Numerical simulation of impact on pneumatic DTH hammer percussive drilling

Abstract

The process of DTH (down-the-hole) hammer drilling has been characterized as a very complex phenomenon due to its high nonlinearity, large deformation and damage behaviors. Taking brittle materials (concrete, granite and sandstone) as impact specimens, the explicit time integration nonlinear finite element code LS-DYNA was employed to analyze the impact process and the penetration boundary conditions of DTH hammer percussive drilling system. Compared with previous studies, the present model contains several new features. One is that the 3D effects of DTH hammer drilling system were considered. Another important feature is that it took the coupling effects of brittle materials into account to the bit-specimen boundary of the drilling system. This distinguishes it from the traditional approaches to the bit-rock intersection, in which nonlinear spring models are usually imposed. The impact forces, bit insert penetrations and force-penetration curves of concrete, granite and sandstone under DTH hammer impact have been recorded; the formation of craters and fractures has beenalso investigated. The impact loads of piston-bit interaction appear to be relatively sensitive to piston impact velocity. The impact between piston-bit interaction occurs at two times larger forces, whereas the duration of the first impact doesn't change with respect to the piston velocity. The material properties of impact specimen do not affect the first impact process between the piston and bit. However, the period between the two impacts and the magnitudes of the second impact forces greatly depend on the specimen material properties. It is found that the penetration depth of specimen is dependent on the impact force magnitude and the macro-mechanical properties of the brittle materials.

Investigation of insert-hole interference fit influence on downhole drilling bit failure

“…Down-the-hole (DTH) drilling is a rotary-impact drilling method widely used in mining, exploration, water well drilling, road construction and other drilling operations around the world. 1 In this process, bit failure is mainly because of tooth loss, fracture and wear. Lost teeth are usually peripheral ones on the inclined plane of the bit end face.…”

“…The suggested designs can be applied where they are feasible and physically obtainable. 14 Bu et al 1 studied impact stresses of rock, piston, bit and buttons (inserts) in DTH drilling process via threedimensional (3D) simulations. The main effective factors such as piston velocity and rock material were investigated.…”

Dynamic analysis and parameter matching simulation system of DTH Hammer

“…Some predecessors have carried out a series of related work about the computer simulation study of dynamic process of DTH drilling [1][2][3][4] . However, the research is mainly focused on the dynamic analysis of the DTH Hammer without yet established a more comprehensive computer simulation program [5][6][7] , and there is no a software for the evaluation and parameter optimization of the design scheme.…”

Effect of suction nozzle structure on reverse circulation performance of down-the-hole hammer drill bit

“…In hard formations, this technique boasts better penetration rate and straighter bore hole than the other drilling methods [2]. The drilling process is driven by the percussive force on the drill bit, which comes from the high-pressure (HP) compressed air released by the DTH hammer.…”