Judgment technique for over-exploration of water-conducting channel based on process analysis and fuzzy comprehensive evaluation

The geological conditions of the North China-type coalfields are complicated, and a large number of water-conducting channels are formed by the tectonic cutting of the coal seam base plate, whose detection and identification have always been the key point and difficulty in water damage prevention and control. Based on the multi-branch directional long drilling overrun investigation, the water-conducting channel identification technology combining process analysis and fuzzy comprehensive evaluation was constructed. Firstly, in the process of overpassing exploration, six evaluation indexes were selected, named drilling time recording, drilling fluid consumption, γ recording, rock chip recording, water pressure test and injectability and the construction process was divided into 16 working conditions, according to which a comprehensive analysis flowchart was set up to make a qualitatively judgement on whether the sample points were water-conducting. Secondly, the six indicators are quantified and graded by drilling speed, drilling fluid consumption, γ value, non-tuff proportion, unit grouting volume, and grouting volume, the weights of the indicators were determined by using the over-weighting method, and a three-level quantitative identification was made based on the fuzzy theory and the maximum membership principle to determine whether the sample point was water-conducting. Lastly, the technique was used to carry out a comprehensive process analysis and fuzzy comprehensive evaluation of 13 points in the 15031 working face of Zhaogu No.1 mine, of which 10 points had a high probability of water conduction and 3 points had a low probability of water conduction. This technique constructed a system of indicators for identifying water-conducting channels, and carried out quantitative grading and comprehensive evaluation, which improved the identification of water-conducting channels in the coalbed base plate.