The total water inflow of 10 production mines in the world is 398m3/min (1981August), excluding the flooded Yanmazhuang mine (water volume is 123m3/min) and local mines.
The mine water inflow is related to the hydrogeological boundary conditions of the deposit, the degree of structural fragmentation, the mining coal seam, the mining depth and the mining time. The water inflow of each mine varies greatly, ranging from 3.5 to 123m3/min. Generally, the change of water inflow can be divided into the following three stages.
(1) well construction time
Borehole water and Permian sandstone fractures are mainly excavated in the shaft, in which alluvial water inflow can reach 1.6m 3/min and sandstone water inflow can reach 1 ~ 2 m3/min. After shaft grouting treatment, the general residual water is 1 m3/min. When digging the bottom hole, the water volume is 2 ~ 3m3/min. During the well construction period, the mine drainage and waterproof ability is small, the area is small and the disaster prevention ability is weak. Therefore, the location of the shaft is selected in the weak water-bearing strata, avoiding quicksand layer, faults and limestone water inrush to ensure normal construction. At the same time, reliable drainage and waterproof ability must be established to consolidate the underground production position. Zhongmacun Mine is located on the fault zone. In the case of insufficient waterproof ability, the temporary water bunker roadway is opened to a place only 6 m away from the "eight ashes" and bears a water pressure of 25.9kg/cm2. Results Water inrush occurred at the speed of 1.05 m3/min, resulting in well kick accident.
(2) the initial stage of development
In this area, the distance between big coal and eight ash is 20 ~ 40m, the water pressure is 20 ~ 30kg/cm2, and the water pressure per meter of rock pillar is 0.5 ~ 1.5kg/cm2, most of which are in the situation of water inrush. Therefore, it is necessary to drain water to reduce the water pressure of the eight-ash aquifer and reach the safe water head value. With the excavation of roadway, the eight-ash aquifer is directly exposed, and the fault eight-ash water gushes out. The mine water inflow is mainly eight ash water, and the water amount reaches 30 ~ 80m3/min, which greatly reduces the water level. In some areas, the interval between big coal and eight ash is thick and the structure is simple. Using the water-resisting layer can protect the mine from long-term water inflow (below 5m3/min).
(3) Late stage of mining
In the later stage of mining, the hydrogeological conditions are more complicated because it extends to mine field boundary or horizontally to the Carboniferous "second coal" mining, which is characterized by:
1) into the complex structural area. When crossing the fault, "L2" or O2 water inrush occurs strongly, such as1301kloc-0/working face water inrush 103m3/min, and Wangfeng mine 1 17 area water inrush/min.
2) When mining the second level, the water quantity of the first level shifts to the deep. For example, the water inflow in the west of Yanma Mine is 54 ~ 66 m3/min, and the water output in the second level development is 40m3/min, which is 65% lower than that in the first level.
3) The water inrush point deviates to the direction of water supply. For example, the F3 fault in Yanma Mine is the water supply source, and the water inflow of the working face is19610115m3/min; F3 fault tip,1September 1964,1212/working face water inrush 89m3/min,10/working face water disappeared. 1966, 65438+the water yield of west alleys in February is 58m3/min,1212/the water yield of working face is reduced to 22m3/min. On August 4th, 1977, 144 1 face directly encountered F3 fault, and water burst 120m3/min. The water quantity of the above water inrush points is greatly reduced, and the water inrush points continue to develop to F3 fault, and the new water inrush points and old water inrush points are reduced.
4) When mining the second lump of coal, the mine water inflow will increase by 30 ~ 50m3/min. At this time, the water from L5 and L2 aquifers directly flows into the mine, and the water levels of these two aquifers also drop obviously.
In addition to the above-mentioned changing trends related to mining conditions, the mine water inflow dynamics also have the following characteristics: ① The seasonal variation of water inflow dynamics is small, with the annual variation range of 1.05 ~ 1.3 times; (2) The change of water quantity is obviously influenced by the fluctuation of water inrush, and it increases step by step. After the water quantity jumps, it is generally fast and stable; ③ The general trend of water quantity is increasing; (4) Under the condition of not exposing new water sources, the water inrush point will increase or shift, but the total water volume will remain unchanged.
The above characteristics show that the groundwater recharge source in this area is rich, and the water quantity has the function of fully regulating and balancing, which is in a dynamic and stable state and is not easy to be lost.
2. Boundary characteristics of mine water inrush
Mine water inflow mainly depends on the water inflow boundary conditions of the deposit. According to the hydrogeological characteristics of Jiaozuo mining area, there are three kinds of water inflow boundary conditions in the mine field:
1) Strong recharge boundary, that is, horizontal or vertical direction, with strong aquifer recharge (aquifer gravel layer and karst limestone). The aquifer receiving recharge is also a strong aquifer. For example, the outcrop of shallow coal seam in Yanmazhuang Mine is covered by water-bearing gravel layer, in which Ordovician limestone and Carboniferous limestone layer contact with gravel layer, and the water level tends to be consistent. After the mine drainage, the water level will be replenished with high head, and the hydraulic connection is close. At the same time, there is a NE-trending F3 fault zone in the deep part, and the eight ash and two ash are hydraulically connected with the Ordovician limestone, resulting in frequent water inrush and large water quantity, resulting in Yanmazhuang Mine 20.
2) Weak recharge boundary, that is, contact with weak aquifer or water-resisting boundary in horizontal and vertical directions. For example, the outcrop of Tianmenjing coal seam is covered by alluvium, and there is no water. The coal seam floor has a complete water-resisting layer of 40m, and the two plates of deep faults are the water-resisting boundaries of coal measures strata contact, and the mine water inflow is 4 ~ 5m3/min.
3) Local strong recharge boundary, that is, mine field boundary has strong aquifer recharge along the horizontal or vertical direction, but the water content of recharge aquifer is weak, which is not conducive to groundwater recharge. For example, in Ma Zhong mining area, the main source of groundwater recharge is a part of the shallow Lee Ha fault, and the deep Jiulishan fault has a large drop (300m), so the Ordovician limestone is in contact with the coal measures. Deep limestone fractures are small and do not form a strong recharge boundary. After mine drainage, the water level difference between the two plates of Jiulishan fault is more than 200 meters, and the mine water inflow is 80 ~ 40 m3/min.
3. Mine water inrush characteristics
Mine water inrush is the most prominent problem in the hydrogeology of this coalfield deposit, which threatens the safe production of the mine. According to incomplete statistics (table 1-7), there were 707 water inrush accidents as of 198 1 * *, of which 5 1% was water inrush greater than 1m3/min, and 13 was water inrush greater than 30. The outburst level is 20 ~ 30 times a year. Generally, in years with high footage (such as 1958, 1962 ~ 1965, 1977 ~ 1978), there are more water inrush times, with 30 ~ 40 times a year. After 1973, the frequency and intensity of water inrush increased due to the development and horizontal extension of Carboniferous second coal.
Table 1-7 Classification Statistics of Water Inrush
The water inrush source is mainly the "eight ashes" of large coal floor, and the water inrush is 253 times, accounting for 36%. Water inrush from roof sandstone and shaft alluvium accounts for 40%, and the water inrush is small. The water in boreholes and small coal mines accounts for 13%. Water inrush from the floor of large coal seam is eight ash water 20 ~ 40m away from the large coal seam, which breaks through the floor through the rock fracture zone and is induced by mining.
Precursory characteristics of (1) water inrush
Generally speaking, the water inrush process is a precursor, which can be summarized as follows: ① Floor heave, such as -65438+2~3m temporary water storage in Zhongmacun Mine, suddenly heard a "shout" at 7: 00 on March 27th, and the floor heave was about 1m away from the working face, and water gushed out, with an inflow of 0.67m3/min and 65438. (2) The working face is wet and drenched with water, such as the second track of Mazhuang Mine (1),1March 8, 979, and the strata are found to be soft; On March 9 14: 30, two pieces of palm-sized water were found on the working face. 14: 45, there was a splash on the rock wall. The water inflow at 15 is 138m3/min and 15 respectively. (3) The working face is cold, such as Mazhuang Coal Mine 144 1 working face, 1977, and the water inrush on August 20th was 120m3/min, and the workers felt cold after working before the water inrush 1 ~ 2 days. In addition, the phenomena of ground pressure increase, broken beam, broken column, spalling, increased fracture density, red rust on fracture surface, change of rock occurrence, fault and sudden drop of gas content in coal seam are also precursors of water production.
The mechanism of floor water inrush is that the thickness of floor water-resisting layer is closely related to water pressure, and ground pressure is the fuse. The empirical value of critical water inrush coefficient (the ratio of water pressure to the thickness of water-resisting layer) in Jiaozuo mining area is 0.5 (mostly fault fracture zone). Floor water inrush is a kind of release of water level energy, and the change of water inflow is related to the structure of water inrush stratum, which can be divided into three categories:
The first category: strong water inrush type. When water inrush occurs, the water quantity quickly reaches the maximum value, and then decreases steadily, mostly in hard strata, close to the water source and located in the fault zone. For example, Mazhuang Mine 1 track water inrush case shows that the precursor of water inrush (drenching water) suddenly increases to 240m3/min after about 20 ~ 30 minutes.
The second category: jumping type. The water volume suddenly changes from small to large, and the frequency and intensity are getting bigger and bigger, mostly in the fault zone, a little far from the water source, and the water channel is enlarged. For example, in Fengying Coal Mine 130 1 1 working face, water production starts at 1m3/min, and increases to15 ~ 85m3/min one day later; After another 30 hours, it suddenly increased to more than 89m3/min, causing floods. This kind of water is very dangerous and begins to paralyze people, so we come to the conclusion that "if you are not afraid of being big, you are afraid of jumping".
The third category: slow type. When the aquifer is excavated or the floor strata are generally broken, the water quantity gradually increases with the exposed area, and then extends to the boundary with the influence radius to achieve water stability or gradually decreases and discharges due to insufficient recharge conditions. For example, Wangfeng Mine 1 17 is a floor fracture zone, and there is a large area of water, like boiling water tumbling, and the water volume is kept at 15m3/min.
The maximum water inrush includes moving water and partial still water. According to the measured data in this mining area, the stable water volume is 50% ~ 70% of the maximum water volume, and some of them reach 80%.
(2) Spatial characteristics of water inrush point distribution
The spatial distribution of water inrush points has certain rules, and water inrush points, water inrush zones and water inrush areas are often related to the distribution of faults (especially tensile faults). This area can be divided into the following types:
1) Fracture-intensive zone along the axis of anticline. There are gentle wavy folds in the coal seam strike (N60°E) in this area, and an anticline axis appears at a distance of about 4 ~ 5 km. There are many small structures and high fracture density in this area, and water inrush often occurs. Such as Wangfeng Coal Mine, Ma Cunjing Coal Mine and the western part of Yanma Coal Mine.
2) NW-trending tensile fracture zone. The NW-trending tensional fracture zone is often a small graben, which is arranged in parallel at equal intervals, with a spacing of about 600 ~ 800 m, and often has a group of water inrush zones. For example, the water inrush points in the second coal mine of Jiaoxi Mine are distributed in this tensional fracture zone, and water inrush is frequent.
3) Transverse tensile fracture zone along the strike of coal seam. For example, a group of water inrush points in the second coal mine area of Lifeng Coal Mine are distributed at 60 E north latitude, and the west side of them is a tensile fault at 60 E north latitude ... We choose grouting to block water at the intersection of water inrush points and small anticline, and soon the whole face will be blocked.
4) Small V-shaped fracture near the big fault. Water inrush points often appear in pipe strings. For example, there are four parallel and equidistant zigzag faults (about 120m) on the northeast side of Fenghuangling fault in Jizhazhang No.2 coal area of Lifeng Mine, and water inrush points appear in groups on both sides of the faults.
5) The area where two large faults twist each other, that is, the torsion fracture zone. For example, the Lihe fault in the southwest section of Zhongmacun Mine rises north and falls south, while the Lizhuang fault in the east section rises north and rises south, forming a twisted state, which makes the small structures in this area dense, water inrush frequent and groundwater difficult to drain.
6) Fault intersection. For example, the F3 fault in the west of Yanmazhuang Mine is the intersection of a NE-trending fault and three EW-trending small faults, and there are water inrush points in the intersection area, which are1441120m3/min, 57m3/min and12/kloc-0 in the west lane.
7) Fault tip extinction zone. For example, in Yanmazhuang Mine 10 1 working face, the water inrush point is located at the tip of F4 fault, and the water inflow is 15m3/min.
8) The upper wall (movable plate) of the normal fault. Most water inrush occurs in this area, such as Feng Ying 130 1 water inrush of 84m3/min.
In a word, the distribution of water inrush points is related to fault lines. In the areas with dense tectonic lines and rich tectonic water areas, the points, lines and surfaces of water inrush are regularly combined.
The migration of water inrush points is very common, and its law is that after the emergence of new water inrush points, the water volume of old water inrush points decreases or disappears. Another important feature is that the water inrush point deviates from the direction of water supply source. For example, a horizontal water inrush point in Yanmazhuang Mine is distributed near F3 fault, and the water inrush point is close to the water source from far and near (101:15m3/min; 89 cubic meters per minute; The water outlet is at 12 12; 53 cubic meters per minute; Water is discharged from the west alley; 144 1 point effluent 120m3/min), which is closely related to the hydraulic power of each water point. After the new water inrush point comes out, the water quantity of the old water inrush point is obviously reduced, indicating that the water supply source is the same until F3 is exposed as a vertical water supply channel. At present, through fault grouting, the total water inflow of the mine is reduced from 90m3/min to 7 1 m3/min, which confirms the judgment that the water outlet point moves to the water source.