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an important part of the safety management of open-pit mines, and has a direct relationship with whether open-pit mining is safe. Here, I would like to give you a popular science about the types, prevention and treatment of slope and landslide accidents in open-pit mines, and hope that such tragedies will not be repeated.
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The mining of open-pit mine is to
divide the ore rock into a certain thickness of horizontal layers, mine layer by layer from top to bottom, and form step-like steps around the open-pit mine, and the slope composed of multiple steps is the open-pit mine side gang, that is, the open-pit mine slope.
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step slope, and a bottom line on the slope.
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Steps, according to their use, can be divided into work platform, safety platform, cleaning platform, transportation platform, etc. A final slope is a slope consisting of steps mined to the final interface. The final slope angle is the angle between the final slope slope and the horizontal plane.
With the gradual increase of mine mining depth, the height, area and maintenance time of the open-pit mine slope must be greatly increased, otherwise the slope slide disaster will become increasingly prominent. Therefore, the stability of the slope has increasingly become one of the focuses of mine disaster prevention in China.
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are generally five types of slope landslides: plane landslides, wedge landslides, circular arc landslides, dumping landslides and composite landslides, of which plane landslides are the most frequent landslide types.
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Slope landslide activity is a phenomenon in which the rock mass eventually evolves from deformation to caving under the action of a variety of stresses, and the whole process can be divided into three stages:
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Slope landslides are affected by a variety of factors, mainly divided into the following 6 aspects:
(1) The determination of the slope angle is unreasonable
The slope angle design is too slow, the slope stability is high, but it increases the peeling effort and cost, but can reduce the slope maintenance fee. Increased slope angle, poor stability, reduced stripping effort and stripping cost, but brought unsafe personnel and equipment.
(2) The influence of geological factors on slopes
The rock mass is composed of a variety of rocks, and there are various structural surfaces in the rock mass, and thestructural surfaces are distributed and numbered in the rock mass, which affects the stability of the slope rock mass. A large number of landslide examples show that the sliding surface and edge contour of the landslide mass are controlled by the structural surface of the rock mass.
(3) Groundwater in rock mass
Groundwater can change the physical and mechanical properties of rocks, generate static pressure and buoyancy in the fractures of the rock mass, and when groundwater flows in the fractures in the fractured rock mass, these slope crushed rocks will be subjected to the dynamic pressure of water, so that the stability of the slope is reduced.
(4) Blasting effect
Earthquakes caused by blasting can open the joints of the rock mass, or even break the rock, affecting the stability of the slope.
(5) The geometry of the slope
In open-pit mining, when the slope angle remains unchanged, the higher the slope, the more unstable it is. When the slope height remains unchanged, the larger the slope angle, the more unstable it is. From the horizontal section, the more slopes, the more unstable, because the slopes of the protruding stope are easily damaged by pulling, which is not conducive to the stability of the slope.
(6) Other factors affecting the slope
There are management factors, such as over-excavating slope feet, piling up waste rock and equipment in the upper part of the slope, building houses, etc., the influence of weathering, the influence of seismic activity, all of which will reduce the stability of the slope.
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(1) Reasonably determine the slope angle of the working stage
In open-pit mining, stripping first and mining later, it is strictly forbidden to dig out the bottom and put the upper part to cause landslides. During the work phase, rock drilling, blasting, shipping and geological surveys are carried out and are constantly moving as the recovery progresses.
The ore rock near the slope is affected by the blasting vibration, and accidents often occur because the rock collapses or narrows the width of the platform due to excessive slope angle at the stage. To this end, in the design and production of open-pit mines, it is necessary to determine the appropriate slope angle and specify the minimum working platform width according to the geological conditions of the mine, the mechanical properties of the rock and the performance, specifications and dimensions of various equipment, and set the stripping, mining and transportation equipment, power supply and communication lines within the scope of the stable slope of the working platform.
(2) Slope maintenance
The open-pit mine slope must be regularly inspected and maintained to ensure the stability of the slope and prevent disasters.
Establish a professional team for slope maintenance, strengthen inspection and maintenance, and if necessary, carry out manual slopeing, lay turf, plant shrubs, and build local retaining walls or pre-embedded anti-slip slope stakes.
It is necessary to set up a drainage network to prevent surface rainwater from flowing into the pit to wash the slope and lubricate the layer; Deep concave open-pit mines should be surrounded by facilities to prevent flash floods and debris flows, or to prevent diversion. The drainage network includes surface drainage, underground drainage, and three-dimensional drainage system.
When blastingnear the slope, it is advisable to use pre-cracking and shock absorption blasting methods to reduce the single-hole charge and increase the number of holes, and reduce the number of gun holes for each delayed blasting to prevent the stability of the slope from being damaged due to open blasting operations.
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(3) Anti-slip engineering and reinforcement method
Anti-skid engineering is an indispensable part of landslide prevention, especially for mining slopes where the safety of life and property is at stake.
Anti-slip works include: anti-slip retaining wall, reinforced retaining wall, anchor plate retaining wall, prestressed anchor cable retaining wall, bolt retaining wall.
Anti-slip piles: large cross-sectional row anti-slip monopile, anti-slip chain, steel pipe pile, bearing platform anti-slip pile, flood-resistant pile, pile foundation retaining wall, chair retaining wall, row frame anti-slip pile, anti-slip rigid pile, sheet pile anti-slip pile and anchor pile.
Soil quality improvement: grouting and micropiles.
(4) Monitoring of landslides
Monitoring the displacement of rocks can detect signs of landslides. The activity of groundwater under the slope should also be observed with a water pressure gauge; The effects of blasting vibration are observed with a seismometer to obtain slope dynamics.
(5) Landslide prevention
Restrictions on unlicensed mining and strict prohibition of illegal mining; punish and control mining sites that occupy hilltops and hillsides; Predatory mining without opening work steps, stripping or mining while stripping is prohibited; Destruction of hillside vegetation is strictly prohibited; Flood control facilities to divert water flow must be set up at the edge of the open-pit mine, and the slope must be mechanically reinforced, and anchor poles and anchor piles must be installed.
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In the process of open-pit mining, the stability of the slope directly restricts the safety of the mine and is one of the most critical factors affecting the economic benefits of the mine. Generally, from the mine to the end of mining, the impact of landslides runs throughout, so the treatment of open-pit slopes should continue until the end of mining.
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