This invention will now be described in detail, by way of example but not of limitation, by reference to the annexed figures wherein:
As shown in
Head 1 is connected to devices of known type which cause it to rotate around its own axis until it causes rod 2 to rotate.
Rod 2 consists of a set of (self-drilling) steel bars 3, which are of known type in themselves, and which are connected end-to-end via sleeve couplings 4, with the insertion of high-pressure gaskets 5.
Rod 2 is fitted at its tip with a disposable bit 6, which presents one or more nozzles 7 leading to an axial pipe 8; said pipe 8 communicates with the interior of the drilling rod which, in turn, communicates with a pipe 9 located in the injection head.
A line 11 designed to feed a grout mixture originating from equipment 12 of known type leads to inlet 10 of pipe 9.
Two stages of the process are illustrated in
The equipment, supported by a structure 13, which is only illustrated schematically because it is of known type, is set up at the point to be drilled; the first bar, fitted with a bit at its tip, is mounted on head 11, and drilling begins.
Head 1, connected to a rotary table or other known apparatus which causes it to rotate around its own axis, causes the rotation of bar 3 with bit 6, which begins to drill the ground (
During excavations, grout is pumped at high pressure into pipe 9 and exits through nozzles 7 in the bit at very high speed and pressure, thus removing and compacting the soil around the rod and creating a hole, shown as 14 in
As drilling proceeds, other bars are added to the rod and secured with couplings 5, and drilling continues in this way until the design depth is reached.
If necessary, the rotation of the rod and simultaneous grout injection can be continued for some time, so as to create at the base of the pipe a bulb of larger dimensions which improves interaction with the soil.
When drilling is over, the rod is disconnected from head 1, which is moved to another point, while the rod remains embedded in the grout which has filled the hole. The interior of the rod is also full of grout, acting as reinforcement for the pile thus constructed. As will clearly appear from the description supplied, this technique offers all the advantages of the jet-grouting technology for the production of micropiles, with a high-output process which allows fast, clean operation.
An expert in the field could devise various modifications and variations, all of which should be deemed to fall within the ambit of this invention.