Background of the invention

The invention relates to method for post drilling insertion, wherein an elongated insertion object is fed into a pre-drilled hole. The feeding is per- formed by means of an insertion unit, which is arranged to a free end a boom that belongs to a mining vehicle. The insertion object is pushed to the pre- drilled hole at least partly.

The invention still further relates to an insertion unit and to a mining vehicle.

The field of the invention is defined more specifically in the preambles of the independent claims.

Rock may be drilled in rounds. Then, drill holes are first drilled in rock, after which the drill holes are charged and blasted. Rock material becomes detached from the rock by the amount of the length of the round, and it is transported elsewhere before drilling the next round. Various tunnels, underground storage halls, containers, parking spaces or other corresponding rock caverns may be formed in the rock by excavation. However, the rock in which such rock caverns are excavated is not always sufficiently firm, uniform and stable by nature. Also, blasting a round may break or otherwise weaken the rock defining the rock cavern, so that the firmness of the rock is insufficient after excavation. Thus, it is rather typical that the ceiling and walls of the rock cavern, sometimes even the floor, must be reinforced. Reinforcing may be done by drilling to the rock several reinforcement holes in which a rock bolt, a cable or the like reinforcement member or reinforcement material is fitted. The reinforcement holes may be drilled by using a mining vehicle provided with a drilling boom having a drilling unit and means for mounting the reinforcement in the drilled hole. The drilling unit and reinforcement insertion means are arranged to the drilling boom so that at first a drill hole is drilled and there after the drilling unit is indexed away and the insertion means are placed in the front of the drill hole mouth. The drilling boom is kept stationary and the units at the free end of it are moved. A disadvantage in such arrangement is one unit stands still while the other unit is operating, whereby the working principle is ineffective. Also this arrangement causes extra weight and stresses to the boom construction. Brief description of the invention

An object of the invention is to provide a novel and improved method, an insertion unit and a mining vehicle for inserting objects into pre-drilled drill holes.

The method according to the invention is characterized by changing feeding angle of the insertion object during the insertion relative to the direction of the pre-drilled hole.

The insertion unit according to the invention is characterized in that the insertion unit comprises at least one angle adjusting device for changing the feeding angle of the insertion object.

The mining vehicle according to the invention is characterized in that the insertion unit comprises at least one angle adjusting device, whereby a feeding angle of the insertion object can be changed during the feed.

An idea is that the drilling unit and the insertion unit are in different booms. Furthermore, the insertion unit is provided with one or more angle adjusting device which is arranged to change or alternate feeding angle of the insertion object relative to the direction of the pre-drilled hole.

An advantage of this is that when the operating units are in booms of their own the operation is effective. Further, the disclosed angle adjusting feature finds the hole direction automatically, whereby there is no need to position the inserting unit exactly to the same direction as a center line of the pre- drilled hole. This makes the positioning of the insertion unit faster. Further, less demand is set to directional information of the pre-drilled hole and insertion unit. Moreover, the insertion object penetrates more easily to the pre-drilled hole due to the feeding angle adjustment, whereby feed force can be decreased. The construction is subjected to minor stresses, which improves the operational life of the insertion unit. Also, thanks to the presented solution feeding of the insertion object can be ensured even in demanding circumstances and situations. Thereby preplanned post-drilling measures can be per- formed effectively. All in all, a solution is presented to miss-alignment and hole irregularity problems occurring in the insertion procedure.

According to an embodiment the insertion unit is provided with an angle adjusting device which is arranged to move the rear end of the feed beam in transverse direction relative to the feed line. During the adjustment the front end of the feed beam can be kept stationary in transverse direction. According to an embodiment a front end of the insertion object is kept stationary in a transverse direction during the change in the feeding angle. Thereby the change in the feeding angle is performed relative to the front end.

According to an embodiment the adjustment of feeding angle of the insertion object is set to be proportional to the feeding distance. At the beginning the feeding angle is changed with a greater magnitude and when feeding proceeds, the angle adjustment decreases. At the end of the feeding cycle the feeding angle adjustment may be terminated. The decrease in angular adjust- ment can be continuous or it can be accomplished step wise.

According to an embodiment the angle adjusting device is arranged to rotate or turn the rear end of the feed beam along a curved path of movement.

According to an embodiment the feeding angle is changed by apply- ing a spiral movement, whereby the rear part of the insertion object proceeds during the insertion along a helical path of movement as it is simultaneously moved in its longitudinal feed direction.

According to an embodiment the insertion unit is provided with one or more sensing means for detecting load that resists pushing of the insertion object into the pre-drilled hole. The insertion unit may comprise one or more force sensor, for example a strain gauge, or alternatively force generated by the feeding device can be measured. In case feeding angle of the insertion object is incorrect, the rock is fractured or otherwise unstable, or if the pre- drilled hole includes a partly collapsed narrow section, there occurs increased force resisting the feeding of the insertion object. In the control unit there may be a preset force level above which level insertion aid measures are started at the latest.

According to an embodiment the feeding of the insertion object is stopped when the force resisting the feeding exceeds the preset force level. This avoids jamming of the insertion object and breakage of the feeding equipment and the insertion object.

According to an embodiment the feeding of the inserted object is stopped and the feeding direction is changed from the normal feed direction to the reverse direction when the force resisting the feeding exceeds the preset force level. The insertion object can be pulled backwards for a relatively short distance and after that the feeding to the normal feed direction is started again. If necessary this push and pull sequence is repeated. The feeding aid cycle including the change in the feeding direction can be combined with the feeding aid cycle including the change in the feeding angle. At the end of the feeding of the insertion object when no angle adjustment is no longer possible problems occurring in the feeding can be solved by means of push and pull aid cycle.

According to an embodiment the insertion unit is controlled by one or more control unit. The control unit may be provided with two, three, four or even more installation modes having different control strategy for installing an object into a pre-drilled hole.

According to an embodiment the operation cycle of the insertion unit is controlled automatically by means of the control unit. When the drill hole position is detected by the positioning system the control unit may start the automatically insertion cycle including the steps and measures disclosed in this application.

According to an embodiment the operation cycle of the insertion unit is controlled manually by an operator of the mining vehicle or alternatively in co-operation with the control unit.

According to an embodiment the inserting unit is provided with one or more installation aid means in addition to the angle adjusting device.

According to an embodiment vibrating forces are directed to the installed object in order to facilitate the installation. The installation unit may be provided with one or more vibrating device. The vibrating device may comprise a hydraulic motor which is arranged to rotate an eccentric piece, for example. The vibration may occur simultaneously with one or more other installation aid means disclosed in this application.

According to an embodiment the installed object is rotated around its longitudinal axis in order to facilitate the installation. The installation unit may be provided with a rotation device. The rotation device may correspond to a hydraulic rotation motor of a drilling machine, for example. The rotation may occur simultaneously with one or more other installation aid means disclosed in this application.

According to an embodiment impact pulses are directed to the installed object during insertion. Thus longitudinally propagating stress waves are formed so that the installation is facilitated. The installation unit may be provided with an impact device. The impact device may be hydraulically oper- ated, for example. Percussion may occur simultaneously with one or more other installation aid means disclosed in this application.

According to an embodiment the pre-drilled hole is a reinforcing hole. In this case the insertion object may be an elongated physical piece such as a rock bolt, tube or cable that is pushed into the drill hole. Alternatively the insertion object may be a feed hose, tube or channel that can be partly pushed into the drill hole where after reinforcing injection material such as a concrete or any other soldering material can be fed through the hose inside the drill hole. Thereby the insertion object may be a reinforcing piece or feeding means for charging material.

According to an embodiment the pre-drilled hole is a blasting hole. In a post-drilling phase an explosive is fed to the drill hole. The explosive can be in a form of a powder or granules whereby it can be fed into the drill hole by means of an elongated feed hose, tube or channel pushed at least partly in- side the drill hole. Further, it is possible to use explosive cartridges or packages, which can be rammed to the drill hole by means of an elongated bar. Moreover, in a small-charge-blasting mining method propellant charges are fed into the drill hole through an elongated hose or tube. Thereby the insertion object may be an elongated explosive package or feeding means for blasting or propellant material.

According to an embodiment in the post drilling phase an elongated measuring probe is fed into the drill hole. Thereby the insertion object may be a sensing or measuring instrument. By means of such instrument drilling accuracy compared to a drilling plan can be confirmed. For example direction of the drill hole and bottom coordinates of the drill hole can be determined.

According to an embodiment the mining vehicle is a post-drilling vehicle without any drilling unit. Such a mining vehicle is a special-purpose vehicle equipped only for feeding insertion objects into the pre-drilled holes. Construction and control of such special mining vehicle can be optimized according to one purpose only.

According to an embodiment the mining vehicle is a multi-use vehicle being capable of drilling and insertion operations. Such a mining vehicle is provided with at least two booms wherein at least one first boom is a drilling boom provided with a drilling unit and at least one second boom is a post- drilling boom provided with an insertion unit. According to an embodiment the positioning of an insertion unit at a pre-drilled hole includes two phases, namely a rough positioning and a fine positioning. The rough positioning is based on information gathered during the drilling of the hole in question. For example coordinates and directional angles of the holes are stored during drilling. By means of the rough positioning the insertion boom and the insertion unit therein can be positioned close to the pre-drilled hole. In the fine positioning the insertion unit is positioned to the pre- drilled hole so that it is possible to feed a front end of the insertion object to a hole collar. The insertion device may be provided with one or more cameras and a hole recognition system to identify the pre-drilled hole in a rock surface. The hole recognition system detects accurate position of the pre-drilled hole and control commands are given to boom actuators to implement the fine positioning. Also, the insertion unit may be equipped with another type of detector to detect or measure the accurate position of the hole mouth. An advantage of this embodiment is that positioning is faster since in the rough positioning the insertion unit can be moved with rapid movements at a proximity of the pre- drilled hole after which only a short distance needs to be moved accurately in the fine positioning step. The stored positioning information allows the fast rough positioning. This embodiment also makes it possible to use unmanned mining vehicles for post-drilling insertion.

According to an embodiment one or more identifier is arranged in connection with at least one drilled bore hole in order to facilitate positioning of devices used in the post-drilling phases. The insertion unit may be provided with means for reading or identifying the identifier placed into the drill hole or near the mouth of the borehole. The drilling unit may be provided with a mounting or applying device for arranging the identifier at the drill hole before starting the drilling operation, during the drilling operation or directly after the drilling. The identifier is installed before the drilling unit is moved away from the drilled hole towards the next drill hole position. The use of the identifier fastens and simplifies the positioning of the post drilling units and devices and makes the positioning accurate too.

According to an embodiment one or more drilled hole is provided with one or more physical identifier piece. The identifier may be a tubular piece, which can be partly inserted in a borehole, for example. The identifier improves detection of the drilled hole. The identifier may have a colour or a shape that is easier to detect by means of a camera. The identifier piece may form a sharp edge for the drill hole, which improves detection of the hole by optical means. Furthermore the identifier may comprise a transmitter and the post-drilling device may comprise a receiver whereby a wireless data connection can be created between the identifier and the insertion device. The data transmission can be used for positioning the post-drilling units accurately to the predrilled hole. The identifier may comprise a RFID (Radio Frequency IDentifi- cation) tag, for example.

According to an embodiment one or more pre-drilled hole is provided with one or more colour medium. Around the drilled hole a colour marking can be painted. The marking may have an annular shape. The drilling unit may be provided with a spraying device or nozzle for applying the colour medium to the drill hole collar. The colour medium can be selected so that the pre-drilled hole can be detected more easily with an optical hole recognition system comprising one or more cameras and a computer vision system. Thanks to the painted marking influence of shadows and surface irregularities can be diminished. One possibility is to use reflecting paint or electromagnetic waves emitting paint and to provide the insertion unit with a light source or another suitable emitter. The computer vision system executes an image processing for digital images taken by a digital camera arranged in the post-drilling unit. The im- age processing can be based on feature detection and feature extraction. As a result of the image processing accurate position of the pre-drilled hole can be automatically detected and control commands can be formed in a control unit of the mining vehicle for controlling boom actuators. The identifier according to this embodiment can radically improve efficiency of the optical hole recogni- tion. Painted identifier is also easy to apply, inexpensive and endures well in demanding conditions.

According to an embodiment colour medium is fed through a drilling tool in order to make a position identifier to the rock surface. The colour medium can be fed via normal flushing channels to a drill bit wherefrom the colour medium spreads to surrounding surfaces. An advantage of this embodiment is that no separate paint system needs to be arranged in the drilling unit.

According to an embodiment colour medium is fed through a drill bit after being extracted from the drill hole. Thereby a painted ring is formed around the drill hole opening. This improves optical detection of the edge of the drill hole opening. If desired, the paint inside the hole can be removed by reinserting the drill bit inside the drill hole and feeding flushing water through the drill bit to the drill hole whereby the paint is flushed away from the inside surfaces of the drill hole. When the paint is removed inside the hole the edge detection of the drill hole opening is improved since the drill hole shows as a dark circle, which is surrounded by the colour marking. The colour medium can be chosen so that a clear contrast occurs between the dark circle and the annular paint marking.

According to an embodiment two or more different colours are used for marking the drilled holes. The above disclosed physical identifier piece or painted marking may have a colour code system wherein different colours may indicate rock features such as rock stability, fractured rock or voids in rock. Hazardous drill holes can also be provided with a specific colour code. Information for the colour code system can be gathered during the drilling manually by the operator of the rock drilling rig and automatically by means of sensors and a drilling monitoring system.

Brief description of the figures

Some embodiments are described in closer detail in the accompanying drawings, in which

Figure 1 shows schematically a rock drilling rig positioned in the face of a rock cavern for drilling reinforcement or blasting holes,

Figure 2 shows schematically a perspective view of a tunnel having blasting holes and a reinforcement fan,

Figure 3 shows schematically and seen from above an embodiment wherein a separate drilling vehicle and post-drilling vehicle are used,

Figure 4 shows schematically and seen from above an embodiment wherein a mining vehicle includes a drilling boom and a post-drilling boom,

Figure 5 shows schematically an insertion unit,

Figures 6a - 6c show schematically an insertion cycle comprising feed and feed angle adjustment and possible other feeding aid measures,

Figures 7 - 10 show schematically some alternatives for moving a rear end of an insertion object along a curved path of movement,

Figure 1 1 schematically shows a rock surface area wherein drill holes are drilled and some of the openings of the drill holes are provided with an identification aid,

Figure 12 is a simplified diagram showing some features disclosed in this application. For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. In the figures, like reference numerals identify like elements.

Detailed description of some embodiments

Figure 1 shows a rock drilling rig 1 navigated in a face 3 of a tunnel

2 or the like rock cavern. The rock drilling rig 1 comprises a movable carrier 4 provided with one or more drilling booms 5, each of which has a rock drilling unit 6 at its outermost end. The drilling unit 6 may be positioned at a start location of a drill hole 7 by moving the boom 5. Drill holes 7 can be drilled for a round 8 and for a reinforcement fan 9. When the rock drilling rig 1 is driven to the drilling location, navigation is first carried out in which the coordinate system of the drilling rig is connected to the coordinate system of the working site. The actual drilling cycle is performed for each drill hole after the drilling unit 6 has first been positioned in the start location and direction determined by the drilling pattern or controlled by an operator manually. The control system may comprise one or more control units 12, which may be a computer or a processor capable of determining the actual position of the boom. The boom 5 may comprise two or more boom parts connected to each other by means of joints. In the boom 5, there may be sensors 1 1 or the like measuring devices, and on the basis of the position information obtained from them, the control unit 12 can determine the location and direction of the drilling unit 6. The positioning data of each hole 7 being drilled is stored and can be utilized in post-drilling actions such as in reinforcement or explosive insertion. Information can be gathered also during the drilling utilizing a so called measuring while drilling system. This hole specific information can be utilized in post-drilling measures too. The drill hole data can be transmitted to a control unit 13 of a mine or directly to a control unit of a second mining vehicle comprising post-drilling insertion means.

In Figure 1 , the drilling unit 6 is positioned at the point of an excava- tion drill hole 7a to be drilled. The tunnel 2 is excavated by drilling in the face 3 several excavation holes 7a substantially in the direction of a tunnel line L, which are charged with explosives after the drilling. At least positioning information of such blast holes 7a are saved for post-drilling charging. In blasting, rock material is detached from the rock by the volume of the round 9. Blasting a round may damage the rock defining the tunnel contour, or the firmness of the rock may be insufficient by nature in order to guarantee a safe tunnel. Thus, there may be a need to reinforce the ceiling 14 and walls 15 of the tunnel 2. The rock may be reinforced by drilling, several adjacent reinforcement holes 7b to which a rock bolt or the like reinforcement members can be fitted. The number, depth, diameter, start locations and directions of reinforcement holes 7b among other drilling information may be stored in a memory media and can be used in post-drilling reinforcement insertion. The reinforcement holes 7b may be drilled in a fan form, whereby there are drill holes on both walls 15 and on the ceiling 14 of the tunnel. The direction of the reinforcement holes 7b is crosswise to the tunnel line L.

In Figure 2 it is illustrated a tunnel 2 having blast holes 7a for excavating a round 8 and a reinforcement fan 9 provided with several reinforcement holes 7b. In a post-drilling phase insertion objects can be inserted into these pre-drilled holes 7 by means of an insertion unit arranged in a post-drilling boom. Charges such as explosives or propellants can be inserted into the blast holes and reinforcing members such as rock bolts or injection material or grouting material can be inserted into the pre-drilled holes.

Figure 3 shows an arrangement wherein drilling is performed by a mining vehicle 1 having one or more drilling booms 5a provided with drilling units 6, and for the post-drilling operation there is a special post-drilling mining vehicle 16 having one or more post drilling booms 5b provided with insertion units 17. At first a rock drilling rig 1 is positioned to a drilling site and planned holes 7 are drilled. Thereafter the post drilling mining vehicle 16 is positioned to the drilling site and insertion objects are fed into the pre-drilled holes 7. Coordinates, directional angle and other positioning information is stored during the drilling phase and the positioning information can be communicated from the control unit 12 of the rig 1 to a mine control unit 13 and to a control unit 18 of the post-drilling mining vehicle 16. Thereby positioning information gathered during drilling can be utilized in positioning the insertion unit 17 at the pre- drilled hole.

The positioning of the mining vehicles 1 , 16 to the working site can be based on fixed position identifiers 19, scanned wall surface profiles 20 of the working site, distance measurement based on dead reckoning, peg numbers 21 identifying mine distances, positioning based on wireless beacons, positioning in a wireless network, or their combination. Furthermore, in posi- tioning a tunnel laser 22 may also be utilized. After the positioning the mining vehicle is navigated so that one united coordinate system is used in drilling and post-drilling actions. At least the position of each drilled hole is stored when the drilling unit is positioned and drilling is started. Thereby coordinates of the drilled holes are known by the positioning system. Positioning data can be stored and managed by using a standardized format, such as IREDES (Inter- national Rock Excavation Data Exchange System), whereby data is compatible for different control units involved. The positioning information is communicated to the post-drilling mining vehicle 16, which is positioned and navigated to the working site where the pre-drilled holes are located. The insertion unit 17 is positioned according to the stored drill hole position information close to the pre-drilled hole 7. Since there may be inaccuracy in the positioning because of clearances of the boom joints, it may be impossible or difficult to position the insertion unit 17 directly to a collar of the pre-drilled hole. Therefore the positioning may be completed with a fine positioning wherein the insertion unit 17 is moved accurately to the collar of the pre-drilled hole. In the fine positioning a computer vision system can be utilized or different hole identifiers can be detected, for example. The fine positioning principles are discussed above in this application and also in connection with Figure 5.

In Figure 4 an alternative arrangement is disclosed. The mining vehicle 1 is provided with one or more drilling booms 5a with drilling units 6 and one or more post-drilling or insertion booms 5b with insertion units 16. In this embodiment the mining vehicle 1 is a multi-use apparatus that can be positioned and navigated to the working site in a manner disclosed in the description of Figure 3. The drilling and insertion are carried out with different booms 5a, 5b wherefore positioning data of the drilled holes are stored and utilized when rough positioning the insertion unit 17 after drilling close to the pre-drilled hole 7 indicated as a black circle in Figure 4. Positioning information can be stored in the control unit 12 of the mining vehicle 1 and, if needed, it can be communicated to one or more external control unit 13.

In Figure 5 one possible insertion unit 17 is shown. The insertion unit 17 comprises a feed beam 23 and a feed device 24 supported on the feed beam. The feed beam 23 can be attached to a post-drilling boom 5b by means of a cradle 25 or corresponding means. An insertion object 26 can be supported to a shank 27 of the feed device 24 and can be supported by a front support 28 to a front end 23a of the feed beam. Thereby the insertion object 26 is in a feed line 29 and can be pushed forward and pulled rearward by the feed device 24, which is movable on the feed beam 23. The front end portion 23a of the feed beam may comprise one or more cameras 30 in order to detect the pre-drilled holes after the insertion unit 17 is rough positioned 31 at a proximity 32 to the pre-drilled hole on the basis of collected drilling position information. Thereafter the insertion unit 17 is fine positioned 33 from the proximity position 32 accurately to a mouth of the pre-drilled hole 7. In fine positioning 33 several cameras can be used in order to produce stereo pictures or videos. The control unit 12 comprises an image processing system for detecting optically the accurate position of the pre-drilled hole 7. Alternatively or in addition to cameras the insertion unit 17 may comprise one or more identifiers, receivers or other de- tection means for hole recognition.

As can be seen in Figure 5, there may be an angle between the feed line 29 and a center line 34 of the pre-drilled hole. In case the insertion object 26 has incorrect feed direction relative to hole direction there exist forces resisting the feeding. The inserting device 17 may comprise one or more sensors, measuring units or other sensing means 35 for detecting the feed resistance. When feed resistance is detected the control unit 12 can start various feed aid measures in order to facilitate the insertion. The insertion unit 17 may comprise one or more angle adjusting device 36 by means of which a rear end portion 23b of the feed beam can be moved in transverse direction. The angle adjusting device 36 may rotate R the rear part 23b of the feed beam as it is shown in Figure 5. The rotation R is executed simultaneously with the feed F whereby a rear end of the insertion object 26 proceeds in a helical pattern. The front end of the feed beam may be supported against a rock surface or is kept stationary in some other way.

Figure 6a shows in a simplified manner start of the insertion cycle.

At the beginning the rotation R has a greater magnitude i.e rotation is performed with a greater radius. That is because at first the purpose is to sense and find the direction 34 of the pre-drilled hole 7. As the insertion proceeds and the insertion object 26 penetrates into the hole 7 the angle adjustment is decreased, as it is shown in Figures 6b and 6c. Further, in Figure 6c resisting forces are detected because there is an irregular portion 37 in the hole that causes problems for the insertion. Increased feed resistance is detected and the control unit may thereafter control the feeding with different feed aid control modes. According to one control mode feed direction is changed 38 between normal direction and reverse direction according to the feed resistance. In an- other control mode the insertion object 26 is rotated or turned around its longitudinal axis 39 during the feed.

Figures 7 to 9 illustrate in a highly simplified manner some possible angle adjusting devices 36 for implementing a transverse movement for a feed beam rear end 26b. In Figure 7 the angle adjusting device 36 comprises a pressure medium cylinder or a corresponding linear actuator 40 which can be turned a limited angle by means of turning actuator 41 . When the actuators 40, 41 are executed simultaneously the rear end of the feed beam can be rotated R in a desired magnitude and rotation direction. Depending the controlling of the actuators 40, 41 other curved movement paths and also linear transverse movements can be generated. In Figure 8 the angle adjusting device 36 comprises two linear actuators 42, 43, such as cylinders, which can be simultaneously controlled for generating rotation R and various paths of movements. In Figures 7 and 8 the combined action of two or more actuators causes the curved movement path. In Figure 9 the angle adjusting device 36 comprises a curved guide surface 44 along which the rear end of the feed beam 23 can be moved by a drive mechanism 45. In this embodiment the shape of the guide surface defines the movement path.

In Figure 10 there are shown two more alternatives for angular ad- justment devices. An alternative angle adjusting device 36a can be arranged between the feed beam 23 and the feed device 24. The device 36a may include actuators for moving the feed device 24 in the transverse direction. Further, an angular adjusting device 36b can be integrated to the feed device 24 or to a shank or adapter attached to the feed device. The adjusting device 36b comprises at least one linear actuator for moving the rear end of the insertion object 26 in a transverse direction and at least one rotation device for rotating the rear end of the insertion object around axis M after being first transversally moved 29a by the linear actuator. The operation of the device 36b is thus based on eccentric position of the rear end of the insertion object 26 and simul- taneous rotation. These angular adjustment devices 36a, 36b may be sufficient in some cases or they may be used in combination with the angular adjustment devices influencing the feed beam. Further, it is to be noted that other possibilities exists for rotating or moving the rear end portion of the insertion object during the insertion cycle.

In Figure 1 1 there is a rock surface area wherein drill holes are drilled and some of the openings of the pre-drilled holes 7 are provided with an identification aid. The pre-d lled holes 7 show as dark circles in optical detection means. A physical identifier 46 may be arranged in a drilling cycle inside the hole 7. The identifier 46 may a tubular piece having an outer edge 47 having a color or shape which improves optical detection. One possibility is to paint around the hole opening an annular identification marking 48 which improves the optical hole recognition. Furthermore, the hole may be provided with a RFID tag or corresponding machine readable active or passive wireless identifier 49.

In Figure 12 some of the above discussed embodiments and fea- tures are shown in a simplified diagram.

In some cases, the features disclosed in the present application may be used as such, irrespective of other features. On the other hand, when necessary, the features disclosed in the present application may be combined so as to provide different new combinations.

The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims.