This paper introduces the types, prevention and treatment of slope and landslide accidents in open-pit mines. The mining
of open-pit mine is to divide the ore and rock into horizontal layers with a certain thickness and mine them layer by layer from top to bottom, forming step-like steps around the open-pit mine. The slope composed of multiple steps is the open-pit slope, that is, the open-pit slope.
The open-pit mine slope is composed of bench, upper bench flat plate, lower bench flat plate, bench slope, bench slope angle, bench height, bench slope top line, bench slope bottom line, etc.
Steps can be divided into working platform, safety platform, cleaning platform and transportation platform according to their uses. The final slope refers to the slope composed of the bench mined to the final interface. The final slope angle is the angle between the final slope face and the horizontal plane.
With the gradual increase of mining depth, the height, area and maintenance time of open-pit mine slope should be greatly increased accordingly, otherwise, the slope sliding disaster will become increasingly prominent. Therefore, the stability of slope is becoming one of the key points of mine disaster prevention in China. The types
of
landslide generally include plane landslide, wedge landslide, circular landslide, toppling landslide and compound landslide, among which plane landslide is the most common type of landslide. Causes
of
landslide The landslide activity is a phenomenon that the rock mass deforms and eventually develops into collapse under the action of various stresses. The whole process can be divided into three stages:
The landslide is affected by many factors, mainly divided into the following six aspects. If the slope angle is
determined to be unreasonable and
the slope angle is designed to be too gentle, the slope stability will be higher, but the stripping workload and cost will be increased, and the slope maintenance cost will be reduced. If the slope angle is increased, the stability will be poor, and the stripping workload and cost will be reduced, but the personnel and equipment will be unsafe.
The
rock mass is composed of a variety of rocks, there are a variety of structural planes in the rock mass, the distribution and number of structural planes in the rock mass affect the stability of the slope rock mass. A large number of landslide examples show that the sliding surface and edge contour of the landslide body are controlled by the structural plane of the rock mass. Groundwater
in the
rock mass can change the physical and mechanical properties of the rock, and produce static pressure and buoyancy in the fissures of the rock mass. When the groundwater flows in the fissures of the broken rock mass, the slope broken rock will be subjected to the dynamic pressure of the water, thus reducing the stability of the slope. The earthquake caused by
blasting can open the joints of the rock mass, even break the rock, and affect the stability of the slope. Geometrical shape
of the slope In open-pit mining, when the slope angle is constant, the higher the slope is, the more unstable it is. When the slope height is constant, the larger the slope angle is, the more unstable it is. From the horizontal section, the more the slope is, the more unstable it is, because the slope protruding to the stope is easily damaged by tension, which is not conducive to the stability of the slope. Other factors
affecting the slope include management factors, such as over-excavation of the slope toe, waste rocks and equipment piled on the upper part of the slope, buildings, etc., the impact of weathering, and the impact of seismic activity, all of which will reduce the stability of the slope. Prevention and control
of
landslide When open-pit mining is carried out at the slope angle
of the working stage, stripping shall be carried out first and then mining shall be carried out. It is strictly forbidden to dig the bottom and put the upper part to cause brutal and risky mining of landslide. In the working stage, rock drilling, blasting, loading and geological survey are needed, and they are constantly moving with the advance of mining. The rock near the
slope is affected by blasting vibration, and accidents often occur because the slope angle is too large to cause rock collapse or narrow the width of the platform. Therefore, in the design and production of open-pit mines, it is necessary to determine the appropriate slope angle and specify the minimum width of the working platform according to the geological conditions of the mine, the mechanical properties of the rock and the performance, specifications and sizes of various equipment used, and to set the stripping, mining and transportation equipment, power supply and communication lines within the scope of the stable slope of the working platform.
Slope maintenance
The open-pit mine slope must be inspected and maintained regularly to ensure the stability of the slope and prevent disasters. A professional slope maintenance team shall be
established to strengthen inspection and maintenance. If necessary, artificial sloping shall be carried out, turf shall be laid, shrubs shall be planted, local retaining walls shall be built or anti-landslide piles shall be embedded. Drainage network
shall be set up to prevent surface rainwater from flowing into the pit to scour the slope and lubricate the bedding; deep open pit mines shall set up blocking or dredging facilities to prevent mountain torrents and debris flows outside the pit. Drainage network includes the following three parts: surface drainage, underground drainage and three-dimensional drainage system. When blasting is carried out
near the slope, the presplitting and damping blasting methods should be used to reduce the charge of a single hole and increase the number of holes, and reduce the number of holes for each delay blasting, so as to prevent the stability of the slope from being damaged by the open-air blasting operation.
Anti-slide engineering and reinforcement methods
Anti-slide engineering is an indispensable part to prevent landslides, especially for the mining slope which is related to the safety of life and property.
Anti-slide engineering includes: anti-slide retaining wall, reinforced retaining wall, anchor plate retaining wall, prestressed anchor cable retaining wall and anchor rod retaining wall.
Anti-slide pile: large-section row anti-slide single pile, anti-slide chain, steel pipe pile, bearing table anti-slide pile, anti-flood pile, pile foundation retaining wall, chair retaining wall, bent anti-slide pile, anti-slide rigid frame pile, sheet pile anti-slide pile and anchor pile.
Soil improvement: grouting and micro-pile. The monitoring
of
landslide can find the sign of landslide by monitoring the displacement of rock. The movement of underground water under the slope should also be observed with a water pressure gauge, and the influence of blasting vibration should be observed with a seismograph to obtain the slope dynamics. The
prevention and control
of landslide shall restrict the mining without license and prohibit the illegal mining; punish and control the mining spots occupying the hilltop and hillside by force; prohibit the predatory mining without opening the working bench, without stripping or while stripping; It is strictly prohibited to destroy the hillside vegetation. Flood control facilities for dredging water flow must be set up at the edge of open-pit mines. Mechanical reinforcement shall be carried out for the side slope, and anchor rod and anchor pile shall be set. In the process
of open-pit mining, whether the slope is stable or not directly restricts the safety of the mine, which is one of the most critical factors affecting the economic benefits of the mine. Generally, the impact of landslide runs through the whole process from the mine production to the end of mining, so the treatment of open-pit slope should continue until the end of mining, and its investment is huge.
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