Recently, HANFA held a revolutionary industrial experiment, the rotary drill equipped with combination DTH hammer, drill a large diameter (3500 mm), rock formation pile hole.The experiment is very well, and achieved a great success.The success of the experiment, marked the drilling horizontal qualitative changed in HANFA or China.
The present of pile hole drilling
For the pile hole drilling,at present,there are three technology(rotary drilling technology,water reverse circulation drilling technology,heavy hammer percussion drilling technology),but they can not meet the rock pile holes, deep pile hole.There is no better way to solved the problem until the emergence of the experiment.
(1) Rotary drilling technology
This is used for pile hole 1000mm-1500mm in diameter with great efficiency, but slowly for pebble bed, sand layer, weak weathered rock, let alone rock layer. Though it’s also can equipped with multiple air compressors to drill a hone 1000mm in diameter, but the method of air-powered percussion and cuttings removing with high cost still make it can’t be accepted in the industry.
(2) Water reverse circulation drilling technology
It’s widely used for the hole 1000mm-3000mm in diameter, especially for the hole more than 2000mm in diameter with high drilling efficiency, but it’s can’t be used for rock layer and weathered layer formation.
(3) Heavy hammer percussion drilling technology
The hole 1000mm-2000mm in diameter of rock layer, pebble bed is suitable for mud normal circulation drilling. But with a hammer (3-5tons) go into a free falling, it’s the slowest one during the all drilling method. Until now, there is still no other better way to replace it.
The improvement of pile hole drilling technology
In order to solve the existing problems, improve the level of the pile hole drilling, depending on HHANFA ten years mining, trenchless, wells, pile hole, core, manufacturing and construction experience, independent research and development the drill hole process can realize a variety of pile, meet different strata, is replace the current single reverse circulation drill and heavy hammer drill the latest patent product. It can widely used in railway, urban construction, the subway, Bridges, electricity and other large hole pile construction。
For pile hole, water well of large diameter about 400mm-3000mm or super deep(200m-2000m) small diameter (200mm-300mm), which can improve drilling efficiency for 3-5 times, save more than half of equipment investment and 40%-60% oil consumption. The comprehensive and advanced technology can meet all requirement of all formations complex condition.
Patent DTH hammer, tThree-wall drilling pipe, “air be only for percussion purpose and no deslagging” technology
Three-wall drilling pipe is adopted in this technology. In the middle is a pipe to transmit the air for percussion of DTH hammer. And the first annular is used to exhaust to the surface for DTH hammer independently. The second annular is normal circulation for mud travels to the bottom of the hole. And the mud travels back to the surface around the outside of the drill pipe. This is combined the normal circulations of air and mud drilling technology.
Air-power is only used for percussion and exhausting independently, which will makes the drilling efficiency not affected by the drilling depth and underwater. And it will keep the same efficiency like surface drilling. Even though more air is needed according to the increase of the depth, but the drilling depth also can achieved same as depth of mud normal circulation during oil drilling in theory. But the working efficiency of air-power DTH hammer is3-5times improved than roller cone drilling.