The invention does not relate to any use that there may be for the kerf. In particular, the invention does not relate to a method of drilling nor to a method of forming a foundation.

BACKGROUND OF THE INVENTION In the foundation drilling industry shafts are drilled to house foundation piles for buildings, bridges and the like. US patent 6,189,630 describes techniques for drilling relatively large diameter shafts. The patent describes the use of a hollow core barrel with a plurality of hammer drills that are used to cut an annular kerf. Once the kerf is drilled to the desired depth in the ground, the core barrel is withdrawn from the kerf and the core may be removed by conventional techniques. Alternatively, the core may be left in place to form the interior portion of a structural pile. In such a construction, the drilled annular kerf may be filled with a casement or pipe and any voids subsequently filled with cement.

US patent 4,458,947 describes a deep level mining method. The patent describes drilling holes to enable the maximum possible recovery of reef. The patent describes and illustrates drilling overlapping holes.

The present invention seeks to provide an apparatus for drilling a kerf in the ground which apparatus is relatively simple in construction and operation.

SUMMARY OF THE INVENTION According to the present invention there is provided an apparatus for drilling a kerf, said apparatus including a base structure, a carriage member mounted on the base structure and a drill rig mounted on the carriage member, and wherein the carriage member is arranged so that the drill rig can be used to drill a plurality of holes which form the kerf.

Preferably, the apparatus is arranged to drill an endless kerf.

Preferably, the carriage member is arranged for movement relative to the base structure so as to enable the drill rig to be repositioned along a path that defines the kerf to be drilled. Following movement of the carriage member, a subsequent hole can be drilled relative to the first hole. The subsequent hole is arranged so as to overlap, at least in part, with the first hole.

Preferably, the apparatus is arranged so that the position of the drill rig on the carriage member can be varied so as to enable kerfs of different dimensions and orientations to be drilled.

The base structure is arranged to support the apparatus on a ground surface.

The base structure preferably includes a guide system arranged to guide the movement of the carriage member and thereby define the shape of the kerf to be drilled.

In accordance with a preferred embodiment of the invention, the carriage member includes a rotation carriage and a slide carriage. The slide carriage is arranged so that the drill rig can be mounted thereon and is connected to the rotation carriage so that rotation of the rotation carriage causes a rotation of the slide carriage.

The slide carriage is preferably further arranged so that it can move substantially horizontally to thereby enable the drill rig to be repositioned relative to a centre point of the apparatus. Repositioning of the slide carriage relative to the centre point enables the dimensions of the kerf to be varied.

Where the kerf is to be substantially circular, repositioning of the slide carriage relative to the centre point enables the radial dimension of the kerf to be varied.

The rotation carriage is mounted on the guide system of the base structure and can be indexed along the guide system by increments. The increments are determined so that there is an overlap between adjacent drilled holes. The drill rig can thus be repositioned and then used to drill a drill hole at each incremental position along the guide system so as to thereby drill the endless kerf.

Computer controlled means may be provided to control the movement of the slide carriage and/or the rotation carriage so that the desired configuration of the kerf can be achieved.

The base structure preferably further includes means for levelling the apparatus. The levelling means preferably includes a plurality of levelling jacks that form part of the base structure.

The drill rig is preferably mounted on the slide carriage so that drilling occurs at a location within a space defined by the guide system.

The guide system preferably includes a monorail structure that, in accordance with a preferred embodiment, adopts a substantially circular configuration. It will however be appreciated that the monorail structure may adopt other configurations. It will also be appreciated that the endless kerf is preferably annular, but may adopt other configurations.

Preferably, the slide carriage and the rotation carriage each include a rectangular shaped frame. The frame of the slide carriage is preferably arranged for movement relative to the frame of the rotation carriage.

Preferably, the slide carriage frame can slide relative to the rotation carriage frame or can be otherwise indexed there along.

The invention further provides a steering dolly that may be used with the drilling apparatus to guide the drilling of a kerf of a desired configuration. The steering dolly includes a front steering member and a rear steering member, a drill sleeve for guiding a drill during drilling of a hole along the path of a kerf being drilled, and wherein the drill sleeve is connected to said front steering member and is arranged so that a drill located in the drill sleeve is positioned to drill a hole that overlaps, at least in part, with a part of the previously drilled kerf.

Preferably, a joining member is connected between the front steering member and the rear steering member. The joining member is shaped so that the drill sleeve is positioned on the path of the kerf to be drilled.

The drill sleeve is preferably dimensioned so that a hammer drill or the like can pass there through and so that when the drill is hammered into the ground, the steering dolly is free to move substantially vertically along the length of the drill hole. Sufficient clearance between the periphery of the hammer drill and the inner wall of the drill sleeve is preferably provided so that drilling vibrations are not directly transferred to the steering dolly.

The spacing between the rear steering member and the front steering member is preferably variable. The rear steering member would, in one embodiment, be located at a position equivalent to three or four drill holes behind the hole being drilled. However, the desired spacing between the rear steering member and the front steering member is determined by the dimension of the kerf to be drilled. Typically, the larger the diameter of the endless kerf to be drilled the further away the rear steering member would be positioned relative to the front steering member.

The drill sleeve is preferably configured so that the steering dolly can move substantially parallel to the drill during a drilling operation.

The joining member may be an adjustable or a hinged member so as to enable the positioning of the front steering member to be adjusted relative to the rear steering member. Locking means is provided to lock the joining member in the desired angular orientation.

The front steering member is preferably tubular to enable removal means to be passed therethrough so that drilled material can be removed from the kerf as drilling takes place. The removal means may include a suction tube or other device to facilitate removal of drilled material.

The steering dolly is arranged to be supported in the kerf by at least one support cable. The support cable is arranged to be attached to an anchor.

The steering dolly is preferably arranged so that percussion effects from the hammer drill is minimised.

DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side view of a drilling apparatus in accordance with an embodiment of the invention; Figure 2 is a top view of the drilling apparatus shown in Figure 1; Figure 3 is a side view of a steering dolly in accordance with an embodiment of the invention being used to drill a kerf ; and

Figure 4 is a top view of the steering dolly shown in Figure 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 illustrates an apparatus 10 for drilling a kerf. The apparatus 10 is particularly arranged to enable drilling of an endless kerf. The apparatus 10 includes a base structure 12, a carriage member 14 and a drill rig 16. The drill rig 16 is mounted on the carriage member 14. Also mounted on the carriage member 14 is ancillary equipment 18 that may include a drill rig engine, cyclone and hydraulics, etc. The drill rig 16 includes a drill rig mast 20, a rotation head 22 and a hammer drill 24.

The base structure 12 is arranged to support the apparatus 10 on a ground surface 26. The base structure 12 includes a plurality of levelling jacks 28 which can be used to level the apparatus 10 so that a drill hole drilled by the drill rig 16 is substantially vertical.

As best illustrated in Figure 2, the base structure 12 also includes a guide system in the form of a monorail structure 30. The guide system is arranged to guide the movement of the carriage member 14. In this embodiment, the monorail structure 30 is circular in configuration and is formed from a pair of semi-circular sections 30a, 30b. The semi-circular sections 30a, 30b have flanges 32 on their respective ends so that the two sections 30a, 30b can be joined together at the flanges 32 using flange bolts 33.

As shown in Figures 1 and 2, the levelling jacks 28 are connected to the underside of the monorail structure 30 and are spaced equally thereabout so as to properly support the monorail structure 30 above the ground 26.

The carriage member 14 includes a rotation carriage 34 and a slide carriage 36.

The slide carriage 36 is arranged so that the drill rig 16 and the ancillary equipment 18 can be mounted thereon. The slide carriage 36 is connected to

the rotation carriage 34 so that rotation of the rotation carriage 34 causes rotation of the slide carriage 36. The connection between the slide carriage 36 and the rotation carriage 34 is such that upward, downward and radial thrust forces transmitted through the apparatus 10 can be accommodated. Movement of the slide carriage 36 and the rotation carriage 34 will be described in more detail subsequently.

As shown in Figures 1 and 2, the rotation carriage 34 includes a rectangular shaped rotation frame 38 that is connected at each of its longitudinal ends to the monorail structure 30. The connection between the monorail structure 30 and the frame 38 of the rotation carriage 34 is such that the rotation frame 38 can be move along the monorail structure 30 so as to cause the rotation frame 38 to rotate about a centre point 39 of the apparatus 10. It will be appreciated that the connection between the monorail structure 30 and the rotation frame 38 should accommodate any upward, downward and radial thrust forces transmitted through the apparatus 10.

The slide carriage 36 includes a substantially rectangular shaped frame 40 that is connected to the rotation frame 38 in a manner that enables the slide frame 40 to move substantially horizontally. Preferably, movement of the slide frame 40 is achieved by sliding the frame 40 along a track located in the inner longitudinal sides of the rotation frame 38. By sliding the slide frame 40 horizontally, the position of the drill 24 relative to the centre point 39 can be varied and thus, it will be appreciated, that the radius at which a bore hole can be drilled by the drill rig 16 can be correspondingly varied.

As is best illustrated in Figure 2, the drill rig 16 is mounted on the slide carriage 36 so that drilling occurs at a location within the internal space defined by the monorail system 30. It will also be appreciated that the levelling jacks 28 support the apparatus 10 at locations outside of the kerf being drilled. This is important because it prevents, or at least minimises, the possibility that the core

(i. e. the ground bounded internally by the endless kerf) will shear. It is important to maintain the stability of the core for any subsequent use.

In order to drill a continuous kerf the apparatus 10 is set up at the desired drilling location. The apparatus 10 is levelled on the ground surface 26 using the levelling jacks 28. The slide frame 40 is then slid so as to position the hammer drill 24 at the required radius from the centre point 39. Once the slide frame 40 has been properly positioned, it is locked into position and the drilling procedure can commence.

The first step in the drilling procedure is to drill a pilot hole. A hammer drill 24 is then used to drill the first hole. Once the first hole has been drilled to the desired depth, the drill 24 is retracted and then the rotation frame 34 is moved along the monorail structure 30 so as to relocate the hammer drill 24 to a subsequent drilling position. The rotation frame 34 is moved along the monorail structure 30 a sufficient distance so that when a subsequent hole is drilled it will overlap, at least in part, with the previously drilled hole. Once the subsequent hole is drilled, the hammer drill 24 is retracted and then the procedure is repeated until the rotation frame 34 has been moved along the entire length of the monorail structure 30. This enables an endless kerf to be drilled in the ground 26. A circular shaped endless kerf 45 is shown schematically in Figure 2.

It will be appreciated that mechanical or hydraulic means (not shown) may be provided to slide the slide frame 40 relative to the rotation frame 34 so as to set the positioning of the drill rig 16 relative to the centre point 39. It will also be appreciated that mechanical or hydraulic means (not shown) may be provided to rotate or index the rotation frame 34 along the monorail structure 30. Control means (not shown) may also be provided to control the indexing of the rotation frame 34 along the monorail structure 30. Control means may also be provided to control movement of the slide frame 36. In this way, control means may be used to control the configuration of the endless kerf that is drilled by the

apparatus 10. The construction of kerfs of different configuration is envisaged.

The control means may include a computer and appropriate software.

Figures 3 and 4 illustrate a steering dolly 50 that is suitable for use with the previously described apparatus 10. The steering dolly 50 helps to maintain the hammer drill 24 in the desired vertical orientation and maintain the drill 24 on the path defining the kerf to be drilled. Figure 3 illustrates schematically a kerf 45 being drilled by a hammer drill 24 that is guided by the steering dolly 50.

The steering dolly 50 includes a rear steering member 52, a drill sleeve 54, a joining member 56 and a front steering member 58. The drill sleeve 54 is arranged so that a drill 24 can pass therealong and can be used to drill a hole on the path defining the kerf. The rear steering member 52 and front steering member 58 are each formed as tubular sleeves.

In use, the rear steering member 52, joining member 56 and front steering member 58 are arranged to travel, as a hole is being drilled, vertically down a portion of a previously drilled kerf. The front steering member 58 however is arranged to travel vertically along the leading end of the kerf. The leading end of the kerf is formed by the last most hole that was drilled on the path of the kerf. The exact positioning of the rear steering member 52 relative to the front steering member 58 will depend on the length of the joining member 56. It should also be appreciated that it is possible, in some circumstances, for the rear steering member 56 to be directly connected to the front steering member 58.

The front steering member 58 is tubular and includes a sidewall portion 59 that is common with the sidewall of the drill sleeve 56. The common sidewall portion 59 is shaped so that when a drill 24 is located in the drill sleeve 54 and is used to drill a hole, that hole overlaps, at least in part, with that portion of the kerf in which the front steering member 58 is traversing. In this way, overlapping holes on the path of the kerf are drilled so as to form the kerf.

The steering dolly 50 has a vertical dimension substantially equal to the length of the hammer drill 24. This ensures that the hammer drill 24 will be properly supported and will thus maintain the correct vertical orientation of the drill.

The drill sleeve 54 is dimensioned so that a hammer drill 24 can pass there through and so that when the hammer drill 24 is hammered into the ground, the steering dolly 50 is free to move substantially vertically along the length of the drill hole. Sufficient clearance between the periphery of the hammer drill 24 and the wall of the drill sleeve 54 is also provided so that drilling vibrations are not directly transferred to the steering dolly 50.

The front steering member 58 has a lower end 58a that extends below the lower end 54a of the drill sleeve 54. Thus, when a suction tube or other device is passed through the front steering member 58, the suction device can be positioned adjacent to the drill bit 24a and below the depth of the drill bit 24a in the kerf 45. This arrangement of the lower end 58a of the front steering member 58 and the associated suction tube is illustrated in Figure 3.

Accordingly, the suction tube can be used to collect the drill cuttings as they are drilled free by the drill bit 24a. This ensures that the cuttings are collected before they have an opportunity to settle on the floor of the kerf. It is desirable to ensure that the floor of the kerf is clean.

The spacing between the rear steering member 52 and the front steering member 58 is determined by the configuration of the endless kerf being drilled.

The rear steering member 52 would typically be spaced at a distance equivalent to three drill holes behind the hole being drilled. However, the larger the diameter of the endless kerf to be drilled, the further back the rear steering member 52 would preferably be located relative to the front steering member 58 in order to properly steer the steering dolly 50.

The joining member 56 is shaped so that the drill sleeve 54 is positioned along the desired path of the kerf to be drilled. The joining member 56 may be

adjustable in length and angular orientation so as to control the positioning of the front steering member 58 and thus the drill sleeve 54, relative to the rear steering member 52. To achieve this, the joining member 56 may include a hinged member 55 that enables the front steering member 58 to be rotated relative to the rear steering member 52. The hinged member may also enable the spacing between the rear steering member 52 and front steering member 58 to be varied. Locking means 57 is preferably provided to lock the joining member 54 in the required angular and length configuration.

The steering dolly 50 is arranged to be supported in the in the kerf by at least one support cable. The cable is attached to the cable anchor 59.

An apparatus according to the present invention is advantageous because it enables an endless kerf to be readily drilled. An apparatus according to an embodiment of the invention is relatively simple in design and easy to operate.

A steering dolly in accordance with an embodiment of the invention when used in conjunction with the inventive drilling apparatus facilitates the proper location of the drill 24 relative to a previously drilled hole. This aids in the accurate construction of a kerf.

The embodiments have been described by way of example only and modifications within the spirit and scope of the invention are envisaged.