With the improvement of China's economic level and the increase of resource exploitation demand, the scale and quantity of mining area construction in China have greatly increased. However, the mine owners do not pay attention to the detailed and professional exploration of hydrogeology in the mining area, and the geological exploration methods adopted also have certain disadvantages, which affect the exploration effect, and the mining area construction planning is blind and prone to mine accidents. Therefore, measures must be taken to improve it.
First, the problems existing in hydrogeological exploration in traditional mining areas
Traditionally, mine owners pay more attention to the distribution and trend of coal resources when they understand the natural and human environment of mining areas. Even if they made a report on hydrogeological exploration in the mining area, it was only superficial, not detailed and not in-depth. More is based on their own experience to analyze and evaluate the relevant situation of the mining area, and there is no actual and specific investigation. However, the selection of some hydrogeological exploration methods has great limitations. Mines are generally limited by karst confined water, and floor water inrush is a common phenomenon, and its reasons are various. The development and change of hydrological structure in karst fractures is the most critical factor affecting water inrush from bottom water. The properties and characteristics of layers and rocks that separate water from air affect the amount of bottom water flow protrusion; In the process of mining in the mining area, it may cause damage to the bottom, which may lead to water infiltration into the bottom; The structure of rock and soil in mining area and the development and change of cracks between rock and soil will affect the size of water flow; Water flow pressure, mine rock pressure and their interaction have great influence on bottom water inrush. Therefore, traditionally, hydrogeological exploration generally needs to understand the development and change law of hydrological structure in karst fractures, the nature and characteristics of water-gas separation layer, the structure of rock and soil in mining areas, the development and change of cracks between rock and soil, and the change and development law of water-bearing layer. Using this traditional hydrogeological exploration method, only one exploration method can be used at a time to find out the cause of water inrush, such as drilling holes from the ground, pumping water or injecting water. In this way, we can only detect the development and change of rock strata and the accumulated water flow in a certain area below the surface, as shown in figure 1, which shows the surface coverage of rock strata in a certain area and reflects the natural classification of rock strata in a certain area of the mining area. But it is impossible to detect the situation below the surface in a larger range. Moreover, because there are many reasons for water inrush at the bottom of the mining area, it is impossible to detect it with a unified hydrogeological exploration method. Moreover, the water inrush phenomenon at the bottom of each area may have different manifestations due to the changes of various factors. For example, if water inrush occurs at the bottom of the fault, then the composition and structure of karst play a major role, and the water inrush at the bottom has a great destructive impact, which is probably caused by changing the pressure when people are mining in the mining area. In hydrogeological exploration in mining area, it is necessary to effectively divide limestone aquifer and gas-water separation layer, and it is of great significance to find out the thickness and layers of limestone. On the one hand, we can find out the specific number of aquifers by effectively dividing limestone aquifers and layers separating air and water. In geological calculation, firstly, we should calculate the water quantity that can be extracted from borehole and the thickness of aquifer, and then substitute the obtained concrete values into a fixed formula to get a coefficient, and then use the value of this coefficient to calculate the water quantity that can be gushed out of the mine, so as to get scientific and effective exploration results; In addition, through the change and development law of aquifer, it can provide scientific basis for controlling hydrological environment. We can choose to adopt the way of "blocking" or "dredging" according to the specific change law, which requires detailed identification and summary of the change law of water content in vertical layer of limestone, and draw regular conclusions. However, it is very complicated to accurately measure the thickness and number of layers, and it faces many difficulties. Therefore, in traditional hydrogeological exploration, it is generally believed that the closer the vertical layer of limestone is to the surface, the more water it contains, which cannot adapt to the complex hydrogeological conditions in the mining area. Second, the methods to solve the problems existing in hydrogeological exploration in mining areas
(1) In order to effectively prevent the phenomenon of sudden bottom water flow, it is necessary to comprehensively observe and detect the causes of sudden bottom water flow, and effectively prevent and control possible problems. Various methods can be combined to carry out hydrogeological exploration in the mining area, and before planning and designing the mining area, the method of detecting earthquakes on the ground can be used. Find out the geological structure state and the development and change of fault plane in mining area, study the situation of coal resources in coal seam and the flat fluctuation at the bottom, and analyze the water-bearing surface situation that affects mining in combination with specific mining areas, so as to take scientific and reasonable water prevention measures and improve the accuracy and practicability of mining area planning and design. Of course, some small and medium-sized structures in hydrogeology need to be analyzed and explored at this stage. Small structures mainly include fault planes with a difference of about five meters between the highest point and the lowest point, cylinders for trap implementation, spatial layout of mining, etc. These must be arranged before planning and designing the mining area. At present, many advanced exploration methods can be used for layout. It is much more convenient to explore objects on the ground than in mines, and good results can be achieved in a short time. However, the way to explore ground objects is greatly influenced by the surface conditions. Irregular fluctuations may occur in a certain area and at a certain time in the mining area. The reasons for the fluctuations may be due to the surface, the reasons below the surface, and even the seabed and river bottom. At this time, we can use the method of in-depth detection of small fluctuations to analyze the reasons, so as to seek effective solutions in time. If we want to find out the water content under the mine in the mining area, we need to consider the natural environment and human environment around the mine, such as the structure that can divert water and the level of separation between air and water in the mining area, and then drill to a certain extent, so as to better carry out hydrological adjustment work such as diverting water and reducing mine pressure. At present, the general geological exploration methods are based on the physical properties of the earth's surface, and some basic exploration methods are adopted. Real-time dynamic monitoring of hydrogeological exploration in mining area by computer technology can not only analyze the recoverable geological conditions of coal seam in real time, but also predict the hydrogeological conditions in mining area in advance. If a series of techniques are used, such as changing the electromagnetic field instantly, predicting the possible situation by monitoring the three-dimensional shape of the earthquake, exploring objects in the mine, exploring objects on the ground and so on. It can well locate the fracture layer in the mining area, calculate the depth of rich coal seam, and analyze the development of karst fractures and gas-water separation layer. The information and data obtained through the above technologies are summarized to form a complete system, and the calculated results are formed after analysis, so that the hydrogeological information and data are more operable, so that the mining area staff can know the hydrogeological conditions and conditions in the mining area in detail, adjust and control the mining of mining resources scientifically and reasonably according to the specific conditions, and flexibly respond to various situations that may need to be faced with artificial or natural conditions. The complex hydrogeological conditions in the mining area have great influence on the mining work in the mining area. It is difficult to exclude the influence of complex geological conditions around the mining area and the development and change of fault planes by only one exploration method. It is also difficult to make good use of the structural change and development law of coal seam plane and adopt a combination of various methods to carry out hydrogeological exploration in mining areas, which can not only achieve good exploration results, but also ensure the efficient production of mines and the health and safety of mining personnel. (2) In order to find out the law of water content in limestone vertical plane, people traditionally adopt simple pumping test or electric power calculation method, but still can't draw a very effective conclusion. This is mainly because the calculation method adopted is not scientific and reasonable. For example, the study of karst cracks can only make clear the change and development of cracks, and it is easy to ignore the study of some easy-to-change areas. The data obtained and the water pressure test on the section have a good effect on understanding the water-bearing law of limestone vertical plane. The sectional water pressure test is more effective in relatively hard ore and rock. The concrete method is to inject water into the borehole with strong pressure, and then by observing the extent to which the injected water is absorbed by the ore and rock, we can know the hydrogeological situation below the mining area by using a certain formula. If it is observed that the better the injected water is absorbed by ores and rocks, it can be judged that the better the fracture development is, the smaller the change degree is. On the contrary, if it is observed that the injected water is poorly absorbed by ores and rocks, it can be judged that the development of fractures is not good enough and the degree of change is relatively large. Generally, a device for blocking the water flow is used in the segmented water pressure test to achieve the purpose of separating different levels of drilling holes. In this way, we can not only know the vertical fracture of ore and rock, but also know the absorption degree of water flow at different levels. In the process of water pressure, the bottom of the borehole can be reached under water pressure, and the upper end can be used to place a plug to stop the water flow. The distance between the upper end and the lower end is generally determined according to the size of cracks in karst, and the water blocking devices are generally the same. At the same time, the water content law of limestone vertical layer can be obtained effectively by using groundwater flow velocity measuring instrument. When pumping water from the hole drilled by the drill bit at a fixed time and flow rate, different flow rates at different levels can be measured by taking photos or measuring with instruments, and good results can be achieved. (3) Ensure the quality of personnel. However, in the process of hydrogeological exploration in mining areas, improving the quality of prospectors and making them explore within the scope of operating rules can improve exploration efficiency and obtain more comprehensive and accurate hydrogeological information and data, and ensure the quality of geological exploration by continuously strengthening their ability to analyze and use information and data for practical calculation and problem solving.
Thirdly, it is concluded that the hydrogeological exploration in the mining area is a complex project, which requires a combination of various methods to effectively divide the limestone aquifer and the layer that separates the air from the water flow. Then, through the efforts of the vast number of hydrogeological workers, the smooth hydrogeological exploration in the mining area is ensured and the safe production in the mining area is maintained.
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