Similarity criteria and coal-like material in coal and gas outburst physical simulation

Abstract

Coal and gas outburst is one of the main gas hazards in coal mines. However, due to the risks of the coal and gas outburst, the field test is difficult to complete. Therefore, an effective approach to studying the mechanism and development of outburst is to conduct the similar physical simulation. However, the similarity criteria and similar materials in outburst are the key factors which restrict the development of physical simulation. To solve those problems, this paper has established similarity criteria base on mechanics model, solid-fluid coupling model and energy model, and presented high similar materials. Combining with three groups of similar number, and considering similar mechanical parameters and deformation and failure regularity, the similarity criteria of outburst is determined on the basis of the energy model. According to those criteria, we put forward a similar material consists of pulverized coal, cement, sand, activated carbon, and water. The similar material has high compressive strength and the accordant characteristics with the raw coal, include density, porosity, adsorption, desorption. The new research is promising for preventing and controlling gas hazards in the future.

Experimental Development of Coal-Like Material with Solid-Gas Coupling for Quantitative Simulation Tests of Coal and Gas Outburst Occurred in Soft Coal Seams

“…Coal and gas outburst is an extremely complex gas dynamic phenomenon, in which large amounts of coal and gas are often ejected at a very 2 of 23 fast rate from the coal rock seam to the mining space in a very short period of time (a few seconds to a few minutes). Such outbursts could destroy underground facilities, damage the ventilation system, cause a large number of casualties and even induce secondary accidents such as gas burning or explosion [2,[4][5][6][7]. Today, more than half of the disasters due to coal and gas outbursts occur in China [8], causing major economic losses and casualties.…”

“…Many factors could cause coal and gas outbursts, including in-situ stress, gas pressure, geological structure, physical and mechanical properties of coal, mining methods and so forth. [6][7][8][9][10]. At present, there is no coherent model that can fully reveal their internal mechanism.…”

“…While there was a marked similarity in permeability between natural brown coal and reconstituted specimens, the strength of this type of briquette sample was still lower than natural coal and the gas adsorption/desorption characteristics were also quite different. The third type is pressing a powder mixture consisted of coal powder, cement, sand, lime and other substances [6,10,13,18,19,21,[28][29][30]. Hu et al [13] made coal-like materials using coal powder, cement, water, sand and activated carbon.…”

“…They studied the effect of the proportion of each component on the density and mechanical properties of the samples. In 2017 and 2018, Wang et al [10] and Zhao et al [6] studied the gas and CO 2 adsorption characteristics of such coal-like materials. Zhang et al [30] analyzed the influence of different material ratios on the elastic modulus.…”

“…(2) The similarity remains low between coal-like materials and natural coal in mechanical and physicochemical properties, especially in that the former still have lower strength and very few indexes were measured. Their deformation features and adsorption and desorption characteristics are often not considered and still significantly different from those of natural coal [6,10,13,19,29]. As a result, most simulation studies only reported qualitative rather than quantitative results [13,31].…”