DK169043B1 - auger - Google Patents

Abstract

Drilling apparatus, in particular for drilling of holes preferably in soil consisting essentially of glacier deposits or comparatively soft rocks, said drilling apparatus comprising a drilling pipe with a cutter head, the drilling pipe consisting of two coaxial pipes forming an interspace, through which a drilling medium such as water or air can be introduced, and in which drilling pipe the cutter head is placed on the end, which is in front during the drilling, the cutter head comprising a number of hard metal bits and nozzles in between, through which the drilling medium can flow under pressure. To obtain an effective conveyance of the material removed during the drilling through the inner of the drilling apparatus, through which it should also be possible to introduce for instance liners, the drilling apparatus is constructed in such a way that the clear of the inner one of the coaxial pipes is unobstructed, that in addition to the nozzles in the cutter head a number of radially inwards directed nozzles is provided at a short distance from the cutter head and a number of ejector nozzles, which is directed obliquely inwards in a direction away from the cutter head.

Description

i DK 169043 B1in DK 169043 B1

Den foreliggende opfindelse angår et jordbor af den i indledningen til krav 1 angivne art.The present invention relates to a soil drill of the kind set forth in the preamble of claim 1.

Et jordbor af denne type er beskrevet i USA-pa-tentskrift nr. 3.638.741. Det kendte jordbor er beregnet til 5 fremstilling af hegnsstolpehuller og er derfor udformet som et håndværktøj. Det kendte jordbor har ud over de to koncentriske rør, mellem hvilke boremediet føres frem til borekronen, et centralt rør, der kan tilsluttes til den samme eller en anden kilde for boremedium, som tilføres i store 10 mængder til borttransport af den jord, som ved boringen trænger op i det indre af de to koncentriske rør. Det centrale rør, som forløber i hele borets længde, udgør en hindring for indføring af et foringsrør eller en sugespids i borehullet, medens boret stadig befinder sig i borehullet.A soil drill of this type is disclosed in U.S. Patent No. 3,638,741. The well-known earth drill is intended for the manufacture of fence post holes and is therefore designed as a hand tool. The known soil drill has, in addition to the two concentric tubes between which the drilling medium is advanced to the drill bit, a central tube which can be connected to the same or another source of drilling medium, which is supplied in large quantities for the transport of the soil which by the bore penetrates the interior of the two concentric tubes. The central pipe extending throughout the length of the drill constitutes an obstacle to insertion of a casing or suction tip into the borehole while the drill is still in the borehole.

15 Denne ulempe er betydningsløs ved fremstilling af stolpehuller, men hindrer anvendelsen af boret til dybere boringer, der skal udføres, f.eks. brøndboringer til grundvandssænkning, drikkevandsudvinding eller lignende.This disadvantage is meaningless in the manufacture of post holes, but prevents the use of the drill bit for deeper bores to be performed, e.g. wells for groundwater lowering, drinking water extraction or the like.

Ved fremstilling af dybere boringer til fremstilling 20 af brønde og lignende anvendes normalt et bor udformet som et enkelt rør, som afsluttes med en borekrone eller en mejsel. Boremedium føres frem til borekronen gennem rørets indre og undviger langs borerørets yderside sammen med det ved hjælp af borekronen løsgjorte materiale. Også dette normalt 25 anvendte bor har den omtalte ulempe, at en foring eller en sugespids ikke kan indsættes i den borede brønd, før boret er fjernet.In the preparation of deeper bores for the preparation of wells 20 and the like, a drill formed as a single tube is usually used which terminates with a drill bit or chisel. Drilling medium is advanced to the drill bit through the interior of the pipe and avoids along the outside of the drill pipe along with the material released by the drill bit. Also this normally used drill has the disadvantage mentioned that a liner or suction tip cannot be inserted into the drilled well until the drill is removed.

Formålet med opfindelsen er at videreudvikle det indledningsvis nævnte bor på en sådan måde, at det bliver an-30 vendeligt også til dybere boringer, og så det tillader indsættelsen af en foring i den borede brønd, inden boret fjernes.The object of the invention is to further develop the initially mentioned drill in such a way that it is also applicable to deeper wells and so permits the insertion of a liner into the drilled well before the drill is removed.

Dette formål tilgodeses ved, at boret er karakteriseret ved det i den kendetegnende del af krav 1 angivne.This object is met by the fact that the drill is characterized by the part of claim 1.

35 Tilføjelsen af de radialt indefter og skråt opefter- rettede ekstra dyser, som er rettet ind mod den fri indre lysning i boret, medfører, at det ved boringen friskårne materiale sønderdeles og ved hjælp af de skråt opefter rettede DK 169043 B1 2 dyser bringes til at strømme op gennem den centale lysning sammen med boremediet. Praktiske forsøg med en prototype af boret har vist, at boret i moræneaflejringer, såsom ler og sand, arbejder væsentligt hurtigere end de sædvanligvis an-5 vendte bortyper, samt at forbruget af boremedium reduceres væsentligt på grund af den kortere boretid. Typisk er boret ca. 6 gange så hurtigt som det normalt til dybere boringer anvendte bor med en som en mejsel udformet borekrone.35 The addition of the radially inwardly and inclined upwardly directed nozzles, which are directed towards the free internal illumination of the drill, causes the freshly cut material to be broken at the bore and by means of the inclined upwardly directed DK 169043 B1 2 nozzles. to flow up through the central illumination along with the drilling medium. Practical experiments with a prototype of the drill have shown that drilling in moraine deposits, such as clay and sand, works significantly faster than the commonly used drilling types, and that the consumption of drilling medium is significantly reduced due to the shorter drilling time. Typically, the drill is approx. 6 times as fast as normally used for deeper bores with a chisel-shaped drill bit.

I henhold til en særlig foretrukken udformning af bo-10 ret ifølge opfindelsen er dette udformet således, at der kan udtages borekerner, der kan anvendes til analyse af de jordlag, hvori der er boret. Denne udformning er kendetegnet ved det i krav 2 angivne. Ved udformningen ifølge krav 2 styres tilførslen af boremedium ind i den fri lysning af boret ved 15 hjælp af en ændring af borets rotationsretning. Når der skal udtages en borekerne, bringes boret til at rotere i en sådan retning, at de ekstra dyser afspærres, hvorved der opbygges en kerne i borets indre. Kernen kan tages op enten ved at boret tages op eller, hvis boreprøven ikke skal have særlig 20 store dimensioner, kan den bringes op ved hjælp af ejektor-dyserne, der sættes i drift ved at ændre borets rotationsretning .According to a particularly preferred embodiment of the drill according to the invention, this is designed so that drill cores can be extracted which can be used for analysis of the soil layers in which the drill is drilled. This configuration is characterized by that of claim 2. In the embodiment according to claim 2, the supply of drilling medium is controlled into the free illumination of the drill by a change of the direction of rotation of the drill. When a drill core is to be removed, the drill is made to rotate in such a way that the extra nozzles are blocked, thus creating a core in the interior of the drill. The core can be picked up either by picking up the drill or, if the drill sample does not have very large dimensions, it can be brought up by means of the ejector nozzles which are put into operation by changing the direction of rotation of the drill.

Andre fordelagtige udformninger fremgår af de øvrige uselvstændige krav.Other advantageous designs are apparent from the other dependent claims.

25 Opfindelsen skal i det følgende beskrives nærmere un der henvisning til tegningen, på hvilken:The invention will now be described in more detail with reference to the drawing, in which:

Fig. 1 perspektivisk viser den forreste del af et jordbor ifølge opfindelsen i delvis gennemskåret tilstand, fig. 2 viser endefladen af den ene del af et af to i 30 forhold til hinanden vinkelforskydelige dele bestående bor ifølge opfindelsen, og fig. 3 viser den forreste del af et af to dele bestående bor svarende til udformningen ifølge fig. 2 set fra siden.FIG. 1 is a perspective view of the front part of a soil drill according to the invention in partially cut-away condition; 2 shows the end surface of one part of one of two angularly displaceable borings according to the invention, and FIG. 3 shows the front part of one of two parts drilled in accordance with the configuration of FIG. 2 seen from the side.

35 Fig. 1 viser den forreste ende af et jordbor 1 omfat tende dets borekrone. Jordboret er opbygget af to koncentriske rør 2 og 3, mellem hvilke der er et annulært mellemrum, der strækker sig i hele borets længde. Mellemrummet DK 169043 B1 3 danner under borets drift en tilførselskanal for det anvendte boremedium, der kan være vand, boremudder eller luft afhængig af boreopgavens art og typen af det til boret hørende hjælpeudstyr. De to koncentriske rør er ved borets forreste 5 ende forbundet med hinanden ved hjælp af en endevæg 4, der udgør basis i borets borekrone. Borekronen omfatter et antal hårdtmetalplatter 5, der i den viste udformning har form omtrent som en champagneprop med et cylindrisk skaft 5a, der er indsat i en i borets aksialretning forløbende boring i 10 endevæggen 4 og med et tilnærmelsesvis halvkugleformet hoved 5b. Hårdtmetalplatterne er fortrinsvis placeret med indbyrdes afstand langs to koncentriske cirkler på en sådan måde, at de halvkugleformede hoveder på hårdtmetalplatterne rager en smule uden for henholdsvis den indvendige væg af det ind-15 vendige rør og den udvendige væg af det udvendige rør 2. Hårdtmetalplatterne 5 bliver derved i stand til at nedbryde den jord, som boret arbejder i, i et så bredt spor, at der er frigang omkring boret.FIG. 1 shows the front end of an earth drill 1 comprising its drill bit. The ground drill is made up of two concentric tubes 2 and 3, between which there is an annular gap extending the entire length of the drill. The space DK 169043 B1 3 forms during the drilling operation a supply channel for the drilling medium used, which may be water, drilling mud or air depending on the nature of the drilling task and the type of drilling auxiliary equipment. The two concentric tubes are connected to one another at the front end of the drill by means of an end wall 4 which forms the base of the drill bit. The drill bit comprises a plurality of cemented metal plates 5, which in the embodiment shown are similar in shape to a champagne plug with a cylindrical shaft 5a, which is inserted into a bore extending in the axial direction of the drill bit in the end wall 4 and with an approximately hemispherical head 5b. The cemented carbide plates are preferably spaced apart along two concentric circles in such a way that the hemispherical heads of the cemented carbide project slightly beyond the inner wall of the inner tube and the outer wall of the outer tube 2. The hard metal plates 5 thereby being able to break down the soil in which the drill works, in such a wide track that there is clearance around the drill.

Under boringen bringes boret til at rotere, hvorved 20 borekronen med hårdtmetalplatterne løsner jorden foran boret. Møder boret en sten eller andre hårde forekomster i jordlagene, knuses disse af hårdtmetalplatterne. Den løsnede jord fjernes fra området foran boret ved hjælp af et antal stråler af boremedium, som udsendes fra et tilsvarende antal 25 i det væsentlige aksialt rettede dyser 6 i endevæggen 4. Dyserne 6 kan ved en foretrukken udformning omfatte to serier af dyser, hvor den ene serie danner en vinkel på 10-15* indefter mod borets akse og den anden serie tilsvarende danner en vinkel udefter på 10-15* i forhold til borets akse.During drilling, the drill is caused to rotate, thereby loosening the drill bit with the hard metal plates to the ground in front of the drill. Meetings drilled on a rock or other hard deposits in the soil layers are crushed by the cemented carbide plates. The loosened soil is removed from the area in front of the drill by a number of jets of drilling medium emitted from a corresponding number of 25 substantially axially directed nozzles 6 in the end wall 4. The nozzles 6 may, in a preferred embodiment, comprise two series of nozzles, the one series forms an angle of 10-15 * inwards towards the axis of the drill and the other series correspondingly forms an angle of outwards of 10-15 * with respect to the axis of the drill.

30 Den centrale kerne, som ved boringen efterlades i lysningen i det inderste rør, sønderdeles og transporteres op af borehullet ved hjælp af boremedium, som indsprøjtes gennem dels et sæt i det væsentlige radialt indefter rettede dyser 7, dels gennem et sæt skråt opefter rettede ejektordy-35 ser 8. Ud over den funktion at transportere det sønderdelte materiale op fra borehullet gennem borets indre regulerer ejektordyserne tillige det statiske tryk på søjlen af boremedium på borets yderside. Det er ønskeligt, at kun en min- DK 169043 B1 4 dre del af det frigjorte materiale transporteres opefter langs borets yderside, hvor det vil øge friktion og slitage på boret under dets rotation. Dyserne 6 er anbragt i kort afstand fra borets endeflade, medens dyserne 7 kan være an-5 bragt i nogen afstand fra enden af boret. Afstandens størrelse er ikke kritisk, men fortrinsvis er den forholdsvis lille, således at der skabes en zone i det indre af borets forreste ende med en meget kraftig turbulens, der effektivt sønderdeler det materiale, som under boringen føres op i bo-10 rets indre, efterhånden som boret trænger frem eller ned i de jordlag, hvori der bores. Ved boret ifølge opfindelsen bringes det opborede materiale ud af borehullet i en sønderdelt og opslemmet tilstand i det boremedium, som bruges til boringen. Som boremedium anvendes normalt vand, der tilføres 15 under et tryk på 12-20 bar, men boret er tillige anvendeligt med et boremudder, som er fortykket med f.eks. bentonit, eller med luft, som tilføres under et tilsvarende eller noget højere tryk. Ved boringer, som udføres, hvor rigelige mængder af vand ikke er til rådighed, er luft et foretrukket al-20 ternativ, der i praksis er særdeles håndterligt og effektivt, især fordi boret ifølge opfindelsen arbejder meget hurtigt i forhold til kendte bor, hvorved det til boringen nødvendige luftforbrug bliver moderat, idet det begrænses af den kortere boretid.The central core, which is left at the bore in the hole in the inner tube, is disintegrated and transported by the borehole by means of drilling medium injected through a set of substantially radially inwardly directed nozzles 7 and partly through a set of oblique upwardly directed ejector nozzles. -35 see 8. In addition to the function of transporting the disintegrated material up from the borehole through the interior of the drill, the ejector nozzles also regulate the static pressure on the column of drilling medium on the outside of the drill. It is desirable that only a minor part of the released material be transported upwards along the outside of the drill, where it will increase friction and wear on the drill during its rotation. The nozzles 6 are located at a short distance from the end surface of the drill, while the nozzles 7 may be located at some distance from the end of the drill. The size of the spacing is not critical, but preferably it is relatively small, so as to create a zone in the interior of the front end of the drill with a very powerful turbulence that effectively disintegrates the material brought into the drill's interior during drilling. as the drill penetrates or descends into the soil layers in which it is drilled. In the drill according to the invention, the drilled material is brought out of the borehole in a disintegrated and suspended state in the drilling medium used for the drilling. As the drilling medium, water is normally used which is supplied under a pressure of 12-20 bar, but the drill is also useful with a drilling mud which is thickened with e.g. bentonite, or with air supplied under a corresponding or slightly higher pressure. In wells carried out where copious amounts of water are not available, air is a preferred alternative which is in practice extremely manageable and effective, especially because the drill according to the invention works very quickly in relation to known wells, The air consumption needed for drilling becomes moderate, being limited by the shorter drilling time.

25 I henhold til en særlig udformning af boret ifølge opfindelsen kan det udformes således, at det er muligt at optage sammenhængende borekerner. Udformningen, der er vist på fig. 2 og fig. 3 omfatter en forreste del af boret 1 omfattende dyserne og borekronen vist på fig. 3, hvilken for-30 reste del er drejelig i forhold til borets øvrige skaft, hvis forreste ende er vist på fig 2. De to dele af boret er samlet langs en deleflade, der tjener som ventil til styring af tilførslen af boremedium til de ind i det indre af lysningen i det indre rør rettede dyser.According to a particular embodiment of the drill according to the invention, it can be designed so that it is possible to receive continuous drill cores. The design shown in FIG. 2 and FIG. 3 comprises a front portion of the drill 1 comprising the nozzles and the drill bit shown in FIG. 3, the forward part being rotatable with respect to the other shaft of the drill, the front end of which is shown in Fig. 2. The two parts of the drill are assembled along a dividing surface which serves as a valve for controlling the supply of drilling medium to the nozzles were directed into the interior of the aperture in the inner tube.

35 Fig. 2 viser en udformning af delefladen 9 på bor skaftets forreste del. Delefladen omfatter et sæt nøglehulsformede åbninger 10, der tjener til optagelse af et tilsvarende sæt tappe 11, der er placeret på den med delefladen 9 DK 169043 B1 5 samvirkende endeflade 12 (fig. 3) af borskaftet 13. Tappene 11 har et hoved 14/ som netop kan passere gennem den udvidede del 15 af åbningerne 10. Efter indsætning i åbningerne 10 låses tappene i den snævre del af åbningerne 10 ved hjælp af 5 sætskruer 16. Tappene 11 kan ikke passere forbi skruerne ud i den udvidede del, og de to dele af boret er derved sikkert sammenholdt. Delefladen 9 indeholder yderligere nogle huller 17, som er forbundet med kanaler, som forsyner de indefter mod det indre af boret rettede dyser med boremedium. Disse 10 huller 17 er placeret ud for huller 18 i endefladen 12 på en sådan måde, at hullerne 17 og 18 er på linie i den vinkelstilling, som de to dele indtager, når tappene befinder sig i den ene ende af de nøglehulsformede åbninger, og forskudt så meget i forhold til hinanden, at der ikke er passage, når 15 tappene 11 befinder sig i den placering, der er afgrænset af sætskruerne 16. I den stilling, hvori de ind mod lysningen rettede dyser er lukket, befinder hullet 18 sig ud for den punkterede cirkel 19. Åbningen og lukningen af passagerne gennem de to sæt huller 17 og 18 styres ved at ændre rotati-20 onsretningen af boret. I den ene rotationsretning er tilstrømningen af boremedium til de indefter imod lysningen i boret rettede dyser afspærret, og bores der med denne rotationsretning opbygges der i det indre af boret en kerne af det materiale, som boret trænger frem i. Denne kerne kan op-25 tages enten sammen med boret eller ved, at borets rotationsretning ændres, hvorved de radialt indefter rettede dyser forsynes med boremedium, der vil afskære kernen, som derefter under normale omstændigheder vil blive skudt op gennem borets indre ved hjælp af den strøm af boremedium, som ind-30 føres gennem ejektordyserne. Den beskrevne fremgangsmåde fordrer ved anvendelse af luft som boremedium visse forholdsregler foretaget til sikker opfangelse af borekernen, der på grund af luftens udvidelse skydes op af borerøret som et projektil.FIG. 2 shows a configuration of the dividing surface 9 on the front part of the drill shaft. The interface includes a set of keyhole-shaped openings 10 which serve to receive a corresponding set of pins 11 located on the end surface 12 (FIG. 3) of the drill shaft cooperating with the interface 9 (Fig. 3). The pins 11 have a head 14 / which can just pass through the extended portion 15 of the apertures 10. After insertion into the apertures 10, the tabs in the narrow portion of the apertures 10 are locked by means of 5 set screws 16. The tabs 11 cannot pass past the screws into the extended portion and the two parts of the drill are thereby securely bonded together. The interface 9 further contains some holes 17 which are connected to channels which supply them with drilling medium inwardly directed towards the interior of the drill. These 10 holes 17 are positioned next to holes 18 in the end surface 12 in such a way that holes 17 and 18 are aligned in the angular position that the two parts occupy when the pins are at one end of the keyhole-shaped openings, and offset so much relative to each other that there is no passage when the pins 11 are in the location defined by the set screws 16. In the position in which the nozzles directed towards the illumination are closed, the hole 18 is out for the dotted circle 19. The opening and closing of the passages through the two sets of holes 17 and 18 is controlled by changing the direction of rotation of the drill. In one direction of rotation, the inflow of drilling medium to the nozzles directed towards the hole in the drill is blocked and drilled with this direction of rotation builds in the interior of the drill a core of the material into which the drill penetrates. is taken either with the drill or by changing the direction of rotation of the drill, thereby providing the radially inwardly directed nozzles with drilling medium which will cut off the core, which will then under normal circumstances be shot up through the interior of the drill by the flow of drilling medium which -30 is passed through the ejector nozzles. The described method requires the use of air as a drilling medium to take certain precautions to safely capture the drill core, which due to the expansion of the air is pushed up by the drill pipe as a projectile.

35 Som et alternativ til den på fig. 2 og 3 viste ud formning, hvor de to i forhold til hinanden drejelige dele er i kontakt med hinanden langs en flade, der forløber vinkelret på borets akse, kan kontaktfladen også have andre ud- DK 169043 B1 6 formninger. Især kan kontaktfladen omfatte et eller flere cylindriske eller koniske afsnit, der kan styre de to dele radialt i forhold til hinanden. Ved udformningen af kontaktfladen med et cylindrisk afsnit bortfalder behovet for 5 de nøglehulsformede åbninger, idet de to dele kan sammenlåses ved hjælp af en eller flere radialt forløbende tappe, som er forskydelige i aflange huller, der strækker sig rundt langs en del af omkredsen på den anden del. Ventilfunktionen sikres på tilsvarende måde gennem åbninger eller udtagnin-10 ger, som flugter med hinanden i en af vinkelstillingerne, og som i den anden er forskudt så meget i forhold til hinanden, at der ikke er passage mellem hullerne. I begge vinkelstillingerne skal der være passage gennem visse af hulparrene, der er forbundet med de i endevæggen placerede dyser, som 15 udsender tilnærmelsesvis aksialt rettede stråler af boremedium i mellemrummene mellem hårdtmetalplatterne. Disse huller kan have en passende aflang form, som sikrer, at der i begge stilliger er et passende gennemstrømningstværsnit, eller eventuelt kan de være således udformet, at gennemstrøm-20 ningstværsnittet er mindst, når de øvrige dyser er afspærret, og der er størst tryk til rådighed til overvindelse af strømningsmodstanden.35 As an alternative to the one shown in FIG. 2 and 3, in which the two rotatable parts are in contact with each other along a surface extending perpendicular to the axis of the drill, the contact surface may also have other shapes. In particular, the contact surface may comprise one or more cylindrical or tapered sections which can control the two parts radially with respect to each other. In designing the contact surface with a cylindrical section, the need for the keyhole shaped apertures lapses, the two parts being interlocked by one or more radially extending pins which are displaceable in elongate holes extending around a portion of the circumference of the Part II. The valve function is similarly ensured through openings or recesses which align with one another in one of the angular positions and which in the other are displaced so much in relation to each other that there is no passage between the holes. In both angular positions, there must be passage through some of the hollow pairs connected to the nozzles located in the end wall which emit approximately axially directed jets of drilling medium into the spaces between the cemented carbide plates. These holes may be of an appropriate oblong shape which ensures that in both positions there is an appropriate flow cross-section, or, optionally, they may be designed such that the flow cross-section is at least when the other nozzles are shut off and there is maximum pressure. available for overcoming the flow resistance.

Claims (3)

1. Jordbor især til boring af huller fortrinsvis i jord, 5 som i det væsentlige består af moræneaflejringer eller forholdsvis bløde bjergarter, hvilket bor omfatter et borerør med en borekrone, hvor borerøret er opbygget af to koncentriske rør (2,3), mellem hvilke et boremedium såsom vand eller luft kan indføres, og på hvilket borerør borekronen er 10 anbragt på dets under boringen forreste ende, idet borekronen omfatter et antal hårdtmetalplatter (5) og mellem disse placerede dyser (6), gennem hvilke boremediet udledes under tryk, kendetegnet ved, at det indre af de koncentriske 15 rør (3) har fri lysning, at der ud over dyserne (6) i borekronen er et antal radialt indefter rettede dyser (7) i kort afstand fra borekronen og et antal ejektordyser (8), som er rettet skråt indefter i retning bort fra borekronen.An earth drill, in particular for drilling holes, preferably in soil, 5 consisting essentially of moraine deposits or relatively soft rocks, comprising a drill pipe having a drill bit, the drill pipe being composed of two concentric tubes (2,3), between which a drilling medium such as water or air may be introduced and on which the drill bit 10 is positioned on its forward end under the bore, the drill bit comprising a plurality of cemented metal plates (5) and between these nozzles (6) through which the drilling medium is discharged under pressure, characterized in that the interior of the concentric tubes (3) is free of light, that in addition to the nozzles (6) in the drill bit, there are a number of radially inwardly directed nozzles (7) at a short distance from the drill bit and a number of ejector nozzles (8), which is directed obliquely inwards in a direction away from the drill bit. 2. Jordbor ifølge krav 1, 20 kendetegnet ved, at borerøret omfatter to i forlængelse af hinanden i en forudbestemt vinkel drejelige rørstykker, der er forsynet med samleflader (9,12), der i den ene af vinkelstillingerne afbryder tilførslen af boremedium til visse af dyserne og i den anden af stillingerne la-25 der forbindelsen være åben.Earth drill according to Claim 1, 20, characterized in that the drill pipe comprises two extension tubes, which are rotatable at a predetermined angle, provided with connecting surfaces (9, 12) which interrupt in one of the angular positions the supply of drilling medium to some of the the nozzles and in the other of the positions the connection is left open. 3. Jordbor ifølge krav 2, kendetegnet ved, at tilførslen af boremedium i den ene af stillingerne er afbrudt til både ejektordyserne (8) og de radialt rettede dyser (7). 30Ground drill according to claim 2, characterized in that the supply of drilling medium in one of the positions is interrupted for both the ejector nozzles (8) and the radially directed nozzles (7). 30