scholarly journals Characteristics of Collapse Accumulation Body in Roadway and Numerical Simulation of Rescue Channel Excavation

Author(s):  
Guangbo Chen ◽  
Pengcheng Teng ◽  
Huiqiang Duan ◽  
Guohua Zhang ◽  
Tan Li

Abstract After the coal mine disaster, the collapsed accumulation body blocked the roadway and interrupted the rescue route, which seriously affected the development of rescue. Based on the post-disaster blockage rescue route of the collapsed accumulation body, the morphology and structural characteristics of the accumulation body were analyzed, and the process of excavating the rescue channel in the collapsed accumulation body in the mining roadway was simulated using CDEM software, and the moving mode of accumulation body fragments was discussed. The study found that: the formation of the accumulation body is the process of continuous “self-organization” adjustment of the rock fragments; the accumulation body along the direction of the roadway axis is divided into three areas: pre-sorting accumulation area, post-sorting accumulation area, and non-sorting accumulation area; the particle size of the accumulation body-particle content conforms to the normal distribution; the harder the rock fragments constituting the accumulation body is, the particle size of the fragments is more different; the number of contact points of the fragments of the tightly accumulation body is more than that of the loose accumulation body; the excavation of the rescue channel is accompanied by the random “self-organization” movement of the accumulated body; the settlement and deformation of the accumulated body is actually the continuous collapse of the old arch structure, and the process of continuous formation of a new arch structure; the initial force of the rescue channel excavation is small, then it increases sharply, and finally stabilizes; the fragment adjustment forms are mainly divided into horizontal movement adjustment, vertical movement adjustment, rotation movement adjustment, and multi-directional movement adjustment. The research conclusion has certain guiding significance for the rescue channel excavation under the condition that the collapsed accumulation body blocks the roadway after the coal mine disaster.

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 426
Author(s):  
Behrooz Abbasi ◽  
Xiaoliang Wang ◽  
Judith C. Chow ◽  
John G. Watson ◽  
Bijan Peik ◽  
...  

Respirable coal mine dust (RCMD) exposure is associated with black lung and silicosis diseases in underground miners. Although only RCMD mass and silica concentrations are regulated, it is possible that particle size, surface area, and other chemical constituents also contribute to its adverse health effects. This review summarizes measurement technologies for RCMD mass concentrations, morphology, size distributions, and chemical compositions, with examples from published efforts where these methods have been applied. Some state-of-the-art technologies presented in this paper have not been certified as intrinsically safe, and caution should be exerted for their use in explosive environments. RCMD mass concentrations are most often obtained by filter sampling followed by gravimetric analysis, but recent requirements for real-time monitoring by continuous personal dust monitors (CPDM) enable quicker exposure risk assessments. Emerging low-cost photometers provide an opportunity for a wider deployment of real-time exposure assessment. Particle size distributions can be determined by microscopy, cascade impactors, aerodynamic spectrometers, optical particle counters, and electrical mobility analyzers, each with unique advantages and limitations. Different filter media are required to collect integrated samples over working shifts for comprehensive chemical analysis. Teflon membrane filters are used for mass by gravimetry, elements by energy dispersive X-ray fluorescence, rare-earth elements by inductively coupled plasma-mass spectrometry and mineralogy by X-ray diffraction. Quartz fiber filters are analyzed for organic, elemental, and brown carbon by thermal/optical methods and non-polar organics by thermal desorption-gas chromatography-mass spectrometry. Polycarbonate-membrane filters are analyzed for morphology and elements by scanning electron microscopy (SEM) with energy dispersive X-ray, and quartz content by Fourier-transform infrared spectroscopy and Raman spectroscopy.


Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3876
Author(s):  
Jesús Valdés ◽  
Daniel Reséndiz ◽  
Ángeles Cuán ◽  
Rufino Nava ◽  
Bertha Aguilar ◽  
...  

The effect of microwave radiation on the hydrothermal synthesis of the double perovskite Sr2FeMoO6 has been studied based on a comparison of the particle size and structural characteristics of products from both methods. A temperature, pressure, and pH condition screening was performed, and the most representative results of these are herein presented and discussed. Radiation of microwaves in the hydrothermal synthesis method led to a decrease in crystallite size, which is an effect from the reaction temperature. The particle size ranged from 378 to 318 nm when pH was 4.5 and pressure was kept under 40 bars. According to X-ray diffraction (XRD) results coupled with the size-strain plot method, the product obtained by both synthesis methods (with and without microwave radiation) have similar crystal purity. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques showed that the morphology and the distribution of metal ions are uniform. The Curie temperature obtained by thermogravimetric analysis indicates that, in the presence of microwaves, the value was higher with respect to traditional synthesis from 335 K to 342.5 K. Consequently, microwave radiation enhances the diffusion and nucleation process of ionic precursors during the synthesis, which promotes a uniform heating in the reaction mixture leading to a reduction in the particle size, but keeping good crystallinity of the double perovskite. Precursor phases and the final purity of the Sr2FeMoO6 powder can be controlled via hydrothermal microwave heating on the first stages of the Sol-Gel method.


2005 ◽  
Vol 128 (1) ◽  
pp. 116-127 ◽  
Author(s):  
Stephen Wiedmann ◽  
Bob Sturges

Compliant mechanisms for rigid part mating exist for prismatic geometries. A few instances are known of mechanisms to assemble screw threads. A comprehensive solution to this essentially geometric problem comprises at least three parts: parametric equations for nut and bolt contact in the critical starting phase of assembly, the possible space of motions between these parts during this phase, and the design space of compliant devices which accomplish the desired motions in the presence of friction and positional uncertainty. This work concentrates on the second part in which the threaded pair is modeled numerically, and contact tests are automated through software. Tessellated solid models were used during three-dimensional collision analysis to enumerate the approximate location of the initial contact point. The advent of a second contact point presented a more constrained contact state. Thus, the bolt is rotated about a vector defined by the initial two contact points until a third contact location was found. By analyzing the depth of intersection of the bolt into the nut as well as the vertical movement of the origin of the bolt reference frame, we determined that there are three types of contacts states present: unstable two-point, quasi-stable two-point, stable three point. The space of possible motions is bounded by these end conditions which will differ in detail depending upon the starting orientations. We investigated all potential orientations which obtain from a discretization of the roll, pitch, and yaw uncertainties, each of which has its own set of contact points. From this exhaustive examination, a full contact state history was determined, which lays the foundation for the design space of either compliant mechanisms or intelligent sensor-rich controls.


2017 ◽  
Author(s):  
Indra Riyanto

This paper will discuss about the design of a portable photo voltaic electric generator capable of tracking sunlight in all directions. Such power generator is designed for disaster affected area with power outage, such as during major floods like Jakarta in 2012, or strong earthquake such as Yogyakarta in 2006 and Japan in 2011 (Tohoku) and 2016 (Kumamoto). Such occurence usually results in disruptions of public service, especially power grids. The system consists of a 10 Wp PV solar panels capable in two axes movement, which is 120° horizontal and 360° azimuth movement with ATMega8535 micro controller as the main controller. Two-axis movement is based on two types of sensors, 360° directional movement is based on the HMC5883 compass sensor. This compass sensor panel also be configured to always directs towards the sun so that if the direction of the base plate was changed, it will automatically direct the panel to the direction of the sun. While 120° vertical movement based on three pieces of LDR (Light Dependent Resistor) as sun sensors. The purpose of this system is to maximize the amount of light received by the panel so the panel power output is also maximized so it can generate emergency electrical supply for lighting and other basic needs.


2020 ◽  
pp. 17-21
Author(s):  
A.A. Krolevets ◽  
N.I. Myachikova ◽  
O.V. Binkovskaya ◽  
S.G. Glotova ◽  
K.M. Semichev ◽  
...  

The paper presents the properties of nanostructured Eleutherococcus; self-organization and particle size are determined using the NTA method. It is shown that the smallest size of nanocapsules is in konjac gum (191 nm), and the largest size is in xanthan gum (464 nm). The resulting nanostructured Eleutherococcus can be used in the production of marmalade.


AIHAJ ◽  
1995 ◽  
Vol 56 (3) ◽  
pp. 243-250 ◽  
Author(s):  
Noah S. Seixas ◽  
Paul Hewett ◽  
Thomas G. Robins ◽  
Robert Haney
Keyword(s):  

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 760
Author(s):  
Melinda Hilton ◽  
Mandana Shaygan ◽  
Neil McIntyre ◽  
Thomas Baumgartl ◽  
Mansour Edraki

Coal mine spoils have the potential to create environmental impacts, such as salt load to surrounding environments, particularly when exposed to weathering processes. This study was conducted to understand the effect of physical and chemical weathering on the magnitude, rate, and dynamics of salt release from different coal mine spoils. Five spoil samples from three mines in Queensland were sieved to three different particle size fractions (<2 mm, 2–6 mm, and >6 mm). Two samples were dispersive spoils, and three samples were nondispersive spoils. The spoils were subjected to seven wet–dry cycles, where the samples were periodically leached with deionised water. The rate, magnitude, and dynamics of solutes released from spoils were spoil specific. One set of spoils did not show any evidence of weathering, but initially had higher accumulation of salts. In contrast, broad oxidative weathering occurred in another set of spoils; this led to acid generation and resulted in physical weathering, promoting adsorption–desorption and dissolution and, thus, a greater release of salts. This study indicated that the rate and magnitude of salt release decreased with increasing particle size. Nevertheless, when the spoil is dispersive, the degree of weathering manages salt release irrespective of initial particle size. This study revealed that the long-term salt release from spoils is not only governed by geochemistry, weathering degree, and particle size but also controlled by the water/rock ratio and hydrological conditions of spoils.


2020 ◽  
Vol 989 ◽  
pp. 199-203
Author(s):  
Ivan N. Egorov ◽  
Nikolay Ya. Egorov ◽  
Viktor P. Kryzhanovsky

The paper presents the results of experimental studies of strontium hexa-ferrite average particle size and structural characteristics changes during milling process. Coarse strontium hexaferrite was milled in beater mill, without and with electromagnetic effect. Electromagnetic effect was produced by constant and alternating gradient magnetic fields with mutually perpendicular induction lines. Particle sizes were measured by microscopic methods, and structural characteristics were calculated by processing of X-ray diffractograms. Diffraction studies showed that during milling process, both with and without electromagnetic effect, the most intensive changes of coherent scattering region (CSR) sizes, dislocation densities and relative deformation of particulate material occur at earlier stage of milling. At this stage the speed of average particle size decrease is maximal. At later stage both average particle size and structural characteristic changes correlate and have asymptotic character.


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