Research On Faster Prediction Technology Of Outburst Risk When A Cross-Cut Or Shaft Is Uncovered Under Complicated Geological Conditions

The paper analyzes several present coal outburst hazard prediction methods when uncovering coal in crosscut and shaft, and finds some problems existing in the normal predict methods including single indicator prediction and multi-indicator prediction, such as poor generality and relativity, low accuracy and so on. What is more severe are the underlying problems, resource wasting and even the accidents. In addition, the long time consumed for prediction methods and the influence from the complicate geology also affect the prediction. To solve these problems, based on the mechanism of loss of spherical shell stability, the author analyzes the influence factors to the uncovering coal in crosscut and shaft and sets up the prediction model, then gets the prediction indicators for the outburst hazard prediction.loss of spherical shell stability think that the expansion energy in initial released gas is the single energy resource to the coal outburst, so that it could be adopted as the prediction indicator. Professor Jiangchenglin employ the Fisher distinguish analysis method to analyze the results of 46 sets of simulation data, and prove that adopting the expansion energy in initial released gas and the thick of soft coal seam as the outburst prediction indicators to predict the outburst risk, the accuracy rate can be 100%; if the expansion energy in initial released gas adopted as the only indicator, the accuracy rate of prediction can from 90.9% to 96.7%,in case the outburst happen at that time, the critical indicator value is 42.98 mJ/g and 103.8 mJ/g. The paper set up the ideal outburst prediction model when uncovering coal in crosscut and shaft. The paper analyzes influencing factor of outburst under ideal model and thinks it can be used in outburst prediction when uncovering coal in crosscut and shaft.To the indicator mentioned, the author exposits the determination method of the expansion energy in initial released gas in detail, and finds out that the determination process is mainly affected by the gas pressure and crash situation of the coalbody, and the expansion energy in initial released gas is in direct ratio with the gas pressure. to sum up, the main outburst prediction indicator which is applyed practically is the measured gas pressure on the spot.the author find out that the human factor is the key point to realize the rapid and accurate measurement of the gas pressure. According to the numerical computation and experiments on the spot, the author get the expand law of spherical direction and radial direction flow field over time, and the method of radial direction flow is obviously better than the method of radial direction flow when using the rapid gas pressure measurements. The balance time of the former is no more than 10% of the latter, and with the advance of gas drainage time, the advantage becomes more and more obvious. According to the results of the numerical computation and experiments, when the method of radial direction flow is adopted, no matter what is the value of gas permeability coefficient, the maximum influence of emptying time to the balance time appears in 30 min, and the maximum value could be from 52% to 56%. To be concluded, using the method of radial direction flow to measure the gas press and accomplishing the drill sealing process in 30 min so as to rapid predict the gas outburst hazard is feasible.According to the detailed study on the rapid gas pressure measurement under complicate geology condition, borehole water sealing measurement has been put forward. Coalmine and lab experiment prove that gas pressure under gas and water co-exist can be determined by platform on the gas curve while water flux is small.Applying the rapid gas pressure measurement technology under complicated geological conditions and energy of initial releasing indicator to predict outburst risk of uncovering coal in crosscut and shaft more than 10 times. All the results are in accordance with the real situations, the accuracy of the new prediction method reaches 100%. The new prediction indicator avoid the disadvantages of predicted indicators recommended in Coal and gas outburst prevention and control rules. The theory gives the minim emission rate in order to make coal seam lose outburst risk with emission drill, decrease the emission time of drainage drill and achieve the rapidly safe tunneling process when uncovering coal in crosscut and shaft.