Influencing Factors And Numerical Analysis On The Impact Crushed Rocks By Pneumatic DTH Hammer

Pneumatic Down-The-Hole (DTH) Hammer has the advantages of fast speeding and high efficiency drilling. And which has been widely used in geology, mining, construction and other engineering fields. The mechanism of impact crushed rock by Pneumatic DTH Hammer is that it is the role of compressed air on the hammer which then passes to the drill bit. Analysis on the rock properties, damaging effects of rockon static and dynamic loads as well as the mechanism of it is done by numerical analysis on the process of ball drilling teeth impact crushing the rocks which is based on the nonlinear dynamic finite element analysis software ANSYS/LS-DYNA. At last according to the intrusive destruction test of conical indenter on the argillaceous limestone, the rock failure is analyzed in process of indenter invading the argillaceous limestone.This paper carried out the following aspects of research work and had drawn the corresponding research results:(1) Through the analysisof the mechanical properties, rock strength and rock failure criteria of rock under static and dynamic role, we provided a theoretical basis for the analysis of mechanism of impact crushed rock by Pneumatic DTH Hammer;(2) According to the analysis on the structure and tectonics of the Pneumatic Down-The-Hole Hammer, we did a lot of research on the stress wave characteristics and the influence on stress wave by impact hammer in process of rock failure;(3) By using of the nonlinear explicit finite element software ANSYS/LS-DYNA, the three-dimensional numerical simulation of the impact crushedrock by ball drilling teeth is done, and the stress and shear stress changes on the vertical z-direction and the horizontal x-direction in process of ruck failure.(4) Two-dimensional numerical simulation of the rock failure process damaged by dome drilling teeth, conical drilling teeth and the drilling teeth is done by use of ANSYS/LS-DYNA. According to the analysis on the changes of von-mises stress and XY stress of the rocks under impact loading, we could see that the maximum stress of rock von-mises is ranged by10～30MPa and which of the XY stress is2-6MPa. From the crack propagation and numerical simulation results of the failure process we can see that under impact loading by ball drilling teeth the vertical cracks first appears on either side of the contact position with the rock drilling teethand vertical rock cracks expands to the interior of the rock. However, with the constant intrusion of the drilling teeth, vertical cracks began to extend on both sides formattingtothe transverse cracks which finally moved upwards through the rock surface and formatted into broken blocks.At the same time there generated vertical cracksand extended to the deep. It will also generate crushing blocks deep inside the rock because of crack propagation in the process of rock failure by the conical drilling teeth, but the vertical crack ranged smaller, the invasion depth was greater and the speed of the drilling teeth changedslowly while the warheads type drilling teeth wasin between.It can be seen that the ball drilling teeth is more suitable for drilling crusherin hardand medium hard rock formations, the cone drilling teeth is suitable for crushing in the soft rock formations, and the warhead type of drilling teeth is in between..(5) From the invasive destructive test of conical indenter on the argillaceous limestone, we analyzed the direct relationship between invasion depth and loading and achieved the conclusion that the invasion depth increased with the loading while invading in the end the rocks cracked into pieces, crushing pit and fragmentation pit.