Dry Core Bits

(1)Drill choice
Both steel grain drilling and cemented inorganic compound drilling aren't appropriate for foundation pile core testing, and diamond drill bits ought to be used for drilling. The diamond drill cutter is okay, the broken rock is stable, the opening of the excavation is little, the annulated space of the bottom of the crushing hole is little, and therefore the diamond is difficult and abrasive. once the high-speed drilling, the core sample is shortly worn by the drill, that is straightforward to get. the important core sample.
If the concrete strength isn't detected, a drill with Associate in Nursing outer diameter of seventy six millimeter are often used. If it's necessary to check the strength of concrete, it ought to be supported the principle that the diameter of the core sample shouldn't be but three times the most particle size of the mixture, and underneath no circumstances ought to be but a pair of times the most particle size of the mixture. Otherwise, the results area unit extremely distinct.
The take a look at Procedure for Cement Concrete of main road Engineering (JTJ 053-1994) stipulates that the diameter of the core sample ought to be thrice the most particle size of the mixture used for concrete, typically 150mm or 100mm. the most mixture size of the coarse mixture employed in the pile foundation is mostly forty millimeter, and therefore the core diameter ought to be a hundred and twenty millimeter. However, the larger the diameter of the core sample, the upper the core value. Therefore, it's sometimes hand-picked from a core diameter of concerning a hundred millimeter.
(2)gap position
The pile drill features a diameter of but one.2 m, 1 hole, a pair of piles with a pile diameter of one.2 to 1.6 m, and three holes of a pile with a pile diameter of over one.6 m. once the core hole is one, considering that the concrete close to the pipe is comparatively poor in quality, not representative, and additionally convenient for the position of the second hole, it's desirable to open the opening at a footing ten to fifteen cm from the middle of the pile. Of course, there area unit additional lateral reinforcing steel bars within the pile body, and therefore the gap position ought to be at the middle of the pile. once the core hole is 2 or additional, the gap position ought to be uniformly symmetrically organized at intervals zero.15 to 0.25D from the middle of the pile. so as to accurately verify the middle purpose of the pile, the pile head ought to be excavated and exposed; if the pile is just too late to be excavated or inconvenient to excavate, the middle of the pile position ought to be measured by the surveyor's instrument.
(3)Precautions
one For part defective piles, like mud, shrinkage, etc., as a result of the defect vary solely accounts for atiny low a part of the pile section, it's potential that the core hole doesn't taste the half and no defects area unit found, so departure a hidden danger. during this regard, once the development method or non-destructive testing suspects that the pile foundation has such defects, the quantity of drill core holes ought to be enhanced, and therefore the hole position are often biased to the surface once the drilling position is organized, as an example, 3 drill cores area unit organized at equal distances. during this approach, the defects of such piles are often accurately mirrored. The drilling arrangement is mostly not too on the brink of the sting, and therefore the drilling ought to be trained vertically. Otherwise, it's simple to hit the steel cage and can't be trained or trained out of the pile to get the core sample.
a pair of for a few native minor defects, the proportion of the whole section is little, however the seriousness of the defect could also be exaggerated once the opening simply passes through it, particularly once the opening is placed on the axis, as a result of the middle pipe is force up throughout construction. once it's simple to cause native segregation on the axis distribution, the core can't be erroneously judged as severe segregation or broken pile.
three within the preparation stage of the core drilling take a look at, it's necessary to grasp the aim of the take a look at and therefore the basic conditions of the project, like pile kind, elevation, pile length, etc. At a similar time, attention ought to be paid to grouping relevant data. as an example, once the borehole is on the brink of the potential cracks or the concrete might have loose quality, segregation, mud and alternative quality issues and therefore the bottom of the pile, you'll be able to use the suitable drilling methodology and method in time, and concentrate to look at the water color modification and drilling. modification the speed and create a corresponding record.