WO2010084238A1

WO2010084238A1 - Method and apparatus for down-the-hole drilling

Info

Publication number: WO2010084238A1
Application number: PCT/FI2009/050860
Authority: WO
Inventors: Jukka Ahonen
Original assignee: Atlas Copco Rotex Oy AB
Current assignee: Tercope Finland Oy
Priority date: 2009-01-21
Filing date: 2009-10-27
Publication date: 2010-07-29
Anticipated expiration: 2011-07-21
Also published as: CA2737279C; NO2382368T3; US20110278069A1; US8857537B2; CL2011001761A1; FIU20090398U0; CA2737279A1; FI8617U1; EP2382368A4; EP2382368B1; JP2012515866A; JP5629271B2; EP2382368A1; FI20095046A0

Abstract

The invention relates to a method and apparatus for down-the- hole drilling, the drilling being carried out by an apparatus, having a drilling device (1) that comprises a casing part (2) and an essentially inside thereof existing drilling unit (3), at the drilling head of which there are at least first drilling means (4) for drilling a centre hole, second drilling means (5) for reaming the centre hole for the casing part (2) and a flushing flow arrangement (6) that comprises first flushing means (6a) for leading of a flushing medium onto a drilling surface (P) and second flushing means (6b) for returning of the flushing medium and drilling waste at least partly internally inside the casing part (2). The first drilling means (4) are removably coupled with the second drilling means (5) in order to enable removal thereof from the hole. The casing part (2) is arranged to be drawn into a hole to be drilled by the drilling unit (3). The flushing medium is being brought onto the drilling surface (P) and returned therefrom by axially directed (s) flow arrangements (6a; 6a', 6b; 6b'), disposed in a cross-section view, on an outer periphery of the first drilling means (4) and/or in an inner periphery of the second drilling means (5).

Description

Method and apparatus for down-the-hole drilling

The invention relates to a method and apparatus for down-the-hole drilling according to the preambles of the independent claims.

For example in patent publication FI 75650 there has been presented a boring tool, which is meant for boring and/or hammer drilling, to be used in connection with a drill rod unit placed inside a mantle pipe. The boring tool to be attached at the front end of the drill rod unit has a center drill, being provided with a cutting unit, and an eccentric reaming drill, being placed after the center drill, the reaming drill having also a cutting unit. The reaming drill moves with respect to the center drill between a drilling position, in which it is positioned sidewards in front of the mantle pipe, and a return position, in which it is withdrawn in radial direction inside the mantle pipe. Deviating from earlier solutions, in which the center drill is in most cases provided with four cutting parts directed radially and being made of hard metal, the reamer for its part comprising either one or two radially directed cutting parts made of hard metal, in the solution according to the publication in question, the cutting parts are replaced by bit parts being arranged in a certain manner. With the solution presented in this publication such constructions of the center drill and the reaming drill have been aimed that the operating time of the boring tool will be as long as possible.

A way to carry out overburden drilling in a more developed manner compared to prior art, is formerly known e.g. from Finnish Patent No. 95618. The drilling head of the drilling unit of the drilling apparatus existing inside a casing part or in other words a so called casing pipe according to this patent, is formed of a first frame part and an annular second frame part, in the drilling surfaces of which there has been arranged drilling organs, such as drill bits or like, of the first and second drilling means or in other words of the pilot and the reamer. In this solution the first drilling means that is the first frame part forming the pilot, is being released from the second frame part forming the reamer in order to pull the same alone off from a drilled hole after the drilling situation. In the solution in question the second organs of the flushing means for removal of drilling waste being generated are arranged to lead drilling waste by means of an assembly belonging to the counterpart surface arrangement, which connects the said drilling means together for a drilling situation unrotatively in respect with each other and in both directions longitudinally, which, in other words, is being carried out as an advantageous embodiment by loosening grooves, belonging to a bayonet coupling, placed longitudinally in the outer periphery of the first frame part.

Particularly a so called pile drilling has rapidly become common in making of both so called micro piles and large-diameter foundation piles. An advantage of pile drilling is among other things the fact that drilled piles can be mounted quickly and accurately in a desired position, direction and depth. Straightness of the piles, verification of the bottom and accurate positioning are factors, thanks to which the pile drilling has often taken the place of pile driving particularly in demanding construction sites. A drilled pile displaces a corresponding amount of soil to its volume by bringing up the drilled soil entirely. This is why not any horizontal strains will be caused that might brake surrounding structures, which may take place when piles are rammed. Pile drilling is also relatively silent and quite shakeless (the operating frequency of the hammer is higher than the natural frequencies of soil and structures) when compared to piles being rammed. On the other hand the possibility offered by a drilled pile to get a casing pipe mounted reliably and without efforts even into a sloping rock surface, are superiority factors when comparing the method to piling by digging.

Thus a significant number of superiority factors are related to pile drilling, which in practice very often make the same as the most recommendable alternative. Thanks to the pile drilling being the most efficient piling method also by its production capacity and due to the fact that it enables piling with relatively small, easily transportable, and space-saving machines that can be put quickly into working order, also foundation constructors almost without exception take up a positive attitude towards the same.

Pile drilling uses pressurized air for operating the down-the-hole hammer and as the means for bringing up the loosened material. Careless use of air in flushing has brought about, however, some problems, solving of which is necessary for the standpoint of development regarding pile drilling.

Problems caused by flushing air can be devided in two main categories:

- Use of flushing air may overdrill an excessive amount of material on surface of the earth, in which case both the foundation to be built and surrounding structures are in danger. This is a typical situation particularly with frictional soil (sand, silt etc.),

- The second problem is due to "pushing" of air into the soil particularly in case of cohesive soil (such as clay) , whereby air may get drifted around load supporting piles (e.g. rammed wood piles) existing in the neighbourhood, in which case weight carrying capacity of the pile (or piles) may decrease very quickly.

Careless use of flushing air has already led to denial of pile drilling by a down-the-hole hammer among other things in some sites, which have been grounded on support of old wood piles driven in cohesive soil, in which case air that has been "escaped" into the soil has caused sudden sinkings and cracks in buildings. On the other hand in some sites, a significantly greater amount of soil has been over drilled by flushing air than the piles have actually replaced, due to which surrounding buildings have been caused to tilt.

Because down-the-hole hammer drilling is, however, a very efficient way to operate, applicable for all soil circumstances and because the piles erected by the same are straight and reliable, the disadvantages related to its use need to be eliminated in order to enable down- the-hole hammer drilling also in the future.

As stated above, the problems caused by the use of flushing air in down-the-hole hammer drilling are usually due to poor professional skill or carelessness of the operating personnel, but in practice also drill bit structures and drilling techniques may effect essentially to arising of the problems. In this context e.g. drill bits are originally designed usually for rock drilling, whereby the flushing air must first of all be directed as efficiently as possible to the drilled point for removing of the particles quickly in order to avoid multiple crushing, and on the other hand with such a volume (and speed) , that the material gets brought up through the casing. This is why the flushing openings of the drill bits are thus aimed directly at the rock surface. During drilling the flushing air may not get back upwards in rock hole, but along a hole with unbroken walls. The situation is, however, different in overburden drilling, whereby the ground may penetrate air even very easily. In this case turning of the flushing air back to the casing pipe or in connection therewith is very problematic or even impossible, if carried out by traditional drill bits. On the other hand, a large amount of air is needed for lifting of the soil, which leads also to a high velocity inside the casing pipe and to very effective blowing of flushing air directly to the soil.

Thus a very controlled circulation of flushing medium is reguired particularly in pile drilling, but correspondingly also in any other type of down-the-hole drilling, in which liquid, such as water is being used as flushing medium, so that the flushing medium is mainly returned back on the surface of the earth through the casing pipe, though the soil would be relatively loose. The drilling action must be performed on the other hand in a space protected as well as possible so that the pressure of the ground does not block input openings of the flushing medium or in other words so that the pressure of the flushing medium to be fed exceeds the pressure of the ground and on the other hand so that the easiest way for flushing medium from the drilled point takes place in a desired manner back to the casing pipe.

It is an aim of the method and apparatus according to the present invention to achieve a decisive improvement in the problems described above and thus to raise essentially the level of prior art. In order to carry out this aim, the method and apparatus according to the invention are mainly characterized by what has been presented in the characterizing parts of the independent claims related thereto. As the most important advantages of the method and apparatus according to the invention may be mentioned simplicity and efficiency of the constructions and operating principles enabled by the same first of all thanks to the fact that it is possible to exploit therewith drill bit constructions that have already been found technically very well functionable. The invention enables extremely simple first drilling means or pilot regarding construction thereof particularly thanks to the fact that the flushing medium is both brought to the drilling surface and removed therefrom together with the drilling waste through a space between the pilot and the reamer, in which case a flushing flow is achieved that circulates very efficiently over the head of the pilot. On the other hand by providing the drilling head with a guide surface arrangement that controls passage of the flushing medium, drifting of the flushing medium to the drilling surface can be secured by simultaneously preventing entering thereof to a return flow channel prior to drifting thereof onto the drilling surface.

On the other hand, the invention enables further use of pressurized air as the flushing medium by providing the drilling head of the drilling unit when needed with a counterpart surface arrangement, which directs passage of the pressurized air flow so, that it may not get directed to the soil. By virtue of the above among other things overdrilling and foundations of surrounding structures getting damaged can be avoided, which is nowadays being tried to prevent when drilling by present technique e.g. by protective pilings limiting the drilling site, which become naturally disproportionately expensive. With the method and apparatus according to the invention, bringing about an improvement of safety, it is thus possible to achieve also clear savings in performing of the drilling itself. Advantageous embodiments of the method and apparatus according to the invention have been presented in the dependent claims related thereto.

In the following description the invention is depicted in detail with reference to the appended drawings, in which

in figure 1 is shown a partial longitudinal cross- sectional view from a drilling device construction presenting prior art,

in figures 2a and 2b are shown a partial longitudinal cross- sectional view from a drilling head of an advantageous drilling device applying the method according to the invention and a flushing medium flow taking place in connection therewith, and a front view as seen from the side of the drilling device's drilling surface,

in figure 3 is shown a longitudinal cross-sectional view from an advantageous drilling device belonging to the apparatus applying the method according to the invention, and

in figure 4 is shown an alternative or complementing implementation with respect to the one shown in figure 3.

The invention relates to a method for down-the-hole drilling, the drilling being carried out by an apparatus, having a drilling device 1 that comprises a casing part 2 and at least during a drilling situation an essentially inside thereof existing drilling unit 3, at a drilling head of which there are at least first drilling means 4 for drilling a center hole, second drilling means 5 for reaming the center hole for the casing part 2 and a flushing flow arrangement 6, which comprises first flushing means 6a for leading of a flushing medium onto a drilling surface P and second flushing means 6b for returning of the flushing medium and drilling waste at least partly internally inside the casing part 2. The first drilling means 4 are coupled with the second drilling means 5 first of all power-transmittedly in order to carry out cooperation thereof at least during a drilling situation with the second drilling means 5 for a rotational motion w4, an axial s feeding motion z4 and/or a hammering motion t4, and on the other hand removably in order to enable removal thereof from the hole. The casing part 2 is arranged to be drawn into a hole to be drilled by the drilling unit 3 e.g. by applying a casing shoe 8. The flushing medium is being brought onto the drilling surface P and returned from the drilling surface P together with the drilling waste by axially directed flow arrangements 6a; 6a', 6b; 6b' that exist, when viewed in a cross section, on an outer periphery of the first drilling means 4 and/or in an inner periphery of the second drilling means 5.

The method is being exploited advantageously when operating with a drilling apparatus, in which the drilling head of the drilling device 1 is formed e.g. as shown in figures 2a, 3 and 4 of a first frame part 4a and a second frame part 5a, the drilling surfaces P; Pl, P2 of which being provided with drilling organs of the first and the second drilling means 4, 5, such as an integrated drilling part, separate drilling pieces, bits or like, and whereby a rotationally symmetrical reamer is being used as the second drilling means 5 that has an essentially continuing drilling surface radially, when viewed in a cross-section perpendicular to a longitudinal direction s of the drilling unit 3. In this context e.g. according to the longitudinal cross-sectional views shown in figures 1, 2a, 3 and 4 and the front view shown in figure 2b, at least the second flushing means 6; 6b of the flushing flow arrangement for returning of the flushing medium and the drilling waste at least partly internally inside the casing part 2 is arranged by one or several axially s directed return flow channels 6b' , being placed between the first and the second drilling means 4, 5, such as the first and the second frame parts 4a, 5a. The flushing medium is being led from a feed channel 6al, being led advantageously centrically to the first drilling means 4, such as the first frame part 4a, by one or several distribution channels 6a2 directed outward therefrom into a feed flow channel 6a' on the outer periphery of the first drilling means 4, such as the first frame part 4a, at a distance e from the drilling surface Pl of the first drilling means. Thus, as manifested e.g. in figure 2b, a part of the flow arrangements between the drilling means 4, 5 being used as a feed flow arrangement 6a' for the flushing medium.

Furthermore as an advantageous embodiment of the method, passage of the flushing medium onto the drilling surface P is guided at the drilling head of the drilling unit 3, e.g. as shown in figures 2a, 3 and 4, by a guide surface arrangement X existing advantageously in the first frame part 4a forming the first drilling means 4 or the pilot.

By means of the guide surface arrangement X in question, returning of a feed flow of the flushing medium from the feed flow channel 6a' to the return flow space 6bl is prevented prior to drifting thereof onto the drilling surface P, in which case circulation of the flushing medium is secured as shown in figure 2a "over" the end of the pilot. Furthermore as shown in figures 2a, 3 and 4 it is in this case thus possible to optimize the flow channels in a way that the cross- sectional area of the feed flow channel 6a' is increased when getting closer to the drilling surface by an inclined bottom surface bs of the flow channel 6a' , in which case simultaneously speed of the flushing medium decreases. Furthermore on the principle disclosed in figure 2b, when bringing the flushing medium to the drilling surface P e.g. by one feed flow channel 6a' , it is possible to make sure efficient removal of flushing medium and drilling waste from the drilling surface P by exploiting two axially directed return flow channels 6b' between the pilot 4 and the reamer 5.

Furthermore with reference particularly to the advantageous embodiment shown in figure 4, direction of the flushing medium feed flow is altered by means of a counterpart surface arrangement y essentially in connection with the drilling surface P particularly in order to decrease drifting thereof into the soil by decreasing its kinetic energy. When carried out in this way, it is possible to efficiently prevent drifting of the flushing medium into the soil, when it collides first of all with the inner surface of the reamer 5 while entering the axially directed feed flow channel 6a' and a second time with an inward oblique end y of the reamer while being guided from the end of the pilot 4 onto the drilling surface.

Furthermore as an advantageous embodiment, it is possible to exploit the flushing medium in a way that by means thereof the return flow is partially made more effective by one or several circulation flow channels 6ab as shown in figures 2a, 3 and 4. The invention relates also to an apparatus for down- the-hole drilling, which comprises a drilling device 1 as described above. Particularly with reference to the advantageous embodiments shown in figures 2a, 2b, 3 and 4, the flushing flow arrangement 6 comprises axially directed s flow arrangements 6a; 6a', 6b; 6b', both for bringing of the flushing medium onto the drilling surface P and for returning thereof from the drilling surface P together with the drilling waste, the arrangements existing, when viewed in a cross-section, on an outer periphery of the first drilling means 4 and/or an inner periphery of the second drilling means 5.

Furthermore as an advantageous embodiment with reference to the longitudinal cross-sectional views, shown in figures 2a, 3 and 4, the first means 6a of the flushing flow arrangement 6 comprise a feed channel 6al, being led centrically to the first drilling means 4, such as the first frame part 4a, and one or several distribution channels 6a2, being led outward therefrom, in order to lead the flushing medium into a feed flow channel 6a' on the outer periphery of the first drilling means 4, such as the first frame part 4a, at a distance e from the drilling surface Pl of the first drilling means.

Furthermore as an advantageous embodiment, the flushing flow arrangement 6 comprises a guide surface arrangement X for guiding passage of the flushing medium onto the drilling surface P at the drilling head of the drilling unit 3. The guide surface arrangement X in question is arranged to prevent returning of the flushing medium feed flow from the feed flow channel 6a' to the return flow space 6bl prior to drifting thereof onto the drilling surface P. Furthermore as an advantageous embodiment particularly with reference to figure 4, the flushing flow arrangement 6 comprises a counterpart surface arrangement y for changing direction of the flushing medium feed flow essentially in connection with the drilling surface P particularly in order to decrease drifting thereof into the soil by decreasing its kinetic energy.

It is clear that the invention is not limited to the embodiments presented or described above, but instead it can be modified within the basic idea of the invention according to the needs at any given time. It is thus clear that the constructions of the drilling heads being illustrated in the appended drawings may vary in practice very much merely when being carried out with differing diameters. Instead of the type of embodiments shown in the appended drawings, it is naturally possible to use as the drilling device also other drilling devices that are applicable for the same purpose, in which a casing part is being exploited in connection with the drilling so that is most advantageously not rotated when being drawn into the ground. It is not that significant for the method and the apparatus according to the invention, either, how the first and second drilling means are coupled to work, so that most heterogeneous solutions can be exploited as the power transmission assemblies between the same starting from a screw joint locking. Also the casing shoe can be placed in an integrated manner at the end of the casing part etc.

Claims

Claims :

1. Method for down-the-hole drilling, the drilling being carried out by an apparatus, having a drilling device (1) that comprises a casing part (2) and at least during a drilling situation an essentially inside thereof existing drilling unit (3), at a drilling head of which there are at least first drilling means (4) for drilling a center hole, second drilling means (5) for reaming the center hole for the casing part (2) and a flushing flow arrangement (6) for leading of a flushing medium onto a drilling surface (P) and for returning of drilling waste at least partly internally inside the casing part (2), whereby the first drilling means (4) are coupled with the second drilling means (5) first of all power-transmittedly in order to carry out cooperation thereof at least during a drilling situation with the second drilling means (5) for a rotational motion (w4), a feeding motion (z4) and/or a hammering motion (t4), and on the other hand removably in order to enable removal thereof from the hole, and whereby the casing part (2) is arranged to be drawn into a hole to be drilled by the drilling unit (3), characterized in that the flushing medium is being brought by first flushing means (6a) of the flushing flow arrangement (6) onto the drilling surface (P) and returned from the drilling surface (P) together with the drilling waste by second flushing means (6b) of the flushing flow arrangement. (6) through axially directed (s) and in respect with each other separate feed flow (6a') and return flow (6b') channels that exist, when viewed in a cross section, on an outer periphery of the first drilling means (4) and/or an inner periphery of the second drilling means (5) .

2. Method according to claim 1 when operating with a drilling apparatus, in which the drilling head of the drilling device (1) is formed of a first frame part (4a) and a second frame part (5a), the drilling surfaces (P; Pl, P2) of which being provided with drilling organs of the first and the second drilling means (4, 5), such as an integrated drilling part, separate drilling pieces, bits or like, whereby a rotationally symmetrical reamer is being used as the second drilling means (5) that has an essentially continuing drilling surface radially, when viewed in a cross-section perpendicular to a longitudinal direction (s) of the drilling unit (3), whereby at least the second flushing means (6; 6b) of the flushing flow arrangement for returning of the flushing medium and the drilling waste are arranged by one or several axially directed (s) return flow channels (6b') existing between the first and the second drilling means (4, 5), such as the first and the second frame parts (4a, 5a), and whereby the flushing medium is being led from a feed channel (6al), being led centrically to the first drilling means (4), such as the first frame part (4a), by one or several distribution channels (6a2) directed outward therefrom into a feed flow channel (6a') on the outer periphery of the first drilling means (4), such as the first frame part (4a), at a distance (e) from the drilling surface (Pl) of the first drilling means, characterized in that passage of the flushing medium onto the drilling surface (P) is guided by a guide surface arrangement (X) existing at the drilling head of the drilling unit (3), such as in connection with the first and/or the second drilling means (4, 5), by means of which returning of the flushing medium feed flow from the feed flow channel (6a') to the return flow space (6bl) is prevented prior to drifting thereof onto the drilling surface (P) .

3. Method according to claim 1 or 2, characterized in that direction of the flushing medium feed flow is altered by a counterpart surface arrangement (y) essentially in connection with the drilling surface (P) particularly in order to decrease drifting thereof into the soil by decreasing its kinetic energy.

4. Apparatus for down-the-hole drilling having a drilling device (1) that comprises a casing part (2) and at least during a drilling situation an essentially inside thereof existing drilling unit (3), at a drilling head of which there are at least first drilling means (4) for drilling a center hole, second drilling means (5) for reaming the center hole for the casing part (2) and a flushing flow arrangement (6) for leading of a flushing medium onto a drilling surface (P) and for returning of drilling waste at least partly internally inside the casing part (2), whereby the first drilling means (4) are coupled with the second drilling means (5) first of all power-transmittedly in order to carry out cooperation thereof at least during a drilling situation with the second drilling means (5) for a rotational motion (w4), a feeding motion (z4) and/or a hammering motion (t4), and on the other hand removably in order to enable removal thereof from the hole, and whereby the casing part (2) is arranged to be drawn into a hole to be drilled by the drilling unit (3), characterized in that the flushing flow arrangement (6) comprises axially directed (s) and in respect with each other separate feed flow (6a' ) and return flow (βb') channels both for bringing of the flushing medium onto the drilling surface (P) by means of the first flushing means (6a) of the flushing flow arrangement and returning thereof from the drilling surface (P) together with the drilling waste by means of second flushing means (6b) of the flushing flow arrangement, the channels existing, when viewed in a cross-section, on an outer periphery of the first drilling means (4) and/or an inner periphery of the second drilling means (5) .

5. Apparatus according to claim 4, in which the drilling head of the drilling device (1) is formed of a first frame part (4a) and a second frame part (5a), the drilling surfaces (P; Pl, P2) of which being provided with drilling organs of the first and the second drilling means (4, 5), such as an integrated drilling part, separate drilling pieces, bits or like, whereby a rotationally symmetrical reamer is being used as the second drilling means (5) that has an essentially continuing drilling surface radially, when viewed in a cross-section perpendicular to a longitudinal direction (s) of the drilling unit (3), whereby at least the second flushing means (6; 6b) of the flushing flow arrangement for returning of the flushing medium and the drilling waste are arranged by one or several axially directed (s) return flow channels (6b') existing between the first and the second drilling means (4, 5), such as the first and the second frame part (4a, 5a) , and whereby the first flushing means (6a) of the flushing flow arrangement (6) comprise a feed channel (6al), being led centrically to the first drilling means (4), such as the first frame part (4a), and one or several distribution channels (6a2), being directed outward therefrom, in order to lead the flushing medium into a feed flow channel (6a') on the outer periphery of the first drilling means (4), such as the first frame part (4a), at a distance (e) from the drilling surface (Pl) of the first drilling means, characterized in that the flushing flow arrangement (6) comprises a guide surface arrangement (X) for guiding passage of the flushing medium onto the drilling surface (P) at the drilling head of the drilling unit (3), which guide surface arrangement (X) prevents returning of the flushing medium feed flow from the feed flow channel (6a') to a return flow space (6bl) prior to drifting thereof onto the drilling surface (P) .

6. Apparatus according to claim 4 or 5, characterized in that the flushing flow arrangement (6) comprises a counterpart surface arrangement (y) for altering direction of the flushing medium feed flow essentially in connection with the drilling surface (P) particularly in order to decrease drifting thereof into the soil by decreasing its kinetic energy.