Automatic measurement method of drilling-cuttings of boreholes in the coal seam and test study

Drilling-cutting method is a commonly used coal bump risk detection method in coal seams. The efficient and accurate acquisition of the quality of drilling-cuttings is a technical difficulty in engineering site, which could directly affect the risk detection efficiency and results. Based on the discharging characteristics of drilling-cuttings and the principle of fluid quality weighing, an automatic measuring device for drilling-cuttings suitable for different diameter boreholes is developed. This device consists of cuttings collecting unit, weighing unit, data processing system and fixing unit. It can measure the quality of the drilling-cuttings according to the flow-quality of drilling-cuttings discharged from the borehole and the calibration function. The measurement accuracy of this method is verified by laboratory test and field test. Research shows that the drilling process and drilling pipe installation process can be easily identified based on the drilling cuttings’ flow quality – time curve. The accumulated flow-quality of drilling-cuttings per meter has positive linear correlation with its actual quality, and the calibration function is related to the device measurement parameters, such as the dip angel of the weighing slideway and the sampling frequency. Compared with the conventional weighing method, when measuring the drilling-cuttings by using the automatic measurement device, the maximum measurement error of the laboratory test is less than 6.5%, and the average error of the field test is 5.13%, while the data with error less than 10% account for 86.91%. The device measure parameters and the engineering factors, such as drilling-cuttings flow velocity and particle size, have little effect on the measurement accuracy. In the construction of conventional-diameter drilling-cutting borehole, the drilling pipe installation process time is reduced by 25.16%, and the construction efficiency is increased by 11.84%. The distribution law of drilling-cuttings in the shallow part of the large-diameter destressing borehole is consistent with that of the conventional-diameter drilling-cutting borehole, and the distribution of drilling-cuttings in deeper roadway side can be obtained. The proposed automatic measurement method of drilling-cuttings can improve the construction operability of large-diameter drilling-cutting method, and can realize the synchronous operation of pressure relief and drilling-cuttings measurement.