A METHOD AND APPARATUS FOR LINING HOLES FORMED WHEN DRILLING THROUGH EARTH LAYERS

Abstract: A method and apparatus of lining holes (1) formed when drilling through earth layers with the aid of a rotatable, hollow guide rod (5) coupled to a bore crown (3). Flushing medium is flushed down through the guide rod (5) so as to cause drill cuttings to be lifted out of the drilled hole (1) between the guide rod (5) and the wall of the drilled hole. Subsequent to completing a drilling operation, the hole (1) is filled with cement (2) moistened with water, and the guide rod (5) is fed down through the hole while rotating the rod, whereat further cement is introduced into the hole, until the wall of the hole is cemented such as to obtain a hard and smooth lining. The hole is drilled with the aid of a bench-drilling apparatus with separate rotation, and the guide rod comprises a rotatable, hollow guide rod which exhibits in cross-section at least one corner or one wing-like part; the guide rod suitably has a rectangular cross-section and is dimensioned relative to the bore crown in a manner such as to guarantee a straight hole, i.e. the guide rod is somewhat smaller than the bore crown.

Description: A METHOD AND APPARATUS FOR LINING HOLES FORMED WHEN DRILLING THROUGH EARTH LAYERS The present invention relates to a method and an apparatus for lining holes formed when drilling through earth layers with the aid of a rotatable, hollow guide rod coupled to a bore crown, whereat a flushing or rinsing medium is passed down through the guide rod in a manner such as to force material loosened by the drill up out of • the drill hole, between the guide rod and the wall of the hole. The task of drilling holes through consolidated and unconsolidated deposits, such as layers of earth and gravel, is both time-consuming and expensive, since it is necessary to line the walls of the holes with pipes . An object of the present invention is to provide a method by which the walls of holes formed when drilling through layers of earth and gravel can be lined in a less time-consuming and a less expensive manner. A further object of the invention is to provide a novel and useful apparatus for carrying out the method. To this end it is proposed in accordance with the invention that subsequent τo drilling a hole the hole is filled with cement moisτened with water, and thaτ the guide rod is then advanced down through the hole, while being roτated, such as to cement the wall of the hole. In order to obtain a hard and smooth surface, it may someτimes be necessary to add further cement to the hole during the wall-cementing operation. The drilling apparatus used for carrying cut the meτhod according to the invenτion is characterized in that ' iτ comprises a rotatable, hollow guide rod which exhibits in cross-section at least one wing-like part or cogging- edge. Such a dogging-edge can be provided by forming a flaτ on a rod of circular cross-section. Thus, the novel method according to the invention has been made possible by changing the cross-secτional shape of the guide rod used in the drilling operation. A " conventional guide rod has milled therealong three or four straight grooves having a width of about 15 mm and a depth of about 5 mm and along which the loose, drilled material is lifted up out of the drilled hole with the aid of the flushing medium, for example compressed air, which is blown down through the guide rod. Because the guide rod according to the invention has a cross-sectional shape which exhibits at least one wing-like part or a dogging corner, a greater space is obtained for the loose, drilled material ( gravel or drill cuttings) while said corner or wing-like part exerts a pressing and working force on the wall of the hole when lining the same with cemen . As a result of its rigidity and dimensioning relative to the bore crown, the guide rod according to the invention will provide a substantially straight hole, thereby avoiding deviations from a straight line such as to form curved holes. This is a necessary condition for lining the hole of the wall with cement, since it is practically imposs- ible to cement the wall of a curved hole, The guide rod will also guarantee a straight hole when drilling through hard earth layers, such as rock. The method and apparatus according to the invention will now be described in more detail with reference to the accompanying drawing, the single figure of which illustrates schematically a guide rod with associated bore crown which has been drilled through an earth layer, whereafter the wall of the drilled hole is cemented. The figure illustrates a hole 1 which has been bored through earth layers and then lined with concrete 2. The hole is shown to be drilled by means of a bcre crown 3 coupled to a guide rod 5 of rectangular cross-section by means of screw adaptors 4. In turn, the guide rod is coupled in a conventional manner to a drilling machine not shown, for example a bench-drilling apparaτus with separate rotaτion, by means of junction rods, junction sleeves or shank adaptors. Because the guide rod 5 has flat surfaces there is obtained a greater space for the drill cuttings between the guide rod and the wall of the hole, while the four dogging corners defining said flat surfaces exert a press- ing and working force on the walls of the hole, The guide rod 5 is provided at both ends thereof with screw threads- - which enable the rod to be screwed onto both a junction rod or thread adaptor 4 and the bore crown 3. It will be understood that several guide rods 5 may be joined to- gether by means of said thread adaptors when drilling holes through thick earth layers. Downwardly extending test holes with an inclination of about 45 to the vertical have been drilled. The thickness of the earth layer drilled during said test drilling operations was between one and a half and three meters. The guide rod was drilled down through the earth layer throughout the whole of the rod length, which is about two meters. A bench-drilling apparatus with separate rotation was used for the test drilling opera- tions, the guide rod with associated crown being driven at high rotational speed. Air was flushed through the guide rod in a manner such as to force the drill cuttings up and out of the hole, between the wall of said hole and the guide rod. When the guide rod had reached a depth of about two meters, all the drill cuttings had been removed from the hole, and the guide rod was then lifted up out of said hole. The hole- was then filled with cement which was moistened with an aqueous mixture to an extent such as to prevent the cement from being blown away. The guide rod was then passed down through the hole at full rotation without being subjected to hammer forces from the drilling apparatus, whereat air-flushing through the guide rod was held at a minimum, and was only such as to prevent the bore crown from being clogged with cement when said crown was passed down through the hole. At the same time as the guide rod was passed down through the hole, a further quantity of said aqueous mixture was introduced into said hole, although only in an amount such as to prevent the dust from rising. If too much water is added, the cement will adhere to the guide rod and will not be forced out against the wall of the hole in the earth layer. Introduction of cement into the hole is continued until the walls of the hole are cemented and have obtained a hard and smooth structure. In the wall- cementing operation, the dogging corners or wing-like parts of the guide rod act as scrapers which force the cement mixture against the wall of the hole while simulta¬ neously working said wall so that it becomes smooth and hardens to form a smooth and hard concre.te lining on said wall. If the earth layer is thicker than the length of the guide rod, a further guide rod can be adjoined to the first mentioned guide rod by means of a screw adaptor, whereafter drilling is continued and the same method as that described above repeated. When drilling deep holes in earth layers and when water is present in the hole, there is used a vessel filled with dry cement through which the flushing medium is blown, said flushing medium entraining the dry cement therewith, whereafter the mixture of flushing medium and cement is fed down through the guide rod to the bore crown. The said vessel is preferably coupled between a pressure vessel and the drilling apparatus, and an operating valve is connected to the input air-line lead¬ ing to the cement-containing vessel.

Claims: C L A I M S : 1 . A method of lining walls formed when drilling through earth layers with the aid of a rotatable, hollow guide rod which is connected to a bore crown, whereat flushing medium is flushed down through the guide rod so . as to cause drill cuttings to be lifted up out of the drilled hole between the guide rod and the wall of said hole, characterized by filling a drilled hole with water- moistened cement, and by feeding the guide rod down through said hole while rotating said guide rod, rotation of said guide rod being continued until the wall of said hole has been worked and cemented. 2. A method according to claim 1, characterized in that further cement is introduced into said hole, to obtain a hard and smooth surface. 3. A method according to claim 1, characterized in that when the hole is filled with cement flushing of said flushing medium through the guide rod is reduced to a level at which material is not lifted from the drilled hole but at which clogging of the bore crown by cement is prevented. 4. A method according to claims 1 , 2 or 3 , characterized m that the guide rod is lifted from the hole subsequent to a completed drilling operation; that drill cuttings are blown from the hole; and that the hole is filled with moistened cement prior to feeding the guide rod down through the hole while rotating said guide rod. 5. A method according to anyone of claims 1 - , characterized in that the flushing medium is compressed air. 6. A method according to anyone of claims 1 - 4, characterized in that the flushing medium used is foam. 7. An apparatus for carrying out the method according to anyone of claims 1 - 6, characτerized by a rotatable, hollow guide rod (5) which exhibits in cross- OMPI section .at least one dogging corner or wing-like part. 8. An apparatus according to claim 7, characte¬ rized in that the guide rod has a rectangular cross- section. 9. An apparatus according to claim 8, characte¬ rized in that the guide rod .has a square cross-section. 10. An apparatus according to claim 7, characte¬ rized in that the guide rod has a triangular cross- section. 11. An apparatus according to anyone of claims 1 - 10, characterized in that the guide rod (5) is so dimensioned in relation to the bore crown, i.e. is some¬ what smaller than said crown, as to guarantee a straight hole.

Inventors: FRIBERG H, ROSSANDER B
Applicants: FAGERSTA AB, FRIBERG H, ROSSANDER B
Application year: 1981
Main classification: E21B33
IPC codes: E21B33