A Review of Coal Pillar Strength FormulasSince 1900 a number of investigators have studied the problem of predicting the strength of coal mine pillars on the basis of compression tests performed on small samples. From these studies, a number of quite different formulas relating compressive strength and sample size and shape factors …Web

It is thus fully demonstrated that hydraulic fracturing technology bears a positive effect on weakening the strength and integrity of high-level thick and hard gangue, thus promoting the crushing and …Web

The results show that one of the traditional statistical models that receives little attention is more suitable than the others to describe the size effect on particle crushing strength. The intact coal strength, i.e., the strength when particle size d → 0, is in the range 10–88.79 MPa, and the coal mass strength, i.e., the strength when d ...Web

The coal under the action of stress wave had experienced the process from no damage, fracture, crushing and severe crushing. The dynamic strength of the coal sample increased gradually, and the energy of failure process increased gradually. Mechanical Constitutive Model of Coal Sample and its Verification.Web

The results demonstrated that selective crushing obviously reduced the crushing value and calorific value of coal gangue; however, after adding 10% fly ash, it played a buffer role in the base mixture, and the unconfined compressive strength increased by 30.9% to 3.52 MPa in 7 days.Web

The results show that one of the traditional statistical models that receives little attention is more suitable than the others to describe the size effect on particle crushing strength. The intact coal strength, i.e., the strength when particle size d → 0, is in the range 10–88.79 MPa, and the coal mass strength, i.e., the strength when d ...Web

An analysis reveals that the absorbed energy—synonymous with crushing work—escalates as the impact strength augments, instigating a nearly linear rise in the …Web

In this paper, phenolic resin, silicon metal powder, corn starch, and coal tar pitch were used as binder for the fabrication of ferro-coke. I-type drum machine (I 600), scanning electron microscope (SEM), and X-ray diffraction (XRD) were applied to test the crushing strength, morphology, and microcrystalline structure of the ferro-coke.Web

Results show that the crushing strength of coke is improved greatly when the hot pressing is conducted at 420 ℃∼440 ℃ for the 1/3 coking coal. Coke's crushing strength is mainly affected by porosity and pores' spatial distribution. For the high porosity, the coke has thin pore walls and the cracks could easily penetrate the entire coke.Web

1 Introduction Coal and gas outbursts are a dynamic phenomenon controlled by the geo-stress, gas pressure, and mechanical properties of the coal itself. They …Web

tion of coal seams in the UK. The test was then, modified by Paone. et al. ... which allows for obtaining a bigger index of crushing strength than in the case of crushing using the 4–8 mm ...Web

In this study, self-developed grouting equipment was used to reinforce coal with different degrees of crushing. Three coal sizes were used to refer to different …Web

This research delineates the energy dissipation characteristics in coal crushing under impact loads, leveraging the capabilities of Separated Hopkinson Pressure Bar …Web

Ring granulators are used for crushing coal to a size acceptable to the mills for conversion to powdered coal. A ring granulator prevents both the oversizing and undersizing of coal, helping the quality of the finished product and improving the workability. ... At this tensile strength, austenitic manganese steel displays elongation in the 35% ...Web

Coal strength will also increase with increased confining pressure (Hobbs, 1964), as shown in Figure 3.2.At atmospheric pressure or unconfined conditions, dull coals can be two to three times stronger than brighter-banded lithotypes from the same seam with the same rank (Medhurst and Brown, 1998, and Lawrence, 1978), and low rank coals can be up to …Web

The main objective of this research is to investigate the possibility of estimating the crushability of rocks from the impact strength test. For this purpose, the results of the crushing test on twenty-four different rock types were compared with the corresponding results from the impact strength test. 2.Web

The crushing characteristics and strength of coal particles have been explored through numerous experiments. In addition to researches on the crushing of single TDC particles, triaxial loading seepage experiments were also conducted on those with different particle size distributions. The study revealed that varying particle size …Web

Results show that the crushing strength of coke is improved greatly when the hot pressing is conducted at 420 ℃∼440 ℃ for the 1/3 coking coal. Coke's crushing strength is mainly affected by porosity and pores' spatial distribution. For the high porosity, the coke has thin pore walls and the cracks could easily penetrate the entire coke.Web

Compared with intact coal, tectonic coal shows low strength properties and a crushing work ratio of 22.11 J/m 2. The specific surface area and total pore volume of the minipores, mesopores, and macropores of the coal strongly increase under conditions of intense tectonism, which indicates that tectonic coal has a very high capacity for rapid ...Web

The results show that the coal strength has the strongest influence on coal and gas outbursts, followed by the gas pressure and the in situ stress. ... After the primary crushing, the coal particles were mainly concentrated in the particle size range of <0.3, 0.3–1, and >1 mm. Because cement has good hydration reaction and can rapidly ...Web

Moreover, the microstructure mechanical properties of anisotropic coal gangue are highly dispersed, so that concentrated stress is easily generated in the use process, which leads to poor strength of coal gangue. The solmdness and crushing value of gravel were 52 times and 1.46 times that of coal gangue. Therefore, the strength of …Web

crushing strength. Theoretical and experimental tests show that the crushing strength of granular materials follows a weibull distribution [2429– ]. Previous studies showed that the Weibull model can also describe the distribution char-acteristics of the crushing strength of rockll particles, and the power function relationship is adopted …Web

The crushability of twenty-four different rock types were determined and correlated with the corresponding results from the impact strength test. It was found that there is a strong inverse linear relation between the crushability index and the impact strength index. It was shown that there is a strong influence of porosity and density on …Web

Compressive strengths of coal gangue aggregate concretes at 7 and 28 days. ... CGA raw has high carbon and low strength with crushing value of 25.1%, which is a critical problem affecting the utilization of CG as aggregate and needs to be solved urgently. Calcination is an effective method to improve the strength of CG as aggregate.Web

It was observed that increase in crushing fineness resulted in improved coal cake shear strength because of stronger particle-particle binding in case of higher crushing fineness. Also, as blend moisture increases from 7 to 11%, the cake shear strength increases and reaches its maximum value at 11% blend moisture but later on it shows a ...Web

The coal sample's dynamic tensile strength had a strong rate correlation, and the saturated coal sample exhibited the highest rate correlation. ... Ma, Q. Y. & Yuan, P. Characteristics of crushing ...Web

The change in coal strength directly affects the degree of coal crushing. The number of elements deleted due to coal failure in the first 0.01 s in each experiment is counted. Figure 15a shows that based on statistical analysis, the number of failure elements after coal impacts the tail beam decreases with the increasing failure standard. The ...Web

In this paper, the addition amount of iron ore powder (10%, 20%, 30%, 40%, 50%) were used to reveal the effect of iron power amount on the crushing strength of ferro-coke. Then four types of binders (phenolic resin, silicon metal powder, corn starch, and coal tar pitch) were added into the coal to test their effect on the cold and hot …Web

Coal agglomerates of 0.015-0.0277m were produced and the weight and crushing strength of the agglomerates were determined. Kerosene (paraffin oil) was used as a bridging liquid.Web

The crushing of raw coal consumes a huge amount of energy, and generally, the coal strength must be overcome. When the load is large and the coal is fully compacted, it will enter a compaction crushing state [13–16]. The crushing of coal is affected by its strength, local particle size, and impact energy [17–21]. The coal loading …Web

The deformation and failure of the coal-rock combination after loading have gone through four stages (Qin et al. 2017): the compaction stage, elastic stage, plastic deformation stage, and post-peak failure stage are similar to the failure process of coal and sandstone specimens.For the coal-rock combination with 0° dip angle, its ultimate …Web

According to the new surface theory [43, 44], the coal crushing energy was all used to create new surfaces, ... the coal fails, the strength of the system decreases sharply, and the rock is ...Web

Section snippets Coal samples preparation and basic parameter determination. To systematically study the impact crushing of coal with the different hardness under different gas pressure, coal samples from Xiaoqing Coal Mine 7# coal seam in Liaoning (XQ) and Zouzhuang Coal Mine 3 2 # coal seam in Anhui (ZZ) were …Web

Coal and gas outburst is a dynamic phenomenon in underground mining engineering that is often accompanied by the throwing and breakage of large amounts of coal. To study the crushing effect and its evolution during outbursts, coal samples with different initial particle sizes were evaluated using a coal and gas outburst testing device. …Web

This demonstrates that the submerged condition will weaken the jet impact strength, thus affecting the coal crushing effect and the flushing efficiency. Therefore, in underground coal mines, HPWJ flushing operations should be carried out under the nonsubmerged condition. To achieve this goal, it is necessary to keep the drainage …Web

coal body was under pressure, the degree of crushing intensified. e fractal dimension of the particle sizes of broken coal particles followed a logarithmic relationship with the increase in the ...Web

The coal crushing ability (the ease with which it may be ground. to a size enough for use as pulverized fuel) is a physical property affected by parameters of ... Shear strength of fine coal in a ...Web

The maximum strain rate of the tested coal specimens ranged from 67.465 to 99.879 s −1, while the compressive strength ranged from 25.999 to 43.743 MPa. The impact compression test results of hard coal …Web

The coal crushing ability (the ease with which it may be ground to a size enough for use as pulverized fuel) is a physical property affected by parameters of the crushing system. ... (p ¯ = 1.5 MPa) was found to be 20 to 30 times lower than the compressive strength of the coal being pulverized .Web