Evaluation system for floor water inrush risk in grout-reinforced working faces based on grouting boreholes dataset

To explore the mechanism of floor water inrush and evaluation methods for grouting effect in grout-reinforced working faces,an evaluation system for floor water inrush risks was established based on the dataset of 3 types of engi- neering information drawn from 2 245 grouting boreholes in 13 working faces of 5 large-scale coal mines in the Jiaozuo mining area,China. Through the case studies of water inrush accidents and data analysis for past water inrush points, the evaluation system considered several key factors including geological structures,hydraulic pressure of underlying aquifers,floor water-conducting properties,and grouting amounts. Based on the changes of borehole data and hydrogeo- logical characteristics in the floor recorded during the grouting process,it was concluded that floor water inrush in grout-reinforced working faces was mainly related to grouting conditions and grouting effects,assuming that mining-in- duced influences were the same. Four effecting factors related to grouting conditions included the dangerous zone of water inrush,water sources along strike,floor water-conducting properties in working faces,and floor water-conducting properties in severely dangerous zones,and three effecting factors related to grouting effects included differences in grouting amount between normal and fault zones,relationship of water pressure and cumulative grouting amount over time,and sequential variations of water pressure,water inflow,and grouting amount. Criteria of classification and effect evaluation for each factor were developed,and eight kinds of analytic legends were concluded. By comparing the differ- ences of each factor between water inrush and safe mining cases,the seven factors were categorized into significant fac- tors,moderate factors,and implicit factors. Finally,a risk evaluation method based on water pressure,water volume, and grouting amount (referred to as three-parameters) was proposed. The study presented a novel method and provid- ed academic support to the risk analysis of floor water inrush and grouting effect evaluation in grout-reinforced working faces.