In foundation construction, rock strata with hardness above moderately weathered are often encountered, which requires a well-equipped pile machine to improve our construction progress. But not all drilling rigs can achieve an ideal level. Here I would like to share some of my personal insights.

First, there is the issue of operator skill. For example, Bauer drilling rigs are recognized in the pile machinery industry as excellent brand rigs, and the quality of their drilling tools is also extremely good. Why is it that during construction they cannot deliver the performance they should?

Let us talk about Kelly drill pipes. As is well known, Kelly drill pipes (commonly known as locking Kelly bars) were invented by the Germans before World War I. They are renowned for stable torque transmission, flexible unlocking methods, and fast hole formation, and are widely used in rotary drilling rigs of various brands. Our country has a vast territory with complex geology such as mountains and hills. In many places, foundation projects face thick underground rock strata with varying degrees of weathering. Under such conditions, Kelly bars can deliver their rock-penetration effect. However, many operators, when penetration is poor, blindly apply pressure. The damage this causes to the drill pipe is long-term and lasting, and without attention to maintenance, accidents inside the hole are very likely. When drilling tools are used properly, there is no need to blindly apply pressure to achieve penetration. There is an old Chinese saying: "Overcome hardness with softness." Blindly applying pressure may not produce good results. The side effects include extreme wear of the drill pipe and inclined drilling of the pile hole, among a series of other problems.

Next I want to discuss our level of understanding of drilling tools and how to better leverage their unique yet very specific functions.

For example: the Beijing-Shanghai High-Speed Railway at Dangjiazhuang, Jinan: pile diameter 1.2 m, pile depth 48-53 m, drilling time 24-30 hours. In local geology, there is moderately weathered limestone at 32-42 m, which is relatively hard, and there are often phenomena of bit balling and slipping. The drilling tool used was the Bauer KBF-K (cutter-tooth sand grab). The result was that after a long time drilling only twenty-odd centimeters, it could not drill any further. The rig mast was pushed up by more than 1 degree under the reaction of the power head, and the drill pipe endured enormous torque and nearly 30 tons of pressure, making it highly prone to twisting or even breaking in the hole. No user wants to see such a situation; this is the consequence of improper selection of drilling tools. A skilled operator must not only have good ability to interpret the strata but also be proficient in using drilling tools, so as to effectively drill through hard rock and soil with the tools.

After many friends watched the short video of Bauer rig coring on our China Rotary Drilling Rig Network (www.44k.cn), they must have thought coring is a very simple matter, and that this sharp tool penetrates rock so heroically. But it also requires an operator of solid competence to achieve twice the result with half the effort. Not every core can be recovered one hundred percent. There are also cases where it cannot be recovered. At such times, a spiral drilling tool with a smaller cone is needed for breaking, rather than using a cutter-tooth sand grab to grind away forcefully. I know many operators who share very similar views. The auger cannot be used in water-filled holes; using it is very dangerous! Dropped rods! If one can grasp the principles of the auger, these problems can be solved one hundred percent. Failure to recover rock and soil is not frightening; what matters is the effect of the drilling tool on breaking the rock and soil. When used in combination with other drilling tools, you will find the hole-forming speed continuously improving. The auger is very effective at breaking rock, but augers with different structures have different breaking effects on rock and soil. Some break sandstone and cobble structures, some break limestone structures, and so on; they cannot be lumped together. We need to carefully analyze and understand them and rationally use their single specialty. I am writing this blog here in the hope that friends in the same field will gain a new understanding of pile machines and drilling rigs, take fewer detours, learn together, and advance together.

Here I want to emphasize that the Bauer series drilling rigs have very excellent quality, and it is not the case, as I said earlier, that they have a high accident rate and cannot drill through. The reason for the high accident rate is that users do not pay attention to maintenance, and the reason they cannot drill through is that users have poor ability to interpret the strata, and also because of the perspective from which they observe the use of drilling tools.