Mine filling body non-uniform permeability field test and analysis method based on sodium chloride and atmospheric precipitation combined tracing

Abstract

The invention aims to provide a field test and analysis method for non-uniform permeability of a mine filling body based on joint tracing of sodium chloride and atmospheric precipitation, and belongs to the technical field of mine hydrogeology. Sodium chloride and atmospheric precipitation are jointly used as a tracer agent, and the conductivity of the tracer agent is obviously increased after sodium chloride is dissolved in underground water; atmospheric precipitation naturally has a relatively low conductivity background value, and different conductivity differences of the two tracers are compared, so that the permeability difference of different parts of the mine filling body can be analyzed and researched according to the seepage distance and time of the underground water in the filling bodies at different positions and the underground water conductivity change characteristics.

Description

Technical Field

[0001] The invention belongs to the technical field of mine hydrogeology, and in particular relates to a field testing and analysis method for the non-uniform permeability of mine filling bodies based on combined tracing of sodium chloride and atmospheric precipitation. Background Art

[0002] Backfill mining is a mining method that injects a mixture of filling materials, such as tailings, waste rock, and water, into the goaf to support the surface and underground space, reduce ground subsidence and environmental impact, and ensure the safe recovery of underground working faces. While the backfill maintains the strength of the mine rock mass and the stability of the underground working face, its inherent water conductivity and permeability characteristics will bring potential water hazards to the underground working face. Existing backfill permeability research usually relies on laboratory testing or numerical simulation technology, but these methods usually require simplification or assumptions in the research process, resulting in a gap between the research results and actual conditions.

[0003] Conducting field tests under natural conditions can not only verify the reliability of theoretical analysis results, but also fully reflect the actual permeability of the filling body and provide relatively objective geological and hydrogeological information. Sodium chloride is a common tracer in mine hydrogeological research and is widely used in groundwater flow monitoring. It is more common to use it with colored tracers, but it is usually necessary to use special instruments to monitor the concentration changes of tracers in groundwater for analysis.

[0004] Atmospheric precipitation is a natural tracer and is widely used in various field conditions such as geological surveys. Invention patent application publication number CN111624679A (Quantitative analysis of groundwater nitrogen pollution sources based on multiple tracers) and CN115683478A (Reservoir water leakage based on water chemistry and hydrogen and oxygen isotope tracing) both use isotope or water chemistry characteristics in atmospheric precipitation for comparative analysis, but the cost of isotope and water chemistry characteristic analysis is relatively high.

[0005] In the field test of the permeability of mine filling bodies, if the tracer selection is based on the above, it is often necessary to purchase special instruments or entrust professional institutions to conduct tests, which is costly, time-consuming and labor-intensive. In addition, the permeability of the filling body has a non-uniform characteristic. The existing test method can only analyze the permeability of the filling body as a whole, and cannot study the differences in permeability of different parts of the filling body. Therefore, it is urgent to design a convenient test and analysis method that can reduce the cost of permeability testing of mine filling bodies and study the non-uniform permeability of different parts of the filling body. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a field testing and analysis method for the non-uniform permeability of mine fillings based on the combined tracing of sodium chloride and atmospheric precipitation, which can study the permeability differences in different parts of the filling. The testing method is simple and effective, can reduce the testing cost, and provide data support for studying the non-uniformity of the permeability of the filling.

[0007] To achieve the above object, the present invention adopts the following technical solution: A field testing method for the non-uniform permeability of mine fillings based on combined tracing of sodium chloride and atmospheric precipitation. This method uses sodium chloride and atmospheric precipitation together as tracers. The conductivity of sodium chloride increases significantly after dissolving in groundwater, while atmospheric precipitation naturally has a relatively low conductivity background value. By comparing the distinct conductivity differences of the two tracers, and based on the seepage distance and time of groundwater in fillings at different locations, the permeability differences in different parts of the mine filling can be analyzed and studied.

[0008] The specific steps are as follows: S1. Analysis of water filling conditions of the filling body; S2. Determine the scope of the on-site test; determine the relative position of the underground working surface and the ground affected by the water conduction of the filling body, and clarify the length, width and depth of the test site; S3. Monitoring of atmospheric precipitation and background values ​​of underground water filling points of filling bodies; S4. Selection of the timing for sodium chloride placement: When the rainfall is about to end, sodium chloride is placed through ground drilling; S5. Data collection and filling permeability analysis.

[0009] Furthermore, in step S1, the water source, water channel and water intensity of the filling body are analyzed, the hydraulic connection between the filling body and atmospheric precipitation is determined, and the filling body samples are taken to analyze the internal void development, main material composition and structural characteristics.

[0010] Furthermore, in step S2, after the on-site test scope is determined, the number of drill holes and the amount of sodium chloride to be placed are determined based on the on-site construction conditions, the distance between the underground working surface and the sodium chloride placement point, the location and density of the underground monitoring points, and the development of voids inside the filling body.

[0011] Furthermore, in step S3, background value monitoring is performed near the filling body at the underground working surface. The underground water filling intensity change characteristics of the filling body are monitored 3 days before the test. The conductivity of the underground filling body water filling position is monitored 3 days before the start of moderate to heavy rain at the test site. The underground monitoring point is selected at a location with a large water filling intensity for easy observation. The conductivity value of the monitoring point position is measured at the same time period and time interval every day, and the conductivity monitoring curve is drawn respectively. From the beginning of precipitation to the end of precipitation, rainwater samples are taken at the same time and place every day to measure the conductivity change.

[0012] Furthermore, in step S4, sodium chloride is added by pouring water into the borehole using a sprinkler truck to fully dissolve the sodium chloride, so that it dissolves into the filling body, and the sodium chloride solution seeps from shallow to deep through the gaps in the filling body into the underground monitoring point.

[0013] Further, in step S5, the permeability coefficient of the filling body of different monitoring points can be calculated by using the start time of atmospheric precipitation, the time interval with the obvious increase of water filling intensity of the underground monitoring point, and the straight-line distance between the sodium chloride delivery point and the monitoring point. In the data collection and analysis, the conductivity of the underground monitoring point position is measured on the day of sodium chloride delivery, and the same time period and time interval are monitored every day. Combined with the background value of the monitoring point monitored before the sodium chloride delivery, the conductivity change curve of each monitoring point is drawn. Atmospheric precipitation enters the filling body before the sodium chloride solution. The conductivity value of each monitoring point in the underground shows a continuous downward trend at the beginning. As the rain recedes, the sodium chloride solution gradually enters the filling body, and then the conductivity of each monitoring point in the underground turns, showing a continuous upward trend, indicating that the sodium chloride solution is injected into the filling body through the borehole and received in the underground. The relative speed of the filling body in different parts can be analyzed by using the time when the conductivity turns.

[0014] The beneficial effects of the present invention are as follows: The sodium chloride and atmospheric precipitation combined tracing method used in the present invention has the advantages that sodium chloride is cheap and easy to obtain; atmospheric precipitation is universal, and can be tested in mining areas with precipitation in a continuous and stable period of time; the two tracers are environmentally friendly, non-toxic and harmless; the test cost is low, simple and effective, and there is no need to purchase expensive instruments, and only a simple conductivity testing device is needed to complete the data collection work. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Implementation flow chart of the testing method of the present invention; Figure 2 is a cross-sectional schematic diagram of an embodiment of the present invention; Figure 3 A schematic plan view of an embodiment of the present invention; Figure 4This is a curve diagram of conductivity change of underground monitoring points according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] A method for field testing and analyzing the heterogeneous permeability of mine filling bodies based on sodium chloride and atmospheric precipitation combined tracing comprises the following steps: S1. Analysis of water filling conditions of the filling body; S2. Determine the scope of the on-site test; determine the relative position of the underground working surface and the ground affected by the water conduction of the filling body, and clarify the length, width and depth of the test site; S3. Monitoring of atmospheric precipitation and background values ​​of underground water filling points of filling bodies; S4. Selection of the timing for sodium chloride placement: When the rainfall is about to end, sodium chloride is placed through ground drilling; S5. Data collection and calculation and analysis of permeability differences in different parts of the filling body.

[0018] Example This embodiment provides a method for field testing and analyzing the heterogeneous permeability of mine filling bodies based on combined tracing of sodium chloride and atmospheric precipitation, which specifically includes the following steps.

[0019] (1) Analysis of filling water conditions. Analyze the filling water source, filling channels and filling intensity of the filling body, determine the hydraulic connection between the filling body and atmospheric precipitation, take filling body samples, and analyze the internal void development, main material composition and structural characteristics. Taking a coal mine in the Northeast Coalfield as an example, the rock strata and filling body are inclined to the north, the filling body is located below the shale aquiclude, and the bottom of the filling body is a tuff aquiclude. The filling body is exposed on the surface, and its outcrop can be recharged by atmospheric precipitation, resulting in an increase in the amount of water inflow underground. The relationship between atmospheric precipitation and filling body recharge is clear. The filling body sampled underground is mainly composed of shale, ash and river sand materials, with poor cementation and easy to break. The pores and cracks developed in the filling body are the main water filling channels. The filling body actually exposed underground is mainly filled with dripping and sprinkling, and the water filling intensity is between 20~30m 3 / h.

[0020] (2) Determine the scope of the on-site test. Determine the relative position of the underground working face and the ground affected by the water conduction of the filling body, and clarify the length, width, and depth of the test site. When implementing the test, the number of boreholes and the amount of sodium chloride to be placed need to take into account the on-site construction conditions, the distance between the underground working face and the sodium chloride placement point, the location and density of the underground monitoring points, and the development of the internal voids of the filling body. The test range of the embodiment is from the surface to the top of the -280 m horizontal working face in the well, with a length of 848 m, a width of 311 m, and a depth of 280 m. The range of 240 m to 260 m south of the working face is used as the sodium chloride placement range. Drill holes on the ground to the filling body are used as the sodium chloride placement point to allow the sodium chloride to enter the filling body along the inclination of the formation. The construction spacing of the boreholes is 210 m, and 5 boreholes are constructed, with a sodium chloride placement of 200 kg in each hole.

[0021] (3) Background value monitoring. Near the filling body of the underground working face, the underground water filling intensity change characteristics of the filling body were monitored 3 days before the test. 3 days before the start of moderate to heavy rain in the test site, the conductivity of the underground filling body water filling position was monitored. The underground monitoring point location was selected at a location with a higher water filling intensity for easy observation. The conductivity values ​​of the monitoring point locations were measured at the same time period and time interval every day, and the conductivity monitoring curves were drawn respectively. From the beginning to the end of precipitation, rainwater samples were collected at the same time and location every day to measure the conductivity changes. For example, the rainwater collected during the rainfall in the mining area in the embodiment was tested to have a conductivity value range of 450μs / cm~500μs / cm, and the conductivity was relatively stable.

[0022] (4) Choosing the timing of sodium chloride placement. When the rainfall is about to end, sodium chloride is placed through the ground borehole. Water is poured into the borehole using a sprinkler truck to fully dissolve the sodium chloride and allow it to dissolve into the filling body. The sodium chloride solution seeps from the shallow to the deep through the gaps in the filling body and enters the underground monitoring point.

[0023] (5) Data collection and analysis The time interval from the beginning of rainfall to the occurrence of a significant increase in the water filling intensity of the underground monitoring point is used. For example, from the beginning of rainfall to the five underground monitoring points: the contact tunnel, the return air tunnel 35 m, the return air tunnel 300 m, the return air tunnel 400 m, and the west monitoring point, the cumulative time for the increase in water inflow at the five locations is 43 h, 50 h, 45 h, 47 h, and 60 h respectively; the straight-line distances from the five placement points to the underground monitoring points are 260 m, 240 m, 255 m, 270 m, and 280 m respectively, and the calculated permeability coefficients of the filling bodies at the five monitoring points are 6.0 m / h, 4.8 m / h, 5.6 m / h, 5.7 m / h, and 4.6 m / h respectively. The conductivity of the underground monitoring point position was measured on the day of sodium chloride placement, and monitoring was carried out at the same time period and time interval every day. Combined with the background value of the monitoring point monitored before the sodium chloride was placed, the conductivity change curve of each monitoring point was drawn. Atmospheric precipitation enters the filling body before the sodium chloride solution. The conductivity values ​​at each monitoring point underground initially show a continuous downward trend. As the rain recedes, the sodium chloride solution gradually enters the filling body. Subsequently, the conductivity at each monitoring point underground turns and shows a continuous upward trend, indicating that the sodium chloride solution is injected into the filling body through the borehole and received underground. The turning point time of the conductivity from decline to increase at each monitoring point reflects the difference in permeability of the filling body in different seepage ranges. The stronger the permeability of the filling body in the local seepage range, the earlier the conductivity turning time. The filling body in the local seepage range at the three locations of the contact tunnel, the return air tunnel 300m, and the return air tunnel 400m has relatively strong permeability, and the permeability coefficient ranks in the top three; while the filling body in the local seepage range at the return air tunnel 35m and the west monitoring point has relatively weak permeability, and the permeability coefficient ranks in the last two.

[0024] 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 replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for field testing and analyzing the heterogeneous permeability of mine fillings based on sodium chloride and atmospheric precipitation combined tracing, characterized in that: This method uses sodium chloride and atmospheric precipitation as tracers. The conductivity of sodium chloride increases significantly after dissolving in groundwater, while atmospheric precipitation naturally has a relatively low conductivity background value. The distinct conductivity differences of the two tracers are compared, and the permeability differences in different parts of the mine filling body are analyzed and studied based on the seepage distance and time of groundwater in the filling body at different locations and the characteristics of groundwater conductivity changes.

2. The method for field testing and analyzing the heterogeneous permeability of mine filling bodies based on sodium chloride and atmospheric precipitation combined tracing according to claim 1 is characterized in that: The steps include: S1. Analysis of water filling conditions of the filling body; S2. Determine the scope of the on-site test; determine the relative position of the underground working surface and the ground affected by the water conduction of the filling body, and clarify the length, width and depth of the test site; S3. Monitoring of atmospheric precipitation and background values ​​of underground water filling points of filling bodies; S4. Selection of the timing for sodium chloride placement: When the rainfall is about to end, sodium chloride is placed through ground drilling; S5. Data collection and calculation and analysis of permeability differences in different parts of the filling body.

3. The method for field testing and analyzing the non-uniform permeability of mine fillings based on combined tracing of sodium chloride and atmospheric precipitation according to claim 2, characterized in that: In step S1, the water source, water channel and water intensity of the filling body are analyzed, the hydraulic connection between the filling body and atmospheric precipitation is determined, and the filling body sample is taken to analyze the internal void development, main material composition and structural characteristics.

4. The method for field testing and analyzing the non-uniform permeability of mine fillings based on sodium chloride and atmospheric precipitation combined tracing according to claim 2, characterized in that: In step S2, after the on-site test scope is determined, the number of drill holes and the amount of sodium chloride to be placed are determined based on the on-site construction conditions, the distance between the underground working surface and the sodium chloride placement point, the location and density of the underground monitoring points, and the development of voids inside the filling body.

5. The method for field testing and analyzing the non-uniform permeability of mine fillings based on sodium chloride and atmospheric precipitation combined tracing according to claim 2, characterized in that: In step S3, background value monitoring is performed near the filling body of the underground working face. The underground water filling intensity change characteristics of the filling body are monitored starting from 3 days before the test. The conductivity of the water filling position of the underground filling body is monitored starting from 3 days before the start of moderate to heavy rain in the test site. The underground monitoring points are selected at locations where the water filling intensity of the filling body is relatively large for easy observation. The conductivity values ​​of the monitoring points are measured at the same time period and time interval every day, and the conductivity monitoring curves are drawn respectively. During the process from the start of precipitation to the end of precipitation, rainwater samples are collected at the same time and place every day to measure the conductivity changes.

6. The method for field testing and analyzing the non-uniform permeability of mine fillings based on combined tracing of sodium chloride and atmospheric precipitation according to claim 2, characterized in that: In step S4, sodium chloride is added by pouring water into the borehole using a sprinkler truck to fully dissolve the sodium chloride, so that it dissolves into the filling body. The sodium chloride solution seeps from shallow to deep through the gaps in the filling body and enters different monitoring points underground.

7. The method for field testing and analyzing the non-uniform permeability of mine fillings based on sodium chloride and atmospheric precipitation combined tracing according to claim 2, characterized in that: The method of step S5 is as follows: using the start time of atmospheric precipitation, the time interval with the obvious increase in water filling intensity at the underground monitoring point, and the straight-line distance between the sodium chloride delivery point and the monitoring point, the filling body permeability coefficient of different monitoring points infiltration paths is calculated; the data collection and analysis, starting from the day of sodium chloride delivery, the conductivity of the underground monitoring point position is measured, and the same time period and time interval are monitored every day. Combined with the background value of the monitoring point monitored before the sodium chloride delivery, the conductivity change curve of each monitoring point is drawn. Atmospheric precipitation enters the filling body before the sodium chloride solution. At the beginning, the conductivity value of each monitoring point in the underground shows a continuous downward trend. As the rain recedes, the sodium chloride solution gradually enters the filling body. Subsequently, the conductivity of each monitoring point in the underground turns and shows a continuous upward trend, indicating that the sodium chloride solution is injected into the filling body through the borehole and is received in the underground.

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