Particularly in well drilling e.g. for water wells or heating wells and generally in deep drillings or in groundwater areas, an earth pipe should be tightened into a rock hole in a way that the surface waters or the like impurities may not get mixed with the groundwater. In certain countries there already exist clear orders for these kinds of drillings and in the future they will also concern Nordic countries. E.g. in several states in the United States, the measure in question is at present obligatory.
Particularly e.g. in the United States and in the Southern Europe, a traditional method being used for carrying out the tightening mentioned above in a corresponding context, is with reference to the pictorial shown in FIG. 1 such that first of all a basic hole is drilled into the ground, the diameter of the hole being significantly bigger than the earth pipe to be installed therein, whereafter, after the drilling, a separate earth pipe is installed in the hole. After this, the space between the earth pipe and the basic hole is filled with a tightening mass, such as e.g. injection sement or bentonite clay, simultaneously, when the protecting pipe with the big diameter that was used in the drilling, is pulled out from the hole possibly along with its drilling means.
This is a very slow and expensive method, first of all because a significantly bigger hole needs to be drilled than what the earth pipe to be installed would require and on the other hand because the protecting pipe being used in the basic drilling needs to be pulled out from the drilled hole in a separate work stage. In addition to the above, when exploiting the method, also a disproportionately high amount of tightening mass is spent.
A way to carry out earth drilling in a more developed manner compared to prior art is formerly known e.g. from Finnish Patent No. 95618. A drilling head of a drilling unit, existing inside a casing part that operates after the drilling as an earth pipe, in the drilling apparatus presented in this patent, is formed of a first frame part and an annular second frame part, the drilling surfaces of which are provided with drilling organs, such as drill bits or like, of the first and second drilling means or in other words of a center drill or a pilot and a reamer. In this solution, the first frame part forming the the first drilling means, is being released from the second frame part forming the reamer, in order to pull the same out from a drilled hole after the drilling situation together with the drill rods.
A drilling performed with an apparatus according to the patent described above, has been shown as a pictorial in the appended FIG. 2. At present there exist e.g. different kinds of tightening cement mixtures and procedures in order to achieve tightening of an earth pipe also when performing this type of drilling. In such a drilling, after the casing part has been drilled into a rock and the first drilling means or the pilot has been pulled out, e.g. a freshly mixed batch of cement is dropped on the bottom of the hole, which is e.g. “crushed” on the hole bottom by a rock drill bit. There is, however, such a problem at present, that in the so called ring drill bits according to the patent described above, there doesn't exist any clear route for leading of the tightening mass outside the casing part in order to achieve an external coupling of the casing part with the rock hole. Thus, according to the rightmost view in FIG. 2, the tightening mass may not enter at all or will not get drifted fast enough in every case outside the casing part before the tightening mass gets solidified, which is why actual external tightening of the casing part or anchoring of the same, can not be carried out reliably enough.