Inclined shaft; Goaf; Steel frame shed
1 mine profile
Shanxi Jinmei Group Yangcheng Jinsheng Gulong Coal Industry is a gas mine, which is formed by the integration of three original mines: Shanxi Yangcheng Goudong Coal Industry, Shanxi Yangcheng North Extension Coal Industry and Shanxi Yangcheng South Gulong Coal Industry. Located in Gulong Township, northwest of Yangcheng County 15km, the mine mainly mines 3# and 15# coal seams. The construction plan is to mine 654.38+200,000 tons annually to serve the mine design. This mine uses the original coal industrial site in Gudong as the main industrial site of the integrated mine, and uses the original main shaft in the site to be transformed into a return air shaft, and newly digs the main and auxiliary inclined shafts. All three shafts fall to the floor of 15# coal seam at one time, with two inclined shafts and one vertical shaft, and the inclined shaft is developed.
The inclined length of the auxiliary inclined shaft is 565438+600mm (bottom 15# coal seam +620 level), and the inclination angle is 23. The design section is a straight wall semi-circular arch with a clear width of 4.5m and a clear height of 3.85m The clear section is 15. 15m2, and the track type is 30kg/m. The topsoil section of the shaft is concreted with a thickness of 500mm, and the bedrock section is supported with anchor net shotcrete with a thickness of 150mm, which is conventional.
The area where the shaft passes belongs to the old mining area of Yuangoudong Coal Mine in 2005. The original mining was basically to arrange the roadway along the coal seam, and the old room and pillar mining method was adopted. The heading azimuth of the working face entering the return air roadway is 2 1 1.5, and the interval is 20m. During mining, a connecting roadway is drilled every 40m, with a width of 3m, and the width of mined-out area after mining is about 9m, leaving 65,438+for two adjacent working faces. The auxiliary inclined shaft reveals that 3# coal seam is located at the western boundary of goaf. According to the geological survey, the mined-out area is 58723m2, and the shaft passes through the mined-out area of No.3 coal seam at high altitude, so there is no large area of water in the area, and the harmful gases are mainly CH4 and CO2, and there is no fire zone.
2. The goaf drainage scheme
In the process of shaft construction, we always adhere to the principle of "digging must explore, mining must explore, digging must explore and mining must explore". Firstly, geophysical exploration is used to explore the goaf in the mine field, determine the specific goaf position near the goaf and wellbore, determine the flooded area, calculate the accumulated water, and analyze the threat degree of water disaster. Then drill holes in the ground, install drainage equipment, and drain the water from the goaf.
When the shaft reaches 180m, stop the excavation, conduct advance drilling to check the goaf situation of No.3 coal seam, find out the goaf situation, eliminate stagnant water, and start the excavation after the concentration of harmful gas is reduced to a safe range. There are 17 boreholes in the shaft face. The arrangement, number and included angle of drilling holes are shown in figure 1.
3. Excavation and support scheme for crossing goaf
Short excavation shall be carried out 5m away from the mined-out area, the circulation progress shall be controlled at 0.8m, the hole depth shall not exceed 1.3m, and ground blasting shall be carried out. Explore the eyes to find harmful gases and water. On the basis of the original roadway anchor net support, 29U steel shed was erected, shotcrete support was carried out, stone wall was filled and shotcrete shaft wall was sprayed. The empty side and the roof part are supported by the steel frame backboard filled with concrete, flaky and wooden piles. Small section should be made during penetration. After the gas and water in the goaf are eliminated, the goaf will be exposed to the design section with a small gun or pneumatic pick.
Technological process: drilling and blasting → knocking on the roof to pry off the live gangue → temporary support of the front probe beam → laying the roof net (jacking anchor rod and anchor cable) → connecting the upper arch beam with the upper back plate or crib (filling rubble concrete) → pulling the tie rod of the arch beam → discharging slag → hanging the wall net (driving the upper anchor rod) → digging the foundation column nest → supporting the shed leg → installing the clamping cable to connect and reinforce → pulling the upper tie rod.
Roadway support in bedrock section of shaft: Left-handed reinforced anchor without longitudinal reinforcement is used as the anchor? 20-M22-2000, each row 13 anchor rods, the row spacing is 800mm, the spacing is 800 mm ... The anchoring agents are MSK2335 and MSZ2360, the φ 6.5 steel mesh is 2200×900mm, and the grid/kloc-0 ×100 mm. Anchor plate 120× 10 mm..C20 shotcrete, cement: p.o32.5, sand: yellow sand, crushed stone: 5 ~ 10 mm, accelerator: J85, sprayed layer thickness: 150 mm.
3. 1 normal section support mode
In the solid bedrock section 5m away from the mined-out area, a 29U steel shed is set up for initial support, with the shed spacing of 800mm, and the shed is connected with 10# channel steel tie rods, with 6 tie rods for each steel shed. After the steel shed, use1200 mm×150 mm× 50 mm wooden backboard for back fastening, and the spacing between backboards is not more than 600 mm ... The circulation method is excavation step by step, C20 concrete is sprayed every 3m, and the low places between the scaffolding are filled with initial setting concrete; After the shaft passes through 3# coal seam and goaf, the whole shaft shed section should be re-sprayed, which should meet the design requirements, and the thickness of spray layer and protective layer at the inner edge of U-shaped steel should be not less than 50 mm ..
The roadway is temporarily supported by front probe beam and hydraulic prop. Two steel pipes with a length of 2500mm and a diameter of φ 108mm are used for the front probe beam, which are fixed on the erected shed beam with 20mm steel clips. The model of hydraulic prop is DN22-300/90, and the prop should be supported by shoes and hats. After the roadway is formed by blasting, the front probe beam will be extended to the head-on rock wall in time, and the top and back will be connected tightly with wooden backboard, and hydraulic props will be laid according to the roof condition. Then use anchor rod, net and shed to support.
3.2 Support when the roof of goaf is higher than the roof of roadway
When the roof of goaf is higher than the roof of roadway, the roof should be supported, the steel shed should be erected directly with the front probe beam, and the steel mesh or steel formwork back plate should be laid. If the empty roof can't be loaded with bolts, it is necessary to tie and fix the steel mesh on the scaffold with iron wire. The roof caving area at the top is connected with a "well"-shaped wooden stake, and a grouting iron pipe is reserved. After the roadway passes through the goaf, it is filled and compacted by grouting. Grouting pipe buried one at the top every 2m until it passed through the mined-out area; For the mined-out areas on both sides of the roadway, flaky concrete is used to fill behind the steel mesh to form a natural slope, and then concrete is sprayed to form a flaky steel mesh concrete wall to ensure the stability and safety of the shaft.
3.3 Support when the goaf floor is lower than the roadway floor
When the goaf floor is lower than the roadway floor, it is very important to strengthen the floor support. Remove the floating gangue in the floor 500 ~ 800 mm vertically from the designed driving floor position, and then build the flaky concrete reinforced floor, with the concrete strength grade of C20. In order to prevent excessive water accumulation in the goaf from threatening the roadway water pressure in the future, when supporting the shaft wall, 2-inch steel pipes and gates are reserved as drainage pipes at the corresponding shaft wall position with the floor of the goaf 500mm high.
3.4 Special circumstances support plan
Large area suspended mined-out area. If the shaft penetrates into a large goaf, in order to prevent the sudden sinking of the roof during construction from causing a major roof accident, it is necessary to set up a wooden crib under the temporary support in advance for effective protection to prevent the roof of the working face from crushing the roadway support and causing an accident. After the initial support is completed, the top wall should be poured with concrete.
Construction of caving fracture zone. If the shaft penetrates into the mined-out caving zone or the surrounding rock fracture zone, the method of advance support, initial concrete spraying and short excavation and short support in front of the steel shed must be adopted. After the completion of the roadway, 30 ~ 50 mm thick concrete is sprayed at the initial stage, the surrounding rock is closed in time, and then the initial support is carried out. If the surrounding rock is seriously broken and caving, grouting can be used to reinforce the broken surrounding rock on the basis of advanced beam support. The roof and two sides in front of the roadway are reinforced, then excavation is carried out and grouting is carried out with cement slurry. Figs. 2 and 3 show the shaft support of the goaf part.
4 Other measures
In the shaft construction, according to the site conditions, on the basis of the original support, the roof is reinforced by reinforcing anchor cable. Entering the floor of 3# coal seam, the roof of roadway is coal seam, which is easy to fall after slag discharge. According to the site situation, the advanced pipe roof support method can be used to maintain the roof in advance. The advanced pipe shed is made of 1.2 inch steel pipe, with a length of 2500mm and an arch above the shaft shoulder of the advanced support. Steel pipe 10, pipe spacing of 300 ~ 400 mm, advanced pipe shed support can effectively prevent the leakage of roof gangue.
5 conclusion
It is a difficult point for inclined shaft to pass through goaf. Practice shows that according to the above measures, the auxiliary inclined shaft of Gulong Coal Industry can pass through the goaf of 3# coal seam safely and smoothly. From April to early May, 70 U-shaped steel sheds were built, with an excavation of 56 meters. During this period, there was no personal injury and roof fall accident, which accumulated valuable experience for the construction of inclined shaft crossing goaf in the future.
References:
[1] Cui Yunlong. Concise handbook of well construction engineering [M]. Beijing: Coal Industry Press, 2003.
Hou Chaojiong, Guo,, et al. Bolt support in coal roadway [M]. Xuzhou: China University of Mining and Technology Press, 1999.
About the author:
Chai Rui (1984-), male, undergraduate, assistant engineer, graduated from Taiyuan University of Technology in July 2005, majoring in mining engineering, and now works in the dispatching command center of Jinsheng Mining Investment Co., Ltd. for technical management.