Prevention and control of mine landslide

Type of landslide

First, the plane landslide

Bedding landslides are the most common type of landslide. Generally it is sliding along the level. It can be divided into two types: landslides along a single level and flat sliding landslides. Along a single level of landslide, the general slip angle is larger than the inner friction angle, and the scale is large, and the chamfer layer excavation is often an important artificial cause of landslide formation. The sloping type sliding landslide has a composite shape, the main sliding surface is a rock surface sliding surface, and the trailing edge of the landslide is an approximate circular arc shape, which is formed along the tracing and development of the structural joints, and the inclination angle gradually changes. Steep and high angle. The main sliding surface is relatively flat, and the sliding deformation speed of the sliding body is small.

Second, the wedge landslide

Wedge landslides are the most common form of landslide. The main feature of the wedge landslide is that the sliding surface and the cutting surface are both large faults or weak structural planes; according to the number of structural planes, it can be divided into two kinds of structural planes, and three structures. The sliding wedge formed by the combination of faces. The landslide formed by the combination of two structural planes is generally a double-slip landslide that slides along the line of intersection of the combined line; the landslide formed by the combination of the three structural planes may be a double-slip landslide that slides in the direction of the intersection of the combined lines. It may also be a single slip surface landslide with a single structural plane tending to slide. When there are two structural planes in the slope intersecting each other to form a wedge-shaped unstable body, that is, when the combined intersection tendency of the two structural planes is similar to or the same as the slope tendency, and the inclination angle is smaller than the slope angle and larger than the internal friction angle, it is easy. A wedge landslide occurs. In addition, its size is generally small.

Third, the arc landslide

Arc sliding landslide means that the sliding surface is arc-shaped and is common in soil landslides. Such landslides generally undergo three stages of creeping deformation through the slope angle, the expansion of the trailing edge of the landslide and the breakage of the landslide in the middle of the landslide. Its early development was slow, and it developed rapidly in the middle and late stages, and the landslide speed was very high. The broken rock mass of the loose structure or the landslide of the soft subsidence rock slope belongs to this.

Fourth, dumping landslides

The dumping deformation landslide generally has an anti-dip slope structure, which initially produces a displacement along the anti-dip structure surface in the slope rock mass, and the slope surface forms a fine dislocation crack, which in turn develops into a crack, further along with the rock stratum level. The displacement causes a relatively differential deformation on both sides of the crack on the slope surface, and the rock layer gradually slopes outward until it collapses. When the slope of the slope rock mass structure is steep, the rock mass may fall. Its failure mechanism is different from the above three. It is the collapse damage caused by the rock mass moving under the action of rock gravity. This type of landslide often occurs on the slope of the step and rarely causes the entire slope to slide.

5. Composite landslide

That is, the landslide formed by the combination of the above two forms. Composite slip surface landslides are common in rock-soil slopes with thick Quaternary overburdens. The soil of the Quaternary cover layer forms an approximately arc-shaped slip surface, while the lower geological structure surface, especially the weak structural plane, develops.

Cause of landslide

According to the theory of mechanics, an object is stationary and is the result of the force balance in all directions. If one or more of the forces change, the balance of the object is destroyed, and the corresponding movement occurs, that is, moving from the original position to the new position in a different way, and forming a new balance of power, which is Equilibrium theory or balance theory.

The factors affecting the stability of slope are: the mechanical properties of the slope rock, the complexity of the geological structure, the joints, the slip surface and the faults; the movement of the groundwater level and the ground rainfall; the existence of residual tectonic pressure; the blasting in the stope Movement; geometric changes in the stope; rainy season and thawing period.

The landslide activity is a phenomenon in which the rock and soil body undergoes deformation and collapse under various dynamic forces. Its formation can be divided into three stages: the first stage is the accumulation stage of unstable factors; the second stage is the gravity collapse stage; the third stage is the equilibrium recovery stage. The first stage: under the long-term geological stress, the rock and soil body produces joints, cracks or fractures, the integrity is destroyed, and even the fracture is divided into fragmented blocks, which lays a foundation for landslide activities. The duration of this phase varies with the nature and structure of the rock, the degree of tectonic activity, the shape of the slope, the strength of the external stress, and so on. The second stage is that the landslide body is separated from the parent rock: it collapses sharply and violently along the direction of the maximum gravity gradient, and then accumulates on the slope. The third phase is the equilibrium recovery phase, and at the same time it is the preparation phase for the next possible landslide, and this cycle changes.

Landslide activity is affected by many factors, mainly during the rainy season. In the soft and hard phase rock formations, due to the differential weathering, the hard rock mass is prominent, and the hard rock body will collapse and fall due to structural surface cutting or gravity creep. The geological tectonic development makes the intact rock divided into splitting bodies, and the splitting body is unstable under the induced factors to form a collapse field. Therefore, the more the structure is developed, the more broken the rock mass is, and the more likely it is to collapse and fall. The artificial influence is mainly to excavate the slope foot and change the stress field, so that the elastic strain energy accumulated in the slope body is released and the stress is redistributed. The rock body produces unloading cracks, which are multi-open and parallel to the slope surface. The crack expands and expands, and the rock mass cut by it may be unstable to form a collapse landslide.

Currently landslide open-air coal mine, iron ore, quarry occurred, mostly due to violation of the mining sequence Luancailanwa caused. In order to make the open-pit mining and stripping operations work normally, the rock mass of the stope slope should have certain stability. When the working steps are mined to the outermost boundary, the final slope is formed. When the final slope angle is too steep, the stability is poor, easy to landslide, endangering the safety of personnel and equipment, leading to the suspension of production and closure; when it is too slow, it will reduce the economic benefits of mining.

Landslide prevention and treatment

First, a reasonable determination of the slope angle of the working stage

Slope stability is a safety guarantee for open pit mining. In open-pit mining, it is first stripped and then mined. It is strictly forbidden to smash the bottom and put the upper part to cause landslides. At the working stage, operations such as rock drilling, blasting, shipping, and geological surveys are required, and they continue to move as the mining progresses. At the stage, especially the ore near the slope is affected by the blasting vibration, and the accident often occurs because the slope of the slope is too large, causing the rock to 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 working platform width according to the geological conditions of the mine, the mechanical properties of the rock and the performance and size of various equipment, and to strip and mine. And transportation equipment, power supply and communication lines, set in the scope of the stable slope of the working platform.

Second, slope maintenance

Open pit slopes must be regularly inspected and maintained to ensure slope stability and prevent disasters. Establish a professional team for slope maintenance, strengthen inspection and maintenance, carry out artificial grading when necessary, lay turf, plant shrubs, build local retaining walls or pre-slip piles. 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 bedding; deep-pit open pit mines should be equipped with facilities for preventing flooding or mudslides around the pit. The drainage network consists of the following three parts: surface drainage; underground drainage; three-dimensional drainage system. When blasting near the slope, it is advisable to use pre-cracking and shock blasting methods to reduce the single-hole charge and increase the number of holes, and reduce the number of blast holes per blasting to prevent damage due to open-pit blasting operations. The stability of the slope.

Third, anti-sliding engineering and reinforcement methods

Anti-sliding engineering is an indispensable part of preventing landslides, especially for mine slopes that are related to life and property safety. Anti-sliding works include: anti-sliding retaining wall, reinforced retaining wall, anchoring plate retaining wall, prestressed anchor retaining wall, anchor retaining wall. Anti-slide pile: large section area anti-sliding single pile, anti-sliding chain, steel pipe pile, bearing anti-slide pile, flood-resistant pile, pile foundation retaining wall, chair retaining wall, frame type anti-slide pile, anti-slip Rigid frame piles, sheet pile anti-slide piles and anchor piles. Soil improvement: grouting, micro piles.

Fourth, the monitoring of landslides

Monitoring the displacement of the rock reveals signs of landslides. The activity of the groundwater below the slope should also be observed with a water pressure gauge; the impact of the blasting vibration is observed with a seismometer to obtain the slope dynamics.

Fifth, landslide prevention

Restriction of unlicensed mining, illegal mining is strictly prohibited; penalties are imposed on mining sites that occupy hills and hillsides; predatory mining that does not open working steps, does not strip or exfoliate mining; it is forbidden to destroy hillside vegetation. Flood control facilities for diverting water flow must be provided at the edge of the open pit mine. The slope is mechanically reinforced, and anchors and anchor piles are provided.

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