DEVICE FOR PRUDENT PENETRATION OF A CASING THROUGH SENSIBLE OVERBURDEN OR SENSIBLE STRUCTURES

Abstract: The present invention relates to a method and a device for driving down casings (2) through sensible overburden or sensible structures, making use of a drilling device (1) activated by compressed air that at the lower part of the drilling device (1) is led through exhaust channels (14, 142) in such a way that the major part (B) of the compressed air flow is directed upwards to be led away between the casing (2) and the drill stem together with the cuttings and a minor part (D) of the compressed air being fed to the drill bit. The characterizing feature for the invention is that the compressed air in the exhaust channels (14, 142) is control­ led in order to adapt the intensity of the compressed air flow to the material that is penetrated. The compressed air (D) fed to the drill bit is led away through jet action from the major part (B) of the compressed air.

Description: The present invention relates to a device for penetrating a casing through sensible overburden. Sensible overburden is for instance cultural layers from earlier civilizations that can be found under the ground surface having a thickness of up to 3 m. The cultural layers are a source of knowledge for the acheologist to learn about life and human beings during earlier epoches. The cultural layers are in some countries protected by law and must not be ruined. Sensible structures are for instance walls of unhewn stone for older buildings, especially while works are going on for reinforcing the fundament or sheet piling in or adjacent to the structures. These works must be carried out very carefully if no permanent damage shall occur. From SE-C-8301718-6 there are known a method and device for penetrating a casing through sensible overburden of the type specified above. However, said prior art cannot adapt the intensity of the air that is directed downwards for flushing around the drill tip. Thus, when using the method and device according to SE-C-8301718-6 certain types of soil, e.g. sand, will erode too much in the area of the drill tip. This can lead to permanent damages of a sensible overburden and subsidences of buildings can also occur. The characteristics of the invention can be found in the appending claims and are explained more in detail in the following. The main characteristics of the invention are that a drilling device that is operated by compressed air is surrounded by a casing, said drilling device at its lower end being provided with adjustable exhaust channels that direct the major part of the compressed air upwards to lead it away between the drill stem and the casing together with the cuttings. Due to the fact that the exhaust channels are adjustable the intensity of the downwards towards the drill bit directed part of the compressed air can be adapted to the nature of the material that is penetrated. By jet action said part of the compressed air can be led upwards along the grooves on the side walls of the drill bit. The invention also relates to the design of these grooves having a lower narrow inlet and an upwards continuously increasing area. Said design makes it impossible for the cuttings to stick on their way upwards. A preferable embodiment of the invention is described in the following with reference to the enclosed drawings where Fig. 1 discloses a longitudinal section of the device according to the invention; Figs. 1A-1E disclose sections along A, B, C, D and E in Fig. 1; Fig. 2 is a view corresponding to Fig. 1 showing the flowing of the compressed air; Fig. 3 illustrates schematically the different working phases when piling in a sensible overburden; and Figs. 4A-4D illustrate schematically the different working phases when piling sensible fundaments for reinforcing buildings. Figure 1 discloses in section a device for overburden drilling comprising a rotating drill 1, that is surrounded by a casing 2. The lower part of the drill, i.e. the drill bit, is shown in the figures as a separate detail. The drill bit is assembled of a guiding device 11, reamer 12 and pilot bit 13. The drill also comprises an exhaust channel 14 for the compressed air operating the drill. These details are known per se. According to the invention the exhaust channel 14 is provided with a control valve 141, that opens and closes for the passing compressed air in response to increasing and decreasing resp. counter pressure from the soil in the area of the pilot bit. Above this control valve 141 there are exhaust channels 142 for the main part of the compressed air, said exhaust channels 142 being provided with valves 143 having passages whose areas are adapted to the material that the device is to penetrate. The valves 143 are accessible for exchange in order to carry out a coarse adjustment, if necessary, before starting a new drilling cycle. The minor part of the compressed air, that passes through the control valve 141 for prudent flushing around the drill tip, thereafter is sucked upwards along grooves 144 on the side walls of the drill bit through jet action from the compressed air that is rushing out directed upwards from the exhaust channels 142 through the valves 143. By having the grooves 144 designed with a narrow lower inlet and a gradually upwards increasing area, the cuttings can never stick anywhere on their way upwards and obstruct the channels. Fig. 2 discloses in section the way of the compressed air through the drill. The compressed air is with great power rushing through the exhaust channel 14 (arrow 4) and is to a major extent pushed backwards by the constriction in the control valve 141. The air then continues through the upwards inclined exhaust channels 142 having valves 143 (arrow B) and then further upwards together with the cuttings between the drill shank and the casing (arrow C). The minor part of the compressed air, that flows through the control valve 141 (arrow D) for prudent flushing around the drill tip, is sucked upwards along the grooves 144 in the side walls of the drill bit (arrow E) through jet action from the compressed air that is rushing out in an upward direction from the exhaust channels 142 through the valves 143. Fig. 3 discloses the different working phases when the casing and the drill is driven down into the overburden to a level just below the lower edge of the cultural layer. After the drill has been drawn up piling can take place through the casing without disturbing the cultured layer. Phase 1 Mobile drill tower with casing 2 and drill 1 mounted, the tower being moved to the place is for drilling. Phase 2 The casing 2 is displayed downwards into the overburden through the cultured layers. Phase 3 The casing 2 is driven down in the overburden to a level just below the lower edge of the cultural layers. Phase 4 A pile 16 is lowered into the casing. Phase 5 The pile 16 is driven down into the overburden to a predetermined depth. Phase 6 The pile 16 has reacted the predetermined depth (driven to a stop in friction material) and then concreted 18 in the casing. Fig. 4A to 4D discloses the different working phases when the casing and the drill are driven down through a fundament of unhewn stone. Phase 1 (Fig. 4A) When the fundament 19 has been reinforced in certain areas 20 the drilling device can be entered on the floor above the base fundament. Phase 2 (Fig. 4B) Casings 2 are driven through the fundament 19 down to a level just below the lower edge of the fundament 19. Phase 3 (Fig. 4C) Steel piles 21 are driven down through the casings 2 until the end 22 of the piles 21 bear against the rock. Phase 4 (Fig. 4D) After the steel piles have been driven down to a stop the drilling device is taken away. The damages of the fundament caused by the drilling are filled with concrete 23. The invention is of course not restricted to the above described embodiments but many modifications are possible within the scope of the appending claims.

Claims: Device for penetrating casings (2) through sensible overburden or sensible structures, comprising a drilling device rotating in a casing and operated by compressed air, said device comprising a drill bit (11, 12, 13) having exhaust channels (14, 142) that direct a major part (B) of the compressed air upwards in order to lead it away between the casing (2) and the drill stem together with the cuttings, and that a minor part (D) of the compressed air is directed downwards for flushing around the drill tip, the last-mentioned part being sucked upwards along the side walls of the drill bit by jet action from the major part of the compressed air flow, characterized in that the exhaust channels have means in the form of valves (141 and/or 143) for controlling the compressed air flow in order to adapt the intensity of the compressed air flow, directed towards the drill bit, to the nature of the material that is penetrated. Device according to claim 3, characterized in that the exhaust channel/ channels for the major part of the pressure medium flow has/have valves (143) with adjustable passing area. Device according to claim 3 or 4, characterized in that the control valves (143) are exchangeable. Device according to claim 3 or 4, characterized in that the exhaust channel receiving the minor part (D) of the compressed air flow has a control valve (141) being so designed that its passing area increases and decreases in response to increasing and decreasing resp. counter pressure from the soil adjacent the drill bit. Device according to any one of claims 3 - 6, characterized in vertical discharge grooves (144) receiving the minor part (D) of the compressed air

Inventors: ANDERSSON, SVEN-GOERAN, BJERKING, SVEN-ERIK, Andersson, Sven-Göran
Applicants: AB SANDVIK ROCK TOOLS
Application year: 1986
Main classification: E02D7
IPC codes: E21B21, E02D27, E02D5, E02D7