DRILL PILES

Object of the invention is a method for performing outside injection for into rock drilled drill piles in which case a drill pile pipe is drilled into the ground by using a pilot bit and a ring bit which is attached to it so that it can be detached so far that there is enough drilled hole also in the rock and that in the method the drill pile pipe is pulled into the hole during the drilling and it also functions as a casing pipe by preventing the drilled hole from collapsing in a collapsible soil during the drilling and the injection mass is fed into the interspace of the drill pile pipe and the rock hole.

A method according to the above seen preamble is previously commonly known in order to drill the drill pile pipe into the ground and even a couple of metres into the rock, too, so that a sufficient loadbearing capacity can be achieved for the pile pipe. When the last hole metres are being drilled into the rock, the detachable bit makes a clearly larger hole regarding its diameter into the rock which diameter is the diameter of the pile pipe. This difference may be even 80 mm, or approximately 40 mm on both sides. When the hole for the pile is ready, the pilot drill with its drill rod is pulled away from inside the pile pipe. After this the concrete is moulded inside the pile pipe and usually with a reinforcement. If in the rock part the concrete is not moulded or injected to the interspace of the pile pipe and the rock hole, the pile pipe does not get enough reliable gripping space or prevention of swinging from the rock. In order to solve this problem one has tried to inject concrete between the pile pipe and the rock hole from underneath by bringing the concrete slurry to the top of the pile pipe along the pipework and at that place by rotating from

underneath the ring bit which is left at the top of the pile pipe so that the head of the injection pipe could be arranged to be in the mentioned interspace.

The solution which is presented above has been found to be unsuccessful because one has not been able to verify reliably whether enough concrete slurry went to the interspace or not and whether it rose at that place high enough. Also one has tried to direct the concrete slurry outside the pile pipe from above into the rock hole part but also this method has faced difficulties. In order to remove these disadvantages a new method and equipment has been developed with which one can achieve an essential improvement in relation to the previous technology. It is characteristic of the method according to the invention that the injection mass is directed at the mentioned inner surface with the help of pipes which are attached to the inner surface of the drill pile pipe into the injection depth close to the lower end of the drill pile pipe by which lower end the pipe stops at an edge piece and its direction is turned through the drill pile pipe towards the space to be injected and that in the method the structure of the circle of the outermost pilot bit and the injection pipes of the mentioned inner surface are adjusted to allow the removal of the pilot bit from the hole at least in one circle position of the pilot bit.

It is characteristic of the invention that the injection mass is directed with the help of the pipes which are attached to the inner surface of the drill pile pipe at the mentioned inner surface into the injection depth close to the lower end of the drill pile pipe by which lower end the pipe stops at an edge piece and its direction is turned through the drill pile pipe towards the space to be injected and that in the method the structure of the outermost circle of the pilot bit and the injection pipes of the mentioned inner surface are adjusted to allow the removal of the pilot bit from the hole by arranging the injection pipes to the inner surface of the drill pile pipe with the same spacing as with which the flushing grooves are arranged to the outer edge of the pilot bit and the widths of the flushing grooves are made to be wider than what the width of the injection pipes with their equipment is.

The advantage of the invention is the fact that the injection mass pipes can be reliably taken at the inner surface of the drill pile pipe and their directing into the right depth is easy. The injection mass goes with certainty to the interspace where it belongs. The injection pipes do not get damaged during the drilling and thanks to the check valve which is attached to them and the pipes stay empty till the injection process. The pilot bit can be pulled out after the drilling when the grooves of the outer edge of the pilot bit and the injection pipes are adjusted to have the same spacing in which case the pilot bit can be taken out at least in such circle position in which the pipes are located in the grooves.

In the following the invention is described more detailed by referring to the

accompanying drawing in which Figure 1 shows a drill pile according to the invention and the equipment which drills it as a side view being a partial section view.

Figure 2 shows a check valve as a section view. In the figure 1 there is a drill pile pipe 4 which is pulled into the hole during the drilling and is left there. A hammering pilot bit 1 and a ring bit 2 which is located around it so that it can be detached function as the drilling device. The drill pile pipe 4 is pulled with the help of the ring bit 2 by using a cutter shoe 3 as a middle piece. The flushing of the drilling head is performed along channels 5 and 6 and the waste caused by drilling is removed from the drilling head with the help of the mentioned flow along a groove 7 backwards. The ring bit 2 is attached around the pilot bit 1 with the help of a bayonet connection.

An injection pipe 9 is attached to the inner surface of the drill pile pipe 4 for example by welding at the locations 11. When the diameter of the drill pile pipe 4 is 800 mm or more, the welding is possible inside the pipe. The pipe 9 must be chosen so that it endures the circumstances. For example a pipe with thick walls 0 32/18 is a good alternative. At the desired injection location the pipe 9 is turned through the wall of the drill pile pipe 4 towards the injection space 8. At this stage an edge piece 10 can be used. Also a check valve can be adjusted to the edge piece 10. The pilot bit 1 can be pulled out from inside the pile pipe 4 in spite of the injection pipes 9 and the edge pieces 10. This can be ensured by arranging the flushing agent grooves 7 of the outer surface of the pilot bit 1 to have the same spacing with the injection pipes 9 and by rotating the pilot bit 1 when it is being pulled away so that the injection pipes 9 are located in the mentioned grooves 7. The width of the flushing grooves 7 is also chosen to be such that the pipes 9 and the edge piece 10 have enough room to fit in there. The ring bit 2 is usually made to be so thin that the outer diameter of the pilot bit 1 is very close to the inner surface of the pile pipe 4.

The drill bit studs being located at the drilling surface of the pilot bit 1 and the ring bit 2 and their spacing, positioning and the flushing channels 6 which are located at the drilling surface are designed and implemented in such a way that the pieces of stone which are removed from a rock will be crushed at the drilling surface into a small enough size, to be under 50 mm so that when they are being removed along the flushing groove 7 inside the pile pipe 4 and further out of there, they would not damage the edge pieces 10 or the injection pipes 9.

A check valve which is adjusted to the edge piece 10 is shown in the figure 2 which valve comprises a closing element 12 and it comprises a spring 13 with the help of which spring the closing element 12 can be kept in a closed position. The valve prevents for example water from accessing the pipe 9 if there is water in the hole during the drilling and the valve also prevents drill dust from accessing the pipe from the interspace 8. Feed pressure of the concrete slurry opens the closing element 12 and then the slurry has access for filling the interspace 8. From the amount of the fed concrete slurry one can come to a conclusion, whether the interspace 8 has been filled or not.

It is important for the pile pipe 4 that it gets a good and stabile grip in the rock hole. This is important especially when the pile pipes are used for bridge foundations.