A self-filling method for abandoned coal mine

Abstract

The present invention discloses a method for self-filling abandoned coal mine cavities, which is characterized by including the following steps: measuring and calculating the amount of mine wastewater generated, adding an oxidant into the wastewater, with a reaction time of 2 to 3 hours; after the oxidant has completely reacted, adding a fine swelling agent and a fine neutralizing agent into the wastewater simultaneously, with a reaction time of 5 to 6 hours; adding a coarse swelling agent and a coarse neutralizing agent into the wastewater simultaneously, with a reaction time of 5 to 6 hours; after the mine cavity is filled, applying a leaching prevention material to its surface. The present invention selects a mixture of limestone and slaked lime as the neutralizing agent, which has a better treatment effect on sulfate ions; the swelling agent can generate a large amount of precipitation, accelerating the filling speed of the mine cavity; it has a significant effect on removing H+ and metal ions; the particle size is smaller, the reaction is more complete, improving the utilization rate of raw materials; it fills the goaf and roadway of the coal mine cavity, effectively preventing and eliminating the occurrence of geological disasters.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine cave repair, and in particular relates to a method for self-filling an abandoned coal mine cave. Background Art

[0002] During the mining process of coal mines, a large number of sulfide minerals (such as pyrrhotite, chalcopyrite and pyrite, among which pyrite is the main one) that originally existed stably in a reducing environment are exposed to an environment with oxygen (water and air). Then, under the combined action of water, air and bacteria, the sulfide minerals generate a large amount of ferrous iron, sulfate and acidic substances, and at the same time, a large amount of heavy metal ions (such as Fe, Mn, Cu, etc.) are leached, thus producing mine wastewater with high acidity and containing heavy metals. Mine wastewater has the characteristics of high SS content, low pH and high content of heavy metals such as Fe and Mn.

[0003] Usually, the wastewater from abandoned mines is not treated and directly enters the environment, which causes serious pollution to the water environment in mountainous areas and affects the irrigation water downstream of mine drainage. This type of wastewater has the characteristics of dispersed discharge and long-lasting, and is not easy to be collected and centrally treated, becoming one of the important sources of water pollution.

[0004] Abandoned coal mines, under the scouring of rainwater and groundwater, not only will acid mine drainage be produced, but the mines left behind are also a potential geological disaster (ground collapse). For acid mine drainage, the current treatment methods are mostly to introduce acid mine drainage into the constructed reaction pool, and then purify the water body through oxidation precipitation, neutralization reaction and wetland treatment. This type of method has good treatment effect and mature application, but the wastewater generated by small historical mines is widely distributed and difficult to collect. The above methods will have problems of complex operation and high cost; and the existing research on mine filling is relatively limited, and most of them are applied to the field of large mines. Therefore, it is urgent to find a simple, easy-to-operate and economically feasible method to gradually fill the mine while treating the acid wastewater generated in small abandoned mines to prevent the occurrence of geological disasters.

[0005] Therefore, in order to solve the above problems, this paper proposes a method for self-filling of abandoned coal mine caves. Summary of the invention

[0006] In order to solve the above technical problems, the present invention designs a method for self-filling abandoned coal mine caves. The present invention adds an oxidant, an expander and a neutralizer to the acid mine wastewater, which can effectively remove H + , so that the dissolved metal ions are removed in the form of hydroxide, sulfate precipitation and zeolite adsorption. This process effectively treats the acidic wastewater. At the same time, the resulting precipitate does not require additional treatment and also fills the mine cave, avoiding the occurrence of geological disasters.

[0007] In order to achieve the above technical effects, the present invention is implemented by the following technical solutions: a method for self-filling of abandoned coal mine caves, characterized in that it includes the following steps:

[0008] Step 1: Install 5 storage tanks outside the mine, and store oxidant, fine expander, coarse expander, fine neutralizer, and coarse neutralizer in the storage tanks respectively;

[0009] Step 2: Measure and calculate the amount of mine wastewater generated, based on 20-150g / m 3 The oxidant is added into the wastewater, and the reaction time is 2 to 3 hours; when the oxidant reacts completely, the oxidant is added at 2 to 5 kg / m 3 The fine expansion agent is adjusted to 9.0-12.0 kg / m 3 Add fine neutralizer into wastewater at the same time, the reaction time is 5-6 hours; press 2-5kg / m 3 The coarse expansion agent is adjusted to 9.0-12.0 kg / m 3 Add the crude neutralizer into the wastewater at the same time, and the reaction time is 5 to 6 hours;

[0010] Step 3: Use tailings to fill the mine cave until it is full and apply anti-leaching material on its surface.

[0011] Furthermore, in the Step 1, the particle size of the oxidant is 80-150 μm, the particle size of the fine expander is 500-600 μm, the particle size of the coarse expander is 600-900 μm, the particle size of the fine neutralizer is 300-450 μm, and the particle size of the coarse neutralizer is 450-850 μm.

[0012] Furthermore, the neutralizer is mixed with limestone and slaked lime, the mass ratio of limestone to slaked lime is 1.5-2:1-1.5, the mixture is dried at a temperature of 150-200°C, and after drying, the mixture is ground into a fine neutralizer with a particle size of 300-450 μm and a coarse neutralizer with a particle size of 450-850 μm.

[0013] Furthermore, the oxidant is prepared by mixing calcium peroxide, sodium hydroxide and water, and the mass ratio of calcium peroxide, sodium hydroxide and water is 70-80:10-15:10-15; then it is placed in an environment with a temperature of 280-360°C for drying, and after drying, the mixture is ground into particles with a particle size of 80-150μm.

[0014] Furthermore, the expansion agent is made by mixing zeolite, montmorillonite and organic matter, and the mass ratio of zeolite, montmorillonite and organic matter is 10-15:50-60:40-45; the mixture is placed in an environment with a temperature of 80-120°C for drying, and after drying, the mixture is ground into a fine expansion agent with a particle size of 500-600μm and a coarse expansion agent with a particle size of 600-900μm.

[0015] Furthermore, in the neutralizer, the purity of limestone calcium carbonate is greater than 90%, and the purity of calcium hydroxide in slaked lime is greater than 95%.

[0016] Furthermore, the storage tank is a vertical storage tank, the tank body is made of polypropylene with acid and alkali resistance, high mechanical strength and good high wear resistance, and needs to be equipped with a support made of stainless steel with a height of 50cm; the installation position of the storage tank is at the top of the mine, and the ground load range of this position should be greater than 2t / m 2 , the seismic fortification intensity of the geological structure should be greater than 6 degrees.

[0017] Furthermore, a conveyor belt for transporting materials into the wastewater is installed at the discharge port of the storage tank.

[0018] Furthermore, the anti-leaching material is epoxy resin, the coating thickness is 1mm, and the usage is 1kg / m 2 .

[0019] Furthermore, the ash-sand ratio in the tailings is in the range of 1:4 to 8, and the filling concentration is 64% to 68%; the cementitious material in the tailings is alkali-activated cementitious material, and the alkali-activated gel material is composited by 85% slag, 5% lime, 5% gypsum, 3% sodium sulfate and 2% cement clinker.

[0020] The beneficial effects of the present invention are:

[0021] The present invention uses a mixture of limestone and slaked lime as a neutralizing agent, which reduces the cost and has a better treatment effect on sulfate radicals; the expansion agent is mainly composed of cheap and readily available biomass, and can produce a large amount of precipitation, thereby accelerating the filling speed of the mine hole; + The effect of removing metal ions is remarkable; the particle size is small, the reaction is more complete, the precipitation coverage that slows down the reaction rate is avoided, and the utilization rate of raw materials is improved; the precipitation generated in the reaction process is used to fill the goaf and tunnels of the mine, effectively preventing and eliminating the occurrence of geological disasters; the raw materials used in the present invention are widely available, low in price, simple in process, easy to operate, and the sludge generated in the reaction is utilized as a resource in situ. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0023] Figure 1 is a flow chart of the present invention;

[0024] Figure 2 It is a schematic diagram of the storage tank structure. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] The size of the historical coal mine cave is 30 to 200m 3 , the amount of wastewater generated is 10~100m 3 / dThe pH value of the cave wastewater is 2-4, the SS value is 150-300 mg / L, the total iron content TFe value is 200-300 mg / L, and the total manganese content TMn value is 15-30 mg / L.

[0028] The specific steps include: the oxidant is put into the tunnel of the coal mine from the top of the mine through the automatic discharging device, and after the reaction for 2 hours, an appropriate amount of expander with a particle size range of 500-600μm and a fine neutralizer with a particle size range of 300-450μm are put into the coal mine, and the reaction time is 5 hours; finally, the expander with a particle size range of 600-900μm and the coarse neutralizer with a particle size range of 450-850μm are put into the mine, and the reaction time is 5 hours; the above reagents reach the bottom of the mine by their own gravity and the scouring effect of rainwater and mountain seepage; the oxidant oxidizes a large amount of Fe 2+ , expanders and neutralizers react with acid mine drainage and Fe 3+ , Mn 2+ The metal ions generate hydroxide precipitates and the sulfate ions generate calcium sulfate precipitates. The montmorillonite and biomass in the expander absorb water and swell to generate a large amount of precipitates, while adsorbing heavy metals and SS. The treated wastewater flows out of the mine and into the surrounding environment, and the generated precipitates fill the goaf and tunnels of the mine.

[0029] The dosage of oxidant is 100g / m 3 (water), the ratio of calcium peroxide, calcium hydroxide and water is 70:15:15; the amount of expansion agent is 3.5kg / m 3 (water), the ratio of zeolite, montmorillonite and biomass is 10:50:40; the amount of neutralizer is 10.5kg / m 3 (water), with limestone and slaked lime in a ratio of 2:1.

[0030] Example 2

[0031] The size of the historical coal mine cave is 30 to 200m 3 , the amount of wastewater generated is 10~100m 3 / dThe pH value of the cave wastewater is 2-4, the SS value is 150-300 mg / L, the total iron content TFe value is 200-300 mg / L, and the total manganese content TMn value is 15-30 mg / L.

[0032] The specific steps include: the oxidant is put into the tunnel of the coal mine from the top of the mine through the automatic discharging device, and after the reaction for 2 hours, an appropriate amount of expander with a particle size range of 500-600μm and a fine neutralizer with a particle size range of 300-450μm are put into the coal mine, and the reaction time is 5 hours; finally, the expander with a particle size range of 600-900μm and the coarse neutralizer with a particle size range of 450-850μm are put into the mine, and the reaction time is 5 hours; the above reagents reach the bottom of the mine by their own gravity and the scouring effect of rainwater and mountain seepage; the oxidant oxidizes a large amount of Fe 2+ , expanders and neutralizers react with acid mine drainage and Fe 3+ , Mn 2+ The metal ions generate hydroxide precipitates and the sulfate ions generate calcium sulfate precipitates. The montmorillonite and biomass in the expander absorb water and swell to generate a large amount of precipitates, while adsorbing heavy metals and SS. The treated wastewater flows out of the mine and into the surrounding environment, and the generated precipitates fill the goaf and tunnels of the mine.

[0033] The amount of oxidant added is 80g / m 3 (water), the ratio of calcium peroxide, calcium hydroxide and water is 70:15:15; the amount of expansion agent is 3.5kg / m 3 (water), the ratio of zeolite, montmorillonite and biomass is 10:50:40; the amount of neutralizer is 10.5kg / m 3 (water), with limestone and slaked lime in a ratio of 2:1.

[0034] Example 3

[0035] The size of the historical coal mine cave is 30 to 200m 3 , the amount of wastewater generated is 10~100m 3 / dThe pH value of the cave wastewater is 2-4, the SS value is 150-300 mg / L, the total iron content TFe value is 200-300 mg / L, and the total manganese content TMn value is 15-30 mg / L.

[0036] The specific steps include: the oxidant is put into the tunnel of the coal mine from the top of the mine through the automatic discharging device, and after the reaction for 2 hours, an appropriate amount of expander with a particle size range of 500-600μm and a fine neutralizer with a particle size range of 300-450μm are put into the coal mine, and the reaction time is 5 hours; finally, the expander with a particle size range of 600-900μm and the coarse neutralizer with a particle size range of 450-850μm are put into the mine, and the reaction time is 5 hours; the above reagents reach the bottom of the mine by their own gravity and the scouring effect of rainwater and mountain seepage; the oxidant oxidizes a large amount of Fe 2+ , expanders and neutralizers react with acid mine drainage and Fe 3+ , Mn 2+ The metal ions generate hydroxide precipitates and the sulfate ions generate calcium sulfate precipitates. The montmorillonite and biomass in the expander absorb water and swell to generate a large amount of precipitates, while adsorbing heavy metals and SS. The treated wastewater flows out of the mine and into the surrounding environment, and the generated precipitates fill the goaf and tunnels of the mine.

[0037] The dosage of oxidant is 150g / m 3 (water), the ratio of calcium peroxide, calcium hydroxide and water is 70:15:15; the amount of expansion agent is 3.5kg / m 3 (water), the ratio of zeolite, montmorillonite and biomass is 10:50:40; the amount of neutralizer is 10.5kg / m 3 (water), with limestone and slaked lime in a ratio of 2:1.

[0038] Example 4

[0039] The size of the historical coal mine cave is 30 to 200m 3 , the amount of wastewater generated is 10~100m 3 / dThe pH value of the cave wastewater is 2-4, the SS value is 150-300 mg / L, the total iron content TFe value is 200-300 mg / L, and the total manganese content TMn value is 15-30 mg / L.

[0040] The specific steps include: the oxidant is put into the tunnel of the coal mine from the top of the mine through the automatic discharging device, and after the reaction for 2 hours, an appropriate amount of expander with a particle size range of 500-600μm and a fine neutralizer with a particle size range of 300-450μm are put into the coal mine, and the reaction time is 5 hours; finally, the expander with a particle size range of 600-900μm and the coarse neutralizer with a particle size range of 450-850μm are put into the mine, and the reaction time is 5 hours; the above reagents reach the bottom of the mine by their own gravity and the scouring effect of rainwater and mountain seepage; the oxidant oxidizes a large amount of Fe 2+, expanders and neutralizers react with acid mine drainage and Fe 3+ , Mn 2+ The metal ions generate hydroxide precipitates and the sulfate ions generate calcium sulfate precipitates. The montmorillonite and biomass in the expander absorb water and swell to generate a large amount of precipitates, while adsorbing heavy metals and SS. The treated wastewater flows out of the mine and into the surrounding environment, and the generated precipitates fill the goaf and tunnels of the mine.

[0041] The dosage of oxidant is 100g / m 3 (water), the ratio of calcium peroxide, calcium hydroxide and water is 70:15:15; the amount of expansion agent is 3.5kg / m 3 (water), wherein the ratio of zeolite, montmorillonite and biomass is 10:50:40; the amount of neutralizer added is 9.0 kg / m 3 (water), with limestone and slaked lime in a ratio of 2:1.

[0042] Example 5

[0043] The size of the historical coal mine cave is 30 to 200m 3 , the amount of wastewater generated is 10~100m 3 / dThe pH value of the cave wastewater is 2-4, the SS value is 150-300 mg / L, the total iron content TFe value is 200-300 mg / L, and the total manganese content TMn value is 15-30 mg / L.

[0044] The specific steps include: the oxidant is put into the tunnel of the coal mine from the top of the mine through the automatic discharging device, and after the reaction for 2 hours, an appropriate amount of expander with a particle size range of 500-600μm and a fine neutralizer with a particle size range of 300-450μm are put into the coal mine, and the reaction time is 5 hours; finally, the expander with a particle size range of 600-900μm and the coarse neutralizer with a particle size range of 450-850μm are put into the mine, and the reaction time is 5 hours; the above reagents reach the bottom of the mine by their own gravity and the scouring effect of rainwater and mountain seepage; the oxidant oxidizes a large amount of Fe 2+ , expanders and neutralizers react with acid mine drainage and Fe 3+ , Mn 2+ The metal ions generate hydroxide precipitates and the sulfate ions generate calcium sulfate precipitates. The montmorillonite and biomass in the expander absorb water and swell to generate a large amount of precipitates, while adsorbing heavy metals and SS. The treated wastewater flows out of the mine and into the surrounding environment, and the generated precipitates fill the goaf and tunnels of the mine.

[0045] The dosage of oxidant is 100g / m 3(water), the ratio of calcium peroxide, calcium hydroxide and water is 70:15:15; the amount of expansion agent is 3.5kg / m 3 (water), wherein the ratio of zeolite, montmorillonite and biomass is 10:50:40; the amount of neutralizer added is 12.0 kg / m 3 (water), with limestone and slaked lime in a ratio of 2:1.

[0046] Example 6

[0047] The other conditions and steps were the same as those in Example 1, except that the ratio of limestone to slaked lime in the neutralizer was 1:1.

[0048] Example 7

[0049] The other conditions and steps were the same as those in Example 1, except that the ratio of limestone to slaked lime in the neutralizer was 3:1.

[0050] Example 8

[0051] The other conditions and steps are the same as those in Example 1, except that the reaction time after adding a 500-600 μm expander and a 300-450 μm fine neutralizer is 3 h; the reaction time after adding a 600-900 μm expander and a coarse neutralizer with a particle size range of 450-850 μm is 7 h.

[0052] Example 9

[0053] The other conditions and steps are the same as those in Example 1, except that the reaction time after adding a 500-600 μm expander and a 300-450 μm fine neutralizer is 7 hours; the reaction time after adding a 600-900 μm expander and a coarse neutralizer with a particle size range of 450-850 μm is 3 hours.

[0054] The treatment effects and slag production rates of acid mine wastewater under different process conditions in Examples 1 to 9 are shown in Table 1:

[0055]

[0056]

[0057] From Table 1, it can be seen that the pH value of the treated acid mine wastewater can be increased to 7-8.2, the removal rate of TFe can reach 92% and above, the removal rate of TMn can reach 83% and above, and the slag production can reach 27-31kg / m 3 .

[0058] From the treatment effects and slag production rates of acid mine drainage water under different process conditions in different embodiments in Table 1, it can be seen that the acid wastewater treatment effects and slag production rates of Embodiments 1, 3, 5, 8 and 9 are the best, but compared with Embodiment 1, under similar treatment effects: the amount of oxidant used in Embodiment 3 is almost twice, and the raw material cost is high; the amount of neutralizer added in Embodiment 5 is more, and the cost is too high; the treatment effects and slag production rates of the processes in Embodiments 8 and 9 are not as good as those in Embodiment 1. In terms of comprehensive economy, treatment effect and slag production rate, Embodiment 1 is the most preferred process.

[0059] Example 10

[0060] The invention uses a mixture of limestone and slaked lime as a neutralizer. Compared with the traditional lime neutralization method, the invention has the advantage of using cheap limestone that has a significant effect on sulfate removal to replace part of the expensive lime. Studies have shown that the mixed method can achieve the same treatment effect with only 2 / 3 of the amount of lime used in the original lime neutralization method, and has a better treatment effect on sulfate. The mixed method can reduce the treatment cost by 30%.

[0061] The expander used in the present invention is mainly composed of cheap and easily available biomass, and can produce a large amount of precipitation to accelerate the filling speed of the mine. The oxidant, expander and neutralizer in the present invention can be used for acid mine wastewater treatment to increase the pH value of the mine water to 7-9, the TFe removal rate reaches 98.75%, the manganese removal rate reaches 91.02%, and the sulfate removal rate reaches 65%.

[0062] The particle size of the neutralizer is limited to 300-850 μm, so that the neutralizer can react more fully with the acid mine wastewater, and the problem of the generated precipitate covering the surface of the limestone to form a coating can be effectively reduced, thereby improving the utilization rate of the limestone.

[0063] The neutralizing agent in the present invention is delivered by an automatic delivery device and a crawler conveyor, wherein the energy of the automatic delivery device comes from a solar power supply system, thus effectively saving manpower, thereby reducing operating costs and manpower costs.

[0064] Compared with traditional research that only focuses on the treatment of acid mine drainage, the present invention not only effectively treats acid mine drainage and avoids the pollution of the surrounding environment by acid mine drainage, but also uses the precipitation produced in its reaction process to fill the goaf and tunnels of the mine, effectively preventing and eliminating the occurrence of geological disasters.

[0065] The raw materials used in the present invention are widely available and inexpensive, the process is simple, the operation is convenient, the equipment is reusable and occupies a small area, the operating cost is low, and the sludge produced in the reaction is recycled in situ, which has strong practicality in this technical field.

Claims

1. A method for self-filling abandoned coal mine caves, characterized in that: The following steps are involved: Step 1: Install 5 storage tanks outside the mine, and store oxidant, fine expander, coarse expander, fine neutralizer, and coarse neutralizer in the storage tanks respectively; Step 2: Measure and calculate the amount of mine wastewater generated, based on 20-150g / m 3 The oxidant is added into the wastewater, and the reaction time is 2 to 3 hours; when the oxidant reacts completely, the oxidant is added at 2 to 5 kg / m 3 The fine expansion agent is adjusted to 9.0-12.0 kg / m 3 Add fine neutralizer into wastewater at the same time, the reaction time is 5-6 hours; press 2-5kg / m 3 The coarse expansion agent is adjusted to 9.0-12.0 kg / m 3 Add the crude neutralizer into the wastewater at the same time, and the reaction time is 5 to 6 hours; Step 3: Use tailings to fill the mine cave until it is full and apply anti-leaching material on its surface.

2. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: In the Step 1, the particle size of the oxidant is 80-150 μm, the particle size of the fine expander is 500-600 μm, the particle size of the coarse expander is 600-900 μm, the particle size of the fine neutralizer is 300-450 μm, and the particle size of the coarse neutralizer is 450-850 μm.

3. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: The neutralizer is prepared by mixing limestone and slaked lime, wherein the mass ratio of limestone to slaked lime is 1.5-2:1-1.

5. The mixture is dried at a temperature of 150-200° C., and after drying, the mixture is ground into a fine neutralizer with a particle size of 300-450 μm and a coarse neutralizer with a particle size of 450-850 μm.

4. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: The oxidant is prepared by mixing calcium peroxide, sodium hydroxide and water, wherein the mass ratio of calcium peroxide, sodium hydroxide and water is 70-80:10-15:10-15; the oxidant is then dried in an environment at a temperature of 280-360°C, and after drying, the mixture is ground into particles with a particle size of 80-150 μm.

5. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: The expansion agent is prepared by mixing zeolite, montmorillonite and organic matter, wherein the mass ratio of zeolite, montmorillonite and organic matter is 10-15:50-60:40-45; the mixture is placed in an environment with a temperature of 80-120°C for drying, and after drying, the mixture is ground into a fine expansion agent with a particle size of 500-600μm and a coarse expansion agent with a particle size of 600-900μm.

6. The method for self-filling an abandoned coal mine according to claim 3, characterized in that: In the neutralizer, the purity of limestone calcium carbonate is greater than 90%, and the purity of calcium hydroxide in slaked lime is greater than 95%.

7. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: The storage tank is a vertical storage tank. The tank body is made of polypropylene, which is acid and alkali resistant, has high mechanical strength and good high wear resistance. It needs to be equipped with a support made of stainless steel with a height of 50cm. The installation position of the storage tank is at the top of the mine, and the ground load range of this position is greater than 2t / m 2 , the seismic fortification intensity of the geological structure is greater than 6 degrees.

8. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: A conveyor belt for transporting materials into the wastewater is installed at the material storage tank outlet; a solar power supply system is arranged on the material storage tank.

9. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: The anti-leaching material is epoxy resin, the coating thickness is 1mm, and the usage is 1kg / m 2 .

10. The method for self-filling an abandoned coal mine according to claim 1, characterized in that: The ash-sand ratio of the tailings is in the range of 1:4-8, and the filling concentration is 64%-68%; the cementitious material in the tailings is an alkali-activated cementitious material composed of 85% slag, 5% lime, 5% gypsum, 3% sodium sulfate and 2% cement clinker.

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