JP2015137788A - Blasting construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blasting construction method capable of reducing vibrations generated on a predetermined spot on the surrounding in accordance with blasting even when a position of a blasting object area is changed.SOLUTION: A dominant frequency at predetermined spots P1, P2 of vibrations transmitted between a working place A and the predetermined spots P1, P2 are determined beforehand and stepwise blasting of the working place A is performed according to the difference of blasting second at which a peak frequency different from the dominant frequency is generated. The dominant frequency at the predetermined spots P1, P2 is measured in such a state that the positional relationship between the working place A and the predetermined spots P1, P2 is determined and, therefore, even when the position of the working place A is changed, the dominant frequency can be precisely measured under distance or ground conditions in accordance with the positional relationship. Accordingly, resonance between the peak frequency produced by the difference of blasting second when performing the stepwise blasting of the working place A and the dominant frequency on the predetermined spots P1, P2 is avoided and vibrations generated on the predetermined spots P1, P2 are reduced.

Description

  The present invention relates to a blasting method, and more particularly, to a blasting method that reduces vibrations that occur at predetermined points around the blasting target region.

  In tunnel excavation work, the blasting method is adopted when the rock (face) to be excavated is extremely hard. In the blasting method, a plurality of charge holes are made in the face, and an explosive is loaded into the charge hole to cause an explosion. In the blasting method, various measures have been proposed to reduce the influence of vibration and sound on the surrounding environment.

  As described in Non-Patent Document 1 below, as a vibration reduction measure in the blasting method, there is known a method for reducing the dose per step by increasing the number of steps of the electric detonator used for the stage blasting. In electric detonators, the blast time is set by the delay agent in the tube. As an electrical detonator, for example, a DS detonator with a time interval of 250 ms and an MS detonator with a time interval of 25 ms are known. On the other hand, an electronic detonator capable of setting a shorter second time interval is known. In the electronic detonator, the second time interval is set by an electric timer using an IC chip in the tube.

  Since electrical detonators use time delay drugs, the actual time interval may vary greatly from the set time interval. In this case, the coincidence is low, for example, the seconds of the current initiation hole and the next initiation hole overlap. On the other hand, in the electronic detonator, the second time interval can be set in units of 1 ms, and the simultaneous property is high. In recent years, a new electronic detonator having a function capable of arbitrarily changing and setting the setting of the second time at the face according to the work performed at the face is also known.

  As described in Patent Documents 1 to 4 below, various blasting methods using an electron detonator are known. For example, in the construction method described in Patent Document 1, the single-shot blast vibration is predicted from the single-shot blast vibration, and the step-by-step explosion start time sequence satisfying a specific condition is calculated based on the predicted vibration. In the construction method described in Patent Document 2, the vibration power spectrum (the magnitude of vibration at each frequency) is reduced by setting the time difference between the initiation period and the fundamental period τ according to a pseudo-random number formula called M series. ing. In addition, in the construction methods described in Patent Documents 3 and 4, a slot was provided in the side portion of the charge hole of the tunnel face, and each charge hole was drilled at a constant interval, and the explosive was preliminarily tested and generated. Oscillation wave simulation determines the time interval of the initiation second that minimizes the energy or amplitude of the vibration wave.

  In these blasting methods, an electron detonator is used to set the time interval accurately, and a wave canceling effect is generated by superposition of vibrations, and vibration amplification is suppressed by this wave canceling effect.

International Publication No. 98/21544 Japanese Patent Laid-Open No. 2-302066 JP 2001-21300 A JP 2001-21298 A

Japan Explosives Manufacturers Association, “Such Blasting, Such Blasting Blast Case Collection”, March 2002, p. 10-13

  At tunnel sites that use the blasting method, it is important to reduce the blasting vibration of neighboring houses. For this reason, as in the blasting method described above, an electron detonator is used to accurately set the time interval for the initiation of the explosion, to improve the coincidence, and to reduce the vibration due to the interference of the waveforms at each initiation hole. However, in practice, since the tunnel face advances every day according to the excavation cycle, the distance from the ground structure or the ground condition differs every time the blasting occurs. Therefore, the vibration waveform of single blasting is predicted from the vibration waveform of stepwise blasting as in Patent Document 1 above, or the blasting is started for each blasting by simulation of the vibration wave generated in the test explosion as in Patent Document 3 above. Obtaining the time difference in seconds is difficult both technically and work-wise.

  An object of this invention is to provide the blasting method which can reduce the vibration which arises in the surrounding predetermined points with blasting, even if the position of a blasting object area | region changes.

  The present invention relates to a blasting method for reducing vibration generated at a predetermined point in the vicinity of a blast target region, and measuring a dominant frequency at a predetermined point of vibration generated by a single blast of the blast target region; A step of setting a detonation second time difference of the stage blasting and blasting so as to generate a peak frequency different from the frequency, and a step of performing a stepwise blasting of the blasting target region by the detonation second time difference.

  According to this blasting method, the prevailing frequency at the predetermined point of vibration transmitted between the blasting target area and the predetermined point is obtained in advance, and the time difference between the initiation seconds is set so that a peak frequency different from the prevailing frequency is generated. Step-by-step blasting is performed in the blasting target area. In this way, since the dominant frequency at the predetermined point is measured in a state where the positional relationship between the blasting target region and the predetermined point is determined, even if the position of the blasting target region changes, it corresponds to the positional relationship. The dominant frequency is accurately measured under distance or ground conditions. Therefore, when staged blasting of the blasting target area is performed, resonance between the peak frequency caused by the time difference between the explosion seconds and the dominant frequency at the predetermined point is avoided, and as a result, vibration generated at the predetermined point can be reduced.

  The blast target area is a face in tunnel excavation, and at least one single blast and step blast for measuring the dominant frequency may be performed continuously. As tunnel excavation progresses, the position of the face changes, but even if there is a security property at a predetermined location around the tunnel, the dominant frequency at the location of the security property is measured in accordance with the progress of tunnel excavation. Therefore, it is possible to reduce the influence of vibration on the security property at a predetermined point as the tunnel excavation progresses. In addition, since at least one single blast and step blast are performed continuously, tunnel excavation by stage blasting is performed, and an appropriate explosive second time difference according to the position of the face at that time is obtained by single blasting. Can be set. Therefore, the vibration generated at the predetermined point can be surely reduced in accordance with the progress of the tunnel excavation.

  An interval of 100 ms or more may be provided between at least one single blast and step blast. In this case, by setting an interval of 100 ms or more between the single blast and the step blast, the influence of the step blast on the measurement of the dominant frequency at a predetermined point can be eliminated.

  The predetermined points are two or more points. In the step of measuring the dominant frequency, in the step of measuring the dominant frequency at each of the predetermined points of vibration caused by single blasting of the blasting target region, In the process of setting two or more types of detonation seconds corresponding to each of the above, and performing the step-by-step blasting, the blasting target area is classified according to each of the predetermined points, and the stage of each division is determined by the set detonation second time difference. You may blast. In this case, the dominant frequency is measured for each category corresponding to each of two or more points, and the time difference between the initiation seconds is set. Therefore, even if the distance between the blasting target area and each point or the ground conditions are different, the time difference between the explosion seconds is set in consideration of those conditions. Therefore, vibration can be reduced at each point.

  If the time difference between the detonation seconds is 10 ms or less and the total detonation time for the stage blasting is 3 sec or less, the total detonation time is shortened while ensuring the desired number of stages necessary for the blasting. Therefore, it is possible to reduce the vibration generated at the predetermined point and to reduce the generation time of the vibration.

  In the step of setting the detonation second time difference, the peak frequency may be obtained by setting the reciprocal of the detonation second time difference or a multiple of the reciprocal of the detonation second time difference. In this case, it is possible to easily set a time difference between initiation seconds so that resonance between the peak frequency and the dominant frequency at a predetermined point can be avoided.

  According to the present invention, even if the position of the blasting target region changes, vibrations that occur at predetermined points around the blasting can be reduced.

It is a mimetic diagram showing a tunnel excavation field where a blasting method concerning one embodiment of the present invention was applied. It is a front view which shows the example of arrangement | positioning of the initiation hole in the face in FIG. It is sectional drawing which shows the example of arrangement | positioning of the explosive and detonator in a detonation hole. It is a schematic diagram which shows the tunnel excavation site where the blasting method which concerns on other embodiment of this invention was applied. It is a front view which shows the example of arrangement | positioning of the initiation hole in the face in FIG. It is a figure which shows the vibration data by the blast based on Example 1. FIG. (A)-(c) is a figure which shows the frequency-analysis result in the single blasting of 3 times in FIG. It is a figure which shows the frequency analysis result in the stage blasting in FIG. It is a figure which shows the vibration data by the blast based on Example 3. FIG. It is a figure which shows the frequency analysis result in the stage blasting in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

  As shown in FIG. 1, the blasting method according to the present embodiment is a method applied to tunnel excavation for the stratum X made of hard rock. This blasting method reduces vibration generated at predetermined points P1 and P2 located around the tunnel TNL (for example, on a hill) when tunnel excavation is performed. For example, in the example shown in FIG. 1, dwellings 1 and 2 are built at predetermined points P <b> 1 and P <b> 2 around a face A that is a blasting target area for tunnel excavation. This blasting method is intended to reduce vibrations generated at the predetermined point P1 or the predetermined point P2 and the residence 1 or the residence 2.

  As shown in FIG. 2, when performing blasting, the face A is provided with a plurality of initiation holes 10. The plurality of initiation holes 10 form a plurality of initiation hole groups B <b> 1 to B <b> 6 for performing staged blasting at the face A. Explosion hole groups B1 and B2 in the center of face A are for centering. The arrangement of the initiation holes 10 shown in FIG. 2 is merely an example, and the number and arrangement pattern can be changed as appropriate. The number and arrangement of the plurality of initiation holes 10 can be determined based on a known method. For example, as shown in FIG. 3, each initiation hole 10 is provided with a plurality of explosives (so-called parent die and increase die) 12 disposed in the hole 11 and a back-side explosive (so-called parent die) 12. A detonator 13 and a container 14 provided on the front side of the explosive 12 are provided.

  In the blasting method of the present embodiment, an electronic detonator capable of setting the detonation second in 1 ms units is used as the detonator 13. This electronic detonator has a function that allows the setting of the detonation seconds to be arbitrarily changed and set at the face A in accordance with the work performed at the face A. In this electronic detonator, for example, in the range of 1 ms to 30 ms, it is possible to set the time difference between the initiation seconds in units of 1 ms. By adopting the electronic detonator, it is possible to control the peak frequency generated by the stage blasting, and as a result, the vibration generated at the point P1 or the point P2 can be reduced.

  Furthermore, in the blasting method of the present embodiment, a plurality of blast holes 20 used for single blasting are provided in the face A apart from the plurality of blast hole groups B1 to B6 used for stage blasting. The initiation hole 20 is provided in the upper vicinity of the initiation hole groups B1 and B2 provided in the center of the face A. The structure of each detonation hole 20 is the same as that of the detonation hole 10 described above, except that the detonator 13 of the detonation hole 10 is set at the timing for single blasting. Is different. These initiation holes 20 are provided to measure the dominant frequency at a predetermined point P1 or P2 of vibration caused by single blasting of the face A.

  In the example shown in FIG. 2, three initiation holes 20 are provided, but the number of initiation holes 20 used for single blasting may be one or two, or four or more. The initiation hole 20 is not limited to being provided at or near the center of the face A, and may be provided on the outer peripheral side of the face A. A certain time interval is provided between the single blasting by the detonation hole 20 and the step blasting by the detonation hole 10. That is, the last detonation of the detonation hole 20 that performs single blasting and the first detonation of the detonation hole 10 that performs staged blasting are performed at regular time intervals.

  Then, the procedure of the blasting method of this embodiment is demonstrated. First, the initiation hole 10 and the initiation hole 20 are provided for the face A. That is, as described above, a plurality of initiation holes 20 for single-shot blasting and a plurality of initiation holes 10 for step-by-step blasting are provided in the face A. Here, an interval of 100 ms or more is provided between the single blast and the step blast. The interval between the single blast and the step blast is preferably 300 ms or more. On the other hand, even if the interval between single blasting and step blasting is too large, the blasting time (the sum of all blasting times for single blasting and step blasting) becomes long, so the maximum is 1000 ms. In other words, the interval between single shot blasting and stage blasting is set to 100-1000 ms. This interval is set to 500 ms, for example. A vibration meter is installed at each of the points P1 and P2, and the displacement speed generated in response to the blast of the face A is measured.

  Subsequently, single blasting with a plurality of detonation holes 20 and step blasting with a plurality of detonation hole groups B1 to B6 are continuously performed. At this time, if this blasting is the first blasting at the tunnel excavation site, a single blasting at the face A is performed in advance and the dominant frequency at the vibration points P1 and P2 is measured. The dominant frequency can also be obtained by frequency analysis (FFT analysis). Then, the peak frequency is obtained by taking the reciprocal of the detonation second time difference in the stage blasting or a multiple of the reciprocal of the detonation second time difference, and the detonation second time difference is set so that the peak frequency is different from the dominant frequency. In the first blasting, the staged blasting is performed with the time difference of the explosive seconds set in advance as described above.

  Explaining the relationship between the initiation time difference and the peak frequency, the present inventors have found the following findings when performing staged blasting with the initiation time difference as T (ms). The first point is that the vibration value to be measured has a high peak at a frequency that is the reciprocal of the detonation time difference T (f = 1 / T) and a frequency that is a multiple of the reciprocal of the detonation time difference T (2f, 3f...). That is. The second point is that, among the frequencies having a high peak, particularly the reciprocal of the time difference T of the initiation seconds has the highest peak. The third point is that the above relationship is established by the high accuracy of the time difference between the detonation seconds of the electron detonator. The fourth point is that the peak frequency of the vibration value (the dominant frequency of the vibration value due to the stage blasting) can be arbitrarily controlled by adjusting the time difference between the initiation seconds.

  In tunnel excavation, the blasting operation in which single blasting and step blasting are continuously performed is repeated. The frequency of repetition is, for example, about 2 to 10 times a day. In the second and subsequent blasting, the time difference between the explosive seconds for the staged blasting is set based on the dominant frequency at the points P1 and P2 measured by the single blasting of the previous blasting. Again, the time difference of the initiation seconds is set so that the dominant frequency at the vibration points P1 and P2 at the time of the previous single blasting and the integral multiple of the reciprocal time difference of the explosion blasting at the stage blasting (ie peak frequency) are different. Set. Preferably, it is set so that the reciprocal of the initiation time difference is larger than the dominant frequency.

  According to the detonator 13 which is an electronic detonator, the detonation second time difference can be set in the field only in 1 ms units, so that the detonation second time difference that can avoid resonance with the vibration frequency at the points P1 and P2 can be avoided. Can be set. Since the electron detonator has high coincidence, it is possible to clearly separate the blast time between the current initiation hole and the next initiation hole.

  And the single blasting by the several detonation holes 20 and the stage blasting by the detonation hole group B1-B6 in the set detonation second time difference are performed continuously. Thus, the blasting process of this embodiment is implemented.

  In addition, it is not restricted to repeating the combination of single shot blasting and stage blasting every time, for example, single shot blasting may be incorporated only once out of two blasting. In setting the time difference of the detonation seconds, it is not limited to the case of using the prevailing frequency by the single shot blasting immediately before, and the prevailing frequency obtained by the single shot blasting two or more times before may be used. In tunnel excavation, the distance traveled at one time is, for example, 1 to 2 m. From the viewpoint of the distance between the point P1 or the point P2 and the ground conditions, the previous face A and the current face A Can be considered to be in the same position. That is, the single blasting is not required for the section in which the dominant frequencies at the points P1 and P2 are assumed to be the same.

  Further, the single blast and the step blast may not be performed continuously but may be performed separately. That is, in order to grasp the dominant frequency at the point P1 or the point P2, single shot blasting without step blasting may be performed.

  In the blasting method according to the present embodiment, the time difference between detonation seconds for blasting is 30 ms or less. If the time difference between the start-up seconds is too large, the frequency f indicating the high vibration value generated by the stage blasting becomes small, and it becomes difficult to set a peak frequency different from the dominant frequency at a predetermined point. It is preferable that the time difference between detonation seconds for burst blasting is 10 ms or less, more preferably 7 ms or less. The prevailing frequency of vibration generated at a predetermined point in the vicinity of tunnel blasting is distributed in the range of 50 to 150 Hz, and most of the frequency is distributed in the range of 80 to 120 Hz. Therefore, the time difference between the initiation seconds is set to 10 ms or less, more preferably 7 ms. By setting to the following, it becomes unnecessary to consider a multiple (twice or more) of the frequency f indicating a high vibration value of vibration generated by step-by-step blasting.

  On the other hand, it is preferable that the time difference between detonation and blasting is greater than 3 ms. If the time difference between the initiation seconds is too small, the frequency f indicating a high vibration value of vibration generated by stage blasting increases and the vibration value increases. The time difference between initiation seconds is more preferably 5 ms or more.

  In the blasting method of the present embodiment, the total initiation time can also be shortened by setting the time difference between initiation and detonation times of step blasting short. The total detonation time can be shortened while ensuring a predetermined number of steps in blasting. The total detonation time for blasting is set to 5 sec or less. The total detonation time for step-by-step blasting is preferably set to 3 sec or less. This is because if the total detonation time for step-by-step blasting is too long, the vibration time due to blasting also becomes longer.

  According to the blasting method of the present embodiment, a dominant frequency at the predetermined point P1 or the predetermined point P2 of vibration transmitted between the face A and the predetermined point P1 or the predetermined point P2 is obtained in advance, and a peak frequency different from the dominant frequency is obtained. The face A is stepped and blasted with the time difference of the detonation seconds set so as to occur. Thus, since the dominant frequency at the predetermined point P1 or the predetermined point P2 is measured in a state where the positional relationship between the face A and the predetermined point P1 or the predetermined point P2 is determined, the position of the face A changes. In addition, the dominant frequency is accurately measured under a distance or ground condition corresponding to the positional relationship. Therefore, when the face A is blasted and blasted, resonance between the peak frequency caused by the time difference between the start-up seconds and the dominant frequency at the predetermined point P1 or the predetermined point P2 is avoided, and as a result, at the predetermined point P1 or the predetermined point P2. The resulting vibration is reduced.

  As described above, in the present embodiment, the peak frequency of the vibration of the stage blasting is adjusted arbitrarily by adjusting the timing of the detonation seconds using the high accuracy of the detonation time difference of the electron detonator (in other words, the distance and The effect of reducing vibration is enhanced by shifting from the dominant frequency inherent to the ground conditions). This idea is a technical idea different from the conventional blasting method which tried to reduce vibration by superimposing (interference) vibration waveforms. Although it is theoretically possible to reduce vibration by superimposing vibration waveforms, it has been difficult to actually realize it. In this respect, in the present embodiment, vibration can be reduced by simple control of removing the peak frequency from the dominant frequency, and therefore, practicality and versatility are high as compared with the conventional blasting method.

  As tunnel excavation progresses, the position of face A changes, but even if there are residences (ground structures) 1 and 2 (see FIG. 1) that are security properties at predetermined points P1 and P2 around tunnel TNL, residence 1 or The dominant frequency at the point P1 or the point P2 of the residence 2 is measured in accordance with the progress of the tunnel excavation. Therefore, according to the progress of tunnel excavation, the influence of vibration on the dwelling 1 or dwelling 2 at the predetermined point P1 or the predetermined point P2 is reduced. In addition, since at least one single blast and step blast are continuously performed, tunnel excavation by stage blasting is performed, and the appropriate time difference between the start-up seconds corresponding to the position of the face A at that time is achieved by single blasting. Can be set. That is, since the vibration propagation path and propagation distance are the same for both blasts (single blast and step blast), the frequency can be easily evaluated. Therefore, the vibration generated at the predetermined point P1 or the predetermined point P2 is reliably reduced in accordance with the progress of the tunnel excavation.

  In addition, an interval of 100 ms or more is provided between single blasting and step blasting. By providing an interval of 100 ms or more between single blasting and step blasting, it is possible to eliminate the influence of stage blasting on the measurement of the dominant frequency at a predetermined point. When the interval is short, the vibration caused by the single blast and the vibration caused by the step blast are overlapped when measuring the dominant frequency at a predetermined point of the vibration caused by the single blast, and the measurement of the dominant frequency cannot be performed accurately.

  If the time difference between the detonation seconds is 10 ms or less and the total detonation time of the stage blasting is 3 sec or less, the vibration generated at the predetermined points P1 and P2 is reduced, and the vibration is generated at the predetermined point P1 or the predetermined point P2. The time spent is shortened.

  In addition, increasing the peak frequency (that is, reducing the time difference between initiation seconds) increases the distance attenuation (that is, the distance attenuation is likely to occur at high frequencies). In this case, by reducing the time difference between the explosion seconds, the overall blasting duration can be shortened, and the influence on the surrounding environment (for example, a residence, a private house, etc.) can be reduced. In addition, if there is a concern about vibration amplification due to superposition of each vibration waveform by reducing the time difference between initiation seconds, the amplification degree due to wave interference can be confirmed each time by comparing with the vibration amplitude value of single vibration.

  In addition, since the peak frequency is obtained by making the reciprocal of the time difference of the detonation seconds or a multiple of the reciprocal of the time difference of the detonation seconds, the detonation that can avoid resonance between the peak frequency and the dominant frequency at the predetermined point P1 or the predetermined point P2. The time difference in seconds can be set easily.

  4 and 5 are diagrams showing a blasting method according to another embodiment of the present invention. In this embodiment, in the step of measuring the dominant frequency, the dominant frequency at each of the predetermined points P1 and P2 of vibration caused by single blasting of the face A is measured. Then, in the step of setting the detonation second time difference, two or more types of detonation second time differences corresponding to each of the predetermined points P1 and P2 are set, and in the step of performing step blasting, the face A is made to correspond to each of the predetermined points. Are divided into two (first section A1 and second section A2), and the first section A1 and A2 are staged and blasted.

  More specifically, as shown in FIG. 5, the stage blasting in the first section A1 (illustrated left-type detonation hole groups B2 to B6) and the stage blasting in the second section A2 (detonation on the road side shown in the figure) The time difference between the initiation seconds is set individually for the hole groups B2 to B6).

  The face A is divided according to the positional relationship between the predetermined points P1 and P2. For example, in order to correspond to the point P1 located on the left side of the tunnel TNL and the point P2 located on the right side, the face A may be sectioned vertically in the center, and the section of the face A may not be equal left and right. Moreover, you may divide into multiple in the circumferential direction from the lower side of a tunnel center.

  Also by such a blasting method, the same effect as the blasting method of the previous embodiment is exhibited. In addition, the prevailing frequency is measured for each of two or more points P1 and P2, and the time difference between the start face A and each point P1 and P2 is different because the explosive second time difference is set for each of sections A1 and A2. However, taking these conditions into account, the time difference between the detonation seconds is set. Therefore, vibration can be reduced at each of the points P1 and P2.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the setting of the detonation second time difference in the stage blasting is not limited to the equidistant detonation second time difference. For example, the peak frequency of vibration due to step-by-step blasting may be prevented by generating a prime time difference of 3 ms, 5 ms, 7 ms, 11 ms, 13 ms, etc.

Example 1
Vibration test by blasting was conducted in actual tunnel excavation. In Example 1, the dosage per initiation hole was about 800 g. The interval between single blasts and the interval between single blasts and stage blasts was 500 ms. The distance from face A to the vibration measurement point was 36 m.

  As shown in FIGS. 7A to 7C, the dominant frequency measured in single blasting was 112 to 136 Hz. On the other hand, the number of explosion holes for staged blasting is 92 holes, the dose per hole is about 800 g, and the time difference between each initiation is 5 ms (the peak frequency that is the reciprocal of the time difference between initiations is 200 Hz). Set. The peak frequency was removed to the higher side with respect to the dominant frequency. As a result, as shown in FIG. 6, the maximum vibration value was 0.356 cm / s. As shown in FIG. 8, there was no amplification of the vibration value in the stage blasting. It should be noted that in order to reduce the vibration generated in the vicinity due to the stage blasting, it was important not to cause the vibration value to be amplified. It was found that staged blasting with a large second time difference generally tends to amplify vibration values.

  In the measurement of the dominant frequency of vibration caused by single blasting, the dominant frequency could be measured well without the influence of step blasting. In addition, the total detonation time for step-by-step blasting is about 500 ms. The arrangement of the initiation holes in the staged blasting is as shown in FIG. 2, and one hole in the figure corresponds to two initiation holes in the staged blasting.

(Example 2)
In Example 2, prior to Example 1, single blasting was performed at a point where the distance from the face A to the vibration measurement point was 80 m. The dose per initiation hole was 800 g. The dominant frequency measured in a single blast was 102-118 Hz. On the other hand, the explosion time difference of the stage blasting was set to 7 ms (the peak frequency which is the reciprocal of the explosion time difference was about 142 Hz), and the explosion was carried out in the same manner as in Example 1. As a result, as in Example 1, amplification of vibration value due to step-by-step blasting was not observed.

(Example 3)
In Example 3, single-shot blasting (three times) and step-by-step blasting with an explosive second time difference of 10 ms were performed. The distance from face A to the vibration measurement point was 34 m. This distance is not significantly different from the distance when Example 1 is performed. The charging conditions are substantially the same as in Example 1. The interval between single blasts was 500 ms, and the interval from the third single blast to the start of stage blast was also 500 ms. In addition, the total detonation time for step-by-step blasting is about 1000 ms.

  As can be seen from FIGS. 7A to 7C, the dominant frequency measured by single blasting at this point is about 112 to 136 Hz. On the other hand, the peak frequency was removed to the lower side with respect to the dominant frequency by setting the time difference of the initiation time of 10 ms (ie, the peak frequency was 100 Hz). As a result, as shown in FIG. 9, the maximum vibration value was 0.483 cm / s. Further, as shown in FIG. 10, the frequencies in the stage blasting are overlapped in the vicinity of 100 Hz, which is considered to have led to the amplification of the vibration value. Thus, when the dominant frequency was close to the peak frequency set by the time difference between the initiation seconds, the vibration value tended to increase.

Example 4
In Example 4, the face A passed through the vicinity of the vibration measurement point, and single blasting was performed at a point where the distance from the face A to the vibration measurement point reached 80 m. The dose per initiation hole was 800 g. The dominant frequency measured in a single blast was 102-118 Hz. On the other hand, the explosion time difference of the stage blasting was set to 7 ms (the peak frequency which is the reciprocal of the explosion time difference was about 142 Hz), and the explosion was carried out in the same manner as in Examples 1 and 2. As a result, as in Examples 1 and 2, amplification of vibration value due to step-by-step blasting was not observed.

  From the above results, in general, under the same ground conditions, the dominant frequency decreases as the distance from the face A to the vibration measurement point increases, and the dominant frequency decreases as the distance from the face A to the vibration measurement point decreases. Tended to be larger. When such a tendency is observed, the time difference between the start of the excavation seconds decreases as the vibration measurement point approaches the face A, and the time difference between the vibration measurement points moves away from the face A according to the progress of the tunnel excavation. Can be increased.

  In the face A where the distance to the vibration measurement point was 35 m, single blasting (3 times) and step-by-step blasting with an explosive second time difference of 3 ms were performed, and the maximum vibration value was 1.05 cm / s. The dominant frequency determined from the ground conditions was around 90 Hz. However, since the time difference between the explosion and the explosive seconds was reduced to 3 ms, the vibration speed was thought to have increased due to the overlapping of the waveforms between the stage blasts.

(Example 5)
In Example 5 of the tunnel with different ground conditions, the dominant frequency was measured at each of the predetermined points P1 and P2 as shown in FIG. The dose per initiation hole was about 1000 g. The point P1 is located on the left side toward the face A, and the point P2 is located on the right side toward the face A. The distance from face A to point P1 was 100 m, and the distance from face A to point P2 was 60 m. The dominant frequency measured in single blasting was 66-74 Hz at point P1, and 96-108 Hz at point P2.

  Then, in the step of setting the time difference between the blasting blasts, the face A is associated with the point P1 (left side) and the point P2 (right side), and is divided into two vertically in the center as shown in FIG. The left side was set as section A1, and the right side was set as section A2. In the setting of the initiation time difference, the displacement was made to the initiation hole 42 in the category A1, the amount per initiation hole was about 1000 g, and the initiation time difference for each initiation was set to 10 ms. On the other hand, with respect to 42 initiation holes in section A2, the amount per initiation hole was about 1000 g, and the initiation time difference between each initiation was set to 7 ms. Blasting was performed under the above conditions. As a result, Comparative Example 1 in which the amount per unit of the initiation hole is set to 1000 g with respect to the 42 symmetrical opening holes, and each of the symmetrical opening holes is set to 10 ms of the initiation time difference, and the symmetrical opening hole. The maximum vibration values were reduced to 1/5 and 1/4, respectively, with respect to Comparative Example 2 in which each of these was set to a detonation second time difference of 7 ms.

  10 ... detonation holes (detonation holes for blast blasting), 20 ... detonation holes (detonation holes for single blasting), 12 ... explosives, 13 ... detonator, A ... working face (blasting target area), A1 ... first division, A2 ... second section, P1, P2 ... point (predetermined point), TNL ... tunnel.

Claims (6)

It is a blasting method that reduces vibrations that occur at a predetermined point around the blasting target area,
Measuring a dominant frequency at the predetermined point of vibration caused by a single blast of the blast target region;
Setting the detonation second time difference of stage blasting so that a peak frequency different from the dominant frequency is generated;
And a step of performing stepwise blasting of the blasting target region with the time difference of the explosion seconds. The blasting target area is a face in tunnel excavation,
The blasting method according to claim 1, wherein at least one single-shot blast and the step-by-step blast for measuring the dominant frequency are continuously performed.   The blasting method according to claim 2, wherein an interval of 100 ms or more is provided between the at least one single blast and the step blast. The predetermined point is two or more points,
In the step of measuring the dominant frequency, the dominant frequency at each of the predetermined points of vibration caused by single blasting of the blasting target region is measured,
In the step of setting the detonation second time difference, two or more types of detonation second time differences corresponding to each of the predetermined points are set,
The step of blasting and blasting divides the blasting target region in correspondence with each of the predetermined points, and performs blasting and blasting of each category with a set time difference of detonation. The blasting method described in one item.   The blasting method according to any one of claims 1 to 4, wherein a time difference between the initiation seconds is 10 ms or less, and a total initiation time for the staged blasting is 3 seconds or less.   In the step of setting the detonation second time difference, the peak frequency is obtained by setting the reciprocal of the detonation second time difference or a multiple of the reciprocal of the detonation second time difference as claimed in any one of claims 1 to 5. Blasting method.

Images