CN113465461B - Large-section tunnel blasting hole-reducing layout method - Google Patents
Large-section tunnel blasting hole-reducing layout method Download PDFInfo
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- 238000005422 blasting Methods 0.000 title claims abstract description 97
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F42—AMMUNITION; BLASTING
- F42D—BLASTING
- F42D1/00—Blasting methods or apparatus, e.g. loading or tamping
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/006—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries by making use of blasting methods
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F42—AMMUNITION; BLASTING
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- F42D1/08—Tamping methods; Methods for loading boreholes with explosives; Apparatus therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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Abstract
The invention discloses a large-section tunnel blasting hole-reducing layout method, which is characterized by comprising the following steps of: the method sets the opening position of the wedge-shaped cut hole at a position which is at a minimum distance d1 from the design contour line of the tunnel, and at the moment, the reserved rock mass outside the design contour line cannot be damaged during the blasting of the wedge-shaped cut hole; and then carrying out wide hole spacing hole distribution on the surrounding rock at the center of the face separated by the pre-cracks, then carrying out tunnel auxiliary hole distribution by adopting a step blasting wide hole spacing small row spacing hole distribution mode, and finally carrying out peripheral hole distribution by adopting an oblique angle mode.
Description
Technical Field
The invention relates to the technical field of large-section tunnel excavation, in particular to a blasting hole-reducing layout method for a large-section tunnel.
Background
With the rapid development of economic society, the traditional small-section tunnel cannot meet the requirement of highway transportation, and large-section tunnels such as three lanes and four lanes are widely used in the highway built in recent years. The drilling and blasting method has the advantages of high efficiency and economy, is a main method for tunnel excavation in China, but if blasting hole meshes of a large-section tunnel are distributed according to a traditional method, the number of drilled holes is increased, the drilling cost is increased, and the project progress is influenced.
The arrangement of the blast hole meshes is always a research hotspot of tunnel blasting, and a large number of expert scholars carry out a plurality of researches on the arrangement: the blasting action mechanism of the distance between the blast holes and the empty holes on the rock mass is researched by thunder warfare and the like, the fracture guide effect between the double blast holes and the empty holes on two sides under different distances between the empty holes and the blast holes is obtained, and the stress change rule of the measuring points around the empty holes is analyzed. Lihongwei and the like research the influence rule of different blast hole distances on the expansion of explosive cracks of rocks (hornrocks). Trade-trade et al studied the effect of the distance between peripheral holes on smooth blasting effect from the principle of blasting, fracture mechanics and empirical methods in order to calculate the distance between peripheral holes suitable for engineering blasting. The single-core light provides a quasi-straight-hole cutting mode, overcomes the defects of straight-hole cutting and inclined-hole cutting, and improves the rock drift tunneling speed. The method is characterized in that the residual strength and the like are calculated according to a blasting theory and an empirical formula, and the selection of reasonable undermining modes, blast hole depths and undermining hole arrangement parameters under the condition of the hard rock roadway is introduced by combining the specific conditions of a test working face. The damage of the rock in the blasting process is analyzed by the Zhang-March-Zengh method, the arrangement of blast holes in the blasting scheme is optimized by a numerical simulation method, and the field blasting effect is evaluated by a damage factor D. The numerical simulation is carried out on the coupled charging blasting process of the peripheral holes by Shuyanming and the like, so that the more reasonable blast hole spacing of the peripheral holes is obtained, the disturbance to the surrounding rock is reduced as much as possible, and the normal collapse of the rock is ensured. The gentle-helping trees and the like optimize smooth blasting parameters, cut hole layout schemes and maximum single-hole loading parameters of tunnel excavation by developing field tunneling blasting tests and layered rock mass failure mechanism analysis, and control engineering problems of over excavation and tunnel face bottom underexcavation caused by easy delamination of tunnel arches due to blasting excavation. Wu megahua and the like researches the fracture expansion condition and the fracture ring range around the blast hole after deep hole blasting by adopting a method of combining theoretical analysis and numerical simulation. Liu catch on the equal study drilling machine of large cross section tunnel blasting, combine smooth blasting design principle, proposed the smooth blasting scheme that is applicable to the large cross section tunnel that adopts airleg rock drill drilling. Yaohou and the like provide a short-footage shallow hole weak blasting scheme, and solve the problem of stability of surrounding rock in the blasting process under the condition of water-rich soft surrounding rock. The research of Feihong and Lu and the like obtains a calculation formula which accords with the actual fracture zone range, analyzes the calculation method of the fracture zone range under the condition of air non-coupling charging, calculates the radius of the rock fracture zone existing in the initial damage and crushing zone, and considers the secondary expansion of the fracture under the quasi-static action of explosive gas by applying the Abel principle and the rock crack arrest condition on the basis.
The research solves a plurality of problems of a tunnel blasting operation field, the result is quite abundant, but along with the increase of the tunnel section, how to reduce the arrangement of blast holes is a scientific difficult problem to be solved urgently, and the research on the aspect of reducing the arrangement of holes is rarely reported.
Disclosure of Invention
The invention aims to provide a large-section tunnel blasting hole-reducing layout method, which is used for pushing outwards the positions of wedge-shaped cut holes to the maximum extent and releasing most of the tunnel faces in the center of a tunnel, verifying the blasting effect of the method by developing field test research, reducing the number of blast holes, improving the tunneling efficiency and ensuring the engineering quality so as to overcome the defects of the prior art.
In order to achieve the purpose, the invention provides the following technical scheme:
a large-section tunnel blasting hole-reducing layout method is characterized in that the opening position of a wedge-shaped cut hole is arranged at a position which is at a minimum distance d1 from a design contour line of a tunnel, at the moment, the reserved rock outside the design contour line cannot be damaged during wedge-shaped cut hole blasting, and a pre-crack is formed after the wedge-shaped cut hole blasting; and then carrying out wide hole spacing hole distribution on surrounding rocks at the center of the face separated by the pre-cracks, then carrying out tunnel auxiliary hole distribution by adopting a step blasting wide hole spacing small-row spacing hole distribution mode, and finally carrying out peripheral hole distribution by adopting an oblique angle mode, wherein the initiation sequence is carried out.
As a further scheme of the invention: the method for determining the value of the minimum distance d1 comprises the following steps: according to the detonation wave theory, when the columnar explosive bag is exploded under the condition of not coupling charging, the initial impact pressure on the rock wall of the blast hole is as follows:
in the formula: ρ is a unit of a gradient 0 Is density, g.cm-3; d1 is detonation velocity, m.s < -1 >; dc is the diameter of charge, and db is the diameter of blast hole; lc is the charge length, lb is the blast hole length; the detonation product impacts the wall of the explosive chamber to obviously increase the pressure, and n is an increase multiple;
according to the attenuation law of stress wave at specific distance
The formula for calculating the peak value of the radial compressive stress is as follows:
in the formula:
d1 is the distance from the calculated point to the center of the blast hole (i.e. the minimum distance from the opening position of the wedge-shaped cut hole to the design contour line of the tunnel in the invention), and r b The radius of the blast hole; the compressive strength of the surrounding rock of the current tunnel section is Rc when sigma is rmax <And Rc, the blasting can be considered not to damage the reserved rock mass outside the design contour line, so that the minimum distance d1 from the opening position of the wedge-shaped cut hole to the design contour line of the tunnel can be calculated.
Compared with the prior art, the invention has the beneficial effects that: the invention provides a large-section tunnel blasting hole-reducing layout method, which is used for determining the minimum distance d from a wedge-shaped cut hole to a tunnel design contour line 1 The surrounding rock at the center of the tunnel face and the peripheral holes of the tunnel are arranged at a wide hole distance, the number of drilled holes is greatly reduced, the construction efficiency is improved, the utilization rate of blast holes of each blast hole is improved, and the construction cost is greatly saved.
Drawings
FIG. 1 is a schematic diagram of a mesh arrangement in a conventional tunnel blasting method;
FIG. 2 is a schematic diagram illustrating the optimization of the detonation sequence in the present invention;
FIG. 3 is a schematic plan view of arrangement of upper-step blastholes in the invention;
FIG. 4 is a schematic view of the charge structure of the blast hole, the cut hole and the auxiliary hole in the invention;
figure 5 is a schematic of a peripheral hole charge configuration according to the present invention.
In the figure: 1. cut holes in conventional tunnel blasting; 2. auxiliary holes in conventional tunnel blasting; 3. peripheral holes in conventional tunnel blasting; 4. blasting with a center wide hole distance of the tunnel face; 5. pre-forming seams by blasting the cut holes; 6. blasting and breaking rock by using auxiliary holes; 7. blasting the peripheral holes to control the contour effect; 8. a tampon; 9. an explosive; 10. a detonator; 11. a detonating cord.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-4, the present invention provides a technical solution:
1. large-section tunnel hole-reducing layout method
1. Traditional hole distribution mode
The initiation sequence of the traditional tunnel blasting method is cut hole blasting, auxiliary hole blasting and peripheral hole blasting, the cut hole blasting is firstly carried out in the center of a face, a central rock mass of the face is extruded outwards to form a cavity, a free face is provided for the auxiliary hole blasting, when the auxiliary hole blasting is carried out, an explosion stress wave is reflected on the free face to form a tensile wave, the rock breaking effect is achieved, and finally the peripheral hole blasting is carried out to control the tunnel profile. The method is suitable for blasting of the small-section tunnel, and the number of blast holes is estimated according to the section area of the tunnel and the firmness coefficient of rocks:
for a large-section tunnel, taking IV-grade surrounding rock, a rock firmness coefficient f =6 and a tunnel section area S =150m2 as examples, the number of holes required to be drilled on the whole section reaches more than 170, and the drilling workload is huge. The current automatic tunnel drilling equipment is not mature and mainly depends on manual drilling, the drilling efficiency of workers is generally about 3 holes/hour (the hole depth is about 4.2 m), and the drilling time is about 4.5 hours per cycle calculated by 13 people in one drilling class. The traditional tunnel blasting method has the advantages that the mesh layout is shown in figure 1, the number of drilled holes is large, the punching time is long, and the requirements of large-section tunnel blasting on high efficiency and economy cannot be met.
2. Reducing hole layout method (see figure 2)
The aim of the cut blasting is to provide a free face for auxiliary hole blasting, reduce the clamping effect, enable the explosion stress wave to reflect and stretch rock breaking on the free face, and for large-section tunnel blasting, the cut holes are not necessarily distributed in the center of the tunnel face. A method for arranging the reducing holes of a large-section tunnel is provided according to the requirements of field blasting engineering, and as shown in figure 2, the method pushes the opening positions of wedge-shaped cut holes outwards to the minimum distance d from the design contour line of the tunnel 1 At the moment, the wedge-shaped cut hole blasting cannot damage the reserved rock mass outside the designed contour line. Firstly, wedge-shaped cut hole blasting is carried out to form a pre-crack, most surrounding rocks at the center of the face are separated from surrounding rocks at the periphery, the surrounding rocks at the center of the face separated by the pre-crack can be blasted at a wide hole distance, and the number of blast holes is reduced. Due to the existence of the pre-cracks, the explosion stress wave is reflected and stretched at the position, the total resistance of explosion is only the shearing resistance action of the bottom surface, the clamping action is greatly reduced, and the damage of the rock mass and the explosion vibration are reduced.
The method is characterized in that the minimum distance d is determined 1 The value of (2) can not only ensure that the rock mass is not damaged, but also furthest push the opening position of the wedge-shaped cut hole outwards. According to the detonation wave theory, when the columnar explosive bag is exploded under the condition of non-coupled charging, the initial impact pressure on the rock wall of the blast hole is as follows:
in the formula: rho 0 Is density, g.cm -3 ；D 1 M.s for detonation velocity -1 ；d c Is the diameter of the charge, d b The diameter of the blast hole; l. the c For the length of the charge, /) b The length of the blast hole is; the detonation product impacts the wall of the explosive chamber to obviously increase the pressure, and n is an increase multiple and takes a value of 8-11.
The number 2 rock emulsion explosive is selected for calculation, and the density rho 0 ＝1.24g·cm -3 Detonation velocity D1=4200m · s -1 Diameter of charge d c =32mm, diameter d of blast hole b =42mm, length of charge l c =2.4m, blast hole length l b =4.8m, the initial impact pressure P =535.25MPa to which the blasthole rock wall is calculated.
According to the attenuation law of stress wave at specific distance
The formula for calculating the peak value of the radial compressive stress is as follows:
in the formula:
d 1 to calculate the distance from the point to the center of the blast hole (i.e., the minimum distance from the opening of the wedge-shaped cut hole to the design contour of the tunnel in this embodiment), r b Is the radius of the blast hole.
According to the on-site geological exploration report, the surrounding rock of the research section is slate, the compressive strength Rc =25MPa, and when sigma is rmax <During Rc, the blasting can be considered not to damage the reserved rock mass outside the design contour line, so that the minimum distance d from the opening position of the wedge-shaped cut hole to the design contour line of the tunnel can be calculated 1 ＝2.96m。
Therefore, the opening positions of the wedge-shaped cut holes are arranged at the positions 2.96m away from the design contour line of the tunnel, the initiation sequence is optimized to control the tunnel contour through wedge-shaped cut hole blasting presplitting crack-blasting of the surrounding rock wide hole distance at the center of the tunnel face-blasting of the auxiliary hole wide hole distance and small row distance blasting rock breaking-peripheral hole blasting. On the basis of forming pre-cracks in the wedge-shaped cut holes, a design concept of step blasting wide-hole-pitch and small-row-pitch hole arrangement is introduced into large-section tunnel blasting, the arrangement of hole network parameters is increased, and the hole network arrangement is shown in figure 3.
2. Engineering background
1. Overview of the engineering
The white bamboo mountain tunnel is a separated extra-long tunnel, the right tunnel is 4404m long, the maximum buried depth is 323m, the left tunnel is 4358m long, the maximum buried depth is 318m, and the distance between the left and right measuring lines of the tunnel is 16 m-41 m. The tunnel is a herringbone slope tunnel, the right longitudinal slope is 2.0 percent to 1.35 percent, the left longitudinal slope is 2.0 percent to 1.35 percent in sequence. The lithology of the surrounding rock in the research section is medium weathering thin-medium thick layered tuff, and the grade of the surrounding rock is III-grade surrounding rock.
2. Idea of design (see FIG. 3)
1) Considering the structure of a field excavation trolley and the operability of manual drilling, the distance from No. 14 and No. 15 wedge cut holes to the design contour line of the tunnel is 2.96m, 6 pairs of horizontal wedge cut holes are arranged, the distance between the wedge cut holes is 0.6m, the inclination angle (the included angle with the face, the later-mentioned inclination angle is the included angle with the face) is 60 degrees, the hole depth is 4.8m, and the horizontal distance is 5.0m.
2) Two blast-relieving holes are distributed in the center of the tunnel face, large rocks are decomposed into small rocks, and the depth of the blast-relieving holes is 3m, and the distance between the blast-relieving holes is 1.0m.
3) The auxiliary holes are distributed in three rows, the row spacing is the same, the distance between the auxiliary holes is gradually reduced from inside to outside, the inclination angle is gradually increased, a large-spacing small-row-spacing blasting process is adopted, and the hole depth of the auxiliary holes is 4.2m.
4) The peripheral holes are uniformly distributed 600mm away from the third row of auxiliary holes, and are inclined at a certain angle to form an inclined angle for facilitating punching, the hole bottoms exceed the designed contour line by about 100mm, and the deviation contour line of the opening of the orifice is controlled within the contour line and is about less than 100 mm.
3. Engineering applications
A large-section tunnel hole-reducing laying blasting method field test is carried out by taking ZK19+ 984-ZK 19+954 sections of the white bamboo mountain tunnel as test sections, an upper step blast hole arrangement diagram is shown in figure 3, and specific blasting parameters are shown in table 1.
TABLE 1 blasting parameter table
Different loadings were used for different lithologies, the specific loadings are shown in table 2.
TABLE 2 different lithology charge for each blast hole
According to advanced geological forecast detection reports of the ZK19+ 984-ZK 19+954 sections of the white bamboo mountain tunnels, the lithology of the surrounding rock of the sections belongs to medium-hard rock, and the explosive loading of each blast hole is as follows: the explosive disassembly holes are 5 pieces multiplied by 0.3kg =1.5kg, and the linear explosive loading density is 0.5kg/m; 8 slotted holes are multiplied by 0.3kg =2.4kg, and the thread loading density is 0.5kg/m; 7 auxiliary holes are multiplied by 0.3kg =2.1kg, and the thread loading density is 0.5kg/m; 4 peripheral holes multiplied by 0.3kg =1.2kg, thread loading density 0.29kg/m; bottom holes are 7 pieces multiplied by 0.3kg =2.1kg, and thread loading density is 0.5kg/m.
The hole charge configuration is shown in fig. 4 and 5, and the initiation sequence is shown in table 3.
TABLE 3 detonation sequence
Blast hole blocking has a great influence on the blasting effect, when blasting is not blocked, most of the blasting energy is consumed in the air, larger air shock waves are generated, the rock mass is crushed less, reasonable blast hole blocking needs to be carried out, the blocking length is larger than 50cm, and the stemming made of sand and clay according to 4.
3. Blasting effect and analysis
1. Number of drilled holes
The ZK19+ 984-ZK 19+954 section of the white bamboo mountain tunnel is IV-grade surrounding rock, the coefficient of Pushi f =6, and the excavation is brokenThe area S =97.4m2 according to the empirical formula of the number of the traditional blast holes
And calculating that the number of holes required to be drilled on the whole section reaches 128, and according to the wide hole distance blasting design scheme of the large-section tunnel, the whole section of the section only needs to be drilled with 105 holes, and the number of drilled holes per cycle is reduced by 23. 13 workers on site drill holes by using 13 drilling machines, the drilling efficiency of the workers is about 3 holes/hour, the drilling time per cycle is about 3.3 hours according to the traditional blasting scheme, the drilling time per cycle is about 2.7 hours according to the blasting scheme designed herein, the drilling time per cycle is saved by 0.6 hour, and the drilling time of a full-line 59km tunnel is saved by about 8850 hours. For the extra-large section tunnels such as three lanes and four lanes, according to the large section tunnel wide hole distance blasting design scheme provided by the text, the number of drilled holes is greatly reduced, the drilling time is saved, and the construction efficiency is improved.
2. Utilization rate of blast hole
According to the large-section tunnel wide hole distance blasting design scheme provided by the text, 5 field blasting tests are carried out on the ZK19+ 984-ZK 19+954 sections of the white bamboo mountain tunnel, the utilization rate of blast holes is counted, and the results are shown in table 4.
TABLE 4 statistical table of blast hole utilization
As can be seen from table 4, the average blast hole utilization rate of the wedge-shaped cut hole is 82.1%, the average blast hole utilization rate of the remaining blast holes is 91.9%, the blast hole utilization rate of each blast hole is high, the sill can be reduced, the gun repairing caused by the sill can be avoided, the blasting quality is improved, and the construction progress is accelerated.
3. Control effect of overbreak and underbreak
And after each cycle of blasting is finished, measuring the overbreak and underexcavation of the tunnel by using a total station, wherein the result is shown in table 5, and counting the actual consumption of sprayed concrete, and the result is shown in table 6.
TABLE 5 statistical table of the overbreak and undermining conditions
TABLE 6 statistics table for concrete over-consumption
From the table 5 and the table 6, according to the large-section tunnel wide-hole-distance blasting design scheme provided herein, the overbreak thickness can be controlled within 15cm, the average overbreak square amount is 3.02m3/m, the average overbreak consumption of the spraying and mixing is 3.75m3/m, and the spraying and mixing overbreak rate can be controlled within 90%. The initial measurement and calculation result shows that the direct construction cost can be reduced by about 1500 yuan for every 10cm reduction of the tunnel, and the construction cost can be reduced by 8700 ten thousand yuan for the whole 59km tunnel.
4. Conclusion
In this embodiment, the sections ZK19+ 984-ZK 19+954 of the white bamboo mountain tunnel are taken as research objects, field test research is carried out, the number of drilled holes, the utilization rate of blast holes after blasting and the overbreak and underpass control effect are analyzed, and the following conclusions are obtained:
1) A large-section tunnel blasting hole-reducing layout method is provided, the minimum distance from a wedge-shaped cut hole to a tunnel design contour line is 2.96m, and the surrounding rock at the center of a tunnel face is blasted at a wide hole distance by adopting two blasting holes, so that the number of blasting holes is reduced.
2) According to the large-section tunnel blasting hole-reducing layout method, the number of holes drilled in each cycle is reduced by 23, the drilling time is saved by 0.6 hour, and the drilling time of a full-line 59km tunnel is saved by about 8850 hours. For the extra-large section tunnels such as three lanes and four lanes, the blasting scheme is arranged according to the reduction holes of the large section tunnel provided by the text, so that the number of drilled holes is greatly reduced, and the construction efficiency is improved.
3) The average blast hole utilization rate of the wedge-shaped cut hole is 82.1 percent, the average blast hole utilization rate of the rest blast holes is 91.9 percent, and the blast hole utilization rate of each blast hole is higher.
4) The over-excavation thickness is controlled within 15cm, the average over-excavation square volume is 3.02m3/m, the average over-consumption of spraying and mixing is 3.75m3/m, the over-consumption rate of spraying and mixing is controlled within 90%, and the expected reduction of the construction cost is about 8700 ten thousand yuan.
Those not described in detail in this specification are within the skill of the art.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.
Claims (1)
1. A large-section tunnel blasting hole-reducing layout method is characterized by comprising the following steps: the method comprises the steps that the opening position of a wedge-shaped cut hole is arranged at a position which is at a minimum distance d1 from a design contour line of a tunnel, at the moment, the reserved rock outside the design contour line cannot be damaged during blasting of the wedge-shaped cut hole, and a pre-crack is formed after blasting of the wedge-shaped cut hole; then, carrying out wide hole spacing hole distribution on surrounding rock at the center of the face separated by the pre-cracks, then carrying out tunnel auxiliary hole distribution by adopting a step blasting wide hole spacing small row spacing hole distribution mode, and finally carrying out peripheral hole distribution by adopting a deflection angle mode; the initiation sequence is that the wedge-shaped cut hole is blasted to form a pre-crack, the surrounding rock of the center of the tunnel face is blasted at a wide hole distance, the auxiliary hole is blasted and broken at a wide hole distance and a small row distance, and the peripheral hole is blasted to control the tunnel profile;
the determination method of the value of the minimum distance d1 comprises the following steps: according to the detonation wave theory, when the columnar explosive bag is exploded under the condition of non-coupled charging, the initial impact pressure on the rock wall of the blast hole is as follows:
in the formula: rho 0 Is density, g.cm -3 ；D 1 M.s for detonation velocity -1 ；d c Is the diameter of the charge, d b The diameter of the blast hole; l c For the length of the charge, /) b The length of the blast hole is; the detonation product impacts the wall of the explosive chamber to obviously increase the pressure, and n is an increase factor;
according to the attenuation law of stress wave at specific distance
The calculation formula of the peak value of the radial compressive stress is as follows:
in the formula:
d 1 for the minimum distance, r, from the design contour of the tunnel from the position of the opening of the wedge-shaped cut hole b The radius of the blast hole is; the compressive strength of the surrounding rock of the current tunnel section is Rc when sigma is rmax <During Rc, the blasting can be considered not to damage the reserved rock mass outside the design contour line, so that the minimum distance d from the opening position of the wedge-shaped cut hole to the design contour line of the tunnel can be calculated 1 。/>
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