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Based on the advanced detection drilling rigs used in underground coal mines, a real-time method of obtaining the depth of drilling is proposed. Displacement sensors are used to measure the stroke of the drilling rig's feeding device during drilling, and an equation to calculate the depth of drilling is put forward. The same measurements are made by several sensors, improving measurement accuracy and reliability. The final drilling depth is obtained using a multi-sensor data fusion algorithm, combined with the calculation equation. The necessary derivation and calculation processes of the multi-sensor, adaptive weighted fusion algorithm are given. To optimize the integrated result, the weighting coefficients can be found through the algorithm corresponding to each sensor in an adaptive mode to optimize the fusion result. Three kinds of displacement sensors are installed on the feeding device of the drilling rig, and the drilling process is simulated in a laboratory test. The test proves that, compared with the mean method of three sensors, the data obtained by the multi-sensor and adaptive weighted fusion algorithm have the higher accuracy, and the sensor with the least variance in the fusion process has the most significant weighting coefficient. The drilling depth data that are obtained are more accurate than those obtained through the mean method with measurement data from a single sensor. The weighted coefficient of the measurement data is minimal when the measurement accuracy of the sensor suddenly deteriorates, so it has little effect on the measurement results. An experiment verifies this method's effectiveness and fault tolerance, showing an improvement in measurement accuracy. [ABSTRACT FROM AUTHOR]

This study establishes a prediction model based on the back propagation (BP) neural network for controlling the underground directional drilling path in a coal mine. The four-layer BP neural network model chooses 11 trajectory parameters (dip angles and azimuths from 12 m after the measurement while drilling (MWD)) and two control parameters as inputs. Two parameters, the dip angle and azimuth at bit, are the outputs. Trained with data from 502 groups, the model was used to forecast 12 test data groups. The results were then compared with the prediction results of artificial experience from 24 technicians. The study shows that the mean absolute error of the dip angle and azimuth at bit are only 0.51° and 0.68°, respectively, as predicted by the prediction model, which uses the logsig activation function and has a double-hidden-layer with a point structure of 9×6. The prediction error also follows a normal distribution. Compared with technicians who have worked for more than five years, the accuracy of prediction results from the BP neural network model is reduced by 33.9% and meets the needs of drilling path control. [ABSTRACT FROM AUTHOR]

Abstract: The underground nearly-horizontal directional drilling technology and equipments, which are firstly developed by Xi’an Research Institute of China Coal Technology & Engineering Group from 2005, are the most advanced in the industry of mining. The directional drilling equipment came into use in 2008, and up to now has obtained the good effect in China''s coalmine. Three hole-depth records of 1046m, 1059m and 1111.6m have been made continuously in underground in-seam directional drilling. In this paper, the technical contents, features and application of the directional drilling technology and equipments are introduced, the future work and trends are subsequently presented. [Copyright &y& Elsevier]

Abstract: The auger drilling technology and moderate pressure air drilling technology for soft coal seam in underground coal mine are introduced with their corresponding applications. According to the requirements of gas extraction borehole construction and the present status of drilling technology, the drilling problems and the developing trend of new drilling technology in soft coal seam are also discussed. Finally, some suggestions on borehole protection, pulverization dust control in borehole and directional drilling technology by air drilling motor are proposed. [Copyright &y& Elsevier]