In order to solve the problems of auger pipe, wide blade drill pipe and triangular drill pipe in the construction of soft protruding coal seam drilling, card drilling and buried drilling are introduced, an integral triangular auger pipe is introduced, the structural characteristics of the drill pipe are discussed, the processing technology is studied, and the drill pipe is trial-produced. The torsional strength of the drill pipe is proved to meet the design requirements by performing the upper and lowering tests and fracture analysis of the drill pipe specimen. The integral three-sided auger pipe was tested in the drilling industry with the ZDY-3200S full hydraulic drilling rig, and its hole completion rate was 100%.
In the process of coal mining, gas extraction is a fundamental measure to prevent accidents such as coal and gas protrusion and explosion. Coal seam drilling and gas extraction process has been widely used as one of the fundamental measures to prevent and control coal mine gas disasters. However, for the soft protruding coal seam, especially in areas with high ground stress, drilling construction is very difficult, prone to abnormal phenomena such as nozzle hole, collapse hole, card drilling, etc., resulting in low drilling rate, shallow drilling depth, and the drilling depth in the soft coal seam is generally not more than 100m, which seriously affects the gas extraction effect of drilling.
At present, the drill pipe used in the construction of soft protruding coal seam drilling underground coal mines is mainly auger pipe, wide blade drill pipe and triangular drill pipe.
(1) Auger drilling is a dry rotary drilling method, the auger pipe and the drill hole form a spiral conveyor belt, the auger pipe continuously conveys the slag broken by the drill bit to the outside of the hole. Auger drilling effectively solves the problem of slag discharge, but it is difficult to drill holes and form holes.
(2) Wide blade drill pipe is based on auger pipe, without changing the spiral angle and pitch, reduce the height of the spiral blade, increase the thickness of the blade, so that the drill pipe can pass through the inner hole of the rotator chuck and the gripper, realize the drilling rig to unscrew the drill pipe, without the use of active drill pipe, while reducing the scraping of the inner wall of the drill hole by the spiral blade (fin), improving the drilling stability and drilling efficiency. However, the slag discharge space of the wide-blade drill pipe is smaller than that of the auger pipe, and the slag discharge efficiency is low.
(3) The slag discharge mechanism of the triangular drill pipe is to form 3 arc-shaped spaces between the drill pipe and the drilling wall, which expands the channel for excluding pulverized coal and gas. Drill pipe in the process of drilling, the pulverized coal stirred up, can play the role of secondary crushed coal, pulverized coal in the state of motion is blown out by the pressure wind, can effectively solve the problem of auger pipe slag discharge channel is blocked, drilling is not easy to occur stuck drilling, holding drill phenomenon. However, the processing quality of triangular drill pipe is difficult to control, and the strength is lower than other drill pipes of the same specification, and the phenomenon of broken rod and lost drilling often occurs during the drilling process, which increases the cost of drilling. Therefore, the author designed the integral triangular auger pipe to solve the above problems that occur in the drilling of auger pipe, wide-blade drill pipe and triangular drill pipe in the construction of soft protruding coal seam.
1. Integral triangular auger pipe structure and working principle
The integral triangular auger pipe structure is shown in Figure 1. The drill pipe is an integral structure, the two ends are male and female joints, the outer contour of the section of the drill pipe body is similar to the triangular drill pipe, but there are discontinuous spiral grooves on the outer wall of the drill pipe.
Integral triangular auger pipe combines the advantages of auger pipe and triangular drill pipe, the structure of the triangular prism increases the annular overflow area between the outer wall of the drill pipe and the hole wall, the drill pipe rotates in the soft protruding coal seam can cause the vortex flow, relying on the 3 edges of the drill pipe to raise the pulverized coal deposited at the bottom of the drill hole, so that the pulverized coal in the hole has been in motion, avoiding the accumulation of pulverized coal in the drill hole;
At the same time, the spiral groove on the outer wall of the drill pipe can assist in slag discharge, and when there is a case of stuck drilling and buried drilling, the collapsed hole can be dredged with the help of the pickpocket function of the spiral groove
The structure of the integral triangular auger pipe shows that the integral triangular auger pipe has the following characteristics:
(1) The integral structure improves the torsional strength and bending strength of the drill pipe;
(2) The thickening design is adopted at the joints at both ends of the drill pipe, which effectively ensures the wall thickness of the threaded end;
(3) Compared with auger pipe, the hardness and strength of the blade are high and the wear resistance is good;
(4) Compared with the triangular drill pipe, the spiral groove can continuously transport the cinder moving inside the hole to the outside of the hole;
(5) The wide blade structure reduces the scraping of the hole wall by the blade and ensures the stability of the hole wall.
2. The processing technology of drill pipe
The material of the integral triangular auger pipe is 42CrMo thick-walled pipe material with high strength and good toughness, and the overall tempering and tempering treatment has a hardness of HRC32~37 to ensure that the drill pipe has good comprehensive mechanical properties.
According to the structure of the drill pipe, the processing process of the drill pipe is determined to include the following four processes:
