The drill bit is the main component of the drilling rig and a tool for transmitting impact energy. It directly contacts the rock and carries out blasting. In the whole operation process, the stress of the bit is very complex, so the requirements for the material and shape of the bit are very high. Master the technical essentials when using eccentric bit. In the specific construction operation, attention shall also be paid to the following aspects:

 

1. Check whether the downhole impactor, drill pipe, casing and casing shoe are firmly connected, whether the eccentric bit rotates flexibly and whether the ventilation is smooth.

 

2. During drilling, attention shall be paid to the follow-up of casing and powder discharge in the hole. For every 0.3 ~ 0.4 m of drilling, forced hole blowing and powder discharge shall be carried out to keep the hole clean. During drilling, the lifting distance of the central drilling tool shall be strictly controlled to achieve strong drilling and powder discharge. It is strictly prohibited to forcibly pull out the central drilling tool during drilling.

 

3. When the drilling is completed or the central drilling tool needs to be replaced, clean the hole first, blow off the residue at the bottom of the hole, then stop rotating and slowly lift the central drilling tool. The lifting force shall be just enough to lift the central drilling tool, and the lifting height shall reach that the rear of the eccentric bit contacts the front end of the casing shoe; Then reverse the drilling tool at low speed and slowly lift the central drilling tool as far as possible. When it is observed that the central drilling tool can be lifted smoothly, it indicates that the eccentric bit has collapsed. At this time, the central drilling tool can be lifted according to the conventional method until all the central drilling tools are lifted out. When reversing the drilling tool, pay attention to prevent the drilling tool from tripping out.

 

4. Sometimes, due to too much residual rock slag at the hole bottom, the rotating part of the eccentric bit is stuck by rock slag, affecting the collapse of the eccentric bit. When repeated attempts to lift still fail, the compressed air shall be delivered and the drilling hole shall be cleaned again. The DTH hammer shall work for a short time, and then the central drilling tool shall be lifted again.