| With the rapid development of infrastructure construction in China,higher requirements are put forward for pile foundation construction.Large-aperture DTH hammers are receiving more and more attention for their efficient rock-breaking performance.In order to study the operation status of the large-aperture DTH hammer drilling system in detail,this paper conducts basic research on the DTH hammer from the theoretical,simulation and experimental aspects to find out the relevant factors affecting the drilling efficiency of the DTH hammer.It has important practical significance for the design optimization of large-aperture DTH hammers.From the analysis of the motion principle of the down-the-hole hammer,the mathematical model is established to analyze the force and motion of the piston at different positions.Through the numerical calculation,the pressure loss of the gas supply system is obtained.The simulation model of the DTH hammer drilling system is established by simulation software Amesim to simulate the motionmotion of the DTH hammer under different air supply pressures.The rock breaking mechanism of the down-the-hole hammer is analyzed.Some parameters such as strength,hardness,elasticity and plasticity of the rock under dynamic load are analyzed.Then the rock fragmentation under different dynamic loads is analyzed from the principle of fracture.The bit-rock impact model is established by the dynamic simulation software Abaqus,which sets different impact speeds and rotational speeds to the drill bit,and analyzes the forces acting on different directions of the rock under different working conditions,the rock stress and the drilling depth.Finally,a measurement system is built to acquire upright vibration and air supply parameters.In combination with the recorded working condition of the DTH in field,the influence of air pressure and rotating speed of power unit on impact frequency and drilling efficiency.Drilling efficiency of the DTH in the face of different ground. |
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