Theory And Application Of Rock Mass Quality Evaluation Based On Response Characteristics Of Drilling Rig

Coal mine safety production is one of the main factors restricting coal’s productivity.Although the situation of coal mine production safety has been improved greatly in recent years,accidents like roadway roof caving,pressure bump and gas outburst occurred frequently,which threaten the coal mine safety production.The lack of understanding of geological conditions is the main bottleneck to prevent and handle the above accidents.Therefore,the correct evaluation of rock mass mechanical properties and quantitative characterization of rock mass quality are the premises of coal mine safety production.However,the existing evaluation methods of rock mass mechanical properties and quality mainly adopt the methods of drilling core and manual cataloguing,which are time-consuming and laborious,and difficult to be widely applied in the field.Therefore,it is necessary to seek a new quantitative characterization method of rock mass quality and obtain rock mechanical parameters quickly and efficiently to guarantee the safety and efficient production of coal mines.During drilling operation,the running parameters of drilling rig are correlated with the mechanical parameters of rock and the structural characteristics of rock mass,which provides a new way for the quantitative evaluation of rock mass mechanical properties and rock mass quality.It is the key to realize the quantitative evaluation of rock mass quality that how to obtain the response characteristics of drilling rig and rock mass quickly in real time and establish the prediction and evaluation model of rock mass quality.In this dissertation,the rock mass quality evaluation based on the response characteristics of drilling rig were comprehensively investigated using the methods of laboratory test,theoretical analysis and field practice.The main research results are as follows:(1)The drilling test platform was developed independently,and the response characteristics of drilling rig during rock breaking were revealed.Based on the theory of dimensional analysis,the drillability index(I_d)of rock was proposed.The correlation mathematical model between I_d value and UCS was established,and the in-situ quantitative prediction of UCS was realized using measurement while drilling.The results show that drilling rock breaking is a process of multi-parameter linkage.Torque is the main factor affecting the efficiency of drilling rock breaking,followed by rotational speed,and feeding pressure has the least effect.The accuracy of I_d value and UCS prediction model was verified by experiments,and the average difference rate between UCS experimental value and predicted value was only 5.71%.(2)A three-way vibration equation of drill pipe was established to reveal the vibration signal characteristics of drill pipe during drilling,and a vibration measurement device while drilling was designed.A method was proposed to distinguish the rock interface based on the amplitude change of the longitudinal acceleration signal of drill pipe,and to distinguish the structural or weak plane of rock mass based on the signal spectral characteristics.The feasibility of the identification method was verified by field vibration measurement test.The results show that lateral and torsional vibration signals cannot be used as indicators to identify the strata interface due to the interference of redundant signals,while the amplitude variation of longitudinal vibration signal can be used to distinguish the change of strata interface.Different from the signals of blasting vibration and rockburst,the vibration signal of drilling rig has no main frequency.But the vibration energy distribution characteristics of different rock mass in different frequency bands are completely different after wavelet packet decomposition and spectral analysis,which can be used for the identification of rock structure characteristics.(3)The correlation mathematical model between rock mass integrity coefficient(Kv)and rock mass quality designation(RQD)was established.And a classification method of rock mass basic quality(BQ)was proposed considering the UCS and RQD,which overcomes the difficulty in obtaining parameters of BQ rock mass quality classification.After that,a prediction method of rock mass quality using drilling parameters and vibration signals while drilling was proposed based on optimized neural network model.The results show that the difference between the calculated Kv using RQD and the measured value is small,which can improve the accuracy of BQ rock mass quality classification method.Compared with CA-ANN model and traditional ANN neural network model,the optimized ICA-ANN neural network model has higher prediction accuracy in predicting rock mass quality classification.(4)A comprehensive prediction and evaluation system of rock mass quality based on drilling parameters and drill pipe vibration signals was established,and it has been successfully applied in the field evaluation of coal seam thickness and in-situ identification of surrounding rock structure characteristics.Field tests were carried out in Yangliu Coal Mine,and the results show that the comprehensive rock mass prediction and evaluation system based on drilling parameters and vibration signals measured while drilling is effective in predicting the thickness of coal seam and the structure distribution characteristics of roadway surrounding rock.There are 84 figures,38 tables,and 181 references.