CN110671984A

CN110671984A - Boulder blasting construction method

Info

Publication number: CN110671984A
Application number: CN201910973673.8A
Authority: CN
Inventors: 张兵; 王凯; 陈桥; 高会中; 韩伟锋; 郭璐; 王雅文; 王发民; 杨延栋; 赵海雷
Original assignee: State Key Laboratory of Shield Machine and Boring Technology; China Railway Tunnel Group Co Ltd CRTG
Current assignee: State Key Laboratory of Shield Machine and Boring Technology; China Railway Tunnel Group Co Ltd CRTG
Priority date: 2019-10-14
Filing date: 2019-10-14
Publication date: 2020-01-10

Abstract

The invention discloses a boulder blasting construction method, which comprises the following steps: setting blast hole positions, drilling construction, checking and accepting blast holes, processing explosive packages, charging blast holes, filling blast holes, blasting a network, warning on site, detonating, grouting and sealing holes. The invention realizes thorough blasting, small particle size of the boulder after blasting, no influence on the construction progress of the cutter head, reduction of damage to the cutter head, and prolongation of the service life of the cutter head, and adopts an underground blasting type blasting mode with high safety.

Description

Boulder blasting construction method

Technical Field

The invention relates to the technical field of shield construction, in particular to a boulder blasting construction method.

Background

In the process of excavating and breaking rocks by the shield tunneling machine, the boulder has high strength and wide distribution, the maximum strength reaches 110MPa, and if the bond strength between the boulder and the surrounding soil body is insufficient, the boulder rotates along with the cutter head to cause the damage to the cutter head and the cutter. And the rock breaking by utilizing the cutter head needs larger thrust, the requirement on the structural strength of the reaction frame is higher, and the cost is high.

In addition, if the particle size of the crushed stone is larger than the size of the opening of the grating or the sealing performance of the originating end opening is poor, the mud bin cannot be pressurized, so that the mud carrying capacity is poor, and the mud is easy to be discharged in a stagnation manner and block the bin.

In the construction process, the boulder is treated by firstly selecting a proper method according to the size, thickness, distribution and strength of boulders and bedrock protruding sections disclosed by geophysical prospecting and drilling, and mainly adopting mechanical treatment and blasting treatment on the boulder in a backfill area according to the current similar engineering experience and the actual situation of the engineering in China. But the mechanical treatment verticality is not well controlled, the treatment effect is not good, the required construction period is longer, and the construction progress is influenced. The existing blasting treatment causes the particle size of the boulder after blasting to be larger, the blasting is not thorough, and the cutter head and the construction progress are easy to damage.

Disclosure of Invention

In view of the above, the invention aims to provide a boulder blasting construction method aiming at the defects of the prior art, which realizes thorough blasting, small boulder particle size after blasting, no influence on the construction progress of a cutter head, reduction of damage to the cutter head, prolongation of the service life of the cutter head, and high safety by adopting an underground blasting type blasting mode.

In order to achieve the purpose, the invention adopts the following technical scheme:

a boulder blasting construction method comprises the following steps:

(1) setting the position of a blast hole: the arrangement range of the blast holes is larger than that of the boulder, the boulder blasting is divided into single-hole single blasting and porous single blasting, the blast hole position of the single-hole single blasting is set at the gravity center of the boulder, and the blast hole position of the porous single blasting is set in a quincunx or rectangular shape;

(2) drilling construction: drilling to a designed depth by a geological drilling rig in a vertical mode, removing broken stones, silt and slurry in blast holes, keeping the blast holes smooth, and burying PVC pipes in the blast holes; the bottom of the PVC pipe is provided with a plug, and the top of the PVC pipe is provided with a covering object for preventing sundries from entering; the drilling process is carried out in a mud wall protection mode;

(3) and (4) checking and accepting the blast hole: after the blast hole is drilled, the technician checks and accepts the blast hole, the blast hole is smooth up and down, the explosive package can be filled into the blast hole to be qualified, the hole forming protection is performed, and the explosive package can be filled for construction after the acceptance is qualified;

(4) processing the medicine package: the explosive package is divided into a single-section explosive package and a multi-section explosive package, wherein the single-section explosive package consists of an explosive section and a counterweight section, and the multi-section explosive package is formed by arranging a plurality of single-section explosive packages; a detonator is embedded in the explosive section;

(5) charging in blast holes: placing the explosive package in a blast hole, wherein when single-hole single body blasting is adopted, the explosive length in the blast hole is equal to the thickness of rock; when the porous single body blasting is adopted, drilling any one blast hole in two adjacent blast holes to the bottom surface of the boulder, and then charging the powder in the blast holes, wherein the distance from the upper surface of the charged powder to the top surface of the boulder is 100 mm; the distance from the bottom surface of the other blast hole to the bottom surface of the boulder is 100 mm, and the distance from the upper surface of the charge to the top surface of the boulder is 100 mm;

(6) filling blast holes: after the explosive package is in place, slowly pouring sand or broken stones into the blast hole, wherein the blocking length is more than 5 m;

(7) blasting the network: 1-7 sections of nonel millisecond detonators are adopted, the interval time of section delay is 25-50 ms, hole or row millisecond delay blasting is carried out, and the interval time of section is 25-50 ms, and hole or row by row blasting is carried out;

(8) and (3) on-site warning: arranging a protective layer on the ground above the boulder; after the connection and detection of the blasting network are finished, warning according to the designed safety distance and the safety requirement, and confirming that all personnel are outside the dangerous area, wherein the blasting warning range is 50m around the blasting area;

(9) detonating: contacting each warning point again, and issuing a detonation command after confirming no errors; after the blasting is finished, the warning command is removed after the technician checks that the scene is correct;

(10) grouting and hole sealing: and (4) grouting and sealing holes of the sleeve valve pipe at the position of the original blasting hole after blasting is finished, and reinforcing the broken rock stratum and the soil body.

Preferably, the maximum grain size of the stone after blasting the boulder is less than or equal to 0.3 m.

Preferably, the distance between adjacent blast holes in the porous monomer blasting in the step (1) is 0.8-1.2m, and the diameter of each blast hole is 89 mm.

Preferably, the weight section in the step (1) is filled with crushed stones, the density of the crushed stones is 1.5g/cm3, and the density of the explosive in the explosive package is 0.95-1.25g/cm 3.

Preferably, a multi-stage medicine package is used when the thickness of the boulder is 2m or more, and a single-stage medicine package is used when the thickness of the boulder is 2m or less.

Preferably, the protective layer comprises a protective plate and sand cladding layers respectively arranged above and below the protective plate; the protection plate comprises an iron plate and a wood balk arranged below the iron plate; the thickness of the sand cladding below the guard plate was 0.5 m.

Preferably, the grouting in the step (10) adopts cement grout, the water cement ratio is 1:1, and the grouting pressure is controlled to be 1.5 ~ 3 Mpa.

Preferably, 4 detonators are arranged in each blast hole.

Preferably, the explosive package is arranged in the blast hole positioned on the boulder, and the explosive package is not arranged in the blast hole outside the range of the boulder.

The invention has the beneficial effects that:

according to the method, the blast holes are firstly positioned, the arrangement range of the blast holes is larger than the range of the boulders, the effect of boulder blasting is favorably ensured, incomplete boulder blasting caused by inaccurate detected boulder edges is avoided, the blasted boulder fragment particles are overlarge, and the blasting range of the boulders is more clearly determined; drilling holes at the positions of the blast holes, wherein the depths of the adjacent blast holes are different, so that the construction is convenient, and the crushing effect of the boulder is improved; when row-by-row initiation is carried out, the front row holes are blasted firstly, then the front row holes are used for blasting and extruding the surrounding soil layer to generate impact force, and then the rear row holes are detonated one by one, so that the impact force caused by the whole initiation is reduced, and the broken stone or slurry is prevented from being sprayed out, so that the construction safety is improved; the PVC pipe is used for keeping the blast hole smooth and preventing sundries from entering the blast hole; because the slurry is arranged in the blast hole, in order to smoothly load the explosive package, a counterweight section is arranged in the explosive package, so that the problem that the explosive package cannot sink after being placed down or cannot be fixed under the action of buoyancy after sinking is solved; the setting when the explosive bag is filled in the blast hole can ensure the blasting effect and the safety of a construction site, prevent too much explosive from impacting too much and avoid too little explosive from causing poor blasting effect; the stability of the explosive package is improved by filling the explosive package above the explosive package in the PVC pipe, and the impact force of the explosive package during explosion is reduced; the arrangement of the blasting network is convenient for blasting operation among the explosive bags; the high-pressure gas generated after blasting presses the slurry out of the hole, the protective layer effectively prevents the PVC pipe from protruding and the slurry gushed from splashing, the construction controllability is improved, and the peripheral personnel are prevented from being accidentally injured; grouting is used to reinforce broken rock formations and soil.

The boulder crushing method has the advantages of strong controllability, thorough boulder crushing, high construction efficiency, strong safety, simple operation and good boulder crushing effect; the replacement frequency of the cutterhead in the tunneling process is indirectly reduced.

Drawings

FIG. 1 is a schematic diagram of a setting structure of a boulder blast hole;

FIG. 2 is a schematic view of a single segment package configuration;

FIG. 3 is a schematic diagram of a multi-segment drug package configuration;

FIG. 4 is a schematic view of a multi-segment cartridge installation;

FIG. 5 is a schematic view of a single section cartridge installation;

FIG. 6 is a schematic diagram of a hole-by-hole detonating circuit;

FIG. 7 is a schematic diagram of a bank-by-bank detonating network;

fig. 8 is a schematic view of a protective layer structure.

In the figure: 1 boulder, 2 blast holes, 3 counterweight sections, 4 explosive sections, 5 detonators, 6PVC pipes, 7 sand cladding, 8 iron plates and 9 wood purlin.

Detailed Description

The invention is further described below with reference to the figures and examples.

A boulder blasting construction method comprises the following steps:

(1) setting 2 positions of blast holes: as shown in fig. 1, the arrangement range of the blast holes 2 is larger than the range of the boulder 1, explosive charges are arranged in the blast holes 2 positioned on the boulder 1, and explosive charges are not arranged in the blast holes 2 outside the range of the boulder 1.

The boulder 1 blasting is divided into single-hole single blasting and multi-hole single blasting, the 2 position of a blast hole of the single-hole single blasting is set at the gravity center of the boulder 1, the 2 position of a blast hole of the multi-hole single blasting is set to be in a quincunx or rectangular shape, the distance between adjacent blast holes 2 in the multi-hole single blasting is 0.8-1.2m, and the diameter of the blast hole 2 is 89 mm.

(2) Drilling construction: drilling to a designed depth by a geological drilling machine in a vertical mode, removing broken stones, silt and slurry in the blast hole 2, keeping the blast hole 2 smooth, and burying a PVC pipe 6 in the blast hole 2; a plug is arranged at the bottom of the PVC pipe 6, and a covering object for preventing sundries from entering is arranged at the top of the PVC pipe; the drilling process is carried out in a mud wall protection mode;

(3) and (4) checking and accepting the blast hole 2: after the blast hole 2 is drilled, the technician checks and accepts, the blast hole 2 is smooth up and down, the explosive package can be filled into the blast hole to be qualified, the hole forming protection is performed, and the explosive package can be filled for construction after the acceptance is qualified;

(4) processing the medicine package: the medicine package is divided into a single-segment medicine package and a multi-segment medicine package which are respectively shown in figures 2 and 3; the single-section explosive package consists of an explosive section 4 and a counterweight section 3, and the multi-section explosive package is formed by arranging a plurality of single-section explosive packages; the counterweight section 3 is filled with crushed stone, the density of the crushed stone is 1.5g/cm3, and the density of the explosive in the explosive package is 0.95-1.25g/cm 3; 4 detonators 5 are arranged in each blast hole 2, and the detonators 5 are buried in explosives.

(5) Charging in a blast hole 2: placing the explosive package in the blast hole 2, wherein when single-hole single body blasting is adopted, the explosive length in the blast hole 2 is equal to the thickness of rock; when the porous monomer blasting is adopted, any one blast hole 2 in two adjacent blast holes 2 is drilled to the bottom surface of the boulder 1, then the powder is loaded in the blast hole 2, and the distance from the upper surface of the loaded powder to the top surface of the boulder 1 is 100 mm; the bottom surface of the other blast hole 2 is 100 mm away from the bottom surface of the boulder 1, and the distance from the upper surface of the charge to the top surface of the boulder 1 is 100 mm; a multi-stage medicine package (as shown in FIG. 4) is used when the thickness of the boulder 1 is 2m or more, and a single-stage medicine package (as shown in FIG. 5) is used when the thickness of the boulder 1 is 2m or less.

(6) Filling a blast hole 2: after the explosive package is in place, slowly pouring sand or broken stones into the blast hole 2, wherein the blocking length is more than 5 m;

(7) blasting the network: 1-7 sections of detonating tube millisecond detonators 5 are adopted, the interval time of section delay is 25-50 ms, hole-to-row or inter-row millisecond delay blasting is carried out, the interval time of section is 25-50 ms, hole-to-hole or row-to-row blasting is carried out, and blasting circuits which are detonated hole-to-hole or row-to-row are shown in figures 6 and 7.

(8) And (3) on-site warning: arranging a protective layer on the ground above the boulder 1, wherein the protective layer comprises a protective plate and sand cladding layers 7 respectively arranged above and below the protective plate as shown in fig. 8; the protection plate comprises an iron plate 8 and a wood balk 9 arranged below the iron plate 8; the sand cladding 7 located below the guard plate had a thickness of 0.5 m.

After the connection and detection of the blasting network are finished, warning according to the designed safety distance and the safety requirement, and confirming that all personnel are outside the dangerous area, wherein the blasting warning range is 50m around the blasting area;

(9) detonating: contacting each warning point again, and issuing a detonation command after confirming no errors; after the blasting is finished, the warning command is removed after the technician checks that the scene is correct; the maximum grain size of the stone after explosion of the boulder 1 is less than or equal to 0.3 m.

(10) Grouting and sealing holes, namely grouting and sealing holes of sleeve valve pipes at the original blasting hole position after blasting is finished, and reinforcing the broken rock stratum and the soil body, wherein the grouting adopts cement slurry, the water cement ratio is 1:1, and the grouting pressure is controlled to be 1.5 ~ 3 MPa.

The construction method is further explained:

1. the operation steps of the explosive charge and blasting network are as follows:

① processing the detonating body and filling explosive according to the design requirement;

after the explosive package is processed in place, drilling two holes in the upper part of the PVC pipe 6, binding the holes with iron wires, tying a rope on the upper part, starting to discharge the explosive package, and determining the bottom depth N of the explosive package according to the drilling parameters and acceptance conditions provided by drilling teams₁Then, the sum N of the lengths of the PVC pipe 6 and the rope is measured₂Make N be₁=N₂The whole bag is suspended at the correct position with the error controlled within +10 cm. After the cartridge is in place, the cable is secured to the wall of the casing with wire so that it is no longer free to move.

② checking whether the explosive reaches the designed position with a measuring string, if not, pressing and conveying to the required position with a gun stick;

③ filling the upper part of the blast hole 2 with a sand cylinder after filling the explosive;

④ the blast holes 2 which are detonated at one time are connected with a detonating network after being filled with explosives.

And (3) calculating the specific charge:

according to the swedish empirical method, the unit consumption is calculated:

q=q₁+q₂+q₃+q₄

in the formula q₁The loading is 2 times of the common land bench blasting, and is increased by 10 percent for the underwater vertical hole. The single consumption of the deep hole blasting of the common hard stone is 0.5kg/m 3;

q₂increment of water pressure above the blasting zone, q₂=0.01h₂（h₂Surface water depth);

q₃increment of the covering over the blast zone, q₃=0.02h₃（h₃Thickness of watch cover layer)

q₄Increment of rock expansion, q₄=0.03h (h stands for step depth)

Here, h₂Taking 21m, h₃Taking 21m, and taking 5m as h.

q=q₁+q₂+q₃+q₄=1.1+0.01*21+0.02*21+0.03*6=1.91kg/m3

Due to the smaller lump size required for crushing, according to similar engineering experience, the specific charge needs to be increased by 50% more, i.e. the engineering charge has a specific charge of q =1.91 (1 + 50%) =2.87kg/m3

After the blasting operation process can refer to the data for trial blasting, the blasting parameters are adjusted according to specific conditions. According to the practical construction experience, when the thickness of the rock stratum is increased and the hole pattern parameters are not changed, the unit consumption needs to be increased properly.

2. Blasting parameter table:

boulder thickness H (m)

Ultra-deep h (m)

Hole distance a (m)

Row pitch b (m)

Each kilogram of the cable is 3

Charge Q (kilogram)

Form of charge

≤5m

1

2.87

0～14.35

Continuous

>5m

1

0.8

2.87

0～14.35

Layering

Setting the length L of the PVC pipe:

L=L_1i+L_2i

l- -length of PVC pipe, L_1i- -explosive segment length, L_2i-weight segment length.

4. Counterweight setting of the counterweight section:

L₁×ρ_explosive+L₂×ρ_{Crushing stone}≧ρ_{Slurry composition}×(L₁+L₂)

Let L₁/L₂= a, a is the distance between adjacent blastholes;

the length of the balance weight and the length of the required PVC pipe can be obtained according to a, and a is less than or equal to 1.75 after calculation. Therefore, when a satisfies the above ratio, the anti-floating requirement is achieved.

5. Explosive quantity:

in order to ensure that the blasting construction does not affect peripheral foundation pits and cofferdam dams, the maximum section dosage must be strictly limited. Therefore, the maximum section of explosive quantity allowed by different buildings (structures) at different distances is calculated according to a blasting ground vibration speed calculation formula of GB 6722-2014. That is, only by carrying out blasting construction according to the maximum loading of each blasting of rocks at different distances, the blasting vibration speed can be smaller than the blasting vibration speed value allowed by the blasting safety regulations, and further the safety of each building and seawall can be ensured.

The blasting vibration velocity calculation formula is as follows: k (Q)^1/3/R）^α

In the formula: r-blasting earthquake safety distance, m; q-explosive quantity, Kg, taking the maximum explosive quantity by millisecond delay blasting; v-earthquake safe speed, cm/s; K. the coefficient and attenuation coefficient related to the conditions of the landform, geology and the like of the blasting site are alpha, and K is 150 and alpha is =1.5 according to the properties of regional granite and past experience.

The maximum allowable explosive amount is: qmax = R³(v/k)³/α。

6. Blasting safety distance:

according to blasting specification, the safe radius of blasting flyrock can be determined by the following formula:

R=20Kn²W

in the formula, K is a safety factor, and K =1.5 is selected; n is the blasting action index of the largest cartridge, n is not less than 0.75, and 0.75 is taken; w is the minimum line of resistance of the maximum one pack, where W = 2.0;

therefore, R =20 × 1.5 × 0.75²2.0=33.75 meters;

the blasting adopted by the invention belongs to underground blasting, no flying stones are harmful to people, and therefore, the warning distance of 50m is enough safe.

7. And (3) checking after blasting:

(1) if the time is more than 5min after the explosion, the inspector is allowed to enter the explosion operation place; if the blind cannon can not be confirmed, the explosion area can be checked after 15 min.

(2) After the explosion point is checked and confirmed to be safe, the worker is allowed to enter the explosion area by the party after the team explosion team leader agrees.

(3) Post-detonation examination of contents

The general contents to be checked for rock blasting are as follows:

① confirming whether there is blind shot;

② whether the diaphragm wall has cracks or damages after blasting;

③ whether there is seismic subsidence around the foundation pit.

(4) Treatment of

① the inspection personnel should report or process the blind cannon and other dangerous cases in time, and before processing, the danger sign should be set on site and corresponding safety measures should be taken, and no independent personnel should approach.

② after blind blasting, carefully inspecting the blasting pile again to collect and uniformly destroy the residual blasting material, and before the blasting pile can not be confirmed to have no residual blasting material, taking preventive measures and sending a specially-assigned person to supervise the blasting pile digging operation.

8. Blasting effect detection

And after the first section of blasting, carrying out coring detection on the blasting area to detect the blasting effect, and taking the extracted complete rock core with the unidirectional length of less than or equal to 30cm as the qualification. And if the sampling core is unqualified, performing secondary blasting on the repaired hole and optimizing blasting parameters. The number of the verification holes is 5 percent of the total holes, and the coring depth reaches 1 meter below the base. And (5) after the core is taken out, analyzing and judging the core sample crack.

9. Blasting safety management

Before construction, relevant personnel are trained in technology and safety, and relevant regulations of blasting safety regulations and blasting design schemes are carefully studied.

(1) Before construction, blasting safety notice should be posted.

(2) Drilling, acceptance inspection and charging are strictly arranged according to the arrangement diagram of the blast holes 2.

(3) After the connection is finished, safety inspection is carried out, and detonation can be carried out after the connection is confirmed to be correct.

(4) The key of the detonator is required to be carried by a blaster, the key cannot be handed over to other people, the key cannot be inserted into the detonator when blasting is powered on, the key must be immediately switched and pulled out after the detonation, and a bus is removed and twisted into a short circuit. The blasting bus is connected with a leg wire, a circuit is checked, and the blasting bus is electrified to work and only operated by one person of a blaster.

(5) When the charging blast hole 2 does not sound after being electrified, a blaster must firstly take off the key and remove the detonating bus from the detonator, and then the detonating bus is twisted into a short circuit, and after at least 15 minutes, the blasting gun can check along the line to find out the cause of the non-sound. After the detonation, people can arrive at the blasting place after the blasting smoke is scattered after 30 minutes.

10. Processing blind cannon

The blind cannon should be processed in time, and the processing mode of the blind cannon is as follows:

(1) if a blind shot is found or suspected, the blasting responsible person should be reported immediately and necessary safety measures taken.

(2) When the blind gun is processed, the processing is carried out under the guidance of a blasting technician or a blasting responsible person. Irrelevant personnel are not present, a warning is set at the boundary of the dangerous area, and other operations are forbidden in the dangerous area.

(3) The following method can be adopted for processing the explosion blind cannon:

① if the factor causing the blind gun is eliminated, if the blasting circuit is possible to connect, the blind gun is eliminated by connecting the blasting circuit again, or the blind gun can be reinitiated under the condition that the blasting circuit, the powder charge, the blockage and the like still have the initiation.

② if the length of the plug is less than the gap distance of explosive or the hole can be filled with explosive, the explosive is filled with an initiating explosive;

③ redrill the parallel hole charge in an area not less than 10 times the diameter of the drilled hole around the hole 2 from which the blind gun occurred.

(4) The blind cannon processing method is strictly operated according to the following cautions:

① prohibit the direct pulling of uninitiated explosive (detonator 5, cartridge, etc.).

② when blind blasting occurs in the electric blasting circuit, the power supply should be cut off immediately and the blasting circuit should be short-circuited in time.

③ after the blind blasting, the blasting operation surface should be inspected carefully to collect the residual explosive.

④ before the existence of residual explosive on the blasting operation surface is not known, a precautionary measure should be taken.

⑤ Each time a blind shot is processed, the processor must fill out a registration card that describes the cause of the shot, the method and results of the shot, and the precautions to be taken.

11. Initiating explosive device management

(1) When the blasting equipment is withdrawn, a worker must carry out blasting, a safety supervisor and a signature of the blasting operator every time, otherwise, the blasting equipment is not withdrawn.

(2) The number of people receiving the explosives and the detonators 5 is at least 2, the number, the serial number and the like must be checked on the spot after the user receives the explosives, and the explosives and the detonators 5 are forbidden to be carried by the same person at the same time.

(3) The warehouse keeper should register and check the code information of the blasting material to avoid error when the blasting material is received by the blasting person each time.

(4) The blasting equipment is subjected to a 'early delivery and late receipt' system, namely, the blasting equipment is delivered in the morning and recovered in the afternoon.

(5) And (4) sending a specially-assigned person to check and count the remaining blasting articles in the construction, returning the blasting articles to the warehouse after the blasting articles are checked to be correct, checking and collecting by warehouse managers according to a clearing order, returning the blasting articles to the warehouse in time, and taking the blasting articles out of the construction site by any person who strictly forbids to store the blasting articles privately. If the violation results in the loss of the blasting equipment, the blasting equipment is seriously investigated until the legal responsibility is followed.

(6) Drilling, charging and detonating according to design requirements, and ensuring the charging construction quality.

(7) And (4) filling (plugging) construction is carried out according to the filling (plugging) material, the filling (plugging) position and the filling (plugging) length required by the design.

Finally, the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting, and other modifications or equivalent substitutions made by the technical solutions of the present invention by those of ordinary skill in the art should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A boulder blasting construction method is characterized by comprising the following steps:

2. The boulder blasting construction method of claim 1, wherein a maximum particle size of stones of the boulder after blasting is less than or equal to 0.3 m.

3. The boulder blasting construction method according to claim 1, wherein a distance between adjacent blast holes in the porous monomer blasting in the step (1) is 0.8-1.2m, and a diameter of the blast hole is 89 mm.

4. The solitary stone blasting construction method according to claim 1, wherein in the step (1), the weight section is filled with crushed stones, the density of the crushed stones is 1.5g/cm3, and the density of the explosive in the explosive package is 0.95-1.25g/cm 3.

5. The method of claim 1, wherein a multi-stage explosive charge is used when the thickness of the boulder is 2m or more, and a single-stage explosive charge is used when the thickness of the boulder is 2m or less.

6. The method of solitary stone blasting according to claim 1, wherein the protective layer comprises a protective plate and sand coats disposed above and below the protective plate, respectively; the protection plate comprises an iron plate and a wood balk arranged below the iron plate; the thickness of the sand cladding below the guard plate was 0.5 m.

7. The boulder blasting construction method according to claim 1, wherein the grout adopted in the grouting in the step (10) is cement grout, the water cement ratio is 1:1, and the grouting pressure is controlled at 1.5 ~ 3 Mpa.

8. The method of claim 1, wherein 4 detonators are installed in each said blast hole.

9. The method of claim 1, wherein a powder charge is installed in a blast hole located on the boulder, and no powder charge is installed in a blast hole outside the range of the boulder.