WEBNov 12, 2020 · Stressstrain curves of coal from unloading tests under different confining pressures As shown in Fig. 5, the recovery of deformation and permeability occurs in the coal sample with the unloading ...
WhatsApp: +86 18203695377
WEBApr 1, 2017 · In underground operations, the coal cutter cut the coal seam, and large coal blocks were cut off from the coal wall. Then, the coal blocks were transported to the laboratory and processed into cylindrical specimens with diameters of 50 mm and lengths of 100 mm in accordance with the ISRM standard (Fairhurst and Hudson, 1999).The .
WhatsApp: +86 18203695377
WEBDec 3, 2021 · As a result, the crack of saturated coal samples cannot keep stationary in the initial stage of loading and unloading and it slips throughout the loading and unloading process. A large number of macrotensile cracks appeared in the failed coal samples with pore water, as the pore pressure provides tensile force to the cracks and promotes the ...
WhatsApp: +86 18203695377
WEBFeb 15, 2014 · By using RMT150B rock mechanics test equipmentthe acoustic emission(AE)tests of coal specimen under conventional triaxial and triaxial cyclic loading and unloading were carried outand AE characteristics of coal specimens under different loading situations was test results show that the AE mutation point in .
WhatsApp: +86 18203695377
WEBDec 13, 2021 · In the deep mining process of coal seams, the mechanical environment of the coal body is complex and in the state of cyclic loading and unloading. The change in the stress state leads to the change in the pore characteristics and the permeability. To investigate the effects of cyclic loading and unloading on the pore characteristics and .
WhatsApp: +86 18203695377
WEBMay 14, 2024 · This study investigates the stability of an artificial dam used in an underground reservoir in a coal mine under periodic weighting imposed by overlying rock strata. For this purpose, cyclic loading and unloading tests with different stress amplitudes were designed. Differences in the mechanical performance of the artificial dam with and .
WhatsApp: +86 18203695377
WEBJan 9, 2017 · various loading conditions, an ultrasonic test system f or the deformation and fracture of coal rock was used and a cyclic loading and unloading pattern is adopted.
WhatsApp: +86 18203695377
WEBDec 20, 2021 · In the true triaxial cyclic mechanical experiment of coal, most of the total work done by the three principal stresses is accumulated in the coal with elastic potential energy (the elastic strain energy will be released in the unloading process of external force, approximately equal to the negative work done by the external force in the ...
WhatsApp: +86 18203695377
WEBJun 1, 2020 · In the loadingunloading tests, the PER value was calculated based on the initial porosity and the relative increment in the volumetric strain during the whole loadingunloading process. A lower ...
WhatsApp: +86 18203695377
WEBFeb 15, 2024 · The overall trend indied a gradual decrease in the fractal dimension of the SPF, suggesting that the SPF within the coal were progressively fractured and permeated as the confining pressure was unloaded, thereby reducing the complexity of the SPF within the coal. (3) The complete process of unloading the confining pressure was simulated .
WhatsApp: +86 18203695377
WEBUnloading and loading freight happens so often that workers and management can become complacent to the inherent dangers that exist in the process. Unloading and loading freight is almost always under some sort of time constraint. This issue and tighter supply chain windows can exacerbate the problem and create an even more dangerous .
WhatsApp: +86 18203695377
WEBSep 1, 2017 · The mining of coal resources causes the stress on the front and both sides of the working face to be in a complex loading and unloading process, and the gas contained in the coal body migrates ...
WhatsApp: +86 18203695377
WEBJun 1, 2019 · (3) During the loadingunloading process of confining pressure, the permeability of coal containing gas is damaged to a certain extent and this damage can be represented by the maximal damage rate ...
WhatsApp: +86 18203695377
WEBFeb 1, 2024 · In the process of coal seam mining, the coal is disturbed by periodic pressure. This disturbance can be simplified to the loading process under different stress environments [5], [9], [10], [45], and the characteristics of the mining stress path are different under different advancing speeds [46]. Fig. 3 shows the loading path of the .
WhatsApp: +86 18203695377
WEBSep 1, 2017 · From the perspective of mechanics, coal mining is a loading and unloading process. The typical underground loading and unloading features are mainly distributed on the front side and the protective layer. These loions are often in a complex stress environment. The main variation of the force is shown in Fig. 1. It shows that the force ...
WhatsApp: +86 18203695377
WEBThe occurrence of coal–rock dynamic disasters is determined by mininginduced stress loading and unloading. Therefore, it is of great significance to analyze the precursory information of coal deformation and failure during true .
WhatsApp: +86 18203695377
WEBOct 8, 2019 · Discussion on bulk carrier loading and unloading operations and freight safety for the owner's and master's responsibilities and obligations as per charter Party requirements. Master's Thesis, Department of Shipping Technology, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan, 2018.
WhatsApp: +86 18203695377
WEBNov 20, 2022 · The paper represents a test investigation of the mechanical properties and acoustic emission (AE) characteristics of lowstrength coal specimens subjected to cyclic loading and unloading. From the lab tests, the following conclusions can be obtained: (1) The axial strain is very well linear with the loading–unloading cycle number, and the .
WhatsApp: +86 18203695377
WEBMay 27, 2022 · The loading process of CRCS under biaxial compression experienced four ... which has resulted in the rapid unloading of stress in coal and rock. A high unloading speed of 10 m/s of horizontal stress was used to investigate the effects of a much higher unloading speed on the failure and instability of the CRCS according to the speed set ...
WhatsApp: +86 18203695377
WEBApr 18, 2024 · The loading process can be divided into four stages, as seen in Fig. 6 a: (1) initial loading, (2) unloading of σ 3, (3) stress concentration, and (4) the coal burst stages. The initial stress level was applied by multistage loading (the initial stress σ 0 has three grades). When the stress reaches the designed value, it will remain constant ...
WhatsApp: +86 18203695377
WEBOct 10, 2022 · Permeability changes with confining stress loading–unloading: (a) is the PUC; (b) is the aclastic coal; (c) is the mylonitic coal; (d) is the loading–unloading process of confining stress. The increase in confining pressure compressed the coal matrix and internal fissures of the coal cores, and their permeability rapidly and then slowly ...
WhatsApp: +86 18203695377
WEBDec 15, 2023 · A novel permeability model under triaxial pressure loading–unloading was developed. • The influence of effective stress and adsorption/desorption is considered in model. • The model is verified using test results of coal seepage under three conditions. • Triaxial pressure loading–unloading has a significant effect on coal permeability.
WhatsApp: +86 18203695377
WEBMar 20, 2023 · In the process of coal formation, the internal structure is different from the occurrence of primary cracks. As a result, the new crack generation and primary crack development of different samples are affected to different degrees during loading and unloading. Energy characteristics under true triaxial loading and unloading
WhatsApp: +86 18203695377
WEBMar 16, 2023 · Research on the mechanical properties and damage evolution of coal during true triaxial cyclic loading and unloading is of great significance for maintaining the longterm safety and stability of underground engineering structures in coal mines. In this paper, firstly, the deformation, strength and fracturing characteristics of coal during true triaxial .
WhatsApp: +86 18203695377
WEBMay 4, 2020 · Coal mining and production activities lead to static loading and unloading changes of coal stress in front of the working face, and the stress change process has a significant influence on the ...
WhatsApp: +86 18203695377
WEBJun 1, 2015 · Fig. 3 (a) compares the deviatoric stress–strain complete process in coal I under both constant and unloading confining pressures. Fig. 3 (b) plots the complete process of coal II under only unloading confining pressure. Firstly, the deviatoric stress–strain complete process is observed to be almost identical before the loading .
WhatsApp: +86 18203695377
WEBFeb 1, 2021 · The samples collected from Banxi coal mine in Chongqing, Southwest China, have been used to study on damage of coal based on permeability change rate (PCR) and loadunload response ratio (LURR ...
WhatsApp: +86 18203695377
WEBJan 1, 2020 · In the coal mining process, the stress state of the coal seam will change due to unloading caused by coal mininginduced, which may lead to the occurrence of coal and gas outburst disasters.
WhatsApp: +86 18203695377
WEBThe permeability characteristics of a broken coal mass under repeated loading and unloading conditions exert significance on spontaneous combustion of coal in goaf during the mining of coal seam groups. Considering this, by using the seepage test system for broken coalrock mass, seepage tests under cyclic loading and unloading .
WhatsApp: +86 18203695377
WEBAs the coal body has a hysteresis effect during the unloading process, it cannot be unloaded to 0 when unloading, and the minimum unloading level was set for the four kinds of samples; that is, after unloading to 2% σ c, the loading was performed until the sample was destabilized.
WhatsApp: +86 18203695377
WEBResearch on energy and damage evolution patterns of gascontaining coal under constricting pressure unloading conditions is urgently needed in the process of deep underground mining and is crucial for understanding the mechanisms underlying coal and gas composite rockburst occurrences. Prior reaching peak stress, cyclic loading and .
WhatsApp: +86 18203695377
WEBJan 1, 2018 · During the process of deep coal mining, coal seams are generally under the true triaxial stress state (σ1>σ2>σ3), which is influenced by the crustal stress and strong excavation disturbance.
WhatsApp: +86 18203695377
A material supplier from Belgium would like to produce limestone powder for his custome...
India is rich in various mineral resources and it is an important mineral processing market
Copyright © 2023 GMC Co., Ltd. SiteMap
