A method for blocking pollution of acidic wastewater in abandoned mines

Abstract

The invention discloses a method for blocking acid wastewater pollution in abandoned mines. The method adopts a construction method of mine body pressure grouting, anti-corrosion and anti-seepage barrier layer, anti-seepage concrete section support, clay wall water stopping, concrete wellhead plugging and backfilling, and cave top supplementary grouting to block the pollution of abandoned mine water gushing. The rock walls around the cave are subjected to radial pressure grouting to form a comprehensive barrier to the water gushing. Concrete is poured in the plugging and backfilling section, and the shrinkage joints formed by the shrinkage of the concrete are filled by supplementary grouting on the cave top to ensure that the plugging and backfilling section concrete is integrated with the cave wall after solidification, so as to achieve the best water-blocking and anti-seepage effect. The technical scheme of the invention is safe, reliable, efficient and fast, conforms to relevant national technical specifications, greatly improves the airtightness and firmness of the mine water gushing pollution barrier, and eliminates the pollution risk of abandoned mine water gushing to the environment.

Description

Technical Field

[0001] The invention relates to the technical field of pollution prevention and control of abandoned mines, in particular to a method for blocking pollution of acidic wastewater in abandoned mines. Background Art

[0002] At present, with the exploitation of mineral resources, mines have changed the original groundwater system. Most of the groundwater flows out from the mines. The heavy metal ions, sulfate ions, suspended matter, etc. carried in the outflow process cause great pollution to the surrounding environment. Due to the closure of a large number of mines in China, a large number of abandoned mines have been formed. It is urgent to take pollution barrier measures to control some water-gushing mines.

[0003] The conventional mine pollution barrier method is "brick masonry" or "concrete wall". This method has problems such as easy leakage, difficult construction, and poor barrier effect. Especially in karst areas and broken strata, the existing barrier method has unsatisfactory treatment effect, and the mines after sealing treatment still have great environmental pollution risks. Summary of the invention

[0004] In order to overcome the technical deficiencies of the existing abandoned mine plugging method in the background technology, the present invention provides an abandoned mine acid wastewater pollution blocking method.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for blocking the pollution of acidic wastewater in abandoned mines, which uses a construction method of pressure grouting of mine bodies, anti-corrosion and anti-seepage barrier layers, anti-seepage concrete segment support, clay wall water stopping, concrete wellhead plugging and backfilling, and supplementary grouting on the top of the cave to block the pollution of water inrush in abandoned mines. The pollution blocking method specifically includes the following steps:

[0006] A. Desilting in the tunnel: remove the silt, residue and loose surrounding rock on the ground in the abandoned mine until the fresh bedrock surface of the original stratum of the adit is reached. After cleaning, use a high-pressure water gun to clean the rock wall in the tunnel;

[0007] B. Anti-corrosion and anti-seepage barrier layer: Brick walls are built in the mine to form a water retaining wall. A water guide pipe is preset at the bottom of the water retaining wall and extends to the outside of the wellhead. The water guide pipe is used to guide the water gushing out of the well during the plugging construction process;

[0008] C. Grouting and solidification of cavern body for anti-seepage: After rigid grouting pipes are driven into the top wall and side wall of the mine outside the retaining wall, pressure grouting is carried out. The grouting liquid penetrates, diffuses, fills and compacts in the rock formation, penetrates and drives away the water and air in the loose particles between the cracks of the rock formation, and then fills the gaps. After the grouting liquid solidifies, the loose soil particles between the rock gaps and the original cracks are cemented into a whole, forming the cavern wall grouting section in the well;

[0009] D. Anti-corrosion and anti-seepage concrete plugging: pour anti-corrosion and anti-seepage concrete in the grouting section of the well wall in step C; reinforce and support the wall of the well wall after the grouting section of the well wall is solidified to form a strengthened overall plugging and anti-seepage structure; before pouring, pre-set a supplementary grouting pipe extending to the outside of the mine well mouth at the highest position of the top of the grouting section of the well wall;

[0010] E. Clay filling: fill clay outside the cave wall grouting section in step D to form a clay watertight section. Before filling clay, grooves are cut into the cave wall at intervals. Clay filling is carried out by artificial layered filling and compaction. After the clay watertight section is completed, bricks are laid to form a clay closed wall;

[0011] F. Concrete wellhead plugging: after closing the mold on the outside of the clay sealing wall of the clay water-proof section, pour concrete to form a concrete plugging section. Before pouring, a supplementary grouting pipe is pre-buried at the highest position of the top of the concrete plugging section and extends to the outside of the mine wellhead;

[0012] G. When the strength of the concrete poured in the concrete plugging section reaches 75%, grouting material is poured into the gap between the cave wall grouting section and the top of the concrete plugging section in the cave through the preset supplementary grouting pipe outside the well to fill and seal the gap at the top of the cave formed by the gravity sinking of the poured concrete;

[0013] H. Spraying concrete outside the sealing section in the well: After the completion of step G, fine stone concrete is sprayed on the surface of the slag backfill area from the end of the concrete sealing section in step F to the mine mouth section to block the seepage of pollutants and prevent surface water from seeping down from the cracks in the cave top from mixing with the slag to form polluted wastewater.

[0014] Furthermore, in step B, the water pipe is provided with an emergency gate valve, a pressure gauge and a water quality detector at the water outlet end outside the mine mouth. After the mine is sealed, the water quality and water level changes in the mine after the blockage can be monitored in real time through the pressure gauge and water quality detector provided on the water pipe outside the wellhead; when it is monitored that the water level in the cave rises abnormally to a high water level that may cause environmental pollution or secondary geological disasters to the surrounding area, the emergency gate valve is opened to drain water and control the water level rise, thereby buying precious time for taking emergency measures.

[0015] Further, in step C, the grouting amount of the rigid grouting pipe is determined according to the following calculation formula:

[0016] Grouting volume of a single rigid grouting pipe: Q ≥πR 2 L nαβ

[0017] Where Q is the grouting volume of a single rigid grouting pipe (m 3 ), R is the diffusion radius (m), L is the grouting length of the rigid grouting pipe = the design length of the rigid grouting pipe-1 (m), n is the formation porosity, α is the formation filling coefficient, and β is the slurry consumption coefficient;

[0018] The tunnel wall grouting section is set according to the fracture area of ​​geotechnical engineering survey. The tunnel wall grouting section can realize the full penetration, diffusion, filling and compaction of the grouting liquid in the rock fractures, cement the rock fractures and the original loose soil particles into a whole, completely seal the fractures and block the water seepage in the fractures.

[0019] Furthermore, in step C, the grouting pressure of the rigid grouting pipe is not less than 0.6 MPa, so that the grouting liquid can fully penetrate, diffuse, fill and compact in the rock formation to form a radial barrier fan.

[0020] Furthermore, in step C, the rigid grouting pipes are evenly arranged and tilted toward the inside and outside of the mine tunnel. The rigid grouting pipes away from the wellhead area tilt toward the inside of the tunnel, and the tunnel wall grouting formed by the rigid grouting pipes forms a conical blocking fan for the gushing water. The rigid grouting pipes near the wellhead area tilt toward the outside of the tunnel, and at the same time form a strong shear support; together with the concrete poured in the tunnel wall grouting section, a higher overall structural strength is formed to achieve the best water-blocking and anti-seepage effect.

[0021] Furthermore, in step E, the length of the clay water-blocking section is determined by the following calculation formula:

[0022] L1≥P*K S *K / (A*γ*Q)

[0023] Where, L1: length of clay water barrier section (m), P: water pressure near the wellhead (Kpa), A: cross-sectional area of ​​the wellhead (m 2 ), K S : Clay permeability coefficient (cm / s), γ: Clay density (t / m 3 ), Q: water inflow from wellhead (m 3 / d), K: safety factor.

[0024] Furthermore, in the step E, before clay filling, the clay needs to be fully mixed after adding water, and the clay is filled manually in layers. During filling, the clay is compacted, and the compaction coefficient is not less than 0.85, so as to achieve a good water-blocking and anti-seepage effect.

[0025] Furthermore, in step F, the length of the concrete plugging section is determined according to the following calculation formula:

[0026] L ≥ P*A*K / (C*frb)

[0027] In the formula, L is the length of the concrete plugging section (m), P is the water pressure near the wellhead (Kpa), A is the cross-sectional area of ​​the wellhead (m 2 ), K: safety factor, C: circumference of the water well section (m), Frb: characteristic value of the bond strength between the cave wall and concrete (Kpa).

[0028] Furthermore, in step D and step G, the supplementary grouting pipe consists of a slurry pipe and an exhaust pipe. The slurry pipe is used to grout the slurry, and the exhaust pipe is used to discharge the air in the void in the cave top during grouting to avoid the formation of casting hollows. The grouting slurry uses expansive cement with a water-cement ratio of 1:1.

[0029] Furthermore, in step B, the water-facing surface of the inner side of the retaining wall is plastered with anti-seepage cement mortar with a thickness of 10 mm to further enhance the anti-seepage effect.

[0030] Furthermore, in step B, the water pipe is a stainless steel seamless pipe, which has good corrosion resistance and can ensure a long service life of the water pipe; the water pipe preset at the bottom of the retaining wall in step B is 150mm higher than the bottom line of the horizontal tunnel, and the diameter of the water pipe is greater than 60mm, which can prevent silt from clogging the water pipe and realize timely discharge of gushing water during the sealing construction process.

[0031] Furthermore, the concrete poured in the cave wall grouting section in step D is anti-seepage and anti-corrosion micro-expansion concrete, which enhances the anti-seepage effect; the concrete poured in the concrete plugging section in step F is ordinary concrete, which ensures the structural strength of the concrete plugging section.

[0032] The beneficial effects of the present invention are as follows: the method of the present invention is innovative on the basis of existing concrete plugging, and adopts pressure grouting to form a radial barrier fan for the water gushing in the cave, so as to achieve the best water-blocking and anti-seepage effect, and pour concrete in the grouting section of the cave wall in the well; after the grouting section of the cave wall is solidified, the cave wall is reinforced and supported to form an overall anti-seepage effect and strengthen the overall plugging structural strength of the grouting section of the cave wall.

[0033] At the same time, a supplementary grouting pipe is provided on the top of the tunnel wall. Grouting is poured into the top gap between the grouting section and the concrete sealing section of the tunnel wall through the preset supplementary grouting pipe outside the well to fill and seal the gap on the top of the tunnel formed by the gravity sinking of the poured concrete.

[0034] Fine stone concrete is sprayed on the outer wall of the sealed wellhead and the ground surface through external concrete spraying to prevent surface water and mine water from mixing and causing pollution.

[0035] After plugging is completed, the water pressure of the well after plugging is monitored through the pressure gauge on the water pipe outside the wellhead. The water gushing condition in the well can be monitored long-term outside the wellhead, and the water quality change in the well after plugging can be monitored in real time through the water quality detector on the water pipe outside the wellhead.

[0036] The technical solution of the present invention is safe, reliable, efficient and fast, complies with relevant national technical specifications, greatly improves the airtightness and firmness of the sealing of mine water gushing, has high safety and reliability, and greatly eliminates the environmental pollution risk of abandoned mine water gushing. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of an implementation of the present invention;

[0038] Figure 2 It is a schematic diagram of the structure of the present invention;

[0039] Figure 3 yes Figure 2 BB surface cross-sectional view;

[0040] Figure 4 yes Figure 2 CC section view;

[0041] Figure 5 yes Figure 2 DD section view;

[0042] Figure 6 yes Figure 2 EE cross-sectional view;

[0043] Figure 7 yes Figure 2 FF cross-sectional view;

[0044] Figure 8 yes Figure 2 GG section view;

[0045] Fig. 9 yes Figure 2 HH plane cross-sectional view;

[0046] Fig.10 is a schematic diagram of Embodiment 2 of the present invention;

[0047] Fig.11 It is a schematic diagram of Example 3 of the present invention.

[0048] Parts and numbers in the picture:

[0049] 1-water retaining wall; 2-cavity wall grouting section; 3-clay water-proof section; 4-concrete sealing section; 11-water guide pipe; 111-emergency gate valve; 112-pressure gauge; 113-water quality detector; 21-rigid grouting pipe; 22-supplementary grouting pipe; 31-interval groove; 32-clay sealing wall. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but is not intended to limit the present invention. Any technical solution based on the transformation or inference of the present invention belongs to the protection scope of the present invention.

[0051] Example 1

[0052] like Figures 1 to 9As shown, the 2# mine blockage of Guankou Coal Mine in Guangyuan, Sichuan, is constructed using the barrier method of the present invention, and the construction method of pressure grouting of the mine body, anti-corrosion and anti-seepage barrier layer, anti-seepage concrete segment support, clay wall water stop, concrete wellhead blocking backfilling, and supplementary grouting on the top of the cave is used to block the water pollution of the abandoned mine. The barrier method specifically includes the following steps:

[0053] A. Desilting in the tunnel: remove the silt, residue and loose surrounding rock on the ground in the abandoned mine until the fresh bedrock surface of the original stratum of the adit is reached. After cleaning, use a high-pressure water gun to clean the rock wall in the tunnel;

[0054] B. Anti-corrosion and anti-seepage barrier layer: A brick wall is built in the mine to form a water retaining wall 1. A water guide pipe 11 is preset at the bottom of the water retaining wall 1 and extends to the outside of the wellhead. The water guide pipe 11 is used to guide the water gushing out of the well during the plugging construction process;

[0055] C. Grouting and solidification of the cave body for anti-seepage: After the rigid grouting pipe 21 is driven into the top wall and side wall of the mine outside the retaining wall 1, pressure grouting is performed. The grouting liquid penetrates, diffuses, fills and compacts in the rock formation, penetrates and drives away the moisture and air in the loose particles between the cracks of the rock formation, and then fills the gaps. After the grouting liquid solidifies, the loose soil particles between the cracks are cemented into a whole, forming the cave wall grouting section 2 in the well;

[0056] The grouting amount of the rigid grouting pipe 21 is determined by the following calculation formula:

[0057] Grouting volume of a single rigid grouting pipe 21: Q ≥πR 2 Lnαβ

[0058] Where Q is the grouting volume of a single rigid grouting pipe 21 (m 3 ), R is the diffusion radius (m), L is the grouting length of the rigid grouting pipe 21 = the design length of the rigid grouting pipe 21-1 (m), n is the formation porosity, α is the formation filling coefficient, and β is the slurry consumption coefficient;

[0059] The design length of the rigid grouting pipe 21 of the No. 2 shaft of Guankou Coal Mine is 4m, the diffusion radius R is 0.3m, the porosity n of the cave wall stratum is 0.4, the stratum filling coefficient α is 0.8, and the slurry consumption coefficient β is 1.1. Substituting the above formula into the calculation, the grouting volume of a single rigid grouting pipe 21 of the cave wall grouting section 2 of the No. 2 shaft of Guankou Coal Mine is not less than 0.298 m 3 .

[0060] The cave wall grouting section 2 is set according to the fissure area of ​​the mine investigated by geotechnical engineering, and the grouting pressure of the rigid grouting pipe 21 is not less than 0.6Mpa, so as to achieve full penetration, diffusion, filling and compaction of the grouting liquid in the fissure area of ​​the rock formation, and cement the rock gap and the originally loose soil particles into a whole.

[0061] D. Anti-corrosion and anti-seepage concrete plugging: pour anti-corrosion and anti-seepage concrete in the grouting section 2 of the well wall in step C; reinforce and support the wall of the well wall after the grouting section 2 is solidified to form a strengthened overall plugging and anti-seepage structure; before pouring, pre-set a supplementary grouting pipe 22 extending to the outside of the mine well mouth at the highest position of the top of the grouting section 2;

[0062] E. Clay filling: Clay is filled outside the cave wall grouting section 2 in step D to form a clay watertight section 3. Before filling the clay, the cave wall is grooved 31 at intervals. The clay filling is carried out by artificial layered filling and compaction. After the clay watertight section 3 is completed, bricks are laid to form a clay closed wall 32;

[0063] The length of the clay water-blocking section 3 is determined by the following calculation formula:

[0064] L1≥P*K S *K / (A*γ*Q)

[0065] Where, L1: length of clay water barrier 3 (m), P: water pressure near the wellhead (Kpa), A: cross-sectional area of ​​the wellhead (m 2 ), K S : Clay permeability coefficient (cm / s), γ: Clay density (t / m 3 ), Q: water inflow from wellhead (m 3 / d), K: safety factor;

[0066] The water pressure P near the No. 2 wellhead of Guankou Coal Mine is 4700 Kpa, and the cross-sectional area of ​​the wellhead is 7.8 m 2 , clay permeability coefficient K s 5×10 -5 cm / s, clay density γ is 1.7 t / m 3 The water inflow from the wellhead is Q, which is 100 m 3 / d, the safety factor K is 2, and the length L1 of the clay waterproof section 3 at the 2# wellhead of Guankou Coal Mine is not less than 3.06 m.

[0067] In the step E, before clay filling, the clay needs to be fully mixed after adding water, and the clay is filled manually in layers. During filling, the clay is compacted, and the compaction coefficient is not less than 0.85.

[0068] F. Concrete wellhead plugging: after closing the mold on the outside of the clay sealing wall 32 of the clay water-proof section 3, concrete is poured to form a concrete plugging section 4. A supplementary grouting pipe 22 is pre-buried at the highest position of the top of the concrete plugging section 4 and extends to the outside of the mine wellhead;

[0069] The length of the concrete plugging section 4 should meet the following requirements:

[0070] L ≥ P*A*K / (C*frb)

[0071] Where, L: length of the concrete plugging section 4 at the wellhead (m), P: water pressure near the wellhead (Kpa), A: cross-sectional area of ​​the wellhead (m 2 ), K: safety factor, C: circumference of the water well section (m), Frb: characteristic value of the bond strength between the cave wall and concrete (Kpa).

[0072] The water pressure P near the No. 2 wellhead of Guankou Coal Mine is 4700 Kpa, and the cross-sectional area of ​​the wellhead is 7.8 m 2 , the safety factor K is 2, the circumference of the water well mouth C is 9 m, the characteristic value of the bonding strength between the cave wall and concrete Frb is 300 Kpa. It is calculated from the above formula that the length L of the concrete sealing section 4 of the 2# well mouth of Guankou Coal Mine is not less than 27.156 m.

[0073] G. When the strength of the concrete poured in the concrete plugging section 4 reaches 75%, grouting is performed outside the well through the preset supplementary grouting pipe 22 into the gap between the cave wall grouting section 2 and the top of the concrete plugging section 4 in the cave to fill and seal the gap at the top of the cave formed by the gravity sinking of the poured concrete;

[0074] H. Spraying concrete outside the sealing section in the well: After the completion of step G, fine stone concrete is sprayed on the surface of the slag backfill area from the end of the concrete sealing section 4 in step F to the mine mouth section to block the seepage of pollutants and prevent surface water from seeping down from the cracks in the cave top from mixing with the slag to form polluted wastewater.

[0075] In step B, the water pipe 11 is provided with an emergency gate valve 111, a pressure gauge 112 and a water quality detector 113 at the water outlet end outside the mine mouth. After the mine is sealed, the pressure gauge 112 and the water quality detector 113 provided on the water pipe 11 outside the well mouth can be used to monitor the water quality and water level changes in the mine after the sealing in real time; when it is monitored that the water level in the cave rises abnormally to a high water level that may cause environmental pollution or secondary geological disasters to the surrounding area, the emergency gate valve 111 is opened to drain water and control the water level rise, thereby buying precious time for taking emergency measures.

[0076] In step C, the grouting pressure of the rigid grouting pipe 21 is not less than 0.6Mpa. The length of the cave wall grouting section 2 is set according to the fissure area of ​​the mine investigated by geotechnical engineering. The cave wall grouting section 2 can achieve full penetration, diffusion, filling and compaction of the grouting liquid in the rock stratum fissures, cement the rock gaps and the originally loose soil particles into a whole, completely seal the fissures, and block water seepage in the fissures.

[0077] The supplementary grouting pipe 22 consists of a slurry pipe and an exhaust pipe. The slurry pipe is used to grout the slurry, and the exhaust pipe is used to discharge the air in the void in the cave top during grouting to avoid the formation of casting hollows. The grouting slurry uses expansive cement with a water-cement ratio of 1:1.

[0078] In the step B, the water-facing surface of the inner side of the retaining wall 1 is plastered with anti-seepage cement mortar with a thickness of 10 mm to further enhance the anti-seepage effect.

[0079] In step B, the water pipe 11 is a stainless steel seamless pipe, which has good corrosion resistance and can ensure the long service life of the water pipe 11. The water pipe 11 preset through the bottom of the water retaining wall 1 is 150 mm higher than the bottom line of the adit, and the diameter of the water pipe 11 is greater than 60 mm, which can prevent silt from blocking the water pipe and realize timely discharge of gushing water during the plugging construction process.

[0080] The concrete poured in the cave wall grouting section 2 in step D is anti-seepage and anti-corrosion micro-expansion concrete, which enhances the anti-seepage effect. The concrete poured in the concrete plugging section 4 in step F is ordinary concrete, which ensures the structural strength of the concrete plugging section 4.

[0081] Example 2

[0082] like Fig.10 As shown, the 4# well of Guankou Coal Mine in Guangyuan, Sichuan is blocked by the blocking method of the present invention, and the construction method of pressure grouting of the mine body, anti-corrosion and anti-seepage barrier layer, anti-seepage concrete segment support, clay wall water stop, concrete wellhead blocking backfill, and supplementary grouting at the top of the cave is used to block the water pollution of the abandoned mine. The blocking method specifically includes the following steps:

[0083] A. Desilting in the tunnel: remove the silt, residue and loose surrounding rock on the ground in the abandoned mine until the fresh bedrock surface of the original stratum of the adit is reached. After cleaning, use a high-pressure water gun to clean the rock wall in the tunnel;

[0084] B. Anti-corrosion and anti-seepage barrier layer: A brick wall is built in the mine to form a water retaining wall 1. A water guide pipe 11 is preset at the bottom of the water retaining wall 1 and extends to the outside of the wellhead. The water guide pipe 11 is used to guide the water gushing out of the well during the plugging construction process;

[0085] C. Grouting and solidification of the cave body for anti-seepage: After the rigid grouting pipe 21 is driven into the top wall and side wall of the mine outside the retaining wall 1, pressure grouting is performed. The grouting liquid penetrates, diffuses, fills and compacts in the rock formation, penetrates and drives away the moisture and air in the loose particles between the cracks of the rock formation, and then fills the gaps. After the grouting liquid solidifies, the loose soil particles between the cracks are cemented into a whole, forming the cave wall grouting section 2 in the well;

[0086] The grouting amount of the rigid grouting pipe 21 is determined by the following calculation formula:

[0087] Grouting volume of a single rigid grouting pipe 21: Q ≥πR 2 Lnαβ

[0088] Where Q is the grouting volume of a single rigid grouting pipe 21 (m 3 ), R is the diffusion radius (m), L is the grouting length of the rigid grouting pipe 21 = the design length of the rigid grouting pipe 21-1 (m), n is the formation porosity, α is the formation filling coefficient, and β is the slurry consumption coefficient;

[0089] The design length of the rigid grouting pipe 21 of the 4# mine shaft of Guankou Coal Mine is 4m, the diffusion radius R is 0.3m, the porosity n of the cave wall stratum is 0.4, the stratum filling coefficient α is 0.8, and the slurry consumption coefficient β is 1.1. Substituting the above formula into the calculation, the grouting volume of a single rigid grouting pipe 21 of the cave wall grouting section 2 of the 4# mine shaft of Guankou Coal Mine is not less than 0.298 m 3 .

[0090] The length of the cave wall grouting section 2 is set according to the fissure area of ​​geotechnical engineering survey, and the grouting pressure of the rigid grouting pipe 21 is not less than 0.6Mpa, so that the grouting liquid can fully penetrate, diffuse, fill and compact in the fissure area of ​​the rock formation, and cement the originally loose soil particles into a whole.

[0091] D. Anti-corrosion and anti-seepage concrete plugging: pour anti-corrosion and anti-seepage concrete in the grouting section 2 of the well wall in step C; reinforce and support the wall of the well wall after the grouting section 2 is solidified to form a strengthened overall plugging and anti-seepage structure; before pouring, pre-set a supplementary grouting pipe 22 extending to the outside of the mine well mouth at the highest position of the top of the grouting section 2;

[0092] E. Clay filling: Clay is filled outside the cave wall grouting section 2 in step D to form a clay watertight section 3. Before filling the clay, the cave wall is grooved 31 at intervals. The clay filling is carried out by artificial layered filling and compaction. After the clay watertight section 3 is completed, bricks are laid to form a clay closed wall 32;

[0093] The length of the clay water-blocking section 3 is determined by the following calculation formula:

[0094] L1≥P*K S *K / (A*γ*Q)

[0095] Where, L1: length of clay water barrier 3 (m), P: water pressure near the wellhead (Kpa), A: cross-sectional area of ​​the wellhead (m 2 ), K S : Clay permeability coefficient (cm / s), γ: Clay density (t / m 3 ), Q: water inflow from wellhead (m 3 / d), K: safety factor;

[0096] The water pressure P near the No. 4 wellhead of Guankou Coal Mine is 6000 Kpa, and the cross-sectional area A of the wellhead is 7.8 m 2 , clay permeability coefficient K s 5×10 -5 cm / s, clay density γ is 1.7 t / m 3 The water inflow from the wellhead is Q, which is 500 m 3 / d, the safety factor K is 2, and the length L1 of the clay watertight section 3 at the 4# wellhead of Guankou Coal Mine is calculated to be no less than 7.82 m.

[0097] In the step E, before clay filling, the clay needs to be fully mixed after adding water, and the clay is filled manually in layers. During filling, the clay is compacted, and the compaction coefficient is not less than 0.85.

[0098] F. Concrete wellhead plugging: after closing the mold on the outside of the clay sealing wall 32 of the clay water-proof section 3, concrete is poured to form a concrete plugging section 4. A supplementary grouting pipe 22 is pre-buried at the highest position of the top of the concrete plugging section 4 and extends to the outside of the mine wellhead;

[0099] The length of the concrete plugging section 4 should meet the following requirements:

[0100] L ≥ P*A*K / (C*frb)

[0101] Where, L: length of the concrete plugging section 4 at the wellhead (m), P: water pressure near the wellhead (Kpa), A: cross-sectional area of ​​the wellhead (m 2 ), K: safety factor, C: circumference of the water well section (m), Frb: characteristic value of the bond strength between the cave wall and concrete (Kpa).

[0102] The water pressure P near the No. 4 wellhead of Guankou Coal Mine is 6000Kpa, and the cross-sectional area A of the wellhead is 7.8 m 2 , the safety factor K is 2, the circumference of the water well mouth C is 9 m, the characteristic value of the bonding strength between the cave wall and concrete Frb is 300 Kpa. It is calculated from the above formula that the length L of the concrete sealing section 4 of the 4# well mouth of Guankou Coal Mine is not less than 34.667 m.

[0103] G. When the strength of the concrete poured in the concrete plugging section 4 reaches 75%, grouting is performed outside the well through the preset supplementary grouting pipe 22 into the gap between the cave wall grouting section 2 and the top of the concrete plugging section 4 in the cave to fill and seal the gap at the top of the cave formed by the gravity sinking of the poured concrete;

[0104] H. Spraying concrete outside the sealing section in the well: After the completion of step G, fine stone concrete is sprayed on the surface of the slag backfill area from the end of the concrete sealing section 4 in step F to the mine mouth section to block the seepage of pollutants and prevent surface water from seeping down from the cracks in the cave top from mixing with the slag to form polluted wastewater.

[0105] In step B, the water pipe 11 is provided with an emergency gate valve 111, a pressure gauge 112 and a water quality detector 113 at the water outlet end outside the mine mouth. After the mine is sealed, the pressure gauge 112 and the water quality detector 113 provided on the water pipe 11 outside the well mouth can be used to monitor the water quality and water level changes in the mine after the sealing in real time; when it is monitored that the water level in the cave rises abnormally to a high water level that may cause environmental pollution or secondary geological disasters to the surrounding area, the emergency gate valve 111 is opened to drain water and control the water level rise, thereby buying precious time for taking emergency measures.

[0106] In step B, the water pipe 11 is a stainless steel seamless pipe, which has good corrosion resistance and can ensure the long service life of the water pipe 11. The water pipe 11 preset through the bottom of the water retaining wall 1 is 150 mm higher than the bottom line of the adit, and the diameter of the water pipe 11 is greater than 60 mm, which can prevent silt from blocking the water pipe 11 and realize timely discharge of gushing water during the plugging construction process.

[0107] The concrete poured in the cave wall grouting section 2 in step D is anti-seepage and anti-corrosion micro-expansion concrete, which enhances the anti-seepage effect. The concrete poured in the concrete plugging section 4 in step F is ordinary concrete, which ensures the structural strength of the concrete plugging section 4.

[0108] like Fig.10 As shown, in step C, the rigid grouting pipes 21 are evenly arranged and tilted toward the inside and outside of the mine cave. The rigid grouting pipes 21 away from the wellhead area tilt toward the inside of the cave, and the cave wall grouting formed by the rigid grouting pipes 21 forms a conical blocking fan for the gushing water. The rigid grouting pipes 21 near the wellhead area tilt toward the outside of the cave to form a strong shear support; together with the concrete poured in the cave wall grouting section 2, a higher overall structural strength is formed to achieve the best water-blocking and anti-seepage effect.

[0109] Example 3

[0110] like Fig.11 As shown, the main wellhead of Wumutuo Coal Mine in Guangyuan, Sichuan is blocked by the blocking method of the present invention, and the construction method of pressure grouting of the mine body, anti-corrosion and anti-seepage barrier layer, anti-seepage concrete segment support, clay wall water stop, concrete wellhead blocking backfill, and supplementary grouting on the top of the cave is used to block the water pollution of the abandoned mine. The blocking method specifically includes the following steps:

[0111] A. Desilting in the tunnel: remove the silt, residue and loose surrounding rock on the ground in the abandoned mine until the fresh bedrock surface of the original stratum of the adit is reached. After cleaning, use a high-pressure water gun to clean the rock wall in the tunnel;

[0112] B. Anti-corrosion and anti-seepage barrier layer: A brick wall is built in the mine to form a water retaining wall 1. A water guide pipe 11 is preset at the bottom of the water retaining wall 1 and extends to the outside of the wellhead. The water guide pipe 11 is used to guide the water gushing out of the well during the plugging construction process;

[0113] C. Grouting and solidification of the cave body for anti-seepage: After the rigid grouting pipe 21 is driven into the top wall and side wall of the mine outside the retaining wall 1, pressure grouting is performed. The grouting liquid penetrates, diffuses, fills and compacts in the rock formation, penetrates and drives away the moisture and air in the loose particles between the cracks of the rock formation, and then fills the gaps. After the grouting liquid solidifies, the loose soil particles between the cracks are cemented into a whole, forming the cave wall grouting section 2 in the well;

[0114] The grouting amount of the rigid grouting pipe 21 is determined by the following calculation formula:

[0115] Grouting volume of a single rigid grouting pipe 21: Q ≥πR 2 Lnαβ

[0116] Where Q is the grouting volume of a single rigid grouting pipe 21 (m 3 ), R is the diffusion radius (m), L is the grouting length of the rigid grouting pipe 21 = the design length of the rigid grouting pipe 21-1 (m), n is the formation porosity, α is the formation filling coefficient, and β is the slurry consumption coefficient;

[0117] The design length of the rigid grouting pipe 21 of the main well of Wumutuo Coal Mine is 3m, the diffusion radius R is 0.3m, the porosity n of the cave wall stratum is 0.3, the stratum filling coefficient α is 0.8, and the slurry consumption coefficient β is 1.1. The above formula calculates that the grouting volume of a single rigid grouting pipe 21 of the cave wall grouting section 2 of the main well of Wumutuo Coal Mine is not less than 0.149 m 3 .

[0118] The cave wall grouting section 2 is set according to the fissure area of ​​geotechnical engineering survey, and the grouting pressure of the rigid grouting pipe 21 is not less than 0.6Mpa, so as to achieve full penetration, diffusion, filling and compaction of the grouting liquid in the rock fissure area, and cement the rock gap and the original loose soil particles into a whole.

[0119] D. Anti-corrosion and anti-seepage concrete plugging: pour anti-corrosion and anti-seepage concrete in the grouting section 2 of the well wall in step C; reinforce and support the wall of the well wall after the grouting section 2 is solidified to form a strengthened overall plugging and anti-seepage structure; before pouring, pre-set a supplementary grouting pipe 22 extending to the outside of the mine well mouth at the highest position of the top of the grouting section 2;

[0120] E. Clay filling: Clay is filled outside the cave wall grouting section 2 in step D to form a clay watertight section 3. Before filling the clay, the cave wall is grooved 31 at intervals. The clay filling is carried out by artificial layered filling and compaction. After the clay watertight section 3 is completed, bricks are laid to form a clay closed wall 32;

[0121] The length of the clay water-blocking section 3 is determined by the following calculation formula:

[0122] L1≥P*K S *K / (A*γ*Q)

[0123] In the formula, L1: length of clay water barrier 3 (m), P: water pressure near the wellhead (Kpa), A: cross-sectional area of ​​the wellhead (m 2 ), K S : Clay permeability coefficient (cm / s), γ: Clay density (t / m 3 ), Q: water inflow from wellhead (m 3 / d), K: safety factor;

[0124] The water pressure P near the main wellhead of Wumutuo Coal Mine is 1800 Kpa, and the cross-sectional area A of the wellhead is 8.2 m 2 , clay permeability coefficient K s 5×10 -5 cm / s, clay density γ is 1.7 t / m 3 The water inflow at the wellhead is Q, which is 50 m 3 / d, the safety factor K is 2. It is calculated from the above formula that the length L1 of the clay watertight section 3 of the main wellhead of Wumutuo Coal Mine is not less than 2.23m.

[0125] In the step E, before clay filling, the clay needs to be fully mixed after adding water, and the clay is filled manually in layers. During filling, the clay is compacted, and the compaction coefficient is not less than 0.85.

[0126] F. Concrete wellhead plugging: after closing the mold on the outside of the clay sealing wall 32 of the clay water-proof section 3, concrete is poured to form a concrete plugging section 4. A supplementary grouting pipe 22 is pre-buried at the highest position of the top of the concrete plugging section 4 and extends to the outside of the mine wellhead;

[0127] The length of the concrete plugging section 4 should meet the following requirements:

[0128] L ≥ P*A*K / (C*frb)

[0129] Where, L: length of the concrete plugging section 4 at the wellhead (m), P: water pressure near the wellhead (Kpa), A: cross-sectional area of ​​the wellhead (m 2), K: safety factor, C: circumference of the water well section (m), Frb: characteristic value of the bond strength between the cave wall and concrete (Kpa).

[0130] The water pressure P near the main wellhead of Wumutuo Coal Mine is 1800Kpa, and the cross-sectional area A of the wellhead is 8.2 m 2 , the safety factor K is 2, the circumference of the water well mouth C is 9.4m, the characteristic value of the bonding strength between the cave wall and concrete Frb is 320 Kpa. It is calculated from the above formula that the length L of the concrete sealing section 4 of the main well mouth of Wumutuo Coal Mine is not less than 9.714m.

[0131] G. When the strength of the concrete poured in the concrete plugging section 4 reaches 75%, grouting is performed outside the well through the preset supplementary grouting pipe 22 into the gap between the cave wall grouting section 2 and the top of the concrete plugging section 4 in the cave to fill and seal the gap at the top of the cave formed by the gravity sinking of the poured concrete;

[0132] H. Spraying concrete outside the sealing section in the well: After the completion of step G, fine stone concrete is sprayed on the surface of the slag backfill area from the end of the concrete sealing section 4 in step F to the mine mouth section to block the seepage of pollutants and prevent surface water from seeping down from the cracks in the cave top from mixing with the slag to form polluted wastewater.

[0133] In step B, the water pipe 11 is provided with an emergency gate valve 111, a pressure gauge 112 and a water quality detector 113 at the water outlet end outside the mine mouth. After the mine is sealed, the pressure gauge 112 and the water quality detector 113 provided on the water pipe 11 outside the well mouth can be used to monitor the water quality and water level changes in the mine after the sealing in real time; when it is monitored that the water level in the cave rises abnormally to a high water level that may cause environmental pollution or secondary geological disasters to the surrounding area, the emergency gate valve 111 is opened to drain water and control the water level rise, thereby buying precious time for taking emergency measures.

[0134] In step C, the grouting pressure of the rigid grouting pipe 21 is not less than 0.6 MPa, so that the grouting liquid can fully penetrate, diffuse, fill and compact in the rock formation, and the originally loose soil particles can be cemented into a whole.

[0135] In step D and step G, the supplementary grouting pipe 22 consists of a slurry pipe and an exhaust pipe. The slurry pipe is used to grout the slurry, and the exhaust pipe is used to discharge the air in the void in the cave top during grouting to avoid the formation of casting hollows. The grouting slurry uses expansive cement with a water-cement ratio of 1:1.

[0136] In the step B, the water-facing surface of the inner side of the retaining wall 1 is plastered with anti-seepage cement mortar with a thickness of 10 mm to further enhance the anti-seepage effect.

[0137] In step B, the water pipe 11 is a stainless steel seamless pipe, which has good corrosion resistance and can ensure the long service life of the water pipe 11. The water pipe 11 preset through the bottom of the water retaining wall 1 is 150 mm higher than the bottom line of the adit, and the diameter of the water pipe 11 is greater than 60 mm, which can prevent silt from blocking the water pipe 11 and realize timely discharge of gushing water during the plugging construction process.

[0138] The concrete poured in the cave wall grouting section 2 in step D is anti-seepage and anti-corrosion micro-expansion concrete, which enhances the anti-seepage effect. The concrete poured in the concrete plugging section 4 in step F is ordinary concrete, which ensures the structural strength of the concrete plugging section 4.

[0139] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for isolating acidic wastewater from abandoned mines, characterized in that: The abandoned mine water pollution is blocked by the construction methods of pressure grouting of the mine body, anti-corrosion and anti-seepage barrier layer, anti-seepage concrete section support, clay wall water stop, concrete wellhead plugging and backfilling, and additional grouting at the top of the cave. The pollution blocking method specifically includes the following steps: A. Desilting in the tunnel: remove the silt, residue and loose surrounding rock on the ground in the abandoned mine until the fresh bedrock surface of the original stratum of the adit is reached. After cleaning, use a high-pressure water gun to clean the rock wall in the tunnel; B. Anti-corrosion and anti-seepage barrier layer: Brick walls are built in the mine to form a water retaining wall. A water guide pipe is preset at the bottom of the water retaining wall and extends to the outside of the wellhead. The water guide pipe is used to guide the water gushing out of the well during the plugging construction process; C. Grouting and solidification of the cave body for anti-seepage: After the rigid grouting pipe is driven into the top wall and side wall of the mine outside the retaining wall, pressure grouting is carried out. The grouting liquid penetrates, diffuses, fills and compacts in the rock formation, penetrates and drives away the water and air in the loose particles between the cracks of the rock formation, and then fills the gaps. After the grouting liquid solidifies, the loose soil particles between the original cracks are cemented into a whole, forming the cave wall grouting section in the well; D. Anti-corrosion and anti-seepage concrete plugging: pour anti-corrosion and anti-seepage concrete in the grouting section of the well wall in step C; reinforce and support the wall of the well wall after the grouting section of the well wall is solidified to form a strengthened overall plugging and anti-seepage structure; before pouring, pre-set a supplementary grouting pipe extending to the outside of the mine well mouth at the highest position of the top of the grouting section of the well wall; E. Clay filling: fill clay outside the cave wall grouting section in step D to form a clay watertight section. Before filling clay, grooves are cut into the cave wall at intervals. Clay filling is carried out by artificial layered filling and compaction. After the clay watertight section is completed, bricks are laid to form a clay closed wall; F. Concrete wellhead plugging: after closing the mold on the outside of the clay sealing wall of the clay water-proof section, pour concrete to form a concrete plugging section. Before pouring, a supplementary grouting pipe is pre-buried at the highest position of the top of the concrete plugging section and extends to the outside of the mine wellhead; G. When the strength of the concrete poured in the concrete plugging section reaches 75%, grout is poured into the gap between the cave wall grouting section and the top of the concrete plugging section in the mine cave through the preset supplementary grouting pipe outside the mine cave to fill and seal the gap in the top of the mine cave formed by the gravity sinking of the poured concrete; H. Spraying concrete outside the sealing section in the well: After completing step G, fine stone concrete is sprayed on the surface of the slag backfill area from the end of the concrete sealing section in step F to the mine mouth section to prevent the seepage of pollutants.

2. The method for isolating acidic wastewater from abandoned mines according to claim 1, characterized in that: In step B, the water outlet end of the water pipe outside the mine entrance is provided with an emergency gate valve, a pressure gauge and a water quality detector.

3. The method for blocking pollution of acidic wastewater from abandoned mines according to claim 1, characterized in that: In step C, the grouting amount of the rigid grouting pipe is determined according to the following calculation formula: Grouting volume of a single rigid grouting pipe: Q ≥πR 2 L nαβ Where Q is the grouting volume of a single rigid grouting pipe (m 3 ), R is the diffusion radius (m), L is the grouting length of the rigid grouting pipe = the design length of the rigid grouting pipe-1 (m), n is the formation porosity, α is the formation filling coefficient, and β is the slurry consumption coefficient.

4. The method for blocking pollution of acidic wastewater from abandoned mines according to claim 1, characterized in that: In step C, the grouting pressure of the rigid grouting pipe is not less than 0.6 MPa.

5. A method for blocking pollution of acidic wastewater from abandoned mines according to any one of claims 1 to 4, characterized in that: In step C, the rigid grouting pipes are evenly arranged and inclined in two directions, namely, inside and outside the mine hole.

6. The method for blocking pollution of acidic wastewater from abandoned mines according to claim 1, characterized in that: In the step E, before clay filling, the clay needs to be fully mixed after adding water, and the clay is filled manually in layers. During filling, the clay is compacted, and the compaction coefficient is not less than 0.

85.

7. The method for blocking pollution of acidic wastewater from abandoned mines according to claim 1, characterized in that: In step D and step G, the supplementary grouting pipe consists of a slurry pipe and an exhaust pipe. The slurry pipe is used for grouting slurry, and the exhaust pipe is used to discharge the air in the void at the top of the cave during grouting. The grouting slurry uses expansive cement with a water-cement ratio of 1:

1.

8. The method for blocking pollution of acidic wastewater from abandoned mines according to claim 1, characterized in that: In step B, the water-facing surface of the inner side of the retaining wall is plastered with anti-seepage cement mortar with a thickness of 10 mm.

9. The method for blocking pollution of acidic wastewater from abandoned mines according to claim 1, characterized in that: In step B, the water pipe is a stainless steel seamless pipe; the water pipe preset at the bottom of the retaining wall is 150 mm higher than the bottom line of the horizontal tunnel, and the diameter of the water pipe is greater than 60 mm.

10. The method for blocking pollution of acidic wastewater from abandoned mines according to claim 1, characterized in that: The concrete poured in the cave wall grouting section in step D is anti-seepage and anti-corrosion micro-expansion concrete, and the concrete poured in the concrete plugging section in step F is ordinary concrete.

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