Open-pit joint mining of Pingshuo coalfield and Anjialing mine

2.5.4. 1 Overview of Pingshuo Coalfield

Pingshuo mining area is located in Shuozhou City, Shanxi Province, belonging to the northern part of Ningwu coalfield. Pingshuo mining area is an important production base of 100 million tons of coal in China. Pingshuo Coal Industry Company has successively built Antaibao Open-pit Mine, Anjialing Open-pit Mine and East Open-pit Mine. In recent years, in order to increase the coal output and reduce the waste of coal resources, a new safe and efficient open-pit combined mining mode of shallow-buried, extra-thick and near-horizontal coal seam has been tried for the first time, which has formed a unique open-pit combined mining mode of China Coal Pingshuo Company and achieved considerable economic benefits.

Pingshuo mining area is bounded by coal seam outcrop line in the east, west and north, and danshuigou fault in the south. The length from north to south is about 2 1km, the width from east to west is about 22km, the area is 380km2, and the geological reserves are127.5 billion t. According to the reply of Shanxi Pingshuo mining area project proposal No.360 [1993] issued by the State Planning Commission, the Antaibao mine joint venture area, Anjialing and Antaibao No.2 between Maguan River and Qilihe River are explored. The survey area to the east of Maguan River is 46km2, with geological reserves of 65,438+176.3km2 and 61400,000 t, which is a national large-scale open-pit mining area. The remaining 204km2 and geological reserves of 661000,000 t are local and township coal mining areas. See Figure 2- 14 for the division of resources. The mining area belongs to the typical open-pit combined mining type and is suitable for open-pit coal mining.

Figure 2- 14 Schematic Diagram of Resource Division in Pingshuo Mining Area

Open-pit combined mining of Anjialing mine in Pingshuo, 2.5.4.2

(1) ore field and stratigraphic structure

Anjialing open-pit mine, including Anjialing and Antaibao No.2 exploration areas, is located in the south-central part of Pingshuo mining area, and its administrative area belongs to Pinglu District, Shuozhou City, Shanxi Province. Its geographical coordinates are11217' ~11226' and 39 24' north latitude. West to the flood level line on the west bank of Qilihe River and the mining boundary of Antaibao open pit mine. In the south, the connection line between Cave 843 and Cave 1 10. Borehole T58 is the exploration boundary in the south, and the exploration line 12 of No.2 exploration area in Antaibao in the north is connected with Pingfan Chengxi survey area. It is about 8.5 kilometers long from north to south and 8 kilometers wide from east to west, with a total exploration area of 59.8 square kilometers and geological reserves of 265,438+88 million tons.

Anjialing open-pit coal mine is a key construction project in the coal industry during the Ninth Five-Year Plan period, and it is also a large-scale modern coal project designed, constructed and managed by China itself, realizing a new coal production mode of open-pit mining. The actual production capacity of raw coal is 30 million tons, which is one of the largest and most modern coal production bases in China.

Figure 2- 15 shows Anjialing open pit mine in Pingshuo.

Figure 2- 15 Anjialing open pit mine in Pingshuo

The strata in Anjialing mining area are composed of Quaternary, Neogene Pliocene, Permian Shihezi Formation, Lower Permian Shanxi Formation, Carboniferous Taiyuan Formation and Carboniferous benxi formation from top to bottom. According to the different properties of soil and rock, they are described as follows: ① Quaternary strata are mainly loess layers, which can be divided into upper and lower layers. The viscosity of the upper loess is very low, and the lower loess contains gravel. It is classified as Grade I non-gravity collapsible loess in geological exploration report, which is extremely unfavorable to engineering construction and will cause great deformation when it meets water under normal pressure. ② Neogene Pliocene interbedded with brownish red clay and loam, with small thickness and scattered distribution in the mining area. It is a kind of weak layer which is easy to deform and reduce its strength when it meets water. If it happens at the base of the dump, it will affect the stability of the dump. (3) The coal measures strata are characterized by hard lithology and dense cementation, except shale, the hardness coefficient is above 4, and the occurrence of slope strata is gentle. The roof of No.4 coal seam is grayish white medium-coarse sandstone, with gravel sandstone locally, hard rock and dense cementation; The roof of 9# coal seam is sandy mudstone, and some are mudstone and carbonaceous mudstone, of which sandy mudstone is hard and mudstone and carbonaceous mudstone are slightly weak.

The structure of the mine field is mainly controlled by Ningwu syncline, Luzigou anticline, Baijiaxinyao syncline and Poole anticline, and the stratum occurrence is relatively gentle, except that the east wing of Luzigou anticline is steep (15 ~ 25), generally below 10. Ningwu syncline, the main fold in the mine field, is located in the east, with the axial direction of NW30, and its secondary levels are all developed in the west, roughly parallel to NE45, and the scale decreases from southeast to northwest. Faults and collapse columns are developed in the mine field, except for a few faults (such as Anjialing reverse fault and Matigou fault), which are generally below 15m. The fault strike is divided into three groups, namely NE, NNE and NNW, with NE as the main strike. Karst collapse columns are unevenly distributed and have different sizes. According to the drilling and 3D seismic results, there is no magmatic activity in this area, which belongs to moderately complex structure, as shown in Figure 2- 16.

The distribution and extension of structures not only provide spatial conditions for the occurrence and migration of groundwater, but also control the recharge, runoff and discharge conditions of groundwater. The west side of Ningwu syncline is Luzigou anticline, which is 50 NW in the east of Erjingtian, turns to NNW at Luzigou, and turns to NNW after extending to Anjialing in the south. The buried depth of limestone is shallow, karst fractures are developed, and runoff conditions are good, forming the Qilihe runoff zone with alternating active groundwater. Most of the mine fields are located in the north of the strong runoff area, close to the recharge area.

Figure 2- 16 Structure Outline of Mine Field

(2) Open pit mining

Anjialing Open-pit Mine adopts single bucket truck technology, and advances from west to east with an annual advancing degree of 350m m. After the fourth year of production, the advancing direction changes from south to north, and there are transportation passages on both sides of the side wall, one for every other platform.

The end slope loess transportation platform is 34m wide and the safety platform is 6m wide. The rock transport platform is 32m wide and the safety platform is 4m wide. The slope angle at the end of the mine field is 34, and the existence time is 4 ~ 5 years.

The dump outside the upper kiln is strip-shaped, which is divided into east and west parts by a belt conveyor corridor. The maximum dumping elevation is 140m, the maximum dumping elevation on the east side is 1455m, and the maximum dumping elevation on the west side is 1430m.

Anjialing open pit mine is located in the north of the dump, railway loop, assembly yard, machine repair workshop and material warehouse are located in the southwest of the dump, and Jessie Village, Dongjie Village, Lianhe Coal Mine and Dongjie Coal Mine are located in the south of the dump, and high-voltage overhead lines pass through them. Therefore, the stability and safety of the upper kiln dump slope is directly related to the safety of these industrial facilities, civil buildings and related personnel.

Internal drainage develops from bottom to top. After the steps are formed, it advances synchronously with the coal mining face, and all internal drainage is realized in the fifth year of production.

The open pit mine is 9.5km long from north to south, 5.3km wide from east to west, and the slope height is about 20 m.

(3) Underground mining

Anjialing mine is located in the north and south sides of Anjialing mine pit, which consists of open-pit non-mining area, shangyao area and Taixi area. The occurrence of strata in this area is gentle, and the dip angle is generally 2 ~ 5, and the local dip angle is about 65438+02. The main mining areas in the mine field are 4- 1 # coal, 4-2 # coal, 9 # coal and 1 1 # coal. The main coal seams have stable occurrence and simple structure, among which the buried depth of No.4 coal is 70.82. The coal quality is hard, containing 3 ~ 5 layers of gangue, and the lithology is mostly mudstone or sandy mudstone. The structure of No.9 coal is complex, and the gangue is mostly sandy mudstone and carbonaceous mudstone, with local kaolinite and siltstone.

Figure 2- 17 shows the location of the mine field in the mining area.

Figure 2- 17 mining field location

Mining method is inclined longwall fully mechanized caving mining method. The working face length is 240m, the mining height is 3.2m, the first caving step of top coal is 16m, the first caving step of direct roof is 34m, the first weighting step of main roof is 44 ~ 45m, the periodic weighting step is 12 ~ 18m, and the dynamic load coefficient is/kloc-0. The support mode of the working face is hydraulic two-column shield type. The mine is a central parallel ventilation system, which adopts the extraction ventilation mode, that is, the main inclined shaft, the auxiliary inclined shaft and the return inclined shaft. The air shaft is equipped with two counter-rotating motors and two supporting motors, one for operation and the other for standby.

(4) Open-pit combined mining

Anjialing open-pit coal mine was originally designed as a single open-pit mining mode. In 2002, China National Coal Industry Import and Export Corporation sent a letter to the State Planning Commission "Request for Instructions on Changing Anjialing Open-pit Coal Mine Project from Single Open-pit Development Mode to Open-pit Combined Development Mode" (Zhongmeibanzi [2002] 16, approved by the State Plan, and based on [2002] 1478 of the Planning Commission) for coal blending.

The designed output per unit area is 100 mt/a, the calculated service life is 103.5 years, and the service life of the first mining area is 23.6 years.

The mining sequence is: mining the first mining area first, and advancing eastward. After 7 years of production, it began to turn into a fan, and then gradually transitioned to the north until the final border was in the north; Before the end of the first mining area, gently slope on the north side of the east, transition to the north of the second mining area, push eastward to the east boundary, gently slope again, and transition to the southwest boundary until the west boundary; Finally, mine the third mining area until the final state in the north.

In order to ensure the safety of ground structures, engineering facilities and underground mining, safety pillar is reserved for shafts, alleys, industrial sites, railways, highways and other important facilities. According to the relevant regulations. After calculation, there is a security pillar not less than 300m away from the floor steps of 4# coal seam at the southern end of the open pit mine. Antaibao Open-pit Coal Mine, southwest of the dump, the loop of the outbound railway loading line reached the collapse edge, leaving a safety pillar of not less than 150m; There are no less than 170m safety pillar in the industrial site of open-pit coal mines and Jiexi village from the south slope to the edge of the subsidence area, and corresponding engineering measures have been taken for the ring road, high-voltage power supply line and ring road in the subsidence area to ensure the normal, efficient and safe joint mining of open-pit workers. It can be seen that the combined mining of open-pit workers in Anjialing open-pit mine is a typical type of underground mining in dump and residual coal mining at boundary. See fig. 2- 18 for the location of open pit workers.

Figure 2- 18 Open-pit combined mining position and typical profile position