The process,impacting concrete slab with tungsten carbide button of DTH hammer bit,was simulating calculated by non-linear finite element software LS-DYNA3D on concrete model,the effects of different target mesh sizes of concrete on impaction force,impact velocity and penetration depth was discussed.

Difficulties are encountered in drilling in boulder formation are efficiently eliminated by using of a combined drilling technique which combines casing drilling with DTH drilling method.

Numerical simulation on bottom-hole flow field of down-the-hole bit;

The failure cause was found by analyzing high pneumatic down-the-hole bit bursting crack and the other reasons in the early stage.

Numerical simulation of inner field for three different kinds of down-the-hole drill bits;