JP3917730B2 - Blasting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is particularly, by applying the blasting how that can dissipate excess pore water pressure caused when performing blasting at high soft ground underground water level in a short time, ground vibrations in a specific direction out of the ground vibration by blasting It is related with the blasting method which can reduce.
[0002]
[Prior art]
Regarding the compaction of loose sand ground by blasting, there have been many examples of construction mainly in Europe and North America. The present inventors have examined the application of the compaction method by blasting to soft ground such as a landfill or a reclaimed land in Japan.
[0003]
[Problems to be solved by the invention]
However, when blasting is performed on soft ground, when viscous soil is confined, viscous soil is distributed near the ground surface, or in the case of ground with a lot of fine particles, the pore water pressure is increased by the explosion energy of blasting. Is increased, resulting in the following problems.
[0004]
In other words, in order to prevent the occurrence of blasting pollution such as noise and ground vibration, drill multiple blast holes in the ground and install explosives in each blast hole, or install multiple explosives in one blast hole. It is necessary to install them at different depths and to explode each explosive in sequence and blast them in stages. However, if the next stage blasting is performed before the pore water pressure that has become excessive due to the blasting has been dissipated, the compaction effect due to the next stage blasting will be reduced. In addition, in view of this point, in order to make the effect of blasting at each stage sufficient, the next stage of blasting is performed after the excess pore water pressure is dissipated at each blasting and the ground is stabilized. In that case, it takes a long time for the blasting operation.
[0005]
On the other hand, as is well known, when there are houses around the site, ground vibration due to blasting becomes a problem. Moreover, since the vibration generated in a soft ground is hard to attenuate compared to a hard ground or a rocky mountain, a large vibration propagates a considerable distance. Therefore, especially in soft ground, it is necessary to reduce ground vibration due to blasting in a specific direction (such as a direction where a house is located).
[0006]
Therefore, a main object of the present invention is to solve the problems described above, the excess pore water pressure caused when performing blasting at high soft ground underground water can be dissipated in a short time Rutotomoni, ground vibration by blasting Is to propose a blasting method capable of reducing ground vibration in a specific direction.
[0007]
[Means for Solving the Problems]
This onset bright in which the above-described problems, the blasthole is drilled to below the groundwater level in the soft ground, we established the explosives groundwater level below the depth in the blasthole, a vicinity of the blasthole, And at least one pore water pressure dissipation hole is provided in the ground on the side to reduce ground vibration so as to extend below the groundwater level , and blasting using the blasting hole,
Prior to the blasting, groundwater in the pore water pressure dissipation hole is drained to the ground side to forcibly reduce the groundwater level near the pore water pressure dissipation hole, thereby reducing ground vibration caused by the blasting.
A blasting method characterized by that.
In the present invention, it is preferable that the pore water pressure dissipation hole has an inner diameter of 50 to 100 mm and a distance from the blast hole of 100 to 200 cm .
[0008]
[Action]
When the pore water pressure dissipation hole is provided in the ground around the blast hole according to the present invention, the pore water pressure in the nearby ground becomes excessive due to the impact force of blasting, but this excess pore water pressure is quickly dissipated in the pore water pressure dissipation hole . Therefore, install explosives in multiple blast holes, install multiple explosives in one blast hole at different depths, and explode each explosive in sequence, blasting in multiple steps. Even when it is performed, the next stage of blasting can be performed in a shorter time, and the blasting operation becomes quicker.
[0009]
In soft ground with high groundwater level, ground vibration due to blasting propagates with pore water as the main vibration medium. Therefore, by providing at least one pore water pressure dissipation hole in the ground near the blasting hole and reducing ground vibration, it is possible to reduce the ground vibration in a specific direction, that is, the pore water pressure dissipation hole side. it can.
[0010]
Furthermore , prior to blasting, if the groundwater in the pore water pressure dissipation hole is drained to the ground side and the groundwater level near the pore water pressure dissipation hole is forcibly lowered, the excess pore water pressure generated by the blasting is dissipated more quickly, and The ground vibration reduction effect is also improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of a blasting method in which a pore water pressure dissipating portion 2 is provided in the ground around the blasting hole 1 when performing blasting using the blasting hole 1 drilled in the ground (hereinafter referred to as a first specific example). Called).
[0012]
Pore pressure dissipation unit 2, Ru provided by drilling the pore pressure dissipation hole 2 A so as to extend up to at least the groundwater level below the surrounding ground of the blasthole 1. The inner diameter and depth of the pore water pressure dissipation hole 2 </ b> A can be determined as appropriate. For example, the inner diameter can be about 50 to 100 mm, and the depth can be the same as the depth of the blast hole 1. Also, in soft ground with high groundwater level, the pore water pressure dissipation hole 2A is not self-supporting until after drilling or blasting, so as shown in the figure, gravel material or the like is formed in the entire dissipation hole 2A (from the bottom to the hole opening). It is desirable to fill the water-permeable material 3. Further, although not shown, a perforated pipe can be built in the dissipation hole 2A so that the hole is positioned at least below the groundwater level. In these cases, the self-supporting of the hole can be assisted by building a non-porous pipe (or a perforated pipe) made of paper, polystyrene foam or the like at an appropriate interval for the portion above the groundwater level.
[0013]
On the other hand, in the illustrated example, the blast hole 1 is drilled to a level below the groundwater level, and an explosive 4 in which a detonator and a leg line (not shown) are arranged is installed at a depth below the groundwater level in the blast hole 1. .
[0014]
When blasting is performed in this example, the pore water pressure becomes excessive due to the impact force of the explosion under the groundwater level, the particle accumulation structure in the surrounding ground is destroyed, and liquefaction occurs in the ground. Then, the ground is compacted as the ground constituent particles are redeposited and the pore water pressure returns to the normal state. At this time, due to the excess pore water pressure, the groundwater quickly permeates into the water permeable material 3 of the portion having better water permeability, that is, the pore water pressure dissipation portion 2. As a result, excess pore water pressure caused by blasting will be dissipated in a short time. Therefore, install explosives in multiple blast holes, install multiple explosives in one blast hole at different depths, and explode each explosive in sequence, blasting in multiple steps. Even when it is performed, the next stage blasting can be performed in a shorter time, and the blasting operation can be performed quickly.
[0015]
Next, FIG. 2 shows an example of a blasting method in which a plurality of blast holes 1, 1... Are drilled in the ground, and pore water pressure dissipating portions 2, 2 are provided in the ground between these blast holes 1, 1.. (Hereinafter referred to as a second specific example). 4 in the figure indicates explosives. A plurality of blast holes 1, 1... Can be provided in a matrix in a plan view as shown in FIG. 3, for example. In this case, a pore water pressure dissipating portion is provided at the center of the four adjacent blast holes 1, 1. 2, 2, ... are preferably provided. Further, the pore water pressure dissipating part 2 in the second specific example cuts the pore water pressure dissipating hole 2A in the same manner as the first specific example described above, and fills the entire hole with the water permeable material 3 such as gravel material. Etc. can be provided.
[0016]
When blasting is performed using a plurality of blast holes as in the second specific example, by providing pore water pressure dissipating portions 2, 2... Between these blast holes 1, 1,. The excess pore water pressure generated can be effectively dissipated in a short time, so that even when blasting continuously in a short time, the ground can be more effectively compacted. .
[0017]
4 and 5 show examples of blasting methods in which pore water pressure dissipating parts 2 and 2 are provided in the ground near the blasting holes 1, 1... Drilled in the ground and on the side where ground vibration is reduced. (Hereinafter referred to as a third specific example). In this example, a plurality of pore water pressure dissipating parts 2, 2... Are provided so as to be spaced apart from the blast hole by about 100 to 200 cm as shown in the illustrated example, or in the circumferential direction around the blast hole on the ground to reduce ground vibration. It is proposed that the central angle θ from one end to the other end be 90 to 120 degrees. Further, the pore water pressure dissipating parts 2, 2... Can be arranged in a straight line as shown in FIG. 4, or can be arranged in an arc shape around the blast hole as shown in FIG. Further, although not shown, the pore water pressure dissipating portions 2, 2... On the other hand, although not shown in the figure, a straight line or an arc-shaped groove centered on the blast hole is dug in the ground to reduce the ground vibration, and a water-permeable material such as gravel material is filled in the groove. It is also possible to provide an arc-shaped pore water pressure dissipating portion centering on the shape or blast hole. In the third specific example, the pore water pressure dissipating part 2 also has the necessary number of pore water pressure dissipating holes 2A as in the first specific example and the second specific example described above, and a gravel material or the like is formed throughout the hole. The water-permeable material 3 can be filled.
[0018]
As described above, in soft ground with high groundwater level, ground vibration due to blasting propagates with pore water as the main vibration medium. That is, ground vibration due to blasting propagates as an excess portion and a non-excess portion of pore water pressure. Therefore, as shown in the third specific example, pore water pressure dissipating parts 2, 2... Are provided in the vicinity of the blast holes 1, 1. As a result, ground vibration due to blasting is reduced by dissipation of excess pore water pressure in the pore water pressure dissipation portions 2, 2.
[0019]
And in the present invention, in these first to third embodiments, in order to further improve the pore pressure dissipation effect and ground vibration reducing effect, the groundwater level pore pressure dissipation unit 2 near reduces forced by pumping groundwater The In this case, the water collection and drainage device used for the well point method can be used as it is. That is, as shown in FIG. 6, a pore water pressure dissipation hole 2A is drilled around the blasting hole 1, and a well point 10 is installed in the dissipation hole 2A and a water permeable material 3 such as gravel is filled. The pore water pressure dissipating part 2 is provided, the upper end side of the well point 10 is connected to the ground drainage device 11, groundwater is collected from the well point 10 by this drainage device 11, and drained to the ground side, so that the pore water pressure The groundwater level near the dissipating part 2 is forcibly lowered. In the figure, 4 indicates an explosive . Then, the forced lowering of the groundwater level of this is, intends row prior to blasting.
[0020]
In this way, if the groundwater level near the pore water pressure dissipation part is forcibly lowered by, for example, pumping up the groundwater, the excess pore water pressure generated by blasting is dissipated more quickly at the pore water pressure dissipation part, thus improving the ground vibration reduction effect. To do.
[0021]
【The invention's effect】
As described above, according to the present invention, in a high soft ground underground water can be dissipated in a short time the excess pore water pressure caused when performing blasting Rutotomoni, ground vibrations in a specific direction out of the ground vibration by blasting Can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a first specific example of the present invention.
FIG. 2 is a diagram schematically showing a second specific example of the present invention.
FIG. 3 is a diagram showing the arrangement of blast holes and pore water pressure dissipation holes in a second specific example.
FIG. 4 is a diagram showing the arrangement of blast holes and pore water pressure dissipation holes in a third specific example.
FIG. 5 is a diagram showing the arrangement of other blast holes and pore water pressure dissipation holes in the third specific example.
FIG. 6 is a diagram schematically showing an example of forcibly lowering a groundwater level.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Blast hole, 2 ... Pore water pressure dissipation part, 2A ... Pore water pressure dissipation hole, 3 ... Permeable material, 4 ... Explosive, 10 ... Well point, 11 ... Drainage device.

Claims (2)

Drill a blast hole in soft ground to below the groundwater level, install explosives at a depth below the groundwater level in the blast hole, and close to the ground near the blast hole and reduce ground vibration. A method of providing at least one pore water pressure dissipation hole so as to extend below the groundwater level , and performing blasting using the blasting hole,
Prior to the blasting, groundwater in the pore water pressure dissipation hole is drained to the ground side to forcibly reduce the groundwater level near the pore water pressure dissipation hole, thereby reducing ground vibration caused by the blasting.
A blasting method characterized by that. The blasting method according to claim 1, wherein an inner diameter of the pore water pressure dissipation hole is 50 to 100 mm, and a distance from the blasting hole is 100 to 200 cm.

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