Study On Uncovering Low Permeable Coal Seam Through Cross Cut By Deep-hole Blasting Technology To Increase Permeability Of Coal Seam

Directing at how to extract the methane in low permeability and high gas-outburst coal seam, this paper researched a new technology that uses deep-hole pre-splitting controlling blast. Its main contents bases on the theory of seam gas occurrence and fluid and the mechanism of deep-hole pre-splitting controlling blast. This paper discussed the particularity of deep-hole pre-splitting controlling blasting in coal seam containing methane, recalling the theory on coal seam gas flow and some related parameters. Analyses and discussion on its process and characteristics during dynamite blasts in coal in detail were also done. It establishes the mathematical model of numerical simulation of deep-hole pre-splitting blast. It issued that proper distance between blasting holes is one of the key factor to get an ideal result of deep-hole pre-splitting controlling blast. Basing on dynamical finite element theory and Mohr-coulomb criterion, this paper simulates stress wave development on time and space, using ANSYS/LSDYNA analysis the two different models. This paper analyzed how the space between blasting hole, guiding hole, coupling coefficient and blasting hole diameter effect the blasting result. It also calculated and get the regular pattern of the two model (distance between two blasting holes are 2m and 4m) established, compared the difference between two models.The simulation shows that in limited space of tunneling face, we should choose proper distance between two blasting holes accord to the scale parameters of tunneling face section and coal rock. If the scale of tunneling face section were small, we should mainly consider the blast stress on coal between two blasting holes, and if the scale of tunneling face section were big, we should mainly consider the blast stress on coal outside two blasting holes. In general, the distance between 2m and 4m can get an ideal result.The spot test shows that deep-hole pre-splitting blast can reduce terra stress and methane pressure effectively, and it is a practical measure which can be used widely to increase methane draining quantity and avoid methane in coal bed outburst.