CN117345242A - Method for efficiently caving suspended top coal at end head of fully mechanized caving face of ultra-thick coal bed - Google Patents
Method for efficiently caving suspended top coal at end head of fully mechanized caving face of ultra-thick coal bed Download PDFInfo
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Abstract
The invention discloses a method for efficiently caving a suspended top coal at the end of a fully-mechanized caving face of an extra-thick coal seam, which utilizes hydraulic coal breaking and caving to weaken the top coal at the end of the fully-mechanized caving face so as to accurately control the maximum suspension length of the suspended top coal at the end of the fully-mechanized caving face, firstly, modeling and numerical simulation are carried out according to basic mechanical parameter data, internal porosity data and fracture distribution data of coal bodies and surrounding rocks of the coal seam and goaf of the target fully-mechanized caving face, and then hydraulic coal breaking and caving operation is carried out on the site of the target fully-mechanized caving face of a mine after the optimal hydraulic coal breaking and caving coal weakening and caving top coal technical parameters meeting the requirements of the maximum suspension length of the top coal are obtained. The method is safe and reliable, has controllable cost and good weakening effect, can realize accurate control on the premise of effectively weakening the mechanical strength of the top coal and controlling the maximum suspension length of the top coal, and is particularly suitable for weakening and caving the top coal at the end head of the fully mechanized caving face of the super-thick coal seam.
Description
Technical Field
The invention relates to a method for caving suspended top coal, in particular to a method for efficiently caving suspended top coal at the end of a fully-mechanized caving face of an extra-thick coal seam, which utilizes a hydraulic coal breaking technology to weaken the mechanical strength of the suspended top coal at the end of the fully-mechanized caving face and obviously reduce the maximum suspension top length of the suspended top coal, and belongs to the technical field of coal mine safety exploitation.
Background
Caving coal mining is a coal mining process developed for thick and extra-thick coal seam mining. When the coal seam is mined by adopting a caving coal mining method, a coal mining working face with the mining height of 2-3 m is arranged along the bottom plate of the coal seam or the bottom of the coal seam within a certain thickness range, the mining is carried out in a comprehensive mechanized mode, and the caving coal is discharged from a coal discharging window behind or on the bracket by utilizing the action of mine pressure or assisted by loosening blasting and the like, and is conveyed out of the working face by a scraper conveyor. The caving coal mining method has a plurality of remarkable advantages, and is suitable for one-time full-height mining of coal beds with the thickness of 5-20 m, and coal which can be mined only by layering for multiple times in the original thick coal bed can be mined once. However, if the top coal above the coal face is hard, part of the top coal is difficult to collapse in time and form a suspended roof, when the suspended length of the top coal is large, a large amount of elastic energy is easily accumulated in the part of the top coal, if sudden fracture occurs under the disturbance of a stope, roof accidents can be possibly induced, and meanwhile, gas accumulation and air leakage in a goaf can be caused by the existence of the suspended top coal, so that gas disaster hidden danger and coal natural hidden danger are induced. Therefore, the suspended length of the top coal at the end of the top coal caving working face is not suitable to be too long, and the suspended top coal at the end of the working face needs to be promoted to collapse in time by technical means.
The conventional forced caving method for caving the suspended roof coal on the caving coal working face mainly shortens the suspension length required by the natural caving of the roof coal by weakening the suspension coal body in advance, and adopts the means of explosive blasting, hydraulic fracturing, carbon dioxide presplitting and the like generally, but has certain defects: the explosive blasting weakening effect is good, but the generated high energy release is easy to induce accidents such as gas explosion, coal dust nature and the like, so that the potential safety hazard is large, and the acquisition and storage of the explosive are difficult; the hydraulic fracturing is pollution-free and high in safety, but the fracturing effect in a coal seam is weak, the controllability of the crack propagation direction and length is poor, and accurate weakening is difficult to realize; the carbon dioxide presplitting technology is relatively new, the single fracturing cost is high, and the wide popularization is difficult at present.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the high-efficiency caving method for the suspended top coal at the end of the fully mechanized caving face of the super-thick coal seam, which has the characteristics of safety, reliability, controllable cost, good weakening effect and the like, can realize accurate control on the premise of effectively weakening the mechanical strength of the top coal and controlling the maximum suspension length of the top coal, and is particularly suitable for weakening caving treatment of the suspended top coal at the end of the fully mechanized caving face of the super-thick coal seam.
In order to achieve the purpose, the method for efficiently collapsing the suspended top coal at the end of the fully-mechanized caving face of the super-thick coal seam utilizes hydraulic coal breaking and caving to weaken the top coal at the end of the fully-mechanized caving face so as to achieve the purpose of precisely controlling the maximum suspended length of the suspended top coal at the end of the fully-mechanized caving face, and specifically comprises the following steps:
step1, acquiring mine data, and acquiring basic mechanical parameter data, internal porosity data and fracture distribution data of a coal body and surrounding rock of a target fully-mechanized caving face coal bed and a goaf thereof;
step2, constructing a loaded damage mathematical model of a coal rock layer of the mining of the target fully-mechanized caving face according to data of Step1, carrying out numerical simulation of the mining process of the target fully-mechanized caving face to obtain stress distribution and deformation characteristics of the target fully-mechanized caving face and a roadway, and periodically collapsing data of a roof and a roof coal, verifying and optimizing parameters of the numerical simulation model by using the periodically fractured collapse data of the roof and the roof coal of a mine site, the mining stress data of a coal bed and the deformation separation layer data of the roadway surrounding rock, so as to form a simulation model which accords with actual production conditions and monitoring data of the mine site; performing simulated hydraulic coal breaking and cave making on the working surface end head coal in the simulation model to obtain optimal hydraulic coal breaking and cave making weakening top coal technical parameters which can meet the maximum suspension length of the top coal and meet the target requirements;
the diameter size and depth size of the hydraulic coal-breaking cavity are as follows
L R cosθ+L 4 sinθ＜H 1
Wherein: l (L) R Is the diameter size of a hydraulic coal breaking cavity, L 4 Is the depth dimension H of the hydraulic coal breaking cavity along the front-back direction 1 The thickness dimension of the top coal above the roadway is the elevation angle of the drill rod;
step3, according to the optimal hydraulic coal-breaking cave-making weakening cave-making technical parameters obtained in Step2, drilling holes in suspended cave-making coal in the mine target fully-mechanized caving face site to the rear end of the end, impacting the broken coal body by utilizing high-pressure water jet ejected by a jet nozzle at the end of a drill rod and radially ejected along the drill rod, and forming a hydraulic coal-breaking cave in the suspended cave-making coal through rotation and rollback movement of the drill rod to complete one hydraulic coal-breaking cave-making operation;
the maximum suspension length of the weakened top coal is smaller than the target control length, and the relation between the maximum length size required by the suspension top coal to fracture and collapse and the weakened mechanical strength is satisfied
f 1 ＝ρ 1 gH 1
f 2 ＝ρ 2 gH 1
Wherein: r is R m Is the roof coal resistanceTensile strength, f 1 Is self gravity of direct roof, f 2 Is self gravity of top coal and ρ 1 Is the density, p of the directly topped material 2 The density and g of the material are the gravity acceleration of the top coal;
step4, continuously verifying and optimizing the numerical simulation model and the simulation model according to real-time monitoring data of the mine target fully mechanized caving face site along with continuous forward stepping promotion of the face and fracture and caving of the top coal after rear weakening, and correcting key parameters, and carrying out hydraulic coal breaking and cave making operation again on the mine target fully mechanized caving face site after fracture and caving of the top coal after rear weakening.
Further, when the Step2 is used for simulating hydraulic coal-breaking and cave-making by pushing coal at the end of the working face in the simulation model, the coal-breaking and cave-making is carried out by drilling from the vicinity of the junction of the suspended coal pushing and the top beam of the end supporting equipment of the working face, and the range of forward extension of the hydraulic coal-breaking cavity is not more than the junction of the suspended coal pushing and the top beam of the end supporting equipment of the working face.
Further, when the Step2 carries out simulated hydraulic coal breaking and cave making on the top coal of the end head of the working face in the simulation model, the internal staggering angle between the drill rod and the roadway space in front of the working face along the front-back direction is 0 degrees.
Further, when Step2 carries out simulated hydraulic coal breaking and cave making on the top coal of the working face end in the simulation model, the elevation angle theta of the drill rod meets the requirement of
θ＝arctan[(H 2 -H 3 )/L 1 ]
Wherein: h 2 For the height dimension of the roadway H 3 For the height dimension of the drilling machine, L 1 Is the distance between the drilling machine and the end of the working surface.
Further, in Step3, when the hydraulic coal breaking hole extends forward to the junction of the suspended top coal and the top beam of the working face end supporting equipment and the suspended top coal does not fall according to the expected, stopping the hydraulic coal breaking hole making operation, and adjusting the elevation angle theta of the drill rod of the drilling machine and the distance L between the drilling machine and the working face end according to the real-time monitoring data of the mine target fully-mechanized caving face site for weakened top coal 1 And repeating Step2 to resume the back of the working face endThe hydraulic coal breaking and cave making operation is carried out in the suspended top coal.
Further, after the stress distribution and deformation characteristics of the target fully-mechanized caving face and roadway and the period collapse data of the roof and roof coal are obtained in Step2, the initial position of the hydraulic coal-breaking cavity 10, the elevation angle theta of the drill rod and the diameter dimension L of the hydraulic coal-breaking cavity are obtained R Depth dimension L of hydraulic coal breaking cavity along front-rear direction 4 Height dimension H of drilling machine 3 Distance dimension L between drilling machine and working face end 1 Grouping numerical simulation is carried out on the equal parameters to obtain the suspended length L of the top coal of the end head of the working face under the condition of different hydraulic coal breaking cavity parameters 3 And (3) obtaining a main control factor to form a preferable coal breaking hole parameter range capable of meeting the requirement of the suspended length of the top coal.
Further, after the target fully-mechanized caving face and roadway stress distribution and deformation characteristics and the period caving data of the top plate and the top coal are obtained in Step2, grouping numerical simulation is carried out according to the setting conditions of the end support equipment of the working face on site, the stress change record data of the roadway support and the mine pressure display record data, and the optimal hydraulic coal breaking, cave-building and top coal weakening technical parameters which can meet the maximum hanging length of the top coal and meet the target requirements under the influence of coupling of different period pressure coming, support and stoping disturbance are determined.
Further, step1, when acquiring basic mechanical parameter data, internal porosity data and crack distribution data of coal bodies and surrounding rocks of a coal seam and a goaf of the target fully-mechanized caving face, selecting coal bodies and surrounding rock samples on site of the target fully-mechanized caving face and the goaf of the target fully-mechanized caving face underground a coal mine, carrying the samples to the ground, preparing standard samples in a laboratory, and testing and acquiring basic mechanical parameter data, internal porosity data and crack distribution data of the standard samples.
Compared with the prior art, the method for efficiently collapsing the suspended top coal at the end of the fully-mechanized caving face of the super-thick coal seam weakens the top coal at the end of the fully-mechanized caving face by utilizing hydraulic coal breaking and cave making so as to realize the accurate control of the maximum suspended length of the suspended top coal at the end of the fully-mechanized caving face, can obviously weaken the mechanical strength of the suspended top coal, greatly shorten the maximum length of the suspended top and has obvious effect; meanwhile, the construction flow of the method for efficiently caving the suspended top coal at the end of the fully mechanized caving face of the super-thick coal seam is relatively refined, the engineering quantity is small, the water jet coal breaking technology is relatively mature, and the construction difficulty is low; in addition, the method for efficiently caving the suspended top coal at the end of the fully-mechanized caving face of the ultra-thick coal seam can obviously reduce potential safety hazards such as easily induced end corner gas accumulation and air leakage, rock burst, gas disasters, spontaneous combustion of residual coal and the like in the production process of the face by controlling the length of the suspended top; in addition, the water jet coal breaking process can promote the initiation and expansion of cracks in the coal body, and water has a softening effect on the coal body, so that the breaking expansion degree of broken coal after breaking and collapsing can be further improved, and the top coal discharging rate and the overall coal mining rate are improved.
Drawings
FIG. 1 is a schematic diagram of the arrangement of the end equipment of the fully mechanized caving face and the hydraulic coal breaking and cave making operation;
FIG. 2 is a side view of FIG. 1;
fig. 3 is a top-down rotated view of fig. 1.
In the figure: 1. the coal seam is mined by the target, 2, the roadway space in front of the working face, 3, a high-pressure water pump, 4, a drilling machine, 5, a drill rod, 6, the end supporting equipment of the working face, 7, a jet nozzle, 8, a water jet, 9, the fully-mechanized caving working face space, 10, a hydraulic coal breaking cavity, 11, the end suspended overhead coal of the working face, 12 and the goaf behind the working face;
H 1 is the thickness dimension of the top coal above the roadway, H 2 For the height dimension of the roadway H 3 For the height dimension of the drilling machine, L 1 L is the distance between the drilling machine and the end of the working surface 2 The width dimension of the working surface along the front-back direction; l (L) 3 Is the suspended length dimension of the top coal along the front-back direction, L 4 Is the depth dimension of the hydraulic coal breaking cavity along the front-back direction, L 5 Is the upper width dimension of the roadway, L 6 Is the width dimension of the lower part of the roadway, L R The diameter size of the hydraulic coal breaking cavity is that of the drill rod, and theta is the elevation angle of the drill rod.
Detailed Description
The invention will be further described below with reference to the accompanying drawings by taking a coal mine comprehensive caving coal mining working face as an example.
The method for efficiently collapsing the suspended top coal at the end of the fully-mechanized caving face of the super-thick coal seam utilizes hydraulic coal breaking and cave making to weaken the top coal at the end of the fully-mechanized caving face so as to realize the accurate control of the maximum suspended length of the suspended top coal at the end of the fully-mechanized caving face, and specifically comprises the following steps:
step1, firstly acquiring mine data comprising geological conditions and mining conditions of a target fully-mechanized caving face coal bed, and basic mechanical parameter data, internal porosity data and crack distribution data of coal bodies and surrounding rocks of the target fully-mechanized caving face coal bed and goaf thereof:
the average burial depth of the coal mining working face of the comprehensive caving coal mine is 500m, the average coal seam inclination angle is 31 degrees, and the average coal seam thickness is 7m. And determining key data such as the arrangement mode, roadway support mode, coal mining parameters and the like of the target fully-mechanized caving face and the four-neighbor goaf according to the comprehensive histogram (including parameters such as thickness, lithology and the like) of the coal layer covered by the coal layer. Wherein the coal mining height of the target fully mechanized caving face is 2.7m, the coal caving height is 4.3m, and the thickness dimension H of the top coal above the roadway is the same 1 Height dimension H of roadway of 3.3m 2 3.7m, recovery speed of 3.2 m/day, upper width dimension L of roadway 5 4.4m, the lower width dimension L of the roadway 6 Width dimension L of the working face in front-rear direction is 5.4m 2 The working face end supporting equipment 6 adopts an end hydraulic support for supporting 6 m.
In order to accurately obtain basic mechanical parameter data, internal porosity data and crack distribution data of coal bodies and surrounding rocks of a coal seam and a goaf of the coal seam of the target fully-mechanized caving face, relatively complete large-size block samples such as coal bodies, gangue and rocks are selected on site of the target fully-mechanized caving face and the goaf of the coal seam to be carried to the ground, standard samples are prepared in a laboratory, and practical basic mechanical parameters such as compressive strength, tensile strength and poisson ratio of the standard samples are tested and obtained. The method comprises the following steps:
the underground selected block sample should be approximately cubic, and its volume is not less than 0.1m 3 Processing and preparing the block sample into cylinder standard with different standard sizes such as phi 50 multiplied by 100mm, phi 50 multiplied by 250mm and the like in a laboratoryAnd after the samples are grouped, testing and obtaining basic mechanical parameters of the standard samples by using an MTS triaxial loading tester, and respectively testing the porosity and crack distribution results inside the standard samples by using a mercury porosimeter and a rock CT machine.
The compression strength of the raw coal standard sample obtained after the test is 14.1MPa, the tensile strength is 1.0MPa, the Poisson ratio is 0.31, and the elastic modulus is 1.1GPa; the porosity of the raw coal standard sample is 7.8%, the average opening degree of the cracks is 90.1um, and the average volume of the cracks is 2.1 multiplied by 10 7 um 3 The fissure degree was 0.83%.
Step2, constructing a loaded damage mathematical model of a coal layer of the coal mining of the target fully-mechanized caving face on the basis of experimental acquisition of mechanical parameters of coal and rock according to geological conditions and mining conditions of the coal layer of the target fully-mechanized caving face, and carrying out numerical simulation on hydraulic fracture and cave-making of the top coal at the end head and caving of the top coal at the end head in the mining process of the working face to obtain preferable hydraulic fracture and cave-making weakening top coal technical parameters which can meet the maximum suspension length of the top coal and meet the target requirements:
firstly, constructing a loaded damage mathematical model of a coal mining stratum of a target fully-mechanized caving face by utilizing UDEC software, importing basic mechanical parameter data, internal porosity data and crack distribution data of coal bodies and surrounding rocks of a coal seam and a goaf of the target fully-mechanized caving face, including geological conditions and mining conditions of the coal seam of the target fully-mechanized caving face, into the model to perform numerical simulation of the mining process of the target fully-mechanized caving face, obtaining stress distribution and deformation characteristics of the target fully-mechanized caving face and a roadway, and roof coal period collapse data, and performing verification and parameter optimization on the numerical simulation model by utilizing the roof and roof coal period fracture collapse data, the coal seam mining stress data, the roadway surrounding rock deformation separation layer data and other data of a mine field, so as to optimize and form a simulation model which accords with actual production conditions and monitoring data of the mine field.
Secondly, carrying out simulated hydraulic coal breaking and cave making on the top coal of the working face end in the simulation model, analyzing the maximum length size required by the fracture and collapse of the suspended top coal in the forward pushing process of the working face, and changing the initial position of the hydraulic coal breaking cavity 10 and the elevation angle of a drill rodDiameter dimension L of theta and hydraulic coal breaking cavity R Depth dimension L of hydraulic coal breaking cavity along front-rear direction 4 Height dimension H of drilling machine 3 Distance dimension L between drilling machine and working face end 1 And analyzing the change rule of the maximum length of the suspended top of the end head of the working face by the equal parameters, analyzing the change rule of the maximum length of the suspended top coal of the end head under the coupling action of the support of the reinforced roadway, the periodical pressure change and the propulsion of the working face, and carrying out verification and model optimization by combining the on-site observation result of the mine.
When analyzing the maximum length size required by fracture and collapse of suspended top coal in the forward pushing process of a working face, applying a cover rock stress and self gravity to a simulation model, applying hydraulic force to the suspended part of the top coal to break the coal and make a cave, continuously increasing the suspended length of the top coal along with the continuous simulation of the forward pushing of the working face, continuously aggravating the damage of the suspended part of the top coal under the action of the cover rock stress and the self gravity until fracture and instability occur, and recording the suspended length L of the top coal at the end of the working face at the moment 3 Is provided for the maximum suspension length of the vehicle.
When the change rule of the maximum length of the cantilever roof at the end of the working face is analyzed, the initial position of the hydraulic coal-breaking cavity 10, the elevation angle theta of the drill rod and the diameter dimension L of the hydraulic coal-breaking cavity are different R Depth dimension L of hydraulic coal breaking cavity along front-rear direction 4 Height dimension H of drilling machine 3 Distance dimension L between drilling machine and working face end 1 Grouping numerical simulation is carried out on the same parameters to obtain the suspended length L of the top coal of the end head of the working face under the conditions of different sizes of hydraulic coal-breaking cavities 10 and different hydraulic coal-breaking cavity parameters 3 And (3) obtaining a main control factor to form a coal breaking cavity parameter range capable of meeting the requirement of the suspended length of the top coal.
When analyzing the support conditions of the reinforced roadway, the periodic pressure change and the change rule of the maximum length of the suspended top coal of the end under the action of the propulsion coupling of the working face, applying reinforced support data (such as the reinforced support data obtained after the measures of increasing the number of support anchor rods, increasing the support resistance of the support and the like) and additional periodic pressure data on the basis of a simulation model to carry out grouping numerical simulation to obtainThe suspension length L of the top coal of the end head of the working face under the conditions of different reinforced support data and additional period pressure data 3 And (3) forming a coal breaking cavity parameter range capable of meeting the requirement of the suspended length of the top coal.
In order to improve the coal breaking effect, the diameter size and depth size of the hydraulic coal breaking cavity 10 should be as follows: l (L) R cosθ+L 4 sinθ＜H 1 Wherein L is R Is the diameter size of a hydraulic coal breaking cavity, L 4 Is the depth dimension H of the hydraulic coal breaking cavity along the front-back direction 1 The thickness dimension of the top coal above the roadway is the elevation angle of the drill rod. In order to shorten the distance L between the drilling machine and the working surface end as far as possible 1 While avoiding contact with the face end supporting equipment 6 when the drill rod 5 drills into the target mining coal seam 1, the requirement of θ=arctan [ (H ] is satisfied 2 -H 3 )/L 1 ]Wherein θ is the elevation angle of the drill rod, L 1 For the distance between the drilling machine and the end head of the working surface, H 2 Is the height dimension of the roadway, H 3 Is the height dimension of the drilling machine.
The optimal technical parameters of weakening the top coal by hydraulic coal breaking and cave making of the mine field target fully-mechanized caving face are obtained by considering the dimensional factors of electromechanical equipment arrangement, roadway residual space, drilling machine 4, high-pressure water pump 3 and the like in the roadway space 2 in front of the working face and combining the mine field construction conditions. According to the simulation result, as shown in fig. 1 to 3, the drilling machine 4 is arranged at the middle position of the roadway space 2 in front of the working face along the left-right direction, and when the end of the working face is in the overhead coal suspension length L 3 Maximum allowable 4m, height dimension H of drilling machine 3 At 1.8m, the distance L between the drilling machine and the working surface end can be determined 1 8.7m, the inner error angle of the drill rod 5 and the roadway space 2 in front of the working face along the front-back direction is 0 degrees, the elevation angle theta of the drill rod is 12 degrees, and the diameter dimension L of the hydraulic coal breaking cavity is the same as the diameter dimension R At 3m, the initial position of the hydraulic coal-breaking cavity 10 and the drilling slant length of the drilling machine 4 are 17.6m, and the depth dimension L of the hydraulic coal-breaking cavity along the front-back direction 4 2.2m.
Step3, carrying out hydraulic coal breaking construction on a mine target fully mechanized caving face site according to the preferable technical parameters of weakening top coal by utilizing hydraulic coal breaking and hole making obtained in Step2, arranging hydraulic coal breaking equipment such as a high-pressure water pump 3, a drilling machine 4 and the like in a roadway space 2 in front of the face, suspending the top coal in the rear of the end to obliquely construct a drilling hole, conveying high-pressure water through a drill rod 5 by using the high-pressure water pump 3, radially spraying high-pressure water jet along the drill rod 5 through jet nozzles 7 (symmetrically arranged two) at the end part of the drill rod 5, breaking a coal body through the impact of the high-pressure water jet, forming a complete hydraulic coal breaking hole 10 which approximates a cylinder in the suspended top coal through the rotation and the rollback movement of the drill rod 5, and enabling broken coal particles and water to flow out from an annular space between the drill rod 5 and the drilling hole in a mixed state; after hydraulic coal breaking and hole making are completed, the hydraulic coal breaking equipment is removed, and one hydraulic coal breaking and hole making operation is completed.
With the continuous forward pushing of the working surface, the suspended length of the top coal is gradually increased, and the top coal breaks and collapses in advance under the action of the dead weight of the top coal and the pressure of the top plate. In order to effectively control the potential safety hazard of suspended roof, the maximum suspended length of the weakened roof coal is smaller than the target control length, and the relation between the maximum length size required by the suspended roof coal to fracture and collapse and the weakened mechanical strength is satisfied
f 1 ＝ρ 1 gH 1
f 2 ＝ρ 2 gH 1
Wherein: r is R m Is the tensile strength of the top coal, f 1 Is self gravity of direct roof, f 2 Is self gravity of top coal and ρ 1 Is the density, p of the directly topped material 2 The density of the top coal and g are gravity acceleration.
Taking the complexity of field conditions into consideration, combining numerical simulation and field application results, carrying out optimization adjustment on the technical parameters again, and determining the coal breaking technical parameters required by meeting the condition that the suspended top coal length is not more than the expected target length under the condition of conforming to the field actual conditions. The results show that when the distance between the drilling machine and the working face end is the dimension L 1 Diameter ruler for hydraulic coal breaking cavity with 9m and drill rod elevation angle theta of 12 DEGCun L R Depth dimension L of 3m of hydraulic coal breaking cavity along front-back direction 4 At 2.2m, the suspended length L of the overhead coal of the end head of the site working face 3 The average value is 3.2m, the maximum value is 3.8m, and the average value is lower than the target value by 4m, thereby meeting the technical requirement of weakening and efficient collapse of the suspended roof.
In order to ensure the coal breaking effect, at least the coal is drilled into and broken into holes from the vicinity of the junction of the suspended top coal and the top beam of the working face end supporting equipment 6; along with the gradual forward retraction of the drill rod 5, the range of the hydraulic coal breaking cavity 10 continuously extends forward, and the range of the hydraulic coal breaking cavity 10 extending forward cannot exceed the junction of the suspended top coal and the top beam of the working face end supporting equipment 6 so as to control the influence of the coal breaking cavity on surrounding rock supporting of the working face.
When the hydraulic coal breaking cavity 10 extends forwards to the junction of the suspended top coal and the top beam of the working face end supporting equipment 6 and the suspended top coal does not fall according to the expected span, the hydraulic coal breaking and cavity making operation should be stopped immediately, and the elevation angle theta of the drill rod of the drilling machine 4 and the distance L between the drilling machine and the working face end are adjusted 1 And (3) carrying out hydraulic coal breaking and cave making operation on the suspended top coal behind the end head of the working face again, and further weakening the mechanical strength of the top coal so that the suspended top coal collapses in time.
Step4, along with the continuous forward pushing of the working face, carrying out repeated hydraulic coal breaking and cave making operations on the mine target fully mechanized caving face from back to front in sequence, analyzing the influence of different schemes of different states and roadway support on the maximum suspension length of the top coal, optimizing the technological parameters of drilling construction and jet coal breaking, and forming the technical method suitable for the suspension top coal high-efficiency caving of the top coal caving face end under different use conditions. Specifically:
sequentially carrying out multiple hydraulic coal breaking and cave making operations on a mine target fully-mechanized caving face from back to front and carrying out real-time monitoring, continuously verifying and optimizing a numerical simulation model and a simulation model, and correcting key parameters; analyzing the elevation angle theta of the drill rod, the drilling position and the diameter dimension L of the hydraulic coal breaking cavity R Depth dimension L of hydraulic coal breaking cavity along front-rear direction 4 Suspended length L of coal at end of working face 3 Maximum length of (2)The optimal technical parameters of weakening top coal by hydraulic coal breaking and cave making on the mine site target fully mechanized caving face are obtained.
The supporting measures of the working face can be enhanced by means of increasing the number of anchor rod base anchor cables, increasing the initial supporting force of the support of the working face and the roadway; the change rule of the pressure is recorded and analyzed according to the stress change and the mine pressure display of the on-site working surface support and the roadway support; and analyzing the influence of the period pressure change and the supporting scheme change on the control of the hanging top of the end head of the working face, and determining the technical scheme of weakening the coal at the end head of the working face under the coupling influence of the pressure change, the supporting and the stoping disturbance of different periods.
The initial conditions such as the burial depth, the dip angle and the coal thickness of the coal bed, the mechanical strength of the coal rock mass, the arrangement of the working face and the roadway and the like can be changed and substituted into the corrected simulation model, so that the technical scheme and technological parameters of drilling construction and jet flow coal breaking which can effectively control the suspension roof length under different field geological conditions and coal mining conditions are researched; based on the hydraulic coal breaking method, the technical scheme of suspending top coal at the end of the top coal caving working face, which is suitable for different complex conditions, is formed by considering the construction quantity and the construction difficulty.
Claims (8)
1. The method is characterized in that hydraulic coal breaking and caving is utilized to weaken the top coal at the end of the fully-mechanized caving face so as to realize the accurate control of the maximum suspension length of the top coal at the end of the fully-mechanized caving face, and specifically comprises the following steps:
step1, acquiring mine data, and acquiring basic mechanical parameter data, internal porosity data and fracture distribution data of a coal body and surrounding rock of a target fully-mechanized caving face coal bed and a goaf thereof;
step2, constructing a loaded damage mathematical model of a coal rock layer of the mining of the target fully-mechanized caving face according to data of Step1, carrying out numerical simulation of the mining process of the target fully-mechanized caving face to obtain stress distribution and deformation characteristics of the target fully-mechanized caving face and a roadway, and periodically collapsing data of a roof and a roof coal, verifying and optimizing parameters of the numerical simulation model by using the periodically fractured collapse data of the roof and the roof coal of a mine site, the mining stress data of a coal bed and the deformation separation layer data of the roadway surrounding rock, so as to form a simulation model which accords with actual production conditions and monitoring data of the mine site; performing simulated hydraulic coal breaking and cave making on the working surface end head coal in the simulation model to obtain optimal hydraulic coal breaking and cave making weakening top coal technical parameters which can meet the maximum suspension length of the top coal and meet the target requirements;
the diameter size and depth size of the hydraulic coal breaking cavity (10) are as follows
L R cosθ+L 4 sinθ＜H 1
Wherein: l (L) R Is the diameter size of a hydraulic coal breaking cavity, L 4 Is the depth dimension H of the hydraulic coal breaking cavity along the front-back direction 1 The thickness dimension of the top coal above the roadway is the elevation angle of the drill rod;
step3, according to the optimized hydraulic coal-breaking, hole-making and weakening coal-pushing technical parameters obtained in Step2, drilling holes in suspended coal-pushing at the site of a mine target fully-mechanized caving face to the rear end, impacting broken coal bodies by utilizing high-pressure water jet ejected by a jet nozzle (7) at the end of a drill rod (5) and radially ejected along the drill rod (5), and forming hydraulic coal-breaking cavities (10) in the suspended coal-pushing through rotation and retreating movement of the drill rod (5) so as to finish one-time hydraulic coal-breaking and hole-making operation;
the maximum suspension length of the weakened top coal is smaller than the target control length, and the relation between the maximum length size required by the suspension top coal to fracture and collapse and the weakened mechanical strength is satisfied
f 1 ＝ρ 1 gH 1
f 2 ＝ρ 2 gH 1
Wherein: r is R m Is the tensile strength of the top coal, f 1 Is self gravity of direct roof, f 2 Is self gravity of top coal and ρ 1 Is the density, p of the directly topped material 2 The density and g of the material are the gravity acceleration of the top coal;
step4, continuously verifying and optimizing the numerical simulation model and the simulation model according to real-time monitoring data of the mine target fully mechanized caving face site along with continuous forward stepping promotion of the face and fracture and caving of the top coal after rear weakening, and correcting key parameters, and carrying out hydraulic coal breaking and cave making operation again on the mine target fully mechanized caving face site after fracture and caving of the top coal after rear weakening.
2. The method for efficiently caving the suspended top coal at the end of the fully-mechanized caving face of the super-thick coal seam according to claim 1, wherein when the Step2 is used for simulating hydraulic power coal breaking and caving by the top coal at the end of the working face in a simulation model, the hole is drilled and broken from the vicinity of the junction of the suspended top coal and the top beam of the end supporting equipment (6) of the working face, and the range of forward extension of the hydraulic power coal breaking hole (10) is not more than the junction of the suspended top coal and the top beam of the end supporting equipment (6) of the working face.
3. The method for efficiently caving the suspended top coal at the end of the fully mechanized caving face of the ultra-thick coal seam according to claim 2, wherein when Step2 carries out simulated hydraulic coal breaking and cave making on the top coal at the end of the face in a simulation model, the internal staggering angle between a drill rod (5) and a roadway space (2) in front of the face along the front-back direction is 0 degrees.
4. The method for efficiently caving the suspended top coal at the end of the fully mechanized caving face of the ultra-thick coal seam according to claim 2, wherein the elevation angle theta of the drill rod is satisfied when the simulated hydraulic coal breaking and hole making are carried out by the end top coal of the working face in the simulation model by Step2
θ＝arctan[(H 2 -H 3 )/L 1 ]
Wherein: h 2 For the height dimension of the roadway H 3 For the height dimension of the drilling machine, L 1 Is the distance between the drilling machine and the end of the working surface.
5. The method for efficiently caving the suspended top coal at the end of the fully mechanized caving face of the ultra-thick coal seam according to claim 1, wherein in Step3, when the hydraulic coal breaking cavity (10) is orientedStopping the hydraulic coal breaking and cave making operation when the suspended top coal does not fall according to the expected span after extending to the junction of the suspended top coal and the top beam of the working face end supporting equipment (6), and adjusting the elevation angle theta of a drill rod of a drilling machine (4) and the distance L between the drilling machine and the working face end according to real-time monitoring data of a mine target fully-mechanized caving working face site aiming at weakened top coal 1 And repeating Step2, and carrying out hydraulic coal breaking and cave making operation on suspended top coal behind the end of the working face.
6. The method for efficiently caving the suspended top coal at the end of the fully-mechanized caving face of the ultra-thick coal seam according to claim 1, wherein after the stress distribution and deformation characteristics of the target fully-mechanized caving face and the roadway and the periodic caving data of the top plate and the top coal are obtained in Step2, the initial position, the elevation angle theta of the drill rod and the diameter dimension L of the hydraulic caving hole (10) are determined by the method for the initial position, the elevation angle theta of the drill rod and the diameter dimension L of the hydraulic caving hole R Depth dimension L of hydraulic coal breaking cavity along front-rear direction 4 Height dimension H of drilling machine 3 Distance dimension L between drilling machine and working face end 1 Performing grouping numerical simulation to obtain the suspended length L of the head coal of the working face under different hydraulic coal breaking cavity parameter conditions 3 And (3) obtaining a main control factor to form a preferable coal breaking hole parameter range capable of meeting the requirement of the suspended length of the top coal.
7. The method for efficiently caving the suspended top coal at the end of the fully-mechanized caving face of the super-thick coal seam according to claim 1 is characterized in that after the target fully-mechanized caving face and roadway stress distribution, deformation characteristics and top plate and top coal period caving data are obtained in Step2, grouping numerical simulation is carried out according to the setting conditions of the end supporting equipment (6) of the on-site working face, the stress change recorded data of the roadway support and the mine pressure display recorded data, and the optimal hydraulic coal breaking and cave-making weakening top coal technical parameter range which can meet the maximum suspension length of the top coal meeting the target requirements under the influence of coupling of different period pressure, supporting and stoping disturbance is determined.
8. The method for efficiently caving the suspended top coal at the end of the fully-mechanized caving face of the ultra-thick coal seam according to claim 1, wherein when Step1 obtains basic mechanical parameter data, internal porosity data and crack distribution data of coal bodies and surrounding rocks of the coal seam and goaf thereof of the fully-mechanized caving face, coal body and surrounding rock samples are selected on site on the underground target fully-mechanized caving face of the coal mine and goaf thereof to be carried to the ground, standard samples are prepared in a laboratory, and basic mechanical parameter data, internal porosity data and crack distribution data of the standard samples are tested and obtained.
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