Roof water control method for constructing waterproof curtain based on freezing

Abstract

The invention relates to the technical field of mineral resource mining, in particular to a roof water control method for constructing a waterproof curtain based on freezing, and the method comprises the steps: determining the occurrence characteristics of a working face roof aquifer in overlying strata, predicting the development range of a water-conducting fracture of the working face roof overlying strata, and obtaining a waterproof curtain according to the relative position relation between the development range of the water-conducting fracture zone and the aquifer. Determining the type of the aquifer needing to be prevented and controlled; and a freezing station is established, freezing holes are drilled in the target layer, freezing modification is conducted on the water-containing rock stratum, and a waterproof curtain is formed in the target water-containing layer. According to the water control method for building the waterproof curtain to cut off the roof aquifer supply based on the freezing method, the designated area of the roof aquifer is modified through the freezing technology, the adaptability to the stratum is high, the strength of the frozen rock stratum is improved, and the water blocking performance is greatly improved; a water blocking curtain is formed in an original rock stratum to cut off supply of a water-bearing layer, and the groundwater runoff direction in the top plate water-bearing layer is changed, so that groundwater runoff cannot flow into a working face in a large range in the recovery period.

Description

Technical Field

[0001] The invention relates to the technical field of mineral resource mining, and in particular to a roof water control method based on freezing to construct a waterproof curtain. Background Art

[0002] The near-surface aquifers and underground sandstone aquifers in the mining area are groundwater resources with important ecological value. When the mining fissures formed by mining the ore layer communicate with the above-mentioned aquifers with strong water-richness, the aquifer water will flow into the working face along the mining fissures, which will not only destroy the groundwater resources in the area and increase the workload of mine drainage, but also cause roof water disasters in severe cases, threatening the safe production of the mine.

[0003] At present, there are three main types of roof water disaster prevention and control according to different management principles. The first is to use drilling projects to pre-drain and reduce the aquifer; the second is to use grouting technology to fill the mining cracks to block the water flow path; the third is to adjust the mining technology to reduce the development height of the water-conducting fracture zone, such as limited thickness mining, strip mining, filling mining, etc. to reduce the development height of the water-conducting fracture zone.

[0004] The above methods can effectively reduce the amount of water gushing during the mining process of the working face and ensure the safe mining of the working face, but there are also certain shortcomings: if drilling engineering is used to pre-drain and reduce the water when facing an aquifer with high water pressure and strong lateral recharge, the high-intensity drainage will not only increase the drainage cost of the mine, but also cause a great waste of groundwater resources. This method will not reduce the drainage volume of the entire process before, during and after the mining of the working face; if the grouting process is used to fill the mining fractures to block the water flow path, due to the randomness of the development of mining fractures, relying on the existing exploration technology, it is impossible to achieve a full-scale detection of the fracture distribution, resulting in the inability of grouting to accurately enter the through-type fractures with water conductivity, and the efficiency of plugging the leakage of roof water is greatly reduced; if the method of suppressing the development of water-conducting fracture zones by limited thickness mining, strip mining, filling mining and other processes is used, it will cause a great waste of coal resources. Summary of the invention

[0005] The present invention provides a roof water control method based on freezing to construct a waterproof curtain, which is used to solve the above-mentioned defects in the existing roof water hazard prevention and control methods. Artificial refrigeration technology is used to freeze the water and rock in a specified range in the roof aquifer together to achieve the purpose of weakening the permeability of the rock formation, and finally form a continuous and impermeable waterproof curtain with a certain contour. Under the interception effect of the waterproof curtain, the direction of groundwater runoff can be changed, thereby reducing the large amount of water in the roof aquifer flowing into the mining face through mining cracks.

[0006] The present invention provides a roof water control method for constructing a waterproof curtain based on freezing, comprising the following steps S1-S6.

[0007] S1. Combined with the exploration drilling in the working face area, determine the thickness and spatial position of the aquifer in the overburden of the working face roof.

[0008] S2. Predict the development range of water-conducting fractures in the overburden of the working face roof, and based on the thickness and spatial position of the aquifer determined in step S1, determine the aquifer affected by the water-conducting fractures, and classify the aquifer types according to the degree of impact.

[0009] S3. Based on the aquifer type divided in step S2, design the type, spatial position and geometric characteristics of the freezing water-blocking curtain to be constructed.

[0010] S4. Establish a ground or underground freezing station according to the type of freezing watertight curtain, and install refrigeration equipment and refrigeration pipelines in the freezing station; construct freezing drilling holes, and the final hole position of the freezing drilling holes must exceed the boundary of the freezing watertight curtain to be constructed. When the hole depth is <100m, the drilling spacing of the freezing drilling holes is 1100~2000mm, and when the hole depth is ≥100m, the drilling spacing of the freezing drilling holes is 1200~1800mm.

[0011] S5. The segmented freezing length is designed according to the strike length of the working face. The refrigeration device is connected to the freezing borehole through the refrigeration pipeline to carry out the active freezing stage construction. The freezing borehole is used to perform in-situ freezing modification on the water-bearing rock formation to form the required frozen waterproof curtain inside the aquifer, thereby cutting off the recharge of aquifer water to the mining area through mining fractures during coal mining.

[0012] S6. After the active freezing stage is completed, the aquifer above the middle of the working face is drilled and dredged through upward drilling construction. After the dredging is completed, the working face is mined, and a maintenance freezing stage is carried out during mining. After mining is completed, freezing is stopped and thawed naturally.

[0013] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, predicting the development range of water-conducting cracks in the overlying rock of the working face roof in step S2 includes obtaining the height and width of the water-conducting crack zone, the height of the water-conducting crack zone is determined by an empirical formula method, an analogy prediction method or a drilling measurement method, and the width of the water-conducting crack zone is determined based on the measured rock stratum movement angle and mining experience data.

[0014] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S2, aquifer types are divided according to the degree of impact, and the divided aquifer types include: aquifers that are completely penetrated by water-conducting fracture zones, forming lateral recharge type aquifers; aquifers that are not completely penetrated by water-conducting fracture zones, forming vertical recharge type aquifers.

[0015] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S3, the types of waterproof curtains to be constructed include vertical waterproof curtains and horizontal waterproof curtains.

[0016] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S3, the spatial position of the waterproof curtain to be constructed is designed to include: the vertical waterproof curtain is constructed in an aquifer that is completely penetrated by a water-conducting fracture zone, and the vertical waterproof curtain is outside the development range of water-conducting fractures; the horizontal waterproof curtain is constructed in an aquifer that is not completely penetrated by a water-conducting fracture zone, and the horizontal waterproof curtain must cover the development range of water-conducting fractures in the aquifer.

[0017] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S4, the geometric features of the waterproof curtain to be constructed include: the vertical waterproof curtain is perpendicular to the aquifer penetrated by the water-conducting cracks, or is constructed at an angle to the aquifer penetrated by the water-conducting cracks; the vertical height of the vertical waterproof curtain is greater than the thickness of the aquifer penetrated by the water-conducting cracks, and the thickness of the vertical waterproof curtain satisfies that the water pressure of the aquifer penetrated by the water-conducting cracks cannot penetrate; the segmented freezing length of the vertical waterproof curtain satisfies that it is greater than the short-term recovery length of the working face.

[0018] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S4, the geometric features of the waterproof curtain to be constructed are designed to include: the width of the horizontal waterproof curtain is greater than the development width of the water-conducting cracks in the aquifer that is not penetrated by the water-conducting cracks; the thickness of the horizontal waterproof curtain satisfies that the water pressure in the aquifer that is not penetrated by the water-conducting cracks cannot penetrate; the horizontal segmented freezing length of the horizontal waterproof curtain satisfies that it is greater than the short-term recovery length of the working face.

[0019] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S4, the construction of frozen drilling includes two construction methods: one is above-ground construction, which is suitable for constructing a waterproof curtain close to the ground surface; the other is underground construction, which is suitable for constructing a waterproof curtain close to the coal seam.

[0020] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, the freezing holes drilled in step S4 include a freezing hole matrix formed by multiple freezing holes arranged in multiple rows, and the freezing hole matrix is ​​constructed based on the geometric characteristics of the waterproof curtain to be constructed.

[0021] According to a roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S5, forming the desired frozen waterproof curtain inside the aquifer includes: carrying out freezing operations in the aquifer, expanding the frozen waterproof curtain in the aquifer to the desired geometric features, the freezing temperature is -30°C~35°C, and the freezing time is >30 days; in step S6, the maintenance freezing stage is the stage of normal coal seam recovery after the frozen waterproof curtain reaches the desired geometric features, and the freezing temperature is -25°C~-30°C.

[0022] The roof water control method based on freezing to construct a waterproof curtain provided by the present invention is a water control method for cutting off the recharge of the roof aquifer by constructing a waterproof curtain based on the freezing method, aimed at geological conditions where the aquifer has a large amount of water and sufficient recharge. The freezing technology can be used to modify the designated area of ​​the roof aquifer. The frozen rock formation not only has increased strength but also greatly enhanced water barrier properties, forming a water-barrier curtain in the original rock formation. The recharge of the aquifer is cut off under the interception effect of the waterproof curtain, changing the direction of groundwater runoff in the roof aquifer, so that the groundwater runoff cannot flow into the working face on a large scale during mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a flow chart of a roof water control method based on freezing to construct a waterproof curtain provided by the present invention.

[0025] Figure 2 It is a schematic diagram of the implementation structure of the roof water control method based on freezing to construct a waterproof curtain provided by the present invention.

[0026] Figure numerals: 1. water-conducting fracture zone; 2. first aquifer; 3. second aquifer; 4. vertical waterproof curtain; 5. horizontal waterproof curtain. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0028] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0029] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0030] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0031] One embodiment of the present invention provides a method for controlling water on a roof based on freezing to construct a waterproof curtain, see Figure 1 As shown, the process includes the following steps S1 to S6.

[0032] S1. Combined with the exploration drilling in the working face area, based on the exploration drilling columnar data in the mine study area, determine the thickness and spatial location of the aquifer in the overburden of the working face roof; S2, predicting the development range of water-conducting fractures in the overburden of the working face roof, and based on the thickness and spatial position of the aquifer determined in step S1, determining the aquifer affected by the water-conducting fractures, and classifying the aquifer types according to the degree of impact; S3. Based on the aquifer type classified in step S2, design the type, spatial position and geometric characteristics of the freezing water-blocking curtain to be constructed; S4. Establish a ground or underground freezing station according to the type of freezing water-proof curtain, and install refrigeration equipment and refrigeration pipelines in the freezing station; construct freezing drilling holes, and the final hole position of the freezing drilling hole must exceed the boundary of the freezing water-proof curtain to be constructed. When the hole depth is <100m, the drilling spacing of the freezing drilling holes is 1100~2000mm, and when the hole depth is ≥100m, the drilling spacing of the freezing drilling holes is 1200~1800mm; S5. The segmented freezing length is designed according to the strike length of the working face. The refrigeration device is connected to the freezing borehole through the refrigeration pipeline to carry out the active freezing stage construction. The freezing borehole is used to perform in-situ freezing modification on the water-bearing rock formation to form the required frozen water-proof curtain inside the aquifer to cut off the recharge of aquifer water to the mining area through the mining fractures during coal seam mining; S6. After the active freezing stage is completed, the aquifer above the middle of the working face is drilled and dredged through upward drilling construction. After the dredging is completed, the working face is mined, and a maintenance freezing stage is carried out during mining. After mining is completed, freezing is stopped and thawed naturally.

[0033] It is understandable that the prevention and control of roof water has achieved fruitful research results in basic theory and engineering practice. However, due to the complexity and diversity of coal mining conditions, the water hazard prevention and control technology under certain special geological conditions is not yet mature, and there is a lack of targeted prevention and control methods. For example, under high-intensity mining conditions such as large mining height, fully mechanized caving mining, and rapid advancement technology, how to prevent and control the thick aquifer with high water pressure and sufficient replenishment within the scope of mining damage is a technical problem that needs to be solved urgently. The roof water control method based on freezing to build a waterproof curtain in this embodiment is a water control method based on freezing to build a waterproof curtain to cut off the replenishment of the roof aquifer, which is proposed for the geological conditions where the aquifer has a large amount of water and sufficient replenishment. The specified area of ​​the roof aquifer can be modified by freezing technology. The frozen rock formation not only increases its strength but also greatly enhances its water barrier performance. A water barrier curtain is formed in the original rock formation. Under the interception effect of the waterproof curtain, the replenishment of the aquifer is cut off, and the direction of groundwater runoff in the roof aquifer is changed, so that the groundwater runoff cannot flow into the working face on a large scale during the mining period. The roof water control method based on freezing to construct a waterproof curtain in this embodiment is suitable for strong water-rich aquifers such as soil layers and rock layers with sufficient water content (generally greater than 10%); the groundwater flow velocity in the aquifer is ≤40m / day and night; the experimental freezing point of the groundwater salinity in the aquifer meets the freezing requirements, which has important guiding and practical significance for reducing the water gushing amount during the recovery of the working face.

[0034] Specifically, in step S2, predicting the development range of water-conducting fractures in the overburden of the working face roof includes obtaining the height and width of the water-conducting fracture zone, see Figure 2As shown, the height of the water-conducting fracture zone 1 is used to determine the aquifer affected in the vertical direction, and the width of the water-conducting fracture zone 1 is used to determine the lateral range of the affected aquifer, and the mining damage range is estimated based on the geometric characteristics of the mining face (inclination, dip, length, width, mining height) and the overburden type. The height of the water-conducting fracture zone 1 can be comprehensively determined by empirical formula method, analogy method or actual measurement method, and the width of the water-conducting fracture zone 1 can be determined based on the actual rock stratum movement angle and previous mining experience data. The methods used to determine the height and width of the water-conducting fracture zone 1 in this embodiment are all existing known methods and are not specifically described here.

[0035] Furthermore, in step S2, the aquifer types are divided according to the degree of impact, and the divided aquifer types include two types: one is the aquifer that is completely penetrated by the water-conducting fracture zone, forming a lateral recharge type aquifer; the other is the aquifer that is not completely penetrated by the water-conducting fracture zone, forming a vertical recharge type aquifer.

[0036] Specifically, the spatial positions of all aquifers in the overburden structure determined in step S1 and the development range of water-conducting fractures obtained in step S2 are compared to classify the aquifers on the top plate of the working face and determine the aquifers that need to be prevented and controlled. Figure 2 As shown in the figure, after coal seam mining, the water-conducting fracture zone 1 affects two highly water-rich sandstone aquifers above the coal seam, namely the first aquifer 2 and the second aquifer 3, wherein the first aquifer 2 crosses the middle of the water-conducting fracture zone 1 and is completely penetrated by the water-conducting fracture zone 1, and the recharge of the first aquifer 2 is mainly lateral recharge, and the second aquifer 3 is located at the upper boundary of the water-conducting fracture zone 1, and the top boundary of the water-conducting fracture zone 1 develops to the inside of the second aquifer 3, and the second aquifer 3 is not completely penetrated by the water-conducting fracture zone 1, and the recharge of the second aquifer 3 is mainly vertical recharge. Under the condition of no interception, the aquifer water of the above two sandstone aquifers flows into the goaf along the formed water-conducting fracture channel, and the cumulative water inflow gradually increases with time under the action of recharge, resulting in a large amount of water inflow from the roof during the recovery of the working face, which cannot ensure the efficient mining of coal resources and causes waste of aquifer water resources.

[0037] The types of waterproof curtains to be constructed as determined in the above step S4 include vertical waterproof curtains and horizontal waterproof curtains. Among them, the vertical waterproof curtain is constructed in the aquifer that is completely penetrated by the water-conducting fracture zone, and the vertical waterproof curtain is outside the boundary of the development range of the water-conducting fractures; the horizontal waterproof curtain is constructed in the aquifer that is not completely penetrated by the water-conducting fracture zone, and the horizontal waterproof curtain covers the development range of the water-conducting fractures in the aquifer located at the upper boundary of the development range of the water-conducting fractures. The vertical waterproof curtain is perpendicular to the aquifer penetrated by the water-conducting fractures, or is constructed at an angle to the aquifer penetrated by the water-conducting fractures; the vertical height of the vertical waterproof curtain is greater than the thickness of the aquifer penetrated by the water-conducting fractures, and the thickness of the vertical waterproof curtain satisfies that the water pressure of the aquifer penetrated by the water-conducting fractures cannot penetrate; the segmented freezing length of the vertical waterproof curtain satisfies that it is greater than the short-term recovery length of the working face. The width of the horizontal waterproof curtain is greater than the development width of the water-conducting cracks in the aquifer that is not penetrated by the water-conducting cracks; the thickness of the horizontal waterproof curtain is such that the water pressure in the aquifer that is not penetrated by the water-conducting cracks cannot penetrate; the horizontal segmented freezing length of the horizontal waterproof curtain is greater than the short-term mining length of the working face.

[0038] It needs to be understood that the spatial position of the vertical waterproof curtain and the horizontal waterproof curtain is outside the boundary of the development range of water-conducting fractures and is not affected by mining. The frozen curtain formed by them can minimize the impact of mining on the working face and avoid the weakening of the waterproof effect of the formed frozen curtain after being damaged by mining.

[0039] Specifically, see Figure 2As shown, for the aquifer that is completely penetrated by the water-conducting fracture zone 1, that is, the first aquifer 2, a vertical waterproof curtain 4 is constructed, the main purpose of which is to cut off the lateral recharge of the aquifer; for the aquifer that is affected by the water-conducting fracture zone 1 but not penetrated, that is, the second aquifer 3, a horizontal waterproof curtain 5 is constructed. Secondly, it is necessary to determine the spatial position of the waterproof curtain based on the spatial position of the aquifer affected by the water-conducting fracture obtained in step S3. In order to reduce or avoid the impact of mining on the interception effect of the waterproof curtain, the vertical waterproof curtain 4 should be outside the development boundary of the water-conducting fracture zone 1, and the horizontal waterproof curtain 5 should cover the development range of the water-conducting fracture zone 1 in the second aquifer 3. Finally, the geometric features of the waterproof curtain are designed according to the type of waterproof curtain. The vertical waterproof curtain 4 can be at a certain angle or completely vertical, which needs to be determined according to the specific conditions of the project site, but the vertical height must be completely greater than the thickness of the first aquifer 2. The thickness of the vertical waterproof curtain 4 must meet the minimum thickness that the water of the first aquifer 2 cannot penetrate, and the horizontal segmented freezing length of the vertical waterproof curtain 4 must be greater than the short-term recovery length of the working face. The width of the horizontal waterproof curtain 5 must be greater than the development width of the water-conducting fracture zone 1 in the second aquifer 3. The thickness of the horizontal waterproof curtain 5 must meet the minimum thickness that the water of the second aquifer 3 cannot penetrate, and the horizontal segmented freezing length of the horizontal waterproof curtain 5 must be greater than the short-term recovery length of the working face. Regardless of whether the waterproof curtain is constructed vertically or horizontally, the spatial position must completely block the channel for the water flow of this aquifer to the water-conducting fracture zone 1.

[0040] It should be understood that the constructed waterproof curtain also needs to be designed with basic parameters. The average temperature of the freezing curtain should be determined according to the buried depth of the freezing curtain, generally around -8 to -12°C. When the frozen wall is subjected to heavy loads and the water barrier safety requirements are high, a lower average temperature of the freezing curtain should be taken. The waterproof curtain is mainly formed by freezing holes, so the spacing, depth and type (horizontal, vertical, inclined) of the freezing holes must meet the requirements of the design size so that the formed freezing curtain has continuity.

[0041] The control spacing of the freezing holes should be determined according to the freezing period requirements, the designed brine temperature and the average freezing temperature. The roof water control method based on freezing to construct a waterproof curtain provided by the present invention, in step S4, the construction of freezing drilling includes two construction methods: one is the construction on the well, which is applicable when the waterproof curtain to be constructed is close to the ground surface; the other is the construction underground, which is applicable when the waterproof curtain to be constructed is close to the coal seam. The freezing holes drilled in step S4 can be multiple freezing holes arranged in a single row. When the freezing holes are horizontal or inclined freezing holes, the freezing holes are 30~60m deep, and the spacing between two adjacent freezing holes is 1100~2000mm; when the freezing holes are vertical freezing holes, the freezing holes are within 100m deep, and the spacing between two adjacent freezing holes is 1200~1800mm.

[0042] In the roof water control method based on freezing to construct a waterproof curtain provided by the present invention, the active freezing stage construction in step S5 can be completed by a one-time freezing full-depth method or a segmented freezing method. Different freezing schemes are adopted for different hydrological, geological and engineering backgrounds to achieve the best economic benefits. For example, during the mining of the workshop, the advancement speed of the working face is limited. If the designed area is frozen once along the direction of the working face, it will greatly increase the unnecessary freezing workload and fail to achieve the best economic benefits.

[0043] Among them, the one-time freezing full-depth method refers to a freezing method in which the depth of all freezing holes is consistent with the maximum freezing hole depth, and the full depth is frozen at one time to form a frozen wall. When the freezing depth is large and the hydrological and engineering geological conditions are relatively suitable, the segmented freezing method can be used to divide the entire freezing depth into several sections, and freeze the frozen wall in sections. The freezing pipe arrangement of this scheme is the same as the one-time freezing full-depth method, except that a freezer with a different structure is used to achieve the purpose of segmented freezing. In actual projects, the strike length of the working face is often large, and the segmented freezing method should be used. The segmented freezing length is designed according to the strike length of the working face, and the freezing is performed in sections along the direction of the working face along the advancement direction. The segmented length needs to be determined in combination with the strike length of the working face and the advancement speed. The segmented freezing length L is calculated: , where v is the working face advancement speed, m / d; d is the number of days, which is 50 days; when the segment freezing length L is less than or equal to 50m, the next segment is frozen.

[0044] It is understandable that after the aquifer is penetrated by the mining cracks, it not only increases the water inflow of the mine, affecting the safe mining of the working face, but also accelerates the flow rate of the water in the aquifer, making it more difficult to freeze. Therefore, the target aquifer needs to be frozen to construct a waterproof curtain before coal mining. In order to form a frozen waterproof curtain, the roof water control method based on freezing to construct a waterproof curtain provided by the present invention can be used to construct an aquifer waterproof curtain, and the water-bearing rock formation is in-situ frozen and modified by freezing drilling to form the desired frozen waterproof curtain inside the aquifer. The frozen waterproof curtain in the aquifer is expanded to the desired geometric features, and the aquifer water is cut off from replenishing the mining area through the mining cracks during coal mining. The freezing temperature is -30℃~35℃, and the freezing time is >30 days.

[0045] Among them, in the process of freezing construction in the drilled freezing hole using a freezer, a freezing pipe is installed in the freezing hole. The freezing pipe should be made of low-carbon steel seamless steel pipe. The diameter can be 89~127mm, not less than 73mm, and the pipe wall thickness should not be less than 5mm. The selection of the freezer is determined by the refrigeration capacity of the refrigeration station, the condensing temperature of the refrigeration cycle system, and the evaporation temperature of the refrigeration cycle system to determine the model and quantity of the refrigeration equipment. (The condensing temperature of the refrigeration cycle system is 3~5℃ higher than the outlet water temperature of the cooling water circulation system, and the evaporation temperature of the refrigeration cycle system is 5~7℃ lower than the temperature of the refrigerant circulation system). Among them, the selection of the refrigerant medium of the freezer, the lowest refrigerant medium temperature should be determined according to the average temperature of the designed freezing curtain and the formation environment, and is generally selected in the range of about -25~-30℃. The cooling capacity required for freezing by the freezer is calculated using the following formula , where Q represents the total heat absorption capacity of the freezing pipe (KJ / h); L represents the length of the freezing pipe (m); D represents the outer diameter of the freezing pipe, and K represents the heat absorption coefficient of the freezing pipe, which is 1047~1172 (kj); the refrigeration capacity of the freezing station is calculated by the following formula , where It represents the refrigeration capacity of the refrigeration station (kj / h); L represents the cooling loss coefficient, which is between 1.1 and 1.2.

[0046] The freezing system is installed according to the parameters determined in the above process. The freezing system consists of a freezing station, a freezing circulation system, and freezing pipelines. The low-temperature medium produced by the freezing station is sent to the freezer through the pipeline. After the low-temperature medium circulates in the freezer, it returns to the freezing station to be cooled again. The low-temperature medium circulates in the freezer and absorbs the heat in the surrounding rock formation to form a freezing column. The freezing column gradually expands and connects to form a freezing wall until the designed thickness and strength are reached.

[0047] The roof water control method based on freezing to construct a waterproof curtain provided by the present invention uses artificial refrigeration technology to freeze the water and rock in a specified range in the roof aquifer together to achieve the purpose of reducing the permeability of the rock formation, and finally forms a continuous and impermeable waterproof curtain with a certain contour. Under the interception effect of the waterproof curtain, the groundwater runoff direction can be changed, thereby reducing the large-scale influx of roof aquifer water into the mining face through mining cracks. This water control mining method based on the freezing method to construct a waterproof curtain to intercept the recharge of the roof aquifer is suitable for various complex water-bearing strata, has good water-proof properties, strong anti-seepage ability of the frozen body, and is easy to control. The freezing holes can be flexibly arranged according to different structural forms and site conditions, and vertical freezing, horizontal freezing, inclined hole freezing, and local freezing can be performed. The formed frozen wall waterproof curtain can withstand underground loads as a temporary supporting structure. The geometric shape design of the frozen wall is easy to arrange the freezing holes. As a water-sealing structure, it can resist the action of groundwater to form a closed waterproof curtain.

[0048] It should be noted that the roof water control method based on freezing to construct a waterproof curtain provided by the present invention, after the active freezing stage is completed, the aquifer above the middle of the working face is drilled and dredged through upward drilling construction. After the dredging is completed, the working face is mined, and a maintenance freezing stage is carried out during mining. The maintenance freezing stage is the stage in which normal coal seam mining is carried out after the frozen waterproof curtain reaches the required geometric characteristics. The freezing temperature is -25℃~-30℃. Freezing is stopped after mining is completed and it thaws naturally.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A roof water control method based on freezing to build a waterproof curtain, characterized in that: include: S1. Determine the thickness and spatial position of the aquifer in the overburden of the working face roof in combination with the exploration drilling in the working face area; S2, predicting the development range of water-conducting fractures in the overburden of the working face roof, and based on the thickness and spatial position of the aquifer determined in step S1, determining the aquifer affected by the water-conducting fractures, and classifying the aquifer types according to the degree of impact; S3. Based on the aquifer type classified in step S2, design the type, spatial position and geometric characteristics of the freezing water-blocking curtain to be constructed; S4. Establish a ground or underground freezing station according to the type of freezing water-proof curtain, and install refrigeration equipment and refrigeration pipelines in the freezing station; construct freezing drilling holes, and the final hole position of the freezing drilling hole must exceed the boundary of the freezing water-proof curtain to be constructed. When the hole depth is <100m, the drilling spacing of the freezing drilling holes is 1100~2000mm, and when the hole depth is ≥100m, the drilling spacing of the freezing drilling holes is 1200~1800mm; S5. The segmented freezing length is designed according to the strike length of the working face. The refrigeration device is connected to the freezing borehole through the refrigeration pipeline to carry out the active freezing stage construction. The freezing borehole is used to perform in-situ freezing modification on the water-bearing rock formation to form the required frozen water-proof curtain inside the aquifer to cut off the recharge of aquifer water to the mining area through the mining fractures during coal seam mining; S6. After the active freezing stage is completed, the aquifer above the middle of the working face is drilled and dredged through upward drilling construction. After the dredging is completed, the working face is mined, and a maintenance freezing stage is carried out during mining. After mining is completed, freezing is stopped and thawed naturally.

2. The method for controlling water on the roof based on freezing construction of waterproof curtain according to claim 1, characterized in that: In step S2, predicting the development range of water-conducting fractures in the overburden rock of the working face roof includes obtaining the height and width of the water-conducting fracture zone, the height of the water-conducting fracture zone is determined by an empirical formula method, an analogy prediction method or a drilling measurement method, and the width of the water-conducting fracture zone is determined according to the measured rock stratum movement angle and mining experience data.

3. The roof water control method based on freezing construction waterproof curtain according to claim 1 is characterized in that: In step S2, the aquifer types are divided according to the degree of impact, and the divided aquifer types include: Aquifers that are completely penetrated by water-conducting fracture zones form lateral recharge type aquifers; Aquifers that are not completely penetrated by water-conducting fracture zones form vertical recharge type aquifers.

4. The roof water control method based on freezing to build a waterproof curtain according to claim 3 is characterized in that: In step S3, the types of waterproof curtains to be designed and constructed include vertical waterproof curtains and horizontal waterproof curtains.

5. The roof water control method based on freezing construction waterproof curtain according to claim 4 is characterized in that: In step S3, the spatial position of the waterproof curtain to be constructed is designed to include: the vertical waterproof curtain is constructed in an aquifer that is completely penetrated by a water-conducting fracture zone, and the vertical waterproof curtain is outside the development range of water-conducting fractures; the horizontal waterproof curtain is constructed in an aquifer that is not completely penetrated by a water-conducting fracture zone, and the horizontal waterproof curtain must cover the development range of water-conducting fractures in the aquifer.

6. The roof water control method based on freezing to build a waterproof curtain according to claim 5, characterized in that: In step S4, the geometric features of the waterproof curtain to be constructed include: the vertical waterproof curtain is perpendicular to the aquifer penetrated by the water-conducting fractures, or is constructed at an angle to the aquifer penetrated by the water-conducting fractures; the vertical height of the vertical waterproof curtain is greater than the thickness of the aquifer penetrated by the water-conducting fractures, and the thickness of the vertical waterproof curtain satisfies that the water pressure of the aquifer penetrated by the water-conducting fractures cannot penetrate; the segmented freezing length of the vertical waterproof curtain satisfies that it is greater than the short-term recovery length of the working face.

7. The method for controlling roof water based on freezing construction waterproof curtain according to claim 6, characterized in that: In step S4, the geometric features of the waterproof curtain to be constructed also include: the width of the horizontal waterproof curtain is greater than the development width of the water-conducting cracks in the aquifer that is not penetrated by the water-conducting cracks; the thickness of the horizontal waterproof curtain is such that the water pressure in the aquifer that is not penetrated by the water-conducting cracks cannot penetrate; the horizontal segmented freezing length of the horizontal waterproof curtain is greater than the short-term recovery length of the working face.

8. The roof water control method based on freezing to build a waterproof curtain according to claim 1, characterized in that: In step S4, the construction of frozen drilling includes two construction methods: one is the above-ground construction, which is suitable for building a waterproof curtain close to the surface; the other is the underground construction, which is suitable for building a waterproof curtain close to the coal seam.

9. The method for controlling roof water based on freezing construction waterproof curtain according to claim 1, characterized in that: The freezing boreholes drilled in step S4 include a freezing hole matrix formed by a plurality of freezing boreholes arranged in multiple rows, and the freezing hole matrix is ​​constructed based on the geometric features of the waterproof curtain to be constructed.

10. The method for controlling water on the roof based on freezing construction of waterproof curtain according to claim 1, characterized in that: In step S5, forming the desired frozen waterproof curtain inside the aquifer includes: carrying out freezing operations in the aquifer to expand the frozen waterproof curtain in the aquifer to the desired geometric features, the freezing temperature is -30°C~35°C, and the freezing time is >30 days; in step S6, the maintenance freezing stage is the stage of normal coal seam recovery after the frozen waterproof curtain reaches the desired geometric features, and the freezing temperature is -25°C~-30°C.

Images