I. Strata

The exposed strata in the mining area are: Middle Permian Maokou Formation (P2m), Upper Permian Longtan Formation (P3l), Changxing Formation (P3c), Lower Triassic Yelang Formation (T 1y) and Quaternary System (q). The lithology of each layer from new to old is described as follows:

1, quaternary (q)

Mainly residual slope soil layer. The lithology is brownish yellow clay and sandy clay, with uneven distribution of gravel and rubble, and loose structure. The thickness is 0 ~ 6m, and it is scattered in depressions and gentle slopes. In unconformity contact with the underlying stratum.

2. Lower Triassic Yelang Formation (T 1y)

Only t 1Y 1Y2 in Shabaowan section and T 1y2 in Yulongshan section are exposed in this group, which are briefly described as follows:

Shabaowan section (T 1y 1): yellow-gray calcareous mudstone, about 3-8m thick, mixed with thin argillaceous limestone. It is in integral contact with the underlying stratum (P3c).

Yulongshan section (T 1y2): gray, light gray, thin-to-thick layered limestone, aphanitic, fine-grained structure, with purple and dark gray argillaceous bands locally and bioclastic limestone at the top. The limestone in the lower part contains heavy mud, with a thickness of about 240-280m.

3. Upper Permian Changxing Formation (P3c)

Gray, dark gray medium-thick layered to thick layered fine-grained to medium-grained limestone, and flint nodules, lumps and bands can be seen intermittently in limestone. A large number of marine fossils of larger individuals are in contact with the underlying stratum (P3l) as a whole. The thickness is about 38-43m, generally about 40m.

4. Upper Permian Longtan Formation (P3l)

Gray and dark gray fine sandstone, siltstone, mudstone, marl, coal limestone, siderite limestone, etc. The bottom is clay rock containing pyrite. This layer is a coal-bearing stratum in this area, rich in pteridophyte fossils and brachiopod fossils. The thickness is about 60-70m. It is in false conformity contact with the underlying stratum.

5. Middle Permian Maokou Formation (P2m)

Light gray, medium-thick gray to thick layered fine-grained limestone produces abundant brachiopod and Odonata fossils. Exposed in the northwest of the mining area. Thickness is greater than 100 m.

Second, the geological structure

Located in the east wing of Ande anticline, near the north end. The formation is monoclinic with dip angle of 85 ~ 100 and dip angle of 9 ~ 10, generally 7. Faults are not developed in this area. According to the investigation of coal mining roadway, in the process of coal mining, some small faults were found locally, ranging from several meters to tens of meters in length and with a fault distance of 3 ~ 8 meters, which did little damage to the continuity of coal seam.

According to the results of peripheral data and the situation of the mining area, it is determined that the complexity of geological structure is medium.

Three. hydrogeological condition

1, characteristics of aquifer and aquifer and their relationship with water filling of deposit.

Quaternary (Q) porous aquifer: it is distributed sporadically in depressions and gentle slopes, mainly in eluvial layers. The lithology is brownish yellow clay and sandy clay, with uneven distribution of gravel and rubble, and loose structure. The thickness is 0 ~ 6m, generally about 3.5m This layer has good water permeability, poor water-rich property and weak water-rich property.

Water-resisting layer (T 1y3) in the 9th beach section of Yelang Formation of Lower Triassic: exposed in the eastern periphery of the mining area, with light purple, purplish red and gray thin mudstone in the upper part and gray limestone in the middle and upper part. It is distributed in the northeast of the mining area, with incomplete exposure and a thickness of more than 200m m.

Karst fracture aquifer of Lower Triassic Yelang Formation (T 1y2) and Upper Permian Changxing Formation (P3c): The lithology and water abundance of Yulongshan Formation and Changxing Formation are similar, only Shabaowan Formation (T 1y 1) is 3-8m thick, and the two layers are separated, and the lithology is light green calcareous mudstone. T 1y 1 is easy to deform and destroy under the roof damage of goaf, and loses its waterproof property. Therefore, Yulong Mountain and Changxing are combined into one layer to study, and the two layers are collectively called "T 1y2+P3c" karst fissure aquifer.

Yulongshan section (T 1y2): exposed in the east of the mining area, the lithology is mainly gray, light gray thin-thick layered limestone, with aphanitic and fine-grained structure, with purple and dark gray argillaceous bands locally and bioclastic limestone at the top, with a thickness of about 240-280m.

Upper Permian Changxing Formation (P3c): gray, dark gray medium-thick layered to thick layered fine-grained to medium-grained limestone, with flint nodules, lumps and bands intermittently visible in the limestone, with a thickness of 40m.

"T 1y2+P3c" stratum is moderately water-rich, distributed in most areas in the east of the mining area, with well-developed joints and fractures. There are four spring points S 1, S2, S3 and S4 in the west of the mining area, and the water inflow is 1.50, 0.53 and 0.83 respectively. T 1y2+P3c is the main aquifer in this area. At that time, the groundwater in "T 1y2+P3c" layer will enter the mine through the water-conducting fracture zone and caving zone, which will have an impact on the water filling of the deposit.

Fracture aquifer of Upper Permian Longtan Formation (P3l): It is composed of gray and dark gray fine sandstone, siltstone, mudstone, marl, coal, limestone and siderite limestone with a thickness of about 40m. There are no springs in this area. This layer is generally weak in water-abundance, and can be regarded as a water-resisting layer. Coal-bearing rock series generally constitute the direct water-filled aquifer of the deposit. In the later mining process, groundwater can directly enter the mine to fill the deposit.

Middle Permian Maokou Formation (P2m) karst fissure aquifer

It is mainly dark gray fine-grained limestone, with a thickness of > > 100m. This layer has developed surface karst, good recharge conditions, strong water abundance and extremely uneven water content. In the later mining process, groundwater is likely to break through this water-resisting layer and enter the mine, which is also harmful. Therefore, this layer is designated as the main direct water-filled aquifer in the lower part of the deposit in this mining area.

2. Influence of structural faults on water filling of the deposit.

Faults in mine field boundary are undeveloped, which has little influence on coal seam water filling.

3. Surface water and its influence on the water filling of the deposit.

There is no surface water body in the mining area, and seasonal gully has little effect on the water filling of the deposit.

4. Hydrogeological conditions of production roadway and old kiln

According to the collected data: According to the original production situation of Yunfeng Coal Mine, the normal water inflow of the mine is QB =15.0m3/h; Maximum water inflow: qmax = 22.0m3/h, and the surrounding mining adits (LD 1, LD2) are all inclined shafts, with certain water accumulation, which has certain influence on coal seam mining. The water inflow is closely related to atmospheric precipitation, and the water mainly comes from the seepage of coal seam roof and the accumulated water in goaf.

According to the investigation, there are a large number of mined-out areas or old kilns in the mining area. Because the coal-bearing rock series has good water resistance and water storage, a large amount of old kiln water may be stored in the old adit, which should be paid attention to when mining.

5. Analysis of water filling factors

Atmospheric precipitation: part of the atmospheric precipitation in the area flows into the gully through the gully, and part of it supplies groundwater. In rainy season, atmospheric precipitation may gather in depressions, which has certain influence on coal seam mining. Atmospheric precipitation is the main source of groundwater in various rock groups in the mining area. When the goaf caving and the resulting water-conducting fracture zone develop to the surface, atmospheric precipitation can indirectly enter the mine in this way.

Groundwater: Although the water content of coal-bearing rock series is weak, the groundwater in it will directly enter the mine pit. P2c+T 1y2 is widely distributed in the mining area, and its water abundance is moderate to strong. Groundwater may enter the mine through the subsidence zone and water-conducting fracture zone, which has certain influence on the mining of C5 and C8 coal seams. The distance between C8 coal seam and top boundary of P2m limestone is10.0 ~15.0m.. If the floor is damaged, groundwater may enter the mine and cause water filling.

Old kiln water: The old mined-out area left by mining C5 and C8 coal seams in the mining area is large, and the old kiln water is the biggest threat in the future mining process. In the mining area, the outcrop line of each coal seam is mined from south to north for a long time and there are many old adits. Due to the closure for many years, there is water in the pit. Part of the water in the pit comes from atmospheric precipitation, and part comes from the accumulation of groundwater in rock strata for many years. It is difficult to estimate the quantity. The owner should pay attention to the water inrush accident caused by the water in the old adit during mining.

Hydrogeological exploration types of the deposit: P2c, T 1y2 karst fissure aquifer and Laoyao water are mainly used to fill the deposit. According to the classification standard of the current code, the hydrogeological exploration type is defined as the second subcategory of the first and second subcategories of the third category, that is, karst water-filled deposits with large water inflow from the roof and floor and medium hydrogeological conditions.

Engineering geological conditions are still lacking. Source: www.lw372 1.com