Abstract:
In an inclined layered solid-filling mining method in an ultrathick coal layer, tunnels and equipment are arranged according to a solid-filling mining method. An artificial roof for a lower layer is formed by metal meshes and bamboo fences of a first layer a solid-filling mining method. The method is repeated, until the entire ultrathick coal layer is finished. The method is repeated forming additional roofs for subsequent layers.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an inclined layered solid-filling mining method in ultra-thick coal layer, which is especially applicable to exploitation of ultra-thick coal layers under surface constructions, railroads, or water bodies. 
     BACKGROUND OF THE INVENTION 
     The resource of ultra-thick coal layers (8-20 m) under constructions, railroads, and water bodies is widely distributed in China, and these coal layers are important coal layers for improving exploitation efficiency and yield in coal mines in China. At present, there are mainly two types of exploitation methods for ultra-thick coal layers (8-20 m) under constructions, railroads, and water bodies in China: the first type includes layered mining, caving mining, and thickness-limit mining, etc., which utilizes a spontaneous caving approach to manage coal roofs, and have the following problems: spontaneous roof caving may cause surface subsidence and damages to surface constructions and railroads, etc., and may result in settlement of ground water level and damage to the ecologic environment; the second type includes strip mining, large area coordinated mining, reducing subsidence by grouting mining, etc., though these mining methods have some surface subsidence control effects and can ensure safe use of surface constructions and railroads, they have disadvantages such as low level of mechanization, low recovery ratio, high production cost, low production efficiency, small scale or partially in research. Hence, it is urgent to develop a coal mining method that can effectively control strata movement, ensure safe use of surface constructions and railroads, etc., and efficiently recover ultra-thick coal layers (8-20 m) under constructions, railroads, and water bodies. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     The object of the present invention is to provide an inclined layered solid-filling mining method for ultra-thick coal layers under surface constructions, railroads, or water bodies. 
     Technical Scheme 
     the inclined layered solid-filling mining method in ultra-thick coal layer disclosed in the present invention comprises the following steps:
         a. dividing an ultra-thick coal layer into inclined layers having thickness of 2.5˜4.5 m according to the thickness of the ultra-thick coal layer under surface construction, railroad, or water body, the structure of overlaying strata, and the protective rating of surface construction, determining the number of inclined layers, and adopting a layered mining downward filling order;   b. arranging tunnels and installing equipment according to a conventional solid-filling mining method, and mining a first working face in the first layer;   c. executing a first filling mining cycle conventionally, i.e., cutting the coal, advancing a scraper conveyer, advancing a filling mining hydraulic support, constructing an artificial roof on the bottom of the mine goaf sequentially, laying a metal mesh on the bottom of the mine goaf firstly, with the edge of the metal mesh arranged at 5 cm from the base of the filling mining hydraulic support, and then laying bamboo fences on the metal mesh, with the edge of the bamboo fences arranged at 5 cm from the edge of the metal mesh, and laying the metal mesh and bamboo fences along the direction parallel to the mining working face, till the bottom of the entire mine goaf is laid with the metal mesh and bamboo fences, then, after laying the metal mesh and bamboo fences, filling a solid material into the mine goaf and compacting the solid material with a rammer compactor, so as to complete the cycle in a first step length; continuing to execute a second filling mining cycle, i.e., under the cover of the filling mining hydraulic support, laying metal meshes and a bamboo fences on the bottom of the mine goaf and connecting the metal meshes and bamboo fences with the metal meshes and bamboo fences laid in the first filling mining cycle together respectively with iron wires, and then filling the mine goaf, so as to complete the cycle in a second step length; such a cycle is repeated, till the mining reaches to the protective coal pillars and thereby the filling mining of the first working face is completed;   d. moving the working face to the next working face in the first layer, and repeating step c, so as to carry out filling mining at all working faces in the first layer sequentially; meanwhile, 4 months after completing filing at the first mining working face in a first layer, carrying out mining filling for a second layer in the same way as that for the first layer at the corresponding position in the second layer, under the cover of the metal meshes, bamboo fences, and artificial roof, till the mining filling of all working faces in the second layer is completed;   e. repeating steps c and d, carrying out filling mining of the current layer under the cover of the artificial roof formed in the previous layer, till the mining filling of all layers in the entire ultra-thick coal layer is completed.       

     Benefits 
     The inclined layered solid-filling mining method in ultra-thick coal layer under a surface construction, railroad, or water body provided by the present invention has the following advantages: the mine goaf is filled with a solid material such as gangue, metal meshes and bamboo fences are laid and an artificial roof is constructed under the solid material, to provide cover for filling mining of the next layer; thus, on one hand, the surface subsidence problem is solved, and safe use of the surface construction is ensured; on the other hand, the coal recovery ratio is improved, the service life of the coal mine is prolonged, the resource of ultra-thick coal layers under surface constructions, railroads, and water bodies is released, and the resource recovery ratio of the coal mine is improved. The present invention solves the two major problems in the prior art: one is surface subsidence and damages to the surface construction or railroad, etc. which resulted from spontaneous caving of roof; and, the other one is low level of mechanization, low recovery ratio, high production cost, and low production efficiency, etc. Since a solid material such as gangue is used as the filling material in the present invention, the pollution of surface environment and the occupation of land are reduced, and strata movement and surface subsidence can be controlled effectively. The method is simple, with high production efficiency, low production cost and high practicability in the art. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of the layout of the first working face in the first layer according to the present invention; 
         FIG. 2  is a side view of the first layer when metal meshes are laid in mine goaf in the first cycle according to the present invention; 
         FIG. 3  is a side view of the first layer when solid materials are filled in a mine goaf in the first cycle according to the present invention; 
         FIG. 4  is a side view of the first layer when coal mining is carried out in the second cycle according to the present invention; 
         FIG. 5  is a side view of the first layer when metal meshes are laid in mine goaf in the second cycle according to the present invention; 
         FIG. 6  is a side view of the first layer when solid materials are filled in a mine goaf in the second cycle according to the present invention; 
         FIG. 7  is a side view of the first layer when the mining reaches to protective coal pillars; 
         FIG. 8  is a side view of the second layer when coal mining is carried out according to the present invention. 
     
    
    
     AMONG THE FIGURES 
       1 —coal mining machine,  2 —material transport gangway,  3 —self-advancing transfer conveyer,  4 —belt-type material conveyer,  5 —coal transport gangway,  6 —coal transfer conveyer,  7 —belt-type coal conveyer,  8 —crushing machine,  9 —coal mining working face,  10 —scraper conveyer,  11 —filling mining hydraulic support,  12 —bottom-dump conveyer,  13 —solid material,  14 —metal mesh,  15 —base,  16 —rammer compactor,  17 —protective coal pillar,  18 —mined goaf,  19 —filling working face,  20 —overlying strata,  21 —first layer,  22 —second layer,  23 —artificial roof,  24 —bamboo fences,  25 —floor. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereunder the present invention will be further described according to an embodiment, with reference to the accompanying drawings: 
     The inclined layered solid-filling mining method in ultra-thick coal layer disclosed in the present invention comprises the following steps:
         a. ultra-thick coal layer is divided into inclined layers having thickness of 2.5˜4.5 m according to the thickness of the ultra-thick coal layer under a surface construction, railroad, or water body, the structure of overlaying strata, and the protective rating of surface construction, the number of inclined layers is determined, and a layered mining downward filling order is adopted;   b. tunnels and equipment are arranged according, to the conventional solid-filling mining method, to form a filling mining system, i.e., drilling out a vertical material filling well at an appropriate ground location, and a solid filling material transport gangway that communicates with the main haulage gangway is dug in the bottom of the vertical material filling well; a belt belt-type material conveyer  4  is deployed in the material transport gangway  2 , a belt-type coal conveyer  7  is deployed in a coal transport gangway  5 ; a self-advancing transfer conveyer  3 , a crushing machine  8 , and a coal transfer conveyer  6  are deployed at the terminal of a coal mining working face  9 ; a filling mining hydraulic support  11 , a scraper conveyer  10 , and a coal mining machine  1  are deployed at the coal mining working face  9 ; a bottom-dump conveyer  12  and a rammer compactor  16  are deployed at a filling working face  19 ;   c. the first working face in a first layer  21  is mined first, i.e., cutting coal, pushing forward the scraper conveyer  10 , and pushing forward the filling mining hydraulic support  11  is performed sequentially according to conventional mining method, then, an artificial roof  23  is constructed in the bottom of a mine goaf  18 , i.e., a metal mesh  14  is laid on the bottom of the mine goaf  18  first, with the edge of the metal mesh  14  arranged at 5 cm from the base  15 , to prevent the metal mesh  14  from fully covered by the solid material  13 , then, a bamboo fence  24  is laid on the metal mesh  14 , with the edge of the bamboo sheath  24  lagged for 5 cm from the edge of the metal mesh  14 , to facilitate connection with the metal mesh  14 , and metal mesh  14  and bamboo fences  24  are laid along a direction parallel to the coal mining working face  9 , till the bottom of the entire mine goaf  18  is laid with metal mesh  14  and bamboo fences  24 , next, after laying the metal mesh and bamboo fences, the mine goaf  18  is filled with the solid material  13 , and the solid material  13  is compacted with the rammer compactor  16  to form a dense filling body, thus, a cycle in the first step length is completed; in the second cycle, mining is carried out in the same way as the first cycle, next, under the cover of the filling mining hydraulic support  11 , a metal mesh  14  and a bamboo fence  24  are laid on the bottom of the mine goaf  18 , and are connected to the metal mesh  14  and bamboo fence  24  laid in the first cycle together respectively with iron wires, then, filling is carried out in the same way as the first cycle, thus, the cycle in the second step length is completed; such a cycle work is repeated, till the mining reaches to the protective coal pillars  17 , the filling mining of the first working face is completed.   d. the working face is moved to the next working face in the current layer, other working faces are mined and filled sequentially according to the filling and mining method of the first working face, till all the mining filling work is done for the first layer  21 ; in addition, the mining and filling for a second layer  22  is carried out in the same way as that for the first layer at the corresponding position in the second layer  22 , under the cover of metal mesh  14 , bamboo fences  24 , and artificial roof  23 , at the time of 4 months after the first working face of the first layer  21  is filled and mined; in that way, the mining and filling of the current layer is carried out under the cover of the artificial roof prepared in the previous layer, till the mining of the entire ultra-thick coal layer between the overlying strata  20  and the floor  25  is completed.