Water retention and disaster reduction method for calcification induced diagenesis of quaternary unconsolidated formation

Abstract

The invention belongs to the field of coal mine water retention and disaster reduction control, and particularly relates to a water retention and disaster reduction method for quaternary unconsolidated formation calcification induced diagenesis. According to the influence range of underground coal mining on the quaternary unconsolidated formation, calcified aqueous solution recharge drill holes generated by inducing calcium carbonate precipitation and effect observation drill holes are reasonably arranged; the method comprises the following steps: preparing a reagent aqueous solution with proper concentration according to ion components and content of a quaternary loose bed occurrence water body; calcium carbonate precipitates generated by chemical reaction of underground water and a calcified aqueous solution form a reinforcing effect on loose sand / soil particles, and sand / soil diagenesis in a corresponding area is promoted, so that a whole with certain bearing capacity is finally formed, a large amount of load of a loose bed is prevented from being transmitted, and a key bed is prevented from being subjected to composite fracture; the purposes of underground water protection and geological disaster prevention and control are achieved. The method can provide guarantee for water-preserved coal mining and strong mine pressure control of a thick unconsolidated formation thin bedrock mining area, and is simple in implementation method, safe, environment-friendly and high in reliability.

Description

Technical Field

[0001] The present invention relates to a method for groundwater protection and prevention and control of mining geological disasters, and in particular to a method for water conservation and disaster reduction of Quaternary loose layer calcification induced diagenesis, which is suitable for use in the field of prevention and control of mining geological disasters such as overall stratum cutting, groundwater leakage, and strong underground mine pressure caused by underground coal mining. Background Art

[0002] Coal mining often causes large-scale collapse and cracking of the overlying rock strata, leading to groundwater loss, significant surface subsidence and other mining damage phenomena. Especially under the conditions where the loose sand / soil layer of the Quaternary system is thick and the thickness of the bedrock overlying the coal seam is thin, due to the load transfer effect of the loose layer, it is very easy to cause composite fracture of the key layer of the overlying rock, directly causing the overlying strata to be cut off as a whole, resulting in the destruction of aquifers, groundwater leakage, surface step collapse, underground pressure frame roof fall and other mining geological disasters. Therefore, scientifically reducing the load transfer degree of the Quaternary loose layer is crucial to effectively prevent and control the occurrence of the above problems. Through a large number of studies, it has been found that if relevant measures can be taken to artificially reinforce the Quaternary loose layer and induce the key load transfer area to form a whole (or local diagenesis), the bearing structure of the "diagenetic body" can be exerted to block the transmission of the overlying load; in this way, the relevant geological disaster problems can be effectively controlled.

[0003] At present, cement grouting, chemical slurry and other solidifying materials are mature technical means for loose sand / soil reinforcement, but the large-scale use of these materials has disadvantages such as environmental pollution and high cost. Many previous studies and engineering practices have found that chemical precipitation of calcium carbonate has a similar coagulation effect as the above-mentioned reinforcement slurry. It can aggregate loose sand / soil particles together through the adsorption, growth and scaling process of calcium carbonate crystals, and form a carrier with certain mechanical strength. The microbial induced calcium carbonate deposition (MICP) reinforcement technology, which is currently widely studied at home and abroad, is a typical representative of this. Considering that the Quaternary loose layer is usually hosted by a certain amount of groundwater (generally a phreatic aquifer), these groundwaters generally contain a lot of Ca 2+ 、HCO3 - If we can adopt the idea of ​​inducing CaCO3 precipitation, and artificially inject an aqueous solution of reagents that can generate calcium carbonate precipitation with groundwater, we can use its adsorption-consolidation effect to effectively promote the consolidation and diagenesis of loose sand / soil. To this end, it is necessary to carry out special design of water conservation and disaster reduction methods for calcification-induced diagenesis of loose sand / soil layers based on the migration and load transfer mechanism of the Quaternary loose layer caused by coal mining. Summary of the invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a method for water conservation and disaster reduction in calcification-induced diagenesis of the Quaternary loose layer. According to the impact range of underground coal mining on the Quaternary loose layer, the calcified aqueous solution reinjection drilling holes and effect observation drilling holes for inducing calcium carbonate precipitation are reasonably arranged; according to the ion composition and content of the water body stored in the Quaternary loose layer, a reagent aqueous solution of appropriate concentration is prepared; the calcium carbonate precipitation generated by the chemical reaction of groundwater and the calcified aqueous solution is used to reinforce the loose sand / soil particles, promote the diagenesis of the sand / soil body in the corresponding area, and finally form a whole with a certain bearing capacity, prevent the large-scale transfer of the loose layer load, and prevent the occurrence of composite fractures in the key layer, so as to achieve the purpose of groundwater protection and geological disaster prevention and control.

[0005] Technical solution: To achieve the above-mentioned purpose, the water conservation and disaster reduction method of calcification-induced diagenesis of the Quaternary loose layer of the present invention comprises the following steps: before coal seam mining, whether a composite fracture occurs in the key layer of the overburden in the mining area is calculated based on the key layer theory to determine whether a calcification solution recharge borehole is needed in the corresponding area; if a composite fracture occurs in the key layer, a calcification solution recharge borehole and an effect observation borehole are constructed on the corresponding surface within a certain range within and outside the mining area; a suitable calcification solution is prepared according to the ion composition and content of the water stored in the Quaternary loose layer and injected from the calcification solution recharge borehole; the calcium carbonate precipitate generated by the chemical reaction of the calcification solution recharged into the loose layer with the groundwater is used to consolidate and induce diagenesis of the loose sand / soil particles, so that they form a whole with a certain bearing capacity, thereby preventing a large amount of load transfer in the loose layer and preventing composite fracture in the key layer, thereby achieving the purpose of groundwater protection and geological disaster prevention and control.

[0006] The specific steps are as follows:

[0007] a. Before coal seam mining, determine the mining area where compound fracture occurs in the key overburden strata;

[0008] b. For the coal mining area where compound fracture occurs in the key overburden strata, determine the plane and vertical range of the corresponding Quaternary loose strata that need to be induced to consolidate and diagenesize;

[0009] c. Construction of drilling holes for recharging calcified aqueous solution on the surface corresponding to the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis;

[0010] d. According to the ion composition and content of the water stored in the Quaternary loose layer, a calcified aqueous solution is prepared and injected into the loose layer through the calcified aqueous solution recharge borehole;

[0011] e. During the reinjection process of the calcified aqueous solution, calcium carbonate precipitates are produced and continuously adsorbed on the surface of loose sand / soil particles, effectively condensing and consolidating the loose sand / soil particles, gradually forming a bearing entity with a certain mechanical strength, blocking the transmission of overlying loads.

[0012] Preferably, in step b, the planar range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis is the coal mining area where compound fracture of the overburden key layer occurs plus the D+h range extending outward from the boundaries of the coal mining area, wherein D is the bedrock influence range caused by mining in the coal mining area, and h is the thickness of the Quaternary loose layer.

[0013] Preferably, in step b, the vertical range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis is (0.5-0.8) h upward from the top interface of the bedrock.

[0014] Preferably, in step c, the calcified water solution reinjection borehole is a vertical borehole constructed from the ground surface, the final hole depth is h, and a casing is arranged in the calcified water solution reinjection borehole, and the casing in the range of (0.5-0.8) h above the bottom of the hole is a flower pipe.

[0015] Preferably, in step c, the calcified aqueous solution recharging boreholes are arranged in an array in strike and dip with spacing set within the plane range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis.

[0016] Preferably, in step c, the distance between the outermost calcified aqueous solution reinjection borehole and the plane boundary line of the Quaternary loose layer that needs to be induced to consolidate and diagenesis is less than 150m.

[0017] Preferably, in step c, an effect observation borehole is also constructed.

[0018] Preferably, in step c, the effect observation borehole is a vertical borehole constructed from the ground surface, and the effect observation borehole is arranged at the four corners of the plane range boundary line where the Quaternary loose layer needs to be induced to consolidate and diagenesis, and the final hole depth is h; the hole wall of the effect observation borehole is closed with casing from a depth of 0.5h below the ground surface, and other sections are protected with flower pipes.

[0019] Preferably, in step d, the injection pressure should be greater than the submerged water head pressure of the loose layer, but should not exceed the water head pressure corresponding to the thickness of the loose layer.

[0020] Preferably, in step d, if the Quaternary loose layer water is rich in Ca 2+ , then the calcified aqueous solution is made of CO3 2- The chemical reagents and deionized water are mixed into an aqueous solution, CO3 2- The concentration is based on the energy and Ca 2+ Sufficient precipitation reaction occurs to set.

[0021] Preferably, in step d, if the Quaternary loose layer water storage Ca 2+ If the concentration is low or there is basically no water in the loose layer, prepare the Ca 2+ and CO3 2-At the same time, two water pipes are set in the borehole to the bottom of the hole to inject the calcium-containing water solution. 2+ and CO3 2- The calcified aqueous solution enters the Quaternary loose layer.

[0022] Preferably, the method further comprises step f. testing the calcification diagenesis effect through effect monitoring drilling.

[0023] Preferably, in step f, if the water level in the effect monitoring hole cannot be restored to the original groundwater level, the recharge amount of the calcified aqueous solution is reduced until no water accumulates in the effect monitoring borehole after pumping, and then the recharge of the calcified aqueous solution is stopped.

[0024] Preferably, the method further includes step g. constructing a core drilling hole for the diagenesis effect of the Quaternary loose layer within the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis, coring the drilling section from the drilling depth below 0.5h to the top interface of the bedrock, observing the integrity and mechanical strength of the core, and if the uniaxial compressive strength of the core is lower than the set value, continuing to inject the calcified aqueous solution; until the compressive strength reaches the set value.

[0025] Preferably, in step g, a Quaternary loose layer diagenetic effect core drilling hole is constructed near the effect monitoring hole.

[0026] Beneficial effects: Based on the migration and load transfer mechanism of the Quaternary loose layer caused by coal mining, the present invention fully considers the ion composition and content of the water storage in the Quaternary loose layer, and carries out targeted calcified water solution recharge drilling, effect observation drilling and preparation of calcified water solution; the calcium carbonate precipitate generated by the chemical reaction of the calcified water solution and groundwater is used to consolidate and shape the loose sand / soil particles in the Quaternary loose layer, thereby forming a calcified diagenetic body of a certain thickness within the range of the Quaternary loose layer affected by mining, effectively blocking the downward transmission of a large amount of overlying loads, and avoiding composite fracture of the overburden key layer, which can not only significantly reduce the development height of water-conducting fissures and prevent the loss of shallow groundwater, but also reduce the mine pressure manifestation intensity of the underground mining face, achieving the dual purpose of water conservation and disaster reduction. Its use method is scientific and reliable, safe and environmentally friendly, and highly practical.

[0027] Compared with the existing technology, it has the following advantages:

[0028] (1) The loose sand / soil particles are cemented and solidified by calcium carbonate precipitates generated by the chemical reaction of calcified aqueous solution and the water storage of the Quaternary loose layer. The calcium carbonate precipitates are easily adsorbed on the surface of the sand / soil particles, which neither pollutes the groundwater nor is easily eroded by groundwater flow. The loose layer forms a bearing entity with a certain mechanical strength, effectively blocking the transmission of a large amount of overlying loads, avoiding compound fracture of the key overlying strata, and achieving the dual effects of water conservation and disaster reduction.

[0029] (2) The selected calcified aqueous solution can not only chemically react with groundwater to generate calcium carbonate precipitates and consolidate loose sand / soil particles, but also regulate the pH and hardness of groundwater to a certain extent, effectively improving the groundwater quality;

[0030] (3) The determination of water conservation and disaster reduction methods for calcification-induced diagenesis of the Quaternary loose layer that can adapt to different mining conditions can provide guarantees for water conservation mining and strong mine pressure control in mining areas with thick loose layers and thin bedrock. The implementation method is simple, safe, environmentally friendly and highly reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a plan view of the arrangement of the calcified water solution reinjection drilling hole and the effect observation drilling hole of the present invention;

[0032] Figure 2 The present invention Figure 1 AA cross-section diagram.

[0033] In the figure: 1-calcified water solution reinjection borehole, 2-effect observation borehole, 3-diagenetic effect core borehole. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are further described below in conjunction with the accompanying drawings:

[0035] like Figure 1-2 As shown, the water conservation and disaster reduction method for calcification-induced diagenesis of the Quaternary loose layer of the present invention comprises the following steps: before coal seam mining, whether a composite fracture occurs in the key layer of the overburden in the mining area is calculated based on the key layer theory to determine whether a calcified aqueous solution recharge borehole needs to be constructed in the corresponding area; if a composite fracture occurs in the key layer, a calcified aqueous solution recharge borehole 1 and an effect observation borehole 2 are constructed on the corresponding surface within a certain range within and outside the mining area; a suitable calcified aqueous solution is prepared according to the ion composition and content of the water stored in the Quaternary loose layer and injected from the calcified aqueous solution recharge borehole 1; the calcium carbonate precipitate generated by the chemical reaction of the calcified aqueous solution recharged into the loose layer with the groundwater is used to consolidate and induce diagenesis of the loose sand / soil particles, so that they form a whole with a certain bearing capacity, thereby preventing a large amount of load transfer in the loose layer and preventing composite fracture in the key layer, thereby achieving the purpose of groundwater protection and geological disaster prevention and control.

[0036] The specific steps are as follows:

[0037] a. Before coal seam mining, the key layer position and its fracture characteristics are judged based on the key layer theory for the geological boreholes at different positions in the mining area, and the mining area where the overburden key layer has compound fracture is determined; for the coal mining area where the key layer has compound fracture, the calcified water solution recharge borehole 1 and the effect observation borehole 2 are arranged; for the coal mining area where the key layer has layer-by-layer fracture, no relevant drilling is required;

[0038] b. For the coal mining area where compound fracture occurs in the key overburden strata, determine the plane and vertical range of the corresponding Quaternary loose strata that need to be induced to consolidate and diagenesize;

[0039] The plane range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis is the coal mining area (working face mining range) where the overburden key layer undergoes compound fracture plus the D+h range extending outward from the boundaries of the coal mining area, where D is the bedrock impact range caused by mining in the coal mining area, and h is the thickness of the Quaternary loose layer; when the mining coal seam is buried at a depth of H≤500m, When H>500m,

[0040] The vertical range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis is (0.5-0.8) h upward from the top interface of the bedrock;

[0041] c. Drilling 1 for the recharging of calcified aqueous solution and construction of drilling 2 for effect observation in the plane range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis;

[0042] The calcified aqueous solution recharge borehole 1 is a vertical borehole constructed from the ground surface, with a final hole depth of h. A PVC casing is arranged in the calcified aqueous solution recharge borehole 1, and the casing within the range of (0.5-0.8) h above the bottom of the hole is a flower pipe; the calcified aqueous solution recharge borehole 1 starts from the center of the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis, and is arranged in an array in the strike and dip at a spacing of 150-200m within the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis, and the outermost calcified aqueous solution recharge borehole 1 is less than 150m away from the boundary line of the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis;

[0043] The effect observation borehole 2 is a vertical borehole constructed from the ground surface. The effect observation borehole 2 is arranged at the four corners of the plane range boundary line where the Quaternary loose layer needs to be induced to consolidate and diagenesis, and the final hole depth is h; the borehole wall of the effect observation borehole 2 is closed with a casing from a depth of 0.5h below the ground surface, and other sections are protected with a flower pipe;

[0044] d. According to the ion composition and content of the water stored in the Quaternary loose layer, prepare a suitable calcified aqueous solution, and inject it into the loose layer through the calcified aqueous solution recharging borehole 1. The injection pressure should be greater than the phreatic head pressure of the loose layer, but should not exceed the head pressure corresponding to the thickness of the loose layer, so as to ensure that the calcified aqueous solution can be injected into the loose layer without outflow;

[0045] If the Quaternary loose layer water is rich in Ca 2+ , then the calcified aqueous solution is made of CO3 2- The chemical reagents and deionized water are mixed into an aqueous solution, CO3 2-The concentration is based on the energy and Ca 2+ If the Quaternary loose layer water storage Ca 2+ If the concentration is lower than 500 mg / L or there is basically no water in the loose layer, prepare the Ca 2+ and CO3 2- At the same time, two water pipes are set in the calcified water solution recharging borehole 1 to the bottom of the hole, which are used to simultaneously inject the Ca 2+ and CO3 2- The calcified aqueous solution enters the Quaternary loose layer;

[0046] e. During the recharging process of the calcified aqueous solution, calcium carbonate precipitates are generated and continuously migrate and diffuse from the bottom of the calcified aqueous solution recharging borehole 1 to the periphery. During the diffusion process, they are continuously adsorbed on the surface of loose sand / soil particles, and at the same time adsorb other precipitates and wrap them layer by layer, thereby effectively condensing and consolidating the loose sand / soil particles, so that they gradually form a bearing whole with a certain mechanical strength, blocking the transmission of the overlying load;

[0047] f. Perform a pumping test on the effect monitoring borehole 2 at intervals of 1-2 weeks; if the water level in the effect monitoring borehole 2 cannot be restored to the original groundwater level, reduce the amount of the calcified aqueous solution recharged until there is no more water accumulation in the effect monitoring borehole 2 after pumping, then stop the recharge of the calcified aqueous solution;

[0048] g. Within the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis, and near the effect monitoring hole 2, construct the Quaternary loose layer diagenetic effect coring borehole 3, and coring the drilling section from the drilling depth below 0.5h to the top interface of the bedrock, and observe the integrity and mechanical strength of the coring. If the uniaxial compressive strength of the coring is lower than 2-5MPa, it is necessary to continue to inject the calcified aqueous solution; thereafter, conduct core drilling tests at intervals of 2-3 weeks until the compressive strength exceeds 2-5MPa. The construction position of the next diagenetic effect coring borehole 3 is near the construction position of the previous diagenetic effect coring borehole 3.

[0049] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of methods under the inspiration of the present invention. Any technical solution that is the same or similar to that of the present application falls within the protection scope of the present invention.

Claims

1. A method for water conservation and disaster reduction in calcification-induced diagenesis of Quaternary loose layers, characterized in that: The following steps are involved: a. Before coal seam mining, determine the mining area where compound fracture occurs in the key overburden strata; b. For the coal mining area where compound fracture occurs in the key overburden strata, determine the plane and vertical range of the corresponding Quaternary loose strata that need to be induced to consolidate and diagenesize; c. Construction of drilling holes for recharging calcified aqueous solution on the surface corresponding to the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis; d. According to the ion composition and content of the water stored in the Quaternary loose layer, a calcified aqueous solution is prepared and injected into the loose layer through the calcified aqueous solution recharge borehole; e. During the reinjection process of the calcified aqueous solution, calcium carbonate precipitates are produced and continuously adsorbed on the surface of loose sand / soil particles, effectively condensing and consolidating the loose sand / soil particles, gradually forming a bearing entity with a certain mechanical strength, blocking the transmission of overlying loads.

2. The water conservation and disaster reduction method according to claim 1, characterized in that: In step b, the planar range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis is the coal mining area where compound fracture of the overburden key layer occurs plus the D+h range extending outward from the boundaries of the coal mining area, wherein D is the bedrock influence range caused by mining in the coal mining area, and h is the thickness of the Quaternary loose layer.

3. The water conservation and disaster reduction method according to claim 1 or 2, characterized in that: In step b, the vertical range of the Quaternary loose layer that needs to be induced to consolidate and diagenesis is (0.5-0.8) h upward from the top interface of the bedrock.

4. The water conservation and disaster reduction method according to claim 1, characterized in that: In step c, the calcified water solution recharge boreholes are arranged in an array in strike and dip with spacing set within the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis, and the outermost calcified water solution recharge borehole is less than 150m away from the boundary line of the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis.

5. The water conservation and disaster reduction method according to claim 1, characterized in that: In step c, the calcified water solution reinjection borehole is a vertical borehole constructed from the surface, the final hole depth is h, and casing is arranged in the calcified water solution reinjection borehole. The casing in the range of (0.5-0.8)h above the bottom of the hole is a flower pipe, and h is the thickness of the Quaternary loose layer.

6. The water conservation and disaster reduction method according to claim 1, characterized in that: In step c, an effect observation borehole is also constructed. The effect observation borehole is a vertical borehole constructed from the ground surface. The effect observation borehole is arranged at the four corners of the plane range boundary line where the Quaternary loose layer needs to be induced to consolidate and diagenesis, and the final hole depth is h; the hole wall in the effect observation borehole is closed with casing from a depth of 0.5h below the ground surface, and other sections are protected with flower pipes, and h is the thickness of the Quaternary loose layer.

7. The water conservation and disaster reduction method according to claim 1, characterized in that: In step d, if the Quaternary loose layer water is rich in Ca 2+ , then the calcified aqueous solution is made of CO3 2- The chemical reagents and deionized water are mixed into an aqueous solution, CO3 2- The concentration is based on the energy and Ca 2+ Sufficient precipitation reaction occurs to set.

8. The water conservation and disaster reduction method according to claim 1, characterized in that: In step d, if the Quaternary loose layer water storage Ca 2+ If the concentration is low or there is basically no water in the loose layer, prepare the Ca 2+ and CO3 2- At the same time, two water pipes are set in the borehole to the bottom of the hole to inject the calcium-containing water solution. 2+ and CO3 2- The calcified aqueous solution enters the Quaternary loose layer.

9. The water conservation and disaster reduction method according to claim 6, characterized in that: The method also includes step f. testing the calcification diagenesis effect through the effect monitoring borehole. If the water level in the effect monitoring borehole cannot be restored to the original groundwater level, the reinjection amount of the calcification aqueous solution is reduced until no water accumulates in the effect monitoring borehole after pumping, and then the reinjection of the calcification aqueous solution is stopped.

10. The water conservation and disaster reduction method according to claim 9, characterized in that: The method also includes step g. constructing a core drilling hole for the diagenesis effect of the Quaternary loose layer within the plane range where the Quaternary loose layer needs to be induced to consolidate and diagenesis, coring the drilling section from the drilling depth below 0.5h to the top interface of the bedrock, observing the integrity and mechanical strength of the core, and if the uniaxial compressive strength of the core is lower than the set value, it is necessary to continue to inject the calcified aqueous solution until the compressive strength reaches the set value.

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