Combined treatment process for water area foundation treatment of tailing pond closed reservoir project

Abstract

The invention relates to a combined treatment process for treating a water area foundation of a tailing pond closed reservoir project, which is characterized in that a transverse drainage system is formed by arranging a filler layer, and an efficient transverse permeation channel is constructed through natural pores among fillers, so that saturated water in tailings at the lower part is quickly discharged through the material pores, and transverse drainage is realized; and the filler can also be used as a foundation bearing layer to directly improve the foundation bearing capacity, reduce the settling volume and provide support for subsequent construction. Meanwhile, a vertical drainage system is further arranged, a plurality of steel pipe seepage wells are evenly distributed in a to-be-treated area, drained seepage water can be concentrated into the steel pipe seepage wells in the treatment process, then the seepage water is transferred in a unified mode through a pump, and centralized treatment is facilitated. The method does not need to depend on a negative pressure environment, does not need to arrange a film for sealing, effectively avoids the influence of continuous water supply of an underground water system on treatment, and is more suitable for a land environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tailing pond closure engineering, and particularly relates to a combined treatment process for water area foundation treatment of tailing pond closure engineering. BACKGROUND

[0002] A tailing pond is an important production facility of a mine and a major hazard source, and generally has a dam height of dozens of meters to hundreds of meters. According to relevant specifications for tailing ponds, a tailing pond that has reached the design final elevation, no longer discharges tailings, and has been idle for more than 3 years or the monthly production and operation subject of the tailing pond should be promptly closed and treated and canceled. According to the Overall Scheme for Tailing Pond Risk and Hidden Danger Treatment issued by the State Mine Safety Supervision Bureau and the Ministry of Finance in 2022, there are about 900 tailing ponds in China that need to be closed, accounting for about 18.3% of the total number of tailing ponds under the supervision of the national safety supervision, and if long-term idle tailing ponds with outstanding risk and hidden dangers are added, the number of tailing ponds that need to be closed will be even more.

[0003] The dewatering and drainage of the tail water area region of an upstream tailing pond and the foundation treatment are difficult points of the entire closure engineering. The tail sand in this region has a very high water content and is often in a saturated state, and the tailing particle size is fine, belonging to saturated soft soil foundation with extremely poor bearing capacity. During the closure construction process, safety accidents such as personnel drowning, mechanical vehicle subsidence, and local liquefaction of tailing sand are easily caused, which not only seriously affects the construction progress, but also threatens the safety of the dam body during construction. Even if all the clear water in the pond is pumped out before construction, the beach surface appears obvious dry cracking phenomenon, and the bearing capacity of the foundation still cannot meet the operation requirements of the closure construction. Therefore, in order to stabilize the soft foundation in advance, speed up the construction progress, ensure the construction safety, and at the same time minimize the post-construction settlement risk of the foundation after the closure, efficient and thorough treatment of the soft tail sand layer in the water-covered area has become a core technical bottleneck that needs to be broken through for the closure engineering of an upstream tailing pond.

[0004] Among traditional treatment methods for saturated soft soil foundations, vacuum preloading is widely used. It is suitable for large-area soft soil foundation treatment. The core principle involves setting up vertical drainage channels such as sand wells, bagged sand wells, or plastic drainage boards in the soft soil foundation to be reinforced. Then, a sand cushion layer is laid on the ground and covered with an impermeable membrane. A vacuum is created to form negative pressure, causing pore water in the soil to gradually seep into the vertical drainage channels, thereby achieving soil drainage consolidation and strength increase. While this method can meet the needs of foundations of varying thicknesses and can reinforce relatively thick areas, it is widely used in soft soil areas in the south and coastal regions. However, when applied to inland areas, the terrain is often more complex than in the coast, with depressions and protrusions, making the sealing membrane installation difficult, resulting in a high breakage rate and significantly increased sealing costs. Furthermore, the strong connectivity between the tailings layer and the surrounding groundwater system in inland tailings ponds can lead to rapid groundwater replenishment during the vacuuming process, making it difficult to maintain negative pressure and achieve the desired reinforcement effect. Therefore, this application proposes a combined treatment process for the water foundation management of tailings pond closure projects. Summary of the Invention

[0005] The purpose of this invention is to provide a combined treatment process for the basic management of the water area in tailings dam closure projects, so as to adapt to tailings dam closure projects in inland areas.

[0006] To achieve the above objectives, the technical solution adopted by this invention is a combined treatment process for the basic management of the water area in a tailings dam closure project, characterized by the following steps:

[0007] Step 1: Fill the area to be treated with filler material to form a filler layer;

[0008] Step 2: Evenly distribute steel pipe seepage wells in the area to be treated;

[0009] Step 3: Compact the filler layer using dynamic compaction technology;

[0010] Step 4: While compacting the surface, use a water pump to remove the water from each steel pipe seepage well until there is no water left in the well, then the treatment is complete.

[0011] The technical features of the present invention also include:

[0012] The filler in step 1 is rubble. The rubble contains more than 50% of particles with a diameter greater than 200mm by weight, and the maximum particle size does not exceed 800mm.

[0013] In step 1, when the content of -200 mesh tailings in the area to be treated is between 69.2% and 80%, a 1.5m thick filler layer is used; when the content of -200 mesh tailings in the area to be treated is above 80%, a 2.5m thick filler layer is used.

[0014] Step 1 is to fill the material in the filling process according to the terrain from high to low, and when the filler layer of a part of the area reaches the specified thickness, the filling of another part of the area is carried out, and the filler layer formed covers the entire area to be treated.

[0015] In step 2, a steel pipe water seepage well is arranged in each 15m*15m area in the area to be treated, and in the construction process, a cycle of 4-6 hours is taken, and when the water seepage amount per hour in a cycle does not decrease, the steel pipe water seepage well can be increased, when the water seepage amount per hour in a cycle decreases by less than 80%, the current number of steel pipe water seepage wells is maintained, and when the water seepage amount per hour in a cycle decreases by more than 80%, the number of steel pipe water seepage wells can be reduced.

[0016] In step 3, when the ramming point is arranged in a plum blossom shape during ramming, the ramming is stopped when the ramming settlement is not greater than 50mm for two times in succession.

[0017] In step 4, a cycle of 4-6 hours is taken in the construction process, and when the water seepage amount per hour in a cycle does not decrease, the steel pipe water seepage well can be increased, when the water seepage amount per hour in a cycle decreases by less than 80%, the current number of steel pipe water seepage wells is maintained, and when the water seepage amount per hour in a cycle decreases by more than 80%, the number of steel pipe water seepage wells can be reduced.

[0018] In step 4, the accumulated water in each water seepage well is pumped out and stored.

[0019] Compared with the prior art, the combined treatment process for the water area foundation treatment of the tailing pond closing project has the following advantages:

[0020] 1. In the application, the rough stone is used as the filling material, the characteristics of rich reserves of mine rough stone materials are fully utilized, the raw material procurement cost is greatly reduced, and the aggregate self-weight is used to realize the extrusion and replacement of silt. After the material is filled to the preset thickness, a strong ramming process is used for accurate ramming treatment to form a stable riprap structure, which directly improves the foundation bearing capacity and reduces the settlement amount as the foundation bearing layer, and constructs an efficient horizontal permeation channel between the aggregates to make the saturated water in the lower tailings quickly pass through the material pores and be discharged, thereby realizing the speed-up of horizontal drainage.

[0021] 2. In the application, the uniformly arranged steel pipe water seepage well continuously collects the saturated water of the surrounding tailings under the action of the pressure difference and gravity during the filling and ramming process, and then the accumulated water in the water seepage well is pumped out through the sewage pump, so that the discharge rate of the accumulated water is improved, and the steel pipe water seepage well can be recycled as the construction process continues, thereby greatly reducing the construction cost.

[0022] 3. The treatment method provided by the present application does not need to rely on a negative pressure environment, and the groundwater system has a small influence on the treatment method, and meanwhile, the porosity of the filler layer is high and the permeability is strong, which is equivalent to constructing a vertical rigid drainage channel in the tailings layer, so that the pore water in the tailings layer can be quickly discharged, and the recharge water flow of the groundwater system can be guided into the gravel pier to avoid the low strength caused by the retention of water in the tailings layer. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a geological condition map before treatment;

[0024] Figure 2 is a real scene map after treatment by the method. DETAILED DESCRIPTION

[0025] The present application will be further described below in combination with specific embodiments.

[0026] A combined treatment process for water area foundation treatment of tailings pond closure engineering is carried out according to the following steps:

[0027] Step 1: A steel pipe water infiltration well is arranged in each 15m x 15m area in the region to be treated.

[0028] Step 2: The content of tailings of-200 purpose in different positions in the entire region to be treated is detected, and the filler is thrown to form a filler layer in the region to be treated in the order from high to low, the filler layer of one position reaches the specified thickness, and then another position is thrown, until the entire region to be treated is completed, when the content of tailings of-200 purpose in the region to be treated is 69.2% to 80%, a filler layer with a thickness of 1.5m is used, and when the content of tailings of-200 purpose in the region to be treated is more than 80%, a filler layer with a thickness of 2.5m is used.

[0029] Step 3: The filler layer is treated by using the dynamic compaction process, and the ramming points are arranged in a plum blossom shape, and when the ramming amount of continuous two times is not more than 50mm, the ramming is stopped.

[0030] Step 4: While the ramming treatment is being carried out, the water in each steel pipe water infiltration well is pumped out and stored by using a water pump, and in the construction process, 4 to 6 hours is taken as a period, when the water infiltration amount per hour in a period does not decrease, the number of steel pipe water infiltration wells can be increased, when the decrease amplitude of water infiltration amount per hour in a period is less than 80%, the current number of steel pipe water infiltration wells is maintained, and when the decrease amplitude of water infiltration amount per hour in a period is more than 80%, the number of steel pipe water infiltration wells can be reduced, until there is no water accumulation in the steel pipe water infiltration well, and the treatment is completed.

[0031] In the process of using the tailings pond, the tailings slurry flows from top to bottom and is stacked on the dam to the water retaining dam. In this process, the coarse grain particles will settle before the fine grain particles. Therefore, in the high terrain area, the coarse grain particles are mainly stacked, and in the low terrain area, the fine grain particles are mainly stacked. The coarse grain particles are easy to separate from water due to their large volume. Therefore, when filling the fillers from high to low, the area where the coarse grain particles are located can be preferentially treated to provide a bearing platform for subsequent treatment.

[0032] When the total water seepage amount of the steel pipe water seepage well is reduced by more than 80% in a cycle, it represents that the water content in the stratum at this position is greatly reduced. Therefore, the number of steel pipe water seepage wells can be appropriately reduced to recycle the steel pipe water seepage wells and improve the construction efficiency.

[0033] Embodiment one:

[0034] The present application is actually applied to the water area treatment of the Shibahe tailings pond closure project. Before treatment, as shown in Figure 1 , the following steps are performed during specific execution:

[0035] Step 1: Since the location of the tailings pond is in a south-high and north-low state, the fillers are filled from south to north. Specifically, in the construction process, the thickness of the filler layer gradually transitions from 1.5 m to 2.5 m from south to north, until the fillers completely cover the area to be treated.

[0036] Step 2: After the filler layer is laid, one steel pipe water seepage well is arranged in each 15 m x 15 m area in the area to be treated. A total of 160 steel pipe water seepage wells are used. The steel pipe water seepage well used has a diameter of 325 mm, a pipe wall thickness of 8 mm, and a hole with a diameter of 10 mm is formed on the pipe wall surface.

[0037] Step 3: After the steel pipe water seepage well is installed, the filler layer is compacted using the dynamic compaction process. The single compaction energy is 2000 KN.m, the hammer weight is 18T, the diameter is Φ2.25 m, the drop distance is 11 m, the compaction point spacing is 4.0 m and is arranged in a plum blossom type. When the compaction settlement at the same compaction point is less than or equal to 50 mm for two consecutive times, the compaction at this point is stopped.

[0038] Step 4: While the compaction is being processed, the water pumping end of the water pump is connected to the pipeline, and the pipeline is inserted into the steel pipe water seepage well to pump out the internal water seepage until there is no water accumulation in the steel pipe water seepage well, and the processing is completed.

[0039] After the above processing, the bearing capacity of the area to be treated is greatly improved, and at least 35 tons of weight can be borne, which is convenient for subsequent self-unloading vehicles to carry out soil covering operations in the area, as shown in Figure 2 .

[0040] The method does not need to set a film and does not rely on negative pressure for drainage, effectively avoiding that the film is easily damaged and that the groundwater system is connected with the tailing pond.

Claims

1. A combined treatment process for the foundation treatment of water areas of tailings pond closure projects, characterized in that, The following steps are taken: Step 1: throw fillers to the area to be treated to form a filler layer; Step 2: evenly arrange steel pipe water infiltration wells in the area to be treated; Step 3: use the strong ramming process to compact the filler layer; Step 4: while compacting, use a water pump to pump out the water in each steel pipe water infiltration well until there is no water accumulation in the steel pipe water infiltration well, and then complete the treatment.

2. The combined treatment process for the water area foundation treatment of tailings pond closure engineering according to claim 1, characterized in that, The filler in step 1 is rough stone, and the content of particles with a particle size greater than 200 mm in the rough stone used is more than 50% of the total weight, and the maximum particle size is not more than 800 mm.

3. The combined treatment process for the water area foundation treatment of tailings pond closure projects according to claim 1, characterized in that, When the content of tailings with a particle size of -200 in the area to be treated is 69.2%-80%, a filler layer with a thickness of 1.5 m is used, and when the content of tailings with a particle size of -200 in the area to be treated is more than 80%, a filler layer with a thickness of 2.5 m is used.

4. The combined treatment process for the water area foundation treatment of tailings pond closure projects according to claim 1, characterized in that, In step 1, the filler is thrown from high to low according to the terrain during the throwing process, and when the filler layer in a part of the area reaches the specified thickness, the throwing process in another part of the area is carried out, until the filler layer covers the entire area to be treated.

5. The combined treatment process for the water area foundation treatment of tailings pond closure projects according to claim 1, characterized in that, In step 2, one steel pipe water infiltration well is arranged in each 15m×15m area in the area to be treated.

6. The combined treatment process for the water area foundation treatment of tailings pond closure projects according to claim 1, characterized in that, In step 3, the ramming points are arranged in a plum blossom shape during compaction, and when the compaction amount is not more than 50 mm for two consecutive times, the compaction is stopped.

7. The combined treatment process for the water area foundation treatment of tailings pond closure projects according to claim 1, characterized in that, In step 4, a cycle of 4-6 hours is taken during construction, and when the water infiltration amount per hour does not decrease within a cycle, the number of steel pipe water infiltration wells can be increased, when the water infiltration amount per hour decreases by less than 80% within a cycle, the current number of steel pipe water infiltration wells is maintained, and when the water infiltration amount per hour decreases by more than 80% within a cycle, the number of steel pipe water infiltration wells can be reduced.

8. The combined treatment process for the water area foundation treatment of tailings pond closure projects according to claim 1, characterized in that, In step 4, the accumulated water in each water infiltration well is pumped out and stored.

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