scholarly journals Strength characteristics of frozen coal–rock interface for rock crosscut coal uncovering

2021 ◽  
pp. 014459872110427
Author(s):  
Chuanqu Zhu ◽  
Heyi Ma ◽  
Pengtao Zhao ◽  
Jiwei Yue ◽  
Binbin Wang
Keyword(s):  
Friction Coefficient ◽  
Moisture Content ◽  
Normal Stress ◽  
Residual Strength ◽  
Testing Temperature ◽  
Test Results ◽  
Direct Shear Tests ◽  
Rock Interface ◽  
Coal Rock ◽  
The Relationship

During a freezing method for rock crosscut coal uncovering (RCCU), the mechanical properties of the frozen coal–rock interface have a significant impact on coal-body stability. To investigate characteristic and development mechanism of freezing strength of frozen coal–rock interface, a series of direct shear tests were conducted on frozen coal–rock interface under various testing temperatures, moisture contents in coal and normal stresses. The test results showed that the strength of the frozen coal–rock interface was affected by the moisture content in coal. The larger the moisture content was, the greater strength of the interface was. When the testing temperature was −10°C, the freezing strength increased from 75.46 to 267.42 kPa with the moisture content increasing from 3% to 9%. The ice cementing strength at the interface also increased with testing temperature decreasing. It increased from 6.44 to 73.34 kPa with the testing temperature decreasing from −2°C to −10°C when the moisture content was 5% and the normal stress was 200 kPa. With the increase of normal stress, the residual strength of the frozen coal–rock interface increased. When the moisture content in coal was 9% and the testing temperature was −10°C, the residual strength of the interface increased from 40.68 to 132.28 kPa with the normal stress increasing from 100 to 400 kPa. The testing temperature had no obvious influence on the friction coefficient and the cohesion of residual strength. When the moisture content in coal was 5%, the cohesion of residual strength increased from 23.39 to 98.7 kPa and the friction coefficient of residual strength fluctuated between 0.49 and 0.63 with the testing temperature decreasing from −2°C to −10°C. The relationship between the shear strength and the normal stress followed the Mohr–Coulomb law.

scholarly journals Performance Analysis of Natural γ-Ray Coal Seam Thickness Sensor and Its Application in Automatic Adjustment of Shearer’s Arms

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zengfu Yang ◽  
Zengcai Wang ◽  
Ming Yan
Keyword(s):  
Mathematical Model ◽  
Coal Seam ◽  
Seam Thickness ◽  
Mining Machine ◽  
Practical Advantage ◽  
Rock Interface ◽  
Coal Rock ◽  
Coal Seam Thickness ◽  
The Mathematical Model ◽  
The Relationship

The technology of coal-rock interface recognition is the core of realizing the automatic heightening technology of shearer’s rocker. Only by accurately and quickly identifying the interface of coal and rock can we realize the fully automatic control of shearer. As the only one used in the actual detection of coal mining machine drum cutting coal seam after the thickness of the remaining coal seam detection method, natural γ-ray has a very practical advantage. Based on the relationship between the attenuation of the natural γ-ray passing through the coal seam and the thickness of the coal seam, the mathematical model of the attenuation of the natural γ-ray penetrating coal seam is established. By comparing the attenuation intensity of γ-ray with or without brackets, it is verified that the hydraulic girders will absorb some natural γ-rays. Finally, this paper uses the ground simulation experiment and the field experiment to verify the correctness of the mathematical model and finally develop the natural γ-ray seam thickness sensor. The sensor has the function of indicating the thickness of the coal seam, measuring the natural γ-ray intensity, and storing and processing the data.

Experimental Analysis on Shear Behavior of Sand-Concrete Interface

2012 ◽  
Vol 204-208 ◽  
pp. 893-898
Author(s):  
Chun Feng Zhao ◽  
Bao Lai Yu ◽  
Cheng Zhao
Keyword(s):  
Shear Stress ◽  
Friction Coefficient ◽  
Normal Stress ◽  
Maximum Shear Stress ◽  
Relative Displacement ◽  
Shear Behavior ◽  
Tangential Displacement ◽  
Interface Shear ◽  
Direct Shear Tests ◽  
Concrete Interface

In order to study the shear behavior of sand-concrete structure interface, shear stress and relative displacement curves were obtained through a series of direct shear tests, in the procedure of which the roughness of interfaces was quantified into 3 grades and the stress history can be achieved by loading the sand to an initial normal stress and then unloading to a normal stress to shear. Through analyzing the curves, several conclusions can be obtained as follows: Shear stress increases with the initial normal stress and roughness at the same tangential displacement. The initial shear modulus can be improved in case of the increase of initial normal stress and roughness. The friction coefficient can be obtained by fitting the curve of the maximum shear stress and normal stress corresponded to Mohr-Coulomb Criterion linearly. The friction coefficient of sand-concrete interface increases with roughness as well as its increase range.

Experimental Study on Drying Shrinkage Performance of Solid Concrete Bricks Made from Recycled Coarse Aggregate

2013 ◽  
Vol 753-755 ◽  
pp. 762-770 ◽  
Author(s):  
Xi Xi He ◽  
Tao Zhang
Keyword(s):  
Moisture Content ◽  
Water Absorption ◽  
Coarse Aggregate ◽  
Drying Shrinkage ◽  
Recycled Aggregate ◽  
Test Results ◽  
Replacement Rate ◽  
Recycled Coarse Aggregate ◽  
The Impact ◽  
The Relationship

Solid recycled coarse aggregate concrete bricks were produced by QTY4-40 brick machine with strength grades of MU15-MU30. Recycled aggregate replacement rate was up to 100%. Water absorption and moisture content were tested. Two methods were taken to test the drying shrinkage. The impact of recycled aggregate replacement rate and curing period on the drying shrinkage rate, water absorption, moisture content, density was analyzed, and the relationship between them was presented. The results indicate that recycled aggregate can increase the shrinkage of solid concrete brick. The shrinkage of recycled solid concrete bricks' (fully substitute) is larger than ordinary concrete bricks' by 1.6-2 times. Water reducer is helpful to improve the water retention and decrease the shrinkage of brick. One of the test results of shrinkage got by the methods recommended in relevant specification is smaller.

scholarly journals Shear strength of bonded concrete-granite joints under constant normal stress conditions

2019 ◽  
Vol 92 ◽  
pp. 13014
Author(s):  
Matthieu Briffaut ◽  
Bassel El Merabi ◽  
Frédéric Dufour ◽  
Grégory Coubard
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Roughness Parameter ◽  
Stress Conditions ◽  
Shear Behaviour ◽  
Bonded Joints ◽  
Test Results ◽  
Direct Shear Tests ◽  
Joint Surfaces ◽  
Granite Samples

The shear behaviour of bonded concrete-granite joints under constant normal stress conditions is experimentally investigated in this paper. Concrete was prepared following standard mix used in pre-existing dams in France and poured on granite samples with a natural surface roughness. Before the direct shear tests, the joint surfaces were scanned by a laser profilometer to obtain the 3D morphology features. By analysing the shear test results, no direct correlations were found between the shear strength of bonded joints and classical roughness parameter.

scholarly journals Effect of Moisture Content on Bursting Liability of Sandstone due to Freeze-Thaw Action

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Kesheng Li ◽  
Maotong Li ◽  
Deng Zhang ◽  
Chuanxiao Liu ◽  
Depeng Ma
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Elastic Strain Energy ◽  
Test Results ◽  
Energy Index ◽  
Cold Region ◽  
Freeze Thaw ◽  
Uniaxial Compressive Test ◽  
Rock Mechanical Properties ◽  
The Relationship

Moisture content (MC) and freeze-thaw (F-T) process have an important influence on the mechanical properties of rock and its rockburst tendency in the cold region. In addition, uniaxial compressive strength (UCS) of rock is of great importance in evaluating weathering durability, frost resistance, and bursting liability of rock. In this study, the UCS of rock and bursting liability index of rock including elastic energy index (WET), impact energy index (WCF), elastic strain energy index (ES), and modified values of brittleness index (BIM) were measured by laboratory tests. These tests were implemented in six different MC (0, 0.58, 1.06, 1.82, 2.43, and 2.80%) and 20 F-T cycles. The relationship between rock mechanical properties, bursting liability of rock, and MC after freeze-thaw damage was established, and the control mechanism of moisture content on mechanical properties and rockburst tendency of rocks in cold regions was revealed. Uniaxial compressive test results showed that the UCS of rock decreases significantly with the increase of MC. Under the action of F-T cycles, WET, WCF, and ES decrease with the increase of MC, and BIM of rock increases gradually. This indicates that the rockburst tendency of sandstone decreases with the increase of MC. To calculate WET, WCF, ES, and BIM of sandstone samples, new empirical equations were established and put forward under different MC after 20 F-T cycles.

Seismic Response for a One-Third Scale-Down Vertical Cylindrical Cask Specimen Using Cyclic Loading Testing

2013 ◽  
Vol 479-480 ◽  
pp. 421-426 ◽  
Author(s):  
Wei Ting Lin ◽  
Tseng Chih Fu ◽  
Yuan Chieh Wu ◽  
Chin Cheng Huang
Keyword(s):  
Friction Coefficient ◽  
Cyclic Loading ◽  
Normal Stress ◽  
Seismic Stability ◽  
Test Results ◽  
Frictional Properties ◽  
Dry Storage ◽  
Scale Down ◽  
Loading Tests ◽  
Cyclic Loading Tests

Since the friction coefficient is critical to the seismic stability of a freestanding cask, cyclic loading tests of a 1/3 scale-down pedestal specimen of the INER-dry storage cask system, which will be used in Taiwan, were conducted to acquire the actual friction coefficient at the cask/pad interface as well as the effect of normal stress and sliding rate on it. Test results indicated that the cyclic frequency had few influence on the friction coefficient and the friction coefficient increased with the normal stress increased. The friction coefficient of the vertical cylindrical cask with an add-on shield, vertical cylindrical cask and add-on shield under actual loading condition was about 0.67, 0.60 and 0.73, respectively. Based on the frictional properties at the cask/pad interface obtained from the test results, it was performed to ensure the actual seismic stability of this INER-dry storage cask system under the design base earthquake.

Problematic Internet Use digunakan Ketika Kesepian pada Remaja

2020 ◽  
Vol 14 (1) ◽  
pp. 45-60
Author(s):  
Yashinta Yashinta ◽  
Dwi Hurriyati
Keyword(s):  
Internet Use ◽  
Hypothesis Test ◽  
Problematic Internet Use ◽  
Coefficient Of Determination ◽  
Test Results ◽  
Research Subjects ◽  
Significance Level ◽  
Relationship Of ◽  
The Relationship ◽  
Effective Contribution

This study aims to determine the relationship of loneliness with problematic internet use on boarding students on Silaberanti street in Siantan jaya Opposite Ulu 1 Palembang city. Research subjects numbered 220 people using random sampling methods. Data was collected using a 60 item problematic internet use scale and a 60 item loneliness. Realibility is generated on scale of problematic internet use of 0,955 and loneliness of 0,946.Hypothesis testing uses product moment correlation analysis techniques. Hypothesis test results showed a positive relationshif between loneliness with problematic internet use on boarding students on Silaberanti street in Siantan jaya Opposite Ulu 1 Palembang city r= 0,684 with a significance level of 0,000 (p<0,01). Loneliness in this study made an effective contribution of 46,8% to problematic internet use which can be seen from the coefficient of determination (r²) that is equel to 0,468.

Energetic relationships for crushing of soil clods

2006 ◽  
Vol 2 (1) ◽  
pp. 51-72
Author(s):  
István Patay ◽  
Virág Sándor
Keyword(s):  
Moisture Content ◽  
Specific Energy ◽  
Soil Moisture Content ◽  
Energy Requirement ◽  
Clay Content ◽  
Clay Soils ◽  
Rigid Support ◽  
Soil Plasticity ◽  
Specific Energy Requirement ◽  
The Relationship

Clod crushing is a principal problem with soils of high clay content. Therefore, there is a need for determining the conditions for clod breaking and clod crushing. The objective of the work was to develop a special purpose tool for single clod breaking both by rigid support of the clod and by a single clod supported by soil and to develop a machine for clod crushing. Furthermore, the purpose was to determine the relationship between the specific energy requirement for clod crushing in the function of soil plasticity and the soil moisture content by the means of the developed tool and machine. The main result of the experiments is summarized in a 3D diagram where the specific energy requirement for soil clod crushing is given in the function of the moisture content and the plasticity index for different clay soils.

Sunlight exposure: the effects on the performance of paragliding fabric

2018 ◽  
Vol 69 (05) ◽  
pp. 381-389
Author(s):  
MENGÜÇ GAMZE SÜPÜREN ◽  
TEMEL EMRAH ◽  
BOZDOĞAN FARUK
Keyword(s):  
Mechanical Properties ◽  
Aging Process ◽  
Air Permeability ◽  
Sunlight Exposure ◽  
Test Results ◽  
Coating Materials ◽  
Strength Tests ◽  
Before And After ◽  
The Relationship ◽  
Dark Blue

This study was designed to explore the relationship between sunlight exposure and the mechanical properties of paragliding fabrics which have different colors, densities, yarn counts, and coating materials. This study exposed 5 different colors of paragliding fabrics (red, turquoise, dark blue, orange, and white) to intense sunlight for 150 hours during the summer from 9:00 a.m. to 3:00 p.m. for 5 days a week for 5 weeks. Before and after the UV radiation aging process, the air permeability, tensile strength, tear strength, and bursting strength tests were performed. Test results were also evaluated using statistical methods. According to the results, the fading of the turquoise fabric was found to be the highest among the studied fabrics. It was determined that there is a significant decrease in the mechanical properties of the fabrics after sunlight exposure. After aging, the fabrics become considerably weaker in the case of mechanical properties due to the degradation in both the dyestuff and macromolecular structure of the fiber

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