(1) Mining work

The mining work includes: rock drilling, charging, and breaking

1) Rock drilling work:

1 Mud hole arrangement - the sub-column sublevel caving method is to make an upward fan-shaped blasthole in the section mining roadway. There are three arrangements for the fan-shaped blasthole dip angle.

(a) Forward tilting arrangement - the inclination of the face is <90°, which is about 70°~85°.

This form is convenient for charging. If the ore is unstable, it will also help prevent the upper part of the ore discharge from falling with a gun. The ore recovery rate is low.

(b) Vertical arrangement - the inclination of the face is 90°. This arrangement, ore recovery, is better than the forward setting. And the direction of the blasthole is easy to grasp, but the charging conditions are worse. If the pressure is charged, the problem is not big. Most of the forms are used when the ore is stable.

(c) Backward placement – ​​in this form, the ore recovery rate is high. However, the conditions of charging and rock drilling are difficult, and it is easy to take off the cannon at the discharge port during blasting. When the ore is stable, it can be used. However, due to the above shortcomings, this arrangement has not been seen in production at home and abroad.

The relationship between the blasthole fan angle and the ore recovery rate is shown in the graph on the left.

2 edge angle of the fan hole

There are three types of edge hole angles, that is, edge hole angles of 5° to 15°, 45° to 50°, and >70°.

(a) The corner angle is 5° to 15° – this arrangement minimizes the borehole depth. When the ore is placed under the overburden, when the inclination angle is below 70°, the ore cannot be released, and the looseness is not obtained. Therefore, with the blasting, the arrangement is likely to cause over-extrusion and side hole blasting. . The recovery of segmented ore under influence. At the same time, the blasthole orifice below 45° is easily blocked by the mine. The workload of cleaning the mine before blasting is large and unsafe. Therefore, only a few mines in production have a poor production capacity due to rock drilling equipment and are unwilling to reduce the height of the section. This arrangement is adopted.

(b) The corner angle of the hole is 45° to 50°. This arrangement has a medium depth of the blasthole and a hole of about 45°. Although it is sometimes buried, the cleaning work is not large. When the segment height is 10 meters, the maximum blasthole depth is about 15 meters, which is compatible with the current capabilities of all rock drilling equipment used in China. Therefore, most of the mines at home and abroad use this arrangement.

(c) The edge angle is >70° - this arrangement, the edge angle is roughly consistent with the limit discharge rock hopper, and the blasted ore flows on the unblasted ore surface, which can get better recovery and collapse. The ore will not bury the blasthole, and the charge is convenient, but the depth of the blasthole is the largest.

When the rock drilling technology can smoothly cut a deep hole of more than 17 meters in a large width roadway, this arrangement is better.

However, according to the YG-80 rock drill used in mines in China, the hole depth is more than 15 meters, and the efficiency is significantly reduced. Some mines abroad use wide recovery tunnels (5 to 6 meters wide), at this time, vertical parallel holes and inclined holes of 70° or more are used. Received a good result. When the ore stability is allowed, increasing the width of the mining approach should be considered reasonable.

2 rock drilling equipment

The domestic main adopts CZZ-700 rubber wheel self-single-single rock drilling rig, equipped with YG-80 rock drill , BBC-120F and YZ-90 rock drill. This type of trolley can be used for fan-shaped holes or parallel holes. It is flexible to move, easy to operate, and has high rock drilling efficiency. The average production capacity is 30-50 meters/set.

The medium-sized mine uses a rock drilling rig with a YG-80 rock drill. The gantry has a simple structure, is easy to manufacture, and has a small amount of maintenance, but the rock drilling efficiency is lower than that of the trolley.

3 Blasting parameters. (dwa _bottom )

Commonly used solder alloy head diameter: 51 ~ 65mm.

The minimum resistance line w=1.5～2.0 meters. Generally, it can be calculated by W=30d. (d - aperture). If it is too small, when the front row of holes is blasted, it is easy to damage the rear row of holes, and it is easy to carry a gun. When W is too large, it is easy to produce large blocks and blasting vertical grooves, which affects the blasting effect.

A hole bottom from _{the bottom} - when the scallops are arranged so that a _bottom generally ≈W. However, at this time, the orifice of the orifice is too dense. In order to make the ore crush evenly, it is considered to appropriately reduce the W value, and at the same time increase the _bottom value of a, and keep the _{bottom of the a} × W product unchanged. This can achieve better results.

2) Blasting work

1) Collapsing step distance - In the mining roadway, the thickness of the blasting layer is called the collapse step. Generally, 1 to 2 rows of holes are blasted each time. The collapsing step used in production is 1.8 to 3.0 meters. The optimal collapse step is determined by production practices and tests. If it is too big or too small, it will make the ore loss worse.

1 When the step of the collapse is too large, the ellipsoid will quickly extend into the upper waste rock, that is, the upper waste rock will soon flow into the mining roadway, blocking a large amount of ore in front, so that this part of the ore cannot be released. The result is a loss of ore. (Figure (b))

2 When the step of the collapse is too small, the ellipsoid is released and quickly reaches the front of the waste rock. The waste rock on the front of the mining roadway appears ahead of time, increasing the depletion index of the ore.

3 [Reference] If the vibrating ore concentrator is used, the depth of the ore active zone can be increased, and the eccentricity of the ellipsoid can be reduced, thereby increasing the step size of the collapse.

b) Charge work

It can be used with a manual charge or a pressurized charge. With gas charge pressure can be increased charge density of 0.9 to 1.0 g / cm ³ or more, only artificially charge of 0.6 g / cm ³ or so.

When a compressed gas charge is used, a charge such as FZY-10 type, ZYZ-150 type, FZY-1 type, or WZ-200 type may be used. (use the first two). Explosives loaded into the applicator must be screened beforehand to prevent blockage.

c) Detonation method - For the sublevel caving method without bottom column, due to the large number of blasting, the method of detonating the detonating line and the detonator is generally adopted. Using this method, the detonating wires in each blasthole are connected in parallel. The detonating line of the first row of blastholes is detonated by a common fire detonator, and the second row is detonated by a squib. That is, the fire tube is used to detonate, and the outer tube and the detonating line are detonated. Detonation in this way, safety is good.

(2) Ventilation work

The poor ventilation conditions of the sublevel caving without pillars are mainly due to the fact that the section mining roadways are all single lanes, with a large number, large sections, and inter-connected, and each mining roadway communicates with the surface through the caving area. Therefore, this mining method is difficult to form a through-flow, which is difficult to manage.

Ventilation problems are not well resolved at home and abroad. This problem will become more pronounced as the depth of mining increases and the use of diesel equipment. At present, foreign mines have adopted an increase in air supply to improve ventilation conditions.

Domestic mines mainly use the fan ventilation of the working face. It is difficult to install according to the method, and the management is also very difficult, so the effect is not good.

Many people are now studying how to create a method of ventilation through the wind, such as the use of high-segment double-deck mining, so that the local fan can be set in the upper rock section to increase the pressure difference and carry out the mine ventilation to improve Ventilation conditions for the loading tunnel.

In addition, some people are still studying the use of "ground communication wind", "drilling ventilation" have some problems, immature. To be studied.

(3) Mining work

1) Mining is the use of mining equipment to transport the ore at the end of the mining approach to the chute. The mining equipment currently used is mainly: ZYQ-14 type loading motive (the car box volume is about 1.8m ³ , the shift efficiency is 120~150T/set. Class, the annual efficiency is about 80,000 tons.) Scraper (diesel drive, The short-distance production capacity is 300-400T/set. Class.)

The factors affecting the efficiency of the mining are: the ore block, the transport distance, the radius of the curve, and the level of the road.

Although the use of the scraper is fast, high in productivity and high in efficiency, it is necessary to solve the problem of exhaust gas purification.

2) Mining management issues

The purpose of mining management is to obtain better indicators of depletion of ore loss, so it is very important to strictly control the cut-off grade of ore. At present, the domestic acquisition of the ore grade mainly relies on sampling for chemical analysis. This method is slow, and the ore-release period is short, and the grade of the ore is greatly changed. In this way, the sampling test can not meet the requirements of on-site production. Therefore, in actual production, it is usually necessary to rely on the experience of the miners and engineers to identify the degree of depletion of the ore with the naked eye or feeling according to the changes in the color, specific gravity and blockiness of the released ore. So this is not accurate.

At present, some metal mines in foreign countries use the physicochemical properties of ore to make some instruments, such as portable isotope fluorescence analyzer, which can quickly analyze ore in the work. In this way, it is possible to control the cut-off grade of the mine well, and it is possible to obtain a better indicator of loss and depletion.

(4) The order of recovery is as follows:

The order of recovery between the upper and lower segments in the 1st stage - in the order of top-down. The recovery of the upper segment should be a certain distance from the front and lower segments (generally a distance greater than one segment height).

2 The order of recovery of each nugget in the same segment.

3 When the local pressure is large, or the ore is stable enough, the order of recovery from the two wings to the center should be avoided as much as possible to prevent the situation as shown in the following figure.

4 The mining roadway of each ore block in the same section should be kept in a straight line to reduce the contact surface between the ore and the waste rock, which is beneficial to reduce the loss and depletion of the ore, and is beneficial to the maintenance and addition of the mining roadway. The stability. Generally, 3 to 5 routes are as straight as possible. If it can't be in a straight line, if it is ahead, it should be no larger than a segmented height.