Patent Publication Number: US-6655290-B2

Title: Structure of slackening type blasting mat

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a structure of a slackening type blasting mat for excluding by excavating part of a sloping surface formed by a base rock layer at one side, or both sides, of a road upon establishing or expanding of the road, or for excavating a part of a middle portion of a base rock layer made of a solid surface. 
     In general, there is a need to cut out a sloped surface made of base rock layer in road construction work for establishing or expanding a remote hill road, or a seashore road along mountain topography. In this case, excavating work of a base rock slope is executed by utilizing heavy-duty equipment such as a large type braker or excavator. In order to prevent accident or damage of passing vehicles during operation, a problem occurs in which mechanical excavating work utilizing the heavy duty equipment is decreased in its excavating efficiency, and a working term becomes longer when the sloped base rock layer is a hard base rock layer which is high in base rock strength. In such a case, cutting out the sloped rock surface is executed by a blasting method utilizing explosives. 
     In accordance with the blasting method of prior art, a so called mobile type blasting method has been used in which explosives filled in a number of blasting holes pierced into a base rock layer are detonated so that the base rick layer is completely released from the mother rock via its blasting pressure. 
     However, since the mobile type blasting method of the prior art increases the blasting pressure by using large quantities of explosives in order to completely release the base rock layer of a part desired to be cut out from the mother rock, there has been a problem of high blasting noise, and that a part of base rock broken upon blasting flies far away from the blasting site to a remote place. But also a blasting vibration coming from the blasting pressure is transmitted far away. Consequently, the blasting has been done by laying a mat made of rubber material or a straw bag etc. on the base rock surface so that the blasting noise is decreased and the broken base rock layer particles cannot be filed. But, since the rubber mat and the straw bag covered on the base rock layer fly away together with broken base rock particles by the blasting pressure, it is hard to expect an effect capable of largely decreasing the blasting noise and vibration. And in a case when human dwelling houses and the like are located within 100 m near a construction working site, there is a problem that an application of a blasting method is difficult to safely implement and a passing of neighboring roads should be isolated. 
     A base rock layer made of hard rock has to be cut out with a predetermined width at a construction site for establishing or expanding the mountain road or seashore road. Dwelling houses and livestock facilities scattered within 100 m from that construction working site and publicestablishments due to the exploding noise and the blasting vibration and the like produced upon blasting the base rock layer, not only the dwelling residences are exposed to noise but also flying stones are thrown into residences. Also, the building is shaken due to the blasting vibration or a ground-sinking phenomenon occurs. Furthermore, a problem is arisen which gives vast casualties to various animals bred in livestock facilities. Still further there is a worry about producing casualties which induces an accident due to influence of exploding sound, such as when a locomotive engine driver is startled causing a derailing accident of the train. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a blasting mat assembly, which does not influence residences near the working site, or livestock facilities and public establishments. 
     Still another object of the present invention is to make even a part of a middle portion of base rock layer made of a non-free surface to be excavated to a predetermined depth by the blasting method. 
     In order to attain the objects of the present invention, there is provided a blasting mat assembly comprising: 
     a metal plate having a continuous bottom major surface for covering a blasting region, said plate having a thickness capable of containing blasting forces within said region; 
     an elastic barrier connected to the periphery of the continuous bottom major surface for dampening blast noise and containing flying debris generated by the blast; and 
     a frame having a substantial weight resting on a top major surface of the metal plate, said frame having metal beams in a grid configuration overlying the top major surface of the metal plate. 
     The elastic barrier comprises a plurality of juxtaposed rubber tires. Axes of the rubber tires are oriented substantially orthogonal to said top and bottom major surfaces. 
     The beams of the frame are preferably steel I-beams or H-beams. The metal plate is steel and has a thickness of at least 3 mm. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a side view of one embodiment for explaining the present invention, 
     FIG. 2 is a plan view for showing a state of a blasting hole arrangement of the present invention, 
     FIG.  3  and FIG. 4 are cross sectional views showing a pierced hole depth of blasting holes of the present invention, 
     FIG. 5 is a view of a blast executing state of the present invention, 
     FIG. 6 is a perspective view for depicting a blasting mat structure of the present invention, 
     FIG. 7 is a cross sectional view of blasting mat of the present invention, and 
     FIG. 8 is a view of an embodiment applying the present invention to a solid surface base rock layer. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     Explaining an embodiment of the present invention in more detail with reference to the accompanying drawings, FIG. 1 is a side view of one embodiment for explaining the present invention. 
     A reference numeral  1  depicts a base rock layer formed at one side or both sides of road when establishing or expanding a mountain road or seashore road, and reference numeral  2  denotes a blasting mat assembly according to the present invention. 
     The blasting mat  2  is constructed such that a steel plate member  21  having a thickness (more than 3 mm) and a continuous lower major surface capable of sufficiently bearing the blasting pressure of explosives is provided over a blasting hole. An elastic member  22  is fixedly attached to an edge portion of the steel plate member  21  thereby diminishing blasting noise and flying stones. A weight reinforcing member  23  made of a steel frame such as from I-type beams or H-type beams rests on a top surface of the steel plate member  21  and is welded to edge portions in a grid shape. A carrying wire  24  capable of lifting the blasting mat  2  is fixedly attached at a top surface of the steel plate member  21 , or else by a hooking member to its weight center portion, so that the blasting mat  2  can be moved and carried by utilizing heavy duty equipment  3 , such as a large type braker or excavator. 
     The elastic member  22  attached to bottom edge portion of the blasting mat  2  is very elastic and easy to attach by bolts and the like. It is preferable to use waste tires  22   a  which sufficiently bears the blasting pressure together with vibrations of the steel plate member upon blasting of explosive and simultaneously exterior discharging of blasting noise, blasting gas and flying stones. A close adherence to bumpy ground surfaces is helpful so that all directions about the steel plate member  21  are protected. 
     The blasting method of the present invention, which blasts and cuts out the portion between free surface  11  and cut-out surface  12  of the base rock layer  1  from a top layer to a bottom layer stepwise by using the blasting mat  2  as described above, operates as follows. 
     A blasting region  14  is formed on a horizontal top surface between free surface  11  and cut-out surface  12  of the base rock layer by equally dividing the area into predetermined regions. Then a number of blasting holes  15  are pierced at predetermined distance intervals in each blasting region  14 , and the blasting holes  15  are formed not only in the blasting regions  14  but also in neighboring blasting regions  14 , the holes are pierced so as to maintain a predetermined distance therebetween among the blasting holes  15 . 
     Each of the blasting holes  15  formed in the blasting regions  14  are pierced by previouslyestablishing the piercing depth to reflect the dislocation structure of the base layer  1 . 
     That is, as in FIG. 3, the blasting hole  15  located at adjacent to free surface  11 , and the blasting hole  15  located at the middle, are deeply pierced while the blasting hole net to the cut out surface  12  is pierced a little shallower whereby the blasting method can be executed in steps, or as shown in FIG. 4, the blasting method can be executed by equally piercing the depth of all blasting holes. 
     An explosive  15   a  having a blasting power capable of slackening the cutting out portion up to the depth desired, is filled in the blasting holes  15  formed in each of the blasting regions  14 . Then a blasting lead wire is connected, and a quantity of explosive filled to the blasting hole  15  is filled only up to a degree (less than 0.4 kg/m2) which is relatively weak so that only a crack of the base rock layer  1  is slackened from the mother rock, i.e., cut out surface  12 . Said blasting lead wire is provided such that the explosives  15   a  filled in the blasting holes  15  are located at each blasting region  14  can be subsequently blasted at time intervals of extremely short time periods (about 0.02 second to 0.05 second). Sand  15   b  is filled to the blasting hole  15  after connecting the blasting lead wire to the explosives  15   a.    
     As described above, after the explosive  15   a  and the sand  15   b  are filled into the blasting hole  15  of each blasting region  14 , a blasting mother wire for blasting the explosive  15   a  of each blasting hole  15  is connected to the blasting means, and then the blasting mat  2  is lifted by heavy duty equipment  3 , whereby the top surface of the blasting region  14  to be blasted is covered. Since the area of the blasting mat  2  is bigger than the blasting region  14 , and the waste tires  22   a  of elastic member  22  are closely adhered on the top surface of the blasting region  14  outside of the blasting holes  15 , and are pressed by the weight of reinforcing member  23 , even if the top surface of the blasting region  14 , i.e., the horizontal top surface  13  of base rock layer  1  is an uneven and irregularly bumpy surface, the waste tires  22   a  of the elastic member  22  are closely adhered on top surface of bumpy blasting region  14 . The weight reinforcing member  23  is strongly pressed by a boom bar of the heavy-duty equipment  3 , said waste tires  22   a  are pressed and adhered on the top of the blasting region  14  by more strong elasticity. At the same time, even among mutually neighboring waste tires  22   a , the blasting mat  2  maintains a firm posture to contain strong blasting pressure and vibration. 
     As described above, during blasting the blasting mat  2  provided over the blasting region  14  is pressed by the heavy duty equipment  3 , and the explosives  15   a  filled into each blasting hole  15  are successively blasted. At this moment, the successive blasting of explosives  15   a  produces only a crack so that the base rock layer  1  of the blasting region  14  is completely divided from the cutting out surface  12 , and the sand  15   b  which has been filled to the blasting hole  15  upon blasting of explosive  15   a  and blasting gas and blasting noise are moved upward of the blasting hole  15  responsive to strong pressure. The steel plate member  21  of the blasting mat  2  which covers the top surface of the blasting region  14  is a steel plate of a thickness capable of sufficiently bearing the blasting pressure, and since the waste tires  22   a  of elastic member  22  are, not only closely adhered on top of the blasting region  14 , but are closely adhered each other, the blasting pressure produced upon blasting of explosives  15   a  and the flying sand accompanying it and the blasting gas, are not flown or leaked through the exterior of the blasting mat  2 . Since the waste tires  22   a  are elastic each absorb the blasting noise and vibration. The blasting noise and vibration transferred around blasting site can be significantly decreased, and the blasting pressure of explosives  15   a  are of a degree capable to cut out with a crack base rock layer  1  from mother rock. The blasting vibration is transferred only around of the blasting region  14 , but it is not transferred outwardly. 
     Thus, when the blasting work of the blasting region  14  of one place is finished, the blasting mat  2  is moved by heavy-duty equipment  3  to the next blasting region  14  and covered. The blasting work is progressed in a stepwise manner, and after the blasting works of all blasting region  14  of the base rock layer  1  are finished, the cutting out work of the base rock layer  1  is completed via means excavating the base rock layer  1  of the blasting region  14  by heavy duty equipment such as a braker, ripper and the like. 
     EXAMPLE 
     A blasting of a base rock layer was tested as follows by applying the blasting method in accordance with the present invention, and measured results such as vibration and noise according to it are shown in Table 1. 
     In accordance with the above test results, the maximum value of noise at a facility distanced by  50  m from the blast working site was measured as 67.6 dB, and it did not exceed 60 dB. However, noise lower than 90 dB causes humans and animals to start to feel pain from the noise. Particularly, the noise at 10 m neighboring the working site was no more than 92.6 dB. In maximum value, and was lower than 100 dB equivalent to a vehicle running on highway. The vibration was also detected as 0.1 cm/s at 50 m. Therefore, it has shown that an influence giving to livestock was almost none in a case when a cattle shed or the like were distanced apart more than 100 m from the working site. 
     Blasting Condition 
     Blast working object: 
     Hard rock layer (a working site of condition as FIG.  2  and FIG. 3) cutting slope width 25 m, height 15*Blasting hole piercing diameter and equipment: 
     (Φ51 mm, Crawler drill 
     *Used Explosive: 
     Φ32 mm New MITE 5500 
     (product of Hankook Gun Powder Co. Ltd.) 
     *Used Detonator: 
     MS electric detonator (product of Hankook Gun Powder Co. Ltd.) 
     *Blasting Hole Piercing Depth: 
     Inner side hole 2.0 m, free surface side 3.0 m 
     Each blasting hole piercing distance: 0.9 m 
     Blasting hole piercing number: 6 ea (2 row Arrangement) 
     Blasting Mat: 
     Steel plate thickness 3.5 mm, width 3.0 m, length 2.3 m, weight 2.2 tom 
     op of the blasting mat is pressed by bucket of fork crane. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 vibraton, 
                   
                   
                 filling 
                   
                   
               
               
                 noise, 
                   
                   
                 quantity 
                 measuring value 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 measuring 
                   
                   
                 per 
                 particle 
                   
                   
                   
                 noise 
                   
               
               
                 instrument 
                 blasting 
                 distance 
                 blasting 
                 speed 
                 frequency 
                 acceleration 
                 PVS 
                 dB(A) dB(L) 
                 measuring 
               
               
                 kind 
                 numbers 
                 (m) 
                 (kg) 
                 (cm/sec) 
                 (Hz) 
                 (g) 
                 (cm/sec) 
                 storm pressure 
                 location 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 DS677 
                 1 
                 50 
                 0.75 
                 T:0.038 
                 &gt;100 
                 0.0298 
                 0.110 
                 67.6(A) 
                 50 m place 
               
               
                 (2506) 
                   
                   
                   
                 V:0.097 
                 51 
                 0.0331 
                   
                   
                   
               
               
                 (german 
                   
                   
                   
                 L:0.070 
                 73 
                 0.0414 
               
               
                 company 
                 2 
                 50 
                 0.75 
                 T:0.041 
                 39 
                 0.0215 
                 0.064 
                 62.0(A) 
               
               
                 product 
                   
                   
                   
                 V:0.046 
                 47 
                 0.0215 
               
               
                   
                   
                   
                   
                 L:0.080 
                 32 
                 0.0331 
               
               
                   
                 3 
                 51 
                 0.75 
                 T:0.079 
                 39 
                 0.0199 
                 0.010 
                 64.6(A) 
               
               
                   
                   
                   
                   
                 V:0.048 
                 73 
                 0.0255 
               
               
                   
                   
                   
                   
                 L:0.052 
                 34 
                 0.0182 
               
               
                   
                 4 
                 52 
                 0.5 
                 T:0.051 
                 37 
                 0.0149 
                 0.064 
                 65.8(A) 
               
               
                   
                   
                   
                   
                 V:0.030 
                 47 
                 0.0182 
               
               
                   
                   
                   
                   
                 L:0.048 
                 34 
                 0.0149 
               
               
                   
                 5 
                 53 
                 0.75 
                 T:0.083 
                 27 
                 0.0199 
                 0.100 
                 64.0(A) 
               
               
                   
                   
                   
                   
                 V:0.091 
                 51 
                 0.0348 
               
               
                   
                   
                   
                   
                 L:0.083 
                 32 
                 0.0199 
               
               
                   
                 6 
                 54 
                 0.5 
                 T:0.054 
                 37 
                 0.0149 
                 0.057 
                 65.0(A) 
               
               
                   
                   
                   
                   
                 V:0.045 
                 51 
                 0.0149 
               
               
                   
                   
                   
                   
                 L:0.040 
                 39 
                 0.0116 
               
               
                 BMIII 
                 1 
                 30 
                 0.75 
                 T:0.349 
                 54 
                 0.133 
                 0.528 
                 74.4(A) 
                 30 m place 
               
               
                 (BA5687) 
                   
                   
                   
                 V:0.051 
                 85 
                 0.196 
               
               
                 (german 
                   
                   
                   
                 L:0.394 
                 45 
                 0.116 
               
               
                 company 
                   
                   
                   
                 T:0.232 
                 51 
                 0.0928 
                 0.375 
                 74.4(A) 
               
               
                 product) 
                 2 
                 31 
                 0.75 
                 V:0.322 
                 54 
                 0.166 
               
               
                   
                   
                   
                   
                 L:0.289 
                 47 
                 0.109 
               
               
                   
                 3 
                 32 
                 0.75 
                 T:0.195 
                 60 
                 0.0829 
                 0.398 
                 73.1(A) 
               
               
                   
                   
                   
                   
                 V:0.230 
                 43 
                 0.113 
               
               
                   
                   
                   
                   
                 L:0.362 
                 45 
                 0.106 
               
               
                   
                 4 
                 33 
                 0.5 
                 T:0.140 
                 57 
                 0.0663 
                 0.296 
                 70.1(A) 
               
               
                   
                   
                   
                   
                 V:0.162 
                 39 
                 0.0563 
               
               
                   
                   
                   
                   
                 L:0.254 
                 43 
                 0.0696 
               
               
                   
                 5 
                 34 
                 0.75 
                 T:0.325 
                 47 
                 0.106 
                 0.568 
                 69.6(A) 
               
               
                   
                   
                   
                   
                 V:0.560 
                 43 
                 0.176 
               
               
                   
                   
                   
                   
                 L:0.378 
                 39 
                 0.109 
               
               
                   
                 6 
                 35 
                 0.5 
                 T:0.149 
                 57 
                 0.0729 
                 0.269 
                 68.0(A) 
               
               
                   
                   
                   
                   
                 V:0.227 
                 60 
                 0.0795 
               
               
                   
                   
                   
                   
                 L:0.257 
                 37 
                 0.0696 
               
               
                 BMIII 
                 1 
                 70 
                 0.75 
                 T:0.079 
                 38 
                 0.0331 
                 0.099 
                 65.8(A) 
                 70 m place 
               
               
                 (BA5745) 
                   
                   
                   
                 V:0.081 
                 51 
                 0.0255 
               
               
                 (german 
                   
                   
                   
                 L:0.064 
                 33 
                 0.0331 
               
               
                 company 
                 2 
                 70 
                 0.75 
                 T:0.049 
                 68 
                 0.0331 
                 0.083 
                 61.2(A) 
               
               
                 product) 
                   
                   
                   
                 V:0.071 
                 60 
                 0.0265 
               
               
                   
                   
                   
                   
                 L:0.069 
                 68 
                 0.0331 
               
               
                   
                 3 
                 2 
                 0.75 
                 Impossible 
                 43 
                 0.298 
                 impossible 
                 94.9(A) 
                  2 m place 
               
               
                   
                   
                   
                   
                 to measure 
                 54 
                 0.587 
                 to measure 
               
               
                   
                   
                   
                   
                 37 
                 0.324 
               
               
                   
                 4 
                 10 
                 0.5 
                 T:1.80 
                 49 
                 1.35 
                 2.00 
                 91.5(A) 
                 10 m place 
               
               
                   
                   
                   
                   
                 V:1.60 
                 73 
                 1.09 
               
               
                   
                   
                   
                   
                 L:1.59 
                 73 
                 0.981 
               
               
                   
                 5 
                 10 
                 0.75 
                 T:6.36 
                 15.8 
                 1.48 
                 10.8 
                 90.7(A) 
               
               
                   
                   
                   
                   
                 V:9.86 
                 19.7 
                 5.57 
               
               
                   
                   
                   
                   
                 L:6.12 
                 15.1 
                 3.13 
               
               
                   
                 6 
                 10 
                 0.5 
                 T:2.77 
                 79 
                 2.68 
                 3.46 
                 92.6(A) 
               
               
                   
                   
                   
                   
                 V:2.60 
                 64 
                 2.01 
               
               
                   
                   
                   
                   
                 L:2.17 
                 79 
                 1.75 
               
               
                   
               
            
           
         
       
     
     In accordance with the present invention the blasting method using an explosive is executed in order to cut out one part of a free surface of a base rock layer utilizing a mat assembly, including a mat body made of thick steel plate member and waste tire absorbing member covering the work site, so that flying stones, blasting noise, or blasting vibration are remarkably decreased, whereby not only casualty generation due to noise and vibration can be extremely minimized. But also public facilities, such as electric power transmitting towers whereby a part of a free surface of the base rock layer can be slackened from mother rock. Since stones after blasting are isolated, base rock layer cutting work is made to progress without controlling the passing of vehicles on neighboring roads. And, since an operator of a blasting site, and the heavy duty equipment such as a braker, ripper and the like excavating the blasted base rock layer are located at a short distance (about 5-10 m) of the blasting site , the excavating work can be speedily progressed by heavy duty equipment after the blasting work of the blasting region is finished, Consequently, cutting work of the base rock layer can be reduced.