Tailings dry landfill design

When the tailings are put into storage, the water content is very high. Although it can seep through a water filtration facility after storage, it will be supplemented by daily rainfall water and surface runoff water. If it is rainy season or continuous rainstorm, it can sometimes be The tailings are in a state of water saturation, which creates a large side pressure on the tailings dam. If the dam is inadvertently, the dam will cause huge losses.

The new technology design can make the tailings gradually dewatering and drying in the sub-storage landfill stage, and is strictly sealed in the landfill reservoir area after the final synthesis type, so the final tailings reservoir is absolutely safe and reliable, and the outside world is Zero pollution in the environment.

This new technology is applicable in both plains and mountains. Particularly useful is the ability to reinforce, cover and expand the existing tailings pond, which not only completely eliminates the safety hazards of the current tailings pond, but also enables large-capacity expansion of the current tailings pond (see Figure W-9). The vertical section implementation of the cross-section diagram), so that the land use efficiency is greatly improved.

For the convenience of calculation, the project of this embodiment is built on the plain, and the footprint of the landfill is rectangular.

2. Implementation content

The new technology implements the tailings dry landfill in two stages: the first stage is the “separate landfill stage” and the second stage is the “peripheral stage”, which is described as follows:

2.1 sub-storage landfill stage

The main content of the silo landfill phase is to construct and fill all the silos in turn, and the implementation period is the landfill design period. A total of 408 silos are built in this design project. Each silo has a diameter of 20 meters, a filling height of 24 meters and a volume of 7540 cubic meters. The total landfill volume of the 408 silos is 3,076,300 cubic meters. If it is 421 cubic meters per day, it can be landfilled for 20 years.

The diameter of the silo should be determined according to the height of the silo. The appropriate ratio of the diameter and height of the silo is about 1:1.2.

First, level the site. If the local soil source is lacking, the surface soil will be excavated and transported to the outside of the site for future coverage in the future.

The tailings drainage mains, branch pipes, and each collection well are then laid. Finally, each silo is constructed in turn and fed in turn.

Since the liquid tailings slurry will generate a large side pressure on the silo body, the continuous feeding of one silo should not be too much. According to the daily feeding of 421 cubic meters, the first silo feed is 1.5 days for 631 cubic meters. Meter, the tailings working face in the silo rises about 2 meters, and then turns to the second silo feed.

After the completion of the feeding to the last 408th silo in turn, it has experienced 408X1.5=612 days, when the tailings water in the first silo has been discharged a lot due to infiltration and evaporation, and the tailings body tends to dry and Consolidation, the working surface of the packing also decreased.

After the tailings feed reaches a suitable height, the reinforced ring is placed, and the reinforced ring is rounded according to the design requirements. When filling, the inside of the reinforced ring should be filled before filling the outside of the reinforced ring.

The placement of the reinforced ring in the solid material can greatly reduce the lateral force generated by the solid material accumulation on the silo body. In addition, a total of 13 vertical soft permeable pipes placed in the center of the silo and along the inner wall of the silo can be The moisture in the tailings slurry is discharged in time so that the lateral water pressure on the wall of the silo cannot be formed. These two measures ensure the safety of the silo body structure.

According to the tensile test chart of the laboratory steel bar, if the Q235 low carbon steel is used for the ring body of the warehouse body, when the tensile force reaches the yield limit, the corresponding elongation is about 0.1%, and when the tensile strength reaches the strength limit. The elongation is about 16%, and very obvious tensile deformation occurs during this process. Therefore, it is not necessary to calculate the force of the inner wall of the warehouse, as long as the tensile deformation of the cylinder ring is observed daily to grasp the safety of the structure of the warehouse.

After the silo is filled, it can be covered without exposing the evaporation of water. In case of heavy rain or to avoid dust pollution, cover it again.

2.2 Peripheral phase

When all the silos are filled, entering the synthesizing stage, it is necessary to temporarily recruit a large number of human resources to participate. Due to the need to raise the recovery silo body, 12 people are evenly distributed around the silo. Excavate the tailings at the top of each silo to fill the gap around the silo, and then compact the lower throwing filler. Each time 0.75 meters is filled, a block body is removed from the bottom up, and a vertical soft water pipe along the inner wall of the silo with an elevation of 0.3 m or more is removed. The above process is repeated until the gap between the adjacent cartridge bodies is completely filled, and the cartridge body is completely removed and recovered.

Simultaneously with the above process, there is also a masonry stone slope protection along the landfill. The slope height rises with the surface of the tailings. When all the gaps between adjacent silos are filled, the slope protection is also increased. To the top. The bulldozer leveles the working surface according to the design elevation, forming the highest part in the middle of the landfill and forming a 1% drainage slope around. After leveling and compacting, the 1mm HDPE film is paved to form a waterproof cushion, and the soft water pipe is evenly distributed on the cushion according to the design.

Finally, the spare earthwork outside the field is backfilled on the waterproof cushion, and the thickness is about 0.6 meters. The shallow roots and flowers can be planted on the soil layer.

The synthetic phase should avoid the rainy season and be completed within 1 month as much as possible.

In the landfill stage, the silo elevation of each silo is 23.5 meters. After the synthetic type, the average elevation of the top surface of the silo is about 20.1 meters (including the thickness of the covering layer is 0.6 meters).

3. New technology superiority

The superiority of new technology is mainly reflected in:

3.1 The tailings pond is absolutely safe and reliable, mainly in:

3.1.1 After the landfill is formed, the top of the landfill is provided with waterproof gaskets and horizontally permeable pipes to effectively prevent rainfall intrusion;

3.1.2 Although the vertical permeable pipes along the periphery of the silo are recovered in the synthetic stage of the landfill, the vertical permeable pipes in the center of each silo are not recoverable and remain in the tailings pile, so the pile There are still many vertical permeable pipes evenly distributed to ensure that there is no water in the pile permanently;

3.1.3 Since a large number of reinforced rings are placed in the tailings pile to form a plurality of independent consolidated bodies, it is impossible to have slip rupture surfaces in the pile.

3.2 Good environmental benefits: Since the filling work surface can be covered at any time during the landfill filling stage and the sealing is carried out after the synthetic type, the environmental benefits can reach zero pollution.

3.3 Low project cost: According to the example of this project, the cost per cubic meter is about 36 yuan without considering the recycling of the warehouse. If the silo body is recovered at 70% depreciation, the cost per cubic meter is about 19.6 yuan. In addition, in the implementation process, it can also be implemented in stages, and the silo body recovered after the completion of the previous implementation is used for later implementation, which can further reduce the project cost.

3.4 Saving land: The existing reservoir area can be used.

4. Optional options

4.1 During the landfill filling, since the rain enters the silo is very limited, mainly to prevent dust pollution, so the top of the silo can be covered without HDPE film, covered with straw curtain. In this way, the waterproof mat layer on the top surface of the landfill after the synthetic type can all adopt the new material HDPE film, and the splicing is simple and more durable.

4.2 The inner wall of the silo is not HDPE membrane, and it is changed into geogrid and permeable geotextile to form the permeable silo body, so that the vertical soft water permeable pipe installed along the inner wall of the silo can be omitted. This scheme can reduce the construction cost, but only if the tailings water directly oozing from the silo body can not pollute the environment.

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