Piling rig hard rock core barrel | Commonly used core coring tools and drilling methods

1. The method of taking out the core
1. Card material card taking method
At the end of the round, throw in the card material (small gravel, iron wire, steel grain) from the ground, and clamp and twist the broken rock core. It is suitable for hard, medium-hard and complete rock and mineral layer hard alloy and steel drilling.

2. How to remove the circlip
The circlip (also known as the breaker) is used to lift the drilling tool a little at the end of the cycle, jam the core and pull it off. It is suitable for diamond drilling of hard and medium-hard rock layers with complete cores and uniform diameters. Coring is convenient and reliable, but the matching accuracy of core diameters and circlips is relatively high.

Requirements for the operation of the circlip and the core
The circlip should have sufficient strength and elasticity. It is processed with spring steel 65 manganese and quenched and tempered steel 40 chromium, hardness HRC45-50.
The free inner diameter of the circlip <0.3mm ± the inner diameter of the drill bit, if the free inner diameter is too large, the core will not be fastened → it will fall off in the middle. The free inner diameter is too small → the core is blocked.
The method to check whether the free inner diameter of the circlip is suitable is to put the circlip on the core, which has a certain holding force and can be gently pushed on the core.
In order to reduce the residual core, the circlip should be placed as close as possible to the bottom of the drill bit.
Do not lift the drilling tool during normal drilling, otherwise the core will be broken prematurely, resulting in core blockage.

3.Dry drilling method
At the end of the second round, stop the water and dry a section, let the rock powder gather at the bottom of the hole to plug the core, and then the drill can be lifted. However, there is the danger of burying and burning the drill. It is suitable for hard alloy drilling in soft or viscous rock formations.

4. Precipitation card method
At the end of the cycle, the circulation is stopped, and the debris in the pipe is allowed to settle and jam the core. It is suitable for reverse circulation drilling of soft, brittle and broken rock formations. Often used in conjunction with dry drilling.

5. Wedge breaker clipping method
At the end of the second round, lift the drilling tool out of the hole, lower it into the wedge breaker, use the hanging hammer to impact the wedge to break the core wedge, and then lower the fixture to lift the core. This method is suitable for drilling large-diameter and relatively hard and complete rock layers.

2. Single-layer core pipe drilling tool - the simplest core drilling tool
In order to improve the extraction rate, the water distribution ball joint and the water distribution cap are added to the single pipe drilling tool. During drilling, the flushing fluid directly enters the core tube through the central hole of the water distribution joint, and the movable water distribution cap is in the shape of an umbrella to protect the core from direct scouring by the flushing fluid, and moves up together with the core.
Before lifting the drill, put the ball valve in to close the central water channel. Under the action of water pressure, when the ball valve moves down beyond the small card, the water hole will be opened, so that the bottom of the hole will form a dry drilling condition.

3. Double-pipe drilling tools
Drilling tools with two layers of core tubes inside and outside are called double-layer core tube drilling tools. In order to overcome the erosion of the rock core by the flushing fluid during single-pipe drilling. An inner tube is arranged in the core tube to accommodate the core, and the flushing fluid flows between the two tubes to avoid direct scouring of the core and protect the core. If the double pipes rotate synchronously during drilling, the inner pipe may still rotate relative to the core, causing damage to the core. The inner pipe does not rotate with the outer pipe during drilling, which not only avoids the scouring of the core by the flushing fluid, but also avoids the adverse effect on the core caused by the rotation of the drilling tool. In difficult-to-coring formations or high-speed rotating diamond drilling, high coring quality can often be obtained.
Structural characteristics of double-pipe drilling tools
In order to reduce the damage to the core caused by mechanical force, a vibration-isolating buffer device is installed in the drilling tool.
In order to reduce the scouring effect on the core, a water blocking and diverting device is installed in the drilling tool.
In order to prevent or alleviate the mutual abrasion of rock and mine cores, a wear-reducing and anti-wear device is added to the double-pipe drilling tool.
In order to prevent the contamination of the rock core, a slurry-separating piston, a press-in inner pipe bit, a sealing device, etc. are provided.
In order to prevent the rock core from falling off, a claw spring, a pressing device, a water-proof ball valve, etc. are provided.

1. Double action double tube
It consists of double pipe joints, inner and outer core pipes, drill bits and check valves. It is generally used for drilling into the loose, easily collapsed and scouring rock formations of I-VII grades.

Commonly used core coring tools and drilling methods
In order to protect the root of the rock core from being washed away, the inner bit of the drilling tool is mostly ahead of the outer bit, generally 20~50mm.

2. Single-action double-pipe drilling tool
It is composed of reducing joint, outer tube, inner tube, single-action device and clamping device. The single-acting bearing sleeve is connected with the inner tube, and the lower end of the inner tube is connected with the short joint and the circlip seat by means of plug connection. Use the thread on the upper end of the mandrel to adjust the clearance between the circlip seat and the inner step of the drill. The clamping device includes a circlip and a circlip seat.

The flushing fluid reaches the circlip seat and the inner step part of the drill bit from the gap between the inner and outer tubes. After the core enters the inner tube, the liquid in the inner tube is discharged between the inner and outer tubes through the one-way valve. At the end of the second round, lift the drilling tool slightly, the circlip moves down relatively to clamp the core, and the circlip seat moves down and abuts on the inner step of the drill bit. At this time, the outer tube bears the tensile force and breaks the core. It is suitable for complete, micro-fractured or heterogeneous, medium-fractured rock formations with grades 7 to 12.

4. Cord Coring Tools
Cord Coring:
The core method is to lift the inner tube and core from the drill pipe to the surface with the help of ropes and special fishing tools without lifting the drill after the core is filled with the core pipe during drilling.

(1) During the core drilling process, lifting and lowering the drilling tool is a time-consuming and laborious auxiliary process. According to statistics, in the not deep drilling, the pure drilling time and the lifting drilling tool each account for about 30% to 40%. The deeper the hole is, the greater the proportion of time it takes to raise and lower the drill. Therefore, wireline coring drilling is a major technological revolution in the field of core drilling. Since the auxiliary time of lifting and lowering drilling tools is reduced, the time utilization rate is improved, so that the rate of return and technical drilling rate can generally be increased by about 25% to 100%.
(2) The rate of mining cores is high. Because the rope coring encounters the core blockage during the drilling process, the agency will report the letter, and the core can be immediately pulled out to extract the core, which reduces the wear time of the core in the core tube, which is beneficial to improve the rate and quality of the core.
(3) The drill bit has a long life. Due to the reduction in the number of drill lifts, the chance of damage to the diamond drill bit is also reduced accordingly. In addition, the gap between the wire coring drill rod and the hole wall is small, and the drill bit works stably, thus prolonging the life of the drill bit relatively.
(4) Strong adaptability to drilling in complex formations. The number of drilling lifts is small, which reduces the chance of the hole wall being exposed. In addition, the drill pipe string can also play the role of casing, so it is beneficial to quickly pass through complex formations.
(5) The labor intensity of workers is low. When drilling with the ordinary drilling method, the number of times of lifting and lowering the drilling tool is large, and the labor intensity of the worker to unscrew the drill pipe is large, while the rope coring drilling can greatly reduce the labor intensity.

The inner diameter of the drill pipe is large and the pipe wall is thin, the material is better, and the machining accuracy is high, which makes the cost of the drill pipe expensive;
There are many supporting equipment for wire-line coring drilling tools, and the one-time investment is large;
The wall of the drill bit is thick, and the power consumption of rock crushing is large when drilling. It works best in hard rock formations of grades 6-9. Generally, it is not suitable to drill 10~12 grade rocks. At this time, the drilling efficiency is extremely low, the drill bit is easily worn, and the advantages of wire-line coring drilling cannot be fully utilized;
The gap between the drill pipe string and the hole wall is small, the wear of the drill pipe string increases, and the circulation resistance of the flushing fluid increases;
Rope coring is generally used in deep holes. Generally, the deeper the hole is, the better the economic and technical effect, but the maximum depth is restricted by the strength of the drill pipe. The large-diameter drill string has high resistance, so its power consumption is large, which affects the high speed in deep holes;

1. Rope coring single-action double-layer core tube - composed of outer tube assembly and inner tube assembly
Outer tube assembly: snap stop head 1 , snap chamber 7 , stable joint 23 (upper reamer), outer tube 46 and drill bit 52 .
Inner tube assembly: spear fishing, clip positioning, suspension, alarm in place, core blockage alarm, single action, inner tube protection and adjustment mechanism.
(1) The spear fishing mechanism consists of the spear fishing head 2 and the recovery pipe 4, etc. During coring, the overshot is lowered in the drill pipe and placed on the upper end of the inner tube assembly, the fishing hook grabs the spear, lifts the overshot upward to move the recovery tube upward, and compresses the elastic clip 6 inward to make it close, so the inner tube assembly It is separated from the outer tube assembly, thereby lifting the inner tube assembly up.
(2) The positioning mechanism of the elastic card: the elastic card 6, the tension spring 5 and the elastic card seat 10. When the inner tube assembly is lowered in the drill pipe, the elastic card is opened outward. Once it reaches the elastic card chamber 7 of the outer pipe, the two wings of the elastic card are attached to the inner wall of the elastic card. The snap chamber stop head can prevent the inner tube from moving upward, and can also drive the upper part of the inner tube assembly bearing to rotate together with the outer tube, so as to avoid the wear of the snap clip due to relative movement.

(3) Suspension mechanism:
The diameters of the inner tube suspension ring 21 and the outer tube seat ring 22 differ by 0.5-1.0 mm. When the inner tube assembly descends to the outer tube spring clip chamber, the suspension ring is seated on the seat ring, so that there is a gap of 2~4mm between the inner tube spring seat 51 at the lower end of the inner tube assembly and the inner step of the drill bit 52 to ensure the single movement of the inner tube.
(4) In-place signaling mechanism: When the flushing fluid is sent down to the inner tube assembly, the flushing fluid passes through the gap between the inner tube and the outer ring; when the inner tube sits on the suspension mechanism, the flushing fluid channel is blocked and the pump pressure increases significantly (0.5~1MPa). ), indicating that the inner tube is in place. At this time, the valve block 39 is opened, the pump pressure returns to normal, and drilling can be performed normally.
(5) Core blockage alarm mechanism: When the core blockage occurs during drilling or the inner pipe is filled, the push force generated by the core to the inner pipe compresses the disc spring, so that the sliding sleeve 24 moves up to block the water hole of the joint 38, causing pump pressure Raised, warn the operator to stop drilling and take out the core.
(6) Single-acting mechanism: two pairs of thrust bearings 29, 31 prevent the inner tube from rotating with the outer tube. 
(7) Inner tube protection (buffering mechanism): When the core is broken, the inner tube and the circlip seat are moved down to the inner step of the drill bit, the pulling force is transmitted from the drill bit to the outer tube, and the inner tube is not damaged.
(8) Adjustment mechanism: When assembling the inner and outer tubes, adjust the gap between the circlip seat and the inner step of the drill (0~30mm).

2. The salvage device - composed of salvage and safety card release mechanism
(1) Salvage mechanism: salvage hook 1, salvage hook frame 3, heavy hammer 7 and wire rope joint. When taking the core, put the fisher into the drill pipe with the wire rope and lower it at a speed of 1.5~2.0 m/s with a heavy hammer. Lift up.
(2) Safe disengagement mechanism: When disengaging is required, a 1m-long casing with a slightly larger inner diameter than the hammer (with an oblique opening on the wall) is put into the wire rope, lowered by its own weight, hits and covers the tail of the salvage hook, forcing it to move toward the end of the hook. Inward contraction, the end opens, so that the overshot is disengaged from the inner tube assembly.

5. Rope coring drilling procedures and operating techniques
(1) Selection and rational use of drill bits
The selection principle of the wire-line coring bit is basically the same as that of the ordinary double-pipe bit. When choosing, it is necessary to combine the characteristics of the rope coring bit, and pay special attention to the following points.

1. Queue use of drill bits
The characteristic of the wire-line coring bit is that it works for a long time at the bottom of the hole. Only when the bit is worn to a certain extent, the drill is lifted for inspection and replacement, so it is more important to use the wire-line coring bit in line. If you don't pay attention to the queuing of the drill bits, it is easy to cause the new drill bits to go down to the bottom of the hole, which increases the workload of reaming. In the same way, the reamer should also be used in line.

2. The new drill should be ground at the bottom of the hole
The lip surface of the rope coring bit has a thick wall and has a variety of lip surface shapes. In order to make the lip surface of the diamond drill bit match the shape of the bottom of the hole, and prevent the lip surface of the drill bit from being inconsistent with the shape of the bottom of the hole, the lip surface of the drill bit is not uniformly stressed. After the drill bit goes into the hole, the initial grinding must be carried out, that is, light pressure (within 1/3 of the normal drilling pressure), slow rotation speed (200 ~ 300r/min), drilling for about 10 minutes, and then continue drilling with normal technical parameters.

3. Determine a reasonable time limit
Wireline coring drilling requires not only high efficiency of the drill bit, but also a longer service life of the drill bit. If the aging of the drill bit is very high and the life of the drill bit is very short, it is necessary to frequently lift and drill down to replace the drill bit, which reduces the drilling efficiency and increases the cost. Therefore, a reasonable time limit must be determined according to the properties of specific rock formations and practical experience. At present, the technical conditions of diamond drilling and the quality level of diamond bits in my country are generally not more than 3m/h. Under the same conditions, compared with the ordinary diamond bit, the wireline coring bit would rather have a slightly lower aging control, and it is also worthwhile to obtain a longer bit life.

4. Determine a reasonable drilling interval
The drill lift interval of wire-line coring drilling not only affects the drilling efficiency, but also affects the life of the drill bit. The larger the drill lift interval, the more pure drilling time and the higher the drilling efficiency; The diamond drill bit is seriously worn and increases the consumption of diamond, so a reasonable drill lifting interval should be determined, that is, the appropriate time to replace the drill bit.
(1) Judging the wear of the bottom lip of the drill bit from the change of the drilling speed.
(2) According to the change of the core diameter, judge the wear of the inner diameter of the drill bit.
(3) According to the change of pump pressure, judge the wear of the bottom lip and nozzle of the drill bit.

5. Prevent drilling accidents
The lip surface wall of the rope coring bit is thick, and a lot of rock powder is generated during drilling. Therefore, it is necessary to make the flushing fluid fully cool the drill bit and remove the rock powder in time, otherwise it will cause a drilling accident. Because the inner and outer tube assembly of the wire-line coring tool is more complicated than the ordinary double-tube structure, and some parts have undergone heat treatment, it is not only difficult to handle the drill-burning accident in the wire-line coring, but also it will cause serious damage to the thin-walled drill pipe. damage, therefore, wire-line coring drilling must prevent drill burn accidents.