Experimental Study On Dynamic Characteristics Of Drilling And Multi-parameter Index Prediction Of Rockburst

Rockburst is a major dynamic disaster caused by the instability and destruction of coal and rock,which seriously affects the safe mining of coal mines.In order to effectively prevent and control it accurately,many scholars at home and abroad use the drilling cuttings method to predict and evaluate rockburst.The drilling cuttings method is a simple and easy method that uses the weight of drilling cuttings per meter to characterize the stress value of the coal,thereby predicting the risk of rockburst and evaluating the danger level.However,in the process of predicting and evaluating rockburst with the drilling cuttings method in mines,on the one hand,due to the incomplete collection of drilling cuttings and the single indicator of the weight of drilling cuttings,the test results are seriously affected.On the other hand,coal seam water injection is conducive to the testing of the weight of drilling cuttings,the last aspect is that during the drilling process using the drilling cuttings method,drilling dynamic phenomena such as pipe-sucking and pipe-sticking.Therefore,in view of the shortcomings of the above-mentioned drilling cuttings method and the dynamic phenomena of pipe-sucking and pipe-sticking,an experimental study of drilling dynamic characteristics and multi-index prediction of rockburst is carried out,aiming to improve the prediction and evaluation of the risk of rockburst reliability of grades.Exploring the danger of rockburst dynamic disaster and the new sensitive parameters of drilling multi-index,and proposing new methods and techniques for precise detection of deep coal and rock dynamic disaster danger zones.In this paper,based on the mechanical model and drilling cuttings production and removal model of coal breaking with drilling rig,the mechanism of pipe-sucking and pipe-sticking is revealed by analyzing the load characteristics and the dynamic relationship between the drilling cuttings production speed and removal speed.Qualitative analysis of the relationship between drilling multi-index and coal stress.Subsequently,the laboratory and field experiments were carried out by using the drilling multi-index test system independently developed by the research group to determine the influence law of coal stress and propulsion speed on the multi-index.With the help of the changing rules of drilling multi-index,the influence of relevant factors on the risk of pipe-sucking and pipe-sticking is studied.As a supplement to the research content of the drilling cuttings removal rule,combined with the experiment,the FEM-SPH coupled algorithm was used to simulate the drill pipe load characteristics and drilling cuttings removal performance of coal breaking.The analysis of the simulation results not only proves its reliability,but also obtains some useful conclusions.The results show that under certain conditions,the drilling cuttings production speed of thedrilling rig increases with the increase of the coal stress,while the drill pipe thrust and torque decrease and increase respectively with the increase of the coal stress.The torque of the drill pipe as an intermediate quantity indirectly affects the change of the rotation speed of the drill pipe,which changes inversely with the rotation speed of the drill pipe.Under certain conditions,the drilling cuttings production speed of the rig is positively related to the propulsion speed,the torque and thrust of the drill pipe are positively related to the propulsion speed of the rig,and the rotation speed of the drill pipe is negatively related to the propulsion speed of the rig.Combined with the theoretical analysis,the research results of the multi-index change law reflect the influence of relevant factors on the tendency of pipe-sucking and pipe-sticking.Under certain conditions,the thrust of the rig decreases with the increase of the coal stress.This downward trend indicates that pipe-sucking is taking place,and its decline increases with the increase of coal stress,the pipe-sucking phenomenon is more obvious.The coal stress environment and the rig's propulsion speed have a significant impact on the probability of pipe-sticking.With the increase of the coal stress and propulsion speed,the drilling cuttings production speed and drilling cuttings removal speed of the rig increase and decrease respectively,and the risk of pipe-sticking increases further.The above research results not only obtained the change law of the drilling indexes with the coal stress,but also confirmed the feasibility of the drilling multi-index prediction of rockburst initially.And the paper conducted a regression analysis on the field test data by Origin software to determine the critical value of the drilling index in construction area.Through the mechanism analysis and experimental research on the pipe-sucking and pipe-sticking phenomenon,it is found that the pipe-sucking phenomenon can not be eliminated from the drilling process alone.The pipe-sucking phenomenon is greatly affected by the stress environment,and the most fundamental way to eliminate this phenomenon is through pressure relief of drilling or coal seam water injection to reduce coal stress in construction area.For the pipe-sticking phenomenon,increasing the drilling cuttings removal speed of the drilling rig and reducing the drilling cuttings production speed of the drilling rig by selecting reasonable drilling parameters are very economical ways to avoid such dynamic phenomena.And the main principle is to select as low a propulsion speed as possible while ensuring construction efficiency.This thesis has 64 figures,17 tables and 60 references.