Hydraulic water seal blasting technology

Laiwu steel Group Lunan River Mining Company Mining Field Anshan poor magnetite ore, a density ρ = 3490kg / m ^3, Platts hard coefficient f = 8 ~ 12, is a high-density hard wear Hardness burst ore. In addition, the Shanghe stope is a narrow strip shape with an average width of less than 200m. The amount of medium explosive charge is strictly controlled. In addition, the structure of the rock in the stope is complex, and the explosive properties of different sections and different rock types vary greatly. The high rate of mid-explosion is high, resulting in a substantial increase in the amount of secondary blasting.

First, the second pressure of water pressure water seal

The conventional method of secondary crushing is the drilling method, and the drilling depth is about 1/2 to 2/3 of the thickness of the rock in the direction of the drilling. This method has high labor intensity, serious dust hazard, low production efficiency, high cost, and a large range of blasting flying stones. Due to the small width of the Shanghe stope, there are blasting flying stones and apples, vineyards and vegetable greenhouses around the stope, which often cause farmers to claim and even prevent blasting, which seriously affects normal production.

In order to effectively control the secondary blasting distance and blasting dust, protect the safety of people, equipment and crops, reduce labor intensity, increase labor productivity, and reduce the cost of secondary blasting, I explore the implementation of water according to the mechanism of water blasting and water sealing blasting. Pressurized water seal secondary blasting technology.

Second, the hydraulic pressure seal blasting mechanism

The hydraulic seal blasting section is shown in the following figure:

Hydraulic water seal blasting section

The blasting mechanism is analyzed as follows:

(1) Basic mechanism

According to the blasting mechanism, when the explosive is exploded in the rock, the energy released is applied to the rock in the manner of the shock wave and the detonating gas expansion pressure, causing the rock to be destroyed. According to the theory, for general industrial explosives, the detonation wave head pressure can be approximated by the following formula, ie

P ₂ =ρoD2/4

Where P ₂ - detonation pressure, KPa;

Ρo-the initial density of the explosive, g/cm ³ ;

Detonation speed of D-explosive, m/s.

It can be seen from the formula that the higher the density and detonation speed of the explosive, the greater the severity. Considering the performance of the explosive and the ease of use, the No. 2 rock emulsion explosive was selected as the charge in the hole. This explosive has good water resistance and is suitable for hydraulic blasting. Its density ρo = 1.00 ~ 1.25g / cm ³ , detonation speed D ≥ 3000m / s. From this, the detonation pressure is calculated to be P2 ≥ 2250 MPa.

Since the unsupported shock wave will decay rapidly as the propagation distance increases, the use of a non-coupling charge will result in a reduction in the shock wave head pressure reaching the borehole wall. However, when air is not used and water is used as the non-coupling medium, and the coupling coefficient is small, the shock wave head pressure is not attenuated too much. Therefore, water is used as the non-coupling medium, and the uncoupling coefficient is controlled to be 1.2 to 1.4.

(2) The role of water injection in the hole

It is well known that water has poor compressibility (generally, the density of water changes by only about 5% under 1000 atmospheres), and is usually treated as an incompressible medium. Therefore, when the explosive is exploded in water, the deformation of the water itself is consumed. Very little, the pressure transmission effect is very good. When the drug pack explodes in water, it generally generates shock waves in the water to propagate around, and at the same time, it also generates the pulsation of the high-pressure air mass formed by the explosive gaseous products.

In the case of water blasting, the damage process of the rock to the rock mass can be summarized as follows: after the explosive is detonated, the borehole wall is firstly subjected to the shock wave passing through the water medium with a peak value of several hundred to several thousand atmospheres. Under the action of strong load, the deformation displacement begins. When the deformation stress exceeds the tensile ultimate strength of the rock, the rock mass is broken. Then, the borehole wall is immediately subjected to the pressure generated by the explosion of the high pressure air mass, just like another jump. The loading further exacerbates the damage of the rock mass. Thereafter, the water with residual pressure rushes out from the weakest point (orifice) of the rock mass. Because the residual pressure energy of the water flow is large, a small amount of rock fragments will be carried out to form a flying stone. It can be seen that there are two types of loads in hydraulic blasting: one is the action of shock waves; the other is the expansion pressure of high-pressure air masses and the high-speed water flow formed by them.

(3) The role of the orifice water seal

The plastic bag filled with water seals the top of the orifice and the periphery of the orifice, delaying the explosion of the explosive product and the high-pressure water in the hole, prolonging the time of the explosion product and the high-pressure water in the hole acting on the hole wall, increasing the time The crushing effect on the rock mass. In addition, in order to further reduce the drilling cost, the drilling depth is adjusted to 1/3 of the conventional depth, so that the distance from the package to the orifice is greatly reduced. From the foregoing, it can be known that the residual pressure water with larger energy will carry a small amount. The rock fragments rush outward to form a flying stone, and the orifice water seal can effectively suppress the amount of flying stones and the distance of the flying stones. At the moment of the explosion of the explosive, the ore flying stone transmits the vast majority of the residual pressure water energy obtained to the water in the upper water pocket of the orifice, while the flying stone itself has a small residual energy and a small flying distance. Therefore, the damage of the blasting flying stone is effectively controlled. The water in the water bag will not only get the energy from the orifice flying stone, but also the energy from the water injection in the hole. The water in the water bag after the energy is obtained will immediately splash, forming a "water mist" above the rock block, covering the blasting dust that is subsequently raised, and damping the dust to quickly drop it to the ground. In addition, the water in the water bag can also effectively reduce the intensity of the explosion shock wave entering the air, so that it is attenuated into sound waves in a short distance, and plays a role of silencing.

Third, the amount of charge calculation

The water pressure water seal blasting single hole charge can be calculated as follows.

q=KW3u

Where q-single hole charge, g;

K-single hole dosage coefficient, g/m ³ , generally K=80-100g/m ³ ;

The minimum distance from the center of the W-package to the surface of the rock block (except the surface at the orifice), m;

U-environment correction coefficient, the value of which takes u=0.5~1.0, takes a small value when there are vulnerable items near the explosion area, and vice versa.

Fourth, the construction of blasting operations

The blasting operation is carried out as follows.

(1) Drilling: Drill holes in large blocks according to the volume, shape and placement of the large blocks. The drilling depth is 1/6 to 1/4 of the thickness of the rock in the direction of the drilling.

(2) Charge: first fill the hole with water, then evenly pack the No. 2 rock emulsion explosive on the No. 8 detonator, hand-crank the tube, and gently put the medicine bag to the bottom of the hole.

(3) Orifice water seal: a square plastic bag with a side length of not less than 40cm (a round or octagonal plastic bag has a better effect, but the cost is slightly higher). After the water is sealed, it is placed on the orifice and the detonating tube is taken out. In order to ensure the water seal effect, the gravel around the orifice must be cleaned. The thickness of the water directly above the orifice should not be less than 8cm, and the radius of the water seal around the orifice should not be less than 12cm.

(4) Connection: The group is connected to the detonating tube.

(5) Detonation: Everything is ready and detonated according to the prescribed procedures.

(6) Post-explosion inspection: Immediately after blasting, the site is inspected. If leakage or explosion is found, the cause should be immediately identified and the explosion treatment should be carried out.

The secondary crushing of the open pit is generally carried out near the electric shovel. In order to protect the shovel operation room glass, the shovel is parked back to the blasting point 30m away before blasting, and the cable is removed. In order to facilitate the placement of the water bag, the shovel tries to flatten out the large pieces that are picked out.

Fifth, the effect analysis

Since the end of 2001, it has been a year and a half to explore the implementation of hydraulic water seal blasting technology in the Shanghe stop. The results show that this blasting method has obvious advantages compared with the traditional blasting and blasting method:

(1) Reduced drilling cost by 2/3

The water pressure water seal blasting technology requires the drilling depth to be 1/6 to 1/4 of the thickness of the rock mass, compared with the traditional borehole blasting method (the drilling depth is 1/2 to 2/3 of the rock mass thickness). The drilling cost (including the cost of the pressure) was reduced by 2/3. This alone saved 2.2 million yuan in 2002.

(2) The scope of blasting flying stones is effectively controlled

The second blasting is most likely to produce flying stones at the orifice, while the hydraulic water blasting technology uses a plastic water bag to seal the orifice and its surroundings, so that the distance of the flying stone generated is effectively controlled, thus making the blasting flystone range Zoom out. This is very important for the Shanghe stop. Because the average width of the Shanghe stop is less than 200m, the distance between the blasting and flying stones is slightly larger, and it will fly out of the stope, damaging the surrounding apples, grapes, greenhouse vegetables and other crops, causing economic losses. Before the use of hydraulic water seal blasting technology, the annual blasting of flying stones to damage crops and external compensation of more than 20,000 yuan, this is only a small part. Compensation for flying stones after bad crops is generally difficult to deal with. Often, due to inconsistent compensation opinions, the relationship between workers and peasants is tense, and the occurrence of production suspensions involves a lot of manpower and material resources. According to incomplete statistics, the direct and indirect losses caused by this year are only over 200,000 yuan.

(3) The discharge of secondary blasting dust is greatly reduced

The drilling depth required by the hydraulic seal blasting technology is reduced by 2/3 compared with the conventional blasting method, and the dust emission during the drilling process is also reduced. In addition, the water-pressure water-sealed blasting technology uses a plastic water bag to seal the hole and its surroundings. When blasting, the water in the plastic bag is first thrown away by the explosive energy, forming a “water mist” above the rock block, covering and hitting. The wet blasting dust makes the dust quickly drop to the ground, improving the working environment of the stope and reducing the incidence of pneumoconiosis. At the same time, the amount of blasting dust discharged is greatly reduced, and the surrounding environment of the stope is protected.

(4) Explosive material consumption

The hydraulic water seal blasting crushing method is compared with the traditional borehole crushing method: the consumption of the detonator and the detonating tube is basically the same; the consumption of the explosive is increased by about 80%; and a plastic bag consumption is also added.

(5) Cost comparison

The various costs of the hydraulic water seal blasting crushing method and the traditional drilling and breaking method are shown in the following table:

Secondary crushing cost comparison table

(unit: yuan)

After comparison: the use of hydraulic water seal blasting technology can save 504,000 yuan per year, economically reasonable.

Sixth, the existing problems

The hydraulic pressure seal blasting method has obvious advantages compared with the traditional borehole crushing method, but there are still some problems to be improved.

Secondary blasting dust

Although the hydraulic water seal blasting technology greatly reduces the amount of dust emissions, a small amount of dust is still generated during the perforation process.

In order to eliminate the secondary blasting dust, I have explored the experimental water seal compression concentrating drug pack secondary explosion technology (referred to as water seal blasting). The ammonium nitrate explosive is compressed under a certain pressure to form a drug pack with a collecting energy point. When the secondary blasting is carried out, the drug pack is placed on the surface of the large rock, and the plastic bag is filled with water and then sealed on the medicine bag. The pack was detonated with a No. 8 detonator and the effect was very good. The principle is: the use of the energy-collecting point of the drug pack to generate the energy-concentrating effect, so that the explosion energy is redistributed in space to improve the energy utilization rate; the plastic water bag sealed on the medicine package can further improve the energy utilization rate, and at the same time Silence, dust, and reduce the scattering of gravel.

Although this secondary blasting method is smaller than the explosion shock wave generated by the general bare blasting method, the blasting wave intensity generated by the secondary blasting method is still many times larger than that of the hydraulic water sealing blasting method. There are two villages around the Shanghe stop, and some of the houses are less than 200m away from the stope. Experiments show that when the number of large blasts exceeds 30, the explosion shock wave generated has a significant impact on nearby residents. Therefore, the number of large blasts must be controlled at around 20 blocks. On the upper reaches of the river, an average of 220 blocks must be exploded every day. With this method of crushing, it is necessary to blast 10 times a day, which obviously does not work. Therefore, this crushing method can only be implemented as a secondary secondary crushing method in a small section.

Environmental hazard

The water-pressure water-sealed blasting technology is used to break up the large pieces, and the plastic water bags that are blown into small pieces are scattered in the ore. Due to the long degradation time of plastic chips in the environment, it will inevitably cause certain harm to the environment. However, under the current circumstances, the cost of making water bags from other materials is relatively high and economically unreasonable.

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