Patent Application
20200378258
The present invention relates to the field of ecological protection technologies, and in particular, to a method for classifying a phreatic leakage disaster level in shallow coal seam mining.
Since coal resources in eastern China are gradually depleted, strategic westward moving of coal production will be continuously accelerated, so that a coal mining amount in western China will increase year by year. It is expected that a coal yield in western China will account for more than 70% of a total coal yield of China in the future. The reserves of coal resources in northern Shaanxi are extremely large, the coal quality is good, and a mining prospect is prosperous. At the same time, northern Shaanxi belongs to an arid-semiarid region, water resources are generally seriously insufficient, and the ecological and geological environment is fragile, which brings serious constraints and impacts on regional economy and social development. The Upper Pleistocene Sarawusu formation sand layer phreatic water with a large area distributed in the Mu Us desert beach in a northern Shaanxi coalfield is an important water source for maintaining ecological vegetation. However, for more than ten years, coal mining has caused extensive damage to the phreatic water resources in the area, gullies have been cut off, and water volumes of springs and lakes are reduced or the springs and lakes are even dried up, resulting in problems in water for industrial and agricultural use and environmental problems such as surface drought, vegetation wilting, and intensified desertification. Therefore, the Sarawusu formation sand layer phreatic water has become an important research subject of ecological and environmental protection in an arid-semiarid region of northern Shaanxi.
In recent years, the domestic geological community has carried out a lot of researches on the problem of water-preserved coal mining in the Jurassic coalfield in western China. Strategies and methods for water-preserved coal mining are discussed. A new viewpoint that a core of water-preserved coal mining is ecological water level protection is put forwarded. With regard to how to deal with a coordination relationship between coal mining and groundwater, more proper coal mining methods and engineering measures need to be used to achieve water-retaining coal mining. That is, problems about a water preservation degree, a way of water-retaining coal mining, and the like still need to be further researched. Whether shallow groundwater level lowering is caused by lateral recharge or vertical seepage can be clearly determined by using a monitored water level of a telemetering water level gauge, thereby classifying a phreatic leakage degree and a degree of affecting ecological vegetation, providing a basic basis for work such as mining area planning, and selecting a mining manner, and having significance of carrying out mining while protecting an ecological environment of an arid-semiarid region.
In view of the analysis above, the present invention aims at providing a method for classifying a phreatic leakage disaster level in shallow coal seam mining and is used to resolve a problem of a failure in accurately determining a phreatic leakage disaster level in coal mining areas. In addition, a corresponding water-preserved mining solution is formulated according to a phreatic leakage and a classified disaster level, thereby minimizing a level of damage to an ecological environment caused by mining.
An objective of the present invention is mainly achieved by using the technical solutions:
A method for classifying a phreatic leakage disaster level in shallow coal seam mining is provided, including the following steps:
S1. collecting a planar graph of a to-be-mined coal seam working face in a mining area, arranging a monitoring point, and burying a telemetering water level gauge to monitor a water level;
S2. according to the monitoring point arranged in step S1, during working face mining, monitoring a ground elevation at the monitoring point, calculating a ground subsidence amount, and collecting information about a drilling footage of the working face;
S3. plotting variation relationship curves of drilling footage and phreatic water level as well as drilling footage and ground subsidence according to the working face drilling footage and the ground subsidence amount that are obtained in step S2 and water level monitoring information obtained in step S1; and
S4. comparing the curve with a no-phreatic leakage graph, a slight-phreatic leakage graph, and a heavy-phreatic leakage graph; and classifying a mined coal seam working face as a no-phreatic leakage area, a slight-phreatic leakage area, or a heavy-phreatic leakage area.
Further, in the step S1, a location for arranging the monitoring point of the working face is located at the center of the working face, a used telemetering water level gauge satisfies requirements of “Instruments for stage measurement. Part 6: remote measuring stage gauge” (GB/T11828.6-2008), a buried depth of a probe of the water level gauge is located below a monitored water level during a mining process, and water level monitoring is performed immediately after the water level gauge is completely mounted.
Further, in the step S2, ground subsidence observation at the monitoring point is started when the distance between the drilling footage and the monitoring point is L, and ended when the monitored data becomes steady, that is, an accumulated ground subsidence amount continuously monitored in 5 days is less than 0.01 m, where a formula for calculating L is as follows:
where
L is an advanced influence distance, in m; h is a mining depth, in m; and w is an advanced influence angle, in °. According to mining depths and advanced influence angles of different mining working faces, start times of ground subsidence observation of different mining working faces are determined, and a first stage of ground subsidence, namely, a non-subsiding stage, is determined efficiently and accurately. A monitoring end time is a time when an accumulated ground subsidence amount continuously monitored in 5 days is less than 0.01 m. At this time, it can be considered in the art that the subsidence ends, and it is unnecessary to continue monitoring.
Further, in the step S2, a formula for calculating a ground subsidence amount at the monitoring point is as follows.
ΔH=He0−He, where
ΔH is a ground subsidence amount, in m; He0 is an initial ground elevation at the monitoring point, in m; and He is a ground elevation at the monitoring point during a mining process, in m.
Further, the step S2, the precision of monitoring of a ground elevation at the monitoring point is 0.001 m. In this precision, accuracy of the monitored data of the ground elevation at the monitoring point and accuracy of subsequently determining an end time of monitoring the ground elevation are ensured.
Further, in the step S4, a ground subsidence variation curve in each of the no-phreatic leakage graph, the slight-phreatic leakage graph, and the heavy-phreatic leakage graph is divided into five stages: stage 1: a non-subsiding stage, stage 2: a slow subsiding stage, stage 3: an accelerated subsiding stage, stage 4: a slowed-down subsiding stage, and stage 5: a steady subsiding stage;
Further, to better classify a phreatic leakage disaster level of a mining coal seam working face, the foregoing classifying method further includes the following step:
Further, a formula for calculating a water level buried depth of the slight-phreatic leakage area in step S4 is as follows:
S=He0−Hw, where
Further, the ecological water level is a groundwater level buried depth capable of maintaining good development and growth of typical vegetation, and the ecological water level is determined according to typical ground cover vegetation of the coal mining area.
Further, the method for classifying a phreatic leakage disaster level of a coal mining working face is applicable to a northwest coalfield.
(1) In the method for classifying a phreatic leakage disaster level in shallow coal seam mining, provided in the present invention, a phreatic leakage level over a coal mining area is directly determined and classified, and further, a coal mining working face is classified as an environmentally friendly area and an environmental disaster area, thereby providing an explicit basis for choosing a mining solution in a mining area. For the mining area, a corresponding water-preserved mining solution may be formulated according to a phreatic leakage disaster level, thereby minimizing damage to an ecological environment caused by mining.
(2) The classifying method of the present invention is simple and practical, where from a perspective of ecological protection, a water resource loss and an environmental disaster is determined for a shallow seam of a northwest coalfield, and a basis is provided for a choice of a mining manner in a mining area, and the method is of significance for ecological and environmental protection in a mining process of the northwest coalfield.
In the present invention, the foregoing technical solutions may alternatively be mutually combined, to implement more preferred combined solutions. Other features and advantages of the present invention are described below in the description, and some advantages may become obvious from the description or may be obtained by implementing the present invention. The objectives and other advantages of the present invention may be achieved and obtained from the content specified in the description, claims, and accompanying drawings.
The accompanying drawings are merely used for the purpose of illustrating specific embodiments, and are not to be construed as limitations to the present invention. In all the accompanying drawings, the same reference numeral indicates the same component.
Preferred embodiments of the present invention are specifically described below with reference to the accompanying drawings, where the accompanying drawings constitute a part of the present application, and are used together with the embodiments of the present invention to explain the principle of the present invention, and are not intended to limit the scope of the present invention.
The present invention provides a method for classifying a phreatic leakage disaster level in shallow coal seam mining, as shown in
S1. Collect a planar graph of a to-be-mined coal seam working face in a mining area, arrange a monitoring point, and bury a telemetering water level gauge.
The step specifically includes: collecting a planar graph of a to-be-mined working face, arranging a monitoring point at the center of the working face, where the used telemetering water level gauge satisfies requirements of “Instruments for stage measurement. Part 6: remote measuring stage gauge” (GB/T11828.6-2008), and a buried depth of a probe of the water level gauge is located below a monitored water level during a mining process, and performing water level monitoring immediately after the water level gauge is completely mounted.
S2. According to the monitoring point arranged in step S1, during working face mining, observe a ground elevation at the monitoring point, calculate a ground subsidence amount, and collect information about a drilling footage of the working face.
The step specifically includes that: a start time of monitoring the ground subsidence amount at the monitoring point is a time when the distance between the drilling footage and the monitoring point is L, and an end time thereof is a time when the monitored data becomes steady, that is, an accumulated ground subsidence amount continuously monitored in 5 days is less than 0.01 m; and the precision of monitoring of the ground subsidence is 0.001 m. A formula for calculating L is as follows:
where
A formula for calculating a ground subsidence amount at the monitoring point is as follows:
ΔH=He0−He, where
ΔH is a ground subsidence amount, in m; He0 is an initial ground elevation at the monitoring point, in m; and He is a ground elevation at the monitoring point during a mining process, in m.
S3. Plot variation relationship curves of drilling footage and phreatic water level as well as drilling footage and ground subsidence according to the working face drilling footage and the ground subsidence amount that are obtained in step S2 and water level monitoring information obtained in step S1.
S4. Compare the curve with a no-phreatic leakage graph, a slight-phreatic leakage graph, and a heavy-phreatic leakage graph; and classify a mined coal seam working face as a no-phreatic leakage area, a slight-phreatic leakage area, and a heavy-phreatic leakage area.
The foregoing no-phreatic leakage graph, slight-phreatic leakage graph, and heavy-phreatic leakage graph are rules generalized from the monitored information (working face drilling footage data, water level gauge data, and ground subsidence data) of a plurality of coal mines in northwest China, and a classification basis is a correspondence between ground subsidence and a water level.
As shown in
As shown in
As shown in
Stage 1 in all of the three basic graphs corresponds to stage a, indicating that the coal mining activity in front of the mining area leads to a decrease in the water level at the monitoring point. At this time, it cannot be determined whether the water level is lowered because of the foregoing phreatic leakage of the mining area or the lateral recharge caused by the ground subsidence. In
To better classify a phreatic leakage disaster level of a mining coal seam working face, the foregoing classifying method further includes the following step:
S5. Define the no-phreatic leakage area as an environmentally friendly area, define the heavy-phreatic leakage area as an environmental disaster area, calculate a water level buried depth of the slight-phreatic leakage area in step S4, if the water level buried depth is deeper than a local ecological water level buried depth, classify the mining coal seam working face as an environmental disaster area, and if the water level buried depth is shallower than the local ecological water level buried depth, classify the mining coal seam working face as an environmentally friendly area. A formula for calculating a water level buried depth of the slight-phreatic leakage area in step S4 is as follows:
S=He0−Hw, where
It should be noted that the ecological water level is a groundwater level buried depth capable of maintaining good development and growth of typical vegetation, and the ecological water level is determined according to typical ground cover vegetation of the coal mining area.
The technical solution of the present invention is described below in detail with reference to a specific example.
As shown in Table 1, an initial ground elevation He0 at the monitoring point is 1226.81; an average mining depth h of first mining nearby the monitoring point is 280 m, mining practice in the mining area has an advanced influence angle w of 62°, and an advanced influence distance L is calculated by using a formula
to obtain that L is 148.87 m. Therefore, when the drilling footage moves forward to 150 m in front of the monitoring point to start to monitor a ground subsidence amount at the monitoring point. Manual monitoring is performed at a monitoring frequency of 2 times/d, where monitoring time points are respectively 6:00 and 18:00. The monitored data of the ground elevation He at the monitoring point is shown in Table 1. As shown in Table 1, the ground subsidence amount ΔH is calculated by using a formula ΔH=He0−He. The data is shown in Table 1. On May 8, 2017, a drilling footage line exceeds the monitoring point by 300 m, and an accumulated ground subsidence amount continuously monitored in 5 days is less than 0.01 m, the ground subsidence becomes steady, and monitoring is stopped.
Variation relationship curves of drilling footage and phreatic water level as well as drilling footage and ground subsidence are drawn according to the monitored data of Table 1, as shown in
In addition, to further determine a phreatic leakage disaster level of the working face of the Jinjitan coal mine, a water level buried depth in a loss process is compared with a local ecological water level buried depth. A formula for calculating a water level buried depth in a loss process is:
S=He0−Hw, where
A value range for calculating the water level buried depth S is 0.91 to 2.33, as shown in Table 1. In addition, the Jinjitan coal mine is located on an edge of the Mu Us desert, and the ground cover vegetation is mainly Shaliu and Saussure. According to the previous researches and previously published articles, “Study on Ecological Safe Groundwater Level Buried Depth in Windy Beach Area of Northern Shaanxi” and “Division of Coal Mining Conditions Based on Ecological Water Level Protection for Northern Shaanxi”, it is determined that the local ecological water level buried depth is 3 m. Upon analysis, a calculated value of the water level buried depth S is less than the local ecological water level buried depth of 3 m. Further, the coal-mining working face of the Jinjitan coal mine is classified to be environmentally friendly. It can be seen that although the water level is slightly lowered in the mining process, vegetation would not be seriously affected.
In conclusion, in the present invention, a coal mining area is classified as a no-phreatic leakage area, a slight-phreatic leakage area, and a heavy-phreatic leakage area according to analysis on respective stages of ground subsidence amounts and monitored water level variations at an observation point and telemetering water, the coal mining area is classified into the no-phreatic leakage area, the slight-phreatic leakage area, and the heavy-phreatic leakage area; the calculated water level buried depth in the coal mining area loss process is compared with the local ecological water level buried depth, and the slight-phreatic leakage area is further classified as the environmentally friendly area and the environmental disaster area. The classifying method used in the present invention is simple and practical, where from a perspective of ecological protection, a water resource loss and an environmental disaster is determined for a shallow seam of a northwest coalfield, and a basis is provided for a choice of a mining manner in a mining area, and the method is of significance for ecological and environmental protection in a mining process of the northwest coalfield.
The descriptions above are merely specific preferred implementations of the present invention, and the protection scope of the present invention is not limited thereto. Any change or replacement that can be easily conceived of by a person skilled in the art within the scope of the technology disclosed by the present invention shall fall within the protection scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201810901441.7 | Aug 2018 | CN | national |
This application is the national phase entry of the International Application No. PCT/CN2019/073162, filed on Jan. 25, 2019, which is based upon and claimed priority to Chinese Patent Application No. 201810901441.7, filed on Aug. 9, 2018, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2019/073162 | 1/25/2019 | WO | 00 |
