Recognizing Method Of Coal Roadway Roof Strata Based On The Vibration Characteristics Of Bolter

As the mining depth continues to grow,coal mine roadway accidents have become increasingly prominent,one of the causing factors of roadway roof fall accidents is the cognition lack of geological strata structure.The roadway roof strata stability is not only determined by strata’s physical and mechanical properties,but much more important is that the combination relationship of roof strata and weak face sedimentary structure.Among which,the roof strata combination directly relates to roof fall types and supporting methods,while the weak face sedimentary structure will influence the rock continuity,especially the existence of all kinds of mud cementing sand layer,inter layer,interlaced bedding and the existence of a variety of tidal bedding,are all the risks of roof fall.Therefore,to figure out the roof strata combination is particularly important for roadway supporting and roadway stability.Based on these,taking the coal roadway roof strata’s characteristics and vibration analysis of drilling rigs as the main study line,to clarify the mechanical mechanism of vibration characteristics while drilling,that is to say rock strata with different mineral components,link structure,cement,particle size and other parameters have different vibration characteristics while drilling rock,thus to clarify that the kind of coal and rock has the same or similar mineral components,link structure,cement,particle size and so on,and it will also have similar physical and mechanical properties,there are similar drilling vibration characteristics when drilling these kinds of rocks.Based on this,theoretical analysis,equipment research and development,experiments and field test and other comprehensive study methods have been used,the method of recognizing coal roadway roof strata based on the vibration characteristics bolter has been systematically analyzed,besides,the aspects of stress,drilling track,characteristic recognition of vibration information in the drilling process have been deeply studied as well,and finally put forward the method of recognizing coal roadway roof strata based on the vibration characteristics bolter,the main process are listed as bellows.(1)By analyzing drill bit force,mineral components,link structure,cement,particle size and other parameters,to clarify the mechanical mechanism of vibration characteristics while drilling,that is to say the kind of rock strata has the same or similar mineral parameters and mechanical mechanism properties,there are similar drilling vibration characteristics when drilling these kinds of rocks.As it have different drilling bit force,thus to make a difference of vibration characteristics while drilling different rock,then to put forward the rock strata recognition method by analyzing drilling vibration characteristics.(2)By analyzing the two rock breaking movements during the process of drilling,one is the axial pushing movement which leads to rock core broken,the other one is spin rock breaking movement when cutting surrounding rock of rock core.These two movement work together,thus to form the holes of drilling rigs drilled along helical trajectories.On this basis,the forcing situation of drill bit while drilling has been analyzed as well,thus to get the drilling track equation of anchor hole.(1)While rock breaking,the drilling bit is influenced by axial drilling force,the resistance force and torque force.These forces work together,thus to form the total drilling force of drill bit,under which the drill bit drills coal and rock.(2)Combing the track under axial pushing movement with the track under spin rock breaking movement,thus to form the drilling trajectory of the drilling rig drilling along the spiral trajectory,and its equation is that:(3)By analyzing the mechanism of longitudinal vibration,lateral vibration and torsional vibration and the general spreading laws of longitudinal vibration wave,lateral vibration wave and torsional vibration wave in the process of drilling,based on vibration test principle,combining with coal mine real situation and mechanical structures characteristics of bolt drilling rigs,the roof fall risk detector for identifying different rock strata drilling characteristics has been designed and researched,it can be used to collect the torsion,longitudinal and lateral vibration information,according to these three kinds of information,roof strata could be recognized.From the aspects of vibration sensor selection and installation,shell structure design and data acquisition and pretreatment system,the design concept and method of roof fall risk detector have been clarified.(1)The roof fall risk detector has obeyed the design principles of safety,water proof,easy to use on structure design,according to vibration characteristics of bolters and test principle of vibration information,proper vibration sensor and its installation position have been chosen.Besides,owning to the central installation position of sensor on drilling and drill pipe joints,thus symmetrical structure has been designed,all the indicator light and explosion-proof shell are water proof.Meanwhile,in order to make install easier,special joints between roof fall risk detector and anchor drill and drill pipe have been designed.(2)The roof fall risk detector has been independently designed and developed according to intrinsically safe standard,and DXP2004 has been applied to circuit design,softwave design uses C language,PC software using Delphi development,all the chips are low power chips,filtering,amplification,analog conversion and so on have been accomplished by combining ADS1248 and LTC1569,STM32F103C8T6 has been used for data collection,and to restore the collected data to the W25Q128 lateral store chip,and to communicate with the host computer through the STM32F103C8T6 chip comes with USB communication interface.(3)Combined with the circuit design and data processing,the drilling vibration signal was analysed.It elemitated the noise and interference of vibration signal in the process of acquisition and storage,effectively removes the noise and interference in the sample data,the drilling time,standard deviation.It achieved good results in extracting the vibration characteristic parameters,such as amplitude range,vibration amplitude and so on.(4)By using the researched and designed roof fall risk detector based on vibration test,laboratory drilling tests have been designed,two materials with obvious difference on mineral composition,particle size,cement,cemented structure,shear resistance and other parameters have been studied.The results show that the three-axis acceleration has a big difference under the two kinds of materials if the drill pipe structure and drilling parameters keep the same.Thus we can see that the measure method based on drilling vibration information can be well used for recognizing medias with big different rock and physical parameters.(5)Based on the laboratory tests,it is found that there are synchronization in the transverse,twist and longitudinal three axial acceleration instantaneous values of the drilling rig.When drilling different rock strata,the longitudinal acceleration amplitude is much bigger,transverse and twist acceleration amplitude are relatively lower.On this study basis,the research method of vibration information characteristics referenced by transverse and twist acceleration based on longitudinal acceleration has been put forwarded.(6)Based on laboratory test results,the roof fall risk detector will be used in field test of Dong Pang mine based on drilling vibration information,and the field test results show that the method of recognizing coal roadway roof rock strata based on drilling vibration information can be effectively identify roof rock strata,and the effect is quite well.It realizes the synchronization with the bolt support,and saves a lot of manpower and material resources for the roof strata structure detection.