Operation method of impact rotary drilling with down-the-hole hammer
The operation method of impact rotary drilling is to install a down-the-hole hammer between the lower end of the rotating drill pipe column and the coring drill, so that the impact pulse, axial drill bit pressure and drill pipe rotation torque act on the drill bit at the same time to achieve drilling and core collection. This drilling method originated in Europe in the early 19th century. The Chinese Ministry of Geology began to study it in 1958 and developed rapidly in the 1970s. Its main advantages are that it can greatly increase the drilling speed and the length of the round footage in hard rock formations, reduce the degree of borehole bending, and significantly reduce the drilling cost. Impact rotary drilling is usually achieved by two types of hammers. One is to use the hammer driven by the energy of the drilling fluid, which is called hydraulic impact rotary drilling, and the other is to use a pneumatic hammer driven by compressed air, which is called pneumatic impact rotary drilling. The following mainly introduces hydraulic impact rotary drilling.
The hydraulic impact rotary drilling system uses a mud pump to pump drilling flushing fluid through the drill pipe into the hammer to drive the hydraulic hammer to impact the core tube and drill bit. The drill pipe is driven by the drilling rig to rotate and pressurize the drill bit. This drilling method can also be combined with rope coring drill tools, called rope coring hydraulic impact rotary drilling. Before drilling begins, the hydraulic hammer and the inner core tube suspended by the spearhead are put into the rope coring drill pipe from the ground, and then the drilling flushing fluid is pumped into the drill pipe to drive the hammer for drilling and coring. At the end of the return, a thin steel wire rope is used to put the salvage device and the hammer and the inner core tube are lifted out of the ground by a special winch.
The hydraulic hammer is the main tool for impact rotary drilling. According to its working principle, it can be divided into three types: positive action, double action and reaction action. Depending on the impact frequency, those with a frequency higher than 40 Hz are high-frequency hammers, which can be equipped with diamond drill bits. Rock crushing is mainly done by rotation and supplemented by impact, which is called hydraulic rotary impact drilling. Those with a frequency less than 40 Hz are low-frequency hammers, which are often equipped with carbide drill bits. Rock crushing is mainly done by impact and supplemented by rotation, which is called hydraulic rotary impact drilling.
