changes in the diet of the Severodvinsk sterlet for the main food objects for more than sixty years of observations have not been established. During periods of high water content of the Northern Dvina due to seasonal changes in the structure of benthic communities, the value of Brooks in the diet of sterlet increases and the proportion of chironomids decreases.

Hydrogels as Antibacterial Biomaterials

2018 ◽  
Vol 24 (8) ◽  
pp. 843-854 ◽  
Author(s):  
Weiguo Xu ◽  
Shujun Dong ◽  
Yuping Han ◽  
Shuqiang Li ◽  
Yang Liu
Keyword(s):  
Mechanical Properties ◽  
Drug Delivery ◽  
Tissue Engineering ◽  
Water Content ◽  
Oxygen Permeability ◽  
Structural Diversity ◽  
High Water ◽  
Clinical Applications ◽  
High Water Content ◽  
Biomedical Field

Hydrogels, as a class of materials for tissue engineering and drug delivery, have high water content and solid-like mechanical properties. Currently, hydrogels with an antibacterial function are a research hotspot in biomedical field. Many advanced antibacterial hydrogels have been developed, each possessing unique qualities, namely high water swellability, high oxygen permeability, improved biocompatibility, ease of loading and releasing drugs and structural diversity. In this article, an overview is provided on the preparation and applications of various antibacterial hydrogels. Furthermore, the prospects in biomedical researches and clinical applications are predicted.

Microwave-Induced Thermoacoustic Imaging for Embedded Explosives Detection in High-Water Content Medium

2019 ◽  
Vol 67 (7) ◽  
pp. 4803-4810 ◽  
Author(s):  
Xiong Wang ◽  
Tao Qin ◽  
Yexian Qin ◽  
Ahmed H. Abdelrahman ◽  
Russell S. Witte ◽  
...  
Keyword(s):  
Water Content ◽  
High Water ◽  
Explosives Detection ◽  
High Water Content ◽  
Thermoacoustic Imaging
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