Abstract:
With a reinforcement and/or anchor bolt ( 1 ) that can be used in mining and/or tunnel construction and that is to be screwed into bedrock ( 7 ), and that includes a bolt head ( 2 ), a bolt end ( 3 ), a bolt shaft ( 4 ) and a thread ( 5 ) that is at least partially configured on the bolt shaft ( 4 ), the objective is to attach the reinforcement and/or anchor bolt ( 1 ) inexpensively and reliably to the bedrock ( 7 ) with little technical effort. A ratio of the length of the reinforcement and/or anchor bolt ( 1 ) to the outer diameter of the reinforcement and/or anchor bolt ( 1 ) is greater than 20.

Description:
[0001]    This claims the benefit of German Patent Application DE 10 2010 002 214.4 filed Feb. 23, 2010 and hereby incorporated by reference herein. 
         [0002]    The present invention relates to a reinforcement and/or anchor bolt, to a method for reinforcing and/or anchoring bedrock in mining and/or tunnel construction, and to the use of a reinforcement and/or anchor bolt in mining and/or tunnel construction. 
       BACKGROUND 
       [0003]    Anchor systems are used in mining and tunnel construction to prevent ground movement of the bedrock or to slow it down or to secure large spalls of the bedrock so as to allow safe operation. Here, two functional principles are known which are, at times, also combined with each other. In mechanical systems, the anchor is secured by frictional engagement, whereby mechanical rock anchors generally also have an expansion shell. In chemical systems, reinforcement rods with a curing mortar are connected to the substrate or bedrock by means of adhesion. Here, the anchors are installed with or without pre-tensioning in the bedrock. The drawbacks of these two different anchor systems are that chemical anchor systems are expensive and that, with so-called expansion anchors, a punctual load is applied into the bedrock. Moreover, with chemical anchor systems, the curing is temperature-dependent, so that a long curing time has to be expected at low temperatures. The anchors cannot be dismantled, which is especially disadvantageous when they are used in coal mining. 
         [0004]    European patent application EP 0 623 759 B1 describes a thread-forming bolt that can be screwed directly into concrete masonry or the like and that comprises a bolt head, a bolt shaft and a thread. 
         [0005]    U.S. Pat. No. 5,114,278 discloses a mining bolt with a thread and a conical tip. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention is to provide a reinforcement and/or anchor bolt, a method for reinforcing and/or anchoring bedrock in mining and/or tunnel construction, and the use of a reinforcement and/or anchor bolt in mining and/or tunnel construction, whereby the reinforcement and/or anchor bolt can be attached inexpensively and reliably to the bedrock with little technical effort. 
         [0007]    The present invention provides a reinforcement and/or anchor bolt that can be used in mining and/or tunnel construction and that can be screwed into bedrock, comprising a bolt head, a bolt end, a bolt shaft and a thread that is at least partially configured on the bolt shaft, whereby the ratio of the length of the reinforcement and/or anchor bolt to the outer diameter of the reinforcement and/or anchor bolt is greater than 20, 30, 50 or 70. 
         [0008]    In particular, the ratio of the of the length of the reinforcement and/or anchor bolt to the outer diameter of the reinforcement and/or anchor bolt may be between 20 and 150, preferably between 30 and 120, especially between 40 and 100. 
         [0009]    In another embodiment, the pitch of the thread corresponds to the product of the outer diameter of the reinforcement and/or anchor bolt and of a factor between 0.2 and 1.2, especially between 0.4 and 0.9. 
         [0010]    In another embodiment, between the bolt head and the bolt end, the thread is configured on the bolt shaft only in the area of the bolt end of the bolt shaft, in particular, the thread is configured on the bolt end only at a distance from the bolt end of less than 80%, 70% or 50% of the length of the reinforcement and/or anchor bolt, and preferably, the core diameter of the bolt shaft without the thread in the area of the bolt head is smaller, preferably by less than 15%, 10%, 5% or 2%, than the core diameter of the bolt shaft with the thread in the area of the bolt end. 
         [0011]    Preferably, the ratio of the outer diameter to the core diameter is between 0.8 and 1.6, preferably between 1.0 and 1.4, especially between 1.1 and 1.2, and/or the ratio of the outer diameter to the pitch of the thread is between 1.0 and 3.0, preferably between 1.5 and 2.5, especially between 1.7 and 2.2, and/or the flank angle is in the range from 50° to 90°. The above-mentioned geometric configuration of the reinforcement and/or anchor bolt allows a reliable positive connection between the reinforcement and/or anchor bolt and the bedrock, especially between the thread of the reinforcement and/or anchor bolt and the bedrock. In this manner, the reinforcement and/or anchor bolt can be reliably connected with a positive fit to the bedrock simply by being screwed into a bore hole in the bedrock. Thus, in an advantageous manner, no chemical systems, for example, curing mortar, are needed to attach the reinforcement and/or anchor bolt to the bedrock, and furthermore, essentially no frictional connection is needed between the reinforcement and/or anchor bolt and the bedrock either, because the reinforcement and/or anchor bolt is attached to the bedrock essentially by means of a positive connection. 
         [0012]    In one variant, the bolt end is configured as a conical tip. The conical tip can be partially or completely shaped onto the bolt end of the reinforcement and/or anchor bolt. 
         [0013]    Advantageously, the bolt end, especially the conical tip, is made at least partially, especially completely, of a material—e.g. metal, especially tempered steel, for example, also as a coating, e.g. made of quartz sand or corundum, or in the form of a ceramic coating—that differs from that of the rest of the reinforcement and/or anchor bolt aside from the bolt end. 
         [0014]    In coal mining (underground mining), so-called longwall mining methods are used more and more often. In this case, the coal seam is mined between longwall panels using a large milling head or plow over the entire length. Before the mining can begin, the panels to be mined have to be secured with the reinforcement and/or anchor bolts, as a result of which the reinforcement and/or anchor bolt is situated in the coal seam that is to be mined. The milling head pulls out the reinforcement and/or anchor bolt together with the coal. Reinforcement and/or anchor bolts made of steel can cause problems when the coal is being conveyed and processed. For this reason, when reinforcement and/or anchor bolts are used in coal mining, they are made, preferably at least partially, of plastic, especially of fiber-reinforced plastic, so that the reinforcement and/or anchor bolt is chopped up by the milling head and cannot damage the conveyor belts. However, in order for the reinforcement and/or anchor bolt to be nevertheless screwed into the bedrock, the bolt end, especially in a configuration as a conical tip, is made of a material that is different from that of the rest of the reinforcement and/or anchor bolt, which is made of plastic. Consequently, the bolt end, especially the conical tip, is made of metal or by means of a coating on the plastic. Moreover, the thread can also be configured as a cutting profile consisting of a hard, wear-resistant layer, for example, the same coating as that on the bolt end. 
         [0015]    In another embodiment, the air-side bolt head is connected, for example, with a positive fit, to the rest of the bolt shaft, and it is made of a material that is different from that of the rest of the bolt shaft. For instance, the bolt head is made of metal, especially steel, and the rest of the bolt shaft is made of plastic. Here, the air-side bolt head preferably has a special geometry, e.g. a hexagonal shape, so that the torque needed to screw in the reinforcement and/or anchor bolt can be applied to the bolt head. 
         [0016]    In an additional embodiment, the diameter of the bolt head is essentially the same size as the core diameter of the bolt shaft or else larger, e.g. by 10%, 20% or 50%, than the core diameter of the bolt shaft. 
         [0017]    In another variant, a thread is present on the bolt head, and a nut, especially an anchor nut, is screwed onto this thread on the bolt head, so that this nut allows the reinforcement and/or anchor bolt to be screwed in as well as tightened, and the force on the anchor head can be transmitted to a head plate or to an anchor head construction. 
         [0018]    Advantageously, the reinforcement and/or anchor bolt, especially aside from the bolt end, can be made at least partially of metal, e.g. steel, or preferably fiber-reinforced plastic, e.g. GFP. Particularly when the reinforcement and/or anchor bolt is used in coal mining, it is made at least partially of plastic. 
         [0019]    In another embodiment, the bolt shaft has a solid or hollow cross section. Particularly in bedrock having a low compressive strength, the bolt shaft can be made with a hollow cross section. 
         [0020]    The invention also relates to a method for reinforcing and/or anchoring bedrock in mining and/or tunnel construction in that a reinforcement and/or anchor bolt, especially a reinforcement and/or anchor bolt described in this patent application, is inserted into the bedrock, whereby a bore hole is drilled into the bedrock and subsequently, the reinforcement and/or anchor bolt is screwed into the bore hole, so that preferably the bedrock is reinforced, and/or preferably an anchor is attached to the bedrock. 
         [0021]    In another embodiment, the thread of the reinforcement and/or anchor bolt cuts its way into the bedrock when the reinforcement and/or anchor bolt is screwed in, and/or a positive connection is created between the thread and the bedrock, and/or a bore hole is drilled whose diameter is smaller, especially by at least 10%, 20% or 30%, than the outer diameter of the reinforcement and/or anchor bolt, and/or a bore hole having a constant diameter is drilled and/or a reinforcement and/or anchor bolt is provided so that the pitch of the thread of the reinforcement and/or anchor bolt is between 0.3 and 1.5, preferably between 0.4 and 1.2, especially between 0.5 and 0.8, times the diameter of the bore hole, and/or a bore hole is drilled and/or a reinforcement and/or anchor bolt is provided so that the core diameter of the thread is smaller, especially by less than 15%, 12% or 8%, than the diameter of the bore hole, and/or a reinforcement and/or anchor bolt is provided so that the flank angle of the reinforcement and/or anchor bolt is calculated according to the formula ((compressive strength of the rock—145)/−1.5)±10° when the compressive strength of the bedrock is between 10 and 100 mPa, and the flank angle is 30°±10° when the compressive strength of the bedrock is more than 100 mPa. 
         [0022]    In another embodiment, a positive connection is created, especially by means of the thread, between the reinforcement and/or anchor bolt and the bedrock, and preferably the amount of the positive connection is at least 50%, 70%, 80% or 90% of the connection of the reinforcement and/or anchor bolt to the bedrock. Hence, the forces to be absorbed by the reinforcement and/or anchor bolt are transferred essentially positively into the bedrock and not by adhesion, by adhesive force or non-positively. 
         [0023]    In particular, the bore hole is drilled with a varying diameter so that an inner section of the bore hole has a diameter that is smaller, preferably by less than 2%, 5%, 10% or 20%, than the diameter in an outer bore hole section. 
         [0024]    In another embodiment, after the reinforcement and/or anchor bolt has been screwed completely into the bore hole, its bolt shaft that is provided with the thread is situated essentially in the inner bore hole section and its bolt shaft without the thread is situated in the outer bore hole section. 
         [0025]    In another variant, after the reinforcement and/or anchor bolt has been screwed completely into the bore hole, the ratio of the anchoring depth of the reinforcement and/or anchor bolt to the diameter of the bore hole is between 20 and 150, preferably between 30 and 120, especially between 40 and 100. 
         [0026]    The invention also relates to the use of a reinforcement and/or anchor bolt in mining and/or tunnel construction for reinforcing bedrock and/or for anchoring, whereby a reinforcement and/or anchor bolt described in this patent application is used. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Below, embodiments of the invention will be described in greater depth with reference to the accompanying drawings. The following is shown: 
           [0028]      FIG. 1  a side view of a reinforcement and/or anchor bolt with a partial lengthwise section of a bore hole in bedrock, 
           [0029]      FIG. 2  a lengthwise section of the reinforcement and/or anchor bolt in the bore hole in a first embodiment, 
           [0030]      FIG. 3  a lengthwise section of the reinforcement and/or anchor bolt in the bore hole in a second embodiment, 
           [0031]      FIG. 4  a lengthwise section of the reinforcement and/or anchor bolt in the bore hole in a third embodiment, and 
           [0032]      FIG. 5  a perspective view of a drill rod. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]      FIG. 1  shows a reinforcement and/or anchor bolt  1  for use in mining and/or tunnel construction. When used as a reinforcement bolt, bolt  1  serves essentially for reinforcing and stabilizing the bedrock  7 , and thus less for absorbing forces that are applied to the reinforcement bolt  1  on the air-side bolt head  2  and that are especially directed towards a longitudinal axis of the reinforcement bolt  1 . When used as an anchor bolt, bolt  1  serves less for reinforcing and stabilizing the bedrock  7 , but essentially for absorbing forces on the air-side bolt head  2  of the anchor bolt  1 . The reinforcement and/or anchor bolt  1  shown in  FIG. 1  can be used as a reinforcement bolt  1  and also as an anchor bolt  1  in mining or tunnel construction. 
         [0034]    The reinforcement and/or anchor bolt  1  ( FIGS. 1 through 4 ) has the air-side bolt head  2 , a bolt end  3  that is arranged in a bore hole  6  ( FIGS. 2 through 4 ), and a thread  5  on a bolt shaft  4 . The bolt shaft  4  has a section that is configured without the thread  5  in the area of the bolt head  2  as a bolt shaft  18  without the thread  5 , and it has a section on the bolt end  3  that is configured as a bolt shaft  19  with a thread  5 . Here, the bolt end  3  is partially configured as a conical tip  9  ( FIG. 1 ). The bolt shaft  4  of the reinforcement and/or anchor bolt  1  has a core diameter D i  on the bolt shaft  18  without the thread  5  as well as on the bolt shaft  19  with the thread  5 , and it has an outer diameter D a  on the thread  5  and a length A. Furthermore, the thread  5  has a pitch P that corresponds to the distance between two windings of the thread  5 . The thread  5  also has a flank angle α.  FIG. 1  also shows the bore hole  6  in the bedrock  7 . The bore hole  6  here has a diameter of D b . 
         [0035]      FIG. 2  shows a first embodiment of an arrangement of the reinforcement and/or anchor bolt  1  in a bore hole  6  that has been drilled in the bedrock  7 . The reinforcement and/or anchor bolt  1  is configured in the area of the bolt head  2  on the bolt shaft  18  in such a way that said bolt shaft does not have a thread  5 , and in another section of the bolt shaft  4  on the bolt end  3 , it has a thread  5 , or else a thread  5  is formed on the bolt shaft  19 . Here, the outer diameter D a  of the reinforcement and/or anchor bolt  1  is 20% to 30% larger than the diameter D b  of the bore hole  6 . After the bore hole  6  has been drilled, for example, with a drill rod  12 , whereby the bore hole  6  has a constant diameter D b , the reinforcement and/or anchor bolt  1  is screwed into the bore hole  6  in that a torque is applied to the bolt head  2 . Due to the larger outer diameter D a  of the reinforcement and/or anchor bolt  1  relative to the diameter D b  of the bore hole  6 , the thread  5  cuts its way into the bedrock  7  and a positive connection is created between the thread  5  and the bedrock  7 . In  FIG. 2 , the reinforcement and/or anchor bolt  1  is screwed completely into the bore hole  6  and can rest with or without pre-tensioning on a head plate  8 . Here, a force is exerted by the bolt head  2  onto the head plate  8 , preferably with pre-tensioning.  FIG. 2  also shows an anchoring depth L of the reinforcement and/or anchor bolt  1  and the length B of the bore hole  6 . The reinforcement and/or anchor bolt  1  in  FIG. 2  has a bolt end  3  that is completely configured as a conical tip  9 . The bolt end  3  or the conical tip  9  can also be detachably connected to the rest of the bolt shaft  4 , for example, by means of a screwed connection or a bayonet connection. Through the use of different bolt ends  3 , the reinforcement and/or anchor bolt  1  can be adapted to different types of bedrock  7 . Moreover, the core diameter D i  of the bolt shaft  4  is approximately 8% smaller than the diameter D b  of the bore hole  6 . As a result, in an advantageous manner, no friction occurs between the bolt shaft  4  and the bedrock  7  when the reinforcement and/or anchor bolt  1  is screwed into the bore hole  6 , so that consequently, the torque that has to be applied to the bolt head  2  to screw in the reinforcement and/or anchor bolt  1  can be reduced. 
         [0036]    When the reinforcement and/or anchor bolt  1  is used in bedrock  7  having a high compressive strength, e.g. solid rock, the bolt shaft  4  is generally configured with a solid profile, whereas, when the reinforcement and/or anchor bolt  1  is used in bedrock  7  having a low compressive strength, e.g. gravel, the bolt shaft  4  is generally configured with a hollow profile. When the reinforcement and/or anchor bolt  1  is used in a bedrock or substrate having a low compressive strength, a hollow profile is already sufficient to absorb the forces that act radially on the bolt shaft  4 . This can save material during the production of the reinforcement and/or anchor bolt  1 . The thread  5  for the reinforcement and/or anchor bolt  1 , especially when the bolt shaft  4  is configured as a hollow profile, can be created, for example, in that a profile wire is wound onto the bolt shaft  4  and laminated into it. 
         [0037]      FIG. 3  shows a second embodiment of the arrangement of the reinforcement and/or anchor bolt  1  in the bedrock  7 . The diameter of the bore hole  6  drilled into the bedrock  7  is larger on an outer bore hole section  11  than on an inner bore hole section  10 . The bolt shaft  19  with the thread  5  is essentially arranged on the inner bore hole section  10 , for instance, with a deviation of less than 40%, 30%, 20%, 10% or 5%. Here, the diameter D b  of the bore hole  6  on the inner bore hole section  10  is about 4% to 8% smaller than the outer diameter D a  of the reinforcement and/or anchor bolt, so that consequently, a positive connection is created between the thread  5  and the bedrock  7  on the inner bore hole section  10 . The diameter D b  on the outer bore hole section  11  is larger here than the outer diameter D a  of the reinforcement and/or anchor bolt. As a result, the reinforcement and/or anchor bolt can initially be inserted with a small amount of force into the anchoring area, namely, into the inner bore hole section  10 . Furthermore, this means that a lower and more constant screwing torque has to be applied onto the bolt head  2 , and a better and constant support is possible due to the smaller diameter D b  on the inner bore hole section  10 . For the rest, the second embodiment shown in  FIG. 3  corresponds to the first embodiment shown in  FIG. 2 . 
         [0038]      FIG. 4  shows a third embodiment of an arrangement of the reinforcement and/or anchor bolt  1  in a bore hole  6  that has been drilled in the bedrock  7 . Like in the first embodiment, the bore hole  6  has a constant diameter D b . In contrast to the first embodiment, however, the core diameter D i  of the reinforcement and/or anchor bolt  1  is smaller on the bolt shaft  18  without the thread  5 , for example, 2% to 8% smaller than the core diameter D i  on the bolt shaft  19  with the thread  5 . The outer diameter D a  of the reinforcement and/or anchor bolt  1  on the thread  5  is about 20% to 30% larger than the diameter D b  of the bore hole  6 , so that in the third embodiment as well, the thread  5  cuts its way into the bedrock  7  when the reinforcement and/or anchor bolt  1  is screwed into the bore hole  6 , and moreover, as a result, a positive connection can be created between the thread  5  and the bedrock  7 . Due to the fact that the core diameter D i  of the reinforcement and/or anchor bolt  1  on the bolt shaft  18  without the thread  5  is smaller than on the bolt shaft  19  with the thread  5 , the torque that is needed on the bolt head  2  can be reduced, since there is less friction between the bolt shaft  4  and the bedrock  7 . 
         [0039]      FIG. 5  shows a perspective view of the drill rod  12  for drilling a bore hole  6  with a varying diameter D b  as shown for the second embodiment in  FIG. 3 . The drill rod  12  has a drilling crown  13 , a stabilizer  14 , a first boring bar  15  having a small diameter, a boring tool  16  and a second boring bar  17  having a large diameter. Here, for example, the drilling crown  13 , the stabilizer  14  and the first boring bar  15  have a diameter of 15 mm, the boring tool  16  has a diameter of 32 mm, and the second boring bar  17  has a diameter of 18 mm. The diameter of the boring tool  16  is thus larger than the diameter of the second boring bar  17 , and the diameter of the second boring bar  17  is larger than the diameter of the first boring bar  15 . 
         [0040]    All in all, the reinforcement and/or anchor bolt  1  entails major advantages. The force that is to be exerted by the reinforcement and/or anchor bolt  1  into the bedrock  7  is applied by the thread  5  essentially positively into the bedrock  7 . The reinforcement and/or anchor bolt  1  is essentially connected with a positive fit or anchored to the bedrock  7  at its bolt shaft  19  with the thread  5 . Thus, it is possible to dispense with a complicated and disadvantageous anchoring of the reinforcement and/or anchor bolt by means of adhesion or by means of a non-positive connection (expansion). Hence, the reinforcement and/or anchor bolt  1  can be inserted into the bedrock  7  with little technical effort in that first a bore hole  6  is drilled, and subsequently the reinforcement and/or anchor bolt with the thread  5  is screwed into the bore hole  6 .