Soft coal seams with coal and gas outburst tendency do not have impulsion tendency

but rock burst disasters occur in soft coal seams under mining in the deep stope

and the existence of this dynamic disaster is confirmed by literature research and cases analysis. The unconfined unidirectional compression test and bursting liability identification indicated that coal samples were not prone to burst

and the monotonic strain strength softened after ultimate load. To study the mechanism of bursting disasters in soft coal seams

the boundary constraints and loading conditions of the excavating face and the mining face under the engineering background were simulated

and the pressure test under the single-degree-of-freedom border was carried out to investigate the stress

strain

and acoustic characteristics of the whole disaster process. The results showed that when coal samples loaded under the boundary condition of single-degree-of-freedom

the strain strength of all the three coal samples appeared as the process of softening-hardening-bursting

and the softening-hardening process even arose repeatedly. The strain strength hardening degree before bursting was remarkable

and the hardening coefficients of the three coal samples were 1.6

1.53

and 2.25

respectively. After strain strength hardening

the compression strength of coal samples before bursting disaster exceeded the threshold value of bursting tendency. Under the pressure with the constraint of single-degree-of-freedom

the bursting disaster

similar to that happens in hard coal seams

occurred when the strain hardening met the strength requirement of bursting

which reasonably explains the cause of rock burst in soft coal seams. When excavating and mining in soft coal seams with coal and gas outburst tendency under the condition of high stress in the deep mines

it is necessary to pay attention to rock burst caused by strain strength hardening. The intensity of such impulsion is generally not high in engineering

but it can induce highly harmful coal and gas outburst or unusual gas emission.